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Proceedings Volume 7658

5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optoelectronic Materials and Devices for Detector, Imager, Display, and Energy Conversion Technology

Yadong Jiang, Bernard Kippelen, Junsheng Yu
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Proceedings Volume 7658

5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optoelectronic Materials and Devices for Detector, Imager, Display, and Energy Conversion Technology

Yadong Jiang, Bernard Kippelen, Junsheng Yu
View the digital version of this volume at SPIE Digital Libarary.

Volume Details

Date Published: 21 October 2010
Contents: 5 Sessions, 216 Papers, 0 Presentations
Conference: 5th International Symposium on Advanced Optical Manufacturing and Testing Technologies 2010
Volume Number: 7658

Table of Contents

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Table of Contents

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  • Front Matter: Volume 7658
  • 5-1
  • 5-2
  • 5-3
  • Poster Session
Front Matter: Volume 7658
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Front Matter: Volume 7658
This PDF file contains the front matter associated with SPIE Proceedings Volume 7658, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.
5-1
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Dependence of silicon thin-film growth characteristics on substrate temperature
Longzhi Lin, Haojie Zhang, Shaoji Jiang
Silicon thin-films are fabricated on quartz substrates in the substrate temperature range 500~600 °C by electron-beam evaporation (EBE). Scanning Electron Microscopy (SEM) is employed to characterize the surface morphology of the films and measure the grain size. It is found that, there is an optimum temperature for getting large grain size. The X-ray diffraction (XRD) results show that the preferred crystallographic orientation on quartz wafer is (111). Raman spectra demonstrate the crystallization condition of the films and the crystalline volume fraction are calculated. The results indicate that the growth characteristics of the films depend significantly on the substrate temperature. Silicon thin-films are observed to be amorphous under the temperature of 560 °; above this temperature, they are polycrystalline. In other words, 560 °C is the critical temperature of the films transforming from amorphous silicon to poly-Si. The optimum temperature at about 580 ° for the growth of the film on quartz substrates is obtained. The films exhibit the largest grain size, highest value of crystalline volume fraction and the best structural quality when the substrate is kept at this temperature.
Assess image blur in photoelectric imaging system
Xiaofu Xie, Jin Zhou, Qinzhang Wu
The difficulty for no-reference image quality assessment is the lack of the information of the reference image. With the analysis of the mathematical model of the photoelectric imaging system and the reason for image blur, a method is proposed for constructing reference images, and at the same time the Structural Similarity index is introduced into noreference image quality assessment. A novel no-reference image quality assessment index called No-Reference Structural Sharpness is then proposed for quality evaluation of blurred images. This method constructs a reference image by a low-pass filter, and assesses the image quality by computing the structural similarity index between the original image and the reference one, thus considering the mathematical model of imaging system as well as the advantages of Structural Similarity index. The experimental results show that the new index is well in accordance with quality assessment results of both subjective evaluation and full-reference methods.
Photoluminescence and photovoltaic performance of poly3-octylthiophene and poly3-alkylthiophene
Lingliang Li, Fujun Zhang, Changrong Guan, et al.
Photoluminescence (PL) and photovoltaic (PV) performance of poly3-octylthiophene (P3OT) and poly3-alkylthiophene (P3DT) were studied in detailed. The two kinds of polymer can exhibit strong deep red emission peaking at 688 nm for P3OT and 675 nm for P3DT under blue light excitation, the effective excitation wavelength is about 462 nm. The dynamic process of exciton induced by light excitation strongly determined the PL and PV characteristics. From the PL excitation spectra of P3OT and P3DT, it can be seen that there are wide and intense excitation wavelengths in the visible light range. Two kinds of polymer solar cells based on P3OT or P3DT doping with PCBM were fabricated and the characteristics of OPVs were measured, the short current density (Jsc) and open circuit voltage (Voc) are 0.84 mA/cm2, 0.95 mA/cm2 and 180 mV, 270 mV, respectively.
Research progress on optical wireless communication at Xi'an University of Technology
Xizheng Ke, Lihong Yang
Optical Wireless Communication (OWC) adopts laser beam as the carrier to deliver the message. It combines with the advantages of Microwave Communication and Fiber Optic Communication. The key technologies of OWC system includes source coding, channel coding, laser diode modulation, auto-alignment and channel. In this paper, the research progress on OWC in Xi'an University of Technology is introduced. The research on source coding involves in baseband modulation, frequency modulation, OFDM transmission and vertical layered space-time codes. The research on channel coding includes RS codes, Turbo codes, LDPC codes and so on. And the adaptive coding method is analyzed to meet the different channel characteristics. Propagation performance of laser is studied and bit error rate (BER) is measured under various weather conditions of rainy days, snowy days, foggy days, hazy days and so on. The experiment results show that applying channel coding methods can improve the system performance of OWC, especially under rainy, snowy, foggy weather conditions, the BER after decoding is up to 10-6. Based on many years of research, the technologies of MIMO, OFDM and space-time coding are proved to be the key technologies that need to solve in OWC.
Energy transfer from both triplet and singlet energy levels of PVK to DCM2 induced by heavy-ion
Jiaxiu Luo, Lixin Xiao, Zhijian Chen, et al.
The energy band of red light-emitting materials is usually very narrow, which easily results in non-radiative recombination of excited states. There also exists concentration quenching effect due to strong π-π interaction. To avoid this, host-guest doping system is mostly used. On the other hand, the ratio of singlet and triplet excited state caused by recombination is 1:3. In comparison with the fluorescence (singlet to singlet), phosphorescence (triplet to singlet, but spin-forbidden) is much weaker, and the quantum yield is much lower. To enhance it and make full use of triplet excited state energy, heavy atom effect is commonly used to induce strong spin-orbital coupling leading to mix of singlet and triplet and release the forbidden triplet energy. Based on this, we fabricated polymer light-emitting diodes adopting polyvinylcarbazole (PVK) as the host and a red fluorescent dye, 2-{2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-pyrido[ 3,2,1-ij]quinolin-9-yl)-vinyl]-pyran-4-ylidene}-alononitrile (DCM2), as the dopant, and materials containing heavy-ion, kalium idode (KI) and bromo-carbazole, as energy transfer bridge to obtain complete energy transfer from excited states of both singlet and triplet energy level of PVK to ground state of singlet of DCM2. We found the current density of devices with heavy-ion materials were higher than device without it, and the weak blue emission from PVK host, existing in device of PVK:DCM2 device, can not be observed in electroluminescence spectra of device with heavy-ion materials, which indicates a complete energy transfer from both triplet and singlet energy levels.
SAW ethanol gas sensors based on cryptophane-A sensitive film
Ping Sun, Yadong Jiang, Guangzhong Xie, et al.
Surface acoustic wave (SAW) devices have been widely used for various chemical sensing applications because the sensor signal can be detected by simple and inexpensive electronics. The interactions between target analyte and the sensor surface cause changes in the mechanical, electrical, dielectric properties of the sensing coating deposited onto acoustic transducer. The changes in these properties will lead to changes in the velocity and amplitude of wave modes, which can be measured by frequency and insertion loss (IL) changes when the acoustic element is realized as a delay line or resonator. Among the different sensing coatings, the supermolecules are of considerable interest because the host molecules can be thought as original receptors allowing a specific recognition of guest molecules based on "key-lock" system. In this paper, SAW ethanol gas sensors that utilize the supermolecule of cryptophane-A as sensitive layer have been studied. We synthesized cryptophane-A from vanillyl alcohol using a double trimerisation method and deposited it on the SAW devices to fabricate cryptophane-A based SAW gas sensors. The SAW frequency and insertion loss (IL) were measured using a network analyzer. The frequency shift as the response of the cryptophane-A based SAW sensors to different concentration ethanol was measured at room temperature. It is found that the cryptophane-A based SAW sensor has high sensitivity and good reproductivity to ethanol. The frequency response increased linearly with the concentration of the ethanol.
Realization of p-type conductivity in ZnO by (N, Ag) dual acceptor codoping: a first-principles study
Ag monodoped, N monodoped and (nN, Ag) codoped ZnO have been investigated by the first-principles calculations, where the formation energies and ionization energies of various complexes and the electronic structure for 3N-Ag complex are studied. The calculated results are that N prefers to substitute O site, and Ag substitutes Zn site under the most growth condition, which indicate NO and AgZn all act as acceptors. Meanwhile, it's shown that N-Ag, 2N-Ag complex contribute little to p-type conduction because of the relatively higher ionization energy. However, 3N-Ag complex may have the lowest ionization energy among various complexes, while the formation energy of 3N-Ag is lower than that of N monodoped, Ag monodoped, N-Ag and 2N-Ag complex under the Zn-rich condition, which indicates that 3N-Ag complex is energetically favorable for the formation of p-type ZnO. Furthermore, by studying the electronic structure of 3N-Ag complex, it may generate an additional impurity band above the valence band maximum of ZnO. It is found that NO generated holes around the top of the valence band, and at the same time, N 2p states hybridized with 4d states of AgZn at the Fermi energy, and the hybridization lowered the repulsive interaction between the two dual acceptors, which enhance the concentration of impurities and the stability of the system, indicating that the dual acceptors evidently improve p-type conductivity of ZnO. Thus, it is found that 3N-Ag complex is the better dopant configuration. That can gain a better quality p-type ZnO under the Zn-rich condition. Our theoretical results are consistent with the experiment results.
Electrical and optical properties of amorphous vanadium oxide thin films deposited by DC magnetron sputtering
Zhenfei Luo, Zhiming Wu, Mingjun Du, et al.
In this work, vanadium oxide thin films were grown on glass slides by using reactive direct current (DC) magnetron sputtering from a vanadium target in an Ar+O2 atmosphere. It was found that the surface morphology, electrical and optical properties were strongly affected by the deposition temperature. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the structure and surface morphology of the samples. The structures of these films showed amorphous nature according to the XRD patterns showing no sharp diffraction peak. Measurements of SEM indicated the smooth surface of film deposited at low deposition temperature and rough surface at relatively high deposition temperature. In addition, these surfaces showed no obvious crystalline morphologies, which supported the XRD results. Electrical measurement indicated that the square resistances of films showed an exponential increase from 33 kΩ/square to 46 MΩ/square as the deposition temperature decreased from 320 to 160 °C, and that the square resistancetemperature curves of films exhibited typical semiconducting behavior. The investigation of optical properties of films in near-infrared range indicated that transmittance varied from about 95 % to 55 % when the deposition temperature elevated. In the ultraviolet-visible range, optical transmission measurements revealed that films showed distinguished transmission spectra when they were grown at different deposition temperatures. In the range of 300 to 400 nm, a transmittance shoulder was observed in the spectra, and this shoulder enhanced when the deposition temperature increased. On the other hand, a transmission enhancement at 530 nm disappeared after the deposition temperature exceeded 240 °C.
Optimizing the growth condition of optoelectronic material (ZnO film) by imaging technology
Jun Wang, Shi Pan, Yi Zhang
Using reactive radio-frequency magnetron sputtering technique, ZnO films are grown on Si (111) substrates with ZnO buffer layers deposited under different temperature with optimal condition of working pressure, sputtering power, flux of gas and sputtering time. In order to study the influence of ZnO buffer depositing temperature on the characteristic of the ZnO film, atomic force microscope, X ray diffraction, Raman spectroscopy and photoluminescence spectrum are used to analyze the morphology, growth orientation, Raman spectrum and optical properties of the ZnO films. It is concluded that the optimal depositing temperature of the ZnO buffer for the growth of the top ZnO film is 350 °C.
Effect of variable substrate temperature for SrTiO3 thin films using pulsed laser deposition
Xiaojing Wan, Li Wang, Xueqiong Su, et al.
In this paper, the high temperature solid state reaction method was applied to the preparation of SrTiO3 ceramic target. The phase of the target has been researched in experiment by X-ray diffraction (XRD). We found that solid state reaction has achieved completely. Then SrTiO3 thin films on MgO (100) substrate were manufactured by PLD using the triple-frequency harmonics of pulsed laser Nd: YAG. The thickness of the SrTiO3 thin films was measured using a stylus profiler. Their microstructure and surface morphology were analyzed using X-ray diffraction (XRD) and atomic force microscopy (AFM). Their optical character was characterized using optical transmission spectrum. Additionally, X-ray photoelectron spectroscopy (XPS) spectra were used to characterize the surface chemical composition of the SrTiO3 thin film. In accordance with the above text result, the relation between the substrate temperature and the SrTiO3 thin films' the structure and character was analyzed and discussed. With increasing temperature of the substrate, film grain size gradually increased and then smaller. The optimized substrate temperature was found to be 700 °C at which the STO films' structure could uniformly dense. The STO films present a low optical absorption in the 400~1000nm wavelength range, and the substrate temperature is not the main reason for the impact of the optical absorption. The optical band gap energy was found to be about 3.5 ~ 4.0eV for the STO thin film. The valences of the three elements (Sr, Ti, and O) in the STO film prepared by PLD are 2+, 4+ and 2-, respectively.
Numerical simulation of multilayer organic light-emitting devices
Hansong Gao, Haibo Rao, Yue Hu, et al.
A numerical model of multilayer organic light-emitting devices (OLED) is presented in this paper which was consisted of electrical and optical model. The electrical model is based on the drift-diffusion equations. Multilayer organic heterojunctions were mostly considered in this work. A simulation course was programmed with MATLAB. The I-V characteristics obtained show a good agreement with experiment data. The optical model utilizes the optical interface effect, the EL spectrum was calculated with Alq3 thickness of 40 nm, 50 nm and 60 nm, respectively. The Brightness- Voltage characteristics was simulated, the results and experimental data in the literature are in good agreement on the magnitude.
The low-cost preparation of pyramid-like texture ZnO thin films and the application as a front electrode in hydrogen amorphous silicon solar cells
Y. H. Hu, L. F, Wang, H. J. Xu, et al.
The pyramid-like texture ZnO thin films were usually synthesized by MOCVD or etching the as-prepared RF magnetron sputtering films, and the expensive equipment cost and uncontrollable acid etching, respectively are two main disadvantages both the MOCVD and RF magnetron sputtered. In this paper, the pyramid-like texture ZnO thin films were prepared through a low-cost two-step process, firstly, a seed ZnO:Al layer was coated on the quartz substrates by sol-gel method and subsequently a ZnO thin film was fabricated by RF magnetron sputtered. It is shown from the XRD and SEM results that the ZnO thin film has (101) preferential orientation with a pyramid-like texture. According to the measurement results of ZnO films' resistivity and UV-Visible transmission spectra, the lower resistivity of 10-3 Ω•cm and optical transmission of higher than 80 % were obtained for these ZnO films. It has shown that the pyramid-like ZnO thin film is a potential transparent conductive film used in amorphous silicon solar cell for front electrode, and the cell performance is comparable advantages for that of ITO conductive film.
5-2
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Substrate temperature influence on the properties of InGaZnO thin films grown by PLD technique
In this paper, the effects of substrate temperature during film growth at relative high temperature have been reported. The IGZO thin films were fabricated by means of pulse laser deposition (PLD) with the InGaZnO (In2O3: Ga2O3: ZnO=1: 1: 8 mol %) target. The substrate temperature altered from room temperature (RT) to 800 °C. The product thin films were characterized rigorously by X-ray diffraction (XRD), atomic force microscopy (AFM), UV-VIS spectrometer, Halleffect investigation and X-ray photoelectron spectroscopy (XPS). The IGZO films was with smooth surface, high transmission in the visible spectral range (about 75-92 %), carrier mobility > 8.0 cm2/(V·s) and carrier concentration at about 1018 cm-3. Finally, the character changes influenced by temperature were obtained from analysis results. This task may benefit to a flat panel display in the process of thin film transistors(TFT) fabrications and improvements.
Polymer PSQ-L notch filter fabricated by simple nanoimprint process
Jie Teng, Xiuyou Han, Mingshan Zhao
Polymers are emerging as an important material in the field of integrated optics. In this paper, we propose a simple method to fabricate polymer waveguides by using a novel polymer PSQ-L. The high index polymer PSQ-LH is used as a core material and the low index polymer PSQ-LL is used as a cladding material. The waveguide circuits are replicated by using a UV-based soft lithography process. Unlike in conventional imprint processes, the imprint step for structuring is done first on the cladding layer rather than on the core layer and is followed by a spin-coating step to fill the imprinted features with core layer material. The all-polymer microring resonators are fabricated by this method. The coupling efficiency between the straight waveguides and the ring is adjusted by controlling the gap distance between the straight waveguides and the ring. About 20dB extinction ratio and a high Q factor of 3.4×104 is obtained for critically coupled PSQ-L ring resonator.
Effect of triplet energy and transporting property of electron transporting material on iridium complex yellow phosphorescent organic light-emitting devices
Wen Wen, Junsheng Yu, Sujie Chen, et al.
Balanced charge carrier and appropriate exciton confinement are considered as the key factors for the realization of highly efficient and stable organic light-emitting devices (OLEDs). An effective way to reach a loss free hole-electron recombination and exciton leakage is to use suitable electron transporting layers (ETLs). To investigate the influence of triplet energy and electron transporting properties of ETLs on the performance of iridium complex yellow phosphorescent OLEDs, we fabricated three devices based on bis[2-(4-tert-butylphenyl)benzothiazolato-N,C2']iridium (acetylacetonate) [(t-bt)2Ir(acac)] doped 4,4'-bis(carbazol-9-yl) biphenyl (CBP) host by using 2,9-dimethyl-4,7-diphenyl- 1,10-phenanthroline (BCP), 1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene (TPBi), and 4,7-diphyenyl-1,10- phenanthroline (BPhen) as ETLs, respectively. It was found that there was no apparent correlation between the device efficiency and the triplet energy of ETLs. Instead, device efficiency was determined by the electron mobility of ETLs only. With an optimized device using BPhen as ETL, a power efficiency of 23.1 lm/W and a current efficiency of 28.0 cd/A at 0.08 mA/cm2 were achieved, which was much higher than that of the control devices (7.5 lm/W for BCP-device and 8.5 lm/W for TPBi-device). The improved efficiency was attributed to that BPhen had the highest electron mobility and provided better charge balance in the hole-dominant devices. Moreover, the EL spectra of three devices showed no obvious difference with a light emission from iridium complex peaked at 562 nm and a shoulder peak at 600 nm. This indicated that no matter BCP, TPBi or BPhen acted as ETLs, the (t-bt)2Ir(acac) triplet exciton can be confined within the emissive layer effectively.
Solvothermal synthesis of platinum nanoparticles and their SERS properties
Yong Yang, Zhengren Huang, Dan Li, et al.
The controllable preparation of platinum nanoparticles with defined shapes, including sphere, octahedron, octapods and tetrapods, was realized by varying the concentration of NaNO3 in the solvothermal process. NaNO3 plays a critical role in synthesizing Pt nanoparticles with different shapes. These Pt nanoparticles were self-assembled on glass substrates to study the influence of metal nanoparticles' shape on their SERS enhancement using 4-mercaptopyridine as molecules probes. Thanks to the enhanced local field effect around their sharp corners and edges, those Pt tetrapods exhibit enhanced SERS properties than those particles with other shapes.
Theoretical and experimental demonstration of phase locking technology by utilizing cubic susceptibility medium
Liang Zhao, Junqiang Sun
A novel proposal for phase locking based on cubic susceptibility medium has been theoretically proposed and experimentally demonstrated. The expression for phase difference between injected waves is yielded from the coupled wave equations, which implies the phase noise can be eliminated through low-efficiency four-wave mixing (FWM). Beat-note signal and autocorrelation trace heterodyned by the injected waves with small and large detune are adopted to assess phase locking effect, and they are monitored by electrical spectrum analyzer (ESA) and autocorrelator (AC) respectively. Moreover, the influence of polarization state on phase locking is also investigated, and experimental results match well with the theoretical predictions.
Steady enhancement of organic solar cell performance by doping phosphorescent iridium complex
Jiang Huang, Junsheng Yu, Hong Wang
Efficient organic photovoltaic cells based on a phosphor of (t-bt)2Ir(acac) were demonstrated. Also, the photovoltaic performances of organic solar cells with a device structure of ITO/(t-bt)2Ir(acac):CuPc (doping rate R=0 and 0.25)/C60/BCP/Ag were determined based on the current density (J)-voltage (V) curves of a series of devices. The absorption spectra of doping layer (t-bt)2Ir(acac):CuPc and C60 films on quart substrates were measured to gain a direct insight of absorption ability of dopant (t-bt)2Ir(acac). Then, revised optical transfer matrix theory was adopted to study inner effect of dopant (t-bt)2Ir(acac) on the enhanced device performance, which shows that (t-bt)2Ir(acac) dopant increases the light density of doping layer by reorganizing the light distribution inside organic films. However, the light absorption efficiency ηA of device with R=0.25 does not improve. According to the unchanging value of open circuit voltage VOC and similar fill factor FF, the assumption that two devices with R=0 and 0.25 possess similar charge carrier collection efficiency ηCTηCC can be made. Thus, the inner enhancement of exciton diffusion efficiency ηED is discovered with the assistance of longer triplet exciton diffusion length of (t-bt)2Ir(acac).
The application of ALD process on special fiber
Guangyuan Wei, Ru Zhang, Peilin Lang
The film thickness and the composition of the fiber can be controlled by ALD (Atomic Layer Deposition) process at atomic level. Therefore, a special fiber with the structure of alternating deposition of doped Nano-semiconductor materials (such as PbS, InP etc.) and SiO2 can be manufactured by ALD process. In a word, this would not only change the manufacturing technology of fiber, but also greatly changed the structure of fiber. In this paper the Band-gap energy and absorption wavelength is calculated for different nano-particle size by the influence of Quantum Size Effect. Considering the 1550 nm wavelength used widely in optical communication, the particle size is calculated, which is used in a simulated structure of the special fiber. Then Based on the simulation of the distribution of optical field, we draw a conclusion that the light field intensity in the special fiber is lower than the single fiber. Therefore, a high-power pumping light should be added if the special fiber is used as amplifying fiber.
Research on high-speed single photon detector
Chao Wang, Hao Yang, Di Wang, et al.
Single-photon detector based on an InGaAs avalanche photodiode is one of hot research on the quantum photon, and is one of the key technologies on quantum communication and quantum image. It is widely used in applications as high sensitive photon spectrum, high speed optic measurement and so on. A suitable delay and comparator with latch function circuit are used to prevent positive and negative transient pulses from influencing the detection of true photon induced avalanches. A dead time modulation feedback control circuit decreases the after-pulse. Especially, ECL difference circuit is the key of high speed single photon detector. In addition, the detector uses the hot tube fan-cooling method. From the performance test, the lowest temperature reaches -62°C, the minimum gate pulse width is 2ns (Full-Width-Half-Max, FWHM) and the dark counter rate is 2.5×10-6 ns-1 with a detection rate of 10MHz when the quantum efficiency is more than 10%.
Simple defogging method for outdoor images based on physical model
Jia Guo, Xiaotong Wang, Chengpeng Hu, et al.
Images of scenes acquired in bad weather have poor contrasts and colors. In this paper, we exploit the idea of interactive method and recover the images based on physical model. First, a simple method is proposed to estimate the scene depths. Second, the parameters in the depths model can be obtained automatically from a single image. Experiments show that our method can remove the haze effectively. Especially, it is easy to serve for the practice.
Quantitative analysis on flyback region problem of 1D transmissive liquid crystal optical phased array devices
Lin Xu, Ziqiang Huang
In practical application of Liquid crystal optical phased array (LCOPA) device, diffraction efficiency and deflection range are two important performance parameters, which should be improved further more. Both diffraction efficiency and deflection range are directly related to the width of flyback region. Therefore, the flyback region problem was analyzed quantitatively in this paper. According to elastic continuum theory of liquid crystal and crystal optics theory, we calculated LC director and its phase delay profile. Then we analyzed quantitatively the influence of device parameters including electrode size, alignment layer thickness and LC cell thickness on the width of flyback region. Results show that there exists a critical value of electrode size. When electrode size is larger than this critical value, the width of flyback region increases nearly linear to the increase of electrode size. The width of flyback region is not sensitive to alignment layer thickness and increases monotonously with the increase of LC cell thickness.
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Nano-optical microscopy: now and its industrialization
Shifa Wu, Zhao Wang, Jian Zhang, et al.
It is a review about the industrialization of Nano-Optical Microscope (NOM, also referred to as the Near-field Optical Microscope). Two comparisons of AF/PSTM (Transmission Mode) with the first generation commercial A-SNOM and AF/RNOM(Reflective Mode) with A-RNOM have discussed. The commercially used A-SNOM can only obtain a transmissivity image of A-SNOM-T(x,y), but AF/PSTM can obtain the separating the transmissivity image PSTM-T(x,y) and the refractive index imge PSTM-n1(x,y). AF/RNOM can obtain the lower contrast reflective index image but ARNOM cannot. The reason how could Pohl have obtained the first A-SNOM image with a resolution of 20-25nm in 1984 but the commercial A-SNOM-T(x,y) only with the resolution in the 50~100nm range is also discussed. Conclusion on the proposal of AF/PSTM and combined AF/RNOM may be the best candidate for the second generation commercial use of NOM.
Study of the transfer function of atmosphere to operation range of IRFPA
Wei Dong, Ying An, Wenjian Chen
There are much more need to characterize and evaluate performance of IRFPA in field. MRTD, MTF, NETD and operating range R are some of the key parameters of IR devices and used to characterize their performance. Around of these parameters there are two ways: analysis in theory and test. The research of these parameters in theory can be used to predict the performance of IR devices and these parameters can be proved by experiments. Whereas these parameters are hard to be tested in field, their test reports are based on experiment in laboratory. So it is very hard to explain or predict the test results of IR devices in theory because of the influence of atmosphere. This paper presents research of transfer function of atmosphere. A model of transfer function with the modified absorption and scatter coefficient is introduced based on the theory of transfer function. The operating range can be modified by transfer function of atmosphere. The experiment results show this model can be used together with operating range in some circumstances. It could be used in the predicting the operating range of IR devices in theory.
Thickness effect and etching implement of silicon substrate of LiTaO3 thin film infrared detector
Deyin Zhang, Wentian Luo, Yong Bao, et al.
The pyroelectric LiTaO3 thin film has low heat capacity, low thermal loss, high pyroelectric response and high possibility to make infrared detector, so the LiTaO3 thin film infrared detector preparation is considered in this paper. During the fabricated experiments, the silicon substrate thickness effect on performance of the LiTaO3 thin film device is very large, and therefore it has been theoretically investigated by using the MATLAB software and by employing one-dimensional heat conduction equation. The simulation results show the thinner the silicon substrate, the less the thermal loss by conduction, and thus, the higher the pyroelectric response of the LiTaO3 thin film device. To verify the theoretical analysis, the LiTaO3 thin film device deposited on the Pt/Ti/SiNx/SiO2/Si(100) substrate with different silicon substrate thickness are fabricated and the etching process of the silicon substrate have been discussed in details. The experimental results of the current responsivitiy and the specific detectivity of the LiTaO3 thin film device agree with the theoretical analysis. The theoretically and experimental results are together determined that, thoroughly etched-off the silicon substrate is the best method to reduce thermal loss and improve the property of the LiTaO3 thin film device.
Realization of large open circuit voltage in organic photovoltaic cells by introducing a fluorescent dye layer
Nana Wang, Junsheng Yu, Yue Zang, et al.
Small-molecule organic photovoltaic (OPV) cell with a large open circuit voltage (VOC) has been achieved by introducing 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) as donor layer. In order to obtain large VOC of standard copper phthalocyanine (CuPc)/C60 OPV cell, a very thin layer of DCJTB was inserted between CuPc and C60. It was found that the device formed multicharge separation interfaces. The VOC of device with 2 nm DCJTB layer was increased from 0.44 to 0.58 V. Also, the atomic force microscope (AFM) 3D-images of the donor surfaces were characterize to discuss OPV cell performance improvement. Furthermore, the absorption spectrum shows that an additional thin DCJTB layer enhances the light harvest capability of the cell.
Electroluminescence performance of organic light-emitting diode with molybdenum trioxide inside hole transport layer
Ye Zou, Zhenbo Deng, Zhaoyue Lü, et al.
A new structure of organic light-emitting diode (OLED) was fabricated by inserting a thin molybdenum trioxide (MoO3) layer into hole transport layer (HTL) N,N'-diphenyl-N,N'-bis(1-napthyl-phenyl)-1,1'-biphenyl-4,4'-diamine (NPB). The device structure is ITO/NPB(10 nm)/MoO3(3 nm)/NPB (30 nm)/tris-(8-hydroxyquinoline) aluminum (Alq3) (60 nm)/LiF(0.5 nm)/Al. The control device is set without MoO3 interlayer. The driving voltage at 100 cd/m2 is only 4.87 V corresponding to the device with MoO3 interlayer, which is much lower than the control device of 6.40 V. The novel device also shows higher power efficiency compared to the control device. The improvement of device performance is attributed to the Charge Transfer complex (CT complex), generated at the NPB/MoO3/NPB interfaces, contributing here as hole transfer enhancer. Our finding additionally demonstrates the practical applicability of MoO3 as a buffer layer in OLEDs.
Fraunhofer diffraction of the object with inclined plane
Anqing Zhao
Taking the rectangular hole as an example, this paper addresses the theoretical calculation and experimental observation of Fraunhofer diffraction field when the object plane is inclined to the system optical axis and compares it with that when the object plane is perpendicular to the system optical axis. The author finds in the experiment that the diffraction pattern changes when the object plane is inclined to the system optical axis. The theoretical significance of the paper lies in that it gives a general expression for Fraunhofer diffraction field. The situation that the object plane is perpendicular to the system optical axis is only a particular case for the above expression.
The research and analysis of TDICCD dynamic driving design
Yun Cheng, Tao Li
Compared with ordinary linear CCD, one of the most remarkable advantages of TDI/CCD is that it can work under low illumination conditions with imaging clearly. Meanwhile, multiple exposures can reduce pixel inconsistency and the fixed-pattern noise; enhance the Sensitivity and Uniformity of visible light CCD. As a result, TDI/CCD has an extensive application in the aerospace industry. To meet the needs of orientation of TDI/CCD's application towards high-speedy, miniaturization and intellectualization, in this paper,Fairchild Imaging CCD525 is chosen as image sensor,by means of programming on XC2V1000 which is one type of Virtex-II serials FPGA, using the key technology such as IP reuse,DCM and timing constrain, realized the functions of real-time adjustment of TDI integration time,number of integration stages,VGA gain and digital quantitative deviation. The whole system not merely passed the software simulation on ModelSim,and achieved satisfactory effect in practical application.
Research on accelerometer based on multi-mode interference
Qiaofen Zhou, Changlun Hou, Guoguang Yang, et al.
A new type of accelerometer is advanced which is based on optical fiber multi-mode interference (MMI). We use a structure that a multi-mode fiber connected to two single mode fibers as the sensing part of the accelerometer. By measuring the changes of the output spectrum can get the acceleration. This paper describes the principle of the accelerometer based on multi-mode interference, and a theoretical simulation is performed. In the experiment a Piezoelectric Ceramic is applied to simulate the Static Acceleration. The result manifests that this type of accelerometer has a great dynamic range and a good resolution, also it's easy to fabricate and low cost.
A novel chemically selective siloxane polymer for chemical vapor sensing
Jia Huang, Yadong Jiang, Xiaosong Du, et al.
A new hydrogen-bond acidic carbosiloxane polymer for quartz crystal microbalance sensors (QCMs) application was synthesized via O-alkylation, Claisen rearrange, hydrosilylation reaction and functionalized the polysiloxane with trifluoroacetone groups (TFA). The trifluoroisopropanol functionalized polysiloxane was characterized by FT-IR and 1HNMR. And this novel siloxane polymer was coated onto AT-cut 8 MHz QCM sensors to investigate its gas sensitive responses to the organophosphorus nerve agent stimulant dimethyl methylphosphonate (DMMP) vapor as well as other interfering organic vapors. The research work indicated that frequency shifts of the trifluoroisopropanol functionalized polysiloxane based QCM sensor to the DMMP vapor were completely linear, and with a regression coefficient of 0.9973 in the concentration range of 10-60 ppm. In addition, the sensitivity of the fabricated QCM sensors to DMMP was up to 10.64 Hz/ ppm, and much higher than the other interfering vapors, limits of detection (LODs) of the QCM sensors was 0.28 ppm, thus high selectivity to DMMP was demonstrated in this work.
Investigation of bright spatial solitons in SBN: 75 photorefractive crystal
Qinglin Guo, Guiying Deng, Baolai Liang, et al.
This work studied the formation of spatial solitons in a SBN: 75 photorefractive crystal by 532 nm continuous-wave laser beam from a single frequency solid laser. It was found that the behaviors of the spatial solitons varied with background light. While white light and 632 nm red light are used as background, the solitons perform like first-order light soliton. The compressed-amplitude, in measured with laser beam's size before and after passing the crystal, is proportional to the applied voltage of a dc electric field, i.e., they are quasi-steady-state solitons formed in a time window. However, as the background is changed to an incoherent 532 nm light output from the same laser, the solitons vary periodically and the compressed-amplitude is not proportional to the voltage of applied dc electric field any more. In this case, solitons form instantaneously at applied field of 900 V/cm and hold the shape for 7 seconds which is less than the one with white or red light as background, and then break slowly. We tried to present reasonable explanation for above observation.
Poster Session
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Daytime star detection device using polarization and spectral filtering method
Gongpu Lan, Wenli Ma, Feng Cheng
How to see the stars in daytime? A new idea is described here in this paper which uses a combination of two methods: one is traditional spectral filtering method and the other is a new attempt on daytime star detection--polarization method. Each of these two method's principle of work, scope of application and limitation on daytime star detection are introduced in detail; and the advantage of the combination is discussed accordingly. Based on the demand of the daytime star detection, a device is designed and its optical system and mechanical structure are also analyzed in this paper. At last, a further discussion of the existing problems and the possible improvements of the current device are presented.
Study of quantitative identification of infrared thermal wave testing based on BP neural networks
Zhang Wei, Liu Tao, Yangzheng Wei, et al.
In order to resolve the problem of quantitative identifying, in pulsed thermography, taking the highest temperature difference and the best testing time as input, and taking defect depth and diameter as output, made use of BP Neural Networks to achieve it, and it was done. According to result, when testing value was in area of swatch, identifying precision was high, and error is less than 3.5%. The feasibility of BP Neural Networks was validated, and it has very important meaning to quantitative identifying of factual application.
Quantum teleportation and survey technology
Zhiguo Wang
Quantum teleportation is an important component element of quantum information theory and is an effective method to realize quantum communication. This paper presents the realization method and survey technology of quantum teleportation, introduces the theory and experiment research process of quantum communication field and its broad prospect.
Effect of carrier gases on growth of thick GaN films by hydride vapour phase epitaxy
Ru Wang, Ruixia Yang, Junling Zhang, et al.
The effect of carrier gas on thick GaN film grown by hydride vapour phase epitaxy on (0001) sapphire substrate has been studied by double crystal X-ray diffraction (DCXRD), field emission scanning electron microscope (FE-SEM), photoluminescence (PL) and Hall tester. H2, as carrier, is propitious to two-dimension growth pattern of GaN film, but it causes production of more defects and impurities. Red shift of band edge emission of PL and a wider FWHM (full wave at half maximum) of DCXRD appear under H2 atmosphere. N2, as carrier, reduces the content of defects and impurities. However, the growth interface of GaN forms easily crystallographic facets but not epitaxial (0002) plane, which leads to appearing of embossed surface. It may gain high-quality HVPE-GaN that H2 and N2 are adopted as carrier gas sequentially.
Data processing based on 3D measurement system using disparity method
Shuping Yang
A double CCD Camera 3D measurement system, which is based on the Marr vision calculation theory, classical disparity imaging theory and stereo model, was designed. Method and related techniques have been described in this paper after analyzing and comparing deferent kinds of 3D testing methods, which provide references for the setting up of hardware system. Based on both eyes vision model, a set of 3D testing program based on disparity is designed. By analyzing the sample data: while the confidence is 0.99, the system precision is 0.01mm.
Traceable dynamic calibration for CHAL-010 thermocouple
Xiaojian Hao, Lina Hao, Sanping Jiang, et al.
Thermal inertia and finite heat conduction make the acquired temperature from temperature sensor be not reliable enough. So, it is necessary to make a dynamic calibration to the sensor. The frequency-response characteristics of high speed radiation thermometer surpass that of the temperature sensor; therefore it can be used as the reference value to calibrate the latter and let system error is corrected. The traceable dynamic calibration method is used to calibrate CHAL-010 thermocouple (manufactured by OMEGA Company). The thermocouple's time constant as well as error correction value of dynamic temperature measurement is obtained from it. The traceability is accomplished successfully through unbroken chain of comparisons with appropriate standard at the system.
Time constant measurement of thermocouple by use of modulated laser
Lina Hao, Xiaojian Hao, Sanping Jiang, et al.
A new time constant measurement means of the surface temperature sensor is proposed, in which a high frequency modulated high power CO2 laser acts as the driving source. The measurement system is designed and practiced in thermocouples with different temperature ranges. It is proved that the system can be used to measure transient surface temperature sensor which be with a time response from the sub-millisecond level to the second level, and the temperature provided by the driving source can range from the room temperature to the high temperature.
The design of mirror's temperature control system of three Antarctic Schmidt Telescopes
Jianlin Zhao, Daxing Wang, Xiangyan Yuan, et al.
Preliminary site testing shows that Antarctic inland Dome A is likely to be the best astronomical observatory site on the ground, Chinese first Antarctic astronomical equipment CSTAR has been successfully run Dome A. Three Antarctic Schmidt Telescopes (AST3) is the next important Antarctic astronomical equipment, one of which will be mounted Dome A. In the year of 2010, and the three will be installed Dome A finally. Because of the very low temperature and saturation vapor pressure, and the temperature gradient changes fast near the ground layer at Dome A, the mirror is easy to be frosted, which is one of difficulties to AST3.Indium Tin Oxide (ITO)is an N-type semiconductor material, because it has few resistors, good light transmission, good weather resistance, small environmental impact, low cost, and it is easy for large area coating, so it is widely used in many fields. The mirror is heated by ITO that is coated on the surface of the mirror, the voltage on the ITO will be tuned by changing the output pulse width, and then the system achieves a closed-loop control. The difference between the mirror temperature and ambient temperature will be maintained in an ideal range, and this will not only ensure that the mirror surface will not get frosting, but to minimize the impact of mirror seeing to guarantee the image quality of the telescope. The experimental results show that the temperature control system can control the different temperature between the mirror surface and the ambient less than 2 degree in real time, which can improve the mirror's working environment, and the overall effectiveness of the telescope's observations.
Viewing angle changeable display
Jinbi Leng, Ziqiang Huang, Wenjun Yang, et al.
Viewing angle changeable display can change the display viewing angle as needed: In the public place the display could have a narrow viewing angle for privacy, while in the private place the displays could have a wide viewing angle for the convenience of the operation and better viewing experience. This article propose a novel adjustable optical transmission device to realize the viewing angle changes for LCD by using the principle of guest- host effect of liquid crystal. The major technology is to insert a special equipment between the backlight and the LCD, through which the backlight will display either parallel or scattered features to get an either narrow or wide viewing angle. The equipment is an adjustable transmission cell (ATC) which is actually a black G-H LC cell. This ATC is the main focus of our invention. The ATC consists of a polarizer sheet and a special guest-host liquid crystal device filled with the two-phase dye (called as GH-LC in this report), to achieve the viewing angle change in the LCD. When an electrical field charges to the ATC, only the so-called near-axis lights can pass through the ATC within a relatively small angle, while the other scattered lights are absorbed sequentially by GH-LC and the polarizer sheet. On the other hand, when there is no electrical charge to the ATC, the cell behaves like a normal polarizer; and the scattered light can pass through the cell and polarizer in a normal way. This paper describes the principle and structure of the device, applies the electric field on the sample to observe the electro-optical properties, combine the theoretical and experimental research, getting the viewing angle effects of the display.
Principle and design of small-sized and high-definition x-ray machine
Anqing Zhao
The paper discusses the circuit design and working principles of VMOS PWM type 75KV10mA high frequency X-ray machine. The system mainly consists of silicon controlled rectifier, VMOS tube PWM type high-frequency and highvoltage inverter circuit, filament inverter circuit, high-voltage rectifier filter circuit and as X-ray tube. The working process can be carried out under the control of a single-chip microcomputer. Due to the small size and high resolution in imaging, the X-ray machine is mostly adopted for emergent medical diagnosis and specific circumstances where nondestructive tests are conducted.
The impact model of cumulative damage on the detection threshold of space optical communication
Guolong Chang, Yanping Zhou, Jing Ma, et al.
In order to improve the radiation hardness of free-space optical communication system, this paper theoretically deduces the radiation damage model of laser diodes' output power. For this model, the theory of Gaussian distribution is used to study the radiation influence on detection threshold of free-space optical communication on the condition that the bit error rate keeps invariable. The result shows that both the output power and detection threshold are the linear functions of total dose.
Dynamic MTF analysis and calculation of aerial camera
Jingyu Liao, Xiaodong Gao
Mechanical vibration is the main source limiting and damaging the resolution of aerial cameras. It is necessary to stabilize the line of sight (LOS) to guarantee the image quality. Using dynamic MTF to evaluate image quality and establish reasonable stabilization system performance standard, is a common artifice during the design process. Linear motion and high frequency vibration MTF have been expressed in closed form; however, low frequency vibration still cannot be solved analytically. A numerical dynamic MTF calculation method was developed. With this method and corresponding results, the image quality as well as affordable residual vibration under particular oscillations can be predicted. As a result, passive isolators and other image system devices can be selected effectively and properly.
Investigation of DBR used in HB-LED
Zhi-Quan Li, Ya-Nan Wang, Xiao-Gang Wu, et al.
The high brightness InGaAlP light emitting diodes(LED) is a novel solid-state lighting in recent years. As the absorption of the red light by the GaAs substrates decreased external quantum efficiency, the development and application of LED are limited. If all the light incident to the substrate can be reflected, the influences of substrate absorption are radically improved. Therefore, a novel distributed Bragg reflector(DBR) is proposed. The defect layer whose crystal lattice constant matched with the substrate grows among the DBR to change the reflectivity spetrum by regulating the defect layer meterial and thickness. According to matrices-optic theoretics, analogically compute the reflectivity and transmission spectrum of Al0.5Ga0.5As/AlAs DBR in which has defect layer, corresponding to the wavelength is 610nm and period is 15. The experimental results show that the reflectivity is not less than 0.6 as the incident angle is greater than 45°. Hence, a novel method is obtained for enhancing the LED external quantum efficiency.
Time information extraction of return signal for laser altimeter over ladder terrain
Wei Zhong, Xu Feng, Guohui Wu, et al.
Laser altimetry is a new measurement technique. Altimeter receives the return signals after launching laser pulses to the ground. Three-dimensional information on the ground is obtained by analyzing the corresponding relationship between return signal features and topographical features. But there is an apparent deficiency when using the data points to establish the three-dimensional DSM. That is the accurate time information of the return signal cannot be obtained when positioning the edge lines of the ladder terrain. In this article, the distribution of the echo waveform over the ladder terrain of city buildings is simulated by a self-designed altimeter waveform simulator under different direction angles and parameters of the terrain. The best extraction method of the return time information at the edge line is identified by analyzing the waveform characteristics at the edge line of this terrain, which enhances the accuracy of applications of the ladder terrain modeling. The time information of the return signal is extracted under various parameters by applying five methods which are accepted internationally, namely Peak point, Mean point, 50% Rise time point, Center of Area point, and Midpoint. Then the experiment values are compared to the actual values. According to the results of the simulations, the difference between the experiment value of the 50% Rise time point and the actual value is minimal. Its resolution ratio is about ten time units maintaining in a narrow range. It proves that this method can effectively improve the accuracy of the extracted time information of the return signal at the edge line over ladder terrain. And it provides a valid data source for establishing a more accurate DSM model.
Identification of the active photo-excited carrier in reverse biased quantum dot resonant tunneling diode
Wangping Wang, Wenxin Wang, Hong Chen, et al.
The active photo-excited carrier has been identified in reverse biased quantum dot resonant tunneling diode (QDRTD) for light detection. The QD is embedded on the AlAs/GaAs/AlAs double barrier part of the material structure and is found with strong charge memory effect. The QD is charged with electrons in forward bias and the charge storage of QD is maintained well in reverse bias until the voltage of QD resonant tunneling peak. With this charge memory effect, the photo-excited holes are charged into QDs in forward bias and still influence the reverse bias behavior of QDRTD at dark. Compared to the illuminated QDRTD in reverse bias, the active photo-excited carrier of reverse biased QDRTD is unambiguously identified as photo-excited holes. The potential profile of QDRTD structure is also calculated and the potential near charged QDs is found greatly pushed up above GaAs EC. This may explain the trapping of photo-excited hole by QD for QDRTD in reverse bias.
Research on phase detection on two-dimensional position sensitive detector
Feng Xi, Lan Qin, Lian Xue, et al.
Position sensitive detector (PSD) is based on the lateral photoelectric effect (LPE) to produce an electrical. The photocurrents output from the electrodes, so the amplitude and phase of the output signal are related to the distance between the light spot and the electrodes. The information of the phase was detached from photocurrent signal. The diversification of phase along with the distance was analyzed, and phase difference between the corresponding electrode signal current as well as the associated difference with the change of PSD related parameters. The result of experiment on one-dimensional and two-dimensional PSD is shown that the position detection error and the linearity all can meet the test requirements.
A real-time HCI system based on infrared tracking
Xin Liu, Yongtian Wang, Yue Liu, et al.
In this paper, a novel Human-Computer Interaction (HCI) system based on IR tracking technology is proposed for big projection screen real-time HCI applications. The proposed system has been successfully applied in a multiple-user shooting game. In this system, each user holds an interactive device, which is based on an ADSP-BF533 hardware platform, to interact with the shooting game on the big projection screen. IR tracking technology is introduced and theories for projective transformation are studied in detail. A fast IR marker identification algorithm is developed for real-time interaction. Two groups of IR markers are adopted in the proposed system for IR tracking, which are fixed on the border of the big projection screen. To utilize the theories for projective transformation, each group of IR marker is composed of 4 IR LEDs with a rectangular arrangement. There is a CMOS sensor inside each interactive device to capture the image of IR markers. The captured image is then used for image processing and IR marker identification on the ADSP-BF533 hardware platform. According to the theories for projective transformation, the target position on the big projection screen of each interactive device can be obtained after the projective transformation from the CMOS image to the big projection screen. An experimental environment is set up and experiments are implemented to test the validation of the performance of the IR marker identification algorithm, i.e. tracking accuracy, time consuming and effective region of the proposed system. Experimental results show that the proposed system is very efficient and robust for big projection screen interaction application. The IR markers can be correctly identified with the identification algorithm developed in this paper. Experimental results also show that the developed system can achieve real-time processing and work with high tracking accuracy. The proposed system works well in a large effective region that allows multiple-user interaction. Moreover, the proposed system can be extended to bigger projection screen interaction applications with the adoption of more groups of IR marker.
Theoretical study on the cross sensitivity of fiber Bragg grating sensor affected by multi-external fields
Binbin Luo, Mingfu Zhao, Saofei Wang, et al.
The applications of Fiber Bragg grating (FBG) sensors have been concerned considerably for many years. However, it is usually difficult to obtain an accurate result by single FBG in practical applications, since the phenomenon of cross sensitivity caused by the multi-external fields always exists. In the past, most of researchers presented their studies only on the cross sensitivity of two parameters including temperature and axial strain, temperature and transverse pressure, and so on. Actually, FBG sensors might be affected by temperature field, axial strain field and transverse pressure field simultaneously in some applications, but no previous analysis has been presented on the cross sensitivity caused by these three parameters. This work extends the previous works on the cross sensitivity of two parameters to that of three parameters in a FBG sensor. The sensing model of FBG in three external fields is deduced and analyzed theoretically from the perspective of its physical mechanism, through which the expression of the cross sensitivity function is obtained. Meanwhile, examples of different external physical factors and fiber parameters are considered for illustration purposes, and the cross sensitivity term is discussed by the numerical simulation. The simulated results show that the properties of cross sensitivity would change in a certain regulation with the changes of external effects and fiber parameters. Compared to the two-parameter analyzing method, this work makes a more comprehensive analysis to the research object. Some valuable suggestions about how to reduce the systematic error and improve the measurement accuracy are put forward as well.
Laser pumping magnetic resonance of theory research based on coherent population trapping
Zhang Yang, Kang Chong, Qingtao Wang, et al.
In the Λ three-level system, we will make use of semi-classical density matrix method to analyze cesium (Cs) hyperfine structure of coherent population trapping (CPT) phenomenon. Coherent population trapping has been widely used in electromagnetically induced transparency, non-inversion laser, optical storage and ultra-slow speed of light fields, then strong-coupling light and weak detecting light form coherent laser light to change the hyperfine structure energy levels of particles number distribution, which impacts on laser pumping magnetic resonance. In this paper, we will discuss the theoretical analysis and system design of laser pumping cesium magnetometer, cesium atomic energy level formed hyperfine structure with the I-J coupling, the hyperfine structure has been further split into Zeeman sublevels for the effects of magnetic field. To use laser pump and RF magnetic field make electrons transition in the Zeeman sublevels to produce the results of magneto-optical double resonance and on this basis we analyze the influence of laser pumping magnetic resonance based on coherent population trapping.
Preparation of negative electron affinity gallium nitride photocathode
Negative electron affinity (NEA) Gallium Nitride (GaN) photocathode is an ideal new kind of UV photocathode. NEA GaN photocathode is widely used in such fields as high-performance ultraviolet photoelectric detector, electron beam lithography etc. The preparation of negative electron affinity gallium nitride photocathode relates to the growth technology, the cleaning method, the activation method and the evaluation of photocathode. The mainstream growth technology of GaN photocathode such as metal organic chemistry vapor phase deposits technology, molecule beam epitaxial technology and halide vapor phase epitaxial technology were discussed. The chemical cleaning method and the heat cleaning method for GaN photocathode were given in detail. After the chemical cleaning, the atom clean surface was gotten by a 700 °C heat about 20 minutes in the vacuum system. The activation of GaN photocathode can be realized with only Cs or with Cs/O alternately. Using the activation and evaluation system for NEA photocathode, the photocurrent curve during Cs activation process for GaN photocathode was gotten. The evaluation of photocathode can be done by measuring the quantum efficiency. Employing the UV spectral response measurement instrument, the spectral response and quantum efficiency of NEA GaN photocathode were measured. The measured quantum efficiency of reflection-mode NEA GaN photocathode reached up to 37% at 230 nm.
Research on effect of Kell coefficient on the quality of aerial photography
Yue Fan, Wenli Ma
The method of Spatial convolution is applied to analyze the imaging process of the CCD imaging system, which involves optical imaging process and CCD integral sampling process, and the ratio between GRD and GSD that is called Kell coefficient is introduced, based on which, analysis of effect of Kell coefficient on the quality of aerial photography is educed. Imaging process of the target is simulated with different Kell coefficient values by matlab. The method of the gray difference between the target and the image on CCD which is regarded as the evaluation criteria is proposed to evaluate the image quality. The simulation results show that when Kell coefficient equals 2.8, the target characteristics can be distinguished.
Luminescent properties of BaAl2Si2O8:Eu2+, Mn2+ phosphor for white LED
Changyu Shen, Ke Li
BaAl2Si2O8:xEu2+, yMn2+ was prepared by high-temperature solid state reaction and X-ray powder diffraction analysis confirmed the formation of it. It was found experimentally that, its emission peaks situated at 420 nm and 570 nm respectively under excitation of 380 nm irradiation. The emission peaks at 420 nm originate from the transition 5d to 4f of Eu2+ ions that occupy the Ba2+ sites in the crystal of BaAl2Si2O8, while the 580nm emission is attributed to the energy transfer from Eu2+ ions to Mn2+ ions. The white light can be obtained by combining the 380 nm chip with the phosphor. When the concentrations of the Eu2+ ions and Mn2+ ions were 0.05 mol and 0.35 mol respectively, the sample presented intense white emitting. The near-ultraviolet InGaN-based BaAl2Si2O8:0.05Eu2+, 0.35Mn2+ LED achieves good color rendering of 85 with the CIE coordinate of (0.3183, 0.3036).
The extraction and identification of target signature based coherent wavelet space frequency domain filtering
Zhaohui Li, Gang Li, Ming Chen
The location and identification of targets in grey images could be determined by wavelet space frequency domain identification filter according to coherent space frequency domain technology. Also the infrared spectrum radiation distribution about the targets could be got by the same algorithm. By making a comparison between the coherent and non-coherent wavelet space frequency domain filtering algorithms, we knew the former way could filter most clutter noises, leaving the primary elements about the targets. Both from target grey images and spectrum radiation, the primary content involved in the target images could be stressed by the former way. Especially more important is the extraction of target signatures by use of the coherent wavelet space frequency domain filtering algorithm in the spectrum radiation domain.
CVD diamond soft x-ray detectors
Lifei Hou, Guohong Yang, Shenye Liu
A class of wide band-gap semiconductor offers an attractive alternative to Si and X-ray diode (XRD) detector technologies for x-ray detection in Inertial Confinement Fusion (ICF) experiments. Because diamond presents high thermal conductivity, resistance and breakdown field, fast charge collection, low leakage current, wide band-gap, low dielectric constant, large carrier drift velocity and outstanding radiation hardness. Using chemical vapor deposited (CVD) technology, 1 mm×1 mm×2 mm, 1 mm×1 mm×3 mm diamond was synthesized. And the detectors were fielded with metal-semiconductor-metal structure. Characteristics of the detectors have been studied on a pulse laser equipment. The results indicate that the rise time and FWHM of the detector reach 60 ps and 120 ps respectively.
First-principles calculations for geometrical structures and electronic properties of nN-Mg codoped ZnO
We have investigated the geometrical structures, the electronic properties, and the formation energies of nN-Mg codoped ZnO in neutral state by adopting the first-principles calculations based on the density function theory (DFT). The calculated results indicate that N atoms prefer to occupy the substitution O site and Mg substitutes the Zn site of the nearest site of N, which act as an acceptor. Compared with the formation energies of various configurations in neutral state, it is found that 4N-Mg complex has the lowest formation energy using NO as dopant resource under Zn-rich condition, indicating that 4N-Mg codoping can enhance the N dopant solubility under this condition. Meanwhile, the Znrich condition is better for p-type doping than the O-rich condition. It demonstrates that 4N-Mg complex is in favor of achieving p-type conduction in ZnO. Simultaneously, analysis of density of states (DOS) of nN-Mg complex find that the valence band maximum (VBM) has a little raise near the Fermi energy level, indicating that the complexes are the typical p-type characteristic. However, for 4N-Mg complex, the Fermi level is located near the top of valence band. Furthermore, from the band structure and PDOS of 4N-Mg complex, it is observed that the complex produces an additional impurity band at the top of the valence band. Meanwhile, the PDOS value of 4N-Mg complex at the Fermi level is relatively large. In addition, 4N-Mg complex has much lower ionization energy of 0.167eV than that of other complexes. Therefore, better quality p-type conductivity is achieved by codoping 4N-Mg in ZnO.
Influence of baffle on improving the thickness uniformity of thin film deposited by magnetron sputtering system
He Yu, Yadong Jiang, Tao Wang, et al.
The way of improving the thickness uniformity of the thin film deposited by magnetron sputtering system is presented in this paper. A simple model for the magnetron sputtering system with a baffle between cathode target and substrate is described. Based on this model, it is possible to predict the relative deviation of film thickness with this baffle-model by taking the shape and size of baffle into the consideration. The purpose of this article is to explain how different baffle parameters affect the uniformity of thin film using the method of finite element with rectangle target in this magnetron system. It is found that there may exist optimum baffle conditions where the relative deviation of thin film thickness is less than 3 % with a diameter of Φ 150 mm substrate.
Analysis of titanium and vanadium oxide thin film by method of reactive co-sputtering
Tao Wang, Yadong Jiang, He Yu
A systematic simulation based on Berg's model and theoretic study of co-reactive sputtering of titanium and vanadium targets is presented. It enables one to predict the hysteresis effect and intermediate composition of the deposited film as a function of different targets current in the co-reactive sputtering process. With this approach, it is possible to obtain different stoichiometry of thin film by choosing different ratio of vanadium target current to titanium target current. In this case, the material composition in the thin film with respect to the fraction of these two targets current can be optimized. Finally, the deposition rate of co-reactive sputtering as a function of total sputtering rate of two metal material atoms is also described.
Photoluminescence investigation of InAs quantum dots in quantum well with different strain reducing layer
Lingmin Kong, Yunqing Zhou, Rui Wang, et al.
The emission dynamics properties of InAs self-assembled quantum dots (QDs) embedded in InGaAs/GaAs quantum well with different strain reducing layer (thin InAlAs and GaAs) were systematically investigated by time-resolved and temperature dependent photoluminescence (TR and TD PL) measurements. We observe that a thin 10 monolayer (ML) GaAs layer may increase the emission wavelength, and 1 nm additional InAlAs layer results a significant nonlinear redshift of above 1.3 μm photoluminescence (PL) peak, which can be explained from the strain analysis. TDPL spectra display an anomalous enhancement behavior of the integrated PL intensity around 150 K for the InAs QD structures without the InAlAs layer, which may be described by the reduced carrier transition at higher temperature for the higher energy barrier of the InAlAs layer. We study systematically PL decay time of the InAs with different structures. The PL lifetime of quantum dots grown on a 10 ML GaAs layer is a littler longer than those without the layer, and a more InAlAs layer may result in a greatly increase of PL lifetime, which implies that the InAlAs layer with higher energy barrier may enhance the quantum restriction of carriers in InAs QDs. The above phenomena also approve the facts that the main mode of carrier migration is quantum tunneling effects at lower temperature, while it is the quantum transition at the higher temperature. We explained these measuring results from the competition between the carrier recombination, escape and redistribution.
Laser active imaging-guided anti-tank missile system small-scale integration design
Mingliang Yan, Xiangqian Shan, Zhou Qu
At present, the domestic and international third-generation anti-tank missiles, laser-guided missiles are mostly divided into active laser-guided and laser semi-active guidance, this guidance system, there are vulnerable to electronic interference, can not be fully realized after launching deficiencies. Article based on this, an in-depth understanding of imaging-guided laser-active working principle, based on the pairs of third-generation anti-tank missile guidance system, boldly proposed to improve the anti-tank missiles, laser-active small-scale integration of imaging guidance system design, the main purpose is to improve a certain type of The optical target missile, TV angle measurement, laser-guided instruction transmission means, so that anti-tank missiles to achieve forward-looking, the next obstacle avoidance TV and multi-functional integration of the entire after launching smart missiles, and in theory be able to study the new antitank missiles play a certain reference.
Systematical investigations of annealing effects on electrical properties and thermal sensitivity characteristics of TiO2-δ thin films by DC reactive magnetron sputtering
Yonglong Qiu, Zhiming Wu, Yongfeng Ju, et al.
In recent years, TiO2-δ thin films as a kind of thermal sensitive material have been attracting more and more attention on the application of infrared devices. In this article, TiO2-δ thin films from the technology of DC reactive magnetron sputtering were deposited on glass substrates under the same sputtering conditions while different annealing conditions. Annealing effects on electrical properties and thermal sensitivity characteristics were systematically investigated under different annealing conditions including annealing circumstance, annealing time and annealing temperature. Results indicated that the sheet resistance (R) and temperature coefficient of resistance (TCR) of TiO2-δ thin films would decrease after vacuum-annealing and would increase after oxygen-annealing. Furthermore, they would increase more and more when the annealing time and the oxygen flux increased during oxygen-annealing. On the contrary, R and TCR would decrease when the annealing temperature went up. Based on that, TiO2-δ thin films could be better applied on related devices under proper technique of annealing.
A new method of building footprints detection using airborne laser scanning data and multispectral image
Yiping Luo, Ting Jiang, Shengli Gao, et al.
It presents a new approach for detecting building footprints in a combination of registered aerial image with multispectral bands and airborne laser scanning data synchronously obtained by Leica-Geosystems ALS40 and Applanix DACS-301 on the same platform. A two-step method for building detection was presented consisting of selecting 'building' candidate points and then classifying candidate points. A digital surface model(DSM) derived from last pulse laser scanning data was first filtered and the laser points were classified into classes 'ground' and 'building or tree' based on mathematic morphological filter. Then, 'ground' points were resample into digital elevation model(DEM), and a Normalized DSM(nDSM) was generated from DEM and DSM. The candidate points were selected from 'building or tree' points by height value and area threshold in nDSM. The candidate points were further classified into building points and tree points by using the support vector machines(SVM) classification method. Two classification tests were carried out using features only from laser scanning data and associated features from two input data sources. The features included height, height finite difference, RGB bands value, and so on. The RGB value of points was acquired by matching laser scanning data and image using collinear equation. The features of training points were presented as input data for SVM classification method, and cross validation was used to select best classification parameters. The determinant function could be constructed by the classification parameters and the class of candidate points was determined by determinant function. The result showed that associated features from two input data sources were superior to features only from laser scanning data. The accuracy of more than 90% was achieved for buildings in first kind of features.
Up-converion in bismuth doped fibers
Yanqing Qiu, Jianfeng Wang, Yongxing Jin
We investigated the up-conversion fluorescence characteristics of the bismuth doped silica fibers with and without Al codopant (BA fiber and BI fiber). Unusual up-conversion fluorescence was discovered in both of these two fibers when excited by pump lasers. After more experiments, it was found that the BI fiber showed more complicated and distinct upconversion spectrum than the BA fiber, but with different and weaker NIR emission as we reported before. And it was implied that the up-conversion fluorescence should be mainly responsible for the Bi2+ ions which was rich in BI fiber. Thus, by properly improve the Al co-doping concentration could alleviate the fluorescence up-conversion thus improve the efficiency of the NIR band fluorescence. Besides, the complicated up-conversion fluorescence bands may helpful to clarify the energy levels of the Bi ions in silica materials.
Design of optimized quantum well infrared photodetector's structure including higher order effects
Jupeng Jin, Chun Lin
Photoconductive GaAs/AlGaAs quantum well infrared photodetector (QWIP) achieves best performance when the well has its first excited state resonant with barrier height. Optimum QWIP structure parameters can be designed according to this rule. The parameters calculated by simple square well model taking account of variable effective mass are not accurate enough and can merely provide a rough estimation for actual QWIP devices. Higher order effects including band nonparabolicity, quantum confined Stark-effect and Coulomb interaction of large number of charge carriers (also known as Many-body effect) can have considerable influence on the energy level of quantum wells. Band nonparabolicity effect was included in the calculation in this paper. And a group of optimized GaAs/AlGaAs n-type QWIP structure parameters covering wavelength from 7 μm to 16 μm were systematically calculated, using one band effective mass approximation (EMA) and shooting method. These calculated results were carefully compared with those where band nonparabolicity was not considered, and 4 ± 2% discrepancy was found. Since a photoconductive QWIP normally works under a certain bias, change of the confined state energy level and shift of peak wavelength caused by the quantum confined Stark-effect were calculated and discussed. All the calculated quantum well structure parameters in this paper will offer a more accurate guide for QWIP fabrication.
Liquid crystal writable gratings for beam steering
Yali Gao, Mingwei Li, Yongji Shi, et al.
Liquid crystal writable grating technology is being developed for beam steering in laser radar systems. It is ability to steer broad-spectral -band radiation for us in passive sensors. There is potential for these devices in microscan systems because there is little or no dispersion for the small scan angles required in microscanning. The dispersion that is less than the resolution of the sensor considered here. For large angle steering, the dispersion correction or a narrowing of the spectral bandwidth is required. The degradation in sensitivity resulting from narrowing the spectral bandwidth is considered. A high quantum efficiently step-stare sensor with a two-dimensional focal plane array responsive over a narrow spectral width can achieve the same sensitivity as current linear scanning sensors while being able to steer the field of view(FOV) over a larger field of regard with no moving parts. A promising approach for steering a narrow FOV with broad spectral content and good resolution is described.
Detection algorithm of infrared small target based on improved SUSAN operator
Xingmiao Liu, Shicheng Wang
The methods of detecting small moving targets in infrared image sequences that contain moving nuisance objects and background noise is analyzed in this paper. A novel infrared small target detection algorithm based on improved SUSAN operator is put forward. The algorithm selects double templates for the infrared small target detection: one size is greater than the small target point size and another size is equal to the small target point size. First, the algorithm uses the big template to calculate the USAN of each pixel in the image and detect the small target, the edge of the image and isolated noise pixels; Then the algorithm uses the another template to calculate the USAN of pixels detected in the first step and improves the principles of SUSAN algorithm based on the characteristics of the small target so that the algorithm can only detect small targets and don't sensitive to the edge pixels of the image and isolated noise pixels. So the interference of the edge of the image and isolate noise points are removed and the candidate target points can be identified; At last, the target is detected by utilizing the continuity and consistency of target movement. The experimental results indicate that the improved SUSAN detection algorithm can quickly and effectively detect the infrared small targets.
Analyzing the emission self-organized structure in gas discharge by photoelectric detect method
Shuhua Liu, Fan Yang, Jianmin Song, et al.
In gas discharge, various self-organized structures are formed as the applied voltage is increased. A noticeable phenomenon is that the system undergoes twice hexagon structure. One is observed in the lower voltage range and the other is in the higher voltage range. To study the intrinsic mechanism, the light signal, electric signal, and the emission spectrum of the two hexagons is measured by photoelectric detect method. The electric signal is detected by high-voltage probe. The light signal is measured distinguished in time and space by using diaphragm. The electron excitation temperature is measured using spectrum method. It is conclude that the forming mechanism of the two kinds of hexagon is different. The lower-voltage hexagon is a dynamic multiplex structure, while the higher-voltage hexagon is a single static structure. The excitation temperature of higher-voltage hexagon is higher than that of lower-voltage hexagon.
Multi-feature fusion diagnosis for optoelectronic tracking devices using fuzzy measurement
Yong Zhang, Tianyong Zhang, Xianming Zhang, et al.
With the rapid development of optoelectronic tracking and measurement technology, tracking equipments become more complex and more precise, and the system faults happen at higher probability. The fault orientation, the fault analysis and the fault exclusion change more difficult. The single information and the simple process of multi-information have many deficiencies, which need fusion to improve the reliability. The D-S theory of evidence is a way to resolve the uncertain problems, which fuses evidences to reason the decision results in the same recognition frame used at the decisional level. Using the D-S theory of evidence, a diagnosis frame of multi-feature information fusion is proposed. The deviation ranks of the fault characters is defined according to their offsets from the normal and their happening probabilities were also computed by using the statistical results and the existing knowledge. The data reasoning of rough set theory is employed to construct the key fault evidence space from the multi features. Further, Gaussian subjection function from the fuzzy theory is used to describe the distribution of the key evidences and the distribution of the test data, and the basic probabilities of the evidence are weighed by the matching degree of the two distributions. The multiperiod and space feature information are employed and fused, and the final diagnosis decision is made by some effective methods. A multi-feature information fusion diagnosis for the servo system of the tracking equipment is discussed. The test shows that the diagnosis reliability is improved and the diagnosis uncertainty is reduced, and the fault diagnosis for the precise device and other parts are also effectively resolved by using this fusion method.
Effect of temperature on the growth of vanadium oxide films deposited by DC reactive magnetron sputtering
Mingjun Du, Zhiming Wu, Zhenfei Luo, et al.
Vanadium oxide films were prepared onto glass and KBr substrates at various deposition temperatures by DC reactive magnetron sputtering. X-Ray photoelectron spectroscopy (XPS), Atomic force microscope (AFM), Fourier transform infrared spectroscopy (FT-IR) were employed to analyze the VOx films, respectively. Experimental results indicated that deposition temperature has a great impact on the surface morphology of vanadium oxide films. The XPS analysis confirmed that the vanadium oxide films prepared are V2O5. From Fourier transform infrared spectroscopy, it can be see that the infrared active mode corresponding to V-O-V stretching vibration and the stretching vibration of unshared V=O bonds appeared at about 840 cm-1 and 915 cm-1 in the films formed at 240 , respectively. A shift in the peak position towards higher frequency was found with increasing the deposition temperature which indicated that the films formed at higher deposition temperature were structural disorder.
Measurement and analysis of modulation transfer function of the third generation low-light-level image intensifier
Junhong Su, Xiaofeng Bai, Feng Shi, et al.
The modulation transfer function (MTF) is measured at different illuminance in order to guarantee the veracity of measuring MTF of the third generation low-light-level image intensifier, the measuring result is analyzed. It is concluded that the law of MTF and illumiance, which is valuable for measuring MTF of the third generation low-light-level image intensifier and similar device.
Investigation of fabricating the films in the phase transition regime from amorphous to microcrystalline by MWECR CVD system
Y. J. Xie, Y. H. Hu, R. X. Xiao, et al.
The microcrystalline silicon films in the phase transition regime from amorphous to microcrystalline were fabricated by microwave electron-cyclotron-resonance chemical vapor deposition (MWECR CVD) system. The influence of deposition temperature and deposition pressure on the structure and electrical properties of microcrystalline silicon films was investigated. It is shown that the films in the phase transition regime from amorphous to microcrystalline are easier to fabricate under the condition of lower deposition pressure and higher substrate temperature. For example, the films in the phase transition regime whose crystalline volume fraction is about 30 %, were deposited at substrate temperature of 170 °C and deposition pressure of 0.7 Pa. The films' μτ product is about the order of magnitude of 10-5, whose magnitude is two order higher than that of amorphous silicon films, and their photosensitivity is about 103~104. Therefore, having both high stability and excellent optoelectric properties of the high-quality and device grade film, it is suitable to fabricate the intrinsic materials for amorphous silicon based solar cells.
Inspection focus technology of space tridimensional mapping camera based on astigmatic method
Zhi Wang, Liping Zhang
The CCD plane of the space tridimensional mapping camera will be deviated from the focal plane(including the CCD plane deviated due to camera focal length changed), under the condition of space environment and vibration, impact when satellite is launching, image resolution ratio will be descended because defocusing. For tridimensional mapping camera, principal point position and focal length variation of the camera affect positioning accuracy of ground target, conventional solution is under the condition of vacuum and focusing range, calibrate the position of CCD plane with code of photoelectric encoder, when the camera defocusing in orbit, the magnitude and direction of defocusing amount are obtained by photoelectric encoder, then the focusing mechanism driven by step motor to compensate defocusing amount of the CCD plane. For tridimensional mapping camera, under the condition of space environment and vibration, impact when satellite is launching, if the camera focal length changes, above focusing method has been meaningless. Thus, the measuring and focusing method was put forward based on astigmation, a quadrant detector was adopted to measure the astigmation caused by the deviation of the CCD plane, refer to calibrated relation between the CCD plane poison and the asrigmation, the deviation vector of the CCD plane can be obtained. This method includes all factors caused deviation of the CCD plane, experimental results show that the focusing resolution of mapping camera focusing mechanism based on astigmatic method can reach 0.25 μm.
Detection of weak and small infrered targets under complicated background
Jinling Chen, Jiming Zhang, Linming Deng, et al.
The technique of weak small target detection and recognition has been the key technique of the electro-optical detecting system, many scholars are engaging the research of detection for weak and small targets. The effective detection for small targets in low SNR images is still a hot research field. Because infrared sensor is easily affected by atmosphere hot radiation, long distance and sensor noise, the detected targets in infrared images often present like small targets and drowned in noise. The basic problem inherent to extent the detection range is the detection of small, low observable, no obvious structural information in images and complicated background. In order to improve the detection ratio of weak small targets and decrease the false alarming ratio in the condition of complicated background, the paper presents the technology of pretreatment of infrared images and the technology of detection for weak small targets, mainly including the technology of Sobel edge algorithm and multi-degree and multi-orientation gradient. Based upon horizon-correlative characteristic of infrared images which were gotten by scanning, considering of the target properties in complicated background, an algorithm of weak and small target detection is presented. Because the images appear horizon-correlative characteristic, Sobel horizontal operator is adopted. By this algorithm, the background clutter was suppressed. Then an adaptive threshold was proposed to extract the precise location of small target. Incorporated with the two methods, a single frame weak and small target detection algorithm was built. Its high performance was then proved in a serial of experiments. In order to solve the detection problems of weak and small infrared targets under complicated background, a detection algorithm integrating with multi-degree and multi-orientation gradient fusion is proposed. Based on the principle of infrared radiation property of target, i.e., the gradient variations of pixel gray scale in horizontal and vertical directions, the algorithm handles the property of weak and small target into analysis of image singularity and detects targets by means of multi-degree gradient step length. Then the detected results show this method can remove most false targets. As a result, the algorithms have fulfilled the engineering demands for reliability and real-time property.
Influences of process parameters of low frequency PECVD technology on intrinsic stress of silicon nitride thin film
Weizhi Li, Zhe Kang, Yun Ye, et al.
Silicon nitride (SiNx) thin films were deposited by low frequency (LF) plasma enhanced chemical vapor deposition (PECVD) technology. By systematic variation of the process parameters, e.g. reactive gas flow rate, LF power, chamber gas pressure and substrate temperature. Influences of above parameters on the intrinsic stress of SiNx films were studied and analyzed by combining with the measured refractive index (RI), density, infrared spectra results of deposited SiNx films. The results showed that intrinsic stress of SiNx film was roughly proportional to film density, which was inversely proportional to hydrogen content in the SiNx film. Substrate temperature during deposition was the most important factor affecting hydrogen content in deposited film and, accordingly, the density and intrinsic stress of SiNx film.
Optical fiber sensor for nitroaromatic explosives based on fluorescence quenching
Fenghong Chu
The detection of explosives and related compounds is important in both forensic and environmental applications. In this paper, we report on the preparation of novel plastic optical fiber explosive sensor based on fluorescence quenching. A low priced LED light source and PIN detector were used in this sensor system, a U-shaped plastic optical fiber with high sensitivity act as sensor head. We use amplifying fluorescent polymers (AFP) MEH-PPV as fluorescence indictor. MEHPPV was dip coated on to the surface of the U-shaped plastic optical fiber. For the first time as far as we know we detected the fluorescence lifetime by the phase-fluorometry method to measure the concentration of TNT, which has a merit of immunity to fluctuation of the light source and is more reliable than measuring intensity alone. In the experimental set-up the phase shift between excitation light and fluorescence is calculated by correlation method. Two degree phase difference was measured when the sensor head was exposed to TNT vapor and air in primary experiments.
Calculation of intrinsic surface acoustic wave velocity in LiNbO3
Tao Liu, Kuanxin Yu
Lithium Niobate (LN) crystal has excellent piezoelectric properties, it can be used as substrates of surface acoustic wave (SAW) devices, for example delay line, filter, oscillator, convolver and so on. Intrinsic SAW velocity is determined by the internal property of crystals. In this paper, SAW acoustic basic equation group and SAW mechanical boundary condition equation group are deduced. Intrinsic SAW velocities are calculated systematically using a circle iterative method in zx, xy and yz three coordinate planes of LN along different directions. Stiffness coefficient of piezoelectric crystal can be changed by piezoelectric effect and it is named as piezoelectric modified stiffness coefficient. Reciprocal velocity Curves of LN in the three coordinate planes using the non-modified stiffness coefficients and the modified stiffness coefficients are drawn. Many characters of the SAW device are related to the acoustic velocities, so research results lay a solid base for design and manufacture of the SAW device. It has theoretical significance and practical value.
Optimum cut direction of lithium niobate as substrate in surface acoustic wave devices
Kuanxin Yu, Tao Liu
A cut direction, rotated ZY cut of Lithium Niobate (LN), is studied. LN is a good piezoelectric crystal and it can be used as substrate of surface acoustic wave devices. In this paper, surface acoustic wave equations, including basic equations and boundary condition equations, are deduced. According to these equations the surface acoustic wave velocities are systematically calculated using a circle iterative method for LN along different directions in optimum decoupling acoustic sagittal YZ plane. The electromechanical coupling coefficients for rotated ZY cut LN are also calculated. The optimum cut direction of the LN crystal piece as substrate of surface acoustic wave devices is determined by the largest electromechanical coupling coefficient.
Study on the cloud layer height and properties in Hefei observed by lidar
Zhenyi Chen, Wenqing Liu, Yujun Zhang, et al.
A co-axial transmission elastic-backscattered lidar aiming to detect the optical properties of the clouds is presented in this paper. The modular co-axial design can guarantee the consistency of the transmitting part and the receiving part. In practice a specific diaphragm is used to suppress the stray light of the primary mirror and background light to improve SNR of the backscattered signal in the daytime. So the near ground signal must be corrected with the appropriate overlap factor. A Licel transient recorder is used for data acquisition in analog and photon counting combined in one acquisition system. With the 15 MHz sampling rate, the spatial resolution of 10 m can be attained. The control over the transient recorder and the treatment of the data is performed on a PC. After getting the correctional backscattered signal, retrieving and analyzing the extinction coefficient profile, the cloud base, cloud peak and related optical parameters of the clouds can be confirmed. In order to testify the feasibility of our lidar, it was implemented with a Finland ceilometer Vaisala simultaneously in May in 2008 in Hefei. Results show the lidar system is stable and the data is reliable.
Analysis of properties of ZnCoO bulks by solid state reaction
Xueqiong Su, Li Wang, Jiangbo Chen, et al.
Zn0.9Co0.1O bulks were prepared by solid state reaction at various fritting temperatures in order to investigate the structural and optical properties of the bulks. The valence electron and doping concentration in bulk was measured by Xray photoelectron spectroscopy (XPS) instrument. Some basic properties of the bulk material in powder were examined to enhance the comprehension of magnetism in these semiconductors. The corresponding magnetic properties were evaluated by field-cooling and zero-field-cooling magnetization measurements, while the optical properties were tested by Fourier transformed infrared spectrum (FTIR). It is indcated that Co ions are well inserted in the ZnO structure and surrounded by four oxygen. It means that a series of Co have substituted Zn and the sample all the same maintains original wurtzite structure in lattice with a sintered temperature of 1200 °C, then it leads to chemical bond formation of Co-O. Furthermore, the fritting temperature do not play a crucial role in the determination of Co content.
Method of improving the accuracy of image motion measurement for panoramic aerial cameras
Gang Li, Ping Jia
To improve the accuracy of image motion measurement for panoramic aerial cameras, the paper proposed a method of real-time image motion measurement based on 2D spatial correlation. An auxiliary area CCD is positioned paralleled to the main linear TDI CCD in the focal plane of the camera. For every frame of the image sequence taken by the auxiliary CCD, a prediction on the displacement of the current image in the flight direction is made based on the forward image motion velocity. The current and the reference images are combined together for 2D-correlation, which products an image motion vector. By decomposing the vector, both the forward and pendulum-swing image motions can be determined. The demanding computational requirements for the real-time 2D-correlation are covered by a joint transform optical correlator. Simulation test results show that the accuracy is improved and the measurement error is within 0.2 pixels for input images with SNR=1 dB.
Research on anti-blooming driving timing for CCD video camera
Site Mo, Qi Liu
How CCD camera causes vertical blooming was investigated. The technique based on vertical driving timing, which can clear vertical blooming up the high-intensity pixels, was presented. The saturated charge of photo diode, which is produced by high-intensity-pixel during the exposure time of a line, enters the vertical shift register. On the control of CCD vertical driving timing, all pixels of the same column add the saturation charge, and then the image has vertical blooming. The vertical blooming up the high-intensity-pixel is produced by the saturation charge of the last frame. Depended on the control method of charge transfer, a special driving timing, which can transfer the remaining charge, is used for clearing the vertical blooming up the high-intensity-pixel. The driving timing is tested on a CCD demo board of ICX205, and the testing showed that the vertical blooming up the high-intensity-pixel is deleted. This method has been applied to intelligent traffic monitoring.
Adaptive optimization agorithm for CDS control parameters of high-speed CCD
Site Mo, Qi Liu
The signal-to-noise ratio of the charge coupled devices (CCD) output can be improved by the optimization of control parameters of correlated double sampling (CDS), however, the control parameters of CDS of high-speed CCD is difficult to determine from experiments. In this paper, an adaptive algorithm is proposed to adjust the control parameters of CDS. With fixed target and exposure parameters, the CDS control parameters such as the width of reset pulse, the timing of noise sampling and data sampling are tuned. The images on all combination of the CDS control parameters are acquired. The square sum of the Tenengrad function of all pixels on each image is used to evaluate the quality of the image. The combination of the three CDS parameters corresponding to the maximum sum is chosen as the CDS control parameters, and then the signal-to-noise ratio of the CCD out is the best. Finally, the algorithm is implemented in FPGA and the experiments results show that, compared with the best image acquired without adaptive algorithm, the parameters of edge profile improved from 507.4 to 763.8, the parameters of MTF50 improved from 526.5 to 937.8.
Quadruple region extended displaying using mirror image
Kunio Sakamoto, Fumihiro Kanazawa
A liquid crystal display (LCD) recently comes into common use. It is possible for this display unit to provide the same size of displaying area as the image screen on the panel. Thus the conventional display can show only one screen, but it is impossible to enlarge the size of a screen, for example twice. To enlarge the display area, the authors have developed an enlarging method of display area using a mirror. Our extension method enables the observers to show the virtual image plane and to enlarge a screen area twice. In the developed display unit, we made use of an image separating technique using polarized glasses, a parallax barrier or a lenticular lens screen for 3D imaging. The mirror can generate the virtual image plane and it enlarges a screen area only twice. In this paper, we present a new extension method to enlarge a screen area quadruple.
Glasses-free 3D display system using special grating film with view control effect
Kunio Sakamoto, Yoshifumi Yatabe
We developed a glasses-free 3D stereoscopic display using an LCD display panel and a special grating film for stereoscopic viewing. The display screen is divided in half in order that left and right regions provide the stereoscopic images for left and right eyes. Because both stereoscopic images are not in the same position, it is difficult for the observer to view the 3D image by the stereoviewing. The grating film can solve this problem because it shifts both left and right images to the same position. Moreover this grating film can give us glassesfree 3D viewing because of its view control effect. As the result, the observer can watch overlapped stereoscopic images for left and right eyes without special glasses such as polarized glasses.
4-views tabletop flat display system for collaborative work on round table
Kunio Sakamoto, Tomoyuki Honda
The authors have researched support system of the reminiscence and life review activity. This support system consists of an interactive tabletop display and interface system. On the reminiscence and life review activity, a therapist puts pictures on the table so as to trigger a talk. However some observers may perceive upside down images if they sit down opposite the therapist. To overcome this problem, we have developed the display system which can be viewed from any direction. In this paper, we propose a 4-views tabletop flat display system for cooperative activity on a round table.
Light-weight monocular display unit for 3D display using polypyrrole film actuator
Kunio Sakamoto, Koji Ohmori
The human vision system has visual functions for viewing 3D images with a correct depth. These functions are called accommodation, vergence and binocular stereopsis. Most 3D display system utilizes binocular stereopsis. The authors have developed a monocular 3D vision system with accommodation mechanism, which is useful function for perceiving depth. This vision unit needs an image shift optics for generating monocular parallax images. But conventional image shift mechanism is heavy because of its linear actuator system. To improve this problem, we developed a light-weight 3D vision unit for presenting monocular stereoscopic images using a polypyrrole linear actuator.
Optical characteristics of 9, 10-diphenylanthracene nanocrystals fabricated by reprecipitation
Zhaolin Yuan, Junsheng Yu, Wenming Ma, et al.
9,10-Diphenylanthracene (DPA) nanocrystals were prepared using a reprecipitation method. Morphologies and Optical properties of DPA nanocrystals were investigated by a scanning electron microscope (SEM), UV-Visible absorption and fluorescence emission spectra, respectively. The results showed that a large amount of DPA nanocrystals form and have a width of about 300-500 nm, a length of 500 nm, a thickness of a few tens of nanometers. Optical properties of the nanocrystals are obviously different from those of DPA monomer. All absorption peaks for DPA nanocrystals experience a bathochromic shift with respect to those of DPA monomer due to the formation of J-aggregates in the nanocrystals. The emission peaks of DPA nanocrystals are red-shifted compared with those of the diluted solution, which are attributed to the intermolecular force difference between the monomer and nanocrystals. In addition, the mechanisms of nanocrystals formation were also analyzed and discussed in detail.
Stereo matching based on SIFT descriptor with illumination and camera invariance
Haitao Niu, Xunjie Zhao, Chengjin Li, et al.
Stereo matching is the process of finding corresponding points in two or more images. The description of interest points is a critical aspect of point correspondence which is vital in stereo matching. SIFT descriptor has been proven to be better on the distinctiveness and robustness than other local descriptors. However, SIFT descriptor does not involve color information of feature point which provides powerfully distinguishable feature in matching tasks. Furthermore, in a real scene, image color are affected by various geometric and radiometric factors,such as gamma correction and exposure. These situations are very common in stereo images. For this reason, the color recorded by a camera is not a reliable cue, and the color consistency assumption is no longer valid between stereo images in real scenes. Hence the performance of other SIFT-based stereo matching algorithms can be severely degraded under the radiometric variations. In this paper, we present a new improved SIFT stereo matching algorithms that is invariant to various radiometric variations between left and right images. Unlike other improved SIFT stereo matching algorithms, we explicitly employ the color formation model with the parameters of lighting geometry, illuminant color and camera gamma in SIFT descriptor. Firstly, we transform the input color images to log-chromaticity color space, thus a linear relationship can be established. Then, we use a log-polar histogram to build three color invariance components for SIFT descriptor. So that our improved SIFT descriptor is invariant to lighting geometry, illuminant color and camera gamma changes between left and right images. Then we can match feature points between two images and use SIFT descriptor Euclidean distance as a geometric measure in our data sets to make it further accurate and robust. Experimental results show that our method is superior to other SIFT-based algorithms including conventional stereo matching algorithms under various radiometric changes.
Studies on the lateral emission of erbium-doped fiber amplifiers
Debao Zhang, Setsuhisa Tanabe
The spectral power distribution of side emission from erbium-doped fibers lateral was measured by an integrating sphere and was evaluated quantitatively. The power of side upconversion is very low and the evidence of the contribution of signal laser to the upconversion is observed. The side spontaneous emission power was much larger than ASE power and nearly saturated at the lower pump power. With increasing Er3+ ions concentration, the contribution of signal laser to the green upconversion decreases and the side spontaneous emission are almost same under the strong 100mW pumping. According to the side emission and scattering power and the end output power, the energy budget is tabulated.
Recursive SAM-based band selection for hyperspectral anomaly detection
Yuanlei He, Daizhi Liu, Shihua Yi
Band selection has been widely used in hyperspectral image processing for dimension reduction. In this paper, a recursive SAM-based band selection (RSAM-BBS) method is proposed. Once two initial bands are given, RSAM-BBS is performed in a sequential manner, and at each step the band that can best describe the spectral separation of two hyperspectral signatures is added to the bands already selected until the spectral angle reaches its maximum. In order to demonstrate the utility of the proposed band selection method, an anomaly detection algorithm is developed, which first extracts the anomalous target spectrum from the original image using automatic target detection and classification algorithm (ATDCA), followed by maximum spectral screening (MSS) to estimate the background average spectrum, then implements RSAM-BBS to select bands that participate in the subsequent adaptive cosine estimator (ACE) target detection. As shown in the experimental result on the AVIRIS dataset, less than five bands selected by the RSAM-BBS can achieve comparable detection performance using the full bands.
Threat assessment of aerial target in ultra-wide field of view infrared image
Yulong Zhou, Mingqiang Xing, Yongzhong Wang
When the target is several miles away from the ultra-wide field of view (UWFV) infrared warning system, it will be a point target in the infrared image, so there is no the target information of distance, geometry and texture without which it is hard to assess the threat of target accurately. It is very important for the air defense command and decision making to have a correct threat assessment of the aerial target, and at present there are few reports about the aerial target threat assessment of the UWFV infrared warning system. The characteristic of the UWFV infrared image is analyzed. A laser range finder is used to measure the initial distance of each target which will be sent back to the infrared warning system. Together with the target information of initial distance, gray value, course angle and angular altitude, considering the nonlinear characteristic of aerial target threat assessment, the threat assessment method based on RBF neural network is presented for its good self-adaptive and self study ability to solve nonlinear complex problems. After simulation experiment, it is found that this method is available and effective.
The research of Organophosphorus pesticide biosensor characteristic
Yong Peng, Xixian Luo, Yi Cheng
To study the fiber-sensor film applied in detecting Organophosphorus pesticide, methyltriethoxysilane was used as precursor, which was doped by FITC- AchE. Consequently, the excellent Acetylcholinesterase biology sensitivity film was prepared. Physics characteristic of the film and sensitivity of Organophosphorus pesticide were researched. In organophosphorus pesticide residue testing, the experimental results indicated that the linear measurement range could reach 10-7~10-6 mol/L, moreover the detection limit is 10-8 mol/L. The sensor could be applied in biological / chemical research, clinical medicine, environmental protection, food inspection, biochemical preventive war field and so on.
Bad pixel replacement based on spatial statistics for IR sensor
Xiang-long Meng, Wei Zhang, Ming-yu Cong, et al.
IR focal plane arrays typically contain bad pixels. Bad pixels have to be corrected because those can significantly impair the performance of target-detection algorithms. On the other hand, particularly as an aid to visual interpretation, it is desirable to replace the bad pixels. IR image contains spatial information and is correlative in spatial domain. In spatial statistics the semivariogram is an important function that relates semivariance to sampling lag. This function can characterize the spatial dependence of each point on its neighbor and provide a concise and unbiased description of the scale and pattern of spatial variability. One of the main reasons for deriving semivariogram is to use it in the process of estimation. Kriging is an interpolation and estimation technique that considers both the distance and the degree of variation between known data points when estimating values in unknown areas. In this paper a new technique based on spatial statistics is developed for bad pixel replacement. The main objective of the technique is to replace bad pixels through Kriging estimation. Theory analysis and experiments show that the method is reasonable and efficient.
Scanning capacitance microscopy characterization on diffused p-n junctions of InGaAs/InP infrared detectors
Hao Yin, Yongfu Li, Wenjuan Wang, et al.
The p-n junctions in planar detectors are usually formed by diffusion of p-type impurity, and the effect of diffusion is crucial for device performance. This work reports the investigation of cross-sectional scanning capacitance microscopy (SCM) on the p-type diffusion in device structures of planar InGaAs/InP infrared detectors. Compare to other methods, SCM can provide 2-dimensional carrier distribution mapping with nanometer resolution, thus it meets the requirement of the measurement on micrometer sized photosensitive elements. This work covers two types of InGaAs/InP device structures: i.e. the avalanche photodiodes (APD) and the PIN near-infrared detectors. For APD structures, we obtain the 2-dimensional carrier distribution and vertical p-type depth under 3 diffusion conditions. For PIN near-infrared detectors, the SCM image provides the diffused p-n junction both on the vertical and lateral direction. A stronger lateral diffusion around the InGaAs/InP heterojunction is observed, which indicates the influence of InGaAs/InP boundary on the vertical diffusion. And the junction region can be detected distinctly from the SCM profile, exhibiting the nanometer scale resolution. Finally, the ratio of lateral to vertical Zn diffusion distance in InP is acquired as 0.67. Our results demonstrate the distinctive capability of SCM investigation on semiconductor optoelectronic device structures.
Measuring of spectral BRDF using fiber optic spectrometer
Wei Zhang, Fugang Wang
We designed a new spectral bidirectional reflection distribution function (BRDF) measurement instrument, which can be utilized to measure isotropic materials simply in laboratory. The measurement instrument consists of a fiber optic spectrometer, a three-dimensional turntable, a halogen light source and a computer. The spectrometer acquires 696 samples in visible band. The angular range controlled by three-dimensional turntable is 0~330° and 0~80° for azimuth angle and zenith angle respectively. The halogen light source supplies a continuous spectrum with high efficiency and stability in the wavelength range from 360~1500 nm. The spectrometer and the three-dimensional turntable connect with the computer. The angle rotation and data acquisition are all controlled by the computer. The spectral BRDF measurement of three materials is conducted. The relation of spectral BRDF, wavelength and reflected zenith angle is presented. In conclusion, the designed spectral BRDF measurement system can acquire spectral BRDF data quickly and accurately, thus it is an efficient way to measure material spectral reflected properties which is need for computer rendering, target identification.
The study on organic solar cells based on bathocuproine as an exciton blocking layer
Feng Liu, Jian Zhong, Junsheng Yu, et al.
Using a buffer layer between C60 and cathode was an important and popular approach to improve the performance of organic photovoltaic cells. In this work, we chose CuPc (Copper(II) phthalocyanine) as an electron donor material, C60 (fullerene) as an electron acceptor material and BCP (Bathocuproine) as an exciton blocking layer to fabricate an organic solar cells with a structure of ITO/CuPc/C60/BCP/Ag, and studied the relationship between the photoelectric properties of organic solar cells and the film thickness of BCP. The results showed that the power conversion efficiency (PCE) was closely related to the thickness of exciton blocking layer. With the increasing of BCP film thickness, the power conversion efficiency of the device increased first and then decreased. When the thickness was 0 nm, the power conversion efficiency (PCE) was 0.357 %. When the film thickness was 25 nm, the PCE was 1.013 %. And when the thickness was 50 nm, the PCE was 0.43 %. However, when the thickness was 100 nm, the PCE was 0 %.We presumed that the exciton blocking layer reduce the quenching rate at the interface between organic layer and cathode so that exciton can be separated into electrons and holes more effectively. As a result, the PCE increased. At the same time, if the film of BCP layer thickness is too thick, PCE would sharply decrease due to high resistance during collecting charge carriers.
The growth of cubic boron nitride films on the interlayer of nickel by RF sputter
Qingxiu Guo, Jinxiang Deng, Weiping Zhao
In this paper, the buffer interlayer was formed by first depositing a pure nickel layer on the p-type Si (100) substrate, and then the boron nitride thin films were deposited by using radio frequency magnetron sputter. We used the purity of 99.99 % nickel and purity of 99.99 % boron nitride (h-BN) as targets in the experiment. Step profiler has been employed to measure the thickness of nickel interlayer and cubic boron nitride thin films. Fourier transformed infrared spectroscopy (FTIR) has been employed to characterize boron nitride thin films. The content of cubic phase boron nitride in the films has been calculated through the FTIR spectra. The surface morphology and the grain size of films were examined using an atomic force microscope (AFM). The mixture gas of argon and nitrogen was as the working gas in our experiment. To study the thickness of nickel interlayer how to influence the formation of cubic phase in the boron nitride thin film, we changed the thickness of nickel interlayer by controlling the sputtering time with the same substrate temperature, working gas pressure and other conditions. The results showed that the thickness of nickel interlayer is the key factor in the formation of cubic boron nitride. The growth of cubic boron nitride at room temperature can be realized by appropriately selecting the thickness of nickel interlayer. We also drew out when the thickness of nickel interlayer was about 150nm, the content of cubic phase in boron nitride thin films would get up to the highest. On this basis of these results, we also examined impacts of the substrate temperature (100~400 °C), substrate bias (50~210 V) and annealing conditions on the formation of the cubic boron nitride thin films.
Detection performance of laser range-gated imaging system
Jun Xu, Xiaofeng Li, Jijun Luo, et al.
Laser radar is rapidly developing towards very capable sensors for number of applications such as military sensing and guidance, auto collision avoidance, robotic vision and atmospheric sensing. In this paper, the detection performance of non-scanned Laser Rang-gated (LRG) imaging system is studied. In order to compute the detection range of laser active imaging system, the range equation is derived by using laser illuminating model and considering factors which affect system imaging quality. According to the principle of laser radar and the characters of objects and the detectors in special applied setting, it mainly deduced the non-scanned laser radar range equation of the range-gated system, meanwhile, the SNR model of non-scanned LRG imaging system is set up. Then, relationship of the detection probability, the false alarm probability and the signal-to-noise ratio in the non-scanned LRG imaging system are analyzed, the influence factors of system's performance are pointed out, and the solution is proposed. The detection performance simulation software of non-scanned LRG imaging system is designed with MATLAB and the performance of the imaging system is simulated.
In-situ self-assembled polyaniline/carbon nanotubes nanofiber thin films for ammonia gas sensors
Huiling Tai, Yadong Jiang, Guangzhong Xie
Polyaniline/carbon nanotubes (PANI/CNTs) nanocomposite thin films were fabricated through an in-situ self-assembled method on the interdigitated electrodes for ammonia (NH3) gas sensors. CNTs presented in this work consisted of singlewalled CNTs (SWNT) and multi-walled CNTs (MWNT). The pure MWNT dispersed in N,N-Dimethyl Formamide (DMF) solution was also dipped on the interdigitated electrodes for gas-sensing property comparison. The SEM images showed clearly that PANI/CNTs nanocomposite thin films possess a nanofiber mesh like structure, and TEM analysis exhibited that the diameter of the pure MWNT was 10 nm whereas that of the PANI/MWNT nanofiber was about 50 nm, which confirmed a PANI layer packed on the surface of MWNT during the in-situ polymerization process. The gasresponse of different sensing films to NH3 was investigated at room temperature. It was found that PANI/MWNT nanocomposite thin film exhibited the higher sensitivity than pure MWNT film and PANI/SWNT thin film, which might be ascribed to more active sites for gas adsorption for the PANI/MWNT nanocomposite thin film. The response-recovery property was studied when the PANI/MWNT thin film sensor was exposed to different concentrations of NH3 ranging from 23 to 141 ppm, and it was found that the sensitivity was linear to the concentrations of NH3. This sensor also had good reproducibility and selectivity.
9.3 X continuous zoom optical system with finite conjugate distance
Yiyu Li, Yuanyuan Wang, Dexi Zhu, et al.
A continuous zoom optical system with finite conjugate distance was designed for low-vision aid device. The configuration of the zoom optical system and the evaluation of the optical performance including modulation transfer function(MTF) and diffuse spot in diameter were investigated. The stability of the system performance was forecast by using the tolerance sensitivity analysis and Monte Carlo method. This mechanically compensated zoom lens combines four group components including a fixed objective, moving variator and compensator, and a fixed eyepiece with a total of 10 pieces of lens. The optical system which has a tube length of 76 mm and a front intercept distance of 262 mm can realize continuous zoom from 8.8~ 52 mm and 9.3 X zoom ratio without any image vignetting or obvious fluctuation in image quality.
Optical tracking method based on geometric feature point of the extended target
Zhihua Fan, Chunhong Wang, Changhui Rao, et al.
Optical tracking systems need to measure the shift of target in real time so as to compensate the shift effect. For extended target, template matching techniques are usually used to estimate the image shift, in which the shift can be computed up to subpixel with the parabolic interpolation. In this paper, we propose a new method to estimate the shift accurately building on geometric feature point tracking. The method first extracts feature points from the reference image using Harris detector, and tracks the same feature point by correlating the small patch around it with that of each point detected in other images. The subpixel feature point position utilized to estimate the image shift is then determined by the modified Harris strength of the pixels around that point. Experimental results validates that the proposed method can accurately measure image shifts over large distance under noisy conditions, and that the mean of estimate error is less than 0.03 pixels. Moreover, the contrast of long exposure images before and after shift compensation is compared to evaluate our algorithm in the optical tracking system.
Adaptive NUC algorithm for uncooled IRFPA based on neural networks
Ziji Liu, Yadong Jiang, Jian Lv, et al.
With developments in uncooled infrared plane array (UFPA) technology, many new advanced uncooled infrared sensors are used in defensive weapons, scientific research, industry and commercial applications. A major difference in imaging techniques between infrared IRFPA imaging system and a visible CCD camera is that, IRFPA need nonuniformity correction and dead pixel compensation, we usually called it infrared image pre-processing. Two-point or multi-point correction algorithms based on calibration commonly used may correct the non-uniformity of IRFPAs, but they are limited by pixel linearity and instability. Therefore, adaptive non-uniformity correction techniques are developed. Two of these adaptive non-uniformity correction algorithms are mostly discussed, one is based on temporal high-pass filter, and another is based on neural network. In this paper, a new NUC algorithm based on improved neural networks is introduced, and involves the compare result between improved neural networks and other adaptive correction techniques. A lot of different will discussed in different angle, like correction effects, calculation efficiency, hardware implementation and so on. According to the result and discussion, it could be concluding that the adaptive algorithm offers improved performance compared to traditional calibration mode techniques. This new algorithm not only provides better sensitivity, but also increases the system dynamic range. As the sensor application expended, it will be very useful in future infrared imaging systems.
Research of image enhancement of dental cast based on wavelet transformation
Jing Zhao, Zhongke Li
This paper describes a 3D laser scanner for dental cast that realize non-contact deepness measuring. The scanner and the control PC make up of a 3D scan system, accomplish the real time digital of dental cast. Owing to the complexity shape of the dental cast and the random nature of scanned points, the detected feature curves are generally not smooth or not accurate enough for subsequent application. The purpose of this p is to present an algorithm for enhancing the useful points and eliminating the noises. So an image enhancement algorithm based on wavelet transform and fuzzy set theory is presented. Firstly, the multi-scale wavelet transform is adopted to decompose the input image, which extracts the characteristic of multi-scale of the image. Secondly, wavelet threshold is used for image de-noising, and then the traditional fuzzy set theory is improved and applied to enhance the low frequency wavelet coefficients and the high frequency wavelet coefficients of different directions of each scale. Finally, the inverse wavelet transform is applied to synthesis image. A group of experimental results demonstrate that the proposed algorithm is effective for the dental cast image de-noising and enhancement, the edge of the enhanced image is distinct which is good for the subsequent image processing.
Luminescent properties of Tb(acac)2AA nanorods prepared by ultrasound irradiation
Le Zhou, Hongquan Yu, Haijun Guo
Rare earth organic complexes possess characteristic luminescent properties, such as extremely sharp emission bands, long lifetime and potential high internal quantum efficiency. The corresponding nano-materials have attracted extensive attention recently owing to the potential application for OLED and photovoltaic devices. In this report, ternary complex of rare earth Tb(acac)2AA (acac= acetyl acetone, AA= acrylic acid ) uniform nanorods have been prepared by sonication. The properties of Tb(acac)2AA nanorods were characterized by X-ray diffraction (XRD), Fourier transform Infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). It is interesting to observe that the nanoparticles with diameter of 300 nm are growing into the nanorods with size of 80×1200 nm (W×L) with the increasing of the power output. It can be explained that the cavitation effect was increased with the increasing power output and thus accelerated the growth of nanorods from nanometer-sized seed on the Tb(acac)2AA nanoparticles. Furthermore, the size of the nanorods is much smaller than that of the bulk prepared by precipitation. The luminescent properties of Tb(acac)2AA nanorods were studied in comparison with that of the bulk. The results indicated that the line shapes of corresponding luminescent spectras are similar, but the luminescent intensity of the nanorods is two times stronger than that of the bulk. It means that the nanorods have higher fluorescence quantum efficiency than the bulk. In addition, the fluorescence lifetime of the nanorods is obviously longer. In summary, sonication is an effective approach to prepare rare earth nanomaterial with high luminescence efficiency.
Three-dimensional location of tomato based on binocular stereo vision for tomato harvesting robot
Rong Xiang, Yibin Ying, Huanyu Jiang, et al.
Accurate harvesting depends on the order of the accuracy of 3D location for harvesting robot. The precision of location is lower when the distance between fruit and camera is larger than 0.8 m for the method based on binocular stereo vision. This is a big problem. In order to improve the precision of depth measurement for ripe tomato, two stereo matching methods were analyzed comparatively which were centroid-based matching and area-based matching. Their performances in depth measurement were also compared. Experiments showed that the relationship between distance and measurement was linear. Then, models of unitary linear regression (ULR) were used to improve the results of depth measurement. After correction by these models, the depth errors were in a range of -28 mm to 25 mm for centroid-based matching method and -8 mm to 15 mm for area-based matching method at a distance of 0.6 m to 1.15 m. It can be concluded that costs of computation can be decreased with the promise of good precision when the parallax of centroid which is acquired through centroid-based matching method is used to set the range of parallax for area-based matching method.
Development of the tongue coating analyzer based on concave grating monochrometer and virtual instrument
Zhong Ren, Guodong Liu, Lvming Zeng, et al.
The tongue coating diagnosis is an important part in tongue diagnosis of traditional Chinese medicine (TCM).The change of the thickness and color of the tongue coating can reflect the pathological state for the patient. By observing the tongue coating, a Chinese doctor can determine the nature or severity of disease. Because some limitations existed in the tongue diagnosis method of TCM and the method based on the digital image processing, a novel tongue coating analyzer(TCA) based on the concave grating monochrometer and virtual instrument is developed in this paper. This analyzer consists of the light source system, check cavity, optical fiber probe, concave grating monochrometer, spectrum detector system based on CCD and data acquisition (DAQ) card, signal processing circuit system, computer and data analysis software based on LabVIEW, etc. Experimental results show that the novel TCA's spectral range can reach 300-1000 nm, its wavelength resolution can reach 1nm, and this TCA uses the back-split-light technology and multi-channel parallel analysis. Compared with the TCA based on the image processing technology, this TCA has many advantages, such as, compact volume, simpler algorithm, faster processing speed, higher accuracy, cheaper cost and real-time handle data and display the result, etc. Therefore, it has the greatly potential values in the fields of the tongue coating diagnosis for TCM.
Infrared activity of crystalline silicon and amorphous silicon
Shuang Liu, Wei Chen, Jianing Zhang, et al.
The thermo-resistance effect in silicon has been exploited for the fabrication of uncooled infrared detectors. In this paper, based on the Schrodinger equation of material radiation system and the micro-structure of silicon, the infrared absorption theory of silicon is analyzed. The results show that the infrared activity of amorphous silicon is more activate than crystalline silicon because of the fault and long range disorder, and using the impurity B, Li, and H, the infrared activity of silicon also will be activated.
Si (211) substrate thinning technology for HgCdTe focal plane arrays on Si substrates
Shan Zhang, Chenfei Wang, Juying Cao, et al.
A wet chemical etching method for (211)Si substrates was demonstrated in this paper. The morphologies and cleanness of (211) Si surface etched in different mixture ratio HF-HNO3-HAC solutions have been studied by using optical microscope and the surface profile measuring system (SPMS). The analysis of the surface images indicated that the Si etched by the HF-HNO3-HAC (2:15:5) has the smoother surface, and the wet chemical etching can effectively eliminate the damage introduced by the chemo-mechanical polishing. An auto wet chemical etching agitator which can move in the vertical orientation was used. The wet chemical etching rate of (211) Si was obtained in the room temperature and the transmitted spectra of (211) Si with different thickness were measured by Fourier Transform Infrared Spectroscopy (FTIR) and compared. It is confirmed that the Si with different thickness make no difference to the spectral response in mid-wave. By using this novel technology, the Si substrate of HgCdTe/Si detector was removed completely with the HF-HNO3- HAC (2:15:5) solution. It is obvious that the wet chemical etching method can remove the (211) Si substrates with no damage and detector can work better.
Research on testing field flaws of image intensifier based on spatio-temporal SNR
Bin Zhou, Bingqi Liu, Dongsheng Wu
Image intensifier is the kernel of low-light-level device. The field flaw is one of the important index parameters of the image intensifier. Traditionally the statistic number of the image intensifier's field flaws is calculated through the people's eyes by the aid of an optical microscope, which main limitation is subjective and inefficient. With the broad application of the high-powered CCD and digital imaging processing method in testing performance of image intensifier, the method of appraising SNR based on spatio-temporal noise theory can accurately reflect the spatio-temporal heterogeneous of fluorescence's output image and fulfill the requirements of digital and automatic test. The limitation of the flaws' shape and position can be disregard and the accurate flaws' inspection can be realized rapidly by this method. In this paper, the main factors of forming the field flaws are analyzed and the mathematic model of spatio-temporal SNR is deduced. The hardware devices of the test system for image intensifier's spatio-temporal SNR are discussed. The spatio-temporal SNR of Gen image intensifier is tested by this test system and the test software based on Visual C++ and Matlab. The digital and automatic test of a factitious field flaw is realized by the theory of spatio-temporal SNR. The test precision can achieve pixel level. The experimental results show that this new method is rational, reliable and visualized.
Multi-object spectral imaging based on MEMS
Yuheng Chen, Yiqun Ji, Jiankang Zhou, et al.
The primary compact high resolution imaging spectrometer was developed and reported. Due to its numerous wave bands the original image data is always in a huge scale and costs a tremendous process overhead, but the data amount of the region of interest is as a rule in the order of thousandth, if not less, of that of the whole push-broom region. With a digital micromirror device (DMD), only the region of interesting object is imaged by the imaging spectrometer, which results in a distinct reduction of data quantity and a high data compression ratio. A DMD of high turning rate and residential time adjustability is used as a spatial light modulator to fulfill the object selection function. It is placed after the fore objective and able to reflect the object to either the panchromatic CCD camera channel or the imaging spectrometer channel. The position of the object can be firstly determined through the image interpretation from panchromatic imaging channel and a DMD control command is executed to switch the corresponding mirrors to the imaging spectrometer channel, thus only the object region of interest is imaged by the spectrometer. The multiple objects of both printed patterns and real leaves are accurately determined and selected according to their different locality and shape features. The panchromatic and hyperspectral image data are both collected for further effective object recognition.
A white organic light-emitting diode based on anthracene-triphenylamine derivatives
Quan Jiang, Jianjun Qu, Junsheng Yu, et al.
White organic lighting-diode (WOLED) can be used as flat light sources, backlights for liquid crystal displays and full color displays. Recently, a research mainstream of white OLED is to develop the novel materials and optimize the structure of devices. In this work a WOLED with a structure of ITO/NPB/PAA/Alq3: x% rubrene/Alq3/Mg: Ag, was fabricated. The device has two light-emitting layers. NPB is used as a hole transport layer, PAA as a blue emitting layer, Alq3: rubrene host-guest system as a yellow emitting layer, and Alq3 close to the cathode as an electron transport layer. In the experiment, the doping concentration of rubrene was optimized. WOLED 1 with 4% rubrene achieved a maximum luminous efficiency of 1.80 lm/W, a maximum luminance of 3926 cd/m2 and CIE coordinates of (0.374, 0.341) .WOLED 2 with 2% rubrene achieved a maximum luminous efficiency of 0.65 lm/W, a maximum luminance of 7495cd/m2 and CIE coordinates of (0.365,0.365).
A novel spectrum measurement system
Qiang Qi, Quan Jiang
A novel spectrum measuring system, which was based on the embedded system of ARM, controlled by a PC was developed. The system is composed of a monochromator, a high-precision voltage amplifier, an ARM7 system and a PC. The monochromator convert optical signal into electronic signal, and the signal is then amplified by the voltage amplifier. Then the amplified signal is converted to digital signal by the ARM7 system. At the end, the digital is send to the PC by the USB interface. After the processing and analyzing of the data, PC can measure and display the spectrum of the light source real-time. The system can measure the spectrum and chromaticity coordinates of light source and display device with high precision, and has a friendly interface.
Method for laser disturbing image quality evaluation based on wavelet weight and correlation
Yin Xu, Xiao-quan Sun, Zuo-lai Wang
The advantages and disadvantages of conventional image quality evaluation methods are analyzed and according to the characteristics of laser disturbing image, an image quality evaluation method which is based on wavelet weight and correlation is established. In the method, both the original and disturbed images are processed by wavelet decomposition, replacement and reconstruction. Then different sub-band images are obtained and their correlations are calculated. Combined with band-pass characteristic of human vision, visual weighted coefficients are obtained and objective calculation results are output finally. Experimental results show that this method not only can overcome the influences of different conditions on evaluation of laser disturbing effect, but it is also in good agreement with the subjective method.
Structure design and performance analysis of the CsI(Tl) thin film crystal cell
Shuang Liu, Wan Zhou, Yapei Yang, et al.
In this paper, we design a structure of CsI(Tl) thin film crystal cell, and cover the CsI(Tl) thin film on the surface of the CCD directly. In order to prevent the photons emit from the surface of film, which result in depressing the fluorescence efficient, we cover the film with alumina to form reflective layer. Al layer is used to separate the CsI(Tl) crystal according to the size of CCD photosensitive cell, which solve problem that fluorescence cross talk between the different photosensitive cell. The fluorescence transmission efficiency of CsI(Tl) film crystal cell model is also researched , the results show the fluorescence transmission efficiency is maximum when the thickness of film is 40 μm.
The analysis of the interference hyperspectral image features and compression
Lei Zhang, ShanCong Zhang, Xiangli Bin, et al.
Interference hyper spectral image and the images contain some interference information which are collected by the LASIS are only middle results of the spectrometer, is a three-dimensional image. The amount of the data is large size, and need to be compressed. For testing the actual interference hyper spectral image, use different composed way, to compose of LAMIS and LADIS image, the LASIS image has different target with different spectral band, LAMIS has the same target with different spectrum, LADIS has the same spectrum with different target . The spatial correlation and spectral correlation are analyzed. The self-coefficient and cross-coefficient are also calculated. The method that LASIS extract into LADIS is proposed, which separate interference information form spatial image, and it is a new foundation for interference information protection of LASIS image. The feather of LASIS image is revealed, the results obtained can be use LASIS image processing and compressing.
The manufacture of a binary optic liquid crystal blazed grating and its electro-optical properties
Kun Liu, Ziqiang Huang, Jimin Wang, et al.
A photoresist film was applied on the indium tin oxide (ITO) conductive glass which was coated with silver. The photoinduced changes of the photoresist film were achieved by exposure to UV lamp through a grating & lead pattern photomask. The photoresist film exhibited grating lines and lead patterns after development. The Ag-ITO double film coated with photoresist patterns was etched to double-layer electrode patterns by ion beam. After photoresists were stripped, silver grating electrodes were removed and ITO grating electrodes were coated with polyimide (PI) and treated by rubbing. The orientation was perpendicular to grating. The back electrode was a piece of ITO glass which was oriented by the same method. Nematic liquid crystal (LC) was injected into the grating cell. Other silver-leads were retained and connected with driver ICs and flex circuits. The binary optic liquid crystal blazed grating was fabricated. Step-shaped phase was obtained by applying a step-shaped voltage on LC grating electrodes. It formed blazed grating at one order and the diffraction angle can be shifted dynamically. The sample was checked up by the optical microscope and the He-Ne laser. The results indicate that the sample had clear grating structure and every grating electrode can be controlled separately. The range of the first order of diffraction angle was ±6° in theory. The diffraction efficiency decreased as the diffraction angle increased, and the maximum diffraction efficiency can exceed 80 %.
Acidic chemical bath deposition of Cd1-xZnxS thin films
Meng Cao, Yan Sun, Jie Wu, et al.
Cd1-xZnxS ternary material has a wider band gap than CdS which makes it a better window material for use in CdTe solar cells. Typical chemical bath deposition (CBD) processes for sulfides employ an alkaline medium containing the chalcogenide source and the metal ion. In this work, Cd1-xZnxS thin films have been deposited from acidic solution. The composition, surface morphology and structural properties of the as-deposited and annealed Cd1-xZnxS thin films were studied using energy dispersive X-ray analysis (EDX), scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The band gap of the as-deposited Cd1-xZnxS thin films varied from 2.38 to 2.44 eV, whereas in the annealed films varied from 2.36 to 2.42 eV. The decreased band gaps of the Cd1-xZnxS thin films were due to the improved crystalline nature of the material.
Custom aspherical ophthalmic lens design
Chuan Hu, Yiyu Li, Yuanyuan Wang, et al.
The Liou's model eye is close to anatomical, biometric and optical realities, and is effective in predicting the optical performance. An efficient approach for designing of ophthalmic lenses by regarding ophthalmic lens and Liou's model eye as a single optical system, based on optimization of aspherical surface coefficients is presented. The wavefront aberration and diopter are taken into consideration, the traditional damped least-squares methods are chosen with the high order aspherical equations being used. The appearance of the lens designed is improved obviously than the spherical ones and the fabricating is not complicated; the optical performances are controlled in an acceptable range. With the help of the structure parameters of a single eye ball obtained, custom-design ophthalmic lens is workable which might be a direction of lens design in the future.
Fabrication and characterization of photo cathode materials for transparent organic light-emitting diodes
Hui Lin, Junsheng Yu, Nana Wang, et al.
In this work structural composition and fabrication process of cathode for transparent OLED were investigated. Using a LiF/Al/Ag/Alq3 semitransparent cathode and a Mg:Ag/ITO cathode, green fluorescent transparent organic light-emitting devices (TOLEDs) were fabricated. ITO was evaporated as a cathode onto a thin Mg:Ag layer by DC magnetron sputtering method with the assistance of tiny H2O vapor during deposition process. The fabrication of LiF/Al/Ag/Alq3 electrode was processed without breaking the vacuum. At a bias of 15 V, the luminance of the TOLED with Mg:Ag/ITO and LiF/Al/Ag/Alq3 cathode were 3016 and 4535 cd/m2, respectively. The results indicate that LiF/Al/Ag/Alq3 electrode can be used as an effective and stable cathode in TOLEDs.
Full parallax 3D stereoscopic display
Kunio Sakamoto, Masahiro Nishiguchi
The conventional display can show only one screen, but it is impossible to enlarge the size of a screen, for example twice. A mirror makes another world in the silver coated glass. The authors have ever presented an enlarging method of display area using a mirror. Our extension method enables the observers to show the virtual image plane and to enlarge a screen area twice. To provide twice enlarged region, the surface of a visual display needs to produce dual views. Although the displaying region is doubled, this virtual display could not produce 3D images. To solve this problem, we must prepare to generate four views; side by side observing view windows enable us to perceive stereoscopic 3D images and a vertical neighbor viewing window makes dual views for enlarging display area. In this paper, we propose a 3D imaging display with horizontal and vertical parallaxes using an angle-controlled unidirectional 4-views display.
Research on vision control system for inverted pendulum
Xiaolin Jin, Yongming Bian, Jia Jiang, et al.
This paper focuses on the study and experiment of vision control system for an inverted pendulum. To solve some key technical problems, the hardware platform and the software flow of the control system have been designed. The whole control system is composed of vision module and motion control module. The vision module is based on "CCD camera", the motion control module is based on "Motion Control Card, Servo Driver and Servo Motor", and the software is based on LabView. The main research contents and contributions of this paper are summarized as follows: (1) Analyze the functional requirements of the vision control system about the inverted pendulum, developing the hardware platform and planning the overall arrangement of the system; (2) Design the image processing flow and the recognition track process of the moving objects. The accurate position of the pendulum can be obtained from the image through the flow, which concludes image pretreatment, image segmentation and image post-processing; (3) Design the software structure of the control system and write the program code. It is convenient to update and maintain the control software due to the modularity of the system. Some key technical problems in the software have been solved, so the flexibility and reliability of the control system are improved; (4) Build the experimental platform and set the key parameters of the vision control system through experiments. It is proved that the chosen scheme of this paper is feasible. The experiment provides the basis for the development and application of the whole control system.
Novel reflectivity-difference biosensor
Han Chen, Lian Wei, Ying Feng
The traditional immobilized biomolecule detection technique on arrays has been fluorescence, but this has limitations because of its reliance on fluorophores. Alternatively, many label-free detection techniques have been developed such as surface plasmon resonance (SPR), ellipsometry, thin-film interference, diffractometry, and waveguides. These techniques have the advantage of high speed and high sensitivity, but in exchange rely on complicated structures or detailed sensing cells. A novel reflectivity-difference biosensor is introduced in this paper. When the sensor covered with a protein layer, the cells and the land would have opposite changes of the reflectance which lead to intensity shifts at the far-field diffraction plane. Therefore, it is convenient for the operation without intricate sensor structures and multifarious optical systems.
Poling and characterization of a novel organic/polymer electro-optic material
Jinkun Liao, Xianzhong Tang, Rongguo Lu, et al.
Electro-optic organic/polymer material is important for the fabrication of polymer integrated optic-electronic devices and organic sensors. Recently, a novel organic high μβ value chromophore FFC have been synthesized by molecular design. The absorption spectrum in 400-4000 cm-1 is measured for the material, and the measurement result shows that the absorption loss is negligibly small. An organic/polymer high electro-optic activity material FFC/PSU is obtained by dissolving guest FFC (wt. 20%) and a host polysulfone (PSU) in a solvent. The resolvability of cyclohexanone for the material is satisfactory by comparison with other solvents experimentally, and the preparation of FFC/PSU thin film is ease relatively. The materiel is poled by electric field-assisted contact poling, and the near optimum poling condition is determined by adjusting poling parameters as pre-curing duration, poling temperature and poling voltage etc. The electro-optic coefficient of the material is measured as high as 130pm/V by using the widely accepted simple reflection technique. The investigation indicates that the FFC/PSU has excellent characteristics, such as high electro-optic coefficient, low absorption loss, good thermal stability and capability for withstanding the subsequent process techniques, suitable for the fabrication of high-performance integrated optic-electronic devices and sensors.
Self-assembly of conducting polymer nanowires as hole injection layer for organic light-emitting diodes applications
Yajie Yang, Yadong Jiang, Jianhua Xu, et al.
We reported a controlled architecture growth of high density and ordered nanowire film of poly(3,4-ethylene dioxythiophene) (PEDOT) via Langmuir-Blodgett (LB) technique, and self-assembly performance of PEDOT nanowires at air/water interface was investigated in detail. The conducting film consisting of high density and ordered nanowires was transferred onto ITO substrate as a hole injection layer for organic light emitting diodes (OLEDs). The results showed that, compared to conventional PEDOT film, the improved performance of OLEDs was obtained after using ordered PEDOT nanowire layer as hole injection layer. It also indicated that compact arrangement and well-ordered structure of conducting channel was attributed to the improvement of OLED performance, leading to the increase of charged carrier mobility in hole injection layer and the recombination rate of electrons and holes in the electroluminescent layer.
Study on the dependence of properties of TiOx heat sensitive films on deposit oxygen flow rate
Jing Jiang, Zhiming Wu, Yonglong Qiu, et al.
In this article, titanium oxide thin films (TiOx) are prepared with the reactive DC sputtering in an oxygen and argon atmosphere. Properties of titanium oxide films could be largely varied by controlling the deposition condition. Here we study on the dependence of sheet resistance, thickness, optical transmittance and film composition of titanium oxide films on different deposit oxygen flow rates.
White light LED based on YAG:Ce3+ and YAG:Ce3+,Gd3+ phosphor
Ke Li, Changyu Shen
YAG:Ce3+ and a yellow-orange phosphor YAG:Ce3+,Gd3+ were prepared by solid-state reaction. Excitation spectrum of YAG:Ce3+ was composed of two bands peaking at 335nm and 460nm. Emission band of YAG:Ce3+ peaking at 532nm corresponds to the 5d-->4f transition of Ce3+.The emission peak wavelength of YAG:Ce3+,Gd3+ shifted to longer wavelength with the increasing of the concentration of Gd3+. White LED was obtained by combining GaN(460nm) chip with different ratios of phosphor YAG:Ce3+ and YAG:Ce3+,Gd3+.As the ratio of YAG:Ce3+,Gd3+ phosphor increased, the color rendering index of the LED improved significantly under the forward bias of 20mA. White LED with color rendering index of 85, CIE chromaticity coordinates of (0.3040, 0.2911), and color temperature Tc of 7615K was obtained as the ratio of YAG:Ce3+ and YAG:Ce3+,Gd3+ was 5:3.
White organic light-emitting diodes based on doped and ultrathin Rubrene layer
Yi Li, Yadong Jiang, Wen Wen, et al.
Based on a yellow fluorescent dye of 5, 6, 11, 12-tetraphenylnaphthacene (Rubrene), WOLEDs were fabricated, with doping structure and ultrathin layer structure utilized in the devices. By doping Rubrene into blue-emitting N,N'-bis-(1- naphthyl)-N,N'-biphenyl-1,1'-biphenyl-4,4'-diamine (NPB), the device with a structure of indium-tin-oxide (ITO)/NPB (40 nm)/NPB:Rubrene (0.25 wt%, 7 nm)/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) (30 nm)/Mg:Ag exhibited a warm white light with Commissions Internationale De L'Eclairage (CIE) coordinates of (0.38, 0.41) at 12 V. The electroluminescent spectrum of the OLED consisted of blue and yellow fluorescent emissions, the intensity of blue emission increased gradually relative to the orange emission with increasing voltage. This is mainly due to the recombination zone shifted towards the anode side as the transmission rate of electrons grows faster than that of holes under higher bias voltage. A maximum luminance of 7300 cd/m2 and a maximum power efficiency of 0.57 lm/W were achieved. Comparatively, by utilizing ultrathin dopant layer, the device with a structure of ITO/NPB (40 nm)/Rubrene (0.3 nm)/NPB (7 nm)/BCP (30 nm)/Mg:Ag achieved a low turn-on voltage of 3 V and a more stable white light. The peaks of EL spectra located at 430 and 560 nm corresponding to the CIE coordinates of (0.32, 0.32) under bias voltage ranging from 5 to 15 V. A maximum luminance of 5630 cd/m2 and a maximum power efficiency of 0.6 lm/W were achieved. The balanced spectra were attributed to the stable confining of charge carriers and exciton by the thin emitting layers. Hence, with simple device structure and fabricating process, the device with ultrathin layer achieved low turn-on voltage, stable white light emitting and higher power efficiency.
Study on lifetime of high brightness green organic light-emitting devices
Zhuo Gao, Jian Zhong, Junsheng Yu, et al.
To analyze why the device degrade, we have processed the pictures, which we got when the device degraded, with Matlab programs. The areas of dark spots in the pictures were calculated quantitatively. And we also got the effective light-emitting area and the proportion of dark spots. Comparing and contrasting the attenuation curve of the lightemitting area and the luminance, we could study further the reasons why the device degraded and know how to improve the operation lifetime of device. In this study, a kind of high brightness green organic light-emitting diode was selected as the research object, with a typical OLED multilayer structure, ITO/CuPc/α-NPD/Alq3:C545T/Alq3/LiF/Al. The device started working required only 2.5 V, with a emitting peak at 525 nm and maximum luminous efficiency 3.92 lm•W-1.The brightness of the device was measured to be 2500 cd•m-2 at the drive voltage 20 V. To restrain the permeation of vapor and oxygen into the device, it was encapsulated in low vacuum and high purity of nitrogen. It was a effective way to protect the device and ensure all kinds of device properties steady. Nevertheless, it's inevitable that vapor and oxygen permeated into the device due to the porosity of epoxy resin. The results showed that vapor and oxygen both would result in the light-emitting area decrease. On the one hand, vapor would peel away the cathode from the organic layer and bring in some bubbles; on the other hand oxygen would cause oxidation of cathode and organic layer. As a result, the dark spots appeared, grew up, and finally attached together forming a non-emitting area.
Different materials as a cathode modification layer on the impact of organic solar cells
Jian Zhong, Qiuyan Huang, Junsheng Yu, et al.
Organic thin film solar cells based on conjugated polymer or small molecules have showed an interesting approach to energy conversion since Tang reported a single donor-accepter hetero-junction solar cell. The power conversion efficiency of organic solar cells has increased steadily over last decade. Small-molecular weight organic double heterojunction donor-acceptor layer organic solar cells (OSC) with a structure of indium-tin-oxide (ITO)/CuPc(200Å)/C60(400Å)/x/Ag(1000Å), using CuPc(copper Phthalocyanine)as donor layer, and Alq3(8-Hydroxyquinoline aluminum salt), BCP(Bromocresol purple sodium salt) and Bphen(4'7-diphyenyl-1,10-phenanthroline) as cathode modification layer, respectively were fabricated. The performance of OSC was studied as a function of the different materials as an cathode modification layer to optimize the structure. The current-voltage characteristic of the solar cell under AM1.5 solar illumination at an intensity of 100 mw/cm2 showed that the power conversion efficiency (PCE) was dependent of the different materials of the cathode modification layer. the efficiency along with the different materials as an cathode modification layer will diminish under that standard solar illumination(AM1.5)was obtained. Using a double heterostructure of ITO/CuPc(200Å)/C60(400Å)/Alq3(60Å)/Ag(1000Å) with high-vacuum evaporation technology, the efficiency was 0.587%.the efficiency was 0.967% when the material of the cathode modification layer was BCP, with the structure of ITO/CuPc(200Å)/C60(400Å)/BCP(35Å)/Ag(1000Å), and the efficiency was 0.742% when the material of the cathode modification layer was Bphen, with the structure of ITO/CuPc(200Å)/C60(400Å)/ Bphen(50Å)/Ag(1000Å).Using different materials as a cathode modification layer, it can be seen that the material which matches the energy level could even eventually be able to improve the energy conversion efficiency more.
Azimuth vertical transference based on magneto-optical modulation
Li-long Tan, Qi-yuan Zhong, Xian-xiang Huang
It is a big problem that it need a large field during the missile azimuth aiming using facing upward method. Aiming to solve the problem, it is actualized that the azimuth transfers along with the plump line. This article describes the principle of vertical transference of the azimuth and the concrete realization of magneto-optical modulation. The scheme use the polarized light as the medium of azimuthal information, and restrain interfere coming from azimuth transfering by magnto-optic modulating the ploarized light. Using the technique of azimuth transfering vertically, the launching field is reduced greatly during the missile azimuth aiming process.
Growth of ZnO nanoparticles at low temperature and optical properties
Wenming Ma, Junsheng Yu, Zhaolin Yuan, et al.
Zinc oxide (ZnO) has a wide direct band gap of 3.37 eV at room temperature and a large excitonic binding energy of 60 meV. In this work, ZnO nanoparticles had been successfully fabricated at low temperature (60 °C). The structures, morphologies and optical properties of ZnO nanoparticles were investigated by X-ray diffraction (XRD), a scanning electron microscope (SEM), UV-Visible absorption and photoluminescence (PL) spectra, respectively. Measurement results of XRD showed that the as-prepared ZnO nanoparticles are a random orientation. The nanoparticles are approximately particle shape with an average size of about 50 nm by SEM observation, UV-Vis absorption spectrum indicated that the as-prepared ZnO nanoparticles dispersed in chloroform are highly transparent in the visible region and have a strong absorption band in the UV region, at the same time, we found a sharp absorption edge at near 370 nm. In addition, in the as-prepared ZnO nanoparticles/chloroform solution, both a near band edge (NBE) ultraviolet photoluminescence peak at 372 nm and a defect related deep level emission (DLE) green peak at 513 nm were observed. It suggested that the NBE photoluminescence peak should be attributed to free excitons transition, the DLE green peak should be ascribed to intrinsic defects of the single ionized oxygen vacancy (Vo *) through our research results. Furthermore, we obtained R (R=INBE/IDLE) value as 0.91. This indicates that there are a large amount of single ionized oxygen vacancies in as-prepared ZnO nanoparticles, which results in poor crystalline quality of ZnO nanoparticles.
Synthesis and luminescent properties of LaPO4:Eu3+ nanocrystal with ultrasonic method
Yanbo Wu, Peng Sun, Hongquan Yu, et al.
It is well know that nanoscale rare earth compounds can increase luminescent quantum efficiency and display resolution. To improve luminescent properties of nanocrystalline phosphors and obtain the nanocrystals with different morphology, many preparation methods have been used, such as hydrothermal approach, sol-gel technique and ultrasonic method, etc. In this paper, the LaPO4: Eu3+ nanocrystals were prepared via the ultrasonic method. There were two series prepared, by changing ultrasonic time, using polyvinglpyrrolidone (PVP) and cetyltrimethylammonium bromide (CTAB) as template, respectively. The morphology, structure and spectra properties of the products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and fluorescence spectrum (FS). The results show that all the LaPO4 nanocrystals have a hexagonal structure, and without other impurity phase appearance. All the samples obtained are nanoparticles in the range of 50-120 nm, which indicates that there are almost no effectives on the morphology of the nanocrystals with the change of template kinds and ultrasonic time. But their luminescent properties depend on the kinds of template. When the ultrasonic time is 1h, the luminescent intensity of the obtained sample using PVP as template is much stronger than that using CTAB, but the 5D0 energy level fluorescence lifetime of the Eu3+ in the sample using PVP template is shorter than that using CTAB. In addition, in the two series, luminescent intensity increases at first, then decreases with the growth of ultrasonic time, but the 5D0 energy level lifetime of Eu3+ shows no regulation.
Texture recognition of SAR image based on surfacelet transform
Dandan Liu, Can Zhao, Chunrui Tang
In order to take full use of SAR image dark areas information, texture recognition method of SAR image based on Surfacelet transform is proposed. Firstly, SAR image in test samples is decomposed into brightness SAR image and reflection SAR image based on Retinex model; secondly, the decomposed SAR image carries through Surfacelet transform, in order to reduce computational complexity and shorten the follow-up recognition time, the decomposed SAR image is processed two dimension three level scale Surfacelet transform, and the first level is 8 directions, the others are 8,2 directions respectively, after image Surfacelet transform, the sparsity of the distribution coefficient is even more evident, especially high-frequency sub-band; thirdly, coefficient matrixes of high-frequency sub-band reduce dimension processing by using the singular value decomposition theory of matrix; fourthly, the final eigenvector are composed of character of energy of coefficient matrix in low-frequency sub-band and first and second-order moment of coefficient matrix in intermediate frequency sub-band and eigenvector by reducing dimension in high-frequency subband; at last, use BP neural network to train with supervised and recognize of samples. The method takes full use of SAR image dark areas information, and the simulation results show that the method the recognition rate is better than other methods.
Effect of different solvents on the performance of organic light-emitting device based on red-fluorescent ACY dye by spin coating method
Shuangjiang Yu, Junsheng Yu, Hong Wang, et al.
A small-molecular red-fluorescent dye of [7-diethylamino-3-(2-thienyl)chronmen-2-ylidene]-2,2-dicyanoviny-lamine (ACY) has been blended into blue-emitting poly(N-vinylcarbazole) (PVK) by using different solvents of chloroform and 1,2-dichloroethane. Photoluminescence characteristic of solvent effects were investigated mainly from the aspect of solvent polarity. To demonstrate the solvent effects in organic light emitting devices (OLEDs), devices with a structure of indium-tin-oxide (ITO)/PVK: ACY (x wt %)/tris(8-quinolinolato) aluminum (Alq3)/Mg: Ag were fabricated, in which the weight doping ratios are x = 0.3, 0.5 and 0.7. Using spin coating method, a blending system of PVK: ACY is dissolved in both chloroform and 1,2-dichloroethane with various doping concentrations. As a result, by choosing chloroform as solvent, a high electroluminescent (EL) performance device with a maximum luminance of 7698 cd/m2 at a driving voltage of 15.5 V was obtained, with a concentration proportion of PVK: ACY at 1000: 7. In the EL spectra of the OLEDs, red and green fluorescence of ACY and Alq3 were detected. It was found that by using 1,2-dichloroethane as a solvent, fluorescent quenching emerged with the enhancement of doping concentration. Energy transfer and Alq3 cations quencher theories were used to discuss different solvent effects on OLEDs.
Measurement of gas permeation through packaging materials of OLED by mass spectrometry
Dongliang Wang, Junjian Li, Xiaohui Wang, et al.
Mass spectrometry method was introduced to measure the gas permeability of OLED packaging materials in this paper. Mass spectrum measuring gas permeability of barrier material have the characteristics of quick measure speed, may measuring any gas permeability, and high sensitivity. The penetration rates and the permeability coefficient of water vapor, oxygen and carbon dioxide permeating the encapsulation materials of OLED such as PET plastic film, UV curable adhesive and vacuum sealing wax film have been measured by using the mass spectrometry. The results of experiments show that the permeability coefficient of water vapor through a PET plastic film is 1.8×10-6 cm2/s, and of water vapor through UV curable adhesive is 1.2×10-6 cm2/s at temperature of 80 °C and relative humidity of 68 %. The water permeability coefficient of vacuum sealing wax at 50 °C and 92 %RH is 1.4×10-7 g/m2day. The water permeability of vacuum sealing wax decreases an order of magnitude than that of UV curable adhesive, So Vacuum sealing wax is suitable for the seal material in the packing of OLED than UV curable adhesive.
Efficient organic photovoltaic cells using 2-(4-biphenylyl)-5-phenyl-1,3,4-oxadiazole as an exciton blocking layer
Wei Zhang, Junsheng Yu, Nana Wang, et al.
By using 2-(4-biphenylyl)-5-phenyl-1,3,4-oxadiazole (PBD) as an exciton blocking layer (EBL) at the organic/cathode interface of conventional copper phthalocyanine/fullerene (CuPc/C60) organic phtovoltaic (OPV) cells, a more efficient OPV cell was fabricated. The electrical characteristics of OPV cells with and without PBD as an exciton blocking layer were studied. The results showed that the power conversion efficiency (η) was increased from 0.7% to 1.58%. Also, the dependency of the power conversion efficiency on the absorption spectra of exciton blocking layer (PBD) in OPV cells was investigated, and it showed that the inserted PBD has almost no effect on the visible light absorption of the OPV cell. Hence, the improved photovoltaic performance is ascribed to a more efficient charge carrier transport balance, leading to more effective exciton separation.
Acceptor thickness effect of exciplex and electroplex emission at heterojunction interface in organic light-emitting diodes
Wei Zhang, Junsheng Yu, Kai Yuan, et al.
Organic light-emitting diodes (OLEDs) consisted of a novel fluorene derivative of 5,6-bis(9,9-dihexyl-9H-fluoren-2-yl)- 2,3-diisocyano-2,3-dihydropyrazine (BDHFLCNPy) and a hole transporting material of N,N'-Di-[(1-naphthalenyl)- N,N'-diphenyl](1,1'-biphenyl)-4,4'-diamine (NPB) were fabricated, and electroluminescence (EL) spectrum of devices were investigated. It was found that light emission around 650 nm observed in devices came from exciplex generated at heterojunction interface by NPB molecules worked as electron donor and BDHFLCNPy molecules worked as electron acceptor. Moreover, a shoulder peak around 500 nm ascribed to BDHFLCNPy exciton was observed. To systemically study the effect of heterojunction structure in exciplex formation, OLEDs with different thickness of acceptor were fabricated. The results illustrated that a shoulder peak around 600 nm occurred in EL when acceptor thickness increases, and BDHFLCNPy exciton emitting strength is relatively altered. The emission band around 600 nm is due to electroplex. The L-V-J properties of OLEDs show that device with the thinnest acceptor layer has the highest luminance and current density. On the contrary, OLEDs with thicker acceptor layer have higher luminance efficiency. The different recombination mechanism of exciton, exciplex and electroplex in heterojunction were studied. Furthermore, the acceptor thickness effect of exciplex and electroplex generating mechanism and energy transferring mechanism between them was also discussed.
Design of driving circuit for binocular CCD image system
Mingyu Zhang, Jianyue Ren, Xingxiang Zhang
The paper designs a driving circuit of high sensitive, wide dynamic and high signal-to-noise ratio for binocular CCD imaging system which adopts a Dalsa-made high resolution full-frame 33-mega pixels area CCD FTF5066M. Inner structure and driving timing of the FTF5066M sensor are presented. Field Programmable Gate Array (FPGA) is used as the main device to accomplish the timing design of the circuits and power driver control of the two sensors. By using the Correlated Double Sampling (CDS) technique, the video noise is reduced and the SNR of the system is increased. A 12- bit A/D converter is used to improve the image quality. The output rate of the imaging system designed with integrated chip can reach to 1.3 frames per second through bi-channel. For its good performance, low power consumption and small volume, the driving system can be applied to aeronautics and astronautics field. With a further improvement, a maximum data output rate of 2.7 frames per second can be reached through all the eight channels of the two CCDs.
A study of two-point multi-section non-uniformity correction auto division algorithm for infrared images
Bo Zhou, Yong Ma, Hao Li, et al.
Traditional two-point multi-section non-uniformity correction method for infrared imaging use fixed number of sections and division points; this would greatly affect the algorithm's performance. In order to solve this problem, an auto division algorithm based on slope difference of average temperature response curves of IRFPA and least square fitting was supposed. This algorithm calculates the gradient of IRFPA's average temperature response curve and find out the turning points, then the approximate positions of division points are decided according to given number of sections or given threshold for slope difference; after that a least square fitting is performed in each section to produce subsection correction lines; finally adjacent lines are connected with each other to get the complete correction curve. Experimental results showed that the residual non-uniformity of an infrared image is greatly diminished from 0.08 % of traditional two-point multi-section method to 0.03 %. The method is still as simple as the traditional algorithm, while the precision of correction is significantly increased.
New LED illumination optical engine for micro-projection display
Chunhai Feng, Zhong Meng, Wenjun Sun
A new optical engine consisting of LEDs, rectangular CPC, rectangular lens array and micro display chip DMD is designed by using of KOLA illumination algorithm for micro-projection display. Detail description and analysis of the rectangular CPC and rectangular lens array are provided. The influence due to the size of rectangular CPC and rectangular lens array is analysed for illuminance uniformity on the DMD chip and light energy efficiency of the optical engine system by software ZEMAX. Based on the analysis of parameter of rectangular lens array, the size of rectangular lens array more decrease the illumination uniformity. Experimental results show that the proposed illumination light optical engine can obtain perfect rectangular focula with higher light uniformity more than 90 % and higher energy efficiency of 40 % to meet the needs of micro-projection display, at the same time the designed illumination optical engine compared with other uniformizing light algorithm have advantages such as: lesser capacity, high illumination uniformity.
Efficiency improvement of yellow organic light-emitting devices by using mixed hole transporting layer
Sujie Chen, Junsheng Yu, Wen Wen, et al.
Organic light-emitting devices (OLEDs) with a novel metal iridium complex of bis[2-(4-tertbutylphenyl) benzothiazolato-N,C2'] iridium (acetylacetonate) [(t-bt)2Ir(acac)] doping into a carbazole-based material 4,4'-bis[N-1-napthyl-N-phenyl-amino]biphenyl (CBP) as light-emitting layer (ETL) were fabricated. The optimum doping concentration of (t-bt)2Ir(acac) phosphor was 8 wt%. The maximum power efficiency (ηp) of the OLED was 8 lm/W. Furthermore, to improve the balance of charge carriers and enhance the ηp of the device, a doping system consisted of NPB hole transporting material and CBP host material with a concentration proportion of 1:3 was employed as the mixed hole transporting layer. OLEDs with a structure of indium-tin oxide (ITO)/N,N'-bis-(1-naphthyl)-N,N'- biphenyl-1,1'-biphenyl-4,4'-diamine (NPB):CBP(1:3)/CBP:(t-bt)2Ir(acac)/2, 9-dimethyl-4, 7-diphenyl-phenanthroline (BCP)/Mg:Ag were fabricated. The results showed that current density was decreased and the maximum ηp of the device was 10.6 lm/W. Compared with the conventional device with NPB as hole transporting layer, the improved maximum ηp of the device with mixed hole transporting layer was increased 32.5 %. This is attributed to the reduction of hole injection amount and transporting mobility by doping material CBP in hole transporting layer, which significant enhances charge carrier balance and electron-hole recombination probability.
Contrast study on GaAs photocathode activation techniques
Jun Niu, Yijun Zhang, Benkang Chang, et al.
At present, two kinds of activation techniques for preparing GaAs NEA photocathode are available. In this paper, according to two kinds of photocurrent curve arising in the activation, the characteristic and mechanism of the two kinds of craft were summed up and compared with each other, and the further theoretical investigation on the mechanism of activation was carried out based on the recent research of NEA surface model for GaAs photocathode. It is proposed as a process principle that during (Cs, O) alternation phase of the activation process of GaAs photocathode, Cs should always be in excessive state. Besides, it is also indicated that whether Cs is excessive during (Cs, O) alternation phase and the Cs/O ratio may affect directly the final property of photocathode. Finally, a method to modify the craft parameters to guard against the deviation from the principle is presented. The presented study is very necessary and significative for optimizing the activation techniques so as to enhance the performances of GaAs NEA photocathodes.
Spectral response variation of exponential-doping transmission-mode GaAs photocathodes in the preparation process
Yijun Zhang, Jun Niu, Benkang Chang, et al.
The exponential-doping structure was applied to prepare the transmission-mode GaAs photocathode, and spectral response curves after high-temperature activation, low-temperature activation and the indium sealing process were respectively measured by use of the on-line spectral response measurement system, to research into the practical effect of the exponential-doping structure on cathode performance. The results show that a high photosensitivity ranging from 560 nm to 880 nm with an ascending trend can be obtained after the high-low temperature activation. In the region of longwave threshold, there is a distinct inflexion indicating a better photoemission capability than the former uniform-doping photocathodes. Besides, the spectral response curve in the whole response waveband, especially the long-wave region obviously decreases after indium seal. Compared with the fitted surface electron escape probability after Cs-O activation, it decreases after indium seal according to the quantum efficiency formula of exponential-doping transmission-mode GaAs photocathodes. Based on the double dipole model, the reasons for the variation of spectral response shape are explained on account of the relation between surface escape probability and the evolution of surface potential barrier profile.
Properties of photoelectricity of WOx-doped ITO thin films
Ye Liu, Zhuying Li, Chong Wang, et al.
Indium-tin-oxide (ITO) film is an n-semiconductor transparent conductive film. It has many good properties: conductivity, transmittance in visible region, absorptivity in ultraviolet. And tungsten oxide has good conductivity and it can keep stable structure in high temperature, also it has wearable and anti-corrupt properties. Therefore, tungsten oxide can be added gradually on ITO thin films by magnetron sputtering to research the optical and electrical performance of the doped films. We research the performance of the doped films in five aspects: X-ray diffraction spectroscopy, Scanning electron microscope are used to investigate the crystal structure, surface morphology. UV-visible spectroscopy is used to display the transmittance and absorption spectrum of the films. The thin films' performance of electrochemistry is tested by the workstation of electrochemistry. Its conductivity is tested by Four-probe sheet resistivity meter. The main conclusion: The analysis of SEM results shows that the surface morphology of the films is granulated. Transmittance spectrums suggest that the transmittance of ITO films have been increased by proper doping, the percentage of transmittance is over 90% from visible to near-infrared region. Besides, it shows well in the properties of electricity and electrochemistry in the doped films.
An objective assessment method of digital image mosaic artifacts visibility based on visual perception
The difference of illumination between to-be-mosaicked images will cause mosaic artifacts when digital images are mosaicked. An objective assessment method of digital images mosaic artifacts visibility based on human visual perception has been studied in this paper. The process of the method are as follows; 1) the gradient errors image is obtained according to the to-be-mosaicked images, 2) the just noticeable difference (JND) of reference image is derived by considering the human visual frequency sensitivity, the brightness mask effects and texture mask effects on visual resolution comprehensively; 3) the mosaic artifacts image which is perceptible visually can be acquired by subtracting the JND threshold values from the wavelet coefficients of gradient errors image in wavelet domain. The mosaic artifacts visibility (MAV) of digital image is constructed to use as an objective assessment index of image stitching seam visibility by considering the average value and information entropy of the mosaic artifacts image comprehensively. The experiment indicates that the objective assessment results of digital image mosaic artifacts visibility by MAV index are consistent with those of the subjective perceptual method basically.
Research on APD-based non-line-of-sight UV communication system
Rongyang Wang, Ling Wang, Chao Li, et al.
In this paper, specific issues in designing an avalanche photodiode (APD)-based non-line-of-sight (NLOS) ultraviolet (UV) communication system are investigated. A proper wavelength of the UV LEDs and a system configuration should be considered carefully to assure the feasibility of this system. Using the single scattering model, the received optical power at the sensitive area of the APD can be calculated. According to the calculation, it revealed that the scattered ultraviolet signal level was very low; therefore, a post signal processing circuit was necessary. The authors put forward the key components of the circuit based on the compromise between signal bandwidth and gain. The performance of this circuit was evaluated by means of software simulation, and continued work was involved to improve its signal noise ratio (SNR). The transmitter used in this system was 365 nm UV LED array. Strictly speaking, this was not the practical outdoor UV communication system. Since the scattering coefficient of 365 nm UV only drops a little compared with solar blind UV, the research-grade UV communication could be carried out in a darkroom without a great influence. By combining an APD with a compound parabolic concentrator (CPC) optical system, the effective collection area and field of view (FOV) of the detector could be adjusted. Several issues were also raised to improve the performance of UV communication system, including using more powerful UV LEDs and choosing suitable modulation schemes.
Study on the experiment of cable tension measurement with FBG sensors
Fiber Bragg Grating (FBG) sensors sense the change of temperature or strain by detecting the wavelength shifted reflected by the Bragg grating carved on a fiber. Aiming at measuring tension of cables, we did a lot of experiments with FBGs, testing its loading characteristics, temperature response, repeatability, consistency of different sensors, and long term stabilization. When analyzing data, we find that environment temperature has a serious influence to the result. So we use temperature compensation with a temperature sensor. Then we proceeded same experiments with traditional force sensor under the same condition, compared their result and analyze the advantages and disadvantages of the two kinds of sensors in the measurement of cable tension. At last, we made some prospect on FBG using on cable tension measurement.
Photoluminescence of Mn+ doped GaAs
Huiying Zhou, Shengchun Qu, Shuzhi Liao, et al.
Photoluminescence is one of the most useful techniques to obtain information about optoelectronic properties and defect structures of materials. In this work, the room-temperature and low temperature photoluminescence of Mn-doped GaAs were investigated, respectively. Mn-doped GaAs structure materials were prepared by Mn+ ion implantation at room temperature into GaAs. The implanted samples were subsequently annealed at various temperatures under N2 atmosphere to recrystallize the samples and remove implant damage. A strong peak was found for the sample annealed at 950 °C for 5 s. Transitions near 0.989 eV (1254 nm), 1.155 eV (1074 nm) and 1.329 eV (933 nm) were identified and formation of these emissions was analyzed for all prepared samples. This structure material could have myriad applications, including information storage, magnet-optical properties and energy level engineering.
Photostimulated luminescence of BaFCl:Eu2+ in oxide glass ceramics
Xianguo Meng, Ji Zhou
Oxide glass ceramics with different concentrations of BaFCl:Eu2+ doping have been prepared. Photoluminescence (PL) and photostimulated luminescence (PSL) after x-ray irradiation were observed at room temperature. The PSL was attributed to the characteristic emission of Eu2+ in crystallites of BaFCl, which formed in the glass. Increasing the concentration of BaFCl:Eu2+ causes an increase in PSL conversion efficiency , but a decrease in transparency. The tradeoff between optical transparency and PSL intensity over different concentrations of BaFCl for X-ray imaging plate applications was briefly discussed.
A novel design of infrared focal plane array with digital read out interface
Xiaoyang Liu, Ruijun Ding, Wei Lu, et al.
Infrared focal plane array (IRFPA) with digital read out interface is a key sign of the third generation IRFPA, which plays an important role in the reliability and miniaturization of infrared systems. A readout integrated circuit (ROIC) of IRFPA with digital readout interface based on dual ramp single slope (DRSS) analog to digital converter (ADC) architecture is presented in the paper. The design is realized using shared ADCs in column-wise and these ADCs are consisted of simplified DRSS architecture and shared units. Sample, conversion and readout are proceeded simultaneously in order to adapt large scale and high readout frame rate application. This circuit also shows many advantages, including small area and low power consumption. Simulation result shows that this architecture can be expand to 320×256 pixel array with a frame rate of 100 frames per second or a larger size whit lower frame rate, the quantized resolution of this circuit is 12 bit, and the analog power consumption is only 17μw per ADC.
Reliability studies of high operating temperature MCT photoconductor detectors
Wei Wang, Jintong Xu, Yan Zhang, et al.
This paper concerns HgCdTe (MCT) infrared photoconductor detectors with high operating temperature. The near room temperature operation of detectors have advantages of light weight, less cost and convenient usage. Their performances are modest and they suffer from reliable problems. These detectors face with stability of the package, chip bonding area and passivation layers. It's important to evaluate and improve the reliability of such detectors. Defective detectors were studied with SEM(Scanning electron microscope) and microscopy. Statistically significant differences were observed between the influence of operating temperature and the influence of humidity. It was also found that humility has statistically significant influence upon the stability of the chip bonding and passivation layers, and the amount of humility isn't strongly correlated to the damage on the surface. Considering about the commonly found failures modes in detectors, special test structures were designed to improve the reliability of detectors. An accelerated life test was also implemented to estimate the lifetime of the high operating temperature MCT photoconductor detectors.
Etch-induced damage of HgCdTe caused by inductively coupled plasma etching technique
Wenting Yin, Wenzhong Zhou, Jian Huang
HgCdTe third-generation infrared focal plane arrays such as avalanche photodiodes, two-color detectors and multi-color detectors require isolation of high aspect ratio trenches with admissible etch induced damage at the surface and sidewalls. Dry etch has many advantages compare with wet etch such as high anisotropy, good uniformity and good reproducibility. Inductively coupled plasma (ICP) etching is most widely used for its low etch induced damage which is a new high density plasma technique. It's very important to understand etching mechanisms and reduce etch induced damage for the low damage threshold of HgCdTe which is due to weak Hg-Te bond and low volatility of CdTe component. The main work of this paper is researching the influence of etch induced damage caused by different mask technique using inductively coupled plasma etching instrument with a feasible technics. In this experiment we used two different masks, one only has a film of silicon dioxide which we called thin mask, its thickness is less than one micrometer, and the other is composed of resist and silicon dioxide which we called complex thick mask, its thickness is several micrometers. We tested the current-voltage (I-V) characteristics of a chip which has a special structure achieved by dry etch and about one micrometer wet etch to remove the etch induced damage film. Then we found that in a same condition the I-V characteristics of the chip which used complex thick mask is distinctly better than the chip which used thin mask. Resist and silicon dioxide complex thick mask can effectively reduce etch induced damage. The reasons for this result have two aspects, in one hand, the grown process of silicon dioxide can cause damage of HgCdTe surface, make a thick resist between HgCdTe and silicon dioxide can reduce the damage of HgCdTe surface, in the other hand, complex thick mask can hold up the damage of trench sidewall in etch process.
Effects of solution properties on the morphology and diameters of nanofibers fabricated by electrospinning
Hongjun Jing, Yadong Jiang, Xiaosong Du
In this paper, four different series of polymer solutions were presented to study the effects of solution properties on the morphology and diameters of nanofibers, including the polyethersulfone (PES) dissolving in N, N-dimethylformamide, polyvinylpyrrolidone (PVP) in ethanol, poly(acrylic acid) (PAA) in water and poly(vinylidene fluoride) (PVDF) in N, Ndimethyl acetamide. These solutions revealed different conditions of the formation of beads, the spatial structures and the diameter of fibers. The PVDF nanofibers had plenty of small beads on the fibers, while the other three were uniform fibers without beads. The nanofibers of PES, PVP and PVDF showed good three dimensional structures except the PAA fibrous membranes. The change of fiber diameters of PVDF was much larger than that of PVP.
Research of a high-efficiency practical distributed fiber Bragg grating temperature sensor system
Yanjun Zhang, Bo Wei, Junbo Lou, et al.
A novel practical distribute Fiber Bragg Grating sensor system is presented in this paper. When the bandwidth of the broadband light source is 300 nm, the whole system can monitor more than 1000 meters and it is divided into 100 sections. Each section has 4 gratings with identical center wavelength, and these identical gratings monitor a small zone. The center wavelength of grating will shift due to temperature changes. By detecting the reflected light, the change of temperature and the location can be obtained. The system will alarm if this temperature is over setting value. A high-precision optoelectronic detector is used to detect the optical power, and the resolution is 1 nw. Based on the theory analysis, temperature experiments of different wavelength have been done. Based on the ARM Processor Cores, we designed an optimized algorithm which encoded all gratings and coordinated Fabry-Perot (F-P) tunable filter and optoelectronic detection system synchronously. The accuracy of the algorithm is up to 10 μs. The results show that grating center wavelength varies with temperature and linearity is over 99.6 %. The system not only can realized the temperature measurements but also expand the monitor range. It has been seen in experiments that the characteristics of the measured precisions of good reliability and high efficiency, application in distributed multimetering.
Infrared non-uniformity correction algorithm based on fast independent component blind separation
Hong-Bin Nie, Wei Zhang, Yi-Ming Cao, et al.
Going with Infrared Focal Plane Array (IRFPA) development, the application of infrared imaging system is more and more extensive, it's well known that the Non-Uniformity Correction (NUC) is the only necessary data soft processing in the whole infrared imaging data link, it will be seen from this that the NUC quality stand or fall influences the final imaging product quality directly, for target detection and identification system, it increases the complexity and timeliness of the target detection and identification algorithm undoubtedly. Currently, the Non-Uniformity Correction (NUC) algorithm can be divided two classifications: the one is that Non-Uniformity Correction based on calibration source, this algorithm assumes the infrared system response characteristic is linear, takes the dark current and gain as the two correction parameters, but for nonlinear, especially for the response drift characteristic and the ambient temperature change, the higher the system sensibility is, the greater the influence is and the higher the design requirements for system stray radiation are. The correction effectiveness is limited seriously; the another is adaptive correction algorithm based on scene (SBNUC), it can be subdivided time domain, space domain and motion estimation processing algorithms, although it do not need physical calibration source and also reduces the influence of system response drift to a certain degree, but the requirement is rigorous for statistics specimen and size, and the rapidity of convergence and stability are different. In this paper, according to blind information source decomposition technique, the infrared image is divided to signal and noise as two information sources, a new Non-Uniformity Correction method based on Fast Independent Component (FastICA) blind separation is put forward. By means of the experimental contrast analysis for the linear correction algorithm and constant statistics algorithm of real infrared image, by this new algorithm, the influence of the system response drift and the ambient temperature change for the linear correction algorithm based on physical calibration source is not only suppressed, but also the shortages of the scene-based Non-Uniformity correction (SBNUC) in statistics specimen and size are overcome partly. The experimental result proved the effectiveness of this algorithm in the paper which effectively separated the signal and noise of the infrared image. At the same time, the algorithm in the paper supplied a new solution of Non-Uniformity Correction (NUC) by the experiment.
Application research of fault diagnosis expert system for photoelectric tracking device based on BP NN
Mingliang Hou, Yong Zhang, Feng Liu, et al.
In order to overcome the deficiencies of poor adaptive capacity, lack of inspiration and narrow domain knowledge of expert system and fundamentally improve the diagnostic efficiency, an intelligent fault diagnosis expert system for photoelectric tracking devices, based on BP neural network, is put forward. Firstly, in this paper, some key basic concepts and principles of intelligent fault diagnosis technology are proposed. Secondly, according to the difficulty of multiple and coupling fault diagnosis, after making a comparative analysis of the related BP neural network algorithms, such as the quasi-Newton method, the stretch BP method and the conjugate gradient method, a neural network fault diagnosis reasoning method based on the Levenberg-Marquardt is designed, which combined the implementation of the diagnosis expert system. Finally, several interrelated essential implementation issues, such as the architecture of the system and the VR technology based on OpenGL, are also discussed. Practical experiments and applications demonstrate that the proposed approach is effective, robust and universal.
Distinguishing different parts of objects by terahertz imaging
Jin Ge, Reng Wang, Shuhong Hu, et al.
Since every matter has its distinctive absorption and transmission capacity of terahertz, Terahertz time domain spectroscopy provides a powerful means to distinguish the different parts of objects. The transmittance of terahertz under different frequency can reflect the absorption distribution of the different parts of the samples. The phase shift of the terahertz wave indicates the change of optical thickness of the sample. Tree leaves, plastic ring, plastic convex lens and plastic piece with a small hole have been imaged by terahertz. As widespread samples, leaves are proved to be well imaged by terahertz wave. For the moisture content at different parts of leaves, such as mesophyll and vein, is not the same, the absorption of terahertz at these parts are quite different. At 1.4THz, the leaf's image is of good quality and the vein grids are well shown. The hole and defects in the plastic ring are also clearly shown in the THz image because the phase shifts of terahertz in different parts, such as air, defects or plastic region are not the same. It is also shown that objects with large radius of curvature are suitable for THz imagining and the scattering of THz does not affect THz phase information too much. In short, Terahertz imaging is a powerful technique to distinguish the different parts of most objects as long as the absorption of THz is not very strong.
Fabrication and evaulation of the CdZnTe microlens arrays
Jian Huang, Wenhong Zhou, Wenting Yin
This paper presents a modified thermal reflow process to fabricate CdZnTe (CZT) microlens arrays and a new convenient method to evaluate the quality of the microlens. In the fabrication experiment, square photoresist (PR) isolated-islands with almost zero gap each other were formed on a CdZnTe substrate by the underexposure photolithographic process firstly. Then, high fill-factor (almost 100 %) PR microlens arrays were generated via thermal reflow the islands at 110 °C for 30 minutes. Finally, through etching the substrate using the PR microlens arrays as the mask by an inductively coupled plasma (ICP) dry etching process with Ar/N2/CH4 gas, the high fill-factor CdZnTe microlens arrays were achieved. Besides, a new convenient method to evaluate the quality of the microlens was also established in this paper. At the first step of the evaluation, the data of surface topography of the microlens fabricated was recorded by the confocal scanning laser microscope (CSLM). Then, the characteristic of the microlens such as the surface topography, focusing properties, the light intensity distribution of the microlens, etc. was simulated and displayed by the procedure base on the CZT optical parameters and the data of the actual surface topography of the microlens. The results show that the microlens fabricated by the modified thermal reflow process can focus 80 % incident light of the pixel on the 30 % central region, with only 1.6 % optical crosstalk.
Influence of doping I2 into MEH-PPV on carrier transporting capability and electroluminescence properties
Zhiming Cheng, Fujun Zhang
The current-voltage characteristics and electroluminescence (EL) spectra were studied with different I2 doping concentration in MEH-PPV based on single layer and double layer organic light emitting diodes (OLEDs). For the single layer devices, EL intensity and current was increased with the doping concentration under the same driving voltage. For the double layer devices, the charge carrier recombination zone was controlled by the different I2 doping concentration compared to these devices without doping. The variation of EL spectra was discussed from the improvement of hole mobility in MEH-PPV layer induced by I2 doping into it.
Non-uniformity correction for infrared focal plane array with image based on neural network algorithm
Tingting Wang, Junsheng Yu, Yun Zhou, et al.
Non-uniformity response of detectors based on infrared focal plane array (IRFPA) result in fixed pattern noise (FPN) due to detector materials' non-uniformity and fabrication technology. Once fixed pattern noise added to the infrared image, focal plane image quality will have a serious impact. So non-uniformity correction (NUC) is a key technology in IRFPA application. This paper briefly introduces the traditional neural network algorithm and puts forward an improved algorithm for the neural network algorithm for NUC of infrared focal plane arrays. The main improvement is focused on the estimation method of desired image. The algorithm is used to analyze the image array, correcting data on the array both in space and in time. The correction image in the text is from the infrared data sequence which is more successful of three frames of data obtained. It was found that the estimated image corrected by new algorithm is closer to real image than the estimated image corrected by other algorithm. Moreover, we simulated the new proposed algorithm using Matlab. The results showed that the method of spatial and temporal co-correction of the images is more realistic than the original image.
Effective local-field confinement of silver nanoparticle dimer arrays
Li Yao, Xufeng Li, Tiangang Yang, et al.
The optical properties of silver spherical nanoparticle dimer arrays with various incident wavelength are investigated by using the finite difference time domain method. Due to surface plasmon resonance, in the arrays of strongly coupled Ag nanoparticles, the energy of incident light is effectively confined in the gap of penultimate dimer under the influence of surface plasmonic reflection at the end of array structure. Furthermore, the suitable radius of the nanoparticles can be chosen to obtain the resonant peak at the optional position in the range of visible-nearinfrared wavelength. The above effects can be utilized to design effective functional end-structures in integrated optics.
The influence of substrate temperature on the electrical and optical properties of titanium oxide thin films prepared by d.c. reactive magnetron sputtering
Yongfeng Ju, Zhiming Wu, Yonglong Qiu, et al.
In this investigation, a novel heat-sensitive material titanium oxide (TiOx) thin film was deposited on well cleaned K9 glass substrates by d.c. reactive magnetron sputtering from a metallic titanium target in an Ar + O2 gas mixture. In order to obtain proper TiOx thin films, deposition parameters should be properly controlled. In our system, TiOx thin films were obtained at different substrate temperature while total pressure and oxygen partial pressure were kept at 1 Pa and 0.6 Pa, d.c. power of 100 W, and the deposition time was adjusted in order to deposit thin films with a constant thickness close to 200 nm. The crystalline structure was characterized by X-ray diffraction (XRD) analysis and the results show that all the deposited films have an amorphous structure. In this paper, we have mainly investigated the dependence of electrical and optical properties of the reactively sputtered TiOx thin films on the different substrate temperature during the sputtering process, i.e., as the K9 glass substrate temperature increases from 100 °C to 250°C, the sheet resistance Rs of TiOx thin films is ranged from 305 kΩ/square to 36 kΩ/square, temperature coefficient of resistance (TCR) value up to -2.12 %/K is obtained, optical band gap decreases from 3.34 eV to 3.28 eV. Through the analysis and discussion of the above experimental data, we could obtain the conclusion that the variation in substrate temperature during the sputtering deposition plays a considerable important role in the electrical and optical properties of all the deposited films.
Research of laser active image-denoising method
Jijun Luo, Jun Xu, Suxia Hou, et al.
In this paper, an image-denoising method is presented based on mathematical morphology and wavelet transform. Highfrequency coefficients are processed by mathematical morphology firstly. Then, according to the respective characteristics, high frequency sub-band images at horizontal, vertical and angular directions are denoised by three different filter templates after wavelet transform. We take measures to protect edge information and detail of image. Experiment result shows that the noise of the image is removed effectively. At the same time, the detail of the image is kept well. The method has better denoising effect.
A back-illuminated heterojunctions ultraviolet photodetector based on ZnO film
Xiandong Jiang, Dawei Li, Wenjun Yang, et al.
In this paper, we present the investigation of a back-illuminated heterojunctions ultraviolet detector, which were fabricated by depositing Ag-doped ZnO based (ZnO-TiO2) thin film on transparent conductive layer of ITO coated quartz substrate though the reactive radio-frequency (RF) magnetron sputtering at higher oxygen pressure. The p-n junction characteristic is confirmed by current-voltage (I-V) measurements. The turn-on voltage was 6 V, with a low leakage current under reverse bias (-5 V), corresponding values was just 0.2 nA . It is clearly showed the rectifying characteristics of typical p-n junction's rectifier behaviors. The structural, component and UV (365 nm, 1400 μW/cm2) photoresponse properties were explored by X-ray diffraction (XRD), Scanning Electron Microscope (SEM), X-ray energy dispersive spectrometer (EDS) and Tektronix oscilloscope. The results showed that: Ag in substitution form in the ZnO lattice, Ag doping concentration is low, the sample is highly c-axis preferred orientation, With the increase in doped Ag volume, ZnO film of 002 peaks no longer appear. The surface of the Ag doped ZnO based film exhibits a smooth surface and very dense structure, no visible pores and defects over the film were observed.The ultraviolet response time measurements showed rise and fall time are several seconds Level.
Design of the acquisition system with low-noise based on 160×120 uncooled infrared detector
Yanmin Xing, Yun Zhou
This paper discusses the importance of the Uncooled infrared focal plane array detector with low noise, and focuses on solving the hardware problem - how to reduce the noise of the detector by the technique of I2C and differential input. Meanwhile the hardware circuitry should meet the driving conditions. Beside of this, the author aims to describe the method using in reducing the noise of the detector driver circuit, the quantization noise of the A/D circuit, removing the image background noise, non-uniformity correction and so on. Moreover, the author analyzes the noisy level of each part of the circuitry in theory, and obtains the RMS and SNR of the practical image. The results show that: the acquisition system is working properly and has a comparably low noise performance. The RMS noise of the acquisition system is 568 μV, and the SNR reaches over 60 dB under the blackbody irradiation and the room temperature.
Design of high-speed low-noise pre-amplifier for CCD camera
Xucheng Xue, Shuyan Zhang, Hongfa Li, et al.
Pre-amplifier circuit is critical for the noise performance of the high speed CCD camera. Its main functions are amplification and impedance transform. The high speed and low noise pre-amplifier of CCD camera is discussed and designed in this paper. The high speed and low noise operational amplifier OPA842 is adopted as the main part. The gain-set resistors for the amplifier are designed optimally. The different precision gain-set resistors are swept using Monte Carlo method. CCD video signal which has high DC offset voltage is AC coupled to the amplifier. The output signal of the amplifier is source terminated using 50 ohms matching resistor so as to transmit the video signal through coaxial cable. When the circuit works in high speed, the PCB will have important effect to circuit performance and can even cause the amplifier unstable due to the parasitic problem of PCB. So the parasitic model of the PCB is established and the PCB layout design issues are also presented. The design result shows that the pre-amplifier can be used in the camera whose pixel rate could be up to 40 MHz and its input referred noise density is about 3 nV/Hz1/2.
High-efficient and brightness white organic light-emitting diodes operated at low bias voltage
Lei Zhang, Junsheng Yu, Kai Yuan, et al.
White organic light-emitting diodes (OLEDs) used for display application and lighting need to possess high efficiency, high brightness, and low driving voltage. In this work, white OLEDs consisted of ambipolar 9,10-bis 2-naphthyl anthracene (ADN) as a host of blue light-emitting layer (EML) doped with tetrabutyleperlene (TBPe) and a thin codoped layer consisted of N, N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)-benzidine (NPB) as a host of yellow light-emitting layer doped with 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidin-4-yl-vinyl)-4H-pyran (DCJTB) were investigated. With appropriate tuning in the film thickness, position, and dopant concentration of the co-doped layer, a white OLED with a luminance yield of 10.02 cd/A with the CIE coordinates of (0.29, 0.33) has been achieved at a bias voltage of 9 V and a luminance level of over 10,000 cd/m2. By introducing the PIN structure with both HIL and bis(10- hydroxybenzo-quinolinato)-beryllium (BeBq2) ETL, the power efficiency of white OLED was improved.
The spectral adaptation applied to image color appearance model
Huimin Yang, Weiping Yang, Chunwen Guo, et al.
The major aim of Color Appearance Model is trying to resolve the problem of high faithful color reproduction under different viewing conditions, which is one of the main mathematical methods fulfilling the cross-media color production. Currently used Color Appearance Model (CAM) based on von Kries chromatic adaptation transform, that is, CAM acts upon chromatic signals such as tristimulus values rather than spectral characteristics. The spectral adaptation model introduced by Fairchild in 2006 based on the spectral reflectance factor of stimulus and the spectral power distribution function of light source. The new way models the vision phenomenon with no requirement for the chromatic processing. Munsell color chips are used as basic data. Spectral adaptation model and CIELAB color space are employed to predict corresponding color appearance attributes. Then the comparison to CAT02 chromatic adaptation transform is also made. The result shows that spectral adaptation model has a high degree of accuracy in lightness performance, and the relative error is between 2 % and 5 %. But the accuracy of chroma is less than CAT02, and both models have good uniformity in hue performance. Taking the image color appearance model as the carrier, the spectral adaptation model is applied to the image reproduction. The methods are used to model the image with no requirements for the CAT02 chromatic adaptation processing and to use spectral adaptation as pretreatment, then to carry out the chromatic adaptation transformation. Discussion of the advantages and limitations of the model and the practical value in image rendering is also presented.
Novel structure for ultrafast uncooled focal plane array
Zhengxi Cheng, Bin Ma, Xuemin Zhang, et al.
A novel structure combining normal uncooled focal plane array (UFPA) microbridge and RF MEMS switch is presented. The MEMS switch is integrated into the microbridge without any modification of the microbridge structure and fabrication process. The upper electrode of the switch is the IR absorbing layer of the microbridge, and the down electrode is the reflecting mirror of the IR resonant chamber on the substrate. With the help of the MEMS switch, the microbridge can be pulled down to the substrate, and be cooled to the substrate temperature T0. Correlated double sampling(CDS) method is used to read out the difference between R(T0) and R(T1), where R(T0) is the value of thermistor on the microbridge when the microbridge is pulled down to the substrate, and cooled to the substrate temperature T0, and R(T1) is the value of thermistor when the microbridge is heated up to T1 by radiation after the microbridge is released from the substrate for a certain short time. The difference between R(T0) and R(T1) is just related to thermistor R itself, and no reference resistor is need. Match between the thermistor and its reference in normal structure, which is the most difficult task in fabrication, is no longer existed. And the signal due to mismatch between the thermistor and the reference resistor, which is very large compared with the signal due to the thermistor change, and which often makes op saturated, also no long exists. In CDS read-out circuit, the difference between R(T0) and R(T1) can be very small, which cannot approximate thermal equilibrium state. So it only needs a very short time for the microbridge to absorb radiation. The simulation results show that this novel structure can work up to 10KHz without any performance decrease, which is 100 times faster than the speed of the normal structure.
Fabrication of black silicon materials by wet etching and characterization
Zhengyu Guo, Zhiming Wu, Anyuan Zhang, et al.
In this paper we use Si3N4 membrane acting as mask in fabrication of black silicon by wet etching technique, and the sample have nearly 90% absorptance at wavelength from 250 nm to 1000 nm. The experiments result shows that Si3N4 membrane as mask wet etching technique for fabrication of black silicon is feasibility, and has much more advantages compared to fabrication of black silicon by using femtosecond laser, RIE and hydrothermal etching. It provides a proper and economical method for fabrication of black silicon visible and near-infrared optoelectronic devices.
Effects of annealing on InAsSb films grown by the modified LPE technique
Changhong Sun, Shuhong Hu, Qiwei Wang, et al.
We have studied the annealing effects on InAsSb thick films grown by the modified liquid phase epitaxy (LPE) technique. Appropriate annealing treatment can efficiently eliminate Sb vacancy and stain which are formed during growing process, thus it is necessary to study the influence of annealing condition (temperature, ambient, time and cooling rate) on the properties of InAsSb epilayer. The X-ray diffraction measurement (XRD) showed the annealed InAsSb films were polycrystalline with (111)-preferred orientation, except for the two samples annealed with 350 °C for 15 hours and with rapid cooling rate, respectively, which exhibited a (100)-preferred orientation. The Fourier transform infrared (FTIR) revealed a cut off wavelength more than 10 μm for the samples. Also, the infrared transmittance would be improved due to decreasing of film defects by appropriate annealing treatment. Measurement of electrical properties for samples revealed the increase of electron mobility and the reduce of carrier concentration at 77K when keeping anneal temperature low at 350 °C and extending anneal time, indicating the electrical improvement of the InAsSb layers.
Preparation and mechanism of carbon encapsulated Cu nanoparticles
Jun Xue, Houkui Xiang, Shuli Pang, et al.
In recent years, research interests in copper nanoparticles have been increased significantly due to their excellent performance in tribology, catalysis and many other fields. However, their applications have been still limited because the bare nanoparticles are easily oxidized. Therefore, the study of copper nanoparticles encapsulated in carbonaceous shells is an important issue. In this study, the carbon encapsulated copper nanoparticles were prepared using copper nitrate as the metal sources and using sucrose as the carbon sources, through reducing and annealing. The phase, morphology, particle size and structure of as-prepared samples were characterized using X-ray diffraction, field emission transmission electron microscopy, scanning electron microscopy and Raman spectroscopy, respectively. The results indicate that the samples exhibit well core/shell structure, with sphere form and uniform size (50 nm in average). The copper cores consists of polycrystalline particles with fcc structure, whose size varies from 20 nm to 60 nm. The shell is amorphous carbon and its thickness is about 10 nm. In addition, the formation mechanism of carbon encapsulated copper nanoparticles was discussed and presented in the paper.
Studies of a colorimetric array consisted of metalloporphrins and Pt complexes
Jing Luo, Tengshuang Ma, Lu Li, et al.
We have studied the absorption of volatile organic compounds (VOCs) and vapochromic characterization by a colorimetric array based on metalloporphyrins and Pt complexes: ZnTPP, CuTPP, and [Pt(Me2bizmpy)Cl]Cl (TPP=tetraphenylporphrins; Me2bzimpy=2,6-bis(N-methylbenzimidazol-2-yl)pyridine). The array was exposed to pyridine, tetrahydrofuran, ethyl acetate, methanol and acetonitrile. The experimental results demonstrate that the Pt complexes are sensitive to methanol and acetonitrile, while ZnTPP and CuTPP present an obvious response to pyridine, tetrahydrofuran and ethyl acetate. The response behaviors are reversible and rapid within seconds. The changes of Ultra Violet Visible (UV-visible) absorption spectrums of ZnTPP and CuTPP LB films before and after exposure upon the VOCs are also discussed. In addition, the differences of absorption spectrum of Pt complexes dissolved in several solvents are mentioned. The results show that [Pt(Me2bizmpy)Cl]Cl, CuTPP and ZnTPP exhibit reversible changes of action with VOCs, and they show promising future to be used in Smell-Seeing Electronic Nose to identify VOCs.
A novel colored electrophoretic core/shell particles prepared by precipitation polymerization
Yuguang Feng, Feng Teng, Shihua Huang
In one bath 3 stages process, Surface-ionized core with pyridinium was dyed separately with ordinary red, green, blue acid dyes, and was changed into color microsphere. The shell polymer with epoxy group was prepared to reduce travel resistance, and then the colored electrophoretic particle was obtained by means of ionizing the core-shell microsphere. After the microsphere was characterized by DSC, TG, FTIR and SEM, zeta potential of electrophoretic particles dispersed in organic solvents was tested and changed regularly with particle size and concentration.
Subpixel edge-detection algorithm based on pseudo-Zernike moments
Kun Zhang, Haiqing Chen, Qingwen Liang, et al.
In order to meet the demands of high precision localization and anti-interference performance for optoelectronic detection and imaging devices, a new subpixel edge detection approach based on orthogonal Pseudo-Zernike moments is proposed in this paper with both theoretical analysis and experimental demonstration. First, the ideal step model of subpixel edge is established, and the specific characteristics of edge points can be extracted through the convolution with each order of Pseudo-Zernike moments. According to the principle of amplitude rotation invariance, the parameters of subpixel edge can be obtained by analyzing the relationships between different orders and repetitions of Pseudo-Zernike moments when the image edge is rotated to the vertical direction. And then the actual coordination of the subpixel edge point can be identified. Comparing with other approaches such as spatial moment operators, and Zernike moment algorithm, the experiment results prove that the proposed method has the virtue of higher measuring precision and better noise suppression performance. The edge detection accuracy is up to 0.07 pixel for straight lines with noise, and 0.1 pixel for curves with noise. Therefore, it can be concluded that the proposed method is an efficient approach with a relatively high accuracy and stabilization for image edge detection.
Study on height calibration in the PMP measurement system
Ya-feng Zhang, Hua-zhi Wu, Xuetao Pan, et al.
Phase modulated object height information is get by phase shift technology or Fourier transformation technology in the PMP measurement system, and then get continuous phase by phase demodulation and phase unwrapping technology, and get object height information based on system height formula. In theory, telecentric beam path projector lens center and CCD incidence diaphragm center are located in the common vertical plane, and their light axis are located in the common horizontal plane, and then exact system parameters are get. But it is impossible to come true this demand in fact. So in this paper, calibrate object height and optimize structure parameters in a general system by the least square interactive method and genetic algorithm, in which selected real-coded Genetic algorithm, right population size, adaptive fitness function, crossover operator and mutation operator, and then realized spatial identification. Compared with the traditional least square interactive method, experimental results show that this method has better calibration precision and improves the 3-D measure precision of the system.
Effects of different nanostructural ZnS films on the characteristics of organic/inorganic heterostructure devices
Lifang Lu, Zheng Xu, Fujun Zhang, et al.
Organic/inorganic heterostructure ITO/poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene vinylene] (MEHPPV)/ ZnS/Al devices were fabricated. The effects of different nanostructural ZnS thin films on the characteristics of the devices were studied in detail. Different nanostructural ZnS thin films were prepared by glancing angle deposition (GLAD) technology. ZnS films were deposited on pieces of indium tin oxide (ITO) substrates coated with MEH-PPV in an electron beam evaporation system when the oblique angle was set to 0° and 80° respectively. During the deposition process, the base pressure of vacuum chamber was 3×10-4 Pa, the deposition rate was fixed at 0.2 nm/s and the rotation rate of the substrate was 0.05 rev/s. Scanning electron microscope (SEM) images show that ZnS nanocrystalline films were formed on the substrates at different oblique angles, but the nanocolumnar structure was only formed at the situation of α=80°, and a continuous and uniform ZnS thin film was obtained at 0°. The electroluminescence (EL) intensities of the organic/inorganic heterostructure devices were enhanced compared with the single-layer devices, and the device with the nanocolumnar ZnS layer showed higher emission intensity compared with the one composed by the continuous ZnS film deposited at normal incidence under the same driving voltage. The different nanostructural ZnS films were found to have direct effects on the electrical and luminance characteristics of the organic/inorganic heterostructure devices.
Au-coated MCP photo-detector and its energy spectrum response
Zheng Yuan, Tao Chen, Yunfeng Li
Micro-channel Plate (MCP), which can be served as electron multiplier achieved by the surface of micro-pores that has some electrical conductivity and performs well in producing secondary electrons, is a fiberglass plate made of silicate glass containing oxide of lead, bismuth and otherwise. Once coated with cathode film both sides, MCP is capable of responding to ultraviolet (UV) of several eV and x-ray of several keV. When gold is applied as photocathode, it has good stability of emission, photoelectric emission character would not be changed even though exposed in the air several times, and the photoelectric current density distributes uniformly. This article introduces a special photo-detector, which employs MCP as dielectric substrate, and evaporates a layer of thin Au on the front surface acted as the photocathode and input electrode, while a layer of general electrode on the back surface. In addition, an electron receiver is also needed to structure the photo-detector. Energy spectrum response at ultraviolet band of this Au coated MCP photo-detector was measured through measuring the response current of the detector between 200~340 nm (3.66~6.22 eV) directly. The selective photoemission of Au has been found, which had been found only for alkali metals.
Organic light-emitting diodes based on bipolar material FLAMB-1T
Lu Li, Junsheng Yu, Zhu Ma, et al.
Organic light-emitting diodes (OLEDs) were fabricated with a structure of indium-tin-oxide (ITO)/poly(Nvinylcarbazole) (PVK): 2-{4-[bis(9,9-dimethylfluorenyl)amino]phenyl}-5-(dimesitylboryl)thiophene (FLAMB-1T)/[tris (8-quinolinolato) aluminum (Alq3) or 2,2',2"(1,3,5-benzenetriyl) tris-(1- phenyl-1Hbenzimidazole) (TPBi)]/Mg : Ag by spin coating method using a bipolar material of FLAMB-1T. Electroluminescent (EL) spectra characteristic was investigated, and the performance differences of the OLEDs were analyzed. Also, the luminance-voltage characteristics of the two devices were compared. The luminances of the devices were 2085 and 4389 cd/m2 at 15.5 V. The maximum power efficiencies of the devices were 0.24 and 4.9 lm/W. The EL spectra were located at 520 and 478 nm with the electron transporting layer of Alq3 and TPBi, respectively. The emitting processes of the device were discussed using energy transfer and direct carrier trapping principle in polymeric material.
Effect of corona poling on structure evolutions of alpha-phase and beta-phase PVDF films
Yingxue Xi, Huiqing Fan, Weiguo Li, et al.
In this work, Static piezoelectric measuring tester was used to examine piezoelectric strain constant variations as function of corona fields; it also introduced XRD experiments were carried out on PVDF films with different corona voltage. Such information may be relevant in identifying changes in the degree of crystallinity and crystalline phase changes that occur during poling process. Complementary information was also obtained by performing differential scanning calorimetry (DSC) studies of the same samples. The results show that the poled films exhibit better piezoelectric properties than non-poled ones due to structural changes during corona poling process. A decrease in the degree of crystallinity is found and better piezoelectric characteristics can be obtained in poled β-phase films. However, the value of piezoelectric strain constant of poled α-phase films was relative lower in comparison with β-phase ones due to existence of a considerable number of non-polar phase content in crystalline region.
Study on the detectivity of the pulsed infrared thermograph
Yan Huo, Hui-juan Li, Yue-jin Zhao, et al.
Infrared thermography as a wide-area, rapid, and noncontact nondestructive testing (NDT) method has been widely recognized for many years. It is based on the thermal wave theory, using different heat source to heat the detected samples, Pulsed Infrared Thermography has emerged as the most widely used form of the technique, through the measurement of the surface temperature, the inside information of the sample can be obtained. However, the detectivity of the Pulsed Infrared Thermography has its limitations, fundamental detectivity of a flaw will depend on its size, depth and the distance between two adjacent flaws. In this paper, the theoretical analysis of detectivity of infrared pulsed thermography and criteria to assess the detectivity are discussed , as well as the theoretical testing limit is given for the Pulsed Infrared Thermography , two related experiments are done, one sample is the aluminum plate with back-drilled rectangle flumes, having six flumes in the same size but different depths, the sample is used as the detectivity reference sample, which is used to analysis the relationship between detectivity of the pulsed infrared system and the characters of a flaw. Meanwhile, a second sample is the Sandwiched structures which are composed by a honeycomb core between two multi-layer carbon fiber reinforced plastic (CFRP) facesheets, the structure is widely used in aerospace nowadays, it has flaws in different sizes, depths and distances between two flaws, the second sample is used to study the influence factors of the detectivity of the Pulsed Infrared Thermography. For the CFRP sample, the detectable size, depth, and distances between the flaws are given as a result. From the two different experiments, detectivity of the Infrared Pulsed Thermograhy has been studied.
CMOS image sensor with contour enhancement
Liya Meng, Xiaofeng Lai, Kun Chen, et al.
Imitating the signal acquisition and processing of vertebrate retina, a CMOS image sensor with bionic pre-processing circuit is designed. Integration of signal-process circuit on-chip can reduce the requirement of bandwidth and precision of the subsequent interface circuit, and simplify the design of the computer-vision system. This signal pre-processing circuit consists of adaptive photoreceptor, spatial filtering resistive network and Op-Amp calculation circuit. The adaptive photoreceptor unit with a dynamic range of approximately 100 dB has a good self-adaptability for the transient changes in light intensity instead of intensity level itself. Spatial low-pass filtering resistive network used to mimic the function of horizontal cell, is composed of the horizontal resistor (HRES) circuit and OTA (Operational Transconductance Amplifier) circuit. HRES circuit, imitating dendrite of the neuron cell, comprises of two series MOS transistors operated in weak inversion region. Appending two diode-connected n-channel transistors to a simple transconductance amplifier forms the OTA Op-Amp circuit, which provides stable bias voltage for the gate of MOS transistors in HRES circuit, while serves as an OTA voltage follower to provide input voltage for the network nodes. The Op-Amp calculation circuit with a simple two-stage Op-Amp achieves the image contour enhancing. By adjusting the bias voltage of the resistive network, the smoothing effect can be tuned to change the effect of image's contour enhancement. Simulations of cell circuit and 16×16 2D circuit array are implemented using CSMC 0.5μm DPTM CMOS process.
CFRP sandwiched facesheets inspected by pulsed thermography
Huijuan Li, Yan Huo, Liangxu Cai, et al.
Carbon fiber reinforced polymer (CFRP) has been always used in aerospace, Sandwiched structures composed by a honeycomb core between two multi-layer CFRP facesheets are very common on aerospace parts. As to the application of the CFRP sandwiched facesheets is extended, The demand for quality control of CFRP sandwiched composites is increasing, Infrared thermography is one of several non-destructive testing techniques which can be used for defect detection in aircraft materials such as carbon-fibre-reinforced composites. Infrared thermography can be potentially useful, as it is quick, real time, non-contact and can examine over a relatively large area in one inspection procedure. The technique is based on heating the sample surface with different heat sources and monitoring the surface temperature of the sample with an IR camera, any abnormal behavior of the surface temperature distribution indicates the subsurface defect. This kind of structure is normally affected by anomalies such as delaminations, disbonding, water ingressing to the core. in this paper, several different kinds of defects which are of various size and depth below the test surface are planted in the CFRP composites, the Teflon inserts between the plies in the facesheet represents the delaminations, the Teflon inserts between the inner facesheet and adhensive or between adhensive and core are simulated disbonding in the composites, they are all tested by pulsed thermography, meanwhile, these samples are also inspected by ultrasonic testing, compare with each characteristic and the results got by these two different methods, it shows that pulsed thermography is an effective nondestructive technique for inspecting CFRP composites.
Design of the data acquisition and real-time imaging system for UIRFPA
Taoli Pan, Guangzhong Xie, Yun Zhou, et al.
This paper presents a useful design of the time-series driving, data acquisition and real-time imaging system for the uncooled infrared focal plane arrays (UIRFPA). The field programmable gate array (FPGA) is used as the central processing unit (CPU) in the system, which can control and harmonize all functional modules. The Ping-Pong structure is employed to realize real-time imaging. The SDRAM is adopted for the data storage to fulfill the need of mass memory. And there are also some switches and keys to provide human-machine interaction. This system works for UIRFPA with resolution of 320×240 steadily and authoritatively. The noise doesn't merge in main signals, so the system can extract the signals of UIRFPA accurately and efficiently.
Modeling of image matching accuracy with image metrics based on least squares matching algorithm
Xi-yang Zhi, Wei Zhang, Fan-jiao Tan, et al.
The determination of conjugate points in a stereo image pair, i.e. image matching, is the critical step to realize automatic surveying and recognition in digital photogrammetric processing. The accuracy of image matching is closely related to specific matching algorithm as well as images. In this paper, the qualitative and quantitative relationships between the matching accuracy and the image metrics are studied at the basic of Least Squares Image Matching algorithm (LSIMA). Firstly, the algorithm is deduced mathematically, and then the main image metrics affecting the matching accuracy are presented, including total variation (TV) metric and difference of signal-to-noise ratio (DSNR) metric. Subsequently, variations of matching accuracy with TV and DSNR are analyzed, and mathematical model between them is developed. Studies show that the matching accuracy presents the natural exponential rule along with TV and DSNR of image pairs. Besides, parameters of the model are estimated and the model is verified by simulation experiments. Finally, the correctness of the model is verified using real remote sensing images. Experimental results demonstrate the robustness and accuracy of the proposed model.
Based on airborne multi-array butting for IRFPA staring imagery
Minjun Mao, Gonghai Xiao, Yancheng Lin, et al.
Because infrared system detects the radiation energy of the target, it has the ability to work all day that the visible-light detection system cannot achieve, at the same time, infrared system is a passive detection system, does not need active detection technology such as radar, which requires large radiation power or a larger expandable antenna. It is more suitable for airborne applications, therefore, infrared imaging based on the aircraft and aerostat platform, has been an important means of monitoring the ground. However, due to detector limitations, the spatial resolution of current infrared cameras or spectrographs and the total field coverage of view are generally not satisfied the customer's requirements. This paper proposes an airborne infrared camera imaging method based on multi-planar arrays, using frame-type imaging array. In order to provide large ground coverage together with good spatial resolution, the mirror is drove to scan rapidly by the galvanometer. The scanning mirror works at staring imagery mode. During multi-planar detectors exposure and imaging, the mirror moves to the staring position. There is more than 10 % overlapping sensor foot prints between two adjacent frames, and the functions of image matching algorithms are used to ensure the seamless butting. This imaging method improves the system integration time, and effectively improves the sensitivity of infrared systems; frame-type imaging solves the serious image distortion caused by the platform attitude.
The design of the high-power semiconductor laser signal transmitter
Na Shen, Xianjing Zhang, Nengdong Wang
The paper mainly focuses on the research of the high-power semiconductor laser signal transmitter. There are two keys in the design: first, the power-driven technology of the high-power semiconductor laser. The paper generates fast current pulse in a low-impedance load by the way of control the pulse length to drive the semiconductor lasers. Second, the information coding techniques based on laser pulses. It is realized in the control of Field-Programmable Gate Array. In additionally, in the optical window design, the system use of inverted telescope lens structure to compress and collimate the laser beam. The specimen achieved the desired performance in experiment.
Study on optical properties of two-color microbolometers
Henan Zhao, Tao Wang, He Yu, et al.
In this article, the practical structure of two-color microbolometers for uncooled infrared detection was considered, a mathematical model to calculate infrared absorptance was described. The optical characteristic of multilayer structure consisting of Nitride (SiNx) infrared absorber film/ Vanadium (VOx) heat sensitive film/ SiNx support film/ the first optical resonant cavity/ a tunable reflecting Al micromirror/ the second optical resonant cavity /a bottom electrode made up of Al was investigated. According to optical admittance matrix theory, relation between infrared absorber film thickness, the first optical resonant cavity of two-color microbolometer and infrared absorptivity was simulated by MATLAB software.
Fast-camera calibration of stereo vision system using BP neural networks
Huimin Cai, Kejie Li, Meilian Liu, et al.
In position measurements by far-range photogrammetry, the scale between object and image has to be calibrated. It means to get the parameters of the perspective projection matrix. Because the image sensor of fast-camera is CMOS, there are many uncertain distortion factors. It is hard to describe the scale between object and image for the traditional calibration based on the mathematical model. In this paper, a new method for calibrating stereo vision systems with neural networks is described. A linear method is used for 3D position estimation and its error is corrected by neural networks. Compared with DLT (Direct Linear Transformation) and direct mapping by neural networks, the accuracy is improved. We have used this method in the drop point measurement of an object in high speed successfully.
Spectrum acquisition of detonation based on CMOS
Yan Li, Yonglin Bai, Bo Wang, et al.
The detection of high-speed dynamic spectrum is the main method to acquire transient information. In order to obtain the large amount spectral data in real-time during the process of detonation, a CMOS-based system with high-speed spectrum data acquisition is designed. The hardware platform of the system is based on FPGA, and the unique characteristic of CMOS image sensors in the rolling shutter model is used simultaneously. Using FPGA as the master control chip of the system, not only provides the time sequence for CIS, but also controls the storage and transmission of the spectral data. In the experiment of spectral data acquisition, the acquired information is transmitted to the host computer through the CameraLink bus. The dynamic spectral curve is obtained after the subsequent processing. The experimental results demonstrate that this system is feasible in the acquisition and storage of high-speed dynamic spectrum information during the process of detonation.
Study on algorithm and real-time implementation of infrared image processing based on FPGA
Yulin Pang, Ruijun Ding, Shanshan Liu, et al.
With the fast development of Infrared Focal Plane Arrays (IRFPA) detectors, high quality real-time image processing becomes more important in infrared imaging system. Facing the demand of better visual effect and good performance, we find FPGA is an ideal choice of hardware to realize image processing algorithm that fully taking advantage of its high speed, high reliability and processing a great amount of data in parallel. In this paper, a new idea of dynamic linear extension algorithm is introduced, which has the function of automatically finding the proper extension range. This image enhancement algorithm is designed in Verilog HDL and realized on FPGA. It works on higher speed than serial processing device like CPU and DSP. Experiment shows that this hardware unit of dynamic linear extension algorithm enhances the visual effect of infrared image effectively.
Calculation of optical band gaps of a-Si:H thin films by ellipsometry and UV-Vis spectrophotometry
Yijiao Qiu, Wei Li, Maoyang Wu, et al.
Hydrogenated amorphous silicon (a-Si:H) thin films doped with Phosphorus (P) and Nitrogen (N) were deposited by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD). The optical band gaps of the thin films obtained through either changing the gas pressure (P-doped only) or adulterating nitrogen concentration (with fixed P content) were investigated by means of Ellipsometric and Ultraviolet-Visible (UV-Vis) spectroscopy, respectively. Tauc formula was used in calculating the optical band gaps of the thin films in both methods. The results show that Ellipsometry and UV-Vis spectrophotometry can be applied in the research of the optical properties of a-Si:H thin films experimentally. Both methods reflect the variation law of the optical band gaps caused by CVD process parameters, i.e., the optical band gap of the a-Si:H thin films is increased with the rise of the gas pressure or the nitrogen concentration respectively. The difference in optical band gaps of the doped a-Si:H thin films calculated by Ellipsometry or UV-Vis spectrophotometry are not so great that they both can be used to measure the optical band gaps of the thin films in practical applications.
Research on infrared image enhancement algorithm based on histogram
Jie Zhang, Ziji Liu, Yanzhao Lei, et al.
Infrared image often has the defects of low contrast and high dynamic range. Image enhancement technology is very important for infrared images. In this paper, several methods were introduced to improve the quality of infrared images. At first, images from IRFPA must be pre-processed by the algorithm of blind compensation and non-uniformity correction (NUC). Then, the image was enhanced by the algorithm of direct gray scale transformation and plateau equalization (PE). The quality of the image was enhanced effectively. However, the noise was also amplified. At last, the image noise was suppressed by using median filter. The experiment result indicates that infrared image enhancement algorithm can not only enhance image contrast effectively but also keep the detail information of original infrared image well.
Design of SOPC-based infrared image enhancement system
Yanzhao Lei, Zhiming Wu, Ziji Liu, et al.
On the basis of the brief introduction to theory of uncooled infrared thermal imaging system and the infrared image processing algorithms, the key technologies to real-time image enhancement was studied, which driving a 160×120 Infrared Focal Plane Arrays (IRFPA) imaging system. In this article, an uncooled infrared thermal imaging system with real-time image processing and image enhancement was designed and developed, most importantly, a better result was achieved. Aiming at the Infrared Focal Plane Arrays (IRFPA), the hardware system used flexible design approach and efficiently developed tools on System-on-a-Programmable-Chip(SOPC)with two SDRAMs memories used as frame buffers. By this means, the 160 × 120 of IRFPA realized image acquisition. In this article, the structure of the system and the software realization of infrared images to achievement of the non-uniformity correction and image enhancement algorithm for parallel operation On the SOPC were described in details.The results showed that the design of SOPCbased real-time infrared image processing system could simplify system hardware and software design while ensuring the computing abilitiy. To the IRFPA imaging system of 160 × 120, processed infrared image quality was improved significantly to meet the real-time dynamic detection and tracking needs. Finally a system of uncooled infrared thermal imager with high price quality and convenient reconfiguration condition was implemented.
Simulation and analysis of ACB'S photometric signature based on STK
Liangliang Zhang, Debao Ma, Chaoyang Niu
The basic theory of observations on ACBs' photometric signature is studied in this paper. A ground-based opto-electrionic observation emulation method with STK and MATLAB is presented to solve the problem that the real space observation is hardly run under the condition of technology institute. A spatial object brightness change model is established in combination of blackbody radiation theory. The photometric characteristics of space object are then analyzed using the above model by the simulation platform. Respectively, a low-orbit satellite and a tumbling rocket are simulated. The desired results are achieved by analysing brightness changes of the targets on various operating.
980-nm 14-pin butterfly module dual-channel CW QW semiconductor laser for pumping
Yun Deng, Changling Yan, Yi Qu, et al.
Nowadays, with its mature progress, the 790 nm - 1000 nm wavelength semiconductor laser is widely used in the fields of laser machining, laser ranging, laser radar, laser imaging, laser anti-counterfeit, biomedical and etc. Best of all, the 980 nm wavelength laser has its widespread application in the pumping source of Er3+ -doped fiber amplifier, optic fiber gyroscopes and other devices. The output wavelength of the fiber amplifier which takes the 980 nm wavelength laser as its pumping source is between 1060 nm and 1550 nm. This type of laser has its extremely wide range of applications in optical communication and other fields. Moreover, some new application domains keep constantly being developed. The semiconductor laser with the dual-channel ridge wave guide and the 980 nm emission wavelength is presented in this paper. In our work, we fabricated Lasers with the using of multi-quantum well (MQW) wafer grew by MBE, and the PL-wavelength of the MQW was 970 nm. The standard photofabrication method and the inductively coupled plasma (ICP) etching technology are adopted in the process of making dual-channel ridge wave guide with the width of 4 μm and height of 830 nm. In the state of continuous work at room temperature, the laser could output the single mode beam of 70 mW stably under the current of 100 mA. The threshold current of the laser diode is 17 mA and the slope efficiency is 0.89 W/A. The 3 dB spectrum bandwidth of the laser beam is 0.2 nm. This laser outputs its beam by a pigtail fiber on which Bragg grating for frequency stabilization is carved. The laser diode, the tail fiber, and the built-in refrigeration and monitoring modules are sealed in a 14-pin butterfly packaging. It can be used directly as the pumping source of Er3+ - doped fiber amplifier or optic fiber gyroscopes.
Underwater object detection technology based on polarization image fusion
Yongguo Li, Shiming Wang
The performance of the traditional underwater optical imaging systems is ultimately limited by the absorption and scattering properties of the water substance. Polarimetric imaging can be used to remove degradation effects, and can be applied to high-level vision tasks, such as object classification and recognition and camouflage identification, etc. The method of improving contrast was presented by polarization imaging. The polarization images when the angle of polarization are 0°, 45°, 90° and 135°, the gray levels of the images are calculated by program. There are much complementary and redundancy information among the polarization images. According to the character of parameter I of stokes vector, degree of linear polarization (DoLP) and the angle of polarization (AoP), A RGB false color based polarimetric images fusion are given to enhance the contrast.
X-ray integrated digital imaging system based on a-si flat panel detector
Jian Fu, Bin Li, Baihong Jiang
X-ray phase contrast imaging (X-PCI) is one of the novel imaging methods. For the low density substance, it provides better images than the conventional X-ray attenuation imaging. In order to get a high-quality image, X-PCI adopts the high spatial resolution image intensifier as the detector. However, the X-ray attenuation imaging usually adopts the high sensitivity a-si flat panel detector (FPD) as the detector. So it is currently one of the questions in the field of X-ray imaging how to realize these two functions at a system: X-ray attenuation imaging and X-PCI. An X-ray integrated digital imaging system based on FPD is designed and developed after analyzing the imaging principle of X-PCI and the imaging feature of FPD. The results from simulation and experiments in this system show that the X-PCI image can be acquired without affecting the quality of the conventional X-ray attenuation image. It demonstrates the possibility to realize these two functions at a system.
Application of stimulated rotational Raman scattering technique in NO2-DIAL system
Dawei Fang, Ben Xu, Kai Yang, et al.
Differential Absorption Lidar (DIAL) for detecting atmospheric pollution is used extensively for its high precision and spatial resolution. The selection of the suitable absorption wavelength and the stimulation and modulation of the corresponding laser source are of key importance for DIAL system. This literature presents first a new approach for attaining the specific absorption wavelength in design of the new type NO2-DIAL. The third harmonic of Nd:YAG laser itself is taken as the selected λon (354.7 nm), and is converted to the circularly or elliptically polarized laser to pump the D2 Raman cell, acquiring plentiful frequency spectrum of stimulated vibrational and rotational Raman scattering light, among which the first-order pure stimulated rotational Raman scattering light nearest to the pumping laser wavelength is taken as the λoff (359.9 nm) for DIAL. The polarization state of the pumping laser can be conveniently modulated by using a λ/4 wave-plate. It is of large advantages in raising the technical performance and the economical efficiency. The technique will be very useful for DIAL to detect other constituents of atmospheric pollution.
Research on detection characteristics test method for infrared detector in low temperature background
Shitao Wang, Wei Zhang, Qiang Wang
In research fields such as infrared astronomical observation and space fragments distribution analysis etc, the first and possibly the most critical evaluation parameter of interest is detection sensitivity. Without adequate detection sensitivity, it is impossible for infrared detector to detect the target at a distance great enough and play the role of terminal detector of background. Although cryogenic optical system can be employed for the aim of increasing detection sensitivity up to the possible maximum extent, research on detection characteristics test method for infrared detector in low temperature background must be undertaken primarily before the cryogenic optical system is designed and manufactured. In this paper, some of the fundamentals of detection characteristics test method are presented, and a set of experimental apparatus is designed and established. Based on this apparatus and by employing an extend plane source blackbody, the general rule of detection characteristics of infrared detector from normal temperature background to low temperature background are investigated. The voltage-output signals of every pixel are continuously acquisitioned for F (≥100) frames under two different blackbody temperatures, and as a result we obtain the evolving regularity of different performance index, e.g. limiting integration time and detectivity D*. The measurement results reported in the paper confirm that the integration time can be improved by a large margin in comparison with normal temperature background, and the specific detecivity D* has the same variation tendency, which can be increased up to one order of magnitude.
Iterative blind image restoration with ringing reduction
Ju-feng Zhao, Hua-jun Feng, Zhi-hai Xu, et al.
Image restoration is one of the most important problems in image processing. It is extremely difficult to obtain the accurate PSF (Point Spread Function) of the degraded image captured from imaging system, so the method of iterative blind deconvolution which is superior to the other ones is adopted. In blind image restoration, the estimation of initial PSF plays a significant role. Meanwhile, with the increase of the number of iteration, ringing ripples may appear at boundary and the regions where gray values vary severely, which affects the quality of the restored image. Therefore, estimation of initial PSF and ringing reduction are two primary problems in blind iterative image deconvolution. A novel approach combined the estimation of initial PSF with ringing suppression in blind iterative restoration is proposed. First, a sophisticated variational Bayesian inference algorithm with natural image statistics is used to estimate initial PSF. Cyclic boundary method is applied to suppress the ringing artifact at the boundary. As to the ringing in areas near edges, spatial weighted matrix is adopted, because spatial weighted matrix can impose an adaptive local constraint on restoration and smoothing to achieve better results. Finally, image quality assessment is used to evaluate the restored image, which also could agree with human visual system. Experiments of simulation and real images show that this approach can restore boundary and edge areas well and reduce the noise in smooth regions, which means that this method can suppress ringing ripples and preserve more details validly.
Monte Carlo simulation of detecting space debris with lidar
Shengliang Fang, Yuhua Fu, Zhen Li
On the basis of analysis and processing of space background radiation, the article gives the detection probability when the lidar detecting space debris, and compare the random variable which is produced by Monte Carlo method with the detection probability, then get the detection results. The results reveal that, the detection model can well reflect the impact of the random variable such as characteristics of the noise fluctuations in the detection process.
Nondestructive testing of rocket engine injector panel using ultrasonic burst phase thermography
Dapeng Chen, Cunlin Zhang, Naiming Wu, et al.
As the key parts of the liquid rocket oxyhydrogen engine, the injector panel is a kind of transpiration material, which is braided and Sintered with stainless steel wire. If some hidden delaminition defects that are difficult to detect appear in the process of Sintering and rolling, a significant safety problem would occur. In this paper, we use the Ultrasonic Burst Phase Thermography (UBP) to detect the delamination defects in the injector panel, UBP is a rapid and reliable nondestructive technique derived from Ultrasonic Lock-in Thermography(ULT). It uses a controllable, adjustable ultrasonic burst as the heat source to stimulate the sample, the defects within the material are revealed through their heat generation caused by friction, clapping and thermoelastic effect, as the resulting surface temperature distribution is observed by an infrared camera. The original thermal images sequence is processed by Fast Fourier Transformation to obtain the phase information of the defects. In the experiments of the delamination sample, the UBP realized the selective heating of delamination defects in the injector panel, and the signal to noise of phase image is higher than the original thermal image because the phase information can not be disturbed by the initial conditions (such as the reflective surface of sample). However, the result of the detection of flat bottom hole transpiration panel sample reflects that UBP is not appropriate for the detection of this kind of defects, because it is difficult to induce frictional heating of flat bottom holes. As contrast, Flash Pulse Thermography is used to detect the flat bottom holes, all of the holes of different depth and sizes can be seen distinctly. The results show that PT is more appropriate for the detection of flat bottom holes defects than UBP, therefore, it is important to select the appropriate excitation method according to different defects.
High-speed motion-blurred image restoration based on blind deconvolution
Lixin Liu, Rong Xu, Ganhua Li, et al.
Due to camera vibration, target motion, atmospheric turbulence and the other factors, the received image is degraded severely in the process of tracking and measurement of high-speed flight aircraft in the atmosphere. Aiming at this problem, optimization of blurred image restoration is proposed based on a blind deconvolution restoration method. This method estimates the direction of point spread function (PSF) in the frequency domain at first, and then estimates the size of PSF by autocorrelation, and finally restores the degraded image by iteration on the appropriate constraint and convergence conditions. The analysis of experimental results show that the method could reduce the phenomenon of the image blur and ringing caused by the uncertainty site of PSF in the process of blind deconvolution and make the system of measurement more precisely and effectively.
A hyperspectral images compression algorithm based on 3D bit plane transform
Lei Zhang, Libin Xiang, Sam Zhang, et al.
According the analyses of the hyper-spectral images, a new compression algorithm based on 3-D bit plane transform is proposed. The spectral coefficient is higher than the spatial. The algorithm is proposed to overcome the shortcoming of 1-D bit plane transform for it can only reduce the correlation when the neighboring pixels have similar values. The algorithm calculates the horizontal, vertical and spectral bit plane transform sequentially. As the spectral bit plane transform, the algorithm can be easily realized by hardware. In addition, because the calculation and encoding of the transform matrix of each bit are independent, the algorithm can be realized by parallel computing model, which can improve the calculation efficiency and save the processing time greatly. The experimental results show that the proposed algorithm achieves improved compression performance. With a certain compression ratios, the algorithm satisfies requirements of hyper-spectral images compression system, by efficiently reducing the cost of computation and memory usage.
Dim-small-targets detection based on higher-order cumulant and wavelet method
Gang Liu, Rong-hui Wang, Qi Wang
A novel two-dimensional (2-D) adaptive filtering algorithm to enhance 2-D signals of small spatial extent embedded in white Gaussian noise and a variety of outstanding modern digital signal processing methods are combined in background segmentation. The coefficients of the adaptive filter converge to a special 2-D slice of the fourth-order cumulant function of the input signal. The proposed algorithm is called the 2-D cumulant adaptive enhancer (2DCAE). And the methods in background segmentation is combining the wavelet energy transformation, data integration and threshold segmentation.
High-speed SPGD wavefront controller for an adaptive optics system without wavefront sensor
Caixia Wang, Xinyang Li, Mei Li, et al.
A non-conventional adaptive optics system based on direct system performance metric optimization is illustrated. The system does not require wave-front sensor which is difficult to work under the poor condition such as beam cleanup for the anomalous light beam. The system comprises a high speed wavefront controller based on Stochastic Parallel Gradient Descent (SPGD) Algorithm, a deformable mirror, a tip/tilt mirror and a far-field system performance metric sensor. The architecture of the wave-front controller is based on a combination of Field Programmable Gate Array (FPGA) and floating-point Digital Signal Processor (DSP). The Zernike coefficient information is applied to improve the iteration speed. The experimental results show that the beam cleanup system based on SPGD keep a high iteration speed. The controller can compensate the wavefront aberration and tilt excursion effectively.
Joint transform correlator based on CIELAB model with encoding technique for color pattern recognition
Tiengsheng Lin, Chulung Chen, Chengyu Liu, et al.
The CIELAB standard color vision model instead of the traditional RGB color model is utilized for polychromatic pattern recognition. The image encoding technique is introduced. The joint transform correlator is set to be the optical configuration. To achieve the distortion invariance in discrimination processes, we have used the minimum average correlation energy approach to yield sharp correlation peak. From the numerical results, it is found that the recognition ability based on CIELAB color specification system is accepted.
Study the encountering simulation system for laser fuze based on intensity attenuation and fiber delay
Laser fuze is a kind of proximity fuze developed with laser technology. A encountering simulation system for laser fuze based on environment simulator and fiber retarder is introduced in this paper. The system can simulate the process for the laser fuze to approach the target quickly, with consideration of changing light path and intensity caused by factors like environment and distance. It can be a reference for the future design of laser fuze.
The energy coupling between two chiral waveguides
Jiaqun Zhao, Ping Cheng, Junqing Li
We discuss the coupling properties in isotropic chiral waveguides. By using Lorentz reciprocity theorem, we obtain a set of coupled linear equations for left- and right-circularly components in isotropic chiral waveguides. From the equations, the light propagation properties in chiral waveguides are obtained. The numerical results show that all the energy in one chiral waveguide can be completely converted into another at special position in coupling region. The energy coupling between two chiral waveguides can be use to design novel optical devices.
Wave-shaping and engineering realization of CCD driving signals
Yan Wang, Tao Li
High-speed driving signals will easily incur the substrate bounce of CCD(charge-coupled device), causing the charge transfer of CCD, which not only reduces the charge transfer efficiency but also produces dispersion. Thus the CCD imaging quality will be severely influenced. This paper introduces the classification and work principle of driving signals and elaborates the mechanism of the occurrence of the substrate bounce of CCD. Taking the characteristics of high speed driving signals into consideration, the paper provides a method to restrict the substrate bounce's disturbance to CCD signals based on the driving signal wave-shaping theory. Theoretically speaking, the driving signal wave-shaping theory may effectively restrict the substrate bounce of CCD. Moreover, the circuit simulation proves the correctness of the theory. After the wave-shaping process to CCD driving circuits, the test results of CCD signals obviously excel those without wave-shaping. The circuit test also shows that the substrate bounce's disturbance to CCD signals is effectively restricted. The test proves the feasibility of the engineering about wave-shaping, providing a scientific theory for the focal plane high-speed driving circuit design in the future.
Timing generator of scientific grade CCD camera and its implementation based on FPGA technology
Guoliang Si, Yunfei Li, Yongfei Guo
The Timing Generator's functions of Scientific Grade CCD Camera is briefly presented: it generates various kinds of impulse sequence for the TDI-CCD, video processor and imaging data output, acting as the synchronous coordinator for time in the CCD imaging unit. The IL-E2TDI-CCD sensor produced by DALSA Co.Ltd. use in the Scientific Grade CCD Camera. Driving schedules of IL-E2 TDI-CCD sensor has been examined in detail, the timing generator has been designed for Scientific Grade CCD Camera. FPGA is chosen as the hardware design platform, schedule generator is described with VHDL. The designed generator has been successfully fulfilled function simulation with EDA software and fitted into XC2VP20-FF1152 (a kind of FPGA products made by XILINX). The experiments indicate that the new method improves the integrated level of the system. The Scientific Grade CCD camera system's high reliability, stability and low power supply are achieved. At the same time, the period of design and experiment is sharply shorted.
128×128 dual-color ROIC with electrical crosstalk resistant design
Wei Lu, Ruijun Ding, Xiaoyang Liu, et al.
Dual-color(MWIR/SWIR)infrared focal plane array with sequence integration mode. It can export two bands photocurrent signal under irradiation. In order to deal with the signal electrical crosstalk problem which the unstable and large variant bias voltage of N-P+-N HgCdTe infrared detectors bring while two bands switch, A novel modified DI (MDI)circuit structure based on adjusting the bias voltage is presented. Through controlling timing sequence, MWIR and SWIR signal are integrated in turn and readout at the same time. The chips of 128×128 ROIC are designed and fabricated with 0.6 um double poly double metal mixed signal technology. The simulation shows right function of the circuit. Power dissipation of analog module is 20 mW, that of digital module is 10.25 uW and it has been tapped out.
A CMOS transimpedance amplifier for pulsed laser range finder
Yi Chen, Genghua Huang, Rong Shu, et al.
The pulsed laser range finding has been extensively applied in space exploration, military use and industry, due to its advantages over other methods of non-contact ranging in simplicity, non-cooperativeness of objects, long detecting range and short range acquisition time. The integration of its receiver channel will be beneficial to weight-lightening, miniaturization and mass production of the laser range finder. A transimpedance amplifier for receiver channel of pulsed range finder is designed using 0.6-μm CMOS technology in this work. It consists of transimpedance pre-amplifier, R-2R resistors ladder variable attenuator and post-amplifier. A regulated cascade circuit (RGC) is used to isolate the input capacitor from input node of transimpedance pre-amplifier, reducing the bandwidth suppression caused by large input capacitor. R-2R variable attenuator is implemented for digital gain control, achieving a total gain control range of 42dB with 7 steps and 6dB per step. Simulation shows that the circuit achieves a bandwidth of 83 MHz with the presence of a 5-pF input capacitor, and a maximum transimpedance of 125.5dBΩ, meeting the requirement of high-precision pulsed laser range finder.