Proceedings Volume 6835

Infrared Materials, Devices, and Applications

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Proceedings Volume 6835

Infrared Materials, Devices, and Applications

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Volume Details

Date Published: 5 November 2007
Contents: 10 Sessions, 67 Papers, 0 Presentations
Conference: Photonics Asia 2007 2007
Volume Number: 6835

Table of Contents

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Table of Contents

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  • Front Matter: Volume 6835
  • Infrared Materials/Devices and Their Application I
  • Infrared Materials/Devices and Their Application III
  • Infrared Materials/Devices and Their Application IV
  • Infrared Materials/Devices and Their Application V
  • Infrared Imagers/Systems and Their Application I
  • Infrared Imagers/Systems and Their Application II
  • Infrared Imagers/Systems and Their Application III
  • Infrared Imagers/Systems and Their Application IV
  • Poster Session
Front Matter: Volume 6835
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Front Matter: Volume 6835
This PDF file contains the front matter associated with SPIE Proceedings Volume 6835, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.
Infrared Materials/Devices and Their Application I
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New architecture for TECless operation of uncooled microbolometers developed at LETI
Thermal imaging market is today more and more attracted by systems with "instant-on" and low power consumption. "TECless" operation of uncooled microbolometer detectors, that is where no Peltier module is needed, is one of the major features required by the market. In order to fulfill this demand, LETI/SLIR is developing and optimizing a new IRCMOS architecture based on a differential reading implemented with current mirrors. This design simultaneously reduces focal plane temperature sensitivity and simplifies the detector driving. An IRCMOS prototype (320 × 240 with a pitch of 25 μm) has been designed, processed, and characterized. This paper presents an overall view of this new design and the latest characterization results of the prototype.
New concept system research and development base on advanced infrared detector
Quanxin Ding, Hua Liu
Case analysis is used on multi spectrum infrared detector technique, cooled infrared detector technique, uncooled infrared detector technique, and quantum well infrared detector and so on, especially on their function and station in system lay. Mainly refer to system characteristics, key technique, key optical system structure, and infrared detector application on system characteristics. Infrared system base on great scale focal plane array (FPA) detectors and super spectral remote sensing is expatiated, and the research solutions and results are evaluated and demonstrate that the testing and evaluation technique is the key technique and one of the main industry.
256x1 element linear InGaAs short wavelength near-infrared detector arrays
Xue Li, Hengjing Tang, Guangyu Fan, et al.
256×1 element linear InGaAs detector arrays assembly have been fabricated for the short wave infrared band(0.9~1.7μm), including the detector, CMOS readout circuits, thermoelectric cooler in a sealed package. The InGaAs detectors were achieved by mesa structure on the p-InP/i-InGaAs/n-InP double hetero-structure epitaxial material. 256×1 element linear InGaAs detectors were wire-bonded to 128×1 element odd and even ROIC, which were packaged in a dual-in-line package by parallel sealing. The characteristics of detectors and detector arrays module were investigated at the room temperature. The detector shows response peak at 1.62μm with 50% cutoff wavelength of 1.73μm and average R0A with 5.02KΩ•cm2. Response non-uniformity and average peak detectivity of 256×1 element linear InGaAs detector arrays are 3.10% and 1.38×1012cmHz1/2/W, respectively.
Performance analysis of 256 element linear 2.4µm InGaAs photovoltaic detector arrays
In this work, the performance of InxGa1-xAs photovoltaic detectors with cutoff wavelength of 2.4μm(x=0.78) were investigated. The detector arrays were fabricated using gas source molecular beam epitaxy (GSMBE) grown material and arranged in linear arrays of 256 pixels of 56×56μm2 dimension. The transition of the large lattice mismatch (1.6%) between the substrate and the absorption layer was dealt with a linearity transformation InxGa1-xAs buffer layer. The dark-current performance achieved is as low as 10-10A at 300K and a bias voltage of -0.5V. This corresponds to a figure of merit for detector resistance R0 times detector pixel area A of R0A =3.5~7.5Ωcm2 at 300K and quantum efficiency above 60%. Room temperature D*(λp) values beyond 3×1010cmHz1/2W-1.
Infrared Materials/Devices and Their Application III
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Near-infrared photodetectors based on mercury indium telluride single crystals
Xiaolei Zhang, Weiguo Sun, Zhengxiong Lu, et al.
Attempt to form the Schottky barrier on mercury indium telluride (MIT) surface by deposition transparent conducting electrode (TCE) and avoid the negative results by non-rectifier contacts nature, we have investigated the oxidation of clean MIT surfaces to form an insulating layer to overcome this disadvantage by metal-insulator-semiconductor (MIS) photodetectors designing. Oxide film is grown on the MIT surface by plasma enhance chemical vapor deposition (PECVD). Previously cleaned MIT wafers were dipped and boiled in solution, which consists of mixture of bromine and an organic solvent in ratio of 1:50. By the way of using these films as intermediate slightly conducting insulator, a fast-response MIT based surface-barrier photodetectors have been developed. Pt films were used as TCE frontal electrode by vacuum magnetron sputtering (VMS). The current-voltage characteristic is described quantitatively based on the energy diagram and the found parameters of the Schottky barrier. Details of oxidation process, Schottky diodes, as well as the photodetectors fabrication and characterizations are discussed.
Performance and reliability characteristic of Stirling cryocoolers
With extensive application of infrared detective techniques, Stirling cryocoolers, used as an active cooling source, have been developed vigorously in China. An overview of the status and performance for some Stirling cryocoolers having been developed is presented. To analyze the cooler's reliability characteristic, failure analysis has been done, and the four crucial failure modes affecting cooler's long-life running are wear, gaseous contamination, Helium leakage and fatigue. According to each failure mechanism, the measures taken to control or minimize its damage were discussed, and some experiments were designed and carried to quantitatively analyze the relationship between failure and performance in detail. To the wear, an ageing test, which was thermal cycle and for about 500 h, was used to improve the internal frication status and eliminate the defective products. To the gaseous contamination, an accelerated experiment was carried by adding contaminants to the cooler by a 3-way valve to get the relationship between performance degradation and amount of contaminants. The chance of a fatigue related failure is very small now because of the FEM analysis and screening test. Based on charge pressure experiment results, the criteria to judge the sealing procedure was given by the ratio of leak rate to cooler volume.
Spatial light modulator based on sheared polymer network liquid crystal
A kind of spatial light modulator using sheared polymer network liquid crystal (SPNLC) is presented. The SPNLC shows a fast response and weak thickness dependency. The SPNLC cell is fabricated by exposing the mixture of E7 liquid crystal and monomer NOA65 under ultraviolet light. A sheared force is applied to the cell to align the liquid crystal domains, decreasing response time and reducing light scattering. A SPNLC sample of d=13μm with about 3ms response time was measured at λ=632.8nm. For another sample of d=20μm reflective infrared spatial light modulator using SPNLC, when the black body of readout radiation was 600°C, response time with about 8ms at λ=10.6μm and the maximum difference in temperature with more than 80°C at 8~14μm were measured.
Properties of Au/Pt/Ti contact to p-InP by rapid thermal processing
Yanqiu Lv, Hengjing Tang, Bing Han, et al.
We found that the contact resistance of Au/Pt/Ti on p-InP increases with the increase of annealing time and annealing temperature. Au/Pt/Ti is ohmic contact metal as deposited with specific contact resistance of 2.49×10-3 Ωcm2 when p-InP doped by 7.5×1018 cm-3 and is Schottky contact when doped by 2×1018 cm-3. Surface morphologies of Au/Pt/Ti after rapid thermal processing (RTP) were analyzed by atom force microscopy (AFM). An interface layer dominated by TiIn compound, which increase the specific contact resistance, was found in Auger electron spectroscopy (AES) analysis. P-InP and n-InP ohmic contacts can be achieved at the same time as deposited when added p-In0.53Ga0.47As layer on p-InP/InGaAs/n-InP without annealing.
A novel vibration control system for Stirling cryocoolers
Baoyu Yang, Yinong Wu, Yajie Tang, et al.
Vibration generated by mechanical cryocoolers has long been identified as a critical issue for space infrared application, for it can degrade the resolution and pointing accuracy of precision instruments. A simple and effective vibration control system based on momentum cancellation has been developed to actively attenuate the vibration of our Stirling cryocooler. The cryocooler expander module consists of a displacer and an electromagnetically driven actuator, which are mechanically placed in a back-to-back configuration. The transfer function of actuator has been solved, based on that result, novel analogue control electronics has been designed to modulate the displacer displacement signal and drive the actuator, so the moving parts of actuator and displacer can move in opposite direction to reduce the vibration force. With this system, the fundamental vibration of expander is reduced by a factor of more than 40 dB without exaggerating other harmonic components; the power consumption is only less than 0.5W without control electronics. The system has achieved the general vibration requirement of space application and has been applied to our products.
Infrared Materials/Devices and Their Application IV
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Uncooled amorphous silicon 160 x 120 IRFPA with 25 um pixel-pitch for large volume applications
This paper reviews the specifications and performances of a 160 × 120 uncooled infrared focal plane array made from amorphous silicon microbolometers with a pixel-pitch of 25 μm, integrated into a LCC TEC-less package. This detector has been specifically designed for large volume production, while keeping the main features of high end developments, at detection pixel level, as well as at ROIC level, like detector configuration by serial link in order to minimize the number of electrical inputs, low power, large dynamic range...) The main particular features of this achievement are the miniaturized very low weight package, along with easy TEC-less operation naturally afforded via the readout architecture, which leads to very low consumption levels, making it well adapted to low end hand held or helmet mounted thermal imaging cameras. We present in the last part of this paper the main electro-optical characteristics and TEC-less operation, demonstrating wide thermal dynamic range and low power, thanks to the simple single-level amorphous silicon technology, coupled with advanced ROIC design.
Innovative on-chip packaging applied to uncooled IRFPA
Geoffroy Dumont, Agnès Arnaud, Pierre Imperinetti, et al.
The Laboratoire Infrarouge (LIR) of the Laboratoire d'Electronique et de Technologie de l'Information (LETI) has been involved in the development of microbolometers for over fifteen years. Two generations of technology have been transferred to ULIS and LETI is still working to improve performances of low cost detectors. Simultaneously, packaging still represents a significant part of detectors price. Reducing production costs would contribute to keep on extending applications of uncooled IRFPA to high volume markets like automotive. Therefore LETI develops an onchip packaging technology dedicated to microbolometers. The efficiency of a micropackaging technology for microbolometers relies on two major technical specifications. First, it must include an optical window with a high transmittance for the IR band, so as to maximize the detector absorption. Secondly, in order to preserve the thermal insulation of the detector, the micropackaging must be hermetically closed to maintain a vacuum level lower than 10-3mbar. This paper presents an original microcap structure that enables the use of IR window materials as sealing layers to maintain the expected vacuum level. The modelling and integration of an IR window suitable for this structure is also presented. This zero level packaging technology is performed in a standard collective way, in continuation of bolometers' technology. The CEA-LETI, MINATEC presents status of these developments concerning this innovating technology including optical simulations results and SEM views of technical realizations.
Design and simulation of a 512×1 readout circuit for focal plane array
Yaoqiao Li, Hui Zhu, Xue Li, et al.
A CMOS 512×1 readout integrated circuit (ROIC) for an IR focal-plane-array (FPA) has been designed. The pixel pitch is 25um. The input stage is the capacitance trans-resistance amplifier (CTIA) and a correlated double sampling (CDS) circuit is included in each unit. In order to avoid the waste of the threshold voltage in the process of sampling, a matched CMOS sample switch was used in CDS. The simulation results show that, if the output voltage of the preamplifier decreases during the integration process, using pMOS source follower can achieve the maximal output swing. Since the 512 elements shared one output channel, the readout rate was limited due to the large capacitance at the output node. So an off-chip changeable resistance was chosen as the load of the source follower to balance the gain and speed. The timing diagram of the driving signals was presented and discussed. Finally, the simulation results are presented, using Cadence spectreS. The saturated differential output swing is 2.1V at 1MHz pixel readout rate, under the condition of 2.5V reference voltage and a 10k Ω load.
The formation and elimination of inclusions in CdZnTe crystal
Cadmium zinc telluride(CdZnTe) crystals are widely used in the fabrication of γ-ray detectors and IR focal plane arrays(IRFPA). But the existence of the inclusion defects in the materials have limited performances and yield of the detectors for quite long time. So it is very important and emergent to study the characteristic of the inclusion in CdZnTe crystal and how to suppress them. In this paper, the distribution characteristic of inclusion densities in the CdZnTe Crystal were described by the IR-transmission microscope technique. And the sizes and densities of the inclusions were found to be relative with the melt stoichiometry and cooling process of the growth. It was also found that the post-annealing of CdZnTe samples can eliminate the inclusions by the element complementarity under the action of thermal drive. In order to investigate the origin of the inclusions, a quick cooling growth experiment was completed by quenching the ampoule into the water. The result showed that there isn't any inclusion in the region of the material where the material grows in very fast growth rate. But the transmissivity of the material has an obvious decrease in long wave band. This means that a great deal of point defects generate instead of the form of the inclusions. The mechanism to form the inclusions has been analyzed based on the above mentioned phenomena and the phase diagram of CdZnTe. Then it can be indicated that the controls of the melt stoichiometry and cooling process of the growth are the two main factors to eliminate the inclusions of CdZnTe materials.
Infrared Materials/Devices and Their Application V
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Analysis of the thermal stress of IRFPA assembly using FEM
Haiyan Zhang, Huajie Lu
Thermal stress is a common problem as for the cryogenic IRFPA (Infrared Focal Plane Array) Assembly, especially when the assembly is in large scale. The stress is generated when the assembly enduring times of temperature cycling ranging from 80K to 300K approximately. This huge temperature change and the mismatch of the CTE (coefficient of thermal expansion) between these materials by which the assembly is made results in severe thermal stress in the IRFPA. This thermal stress is the main reason for the failure of assembly during temperature cycling such as the degradation of device performance and even the die crack. To improve the reliability of the FPA assembly reducing the thermal stress becomes a more important issue. This article presents several results of the analysis of the thermal stress of IRFPA assembly using FEM (Finite Element Method). According to this result we have got an optimal design of the assembly structure.
The device for observing the solar on moon in multispectrum
Gang Huang, Qirong Xiao, Chao Zheng, et al.
In the thesis we introduce the basic design of the solar multi-spectrum telescope and imaging system. The whole system consists of Cassegrainian reflecting telescope, light-splitting system, light-filtering system, photo emissive detector group, calibration spectroscopy system and solar UV light source Simulated in order to image solar UV radiation, visible light and infrared band respectively and get video. The catadioptric parts of our system guarantee to image the three spectrums at the same time. There are turntable filter group before the detectors to achieve visible and ultraviolet band of more specific band imaging. Spectrophotometry system uses germanium spectroscope and spectrophotometry plane mirror to let the infrared and visible light through. And we coat spectroscope and spectrophotometry plane mirror UV-reflective film to achieve UV reflectance spectrophotometry. At last, we get real-time video image in three specific spectrums in a coaxial optical system. Since working in space for some time, the external factors will lead to our system to produce the spectrum of radiation drift. Therefore we add radiation calibration spectra to the system which provide a standard spectral radiation parameters to provide the detected result with a reliable reference data standard.
The electronic structure of the PbS(-100) with vacancy defect: first-principles study
Zong-ling Ding, Huai-zhong Xing, Yan Huang, et al.
Electronic properties of both Pb and S vacancy defect in PbS(-100) have been studied using the first principles density functional theory (DFT) calculations with the plane-wave pseudopotentials. The densities of states are computed to investigate the effect of the Pb and S vacancy on the electronic structure, respectively. In the case of S vacancy defect, the Fermi energy shifted to the conduction band making it an n-type PbS (donor). While in the case of Pb vacancy the DOS do change appreciably.
Generation of ultrashort mid-infrared pulses by super continuum seeded OPA in a MgO: LiNbO3 crystal
Ying Deng, Qi-hua Zhu, Xiao-ming Zeng, et al.
A type I phase matching MgO:LiNbO3 optical parametric amplification (OPA) system were demonstrated. The OPA system was synchronously seeded with a super continuum and pumped by a laser pulse of 1Hz, 55fs, 3.5mJ, centered at 812nm. The super continuum was got by a sapphire plate and the MgO:LiNbO3 crystal which was 30mmx30mmx15mm in size. In order to avoid the three waves' temporal walk-off, pump wavelength and seeded signal wavelength were tuned simultaneously in simulation, and the result was that it can't be avoided in the collinear phase matching OPA. For the purpose of compensating the group velocity's mismatching, the non-collinear phase matching was adopted, then the non-collinear angles and the best amplified signal wavelengths which changing with the pump wavelengths were also optimized in numerical simulation for the non-collinear phase matching OPA. As a result, pulse energy of as much as 126uJ was achieved at wavelengths ranging from 3.2μm to 4.3μm.
Progress in cooled IR detectors and new developments
Philippe Tribolet, Michel Vuillermet
Cooled IR detectors are produced at mass production level at Sofradir for years based on its mature and proven HgCdTe technology. However, following the market needs, a lot of progress have been made and allow Sofradir to offer new product designs mainly dealing with the simplification of the detector use as well as reliability improvements. In addition to the conventional technologies used at mass production level, the Molecular Beam Epitaxy (MBE) approach has been under investigation for several years to prepare both the very large array fabrication and the new (3rd) generation developments. CEA-Leti, in cooperation with Sofradir, obtained very good results on 4-inches wafer size which confirms the mastering of this growth process. Very high qualities FPAs (1280×1024), with pitches as small as 15μm, were demonstrated as well as bicolor and dual band FPAs which use more complex multi hetero-junctions architectures. A very new development at CEA-Leti concerns avalanche photodiodes (APD) made with HgCdTe which presents a unique feature among all the over semiconductors: extremely high avalanche gains can be obtained on n on p photodiodes without absolutely any noise excess. These results open new interesting fields of investigation for low flux applications and fast detectors. The cooled IR detector field is progressing very rapidly and new developments will offer a lot of system simplification and enhancements.
Infrared Imagers/Systems and Their Application I
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Subpixel boundary backward substitution reconstruction algorithm for not uniform microscan to FPA and blind micromotion matching
For the subpixel micro-scanning imaging, we propose the reconstruction algorithm based on neither interpolation nor super-resolution idea but one of the block-by-block method recursive from the boundary to centre when additional narrowband boundary view-field diaphragm whose radiation is known a prior. The aim of the predicted boundary value is to add the conditions for solving the ununiqueness ill-problem to the inverse transition matrix from the destructed process. For the non-uniform scan factor, the improved algorithm associated with certain non-uniform motion variables is proposed. Additionally, attention is focused on the case of unknown subpixel motion, when the reconstructed images are blurred by motion parameter modulation and neighbouring point aliasing because the value of micro-motion is not the correct one. Unlike other methods that the image registration is accomplished before multi-frame restoration from undersampled sequences frame by frame, in this paper, 2-D motion vector is estimated in single frame just from the blur character of reconstructed grids. We demonstrate that once the estimated motion approaches to the real one, square summation of all pixels over the unmatched image approximately descends to the minimum. The matching track based on recursive Newton secant approaching is optimized for high matching speed and precision by different strategies, including matching region hunting, matching direction choosing and convergence prejudgement. All iterative step lengths with respect to motion parameters are substituted by the suitable values derived from the statistic process and one or multi-secant solution. The simulations demonstrate the feasibility of the matching algorithm and the obvious resolution enhancement compared to the direct oversampling image.
Analysis of selection of structural element in mathematical morphology with application to infrared point target detection
Jiefeng Guo, Guilin Chen
Low signal-to-noise ratio and complex background make the point target detection from infrared image a challenging and difficult problem. Combining the filtering characteristic of opening operation of mathematical morphology and the technique of background prediction, this paper presents a point target detection algorithm based on mathematical morphology, including analytic expressions for the detection algorithm. The selection of structural element is the key of mathematical morphology. The analyzing method of selection of structural element is presented. This paper mainly analyzes and compares the different performances produced by four kinds of structural elements having different size and shape, when these structural elements process the different components of complex background and point target. The analyzing and comparing methods focus on the curves generated by plotting the samples of image in row in which the point target exists. This analyzing method of selection of structural element is effective. The experiment results of detection algorithm using four kinds of structural elements to respectively process the infrared point target image are also presented and analyzed, including the probability of detection and the number of false targets.
Infrared dual spectral imaging system
Hai-tao Wang, An-bing Geng, Chang-cheng Yang, et al.
Based on the spectral characteristics of the target, dual spectral imaging system is conducted in target detection. The dual spectral system has simultaneously less false alarm probability and widened operating distance, There are many models of dual spectral system, such as ultraviolet and visible light, visible light and near infrared, mid-IR and long-IR system and etc. The principle of dual spectral system is described, and especially the paper studied deeply hybrid refractive-reflective dual-band system; refractive mid-IR and long-IR system. A designed sample of part-optics-light-path refractive detection system based on the application of re-imaging and 100% cold shield efficiency is given which is operating in the 3.7~4.8μm and 7.7~10.3μm wavelength bands and the rectification of the ray aberrations in both bands has been simultaneously accomplished. Because of the same aperture, field of view and focal length, the dual spectral optical images can be coupled and be simultaneously displayed in one picture.
MODIS-based analysis of snow distribution and change in Emin River basin, Xinjiang, China
Zhihui Liu, Jingxiang Gao, Huan Pei, et al.
Serious snowmelt flood happened in the north of Xinjiang in March each year and it brought serious effect to local people's life and national production. Researching on snow distribution and change can provide decision support for preventing flood and alleviating disaster, Meanwhile, accurate snow mapping on a drainage area and snow cover depletion curve can provide parameters for simulating snowmelt runoff. This paper introduced unmixed pixel method and extracting snow cover according to the elevation zone, analyzing snow change in each elevation zone from March 4th to 12th 2005 in Emin river basin, Xinjiang, China integrating MODIS data and GIS. In addition, this paper analyzed the reason of flood formation and making regression analysis of snow change with weather factor by stepwise regression. The result shows that the correlation between snow change and temperature, as well as precipitation is high in 400-900m elevation zone (r = 0.9).
Infrared Imagers/Systems and Their Application II
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General performance evaluation on thermal imaging systems with the square integral method based on MRTD channel width
Jihui Wang, Weiqi Jin, Xia Wang, et al.
The Square Integral (SQI) Method based on MRTD (Minimum Resolvable Temperature Difference) is introduced for the design and evaluation of thermal imaging systems. It is well known that there exists an optimal angle magnification which can make optoelectronic imaging systems and human eye matching optimally, and make optoelectronic imaging systems attaining the optimal performance. Based on MRTD and channel width, a new way called SQI method is presented for evaluating the universal performance on thermal imaging systems, and attaining the optimal angle magnification or optimal viewing distance. The method can give a rational description for the matching between thermal imaging systems and human eye. Results calculated with this method are in agreement with experiment measurements quite perfectly. From the coherence between measurement data and theoretical predictions with variable detector size, optics focus, luminance and human vision, it appears that the SQI method is an excellent synthesized measure for the optimal angle magnification and the performance of thermal imaging systems.
Study of dynamic infrared scene projection technology based on Digital Micro-mirror Device (DMD)
Yu Hu, JiaoBo Gao, Jun Wang, et al.
Digital Micro-mirror Device (DMD) is a kind of reflecting spatial light modulator which has most virtue such as operating on the whole wave bands, high resolution, high frame rates, wide dynamic range, complete digitalization, small cubage and wide thermal range. A dynamic infrared scene generating and emulation system can be constructed of it with producing high quality dynamic infrared image. This paper presents the operating principle of DMD and the basic principle of dynamic IR scene projection system based on DMD. The choice of illumination and optical path in the system is analyzed in details. A modified device with a infrared window is obtained, its transmissive band is 0.4~12μm and almost all pixel is intact. Several images generated by the system is shown and the characteristics of spectrum output is tested. Major technical parameters of the DMD dynamic infrared scene projection system is given in the last section.
Study on pulsed phase analysis of depth measurement for infrared thermal wave nondestructive evaluation
Yan-hong Li, Yue-jin Zhao, Li-chun Feng, et al.
Pulsed infrared thermal wave nondestructive evaluation has been widely used in various materials' R&D, quality supervise, detection and evaluation. Furthermore, based on pulse infrared thermal wave thermography experiment, a new signal analyze method called pulse phase thermography was introduced by changing the temporal signal to frequency field through Fourier transform. The pulse signal consists of various frequencies information and different thermal wave frequency reaches corresponding depth in the material. According to the relation of thermal wave's frequency to conduction depth, pulse phase thermography method can detect the depth of defects. The intuitionistic thermograph result is the phase information of each pixel in frequency field, through that the defect's size, location can be well distinguished. In order to solve the depth detection, two standard flat bottom holes samples made of aluminum and steel were studied. By analyzing the experimental results, it showed the theoretical depth value and actual depth relations, which can provide an assistant way for subsurface defects detection of material and structure. In that case, given a standard sample with artificial defects, the products made of the same material can be well detected and evaluated. At the same time, corresponding to the pulse infrared thermal wave thermography, phase thermographs with the phase information have higher sensitivity to the defects, and do not influence with the ununiformity of the light heating.
Infrared Imagers/Systems and Their Application III
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Ultrasonic infrared thermal wave nondestructive evaluation for crack detection of several aerospace materials
The applications of ultrasonic infrared thermal wave nondestructive evaluation for crack detection of several materials, which often used in aviation alloy. For instance, steel and carbon fiber. It is difficult to test cracks interfacial or vertical with structure's surface by the traditional nondestructive testing methods. Ultrasonic infrared thermal wave nondestructive testing technology uses high-power and low-frequency ultrasonic as heat source to excite the sample and an infrared video camera as a detector to detect the surface temperature. The ultrasonic emitter launch pulses of ultrasonic into the skin of the sample, which causes the crack interfaces to rub and dissipate energy as heat, and then caused local increase in temperature at one of the specimen surfaces. The infrared camera images the returning thermal wave reflections from subsurface cracks. A computer collects and processes the thermal images according to different properties of samples to get the satisfied effect. In this paper, a steel plate with fatigue crack we designed and a juncture of carbon fiber composite that has been used in a space probe were tested and get satisfying results. The ultrasonic infrared thermal wave nondestructive detection is fast, sensitive for cracks, especially cracks that vertical with structure's surface. It is significative for nondestructive testing in manufacture produce and application of aviation, cosmography and optoelectronics.
Optical path layout and moving mirrors of wavemeter based on Michelson interferometer
Liqiang Wang, Yuexiang Peng, Fengyou Gao, et al.
General wavemeters based on Michelson interferometer only have a moving arm, which cann't more multiply optical paths' differences, and is unable to avoid dispersion from a beamsplitter. Commonly, the moving mirror driven by a direct current motor and a ball screw have some disadvantage, such as heavy weight, unstable motion. In the paper, a better optical layout, and configuration and a driving method of moving mirrors are proposed. A newly optical paths layout of a wavemeter based on Michelson Interferometer is present, including two moving mirrors for forming optical paths' differences, a beamsplitter for splitting a light into a transmitted light and a reflected light, two reflectors, and a reference laser. It has two moving arms and can eliminate dispersion from the beamsplitter. According to Doppler effect, how to form the interference fringes in the photodiodes is analyzed and formulated. The Doppler effect appears with motion of the moving mirrors. Consequently, alternately dark and bright interference fringes are generated, then received and converted into the electronic signals by the photodiodes. It is concluded that the electronic signals involves the wavelength of a light and the velocity of the moving mirror by investigating the Doppler effect. The structure of the moving mirrors is clarified. The moving mirrors are made of the two pyramid prisms which are placed symmetrically on the driving motor. A controlling system for keeping the moving mirrors in constant velocity is designed. In order to make frequencies of electronic signals from interference fringes stable, the moving mirrors must move in a uniform speed. The voice coil motor (VCM) drags the moving mirror to and fro. VCM in uniform motion is realized by an optical-mechanical-electrical closed-loop feedback system. The Doppler frequency difference of the reference laser is the standard of the system. The PID controller comprising parallel proportional-integral-differential operational circuit regulates the velocity of VCM.
MTF testing algorithms for sampled thermal imaging systems
Stephen D. Fantone, David A. Imrie, Daniel Orband, et al.
The introduction of third generation thermal imagers brings a new challenge to the laboratory evaluation of the thermal imager resolution performance. Traditionally, the Modulation Transfer Function (MTF) is used to characterize the resolution performance of the thermal imager. These new third generation of thermal imagers can be categorized as sampled imaging system due to the finite pixel size of the elements comprising the focal plane array. As such, they violate the requirement of shift invariance required in most linear systems analyses. We present a number of approaches to measuring the resolution performance of these systems and conclude that source scanning at the object plane is essential for proper MTF testing of these sampled thermal-imaging systems. Source scanning serves dual purposes. It over-samples the intensity distribution to form an appropriate LSF and also generates the necessary phases between the thermal target image and the corresponding sensor pixels for accurate MTF calculation. We developed five MTF measurement algorithms to test both analog and digital video outputs of sampled imaging systems. The five algorithms are the Min/Max, Full Scan, Point Scan, Combo Scan, and Sloping Slit methods and they have all been implemented in a commercially available product.
Infrared Imagers/Systems and Their Application IV
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Quantitative analysis of peanut oil content in ternary blended edible oil using near infrared spectroscopy
Huacai Chen, Fuli Liu, Zhilan Wang, et al.
Calibration models of quantitative analysis of peanut oil content in ternary blended edible oil by near infrared spectroscopy were built using partial least square (PLS) regression. A total of 92 samples blended with three kinds of pure oil in different proportion (V/V) were prepared. Near infrared diffuse reflectance spectra of the samples were collected over 4 000 cm-1-10 000 cm-1 spectral region with a FT-NIR spectrometer. A calibration model of prediction to the peanut oil content was established with PLS using the original spectra and validated with leave-one-out cross validation method. The correlation coefficient and the RMSEC of the model were 0.9926 and 2.91%, respectively. The result showed that near infrared spectroscopy could be an ideal tool for fast determination to the peanut oil content in blended edible oil.
Calibration research of laser speedometer
Yan-mei Cui, Tao Li, Jie Leng, et al.
Existing calibration methods of laser speedometer are summed up and one new calibration method and instrument with simulated target is put forward in this paper. Comparison and experiments show that the calibration instrument can meet the need of laser speedometer calibration because of its wide calibration range, high repeatability and universal performance.
Infrared and visible image fusion algorithm based on Contourlet transform and PCNN
Yuchi Lin, Le Song, Xin Zhou, et al.
A new image fusion method based on Contourlet transform and an improved pulse coupled neural network (PCNN) is introduced in this paper. The input infrared and visible images are processed with Contourlet decomposition which has multi-scale and multi-directional characteristics. The PCNN algorithm deriving from the neurophysiology is optimized in order to be compatible with the image fusion strategy. Owning to the global coupling and pulse synchronization characteristic of PCNN, this new fusion strategy utilizes the global features of source images and has several advantages in comparison with the traditional methods based on the single pixel or regional features. Multiple criteria and statistical indicators regarding different aspects of image quality are presented for objective and quantitative evaluation of the fused images to understand the performance of image fusion algorithms. Experimental result shows that the new method can improve the quality of image fusion and can achieve an ideal fusing effect. The method would find its application in the aspects of optical imaging, target detection and safety monitoring, etc.
Technology for low-cost PIR security sensors
Current passive infrared (PIR) security sensors employing pyroelectric detectors are simple, cheap and reliable, but have several deficiencies. These sensors, developed two decades ago, are essentially short-range moving-target hotspot detectors. They cannot detect slow temperature changes, and thus are unable to respond to radiation stimuli indicating potential danger such as overheating electrical appliances and developing fires. They have a poor optical resolution and limited ability to recognize detected targets. Modern uncooled thermal infrared technology has vastly superior performance but as yet is too costly to challenge the PIR security sensor market. In this paper microbolometer technology will be discussed which can provide enhanced performance at acceptable cost. In addition to security sensing the technology has numerous applications in the military, industrial and domestic markets where target range is short and low cost is paramount.
Poster Session
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High uniformity InGaAs linear mesa-type SWIR focal plane arrays
In this paper, 256 elements front-illuminated InGaAs mesa detector arrays were fabricated based on doped-InGaAs absorbing layer in MOCVD-grown p-InP/n-InGaAs/n-InP double-heterostructure epitaxial materials. The processing includes mesa-making, SiNx passivation, growth of electrodes and so on. The current-voltage, capacitance-voltage characteristics and response spectrum of the detector were measured. The results indicate that the InGaAs detector has typical dark current about 0.9 nA at 0.5 V reverse-bias voltage, a capacitance as low as 49 pF at 1 reverse-bias voltage, and the peak wavelength and cutoff wavelength at 1.57μm and 1.68μm respectively. The InGaAs detector arrays were connected with two CTIA-structured L128 read-out integrated circuits, and the response signal and noise were obtained. At room temperature, the mean peak detectivity of the InGaAs focal plane arrays (FPAs) is 1.9×1012 cmHz1/2W-1, and the non-uniformity of response is superior to 6%. The laser beam induced current (LBIC) technique was used to investigate the crosstalk and photoactive area of the InGaAs detectors. Its results indicate that there is little crosstalk between two neighbor InGaAs detectors, about 7%. The photoactive area of InGaAs detector extends about 4.5 μm, and the reason is analyed in the paper.
Iterative infrared image restoration
Iterative infrared image restoration is concerned with the improvement of infrared imagery acquired in the presence of varying degradations. The degradations can arise from a variety of factors: common examples include undersampling of the infrared image data, uncontrolled platform or scene motion, system aberrations and instabilities, noise characteristic of the infrared detector. In this paper, the mathematic models of infrared image blur and sampling and noise models are discussed. The iterative infrared image restoration problem is discussed, too. We show the origin and restoration infrared images which are used in the application of iterative infrared image restoration. By assessing subjectively and objectively to restoration infrared images, we have verified this kind of model and the feasibility of the iterative infrared image restoration.
A kind of real-time infrared image enhancement algorithm
A new algorithm which is suitable for FPGA to the real-time infrared image enhancement is proposed in this paper. In order to reduce Infrared image noise, we use the accumulation of the combining sequential neighbor frames, and use the nonlinear expanding of gray histogram to enhance contrast ratio. This kind of algorithm has considered infrared image characteristic and vision characteristic of the human eye synthetically, and guarantee real-time character of image process, at the same time, also give consideration to the advantage of the FPGA design. This method can be realized easily on hardware without damaged enhancement result. Finally, quality of enhanced image is evaluated through a model. It has verified the enhancement result of this kind of algorithm, and offered reliable assurance for further treatment of the infrared image. Use in the image system of the infrared video, the effect of image Enhancement is obvious.
Growth and characterization of <110> oriented ZnTe single crystal
Reng Wang, Weizheng Fang, Pei Zhao, et al.
ZnTe crystal has been grown at a temperature as low as 1060°C using Te solvent method. X-ray diffraction showed that the ZnTe crystals were grown from <110> oriented. The transmission was over 60% from 2 μm to 22 μm by using Fourier Transform Infrared Spectrometer. The etch pit density in the sliced wafer was about 2×104 cm-2 detected by Scan Electronic Microscopic. The transmission spectrums were measured from 0.2 to 3 THz by using Terahertz Time Domain Spectroscopy. And the refractive index and extinction coefficient were obtained through analysis of the time domain waveform.
Application of contourlet transform in infrared image denoising
Yuchi Lin, Xin Zhou, Le Song, et al.
Wavelet threshold denoising is widely used in the denoising of the infrared image for its simplicity and effectiveness in application. However, there has been a growing awareness to the observation that wavelets may not be the best choice for describing infrared images. This observation is due to the fact that wavelets are blind to the smoothness along the edges commonly found in images. A denoising method of infrared image based on Contourlet transform is presented in this paper. In selecting the hard threshold function to process the coefficients in the Contourlet domain, we could thereby obtain the denoised infrared image of superior quality via inverse transforming. The result of the experiment indicates that compared with the traditional algorithms of the wavelet, this method can preserve the detail and the texture of the infrared image more effectively, and has better image effect and the SNR value.
Study on the thermal field change and affecting factors in urban areas of Hangzhou Tourism city
The thermal field of urban and suburban areas of Hangzhou tourism city was derived from TM ETM thermal infrared data and the spatial characteristics and changes were qualitatively analyzed. Water bodies have stable and uniform thermal field. The land surface temperature (LST), normalized difference vegetation index (NDVI), buildings distribution information and water body distribution information of two times TM Image in 1993 and 2003 were extracted and the influence factors of thermal field time-space characteristics were analyzed. The two times field of 1993 and 2003 become comparable with each other in thermal value. With the other bands of the same data set, the basic factors affecting the thermal field, namely buildings, greenbelts and water bodies, were identifled by visional interpretation or image processing. The LST, NDVI, buildings and water body distribution information were calculated for qualitative analysis of the basic affecting factors. The results show that the effects upon the thermal field gradually decrease in order of buildings, greenbelts and water bodies. So, in Hangzhou tourism city, many existing greenbelt and water bodies should be strictly protected and constructed.
Retrieval of atmospheric water content and transmittance computation of thermal bands based on MODTRAN
As an EOS instrument with 36 bands, MODIS is very useful because of its global coverage, radiometric resolution and dynamic ranges as well as accurate calibration in multiple thermal infrared bands designed for retrievals of sea surface temperature (SST), land surface temperature (LST) and atmospheric properties. The paper discusses the influence of main parameters such as water content density on atmospheric transmittance and radiance. The relationships between the atmospheric transmittance and different atmospheric height, and different atmospheric water content were analyzed. This paper introduces and derives the algorithm about retrieving water content of atmosphere from MODIS data. The retrieving result was analyzed and then MODTRAN was employed to simulate the relationship between the water content of atmosphere and the transmittance of MODIS bands 31 and 32. The technique has great value to get some parameters timely with accuracy to every pixel and to monitor the global change.
Fast curvelet transform based non-uniformity correction for IRFPA
The Curvelet transform was developed from the wavelet transform. The applications of Curvelet transform reveal its great potential in image processing due to its unique characteristics. In this paper, the theory and implementation of Curvelet transform is summarized. The traditional Curvelet transform involves a complicated index structure which makes the mathematics and quantitative analysis especially delicate, and it uses overlapping windows increasing the redundancy. The Fast Curvelet Transform was discussed in this paper, which has the optimal sparse representation. By utilizing Curvelet wrapping algorithm based on translation invariance to the nonuniformity correction of the IRFPA, better MSE compared with traditional methods can be obtained. Great compute and analysis have been realized by using the discussed algorithm to the simulated data and real infrared scene data respectively. The experimental results demonstrate, the corrected image by this fast Curvelet transform algorithm not only yields highest Peak Signal-to-Noise Ratio values (PSNR = 33.803), but also achieves best visual quality.
The distribution of grating-coupled field of quantum well infrared photodetector using FDTD method
Hongbo Chen, Xiaoshuang Chen, Yong Zeng, et al.
For most commonly used GaAs/AlGaAs n-type quantum well infrared photodetectors (QWIPs), the normal incident absorption is not possible because of the transition rule. The optical grating is required to achieve high absorption quantum efficiencies. When some gratings are patterned on the metal plate, the polarization direction can be changed greatly because of the diffraction effect. Finite difference time domain (FDTD) method has been used to investigate the effect of a reflection metal grating on the couple efficiency previously. However, the authors only take one metal grating and apply periodic boundary condition along the grating direction due to the computation limit. For a real QWIP system, such simulation is crude. In this work we consider a real GaAs/AlGaAs QWIP with a wavelength response around 15um and use FDTD method to investigate the effect of a reflection metal grating on the electric field pattern and the couple efficiency. The simulating results show that the electric field pattern is not periodic for every metal grating in a real QWIP system. We have also studied the influence of the substrate thickness and the grating period on the electric field pattern and the couple efficiency. These results offer a guideline for the design of QWIP.
An optical model of wide field of view superspectral imager
Zhiping He, Weiming Xu, Jianjun Jia, et al.
This paper introduces a skill but practical optical model of developing wide field of view push-broom hyperspectral imager. Usually, the field of view of a push-broom hyperspectral imaging sensor is less than 30 degrees, and it can not meet the requirement for typical earth observation mission. This paper addresses the difficulty of developing wide field of view imaging sensor and presents an optical model of wide field of view hyperspectal imager. The optical model of hyperspectral imager is composed of a large field of view lens, a long entrance slit, two spectrometers and two area detector arrays and has a cross-track field of view of 60 degrees. The lens images a ground belt onto the long entrance slit, the slit acts as a field stop and allow only light from a linear belt in the scene to enter the imager. The light passing through the long slit is divided two equal parts using a special skill and it is separated and imaged on the area detector arrays by the two spectrometer. The analysis shows that the wide field of view hyperspectral imager doesn't drop down the spatial resolution.
The research for a system of binocular stereo vision based on the near-infrared imaging characteristics of black-and-white CCD
Pengwei Zhang, Zhiquan Zhang, Yifei Zhang
A system of binocular stereo vision based on the near-infrared imaging characteristics of ordinary black-and-white CCD (B/W CCD) camera is proposed to measure the three-dimensional profile of reverse engineering. In this system the infrared LED is used as the marker for the active probe tool, and the near-infrared filter is fixed on the black and white camera to simplify the background and enhance the signal-to-noise ratio of image, the compution of segmentation for the follow-up goal can be greatly reduced. The Paper details the principle and hardware components of the binocular vision system, then analyses and discusses the critical technologies of 3-D profile measurement such as camera calibration, feature extraction and three-dimensional calculation. The experimental results show that the method has many advantages, such as the great contrast images consisted of the markers and background , processing image easily, adapting the change of illumination and better precision positioning.
Study on the predicted model of crop leaf water status by the NIR band of ground reflectance and spaceborne hyperspectral images
Quanjun Jiao, Xue Liu, Bo Liu, et al.
Crop leaf water content can be a valuable biochemical parameter to diagnose crop water stress. The leaf water content characterizes some spectral absorption features in NIR band. Some researchers have proved that it was feasible to retrieve leaf water content utilizing those spectral absorption features. Measured leaf water content data of several sorts of winter wheat and the corresponding reflectance, CHRIS images were collected. Even 974 nm, 1160 nm and 1440 nm were absorption feature bands of foliar water, the predicted accuracies of leaf water content only using these bands were not satisfying. Four popular indices of vegetation water content including NDWI, SR, WI and REP were used to build the predict model and evaluated though relativity analysis. SR and REP opposed the stronger predicted accuracy of leaf water content than other spectral indices. Limited to the band position setting and band spectral function of CHRIS, SR and REP were modified fit to the band setting of CHRIS. The predicted model based on ground reflectance were made to adaptable to the band spectral function of CHRIS sensors, and the results showed that wide band spectral function indeed caused a lower accuracy of crop water content than narrow band spectral function.
IMMPDA algorithm for infrared target tracking based on multifeature fusion
Jin Zhang, Jianxun Song, Qinzhang Wu
The interacting multiple model probability data association (IMMPDA) algorithm is widely used to target tracking in clutter. However, it is difficult for IMMPDA to get high precision track when measurements of kinematics state is inaccurate, because it only considers kinematics feature of targets. To overcome the disadvantage, this paper presents an IMMPDA algorithm based on multi-feature fusion that utilizes multiple features of infrared targets such as kinematics state, size and gray. Association probabilities for targets position are calculated based on IMMPDA algorithm in the polar coordinates. Then the statistic distances of the size and gray are calculated according to state predictions and measurements. After that, statistic distances are further used to compute related association probabilities of targets that are in the validation region. The decision of synthetic data association of all targets in the validation region is made based on the information fusion, which uses fuzzy logic to get different weights of each feature. Experiments indicate that the proposed algorithm has high quality tracking performance. Compared with conventional IMMPDA algorithm, the new algorithm cannot only get higher accurate target association but also improve the stability of the infrared target tracking system.
New technology of photoelectric reconnaissance based on exploitation of quantum effects
A new high spectrum difference technique was discussed in this paper, which use exploitation of quantum effects to detect and warn low observable objects (include missile, stealth etc.). It is a new technique in photoelectric reconnaissance area, and has many advantages such as wide radiation regions and greatly strengthens signal intensity. In this paper radiation spectrum intensity, atmosphere attenuation and effect distance are studied. We found that high intensity of stimulated emission spectrum can be obtained in atmosphere transmit window. So the sensitiveness and distance of detect can be enormously improved.
Automatic target detection in dual band infrared imagery
Jiancheng Yu, Shengli Sun, Guilin Chen
Automatic target detection (ATD) in infrared imagery is challenging problem to Surveillance and Reconnaissance application. Though the recent of advances of remote sensing instrument which significantly improve system's spatial resolution and sensitivity, the size of many infrared targets is equivalent to or even smaller than pixel resolution. Therefore target recognition must be carried out within one pixel. Under such circumstance, traditional image processing techniques generally can not perform well in applications. The paper presented here investigates the issue and presents a novel algorithm for automatic target recognition in dual band infrared imagery with no priori knowledge. It consists of two stage processes, clutter rejection in infrared imagery of each band and followed by target detection with the fusion of the two bands of infrared images. Morphologic method instead of spatial-based processing techniques is applied in clutter rejection. An alternative way is Top-hat which gains a good performance in images with small targets. An in fusion center, dual-band infrared images are fused according to the AND rule whereas the decision rules are obtained from Neyman-Pearson (NP) criterion. A simple method of gaining each sensor's threshold with optimization has been developed. Relative simulations, assuming noise in infrared system is subjected to Gaussian distribution, shows the fusion result with a greater performance than either one even one's performance has been greatly degraded. Experimental results are presented using dual bands of registered infrared imagery to evaluate the performance of the new algorithm. It is suggested that the method presented above is robust, feasible and effective in this application.
The side-passivation research on LWIR HgCdTe detector
In order to prevent Hg running over from the exposing side of HgCdTe LWIR detector with little photosensitive region, side-passivation detectors are fabricated. Then several experiments are done to characterize the side-passivation effect. Firstly, a SEM micrograph is shown, and it makes clear that wet etching and side-passivation can remove part of defect induced by IBE. Secondly, the performance measurement indicates that the performance of side-passivation detector is superior to the general one, especially for detectors with little photosensitive region. Thirdly, hot dipping is done to say that the thermal stability of side-passivation detectors is superior to general ones. And with the exception of this, the less the photosensitive region width is, the stronger the ability of protection is. Last but not the least, the detectivity of not only general detectors but also side-passivation ones increases obviously. As a whole, the performance of side-passivation detectors increases more largely than general ones. Above all, side-wall passivating film can passivate the sensitivity of detector's surface and block Hg out of the surface effectively. The results can provide experimental reference for IR semiconductor detector.
Pseudo-color coding method of infrared images based on human vision system
Xiao Zhang, Tingzhu Bai, Hailan Li
Infrared images often display in gray scale. The low contrast and the unclear visual effect are the most notable characters of infrared images that make difficult to observe. It is a fact that gray scale is not sensitive to human eyes, and it has only 60 to 90 just noticeable differences (JNDs). In comparison with gray scale, color scale might give up to 500 JNDs. Usually people can distinguish many kinds of colors much more than grays. And in gray images, human don't have the ability to tell apart the nuances about detail. Pseudo-color coding enhancement is the task of applying certain alterations to an input gray-image such as to obtain color-image that is a more visually pleasing. In this paper, we introduced a pseudo-color coding method based on human vision system for infrared images display. The HSI space is especially fit for human vision system and is viewed as an approximation of perceptual color space. So the pseudo-color coding method introduced is based on HSI space. In the first place, the individual functional relationship of Hue, Intensity, and Saturation with gray scale level is established. In the second place, the corresponding RGB values are obtained through transformation from the HSI color space to the RGB space. Lastly, the effect of Infrared images enhancement based on the pseudo-color coding method is displayed. Results indicate that this method is superior to other methods through the comparison.
Research of sub-pixel location algorithm based on image correlation
Fuwen Li, Chao Xu, Weiqi Jin, et al.
Digital image correlation as a tool for surface deformation measurement has been widely used in the field of experimental mechanics. The method is known to resolve deformation gradient fields with sub-pixel accuracy. In this paper, we address the application of digital image correlation to the image location with sub-pixel accuracy to estimate displacement of multiple frames of video sequences. The estimation effect depends on various factors such as image noise and the correlation algorithm chosen. Algorithms of the sub-pixel location on image are analyzed: Gray-value Interpolation based Image Correlation and Correlation Coefficient Distribution based Fitting. However, Gray-value Interpolation needs a large amount of computational consumption although has high accuracy and it is apt to be influenced by noisy. Correlation Coefficient Distribution has low accuracy but high effective performance. According to the characteristics of these algorithms, a mix algorithm is introduced to improve both accuracy and computational consumption. The imaging process and algorithm execution are simulated using MATLAB. Further more, we could evaluate the displacements of moving objects between two frames of real video sequences and obtain the reconstructed images through displacement data. The validity of the mixed image location algorithm is obviously verified by comparison between original frames and reconstructed image.
A novel infrared image fusion algorithm based on contourlet transform
Yajun Song, Kun Gao, Guoqiang Ni
For processing multi-band infrared images detected by Multi-color IR Focal Plane Arrays (IRFPA), an image fusion algorithm is proposed based on contourlet transform (CT). Source images are firstly decomposed to the domain of the contourlet transform, the image fusion is then implemented in sub-bands with different scales and directions combining with special image fusion rules. By employing the parameters of Regional Energy (RE) and Local Relative Pixel Intensity (LRPI), which are calculated with the values of CT coefficients and the corresponding neighbor region, the algorithm integrates the approximation coefficients and the detail coefficients according to the parameters. Evaluations of the experiment results according to both the subjective and objective criteria, including average, mean square error, entropy and combined entropy, demonstrate that the algorithm based on CT with the proposed fusion rules is more effective than the ones based on CT with RE fusion rules and traditional method.
Infrared dim small target track predicting using least squares support vector machine
Guangping Wang, Kun Gao, Guoqiang Ni
Compared with Support Vector Machine (SVM), Least Squares Support Vector Machine (LS-SVM) has overcome the shortcoming of higher computational burden by solving linear equations, and has been widely used in classification and nonlinear function estimation. For dim small targets track predicting in the IR image sequences, a new method based on LS-SVM is proposed. LS-SVM has prominent advantages in model selecting, over-fitting overcoming and local minimum overcoming. In this paper, the RBF kernel function is used in LS-SVM, so there are two parameters in LS-SVM: the regularization parameter γ and the kernel width parameter σ2. Since the optimization parameters (γ, σ2) determine the performance of LS-SVM, so their influence on the performance of LS-SVM is analyzed in this paper. Finally, compared with the Least Square (LS) estimation, the experiments show that LS-SVM can track targets more precisely and more robustly than LS. Experiments show that the track predicting method based on LS-SVM possesses the strong learning capability through a small quantity of samples, the good characteristic of generalization and rejection to random noise. It is a potential track predicting method.
A preliminary study on laser-induced damage in InGaAs material and detectors
Hongyang Liu, Hengjing Tang, Haimei Gong
We have investigated the laser-induced damage morphology using femtosecond laser pulse at 0.8 μm on InGaAs surface. Damage morphology has been analyzed by a scanning electron microscope (SEM). The diameter of the damage spot increased, on increasing the laser fluence. The damage morphology at the central portion differs from the one at the periphery of the spot. The roughness and the step height of the damage spot were measured through XP Stylus Profiler which is a computerized, high-sensitivity surface profiler. The depth morphology of the damage spot shows the ablation of material. After the laser-induced damage studies of material, laser-induced damage in 256 elements front-illuminated InGaAs detectors arrays are reported. Prior to irradiation, the dark current is dominated by the diffusion current indicating that the junctions are of good quality. The dark current-voltage curves before laser irradiation are compared with the ones irradiated at different laser power density and we find that the laser irradiation may produce an increase in the dark current. The spectral response was also measured to evaluate the laser-induced effects on the detectors.
Characterization of multilayered HgCdTe for MW/LW two-color application
Qingzhu Wei, Wenhong Zhou, Weiqiang Wang, et al.
Dual color detection is a major concept of the third generation infrared focal plane arrays sensors (FPAs) for increasing the demand of target identification. The performance of these detectors are largely relied on the growth capability of HgCdTe multilayered structure. This paper presents our preliminary results on growth of MW/LW two-color structure by using molecular beam epitaxy. The detector had NPpn architecture, with indium doped n-type bottom (window) layer and Hg-vacancy doped MW and LW p-type layers. The top n-type layer was ion implanted by using B+. The compositions (mole fraction x) of each layers and its gradient at the interfaces were measured by infrared transmission, SIMS and SEM. The In doping layer was analyzed by SIMS. The electrical properties of In doping layer were measured by Hall effects measurements. It was found that the structure obtained agreed well with the growth design. MW/LW two color detectors of a 64×64 format were fabricated by mesa delineation, and the optimum structure was also discussed.
Surface defects induced by impurities in MBE-grown HgCdTe
Xiangliang Fu, Weiqiang Wang, Qingzhu Wei, et al.
Surface defects of molecular beam epitaxially grown HgCdTe are the major concern in developing large format infrared focal plane arrays. Voids were usually observed on the HgCdTe surfaces as previously reported, they were originated either from the improper substrates preparation or from the growth condition. However, the defects formation with impurities has not been addressed. This paper presents our recent observation on defects induced by the impurities involved in the mercury beam fluxes. These defects can be craters or bumps, having a spatially clustering feature. To identify the origin of these kinds of defects, experiments were performed on HgCdTe as well as CdTe with mercury flux, and the defects were observed and analyzed by using SEM and EDAX. The result, for the first time, confirmed that impurities in the mercury beam were responsible to the formation of surface defects.
The research of range-gated laser night vision system on cars
Zhouyan Zeng, Hualin Fan, Songtao Hejun
The characteristic of several night imaging and display technologies on cars are introduced. Compared with the current night vision technologies on cars, Range-gated technology can eliminate backscattered light and increase the SNR of system. The theory of range-gated image technology is described. The plan of range-gated system on cars is designed; the divergence angle of laser can be designed to change automatically, this allows overfilling of the camera field of view to effectively attenuate the laser when necessary. Safety range of the driver is calculated according to the theory analysis. Observation distance of the designed system is about 500m which is satisfied with the need of safety driver range.
Infrared target tracking using multisensor data fusion
Jin Zhang, Yu Lu, Hao Zhu, et al.
The infrared (IR) sensor provides the azimuth and elevation angle measurements of the target. For 3-D tracking, at least two IR sensors are needed. The conventional method puts two sensors in good observation position to gain high precision target track. However, the performance of the method is limited because of instability and observable limit of IR sensors. Therefore, more IR sensors are required to improve efficiency of the tracking system. Multisensor data fusion algorithm proposed in this paper is a novel approach to handle measurements from multiple IR sensors. Measurements extracted from every IR sensor by image processing are put into the extended Kalman filter. Then intersection results of measurements from two sensors in acceptable geometrical position are computed. Every intersection result is assigned a weight factor that represents the performance of intersection using fuzzy logic techniques. The fused estimate of the target is obtained by using a weighted average method to all the intersection results. The simulations with Monte Carlo methods show that the proposed algorithm can fuse the target tracks effectively and accurately. Compared with conventional algorithm, the new algorithm can provide higher precision and more robust estimate of the target.
Analysis of thermal stress damage in single-crystal silicon induced by 1064-nm long-pulse laser
Yanbei Chen, Jian Lu, Xiaowu Ni
Single-crystal silicon is an excellent infrared window material and is often used as light filter, infrared window and substrate material in an optical system. At the same time single-crystal silicon is typical brittle material. Therefore thermal stress damage has possibly occurred before melting when it is irradiated by laser. In order to investigate on the laser-induced thermal stress damage problem in single-crystal silicon, a spatial axisymmetric finite element model is established to solve the thermal stress problem which a single-crystal silicon substrate is heated by a Nd:YAG laser beam with wavelength of 1064nm and pulse width of the millisecond order. After the temperature and stress fields are obtained, the relevant analysis is carried out. The calculational results are in reasonable agreement with the reported experiment results. It found that the stress value in the central zone of the laser spot exceeds the fracture strength of single-crystal silicon, which can explain the damage of cleavage fracture of the material.
A robust sub-pixel edge detection method of infrared image based on tremor-based retinal receptive field model
Kun Gao, Hu Yang, Xiaomei Chen, et al.
Because of complex thermal objects in an infrared image, the prevalent image edge detection operators are often suitable for a certain scene and extract too wide edges sometimes. From a biological point of view, the image edge detection operators work reliably when assuming a convolution-based receptive field architecture. A DoG (Difference-of- Gaussians) model filter based on ON-center retinal ganglion cell receptive field architecture with artificial eye tremors introduced is proposed for the image contour detection. Aiming at the blurred edges of an infrared image, the subsequent orthogonal polynomial interpolation and sub-pixel level edge detection in rough edge pixel neighborhood is adopted to locate the foregoing rough edges in sub-pixel level. Numerical simulations show that this method can locate the target edge accurately and robustly.
Fast response pyroelectric detector-preamplifier assembled device
PiJi Bai, Yunjian Tai, Huiping Liu
The pyroelectric detector is wide used for its simple structure and high performance to price ratio. It has been used in thermal detecting, infrared spectrum and laser testing. When the pyroelectric detector was applied in practice, fast reponse speed is need. For improving the response speed of the pyroelectric detector some specific technology has been used in the preamplifier schematic. High sense and fast response character of the pyroelectric detector-preamplifier assembled device had been achieved. When the device is applied in acute concussion condition, it must survive from the acute concussion condition testing. For it reliability some specific technology was used in the device fabricating procedure. At last the performance parameter testing result and simulation application condition result given in this paper show the performance of the pyroelectric detector-preamplifier assembled device had achieved the advance goal.
Study of uncooled thermal imaging system with multiple working temperatures
Reasons that thermal imaging systems consume power have been analyzed, and a low-power design scheme of thermal imaging systems has been presented with multiple working temperature points. Transient response performance of α-si microbolometer detectors is simulated firstly when the working temperature varies in the range from -40°C to +60°C. Simulating results show that α-si microbolometer detectors have coherent response performance in a large range of working temperature, which lay basis for designing uncooled thermal imaging system with multiple working temperatures. Different from traditional thermal imaging systems, this thermal imaging system has three working temperature with an accuracy range of less than ±0.01°C. When working, the temperature control circuit will switch between the working temperatures according to the variety of the environmental temperature. To evaluate this thermal imaging system, we measure its power consumption and NETD in the environmental temperature range from -40°C to +60°C. The measurement results are that the total power is less than 2500mW and the NETD is less than 120mk. This indicates that the thermal imaging system has nearly the same imaging quality and obviously lower power, compared with traditional thermal imaging systems.
Research on 10.6 μm laser beam monitoring in CO2 laser processing system
Yali Shi, Yunguo Gao, Weijie Deng, et al.
It is a key point of CO2 laser beam monitoring in the CO2 laser processing system to achieve alignment between CO2 laser and PL (pointing and launching) system. By monitoring the angle offset of CO2 laser beam, the compensation can be gotten witch is given to fast-steering mirror to rectify the direction of laser beam. But the normal photoelectric detector can not get the laser signal because of CO2 laser's high energy and long wavelength. Its wavelength is 10.6μm and its power can reach kW level. Consequently, it is difficult to detect the high-energy 10.6μm laser beam directly. So, we monitored the output mirror of laser resonator superseded the laser beam, indirectly. The laser beam monitoring system could be designed based on CCD laser auto-collimation angular measurement principle and image processing method. In this paper, application of CCD laser auto-collimation angular measurement principle and image processing method for CO2 laser beam monitoring system is introduced particularly, After design, fabrication and alignment, the monitoring system can be used for experimental study that including angular measurement accuracy and angle offset measurement of CO2 laser beam. Angle offset range and angle variation rule of CO2 laser beam is also can be acquired for further research.
Based on Householder transform of the Zernike polynomial wavefront fitting method to solve active optics correction force
Fu-guo Wang, Fei Yang, Xiao-xia Wu, et al.
Corrective force solving is a critical technology of the active optics. A method to solve active optics corrective force is introduced, which is based on Householder transform of Zernike polynomial wave front fitting, this method is different from the traditional least square method and Gram-Schmid orthogonal method, because it does not bring ill-conditioned polynomial without constructing normal equation, so it can avoid calculation error, wave front fitting is precision. Based on the coefficient of the Zernike polynomial and the response function of the each actuator, the stiffness matrix of the primary mirror is built, and then adopting the damp least square method to calculate corrective force. Based on this method, φ400m test mirror is simulated many times, the calculation result approve: if the Householder transform is adopted, wave front fitting is precision, the result is stabilization and corrective effectiveness is better.
Design of a recursive filter for infrared image real-time processing
Bing Zhou, Zhongliang Zhou, Yongqiang He
A real-time recursive filtering processor using the core of digital commix chip HSP48212 was presented and designed assisted by FIFO memorizer and CPLD logic parse circuit, which realized real-time recursive filtering of 12bit infrared image. It has much notable virtue such as simple structure, strong real-time capability, controllable logic during operation process, and synchronal clock. It used in infrared fish-eye staring reconnaissance system for image real-time reduce noise and obtain perfect effect.
Application of improved BP neural network in infrared spectroscopy
Ming-zheng Gao, Huo-ming Zhang, Shang-zhong Jin
Artificial neural network(ANN), as a computing model possessing high-nonlinear mapping ability, has a wide application future in engineering. In this paper, combined with some practical problems in infrared spectroscopy, the method of quantitative analysis of the infrared spectrum using the improved BP-NN is discussed. The non-linear relationships between the component concentrations and the peak strengths are obtained. The method was tested and the resulted showed that the system performance was better than with several other commonly used conventional methods. Finally the problems which should be paid attention to are indicated and some helpful advice is given.
A novel real-time system for driving an infrared focal plan array based on FPGA
Ehsan Koohestani, Ali Homaei
A conceptual real-time structure for driving and image enhancement of a Cooled Infrared Focal Plan Array with 320×240 detectors will be discussed. It is the case that a mechanism for Non-Uniformity Correction between the sensitive elements needs a structure for compensation of gradual drift in the detectors' output by update the correction factors in a regular way. A feasible method, Least-Mean-Square, under a compact hardware is introduced. Inherently, the intended detector has not a suitable timing for sending out for standard display equipments, so it is essential to have hardware for frame-to-frame processing. Applying a capability of the sophisticated FPGAs, the contrast enhancement based on Bi-Histogram Equalization which preserves the brightness of infrared image effectively is described.