Proceedings Volume 10155

Optical Measurement Technology and Instrumentation

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Proceedings Volume 10155

Optical Measurement Technology and Instrumentation

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Volume Details

Date Published: 8 December 2016
Contents: 2 Sessions, 143 Papers, 0 Presentations
Conference: International Symposium on Optoelectronic Technology and Application 2016 2016
Volume Number: 10155

Table of Contents

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Table of Contents

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  • Optical Measurement Technology and Instrumentation
  • Front Matter: Volume 10155
Optical Measurement Technology and Instrumentation
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Recent progress of photodetectors based on MX2/graphene van der Waals heterostructures
Hang Yang, Shiqiao Qin, Jinyue Fang, et al.
Recently, heterostructures, combining the unique advantages of both graphene and transition metal dichalcogenides (TMDs, also known as MX2), have exhibited extraordinary photo-electrical properties, thus attracted tremendous interests worldwide. In this paper, we overviewed recent progress of MX2/Graphene van der Waals heterostructures, including the preparation methods, relevant parameters in opto-electronic measurements, physical mechanisms, existing experimental results and encountered problems. Here, we focus to cover the development of entire field, and provide a comprehensive and accurate understanding concerning this field, which may be helpful for interested researchers in this area.
A design of an optoelectronic isolation device to protect the measurement system of the underwater discharge acoustic source
Hui Yang, Yibo Wang, Wen Zhang
In this paper, an optoelectronic isolation device is designed to protect the measurement system of underwater discharge acoustic source (UDAS), from the harmful HV-GND drift. In this device, one linear optocoupler HCNR200 and four high speed operation amplifiers are used to perform a symmetric ‘electronic-optic-electronic’ conversion, and a method of setting a biased voltage is used to avoid the problem caused by the ‘bi-polar’ input signals. Verified by a pSpice simulation, this device can not only achieve a complete electric isolation of the HV system and the measurement system, but also realize a fine restore of the input signals.
Random errors in DIC caused by non-uniform image noise
Digital image correlation (DIC) is an optical measurement technique widely used in the field of experimental mechanics due to its practicality, flexibility, and reliability. The principle of DIC is to correlate the same point in the reference and deformed image. The performance of DIC is influenced by the image noise. Theoretical models have been presented to evaluate the random errors caused by image noise. However, these models are based on the assumption that the variance of image noise is uniform, while in practice the variance of image noise is non-uniform. In order to overcome this deficiency, in this paper, a formula of random errors of DIC corresponding to non-uniform noise is derived. The formula shows that the variance of image noise and image gradients has a coupling effect. In order to verify our theoretical analysis, actual experiments were carried out. The dependence between image noise and intensity was measured for two cameras; the DIC errors caused by image noise were measured experimentally; in order to take the effect of illumination into account, we measured the DIC errors in cases of both uniform and non-uniform illumination. The experimental results show good agreements with our theoretical analysis.
Design of a photoelastic modulator in the spin-exchange relaxation-free magnetometer
The spin-exchange relaxation-free (SERF) magnetometer as an ultra-precision magnetometer has been researched during recent times. The sensitivity of the signal measurement limits the accuracy of the magnetometer. The optical modulation method is used to detect the tiny optical rotation angle of the linear polarized (LP) light, and the modulator is improving from Faraday magneto-optic modulator to photoelastic modulator (PEM). However, the current commercial PEMs have several defects in the adoption of the magnetometer. First, considerable heat will reduce the PEM’s modulation precision; In addition, the big appearance will hamper the assembly of the magnetometer; Moreover, the products are unreliable in the small amplitude modulation. In order to overcome these drawbacks, a sort of PEM is designed by theoretical calculation and finite element simulation in the paper. The target PEM with 50kHz intrinsic frequency and 795nm transmission is composed of one hexahedron piezoelectric transducer (PZT) glued with one optical glass each other. About the PZT, the alpha quartz is determined by considering the vibration and temperature properties of the material, then a proper cut angel and size is calculated to satisfy the design target. Subsequently, the fused silica is used for its well optical property. In the final, a simulation is conducted to verify the feasibility and validity of the design.
Study the multi-band co-caliber infrared system optimize design and quantitative measurement
Ju guang Guo, Yong hui Ma, Zhi hui Yang
The main optical system of multi-band co-caliber infrared system is designed by using a Cassegrain telescope whose primary mirror (PM) and secondary mirror (SM) are aspherical form, and the structure of which is using total reflection system for the former level, the refractive lens group for the stage. After the target radiation to reach the primary mirror, reflecting onto the secondary mirror, and on top of toggling the spectral radiometric flux , respectively, which is reflected by different spectrum region, transmit to infrared focal plane array (IR FPA) for each other imaging detector. Then, photoelectric converse those information which were received by IRFPA. The output signal of detectors are processed and displayed by Read-Out Integrated Circuit (ROIC). We are confirming the image quality of different bands during system model optimization design. According to the specification of design system, establishing the measurement program of quantitative study. The results experimental measurement shows that the optimized design of the optical system has good validity.
Construction of dark spherical spot array using an amplitude-modulated radially polarized beam
Yanzhong Yu, Meng Li, Li Long, et al.
A simple and flexible method is presented for constructing a dark spherical spot array with the prescribed spot number and interval along the optical axis. Through reversing the field radiated from a uniform magnetic current line source in combination with an electric current line source having a cosine-squared taper, the desired focal field can be realized in the 4Pi focusing system. The required incident field on the pupil plane can be obtained by solving the inverse problem and is found to be an amplitude-modulated radially polarized beam.
An adaptive line enhancement method for UWB proximity fuze signal processing based on correlation matrix estimation with time delay factor
Signal processing for an ultra-wideband radio fuze receiver involves some challenges: it requires high real-time performance; the output signal is mixed with broadband noise; and the signal-to-noise ratio (SNR) decreases with increased detection range. The adaptive line enhancement method is used to filter the output signal of the ultra-wideband radio fuze receiver, and thus suppress the wideband noise from the output signal of the receiver and extract the target characteristic signal. The filter input correlation matrix estimation algorithm is based on the delay factor of an adaptive line enhancer. The proposed adaptive algorithm was used to filter and reduce noise in the output signal from the fuze receiver. Simulation results showed that the SNR of the output signal after adaptive noise reduction was improved by 20 dB, which was higher than the SNR of the output signal after finite impulse response (FIR) filtering of around 10 dB.
Research of the penetration gas methods of measuring barrier property of OLED packaging materials by mass spectrometry
Measuring penetration rates of water vapor and oxygen though OLED packaging materials by mass spectrometry is a new method. Currently, the sampling of penetration gas is dynamic sampling method. The sensitivity of this method is magnitude of 10-4 g/m2day, which can not reach the ideal magnitude of 10-6 g/m2day. Static accumulation sampling method for improving sensitivity of measuring is present in this paper. Comparing with dynamic sampling method, the sensitivity of this sampling method has been improved 1-2 magnitudes. The devices of static accumulation sampling method have been designed. The experiments of measuring penetration rates of water vapor and oxygen through packaging materials have been done. The results and analysis of the experiments have been introduced.
Discrimination of three typical amino acids using PARAFAC
Hui Yang, Xue Xiao, Xuesong Zhao, et al.
The intrinsic fluorescence characteristics of tryptophan, tyrosine and phenyloalanine were presented in this paper. The excitation/emission wavelength of tryptophan, tyrosine and phenyloalanine locate at λex/λem=280/350nm, 275nm/303 and 260/280nm respectively. The excitation and emission bands of these bio-fluorophores are quite overlapped within the EEM area whose excitation wavelength/emission wavelength scope is 230-270nm/260-340nm. Using the PARAFAC algorithm, 10 tryptophan, tyrosine and phenyloalanine mixed solutions and three compound amino acids samples were successfully decomposed, the emission profiles, excitation profiles, central wavelengths and the concentration of the three components were retrieved with high precision, and finally, the tyrosine and taurine were detected from 1st and 2nd sample respectively.
Variable aberration generator using a high-order even aspheric singlet for testing optical surfaces
Traditional null optics is generally designed for a particular optical surface. It must be redesigned when the test surface is changed no matter the null optic is reflective, transmitted or a CGH. Development of advanced optical machining and testing based on deterministic figuring and null test makes it possible to apply high-order aspheres. This paper presents a plano-concave singlet to realize variable aberration correction for testing different surfaces. The concave surface is an even asphere with high-order terms. By changing the axial distances among the transmission sphere, the null singlet and the test surface, variable aberrations are generated to meet the aberration balance requirement for various surfaces. The residual aberrations are confirmed within the vertical dynamic range of measurement of the interferometer. It enables flexible testing of optical surfaces without dedicated null optics. The optical design verifies that the aspheric singlet can be used to test conic surfaces with different conic constant and radius of curvature ranging from ellipsoid, paraboloid to hyperboloid and an even asphere.
Q-adjusting technique applied to vertical deflections estimation in a single-axis rotation INS/GPS integrated system
Jing Zhu, Xingshu Wang, Jun Wang, et al.
Former studies have proved that the attitude error in a single-axis rotation INS/GPS integrated system tracks the high frequency component of the deflections of the vertical (DOV) with a fixed delay and tracking error. This paper analyses the influence of the nominal process noise covariance matrix Q on the tracking error as well as the response delay, and proposed a Q-adjusting technique to obtain the attitude error which can track the DOV better. Simulation results show that different settings of Q lead to different response delay and tracking error; there exists optimal Q which leads to a minimum tracking error and a comparatively short response delay; for systems with different accuracy, different Q-adjusting strategy should be adopted. In this way, the DOV estimation accuracy of using the attitude error as the observation can be improved. According to the simulation results, the DOV estimation accuracy after using the Q-adjusting technique is improved by approximate 23% and 33% respectively compared to that of the Earth Model EGM2008 and the direct attitude difference method.
Measurements of density, pressure and temperature in the middle atmosphere with Rayleigh lidar
Ground-based observations of the middle atmospheric density, pressure and temperature profiles can be obtained by lidar. A single-wavelength Rayleigh lidar system based at Hefei (31°N,117°E) has been used to measure the atmospheric density, pressure and temperature in the middle atmosphere in night in the altitude range from about 25 to 40 km. The structure of Rayleigh lidar system, principles of middle atmospheric density, pressure and temperature measurement which is based on the Rayleigh scattering theory and method to retrieve atmospheric density, pressure and temperature profiles were described respectively. This instrument combined a 500mW Nd:YAG laser transmitter with a 0.4 m receiver mirror to observe returns from altitudes between 25km and 40km.The lidar observed atmosphere density, pressure and temperature profiles are validated through comparison with the measure data provided by sounding balloon. According to the data from actual measurement, the inversion of the vertical distribution of middle atmosphere density, pressure and temperature are in good agreement with the result of sounding balloon. Generally, in the altitude range 25 to 40 km, the density ratio profile of Rayleigh lidar to the sounding balloon density fluctuates between 0.98 and 1.10, the pressure ratio profile of Rayleigh lidar to the sounding balloon is between 0.99 and 1.06 and the deviation of the temperature is less than 6 k.
Filtered back-projection reconstruction of photo-acoustic imaging based on an modified wavelet threshold function
Zhong Ren, Guodong Liu, Zhen Huang
In this study, the filtered back-projection algorithm was used to reconstruct the photoacoustic imaging. To improve the quality of the reconstructed image, the wavelet threshold denoising method was combined into the filtered back-projection reconstruction algorithm. To obtain the reconstructed effect of the photoacoustic imaging, a modified wavelet threshold function was proposed. To verify the feasibility of the modified wavelet threshold function, the simulation experiments of the standard test phantom were performed by using three different wavelet threshold functions. Compared with the soft- and hard-threshold functions, the modified wavelet threshold function has better denoised and reconstructed effect. Moreover, the peak signal-to-noises ratio (PSNR) value of the modified function is largest, and its mean root square error (MRSE) value is lest than that of two others. Therefore, the filtered back-projection reconstruction algorithm combined with the modified wavelet threshold function has potential value in the reconstruction of the photoacoustic imaging.
Evaluation of the user experience of “astronaut training device”: an immersive, vr-based, motion-training system
Kang Yue, Danli Wang, Xinpan Yang, et al.
To date, as the different application fields, most VR-based training systems have been different. Therefore, we should take the characteristics of application field into consideration and adopt different evaluation methods when evaluate the user experience of these training systems. In this paper, we propose a method to evaluate the user experience of virtual astronauts training system. Also, we design an experiment based on the proposed method. The proposed method takes learning performance as one of the evaluation dimensions, also combines with other evaluation dimensions such as: presence, immersion, pleasure, satisfaction and fatigue to evaluation user experience of the System. We collect subjective and objective data, the subjective data are mainly from questionnaire designed based on the evaluation dimensions and user interview conducted before and after the experiment. While the objective data are consisted of Electrocardiogram (ECG), reaction time, numbers of reaction error and the video data recorded during the experiment. For the analysis of data, we calculate the integrated score of each evaluation dimension by using factor analysis. In order to improve the credibility of the assessment, we use the ECG signal and reaction test data before and after experiment to validate the changes of fatigue during the experiment, and the typical behavioral features extracted from the experiment video to explain the result of subjective questionnaire. Experimental results show that the System has a better user experience and learning performance, but slight visual fatigue exists after experiment.
Random error model andexperiment of fiber Bragg grating acceleration sensing system
Qinpeng Liu, Haiwei Fu, Zhen’an Jia, et al.
The random error model for evaluating FBG dynamic sensing system is proposed and established by using Allan variance, and the error recognition is experimentally demonstrated. The composition of the FBG sensing system, the characteristic of random error and error source for FBG acceleration sensing system are analyzed. The random error theoretical model based on the FBG acceleration sensing system is proposed and analyzed. In order to experimentally perform stability characterization of the system, the static output signal is achieved, and Allan variance curve is obtained by data processing, and the main coefficients of the error source can be further obtained. The model based on the Allan variance adequately demonstrates that it is feasible to evaluate the FBG system, which provides the basis for further designing, improvements and developing.
Goos-Hanchen shifts at a resonance angle of a two-prism structure using COMSOL multiphysics
Wenjing Zhang, Zhiwei Zhang, Peng Yang, et al.
We simulated and analyzed Goos–Hänchen (GH) shifts of 633 nm polarized light through a two-prism structure, consisting of a right triangle prism and an isosceles triangle prism with Kretschmann–Raether configuration, by comparing the results from COMSOL Multiphysics (CM) simulation software with that of a stationary-phase analysis (SPA). For this two-prism structure, using a gold film that of thickness 45 nm, the maximum positive GH shift, obtained using SPA at the resonance angle of 44.1°, was 354 μm. Using CM at an incident angle of 43.8°, we found the maximum positive GH shift of 9.45 μm. The results obtained using CM are in agreement with those obtained by the SPA around the resonance angle, although the enhancement effect from CM is much less than that of SPA. This is because SPA depends on the differentiation of the phase shift with respect to the incident angle, while a drastic phase shift occurs at the resonance angle. These results are useful for designing high-sensitivity SPR sensors based on GH shift measurement and for application in waveguide-type SPR devices, with sizes in the order of micro millimeter.
Status of astigmatism-corrected Czerny-Turner spectrometers
In order to analysis and design the Czerny-Turner structure spectrometer with the high resolution and high energy reception, various astigmatism methods of the Czerny-Turner structure are reported. According to the location of plane grating, the astigmatism correction methods are divided into two categories, one is the plane grating in divergent illumination, another is the plane grating in parallel illumination. Basing on the different methods, the anastigmatic principle and methods are analyzed, the merits and demerits of the above methods are summarized and evaluated. The theoretical foundation for design of broadband eliminating astigmatism Czerny-Turner spectrometer and the reference value for the further design work are laid by the summary and analyzing in this paper.
A FBG pulse wave demodulation method based on PCF modal interference filter
Cheng Zhang, Shan Xu, Ziqi Shen, et al.
Fiber optic sensor embedded in textiles has been a new direction of researching smart wearable technology. Pulse signal which is generated by heart beat contains vast amounts of physio-pathological information about the cardiovascular system. Therefore, the research for textile-based fiber optic sensor which can detect pulse wave has far-reaching effects on early discovery and timely treatment of cardiovascular diseases. A novel wavelength demodulation method based on photonic crystal fiber (PCF) modal interference filter is proposed for the purpose of developing FBG pulse wave sensing system embedded in smart clothing. The mechanism of the PCF modal interference and the principle of wavelength demodulation based on In-line Mach-Zehnder interferometer (In-line MZI) are analyzed in theory. The fabricated PCF modal interferometer has the advantages of good repeatability and low temperature sensitivity of 3.5pm/°C from 25°C to 60°C. The designed demodulation system can achieve linear demodulation in the range of 2nm, with the wavelength resolution of 2.2pm and the wavelength sensitivity of 0.055nm-1. The actual experiments’ result indicates that the pulse wave can be well detected by this demodulation method, which is in accordance with the commercial demodulation instrument (SM130) and more sensitive than the traditional piezoelectric pulse sensor. This demodulation method provides important references for the research of smart clothing based on fiber grating sensor embedded in textiles and accelerates the developments of wearable fiber optic sensors technology.
Dynamic X-ray phase imaging based on an aperture array
Gongxiang Wei, Yunyan Liu, Tiqiao Xiao
A noniterative method for dynamic X-ray phase imaging from the recorded far-field diffraction intensity distribution of the object wavefront, sampled by a sampling plate, is proposed. The sampling plate consists of a two-dimensional (2D) aperture array and a central reference aperture. In this method, the complex amplitude of the object wavefront, especially the phase that carries the inner refraction information, can be retrieved from the inverse Fourier transform of the diffraction intensity distribution by directly filtering with a same aperture array. As this method requires only a single measurement of the diffraction intensity pattern and does not need any iterative algorithm, in principle, it provides a practical approach for dynamic phase imaging in a wide range of wavelengths. The experimental results demonstrated that the proposed method is practicable. The proposed may have potential application in high-efficiency phase retrieval for coherent diffraction imaging and phase contrast imaging.
Refractive index sensing characteristics of D-shape double core photonic crystal fiber based on surface plasmon resonance
Feng Liu, Shi-tao Li, Xuan Guo
A refractive index (RI) sensor and its sensing characteristics based on surface plasmon resonance (SPR) of D-shape double core photonic crystal fiber (DC-PCF) are researched theoretically in this letter. The basic sensor principle is the SPR light intensity modulation of polished D-shape DC-PCF. The influence of the polished angle and depth on the DC-PCF SPR characteristics is discussed extensively by using the finite element method (FEM). The effects of the coated metal type and its layer thickness on the resonant intensity are also analyzed. The relationship between the analyte RI and resonant wavelength is numerically simulated. The theoretical results show that the sensor’s RI sensitivity exhibits about 2000 nm/RIU with the structure parameters of 60° polished angle, 58.5μm polished depth and 70nm thickness of the silver layer. Furthermore, if the single wavelength laser is chosen, the detection of the two core light intensity difference will improve the ability of resistance to environmental interference. The simple sensor structure and high sensitivity can make this technology for online refractive index measurement in widespread areas.
Novel glucose fiber sensor combining ThFBG with GOD
Mengmeng Li, Ciming Zhou, Dian Fan, et al.
We propose a novel glucose fiber optic sensor combining a thinned cladding fiber Bragg grating (ThFBG) with glucose oxidase (GOD). By immobilizing GOD on the surface of a ThFBG, the fabricated sensor can obtain a high specificity to glucose. Because of the evanescent field, the sensor is very sensitive to the ambient refractive index change arising from the catalytic reaction between glucose and GOD. A four-level fiber model was simulated and verified the precision of the sensing principle. Two methods, glutaraldehyde crosslinking method (GCM) and 3-aminopropyl triethoxysilane covalent coupling method (ATCCM), were experimentally utilized to immobilize GOD. And sensor fabricated with the method ATCCM shows a measurement range of 0-0.82 mg/mL which is better than the sensor fabricated with the method GCM with measurement range of 0-0.67 mg/mL under the same condition. By using ATCCM to immobilize GOD with different concentrations, three sensors were fabricated and used for glucose measurement by monitoring the Bragg wavelength (λb) shifts, the results indicate a good linear relationship between wavelength shift and glucose concentration within a specific range, and the measurement range increases as GOD concentration increases. The highest sensitivity of sensor reaches up to 0.0549 nm/(mg.mL-1). The proposed sensor has distinct advantages in sensing structure, cost and specificity.
Optical skin friction measurement technique in hypersonic wind tunnel
Xing Chen, Dapeng Yao, Shuai Wen, et al.
Shear-sensitive liquid-crystal coatings (SSLCCs) have an optical characteristic that they are sensitive to the applied shear stress. Based on this, a novel technique is developed to measure the applied shear stress of the model surface regarding both its magnitude and direction in hypersonic flow. The system of optical skin friction measurement are built in China Academy of Aerospace Aerodynamics (CAAA). A series of experiments of hypersonic vehicle is performed in wind tunnel of CAAA. Global skin friction distribution of the model which shows complicated flow structures is discussed, and a brief mechanism analysis and an evaluation on optical measurement technique have been made.
An endoscope designed with 3D measurement functions
Qi-hai Zhu, Zheng-lin Li, Li-qiang Wang, et al.
The endoscopic system is widely used in medical and industrial areas, but how to realize the high-precision three-dimensional measurement in the limited space scale still faces many challenges. A method based on the four-step phase-shifting structured light illumination is proposed in this paper for endoscopic 3D measurements. Structured light of which the adjacent phase shift is 90 degrees is generated by the different parts of the time-sharing lighting stripe grating of the optical fiber bundle; CMOS camera is used to collect four structured light images with the phase shift. Finally, the method of four-step phase-shifting is used to demodulate 3D information from the images, and a relative measurement accuracy of 95% within the range of 15-200mm can be obtained. The endoscope with a field of view of 90 degrees, a image resolution of 1280 * 800 and 3D depth calculation time of 0.2 seconds has advantages of simple structure, large field of view, high accuracy and good real-time measurement.
Distributed acoustic sensing system using an identical weak fiber Bragg grating array
Sheng Liu, Xinying Han, Hongqiao Wen
We propose and experimentally demonstrate a distributed acoustic sensing system using an identical weak fiber Bragg grating array. Phase, frequency and location information of vibration can be demodulated by using a path-match interferometry method. 3×3 coupler demodulation technique is employed to eliminate signal fading in interferometer. Experiments on detecting acoustic wave generated by PZT show that the system is capable of measuring vibrations of up to 1000 Hz over 1.6 km with 2.5m spatial resolution.
Research on the calibration of ultraviolet energy meters
Fangsheng Lin, Dejin Yin, Tiecheng Li, et al.
Ultraviolet (UV) radiation is a kind of non-lighting radiation with the wavelength range from 100nm to 400nm. Ultraviolet irradiance meters are now widely used in many areas. However, as the development of science and technology, especially in the field of light-curing industry, there are more and more UV energy meters or UV-integrators need to be measured. Because the structure, wavelength band and measured power intensity of UV energy meters are different from traditional UV irradiance meters, it is important for us to take research on the calibration. With reference to JJG879-2002, we SIMT have independently developed the UV energy calibration device and the standard of operation and experimental methods for UV energy calibration in detail. In the calibration process of UV energy meter, many influencing factors will affect the final results, including different UVA-band UV light sources, different spectral response for different brands of UV energy meters, instability and no uniformity of UV light source and temperature. Therefore we need to take all of these factors into consideration to improve accuracy in UV energy calibration.
Time-resolved fluorescence spectroscopy of oil spill detected by ocean lidar
Xiao-long Li, Yong-hua Chen, Jie Li, et al.
Based on time-resolved fluorescence of oils, an oceanographic fluorescence Lidar was designed to identify oil pollutions. A third harmonic (at 355nm) of Nd:YAG laser is used as the excitation source, and the fluorescence intensities and lifetimes of oil fluorescence at wavelength from 380 nm to 580 nm are measured by an intensified CCD (ICCD). In the experiments, time-resolved fluorescence spectra of 20 oil samples, including crude oils, fuel oils, lubricating oil, diesel oils and gasoline, are analyzed to discuss fluorescence spectral characteristics of samples for oil classification. The spectral characteristics of oil fluorescence obtained by ICCD with delay time of 2 ns, 4 ns, and 6 ns were studied by using the principal component analysis (PCA) method. Moreover, an efficient method is used to improve the recognition rate of the oil spill types, through enlarging spectral differences of oil fluorescence at different delay times. Experimental analysis shows that the optimization method can discriminate between crude oil and fuel oil, and a more accurate classification of oils is obtained by time-resolved fluorescence spectroscopy. As the result, comparing to traditional fluorescence spectroscopy, a higher recognition rate of oil spill types is achieved by time-resolved fluorescence spectroscopy which is also a feasibility technology for Ocean Lidar.
Design on wireless auto-measurement system for lead rail straightness measurement based on PSD
Xiugang Yan, Shuqin Zhang, Dengfeng Dong, et al.
Straightness detection is not only one of the key technologies for the product quality and installation accuracy of all types of lead rail, but also an important dimensional measurement technology. The straightness measuring devices now available have disadvantages of low automation level, limiting by measuring environment, and low measurement efficiency. In this paper, a wireless measurement system for straightness detection based on position sensitive detector (PSD) is proposed. The system has some advantage of high automation-level, convenient, high measurement efficiency, easy to transplanting and expanding, and can detect straightness of lead rail in real-time.
A focal plane metrology system and PSF centroiding experiment
Haitao Li, Baoquan Li, Yang Cao, et al.
In this paper, we present an overview of a detector array equipment metrology testbed and a micro-pixel centroiding experiment currently under development at the National Space Science Center, Chinese Academy of Sciences. We discuss on-going development efforts aimed at calibrating the intra-/inter-pixel quantum efficiency and pixel positions for scientific grade CMOS detector, and review significant progress in achieving higher precision differential centroiding for pseudo star images in large area back-illuminated CMOS detector. Without calibration of pixel positions and intrapixel response, we have demonstrated that the standard deviation of differential centroiding is below 2.0e-3 pixels.
Modular interference characteristics and beat length of a two-hole photonic crystal fiber
Xin Lu, Ying Liu, Xuan Guo
We show the mode propagation characteristics of fundamental and second-order modes in a two-mode highly birefringent photonics crystal fiber (HB-PCF) under a longitudinal strain. The two-mode operation range in HB-PCF is researched. Within this range, the modular interference beat length LMB in each Eigen polarization are simulated with respect to wavelength λ , and the fitting equations between LMB and λ are presented. We also measure LMB at λ = 532nm , respectively. The results show that the theoretical simulation is basically in accordance with the experimental data.
Theoretical analysis and estimation of decorrelation phase error in digital holographic interferometry
Tao Zhang, Yining Yan, Qingkai Mo
In order to theoretically analyze and estimate decorrelation phase error in digital holographic interferometry, the principle of digital holographic imaging system is introduced in this paper, and general point spread function (PSF) of digital holographic system is derived and its approximate function is obtained. According to the characteristics of the digital holographic imaging in accordance with the laws of statistical optics, the expression of complex amplitude standard deviation of σA, σB and σC in each region of the double exposure time and the relationship between the degree of decorrelation are derived, and the expression of the phase error of decorrelation is given. It is simulated in MATLAB, simulative results indicate that statistical properties of decorrelation phase error obtained through theory analysis correspond to decorrelation phenomenon. And the measuring condition, in digital holography interferometry, which decorrelation degrees between the holographies of every double exposure should satisfy ρx + ρy <0.1, is derived.
Experimental evidence for formation mechanism of regular circular fringes
Y. Wang, R. Zhu, G. Wang, et al.
Laser active suppressing jamming is one of the most effective technologies to cope with optoelectric imaging systems. In the process of carrying out laser disturbing experiment, regular circular fringes often appeared on the detector, besides laser spot converging by optical system. First of all, the formation of circular fringes has been experimentally investigated by using a simple converging lens to replace the complex optical system. Moreover, circular fringes have been simulated based on the interference theory of coherent light. The coherence between the experimental phenomena and the simulated results showed that the formation mechanism of regular circular fringes was the interference effect between reflected light by back surface of lens and directly refractive light on the detector. At last, the visibility of circular fringes has been calculated from 0.05 to 0.22 according to the current plating standard of lens surface and manufacture technique of optoelectric detector.
Research on method and device of non-disperse atomic fluorescence excitation light source impurity detection
Yaqing Jia, Hong Wu, Zhengsheng Shen
Analysis on the impurities of non-dispersive atomic fluorescence exciting light source is given. A method is proposed to detect this kind of light source impurity by using spectral analysis, and a set of light source detection standard device was accomplished. Corresponding algorithm and application software were developed. The detection wavelength range of the device is 190~350 nm, the maximum allowable error is ±0.3 nm. The device achieved fast detection of the excitation light source impurity and could be verified by the experimental results.
Design and realization of photoelectric instrument binocular optical axis parallelism calibration system
Jia-ju Ying, Yu-dan Chen, Jie Liu, et al.
The maladjustment of photoelectric instrument binocular optical axis parallelism will affect the observe effect directly. A binocular optical axis parallelism digital calibration system is designed. On the basis of the principle of optical axis binocular photoelectric instrument calibration, the scheme of system is designed, and the binocular optical axis parallelism digital calibration system is realized, which include four modules: multiband parallel light tube, optical axis translation, image acquisition system and software system. According to the different characteristics of thermal infrared imager and low-light-level night viewer, different algorithms is used to localize the center of the cross reticle. And the binocular optical axis parallelism calibration is realized for calibrating low-light-level night viewer and thermal infrared imager.
New time-domain three-point error separation methods for measurement roundness and spindle error motion
Wenwen Liu, Tingting Tao, Hao Zeng
Error separation is a key technology for online measuring spindle radial error motion or artifact form error, such as roundness and cylindricity. Three time-domain three-point error separation methods are proposed based on solving the minimum norm solution of the linear equations. Three laser displacement sensors are used to collect a set of discrete measurements recorded, by which a group of linear measurement equations is derived according to the criterion of prior separation form (PSF), prior separation spindle error motion (PSM) or synchronous separation both form and spindle error motion (SSFM). The work discussed the correlations between the angles of three sensors in measuring system, rank of coefficient matrix in the measurement equations and harmonics distortions in the separation results, revealed the regularities of the first order harmonics distortion and recommended the applicable situation of the each method. Theoretical research and large simulations show that SSFM is the more precision method because of the lower distortion.
Design and experiment of an adjustable full polarization imaging measurement system
Jin-bao Yang, Wei-li Chen, Yuan-nan Xu, et al.
A new scheme of adjustable full polarization imaging measurement system was presented in this paper in order to study the polarization properties of light. It realized the measurement and flexible switching of the linear, circular and elliptical polarization modes in the active and passive mode through the combination of a linear polarizer, 1/4 wave plate and angle adjusting device. A prototype of the adjustable full polarization imaging measurement system was developed and tested in the paper. The adjustable full polarization imaging system was mainly composed of a polarization transmitting unit, a polarization receiving unit and an imaging control unit. In the active mode, the polarization emission unit worked and emitted the active polarized light while in passive mode, the emission unit did not work, and the system got image via natural light. The entire system was integrated into an image sensor with compact structure and good consistency, which can be widely used in the laboratory and field polarization imaging measurement and quantitative analysis.
Two-dimensional imaging of gas temperature and concentration based on hyperspectral tomography
Ming-yuan Xin, Xing Jin, Guang-yu Wang, et al.
Two-dimensional imaging of gas temperature and concentration is realized by hyperspectral tomography, which has the characteristics of using multi-wavelengths absorption spectral information, so that the imaging could be accomplished in a small number of projections and viewing angles. A temperature and concentration model is established to simulate the combustion conditions and a total number of 10 near-infrared absorption spectral information of H2O is used. An improved simulated annealing algorithm by adjusting search step is performed the main search algorithm for the tomography. By adding random errors into the absorption area information, the stability of the algorithm is tested, and the results are compared with the reconstructions provided by algebraic reconstruction technique which takes advantage of 2 spectral information contents in imaging. The results show that the two methods perform equivalent in low-level noise environment, but at high-level, hyperspectral tomography turns out to be more stable.
Tolerance analysis on diffraction efficiency and polychromatic integral diffraction efficiency for harmonic diffractive optics
In this dissertation, the mathematical model of effect of manufacturing errors including microstructure relative height error and relative width error on diffraction efficiency for the harmonic diffractive optical elements (HDEs) is set up. According to the expression of the phase delay and diffraction efficiency of the HDEs, the expression of diffraction efficiency of refraction and diffractive optical element with the microstructure height and periodic width errors in fabrication process is presented in this paper. Furthermore, the effect of manufacturing errors on diffraction efficiency for the harmonic diffractive optical elements is studied, and diffraction efficiency change is analyzed as the relative microstructure height-error in the same and in the opposite sign as well as relative width-error in the same and in the opposite sign. Example including infrared wavelength with materials GE has been discussed in this paper. Two kinds of manufacturing errors applied in 3.7~4.3um middle infrared and 8.7-11.5um far infrared optical system which results in diffraction efficiency and PIDE of HDEs are studied. The analysis results can be used for manufacturing error control in micro-structure height and periodic width. Results can be used for HDEs processing.
Multi-platform laser communication networking optical antenna system design
In this paper, a new conclusion based on rotating parabolic model and a different scheme of laser communication networking antenna system has been put forward in the paper. Based on rotating parabolic antenna, a new theory of the optical properties have been deduced, which can realize larger dynamic, duplex, networking communications among multiple platforms in 360° azimuth and pitch range. Meanwhile, depending on the operation mode of the system, multiple mathematical optimization models have been established. Tracking communication range, emission energy efficiency and receiving energy efficiency have been analyzed and optimized. Relationship among opening up and low apertures, the lens unit aperture, focal length of lens unit as well as rotating parabolic focal length have been analyzed. Tracking pitching range and emission energy utilization has carried on the theoretical derivation and optimization and networking platform link between energy receiver and transmitter has been analyzed. Taking some parameters of this new system into calculation, optimized results can be utilized with MATLAB software for its application and system of communication engineering. The rotating parabolic internal can form a hollow structure, which is utilized for miniaturization, light-weighted design and realize duplex communication in a wide range and distance. Circular orbit guidance is the modern way used in dynamic tracking system. The new theory and optical antenna system has widespread applications value as well.
Spectral responsivity calibration of silicon photodetectors using monochromator-based cryogenic radiometer
Cryogenic radiometer is the most accurate measurement setup for optical power measurement, underpinning the radiometry and photometry standards in many countries around the world. Typically cryogenic radiometers are designed for laser injection, and the measurement uncertainty at the laser wavelengths can reach 10-4. The National Institute of Metrology China has used the laser cryogenic radiometer to realize the absolute spectral responsivity of the detectors. In order to achieve spectral responsivity measurement ability in a wider spectral range, we establish the new spectral type cryogenic radiometer system using a supercontinuum white light source and a double monochromator, covering spectral range of 400 nm - 1100 nm. Establishment of the new cryogenic radiometer will greatly enhance the entire optical radiation measurement capablities, such as radiation illuminance and luminance measurement. A series of experiments have been undertaken, including measurement of noise level, heating equivalence, wavelength calibration, power stabilization, detector characteristics measurement, and different light source spectral radiation power measurement. The measurement uncertainties are analyzed and presented.
Phase retrieval based on cosine grating modulation and transport of intensity equation
Ya-ping Chen, Quan-bing Zhang, Hong Cheng, et al.
In order to calculate the lost phase from the intensity information effectively, a new method of phase retrieval which based on cosine grating modulation and transport of intensity equation is proposed. Firstly, the cosine grating is loaded on the spatial light modulator in the horizontal and vertical direction respectively, and the corresponding amplitude of the light field is modulated. Then the phase is calculated by its gradient which is extracted from different direction modulation light illumination. The capability of phase recovery of the proposed method in the presence of noise is tested by simulation experiments. And the results show that the proposed algorithm has a better resilience than the traditional Fourier transform algorithm at low frequency noise. Furthermore, the phase object of different scales can be retrieved using the proposed algorithm effectively by changing the frequency of cosine grating, which can control the imaging motion expediently.
Measurement system for lens thickness based on low-coherent fiber-optic interferometry
A new non-contact and wide-range measurement system for lens thickness based on low-coherent interferometry was proposed in this paper. In this system the reference mirror was set moveable, and high-resolution grating ruler was utilized to record real-time position of mirror. Then lens central thickness was calculated on the basis of the relative distance between two interference fringes’ peak. Compared with the traditional thickness measurement technology based on low-coherent interferometry the new method has made great progresses. Firstly beam splitting and interference were separated by use of several fiber couplers which realized appropriate intensity ratio of probe beam and reference beam, and enhanced the contrast of interference fringes. Then zoom lens was designed to improve intensity coupling efficiency between the fiber system and lens system. Finally conversion from optical signal to electronic signal was accomplished by using balance detection, which was good for improving the signal-to-noise ratio. In this paper, firstly the basic principle of measuring device was put forward, namely low-coherent interference technique. Then design of the measuring device and solution for the main problems was introduced in detail. Experimental results of device was given in the end of article, which proved that the relative error of measurement was less than 0.05%.
Analyzing the structure of the optical path difference of the supersonic film cooling
Haolin Ding, Shihe Yi, Jia Fu, et al.
While high-speed aircraft are flying in the atmosphere, its optical-hood is subjected to severe aerodynamic heating. Supersonic film cooling method can effectively isolate external heating, but the flow structures formed by the supersonic film cooling can cause the beam degradation and affect the imaging quality. To research the aero-optics of supersonic film cooling, an experimental model was adopted in this paper, its mainstream Mach number 3.4, designed jet Mach number 2.5, measured jet Mach number 2.45. High-resolution images of flow were acquired by the nano-based planar laser scattering (NPLS) technique, by reconstructing the density field of supersonic film cooling, and then, the optical path difference (OPD) were acquired by the ray-tracing method. Depending on the comparison between K-H vortex and OPD distribution, the valleys of OPD correspond to the vortex ‘rollers’ and the peaks to the ‘braids’. However, the corresponding relationship becomes quite irregular for the flow field with developed vortices, and cannot be summarized in this manner. And then, the OPD were analyzed by correlation function and structure function, show that, there is a relationship between the shape of OPD correlation function and the vortex structure, the correlation function type changed with the development of the vortex. The correctness that the mixing layer makes a main contribution to the aero-optics of supersonic film cooling was verified, and the structure function of aero-optical distortion has a power relationship that is similar to that of atmospheric optics. At last, the power spectrum corresponding to the typical region of supersonic film cooling were acquired by improved periodgram.
Accuracy of a reference instrument for specular gloss measurements
Tiecheng Li, Lei Lai, Leibing Shi, et al.
Specular gloss is the perception by an observer of the mirror-like appearance of a surface. The measurement of specular gloss consists of comparing the luminous flux reflected from an object to that reflected from a gloss reference standard. The accuracy of specular gloss measurements depends not only on the characteristics of the instrument but also on the properties of the gloss reference standard. Experiments have been performed to analyze the possible sources of error such as gloss reference standard variation, photodetector linearity and measurement repeatability, which are three most important components of uncertainty. The results indicate that the instrument should be carefully examined before the specular gloss measurement in order to acquire a satisfied result.
Study of laser energy standard and establishment of calibration device
Ming Xia, Jianqiang Gao, Junwen Xia, et al.
This paper studied the standard laser energy meter. A self calibration of the thermoelectric type standard laser energy meter is developed, which is provided with a suitable electric heater. It can be used to simulate and replace the equivalent thermal effect, and to realize the absolute measurement of the laser energy. Because the standard laser energy meter can bulk absorb laser radiation, it can bear higher laser energy density. The material absorption spectrum of the standard laser energy meter is relatively flat from the ultraviolet to the infrared, so it can be used for the measurement of laser energy at any wavelength. In addition, an electric calibration instrument is developed. The electric calibration instrument can be directly displayed or synchronous display by the digital frequency meter. The laser energy calibration device is composed of standard laser energy meter, pulsed laser source, monitoring system, digital multi meter and complete set of electric calibration system. Laser energy calibration device uses split beam detection method. The laser is divided into two beams by means of a wedge shaped optical beam splitter. A laser energy meter is used to monitor the change of the reflected light to reduce the influence of the output laser energy stability of the pulsed laser source, thereby improving the uncertainty of the calibration result. The sensitivity, correction factor and indication error of the laser energy meter can be calibrated by using the standard laser energy meter and the under calibrated laser energy meter to measure the transmission laser beam.
Beam shaping in flow cytometry with diffractive optical elements
Weidong Qu, Derong Li, Peng Jian
Focusing elements are usually employed in the flow cytometry to focus the input laser beam into elliptically shaped Gaussian beam in order to increase power for excitation of fluorescence for high signal-to-noise ratio (SNR). While in order to ensure repeatable and reliable signal generation for accurate population discrimination - despite slight deviations of the cell from the flow centre, the shaped beam should be a cubic diffraction region with uniform power intensity across the cell flow stream. However, it is hard for beam shaping with refractive optical elements. In this paper, we present a beam shaping system in flow cytometry with diffractive optical elements (DOEs) to shape the input laser beam to a cubic diffraction region with uniform power intensity. The phase distribution of the DOE is obtained by using the inverse Fresnel diffraction based layered holographic stereogram, and the cubic diffraction region with uniform power intensity within the cell flow channel is well reconstructed. Simulation results demonstrate the good performance of the new beam shaping system.
Design of wavefront coding optical system with annular aperture
Wavefront coding can extend the depth of field of traditional optical system by inserting a phase mask into the pupil plane. In this paper, the point spread function (PSF) of wavefront coding system with annular aperture are analyzed. Stationary phase method and fast Fourier transform (FFT) method are used to compute the diffraction integral respectively. The OTF invariance is analyzed for the annular aperture with cubic phase mask under different obscuration ratio. With these analysis results, a wavefront coding system using Maksutov-Cassegrain configuration is designed finally. It is an F/8.21 catadioptric system with annular aperture, and its focal length is 821mm. The strength of the cubic phase mask is optimized with user-defined operand in Zemax. The Wiener filtering algorithm is used to restore the images and the numerical simulation proves the validity of the design.
Analysis of wavelength error in spectral phase shifting of digital holographic microscopy
Jie Wang, Xiangchao Zhang, Xiaolei Zhang, et al.
Digital holographic microscopy is an attractive technology of precision measurement. Phase shifting is required to correctly reconstruct the measured surfaces from interferograms. Spectral phase shifting scheme, as an alternative approach of phase shifting, has drawn intensive attention in recent years. However, the wavelength modulated by the acousto-optic tunable filter (AOTF) is not sufficiently precise. As a consequence, severe measurement errors will be caused. In this paper, an iterative calibration algorithm is proposed. It estimates the unknown wavelength errors in the 3-step spectral phase shifting interferometry and then reconstructs the complex object wave. The actual wavelength is obtained by minimizing the difference between the measured and calculated intensities. Numerical examples have demonstrated that this algorithm can achieve very high accuracy over a wide range of wavelengths.
3D shape reconstruction of specular surfaces by using phase measuring deflectometry
Tian Zhou, Kun Chen, Haoyun Wei, et al.
The existing estimation methods for recovering height information from surface gradient are mainly divided into Modal and Zonal techniques. Since specular surfaces used in the industry always have complex and large areas, considerations must be given to both the improvement of measurement accuracy and the acceleration of on-line processing speed, which beyond the capacity of existing estimations. Incorporating the Modal and Zonal approaches into a unifying scheme, we introduce an improved 3D shape reconstruction version of specular surfaces based on Phase Measuring Deflectometry in this paper. The Modal estimation is firstly implemented to derive the coarse height information of the measured surface as initial iteration values. Then the real shape can be recovered utilizing a modified Zonal wave-front reconstruction algorithm. By combining the advantages of Modal and Zonal estimations, the proposed method simultaneously achieves consistently high accuracy and dramatically rapid convergence. Moreover, the iterative process based on an advanced successive overrelaxation technique shows a consistent rejection of measurement errors, guaranteeing the stability and robustness in practical applications. Both simulation and experimentally measurement demonstrate the validity and efficiency of the proposed improved method. According to the experimental result, the computation time decreases approximately 74.92% in contrast to the Zonal estimation and the surface error is about 6.68 μm with reconstruction points of 391×529 pixels of an experimentally measured sphere mirror. In general, this method can be conducted with fast convergence speed and high accuracy, providing an efficient, stable and real-time approach for the shape reconstruction of specular surfaces in practical situations.
A method to enhance the measurement accuracy of Raman shift based on high precision calibration technique
Raman spectrometers are usually calibrated periodically to ensure their measurement accuracy of Raman shift. A combination of a piece of monocrystalline silicon chip and a low pressure discharge lamp is proposed as a candidate for the reference standard of Raman shift. A high precision calibration technique is developed to accurately determine the standard value of the silicon's Raman shift around 520cm-1. The technique is described and illustrated by measuring a piece of silicon chip against three atomic spectral lines of a neon lamp. A commercial Raman spectrometer is employed and its error characteristics of Raman shift are investigated. Error sources are evaluated based on theoretical analysis and experiments, including the sample factor, the instrumental factor, the laser factor and random factors. Experimental results show that the expanded uncertainty of the silicon's Raman shift around 520cm-1 can acheive 0.3 cm-1 (k=2), which is more accurate than most of currently used reference materials. The results are validated by comparison measurement between three Raman spectrometers. It is proved that the technique can remarkably enhance the accuracy of Raman shift, making it possible to use the silicon and the lamp to calibrate Raman spectrometers.
Injection molding lens metrology using software configurable optical test system
Optical plastic lens produced by injection molding machine possesses numerous advantages of light quality, impact resistance, low cost, etc. The measuring methods in the optical shop are mainly interferometry, profile meter. However, these instruments are not only expensive, but also difficult to alignment. The software configurable optical test system (SCOTS) is based on the geometry of the fringe refection and phase measuring deflectometry method (PMD), which can be used to measure large diameter mirror, aspheric and freeform surface rapidly, robustly, and accurately. In addition to the conventional phase shifting method, we propose another data collection method called as dots matrix projection. We also use the Zernike polynomials to correct the camera distortion. This polynomials fitting mapping distortion method has not only simple operation, but also high conversion precision. We simulate this test system to measure the concave surface using CODE V and MATLAB. The simulation results show that the dots matrix projection method has high accuracy and SCOTS has important significance for on-line detection in optical shop.
Theoretical research and comparison of forces in optical tweezers based on ray optics method and T matrix method
Zhenggang Li, Huizhu Hu, ZhenHai Fu, et al.
Based on ray tracing method of ray optics (RO) theory and T-matrix method of electromagnetic scattering theory, we establish optical trap force model and calculate the optical trap force of trapped microspheres whose size is in the beam wavelength scale. Calculation results of axial and transverse trapping efficiency based on the two models agree qualitatively, but differ quantitatively. Then we introduce a trapping efficiency calculation deviation parameter to characterize the difference between these two methods, and analyze how the deviation parameter is influenced by trapped microsphere radius and trapping beam waist radius. Simulation result shows that best agreement between RO model and T matrix calculation method is met when a strongly focused laser beam traps a large microsphere in near the beam waist plane area. In such cases both ray optics approximation conditions and T matrix method approximate conditions are satisfied. Numerical results coincide well with theoretical expectations.
Experiment of inverse synthetic aperture ladar at 1.1km
Ning Wang, Ran Wang, Guangzuo Li, et al.
This manuscript describes an airborne SAL system for remote targets imaging. We have recently completed an experiment of ISAL at 1.1 km outdoor using the system. Relative motion was provided by a rotating platform with three cubes on while the SAL system kept stationary. System, signal collection, processing and the results are described in the paper. The result showed that the system had the ability to image for moving targets. Accurate rotating platform and complex target will be used to achieve further ISAL experiments on the next stage.
Vibration measurement based on the optical cross-correlation technique with femtosecond pulsed laser
Two vibration measurement methods with femtosecond pulsed laser based on the optical cross-correlation technique are presented independently in this paper. The balanced optical cross-correlation technique can reflect the time jitter between the reference pluses and measurement pluses by detecting second harmonic signals using type II phase-matched nonlinear crystal and balanced amplified photo-detectors. In the first method, with the purpose of attaining the vibration displacement, the time difference of the reference pulses relative to the measurement pluses can be measured using single femtosecond pulsed laser. In the second method, there are a couple of femtosecond pulsed lasers with high pulse repetition frequency. Vibration displacement associated with cavity length can be calculated by means of precisely measuring the pulse repetition frequency. The results show that the range of measurement attains ±150μm for a 500fs pulse. These methods will be suited for vibration displacement measurement, including laboratory use, field testing and industrial application.
The simulation and experiment research of harmonic signals based on wavelength modulation spectroscopy
Dong-sheng Qu, Yan-ji Hong, Guang-yu Wang, et al.
In order to improve the measurement based on the wavelength modulation spectroscopy technology, a new simulation method of harmonic signals is analyzed and studied. After choosing one H2O absorption line (7185.60cm-1), the transmitted laser signals can be simulated using the measured incident laser signals and fitted laser frequency signals. The simulation of harmonic signals can be realized after creating the lock-in amplifier and calibrated using measured second-harmonic signal. The reliability of this method can be verified according to compare the simulation results with experiment results. At last, the application of this method in the flow field diagnosis is analyzed. It can lay the foundation of engineering application based on wavelength modulation spectroscopy.
Calibration of angle of incidence of ellipsometer by autocollimator-based method
Wende Liu, Chi Chen, Qiming Fan, et al.
Accurate determination of the angle of incidence (AOI) of ellipsometer could improve the reliability of the model analysis, thus relieving possible parameter correlation, eliminating inconsistency which is often encountered by using reference samples of different sources to fit the AOI. In this work, firstly, various commercially available standard reference samples are used to retrieve the AOI and compared with each other, which demonstrates the difficulty to make a best choice. Then, the autocollimator-based method is proposed for the establishment of a metrological ellipsometer and the traceable calibration of the AOI is realized. For practical use, a simplified method which is often empirically employed in aligning optical elements is inspected and the validity and accuracy are verified experimentally. The experimental statistics indicate that, the accuracy (deviation from the “true” value) of the mean AOI could be determined in a worst case to be 0.03°, and by optimizing certain geometric conditions, the accuracy could be improved up to 0.0013° with a precision of 0.005° (standard deviation).
Numerical simulation research on wind field disturbance detecting with coherent laser
In order to grasp the information of wind field and disturbance in the airport in real time, and to ensure the safety of flight, a method of detecting wind field disturbance using coherent laser is presented. A model to solve the vector velocity of the wind field disturbance is established in this paper. Based on the radial velocity simulation of coherent laser echo signal, a reliable and effective radial velocity data is provided for inversing the vector velocity of the wind field disturbance. Actually, the radial wind velocity appears relatively large fluctuations due to the distribution inhomogeneity of aerosol particles and sensor noise in actual measurement. Therefore, the purpose of adding random noise into the above-mentioned inversion of the radial wind velocity is to simulate the measured radial wind velocity data. In the case of noise interference, the damping least square algorithm is proposed to solve the numerical optimal vector velocity of the wind field disturbance to verify the solving model. In addition, the vector velocity of the wind field disturbance is compared and analyzed under different scanning azimuth interval. Through the simulation results, it shows that the mean square error(MSE) of inversion result is smaller with the decrease of scanning azimuth interval. When the scanning azimuth interval is less than 60°, the mean squared error of the vector velocity of the wind field disturbance is less than 1.14m/s, horizontal direction disturbance quantity is less than 4°, which lays a good theoretical basis for the follow-up field tests.
Beam-forming oriented shape estimation of optical fiber sensor array
Cong Niu, Shuqing Ma, Shuidong Xiong, et al.
In the applications of optical fiber sensor array, many aspects of signal processing are affected by the error of array shape. For example, beam-forming and array shape are closely related. To reduce the effects of shape deformation, an array shape estimation method based on polynomial curve fitting algorithm is proposed in this paper. In the simulation, the heading sensors are placed in the fiber sensor array to obtain the angle information on certain points of the array. With polynomial curve fitted, the estimated function of angle and array length is built. According to the geometry relationship, the X- and Y-axis data of all the points we need on the array are calculated. At last, we compare the results with real array shape in the model, and demonstrate the efficiency of the method. In addition, beam forming simulation is used to check the method. Beam-forming performance of the fiber sensor array system is improved.
Measurements and analysis of solar direct irradiance-meter on Dunhuang radiometric calibration sites
En-chao Liu, Xin Li, Yan-na Zhang, et al.
In order to realize the quantitative application of satellite remote sensing data and adapt to the demand of field calibration of hyper-spectral remote sensors, the solar direct spectral irradiance-meter was developed. According to the sampling principle of spectral irradiance, the irradiance-meter was designed with some technical improvements, the radiometric calibration based on system-level detector were adopted. Irradiance-meter took part in field calibration experiment on Dunhuang radiometric calibration sites and the correct data results were collected. The measurement results of spectral irradiance were consistent with simulated ground irradiance by MODTRAN model. The relative deviation of atmospheric optical depth(AOD) compared with solar radiometer CE318 was less than 4.84%. The whole day results of the irradiance observations and atmospheric transmission in the data applications were collected, the local atmosphere mode and the change of environment were reflected accurately, the input information of the atmospheric parameter were provided for the study of atmospheric properties and field calibration of remote sensors.
Determining the nonlinear refractive index of fused quartz by femtosecond laser Z-scan technology
Lin Zhang, Huan Ren, Hua Ma, et al.
Z-scan technology is an experimental technique for determining the nonlinear refractive index based on the principle of transformation of phase distortion to amplitude distortion when a laser beam propagates through a nonlinear material. For most of the Z-scan system based on the nanosecond or picosecond laser, the accumulation of thermal effects becomes a big problem in nonlinear refractive index measurement especially for the nonlinear materials such as fused quartz and neodymium glass which have a weak nonlinear refractive effect. To overcome this problem, a system for determining the nonlinear refractive index of optical materials based on the femtosecond laser Z-scan technology is presented. Using this system, the nonlinear refractive index of the fused quartz is investigated.
Design of adjustable laser beam high-resolution particle size measuring lens
Zhi-jie Cao, Ming Li, Shu-wei Yang, et al.
On the basis of research on the theory of the Fourier transform lens, according to the observation and test requirements of a fine particle and the geometrical optics aberration theory, a particle size measuring lens of adjustable high resolution laser beam that worked for wavelength of 660 nm is designed, the laser beam can be controlled through the aperture adjusting device of the lens, and can high definition imaging for the semiconductor fiber laser that core diameter is 4.5μm, numerical aperture N.A is 0.13, the output wavelength is 660nm. In the case of object distance for the next 129.5mm, the spot diameter approximately equal to the theoretical amplification value, the main image spot is clear and no flare.
Research on effect of reconstructed image quality in laser reflective tomography imaging
As a novel imaging method, laser reflective tomography imaging can be used for long-range, high-resolution target imaging, with advantages that its spatial resolution is unrelated with the imaging distance, but related with laser pulse-width, bandwidth of detectors and noise. And it can also be easily realized in technology. The principle of range resolved laser reflective tomography imaging was firstly introduced in this paper. The experiment system of laser reflective tomography imaging was established and the projection data acquired by the experiment system was then analyzed and discussed. In the view of the quality of reconstructed image which used filtered back projection algorithm, the influences on reconstructed image quality that those factors such as filter type and projection data cause were compared, and the most critical factor that effect constructed image quality was found out. Experiment results showed that projection data quality is the key factor to reconstructed image quality in laser reflective tomography, Projection data reconstruction which means extracting target range-resolved data from laser echo was useful to improve reconstructed image quality.
Measurement of excited layer thickness in highly photo-excited GaAs
Lingliang Liang, Jinshou Tian, Tao Wang, et al.
Highly photo-excited layer thickness in GaAs is measured using a pump probe arrangement. A normally incident pump illumination spatially modulated by a mask will induce a corresponding refractive index change distribution in the depth direction due to edge scattering and attenuation absorption effect, which can deflect the probe beam passing through this excited region. Maximum deflection of the probe beam will be limited by the thickness of excited layer, and thus can also be employed to measure the thickness of the photo-excited layer of the material. Theoretical calculation confirms the experimental results. This method can find its application in measurements of photo-excited layer thickness of many kinds of materials and be significant to study the characteristics of materials in laser machining, grating and waveguide fabricating.
Development and application of an automated precision solar radiometer
Gang-gang Qiu, Xin Li, Quan Zhang, et al.
Automated filed vicarious calibration is becoming a growing trend for satellite remote sensor, which require a solar radiometer have to automatic measure reliable data for a long time whatever the weather conditions and transfer measurement data to the user office. An automated precision solar radiometer has been developed. It is used in measuring the solar spectral irradiance received at the Earth surface. The instrument consists of 8 parallel separate silicon-photodiode-based channels with narrow band-pass filters from the visible to near-IR regions. Each channel has a 2.0° full-angle Filed of View (FOV). The detectors and filters are temperature stabilized using a Thermal Energy Converter at 30±0.2°. The instrument is pointed toward the sun via an auto-tracking system that actively tracks the sun within a ±0.1°. It collects data automatically and communicates with user terminal through BDS (China’s BeiDou Navigation Satellite System) while records data as a redundant in internal memory, including working state and error. The solar radiometer is automated in the sense that it requires no supervision throughout the whole process of working. It calculates start-time and stop-time every day matched with the time of sunrise and sunset, and stop working once the precipitation. Calibrated via Langley curves and simultaneous observed with CE318, the different of Aerosol Optical Depth (AOD) is within 5%. The solar radiometer had run in all kinds of harsh weather condition in Gobi in Dunhuang and obtain the AODs nearly eight months continuously. This paper presents instrument design analysis, atmospheric optical depth retrievals as well as the experiment result.
Application of chromatic confocal displacement sensor in measurement of tip clearance
Chao Bi, Di Li, Jianguo Fang, et al.
In the field of aeronautics, the tip clearance of rotor exerts a crucial influence on the performance of the aero engine. As defined as the radial distance between the top of the blade and the inner wall of the casing, the tip clearance of too large or small size will adversely affect the normal running of the engine. In order to realize accurate measurement of the tip clearance in a simple way, a non-contact measuring method by the chromatic confocal displacement sensor is proposed in the paper. The sensor possesses the advantages such as small volume, good signal-to-noise ratio, high accuracy and response frequency etc., which make it be widely used in engineering and industry. For testing the performance and potential application of the sensor, a simulation testing platform is established. In the platform, a simulation blisk is installed on the air bearing spindle and a chromatic confocal displacement sensor is fixed on the platform to measure the displacement variation of the blade tip, which can be used to characterize the variation of the tip clearance. In the simulation experiments, both of single and continuous measurement of the tip clearance of the 36 blades on the blisk is executed. As the results of experiments show, the chromatic confocal displacement sensor can meet the requirements of measuring task, in which both of high measuring efficiency and accuracy could be achieved. Therefore, the measuring method proposed in the paper can be utilized in the actual assembling sites of the aero engine.
A zero-crossing point locking system in the time-of-flight measurement of femtosecond pulsed laser
The background and principle of zero-crossing point locking technology are introduced in this paper. An experimental locking system is designed to realize fast locking of zero-crossing point, and the results of locking is studied by analyzing zero-crossing point locking signal. In the distance measurement of femtosecond pulsed laser, a crystal produces the balanced cross-correlation (BCC) signal, which signifies the time offset of the target pulses with respect to the reference pulses. By continuously pulling this signal to zero-crossing point, the locking system provides a closed loop control process, which ensures the stability of the zero-crossing point and the precision of measurement. This locking system is mainly made up by five sections. As a core section of system, P-I circuit can optimize the locking state by changing parameters. A frequency counter referenced to the rubidium atomic clock is used to measure the pulse repetition rate with a stability of 10-12 in the sampling rate of 10s in 24 hours, which is helpful to analyze the measurement precision. In the experiment, the result of zero-crossing point lock can reach to 15mV, in other words, the range of amplitude variation can be reduced to less than 15mV after locking. With the repetition rate data evaluated, the jitter of the pulse repetition rate is within 25Hz in the sampling time of 15s after locking the zero-crossing point. It is proved that the locking system designed has a high practical value in the distance and vibration measurement of femtosecond pulsed laser.
Development of high precision digital driver of acoustic-optical frequency shifter for ROG
Rong Zhang, Mei Kong, Yameng Xu
We develop a high precision digital driver of the acoustic-optical frequency shifter (AOFS) based on the parallel direct digital synthesizer (DDS) technology. We use an atomic clock as the phase-locked loop (PLL) reference clock, and the PLL is realized by a dual digital phase-locked loop. A DDS sampling clock up to 320 MHz with a frequency stability as low as 10-12 Hz is obtained. By constructing the RF signal measurement system, it is measured that the frequency output range of the AOFS-driver is 52-58 MHz, the center frequency of the band-pass filter is 55 MHz, the ripple in the band is less than 1 dB@3MHz, the single channel output power is up to 0.3 W, the frequency stability is 1 ppb (1 hour duration), and the frequency-shift precision is 0.1 Hz. The obtained frequency stability has two orders of improvement compared to that of the analog AOFS-drivers. For the designed binary frequency shift keying (2-FSK) and binary phase shift keying (2-PSK) modulation system, the demodulating frequency of the input TTL synchronous level signal is up to 10 kHz. The designed digital-bus coding/decoding system is compatible with many conventional digital bus protocols. It can interface with the ROG signal detecting software through the integrated drive electronics (IDE) and exchange data with the two DDS frequency-shift channels through the signal detecting software.
Experimental investigation on aero-optical aberration of shock wave/boundary layer interactions
Haolin Ding, Shihe Yi, Jia Fu, et al.
After streaming through the flow field which including the expansion, shock wave, boundary, etc., the optical wave would be distorted by fluctuations in the density field. Interactions between laminar/turbulent boundary layer and shock wave contain large number complex flow structures, which offer a condition for studying the influences that different flow structures of the complex flow field have on the aero-optical aberrations. Interactions between laminar/turbulent boundary layer and shock wave are investigated in a Mach 3.0 supersonic wind tunnel, based on nanoparticle-tracer planar laser scattering (NPLS) system. Boundary layer separation/attachment, induced suppression waves, induced shock wave, expansion fan and boundary layer are presented by NPLS images. Its spatial resolution is 44.15 μm/pixel. Time resolution is 6ns. Based on the NPLS images, the density fields with high spatial-temporal resolution are obtained by the flow image calibration, and then the optical path difference (OPD) fluctuations of the original 532nm planar wavefront are calculated using Ray-tracing theory. According to the different flow structures in the flow field, four parts are selected, (1) Y=692~600pixel; (2) Y=600~400pixel; (3) Y=400~268pixel; (4) Y=268~0pixel. The aerooptical effects of different flow structures are quantitatively analyzed, the results indicate that: the compressive waves such as incident shock wave, induced shock wave, etc. rise the density, and then uplift the OPD curve, but this kind of shock are fixed in space position and intensity, the aero-optics induced by it can be regarded as constant; The induced shock waves are induced by the coherent structure of large size vortex in the interaction between turbulent boundary layer, its unsteady characteristic decides the induced waves unsteady characteristic; The space position and intensity of the induced shock wave are fixed in the interaction between turbulent boundary layer; The boundary layer aero-optics are induced by the coherent structure of large size vortex, which result in the fluctuation of OPD.
Research of spectacle frame measurement system based on structured light method
Automatic eyeglass lens edging system is now widely used to automatically cut and polish the uncut lens based on the spectacle frame shape data which is obtained from the spectacle frame measuring machine installed on the system. The conventional approach to acquire the frame shape data works in the contact scanning mode with a probe tracing around the groove contour of the spectacle frame which requires a sophisticated mechanical and numerical control system. In this paper, a novel non-contact optical measuring method based on structured light to measure the three dimensional (3D) data of the spectacle frame is proposed. First we focus on the processing approach solving the problem of deterioration of the structured light stripes caused by intense specular reflection on the frame surface. The techniques of bright-dark bi-level fringe projecting, multiple exposuring and high dynamic range imaging are introduced to obtain a high-quality image of structured light stripes. Then, the Gamma transform and median filtering are applied to enhance image contrast. In order to get rid of background noise from the image and extract the region of interest (ROI), an auxiliary lighting system of special design is utilized to help effectively distinguish between the object and the background. In addition, a morphological method with specific morphological structure-elements is adopted to remove noise between stripes and boundary of the spectacle frame. By further fringe center extraction and depth information acquisition through the method of look-up table, the 3D shape of the spectacle frame is recovered.
A new optical flat surface measurement method based on machine vision and deflectometry
Kewei E., Dahai Li, Lijie Yang, et al.
Phase Measuring Deflectometry(PMD) is a non-contact, high dynamic-range and full-field metrology which becomes a serious competitor to interferometry. However, the accuracy of deflectometry metrology is strongly influenced by the level of the calibrations. Our paper presents a calibration-based PMD method to test optical flat surface with a high accuracy. In our method, a pin-hole camera was set next to the LCD screen which is used to project sinusoidal fringes to the test flat. And the test flat was placed parallel to the direction of the LCD screen, which makes the geometry calibration process are simplified. The photogrammetric methods used in computer vision science was used to calibrate the pin-hole camera by using a checker pattern shown on another LCD display at six different orientations, the intrinsic parameters can be obtained by processing the obtained image of checker patterns. Further, by making the last orientation of checker pattern is aligned at the same position as the test optical flat, the algorithms used in this paper can obtain the mapping relationship between the CCD pixels and the subaperture coordinates on the test optical flat. We test a optical flat with a size of 50mm in diameter using our setup and algorithm. Our experimental results of optical flat figure from low to high order aberrations show a good agreement with that from the Fizeau interferometer.
Application of double laser interferometer in the measurement of translational stages' roll characteristics
Tao Jin, Lu Shen, Youlong Ke, et al.
In order to achieve rapid measurement of larger travel translation stages’ roll-angle error in industry and to study the roll characteristics, this paper designs a small roll-angle measurement system based on laser heterodyne interferometry technology, test and researched on the roll characteristics of ball screw linear translation stage to fill the blank of the market. The results show that: during the operation of the ball screw linear translation stage, the workbench’s roll angle changes complexly, its value is not only changing with different positions, but also shows different levels of volatility, what’s more, the volatility varies with the workbench’s work speed . Because of the non uniform stiffness of ball screw, at the end of each movement, the elastic potential energy being stored from the working process should release slowly, and the workbench will cost a certain time to roll fluctuate before it achieves a stable tumbling again.
Method for the fabrication error calibration of the CGH used in the cylindrical interferometry system
This paper presents a method of absolutely calibrating the fabrication error of the CGH in the cylindrical interferometry system for the measurement of cylindricity error. First, a simulated experimental system is set up in ZEMAX. On one hand, the simulated experimental system has demonstrated the feasibility of the method we proposed. On the other hand, by changing the different positions of the mirror in the simulated experimental system, a misalignment aberration map, consisting of the different interferograms in different positions, is acquired. And it can be acted as a reference for the experimental adjustment in real system. Second, the mathematical polynomial, which describes the relationship between the misalignment aberrations and the possible misalignment errors, is discussed.
Research of the chemiluminescence detection apparatus for nutrients
Xiaoyi Xu, Yu Wang, Xuxiang Ni, et al.
The multifunctional nutrition analyzer, which integrates four detection functions, can make fast, accurate, quantitative analysis for a variety of nutrients. In this article we focus on researching the luminescence detection system. Compared with other means, luminescence detection needs no excitation light, and the detection sensitivity is improved due to the reduction of the background light. The apparatus consists of an displacement platform, a microporous plate, a combination of an aspheric lens and a plano-convex lens, an optical fiber and a photon counter connected with a computer. A theoretical light intensity formula is established as a reference and a comparison of the experimental data. In the experiment we applies ATP detection reagent as the experimental reagent, whose magnitudes of concentration are from 10-6 mol/L to 10-12 mol/L. The sensitivity of the apparatus could reach a magnitude of concentration of 0.1nmol/L, and it is estimated to be further improved by at least two magnitudes in theory with the system and the reagent optimized.
Conoscopic polarized interference applied in measuring uniaxial axis direction of electro-optic crystal
Yong Liu, Hongzhen Jiang, Lin Zhang, et al.
The crystal can be used to be electro-optic switch because of its electro-optic modulation. Generally the uniaxial axis of electro-optic crystal is perpendicular to the light injection surface. Due to the manufacturing precision, the uniaxial axis direction has a little angle with the normal of the light injection surface, which affects the electro-optic modulation ability. In conoscopic polarized inference, due to birefraction the ordinary ray and extraordinary ray from crystal interferes after the polarizer. The interference pattern of crystal component is circle fringes with dark cross. The center of interference pattern has relation to the uniaxial axis direction. Using digital camera to capture the pattern and the center position of interferogram can be determinate by image processing program. In repeatability experiments the rms of center position is around 1 pixel. To measure the uniaxial axis direction, the normal direction of the crystal component should also be accurately determinate. Michelson interference method is introduced to determinate the normal direction. If rotate the crystal component around the normal direction in conoscopic polarized interference, the track of interferogram center is a circle theoretically. The circle center is related to the normal direction of crystal component, and the radii is related to the angle uniaxial axis, which can be determinate by least square fitting method. Experiment result shows that the measuring precision can achieves several tens of microradians.
Study on application of color filters in vision system of hot forgings
Chao Bi, Jianguo Fang, Di Li, et al.
In order to improve the quality and efficiency of forging process, it needs to execute on-line dimensional measurement of the forgings. In the paper, a laboratory color vision measuring system is set up and the combination of digital and physical filtering is adopted to improve the image quality based on the radiation characteristics of high-temperature forgings. The digital filtering technology is a kind of image processing methods, in which the R component of the forging image is removed. While, the physical filtering technology is achieved by optical filters installed in front of the CCD, in which strong self-emitted radiation from the hot parts can be filtered out. In order to evaluate the image quality, the image contrast is applied, which is generally defined as the difference value between average gray scale of object region and that of background region. In the experiments, image contrast derived with filters at different sample points set from 800°C to 1200°C is compared to determine the optimal scheme of filters to be selected. Results of experiments indicate that the application effect of filters is dissimilar when the forging is in different temperature ranges. Through comparison, the optimal selection scheme of filters is determined to derive high quality image of forgings at different temperatures, which lays a solid foundation for the subsequent image processing.
Influence of surface characteristics on point laser interferometer for aspheric measurement
A point laser interferometer for measuring aspheric optics is developed in this paper. The proposed laser interferometer will be used as a optical probe in optical coordinate measuring machines. The point optical probe is based on homodyne interferometry with frequency stabilized He-Ne laser to provide traceable measurements. The influences of various aspheric surface factors on the performance of point optical probe are analyzed, such as roughness, reflectivity, material, slope angle etc. A compensation method is applied in the signal processing system to reduce the influences. Experimental results show that the measurement resolution is at the nanometer level under various conditions.
Noninvasive blood pressure measurement scheme based on optical fiber sensor
Xianxuan Liu, Xueguang Yuan, Yangan Zhang
Optical fiber sensing has many advantages, such as volume small, light quality, low loss, strong in anti-jamming. Since the invention of the optical fiber sensing technology in 1977, optical fiber sensing technology has been applied in the military, national defense, aerospace, industrial, medical and other fields in recent years, and made a great contribution to parameter measurement in the environment under the limited condition .With the rapid development of computer, network system, the intelligent optical fiber sensing technology, the sensor technology, the combination of computer and communication technology , the detection, diagnosis and analysis can be automatically and efficiently completed. In this work, we proposed a noninvasive blood pressure detection and analysis scheme which uses optical fiber sensor. Optical fiber sensing system mainly includes the light source, optical fiber, optical detector, optical modulator, the signal processing module and so on. wavelength optical signals were led into the optical fiber sensor and the signals reflected by the human body surface were detected. By comparing actual testing data with the data got by traditional way to measure the blood pressure we can establish models for predicting the blood pressure and achieve noninvasive blood pressure measurement by using spectrum analysis technology. Blood pressure measurement method based on optical fiber sensing system is faster and more convenient than traditional way, and it can get accurate analysis results in a shorter period of time than before, so it can efficiently reduce the time cost and manpower cost.
The research on spindle integrated measurement method of cutting force based on fiber Bragg grating
Mingyao Liu, Gong Chen, Zhijian Zhang, et al.
The accurate and effective measurement of cutting force is of great significance to tool condition monitoring. Therefore, various methods of cutting force measurement have been proposed by different researchers. This paper studies the spindle integrated measurement method of cutting force based on Fiber Bragg Grating (FBG) sensing technology, proposes the symmetrical structure which is composed of four identical Γ beam base on the FBG strain detection principle and the force analysis of Γ beam, sets up the theoretical model of spindle integrated cutting force measurement method and determines the paste location of FBG through the analysis of cutting force transfer pattern. In order to verify the accuracy of theoretical model, the cutting force measurement experiment platform is constructed. Ultimately, the feasibility and reliability of this method is verified by experiment.
A system for diagnosis of wheat leaf diseases based on Android smartphone
Xinhua Xie, Xiangqian Zhang, Bing He, et al.
Owing to the shortages of inconvenience, expensive and high professional requirements etc. for conventional recognition devices of wheat leaf diseases, it does not satisfy the requirements of uploading and releasing timely investigation data in the large-scale field, which may influence the effectiveness of prevention and control for wheat diseases. In this study, a fast, accurate, and robust diagnose system of wheat leaf diseases based on android smartphone was developed, which comprises of two parts—the client and the server. The functions of the client include image acquisition, GPS positioning, corresponding, and knowledge base of disease prevention and control. The server includes image processing, feature extraction, and selection, and classifier establishing. The recognition process of the system goes as follow: when disease images were collected in fields and sent to the server by android smartphone, and then image processing of disease spots was carried out by the server. Eighteen larger weight features were selected by algorithm relief-F and as the input of Relevance Vector Machine (RVM), and the automatic identification of wheat stripe rust and powdery mildew was realized. The experimental results showed that the average recognition rate and predicted speed of RVM model were 5.56% and 7.41 times higher than that of Support Vector Machine (SVM). And application discovered that it needs about 1 minute to get the identification result. Therefore, it can be concluded that the system could be used to recognize wheat diseases and real-time investigate in fields.
A new type of rapid and simple coal and other bulk commodities inventory system based on two-dimensional laser scanner
Qianqian Liang, Wenhai Xu, Qisheng Ma, et al.
The acceleration of large coal base construction needs the modern management technology of heap storage as a guarantee. And the inventory of coal and other bulk commodities is an important aspect in the modern management technology of heap storage. Therefore, a rapid, accurate and simple method to measure the volume and quality of coal heaps for scientific management, economic benefit evaluation and storage evaluation of heap storage is very important which has a significant application value. In this paper, we introduce the structural features, working principle and application status of a new type portable heap bulk inventory system. Actual measurements have been carried out in the coal base located in Huanghua port, Tianjin and Qinhuangdao. The measurement results indicate that the system can measure the volume of bulk commodities efficiently, quickly and accurately, and it has extensive application prospects.
A registration method for 2D blade profile
Bin Zhang, Jianguo Fang, Pengfei Liu
Fast and accurate registration research has important theory significance and engineering application value in improving digital measurement accuracy and efficiency. Aiming at solving registration precision and registration speed problem, the extraction scheme of contour dominant point, correspondence establishment method and the objective function of registration are discussed in the paper. Compared with other extraction ones, the scheme can extract typical characters of the blade contour effectively. It is essential to sample measuring points which can represent the entire blade with sufficient confidence and accuracy. Unlike the registration method that only minimizes the one-way distance between the data points and the initial fitted curves, the weighted mutual (two-way) distances between the template profile curves and the data points as the objective function is considered in the paper. The registration algorithm based on iterative closest point algorithm is introduced in details. Using experimental method, the validation of proposed model registration algorithm is verified. Two experimental examples were used to demonstrate registration precision and effectiveness.
Study on the consistency and repeatability of FBG packaging technology
The main research is thermal strain sensing characteristics of epoxy resin in fiber Bragg grating (FBG) packaging process. The results of experiment showed that modified epoxy acrylate resin which is often used to package FBG, occurred glass transition at about 65°C, of which the thermal strain sensing sensitivity decreased. Meanwhile, this study showed that FBG is packaged by the modified epoxy acrylate resin after heat treatment has the effect on strain measurement. The experiment indicated that strain measuring consistency and repeatability of FBG has been significantly improved after heat treatment at high temperature 120°C. Finally, a FBG packaging technology about curable epoxy resin curing at room temperature is proposed, and it can improved strain and temperature measuring consistency and repeatability.
Theoretical analyses of non-diffracting beams interference in a long distance
The intensity distribution of diffraction field of two non-diffracting beams which interfere in a long distance is derived. Non-diffracting beam is generated by an axicon, which is then split into two coherent beams by a beam splitting prism, one of the two beams is regarded as reference beam, which meet the other one through reflector and another beam splitting prism after a long distance. The distribution of interference field is the coherent superposition of each diffraction field. Results show that the locus of interference fringes can be generally assumed hyperbola, the shape of which is affected by interference instance. When the two beams remain parallel, the diffraction pattern is analyzed to be hyperbolic moire fringe,in a case where there is an oblique angle between two beams, the trend of hyperbolic moire fringe change with the interference fringe trend without axicon. Experimental results are compared with theoretical analysis results. Good agreements between them is obtained.
Acoustic emission detection based on distributed feedback fiber laser
Tan Yang, Ying Song, Wen-tao Zhang, et al.
Compared with Fiber Bragg grating (FBG), Distributed Feedback fiber laser (DFB-FL) sensors has the advantages of ultra-narrow line-width, high output power, and low noise level, which will result in a better performance in ultra-slight acoustic emission (AE) detection. In this paper, we demonstrate a DFB fiber laser acoustic sensor. The intensity response of DFB-FL to external acoustic waves has been investigated. The frequency response of the DFB fiber laser based AE sensor is measured in aluminum plate. The experiment results show that the intensity modulated DFB fiber laser acoustic sensor can accurately record the continuous acoustic emission signal and the pencil lead-broken acoustic emission waves.
The system of high accuracy UV spectral radiation system
Guan-yu Lin, Lei Yu, Dian Xu, et al.
UV spectral radiation detecting and visible observation telescope is designed by the coaxial optical. In order to decrease due to the incident light polarization effect, and improve the detection precision, polarizer need to be used in the light path. Four pieces of quartz of high Precision UV radiation depolarizer retarder stack together is placed in front of Seya namioka dispersion unit. The coherent detection principle of modulation of light signal and the reference signal multiplied processing, increase the phase sensitive detector can be adjustment function, ensure the UV spectral radiation detection stability. A lock-in amplifier is used in the electrical system to advance the accuracy of measurement. To ensure the precision measurement detected, the phase-sensitive detector function can be adjustable. the output value is not more than 10mV before each measurement, so it can be ensured that the stability of the measured radiation spectrum is less than 1 percent.
3D indoor modeling using a hand-held embedded system with multiple laser range scanners
Shaoxing Hu, Duhu Wang, Shike Xu
Accurate three-dimensional perception is a key technology for many engineering applications, including mobile mapping, obstacle detection and virtual reality. In this article, we present a hand-held embedded system designed for constructing 3D representation of structured indoor environments. Different from traditional vehicle-borne mobile mapping methods, the system presented here is capable of efficiently acquiring 3D data while an operator carrying the device traverses through the site. It consists of a simultaneous localization and mapping(SLAM) module, a 3D attitude estimate module and a point cloud processing module. The SLAM is based on a scan matching approach using a modern LIDAR system, and the 3D attitude estimate is generated by a navigation filter using inertial sensors. The hardware comprises three 2D time-flight laser range finders and an inertial measurement unit(IMU). All the sensors are rigidly mounted on a body frame. The algorithms are developed on the frame of robot operating system(ROS). The 3D model is constructed using the point cloud library(PCL). Multiple datasets have shown robust performance of the presented system in indoor scenarios.
A standard model eye with micro scale multilayer structure for ophthalmic optical coherence tomography equipment
Zhenggang Cao, Zengqian Ding, Zhixiong Hu, et al.
Optical coherence tomography (OCT) has been widely applied in diagnosis of eye diseases during the last 20 years. Differing from traditional two-dimension imaging technologies, OCT could also provide cross-sectional information of target tissues simultaneously and precisely. As well known, axial resolution is one of the most critical parameters impacting the OCT image quality, which determines whether an accurate diagnosis could be obtained. Therefore, it is important to evaluate the axial resolution of an OCT equipment. Phantoms always play an important role in the standardization and validation process. Here, a standard model eye with micro-scale multilayer structure was custom designed and manufactured. Mimicking a real human eye, analyzing the physical characteristic of layer structures of retina and cornea in-depth, appropriate materials were selected by testing the scattering coefficient of PDMS phantoms with difference concentration of TiO2 or BaSO4 particles. An artificial retina and cornea with multilayer-films which have a thickness of 10 to 60 micrometers for each layer were fabricated using spin coating technology. Considering key parameters of the standard model eye need to be traceable as well as accurate, the optical refractive index and layer structure thicknesses of phantoms were verified by utilizing Thickness Monitoring System. Consequently, a standard OCT model eye was obtained after the retinal or corneal phantom was embedded into a water-filled model eye which has been fabricated by 3D printing technology to simulate ocular dispersion and emmetropic refraction. The eye model was manufactured with a transparent resin to simulate realistic ophthalmic testing environment, and most key optical elements including cornea, lens and vitreous body were realized. By investigating with a research and a clinical OCT system respectively, the OCT model eye was demonstrated with similar physical properties as natural eye, and the multilayer film measurement provided an effective method to rapidly evaluate the axial resolution of ophthalmic OCT devices.
Research on calibration of lux meter based on integrating sphere source
Biyong Huang, Lei Lai, Ming Xia, et al.
In this paper, a new system has been introduced for the calibration of lux meter. This apparatus is designed to use comparison method in high illumination based on integrating sphere source. Experiment has been performed in this apparatus. Meanwhile, the results are compared to that of the superposition method.
The study on measurement methods of phase modulation characteristics for universal liquid crystal spatial light modulator
Yun-long Wu, Jin-song Nie, Li Shao, et al.
The universal liquid crystal spatial light modulator (LC-SLM) was widely used in many aspects of optical study. The working principles and application of LC-SLM were introduced briefly. The traditional Twyman-Green interference method which was used to measure the phase modulation characteristics of universal liquid spatial light modulator had some obvious disadvantages in the practical use, such as high environmental requirement and difficult interference fringes acquisition. The disadvantages of traditional Twyman-Green interference method gained the difficulty of carrying out corresponding optical measurement experiments. To avoid this, the traditional Twyman-Green interference method was improved in the paper. The experimental light path was designed anew. Distinct and stable interference fringes could be acquired by controlling the optical path difference (OPD) dynamically. To verify the validity of the newly proposed measurement method, the phase modulation characteristics of P512-1064 LC-SLM produced by Meadowlark Company were measured by utilizing the improved Twyman-Green interference method at the wavelength of 632.8 nm which was beyond the working wavelengths of the LC-SLM. A series of gray images covering the gray degree from 1 to 256 which were generated by computer were used in the experiment. An extra lens was added in front of a reflector in the optical path to control the OPD dynamically. 256 interference images were acquired after loading the gray image into the LC-SLM in order. After that, the acquired interference images should be pre-processed by several digital image processing methods for easier measurement later. Specifically, the method of gray filtering and morphological processing were adopted to make the interference fringes clearer and thinner in the corresponding processing. Then, the phase modulation curve of the LC-SLM was acquired through numerical computation of the cycles of the interference fringes. In general, the phase modulation curve we acquired was not so accurate in the practical use, as the LC-SLM was required to work from zero to 2pi in the linear interval. So, the nonlinear interval among the phase modulation curve should be compensated and corrected. Here, the method of inverse interpolation which was regarded as one of the most common phase correcting methods was utilized. The corrected phase modulation curve was acquired after numerical computation. The results shows that the improved Twyman-Green interference method could realize the dynamic control of the interference fringes. As a result, the method's requirement for external experiment environment was reduced and its feasibility was improved. Also, the Root Mean Squared Error (RMSE) between the calibrated phase modulation curve and the ideal phase modulation curve was reduced.
MEMS fiber-optic Fabry-Perot pressure sensor for high temperature application
G. C. Fang, P. G. Jia, Q. Cao, et al.
We design and demonstrate a fiber-optic Fabry–Perot pressure sensor (FOFPPS) for high-temperature sensing by employing micro-electro-mechanical system (MEMS) technology. The FOFPPS is fabricated by anodically bonding the silicon wafer and the Pyrex glass together and fixing the facet of the optical fiber in parallel with the silicon surface by glass frit and organic adhesive. The silicon wafer can be reduced through dry etching technology to construct the sensitive diaphragm. The length of the cavity changes with the deformation of the diaphragm due to the loaded pressure, which leads to a wavelength shift of the interference spectrum. The pressure can be gauged by measuring the wavelength shift. The pressure experimental results show that the sensor has linear pressure sensitivities ranging from 0 kPa to 600 kPa at temperature range between 20°C to 300°C. The pressure sensitivity at 300°C is approximately 27.63 pm/kPa. The pressure sensitivities gradually decrease with increasing the temperature. The sensor also has a linear thermal drift when temperature changes from 20°C - 300°C.
Fault diagnosis of the rolling bearing with optical fiber Bragg grating vibration sensor
Peng Wei, Zejing Dai, Leilei Zheng, et al.
Fault diagnosis of the rolling bearing means a lot for property and life safety. In this paper the Fiber Bragg Grating (FBG) vibration sensor and resonance demodulation technology are used in the fault diagnosis of the rolling bearing. Traditionally, the vibration signals are measured by the resistance strain gauge, accelerometer, etc. But those traditional electronic sensors are usually influenced by the industry electromagnetic noise. But the FBG vibration sensor is totally different. It has a lot of advantages such as small volume, light weight, easy connection and so on. And the high industry electromagnetic noise means nothing to the FBG sensors. In this paper, we use the FBG vibration and temperature sensors to measure the fast strain and temperature signal of the rolling bearing. In order to extract the fault signals from strong background noise, the resonant demodulation technology is used to analyze and process the vibration signals collected by the FBG sensors. In order to verify the reliability of the FBG vibration sensor and resonance demodulation technology applied in the fault diagnosis of the rolling bearing, several experiments are done. Five FBG vibration sensors are attached on the different parts of the rolling bearing to verify its function and its influence on the fault diagnosis of the rolling bearing. The results of the experiments show that the FBG vibration sensor method could be used in fault diagnosis of the rolling bearing. The repetitive experiments show the reliability of the FBG vibration sensors method.
The micro spectral measurement of micro integrated filters
Xiaofeng Ma, Sheng Zhou, Yuan Cai, et al.
Theory of micro spectral transmittance measurement and its characteristics have been analyzed. Measurement procedures and data processing method have been introduced. Micro spectral transmittance of micro integrated filters has been measured using PerkinElmer Lambda 1050 spectrophotometer with the combination of a Schwarzschild optical system microscope accessory, and the measured quantitative analysis results have been obtained. The incidence focused light spot size is about 20*40 um2. At last, micro spectral transmittance results for micro integrated filters have been compared with the spectral transmittance for large size samples, which are fabricated under the same condition and measured at normal incidence. The focused incidence for micro spectral measurement will cause a wavelength shift towards the shorter and a deformation transmittance curve, but those changes are in agreement with their theoretical simulations.
Experimental comparative study of doublet and triplet impinging atomization of gelled fuel based on PIV
Jian-lu Yang, Ning Li, Chun-sheng Weng
Gelled propellant is promising for future aerospace application because of its combination of the advantages of solid propellants and liquid propellants. An effort was made to reveal the atomization properties of gelled fuel by particle image velocimetry (PIV) system. The gelled fuel which was formed by gasoline and Nano-silica was atomized using a like-doublet impingement injector and an axisymmetric like-triplet impingement injector. The orifice diameter and length of the nozzle used in this work were of 0.8mm, 4.8mm, respectively. In the impinging spray process, the impingement angles were set at 90° and 120°, and the injection pressures were of 0.50MPa and 1.00MPa. The distance from the exit of the orifice to the impingement point was fixed at 9.6mm. In this study, high-speed visualization and temporal resolution particle image velocimetry techniques were employed to investigate the impingement atomization characteristics. The experimental investigation demonstrated that a long narrow high speed droplets belt formed around the axis of symmetry in the like-doublet impinging atomization area. However, there was no obvious high-speed belt with impingement angle 2θ = 90° and two high-speed belts appeared with impingement angle 2θ = 120° in the like-doublet impingement spray field. The high droplet velocity zone of the like-doublet impingement atomization symmetrically distributed around the central axis, and that of the like-triplet impingement spray deflected to the left of the central axis - opposite of injector. Although the droplets velocity distribution was asymmetry of like-triplet impingement atomization, the injectors were arranged like axisymmetric conical shape, and the cross section of spray area was similar to a circle rather than a narrow rectangle like the like-doublet impingement atomization.
Simulation and experiment of the nonlinear response of the InGaAs p-i-n photodiode under high illumination
Ya-fu Wang, Li Shao, Wei Hu, et al.
The nonlinearity of an In0.53Ga0.47As on InP p-i-n photodiode due to high-energy laser irradiation is simulated using quasi-three-dimensional iterative solutions to the drift-diffusion and Poisson equation in the presence of generation-recombination terms. Some necessary physics models used to simulate the realistic device are discussed, such as the recombination model and mobility model. The calculation results indicate that the peak amplitude of the voltage response to the laser increases sub-linearly and the relative contribution of the tail to the detector response is appreciably enhanced with the intensity of the laser increasing. With the different reverse bias decreasing, the photodiode response saturated voltage reduces, the nonlinear is more serious and the responsivity of the photodiode is decreasing with the same pulse energy. The space-charge-screening effect due to the carriers generated by the high optical injection restraining the internal electrical field is responsible for this nonlinearity. The experiment of the p-i-n photodiodes response to picosecond pulse laser is carried out. By measuring the response voltage and time of the InGaAs p-i-n photodiode, the results are verified the theoretical simulation.
Study on the calibration method of metrological performance of ring laser gyroscope
Dan Qiao, Zi Xue, Yao Huang
Ring Laser Gyroscope (RLG) is a kind of typical inertial device widely used in navigation field. Owing its recent advances, RLG is proposed to be used as angle measuring instrument with highly dynamic performance and loose installation requirement. To prove the reliability of RLG’s angular measuring result, the metrological performance of RLG was analyzed through calibration. A new calibration method was studied to separate RLG’s additional error resource such as bias drift. The special calibrating procedure was designed and the corresponding calibration system was set up. The calibration result shows that the RLG angular measuring system has measuring deviation within ±0.4″ and repeatability within ±0.2″. The study proposes an effective calibration method of RLG’s metrological performance and proves the possibility of RLG’s application in high accuracy in-situ metrology field.
Experimental study of a new injection mode of aluminum dust fuel of pulse detonation engine based on particle image velocity
Wei Wei, Jian-lu Yang, Ning Li, et al.
This paper discussed a new injection mode of aluminum dust fuel on PDE and its measurement of velocity using a high-speed visualization and temporal resolution particle image velocimetry system. Based on particle image velocimetry, we can clear the new method is applicable, and can adjust its parameters to implement best, without operating the pulse detonation engine. Through the analysis of dust velocity distribution images, the most appropriate injection pressure to pulse detonation engine were be determined. It can be seen that a particle image velocimetry system can be very important in the application of experimental study of the pulse detonation engine.
Development on adaptive accelerated system
H. Liu, P. Zhang, H. L. Chen, et al.
Generally adaptive speed system is an important direction in the development of computational imaging. Computational theory of imaging system and its influence on aberration and control, is the basis to develop such a system design, which has application value aspects. The principle approach, modeling, and error analysis are analyzed, and the system configuration based on adaptive is advanced in algorithm analysis.
Evaluation of the photoelectric performance parameters measurement for electron multiplying CCD
Jie Fang, Wenwen Zhang, Jin Gao, et al.
The measurement of the electron multiplying CCD(EMCCD) photoelectric performance parameters plays an important role in the development of the chip and imaging system. Measurement uncertainty is an important index to evaluate the quality of the measurement results. A measurement platform for EMCCD photoelectric performance parameters is set up. An EMCCD camera’s photoelectric performance parameters are measured based on photon transfer technique and the uncertainty of the measurement results is analyzed. Based on the method of GUM, the influences of the integrating sphere light source stability, EMCCD camera electronics system stability, installation posture, stray light in dark environment, camera's digital resolution and measurement sampling on the measurement results are analyzed. Based on the theoretical model of different photoelectric performance parameters, the uncertainty sources are discussed. The combined standard uncertainty is determined by the type A uncertainty and the type B uncertainty. The uncertainty evaluation model is established for the measurement of EMCCD photoelectric performance parameters, including convert gain, readout noise, full well, signal to noise ratio and multiplication gain. The uncertainty of the measurement results is calculated by using the established model. At last, we get the following results: relative standard uncertainty of the convert gain is 0.637% (k = 1), relative standard uncertainty of the readout noise is 0.653% (k = 1), relative standard uncertainty of the full well is 2.384% (k = 1), relative standard uncertainty of the signal to noise ratio is 2.301% (k = 1) and relative standard uncertainty of the multiplication gain is 1.259% (k = 1). The above uncertainty results show that the measurement results of this paper are accurate and reliable.
Real-time O2 measurement in a cement kiln with a TDLAS analyzer
Yanwei Gao, Yujun Zhang, Dong Chen, et al.
Cement kilns are the main source of atmospheric pollutants, and will consume large amounts of fuel. In order to reduce the emissions of gas pollutants and saving fuel, the combustion process inside the furnace is needed to monitor in real time. Oxygen is the main combustion-supporting gas, monitoring the oxygen concentration inside the furnace can be implemented to combustion control and optimize combustion efficiency. We developed a TDLAS analyzer for real-time oxygen concentration measurement to achieve fuel saving and gas pollutant emission reduction. We realized temperature correction algorithm using the relationship between high-temperature oxygen line strength and measurement temperature, improving the measurement accuracy of the oxygen concentration at different temperatures. We tested the analyzer and the test results show that detection limit was 0.1%, analyzer can be achieved accurate measurement of oxygen concentration, the measured oxygen concentration was 5-8%. Results were true and reliable indicated that the oxygen measuring system can be developed to achieve long-term stability operation in high-temperature environments oxygen concentration measurement.
Analysis of nonlinear effects caused by TE waves propagating in two-dimensional Kerr photonic crystals
Jin Pan, Zhixiang Tang, Rong Pan, et al.
As the two main ways to enhance nonlinearity in nano-structured materials, field localization and slow light effects could cooperate to exert influence on nonlinear effect enhancement together. By considering the co-influence of them, we can make use of a field averaging method to calculate the effective nonlinear refractive index coefficient ( n2 ) of Kerr photonic crystals (PhCs). In this paper, we treat the propagation of TE waves in Kerr PhCs in detail as a complementary to TM waves and calculate the effective n2 in the first band. Although TM waves and TE waves may cause different nonlinear effects in two-dimensional Kerr PhCs, it proves that our theoretical calculating method also works well for TE waves.
A 256×256 low-light-level CMOS imaging sensor with digital CDS
In order to achieve high sensitivity for low-light-level CMOS image sensors (CIS), a capacitive transimpedance amplifier (CTIA) pixel circuit with a small integration capacitor is used. As the pixel and the column area are highly constrained, it is difficult to achieve analog correlated double sampling (CDS) to remove the noise for low-light-level CIS. So a digital CDS is adopted, which realizes the subtraction algorithm between the reset signal and pixel signal off-chip. The pixel reset noise and part of the column fixed-pattern noise (FPN) can be greatly reduced. A 256×256 CIS with CTIA array and digital CDS is implemented in the 0.35μm CMOS technology. The chip size is 7.7mm×6.75mm, and the pixel size is 15μm×15μm with a fill factor of 20.6%. The measured pixel noise is 24LSB with digital CDS in RMS value at dark condition, which shows 7.8× reduction compared to the image sensor without digital CDS. Running at 7fps, this low-light-level CIS can capture recognizable images with the illumination down to 0.1lux.
The evaluation of uncertainty about the shape of aperture on measurement of averaged LED intensity
Jian Liu, Hui Liu, Wei-qiang Zhao, et al.
Averaged LED Intensity was defined in CIE 127, in which two measurement conditions were proposed, both required the area of entrance aperture to be 100 mm2. The CIE 127 LED measurement method is widely accepted. Circular entrance aperture is usually used in commercial photometers, but the photosurface of silicon photodetector is square. However, when LEDs with a narrow beam angle are measured their Averaged LED Intensity, the result may vary due to various aperture shapes. In this paper, a mathematical measurement model is built, then the uncertainty of measurement introduced by shape of aperture is rigorously evaluated by comparing the prediction of model and the results obtained from measurement experiments. It is an effective quantitative analysis to the impact of aperture shapes on accurate measurement of Averaged LED Intensity.
Programming implementation of performance testing of low light level ICCD camera based on LabVIEW software
Li Ni, Qiong Ye, Yunsheng Qian
Low light level (LLL) imaging technology major roles in the night and in other low light illumination stage, through a variety of low light level image intensifier and charge-coupled device (CCD), gains image information on the target acquisition, photoelectric conversion and high-performance enhancement, storing and displaying. In order to comprehensively test the parameters such as intensified charge-coupled device (ICCD) signal noise ratio (SNR) and dynamic range, this paper uses Laboratory Virtual Instrument Engineering Platform (LabVIEW) software for programming. Data acquisition is the core of the entire software programming, according to the function; it is divided into three parts: a) initializing acquisition cards; b) data collection and storage of useful data; c) closing the acquisition card. NI PXIe-5122 analog acquisition card and PXIe-1435 digital acquisition card were used to collect pal cameras and camera link cameras’ shooting pictures, developing with analog interface and the digital interface of ICCD test work. After obtaining data, we can then analyze the performance of the camera by calculating the data according to the principle programmed parameters. Experimental testing process, the use of half-moon test target signal to noise ratio, dynamic range parameters and uniformity test target will be normal. Meanwhile, in order to increase the practicality of the program, we also add the database module into the program. LabSQL is a free, multi-database, cross-platform database access LabVIEW Toolkit. Using LabSQL can access almost any type of database, perform a variety of inquiries and record various operations. With just a simple programming, database access can be achieved in LabVIEW.
Analysis of nozzle effect on pulsed detonation engine performance based on laser absorption spectroscopy with Doppler frequency shift
Xiao-long Huang, Ning Li, Chun-sheng Weng, et al.
An optical experiment system of tunable diode laser absorption spectroscopy is designed for valveless gas-liquid PDE to reveal the mechanism of nozzle improved the thrust performance. The velocity of detonation exhaust with non-nozzle, convergent nozzle, divergent nozzle and convergent-divergent nozzle is tested by laser Doppler velocimetry. The results indicate that laser Doppler method can accurately infer the instantaneous flow velocity, especially the velocity platform where contributes more to the engine impulse. The maximum value is 1222.66 m/s, 1128.52 m/s, 1338.64 m/s and 1296.93 m/s, the time of duration which the velocity is greater than 400m/s is 8.51ms, 7.58ms, 5.83ms and 17.62ms of the velocity under the condition of non-nozzle, convergent nozzle, divergent nozzle and convergent-divergent nozzle respectively.
Reflectivity and depth images based on time-correlated single photon counting technique
We presented three-dimensional image including reflectivity and depth image of a target with two traditional optical imaging systems based on time-correlated single photon counting technique (TCSPC), when it was illuminated by a MHz repetition rate pulsed laser source. The first one is bi-static system of which transmitted and received beams path are separated. Another one called mono-static system of which transmit and receive channels are coaxial, so it was also named by transceiver system. Experimental results produced by both systems showed that the mono-static system had more advantages of less noise from ambient light and no limitation about field area of view. While in practical applications, the target was far away leading to there were few photons return which was prejudicial to build 3D images with traditional imaging system. Thus an advanced one named first photon system was presented. This one was also a mono-static system on hardware system structure, but the control system structure was different with traditional transceiver system described in this paper. The difference was that the first return photon per pixel was recorded across system with first photon system, instead of overall return photons per pixel. That’s to say only one detected return photon is needed for per pixel of this system to rebuild 3D images of target with less energy and time.
Research on measurement method of optical transmittance of the artificial fog
Jianghua Hu, Chaochao Jian, Guangzhen Cui, et al.
The attenuation of light was a common result that the light was absorbed and scattered by the artificial fog particles when it transmitted in the artificial fog. The absorbing attenuation process of light transmission in the artificial fog was that the artificial fog converting incident light energy into other forms of internal energy (such as heat energy). The scattering attenuation process of light transmission in the artificial fog was that the artificial fog particles intercepting incident radiation energy to form infrasonic waves and to radiate peripherally so that the incident light energy was reduced on the original direction of transmission. The mechanism of light transmission attenuation in the artificial fog was analyzed. The formation method of the artificial fog was expounded and the measuring principle of the artificial fog transmittance was described. A simple and reliable measurement method of the optical transmittance of the artificial fog in the fog chamber was proposed. The optical transmittance measurement system of the artificial fog was built by using incandescent lamp, power with steady current and voltage, lens, selenium photocell, micro-galvanometer, optical bench, hygrothermograph, humidifier, etc. Under different conditions of humidity, the optical transmittance of the artificial fog was obtained on the basis of measuring the photocurrent before the fog was formed in the fog chamber. The test results show that the measurement system is stable and reliable. During the 43 minutes after the artificial fog was formed, the optical transmittance of the artificial fog was averagely less than 5 percent and the optical transmittance increased gradually with the extension of time. In addition, the optical transmittance of artificial fog didn’t produce obvious change while air humidity increased from 68.7% to 85%. The measurement system can be used to measure transmittance of smoke screen, water mist and other aerosol.
SG-t optimization and processing technology of the points cloud of the railway tank car (container)
Based on 3D laser scanning technology in railway tank car and tank container (the railway tank car (container) for short) application, the point cloud which was incomplete and noise which was found during the scanning process were analyzed. Based on the massive scanning point cloud of railway tank car(container), proposed a fast and effective SG-t point cloud optimization processing method. The SG-t method included sp-H point cloud pre-processing method and Eti-G model reconstruction. The tests showed that the new methods could optimize point cloud which was noise and incomplete in a relatively short time. It could reconstruct model fast and efficient. It could greatly improve the efficiency and precision of scanning. The results which Compared with the results of capacity comparison method showed that measurement uncertainty increased from 4×10-3,k=2 to 3×10-3,k=2.Optimization and processing method of the point cloud of the 3D laser scanning of railway tank car (container) provide a reference to the development of related technologies.
Design of a new type spectacle frames scanner
Xiaodong Chen, Dong Guan, Xiuda Zhang, et al.
The spectacle frames scanner is an important part in the non-modeling lens-edger system, for its function to measure the profile of the spectacle frames and elicit its 3D data for lens-edging. We propose a new spectacle frames scanner based on multi-linear structured light which is a non-contact type. The experiment devices of the proposed system include a portable projector, a 12mm prime lens and an area array CCD camera. The technology of binary stripes and single-camera image collection are used in the new scanner. The original stripes are modulated by the spectacle frames, so we can collect the images and demodulate the 3D data of the spectacle frames based on trigonometry theory. The factors that influence the measurement accuracy of the scanner system are analyzed and the relationship between structure parameters and measurement error of the system has been determined. According to the result of the simulation, we determine the optimal structure parameters of the spectacle frames scanner system. Experiment result for resin frames with high reflectivity is given.
Computed tomography measurement of 3D combustion chemiluminescence using single camera
Kuanliang Wang, Fei Li, Hui Zeng, et al.
Instantaneous measurement of flame spatial structure has been long desired for complicated combustion condition (gas turbine, ramjet et.). Three dimensional computed tomography of chemiluminescence (3D-CTC) is a potential testing technology for its simplicity, low cost, high temporal and spatial resolution. In most former studies, multi-lens and multi-CCD are used to capture projects from different view angles. In order to improve adaptability, only one CCD was utilized to build 3D-CTC system combined with customized fiber-based endoscopes (FBEs). It makes this technique more economic and simple. Validate experiments were made using 10 small CH4 diffusion flame arranging in a ring structure. Based on one instantaneous image, computed tomography can be conducted using Algebraic Reconstruction Technique (ART) algorithm. The reconstructed results, including the flame number, ring shape of the flames, the inner and outer diameter of ring, all well match the physical structure. It indicates that 3D combustion chemiluminescence could be well reconstructed using single camera.
Extrinsic Fabry-Perot interferometric sensor using a polarization-switched phase interrogator
In this paper, a phase variation tracking method for the extrinsic Fabry-Perot interferometric (EFPI) voice sensing system is designed and experimentally demonstrated through a polarization-switched unit based on the combination of polarization-maintaining fiber Bragg grating (PMFBG). The measurements at two operation wavelengths are firstly achieved in one total-optical path, which eliminates the imbalance of optical power from the external disturbances, optical source fluctuation, different detecting response of photoelectric detector and different background noise. Two operation wavelengths reflected from a PMFBG for interference phase tracking are switched via an electro-optic modulator at a high switching speed of 10 kHz. Besides, an ellipse fitting-differential cross multiplication (EF-DCM) algorithm is proposed and illustrated for interrogating the variation of EFPI cavity gap length of the EFPI voice sensor effectively. Preliminary experimental results have proven that the polarization-switched system based on the EF-DCM algorithm could find potential applications in the fields of marine acoustic, medical science measurements, etc.
Study of the performance of image restoration under different wavefront aberrations
Image restoration is an effective way to improve the quality of images degraded by wave-front aberrations. If the wave-front aberration is too large, the performance of the image restoration will not be good. In this paper, the relationship between the performance of image restoration and the degree of wave-front aberrations is studied. A set of different wave-front aberrations is constructed by Zernike polynomials, and the corresponding PSF under white-light illumination is calculated. A set of blurred images is then obtained through convolution methods. Next we recover the images with the regularized Richardson-Lucy algorithm and use the RMS of the original image and the homologous deblurred image to evaluate the quality of restoration. Consequently, we determine the range of wave-front errors in which the recovered images are acceptable.
Method of recognizing the high-speed railway noise barriers based on the distance image
Le Ma, Shuangyun Shao, Qibo Feng, et al.
The damage or lack of the noise barriers is one of the important hidden troubles endangering the safety of high-speed railway. In order to obtain the vibration information of the noise barriers, the online detection systems based on laser vision were proposed. The systems capture images of the laser stripe on the noise barriers and export data files containing distance information between the detection systems on the train and the noise barriers. The vibration status or damage of the noise barriers can be estimated depending on the distance information. In this paper, we focused on the method of separating the area of noise barrier from the background automatically. The test results showed that the proposed method is in good efficiency and accuracy.
Research on measurement method of optical camouflage effect of moving object
Juntang Wang, Weidong Xu, Yang Qu, et al.
Camouflage effectiveness measurement as an important part of the camouflage technology, which testing and measuring the camouflage effect of the target and the performance of the camouflage equipment according to the tactical and technical requirements. The camouflage effectiveness measurement of current optical band is mainly aimed at the static target,which could not objectively reflect the dynamic camouflage effect of the moving target. This paper synthetical used technology of dynamic object detection and camouflage effect detection, the digital camouflage of the moving object as the research object, the adaptive background update algorithm of Surendra was improved, a method of optical camouflage effect detection using Lab-color space in the detection of moving-object was presented. The binary image of moving object is extracted by this measurement technology, in the sequence diagram, the characteristic parameters such as the degree of dispersion, eccentricity, complexity and moment invariants are constructed to construct the feature vector space. The Euclidean distance of moving target which through digital camouflage was calculated, the results show that the average Euclidean distance of 375 frames was 189.45, which indicated that the degree of dispersion, eccentricity, complexity and moment invariants of the digital camouflage graphics has a great difference with the moving target which not spray digital camouflage. The measurement results showed that the camouflage effect was good. Meanwhile with the performance evaluation module, the correlation coefficient of the dynamic target image range 0.1275 from 0.0035, and presented some ups and down. Under the dynamic condition, the adaptability of target and background was reflected. In view of the existing infrared camouflage technology, the next step, we want to carry out the camouflage effect measurement technology of the moving target based on infrared band.
Alignment method of optical registration for multi-channel CCD camera
Jia Xin, Guo Yue
The mapping satellite is use of the multichip CCD assemble technology to meet the precision landscape positioning requirements. The size of a single CCD cannot meet the requirements of modern optical system. High cost and special technology are required for the resolution. In order to apply space camera to the measurement in large field of view and high resolution, the technology of optical assembly with several CCD is discussed. And a reflector based butting system was adopted. To extend the field of view, an optical butting system is proposed. Aiming at the problems of vignette and decline of modulation transfer function caused by butting, a reflector based butting system which has nine mirrors was investigated. This paper introduced the structure design of a long array and the principle of optical butting. The basic idea of this system is to split the optical image into several parts, so that they can be detected by different sensors. The mirror is used in conventional imaging system; divide the optical image into two parts. To eliminate the vignette distortion caused by the optical system and keep high signal to noise ratio, the sensors receiving the two focal image parts are placed with a little overlapping so that they can compensate each other. In order to ensure the key techniques of mirror location accuracy, a new alignment method was proposed about locating conversation components, mainly aimed at enhancing assembly accuracy of linear array CCD.A high quality image can be obtained by butting the two image parts. Its principle, methods of adjusting and testing as well as the structure of focal plane are described. The assembly with nine TDICCDs is finished on the facility which is composed of a long work-distance microscope and a precise X-Y rail, using the method in which the mechanical adjusting is applied. Compared with convention system, this method can satisfy the linearity accuracy and overlapping pixels tolerance of 0.2 detector pixel sizes. And can meet 5um co focal accuracy; the optical assembly has the advantages of simple constitution, low cost and good adaptability, it has practical value.
Design of noise barrier inspection system for high-speed railway
Bingqian Liu, Shuangyun Shao, Qibo Feng, et al.
The damage of noise barriers will highly reduce the transportation safety of the high-speed railway. In this paper, an online inspection system of noise barrier based on laser vision for the safety of high-speed railway is proposed. The inspection system, mainly consisted of a fast camera and a line laser, installed in the first carriage of the high-speed CIT(Composited Inspection Train).A Laser line was projected on the surface of the noise barriers and the images of the light line were received by the camera while the train is running at high speed. The distance between the inspection system and the noise barrier can be obtained based on laser triangulation principle. The results of field tests show that the proposed system can meet the need of high speed and high accuracy to get the contour distortion of the noise barriers.
A defocus-information-free autostereoscopic three-dimensional (3D) digital reconstruction method using direct extraction of disparity information (DEDI)
Da Li, Chifai Cheung, Xing Zhao, et al.
Autostereoscopy based three-dimensional (3D) digital reconstruction has been widely applied in the field of medical science, entertainment, design, industrial manufacture, precision measurement and many other areas. The 3D digital model of the target can be reconstructed based on the series of two-dimensional (2D) information acquired by the autostereoscopic system, which consists multiple lens and can provide information of the target from multiple angles. This paper presents a generalized and precise autostereoscopic three-dimensional (3D) digital reconstruction method based on Direct Extraction of Disparity Information (DEDI) which can be used to any transform autostereoscopic systems and provides accurate 3D reconstruction results through error elimination process based on statistical analysis. The feasibility of DEDI method has been successfully verified through a series of optical 3D digital reconstruction experiments on different autostereoscopic systems which is highly efficient to perform the direct full 3D digital model construction based on tomography-like operation upon every depth plane with the exclusion of the defocused information. With the absolute focused information processed by DEDI method, the 3D digital model of the target can be directly and precisely formed along the axial direction with the depth information.
Wavefront reconstruction algorithm based on interpolation coefficients for radial shearing interferometry
A new wavefront reconstruction algorithm for radial shearing interferometer is proposed. Based on the shearing relationship between the expanded wavefront and the test wavefront, the interpolation coefficient matrix are established by the radial shearing ratio and the number of discrete points of test wavefront. Accordingly, the expanded wavefront can be described by an interpolation coefficient matrix and the test wavefront. Then the test wavefront can be calculated from the phase difference wavefront which comes from any radial shearing interferometer. The numerical simulation proves the correctness of the algorithm. The main error source of this algorithm has been analyzed and the error propagation coefficient has been calculated at last. Above results show that the proposed algorithm is an effective and correct algorithm to reconstruct wavefront for radial shearing interferometer.
Design of spectrally tunable calibration source based on Digital Micromirror Device (DMD)
Wenchao Zhai, Meng Zhang, Fangang Meng, et al.
A kind of novel calibration source with dual output modes, namely, narrow-band and broadband, was designed. The optical system of the source is refractive, in spectrometer-like optical configurations using a prism as the dispersion device. The Digital Micromirror Device (DMD) is used as the spatial light modulator, which locates at the focal plane of the dispersion unit. The dispersive wavelengths are located at the active area of DMD, every column of the DMD corresponds to a different wavelength and the rows of each DMD column correspond to the intensity of that wavelength. With the modulation of the DMD, it can produce narrow-band/monochromatic output like a monochromator by switching the corresponding columns on, and broadband output by switching several different columns on. The source’s operating band spans 450~2250nm, consisting of two independent parts which span 450~1000nm and 1000~2250nm, respectively. The narrow-band bandwidths spans 5~28nm for VIS-NIR and 20~40nm for SWIR subsystems. Several broadband target spectra, including sea water, plants and sun, were simulated by this source through spectral simulation algorithm. The source’s radiometric metrics are suitable to be traced to the absolute cryogenic radiometer (ACR), the most accurate optical power standard at present, which is helpful to improve the calibration accuracy for remote sensors at the beginning. The capability of simulating target spectra will reduce the calibration uncertainties caused by the spectral mismatch between calibration sources and targets viewed by the remote sensors. Based on the considerations above, the source is very appropriate and applicable for remote sensor’s calibration.
Phase distortion of a probe beam transmitting through a transparent medium bulk
A highly feasible full-field phase-measuring methodology has been developed to investigate the phase distortions of a probe beam transmitting through a LiB3O5 (LBO) crystal under different conditions. The results show that wavefront phase exhibits inhomogeneous distribution when the crystal is heated and the phase difference becomes small as time goes by when the heating temperature is kept unchanged. The technique provides an easy and feasible way to accurately measure the phase images of a probe beam transmitting through a crystal. The procedure provided in this report can be also used to study the rapid phase changes that take place in other types of optical materials.
Combining depth and gray images for fast 3D object recognition
Wang Pan, Feng Zhu, Yingming Hao
Reliable and stable visual perception systems are needed for humanoid robotic assistants to perform complex grasping and manipulation tasks. The recognition of the object and its precise 6D pose are required. This paper addresses the challenge of detecting and positioning a textureless known object, by estimating its complete 6D pose in cluttered scenes. A 3D perception system is proposed in this paper, which can robustly recognize CAD models in cluttered scenes for the purpose of grasping with a mobile manipulator. Our approach uses a powerful combination of two different camera technologies, Time-Of-Flight (TOF) and RGB, to segment the scene and extract objects. Combining the depth image and gray image to recognize instances of a 3D object in the world and estimate their 3D poses. The full pose estimation process is based on depth images segmentation and an efficient shape-based matching. At first, the depth image is used to separate the supporting plane of objects from the cluttered background. Thus, cluttered backgrounds are circumvented and the search space is extremely reduced. And a hierarchical model based on the geometry information of a priori CAD model of the object is generated in the offline stage. Then using the hierarchical model we perform a shape-based matching in 2D gray images. Finally, we validate the proposed method in a number of experiments. The results show that utilizing depth and gray images together can reach the demand of a time-critical application and reduce the error rate of object recognition significantly.
Beam hardening correction for interior tomography based on exponential formed model and radon inversion transform
Siyu Chen, Hanming Zhang, Lei Li, et al.
X-ray computed tomography (CT) has been extensively applied in industrial non-destructive testing (NDT). However, in practical applications, the X-ray beam polychromaticity often results in beam hardening problems for image reconstruction. The beam hardening artifacts, which manifested as cupping, streaks and flares, not only debase the image quality, but also disturb the subsequent analyses. Unfortunately, conventional CT scanning requires that the scanned object is completely covered by the field of view (FOV), the state-of-art beam hardening correction methods only consider the ideal scanning configuration, and often suffer problems for interior tomography due to the projection truncation. Aiming at this problem, this paper proposed a beam hardening correction method based on radon inversion transform for interior tomography. Experimental results show that, compared to the conventional correction algorithms, the proposed approach has achieved excellent performance in both beam hardening artifacts reduction and truncation artifacts suppression. Therefore, the presented method has vitally theoretic and practicable meaning in artifacts correction of industrial CT.
Simulation of laser bistatic two-dimensional scattering imaging about lambertian cylinders
Yanjun Gong, Lang Li, Mingjun Wang, et al.
This paper deals with the simulation of laser bi-static scattering imaging about lambertian cylinders. Two-dimensional imaging of a target can reflect the shape of the target and material property on the surface of the target. Two-dimensional imaging has important significance for target recognition. Simulations results of laser bi-static two-dimensional scattering imaging of some cylinders are given. The laser bi-static scattering imaging of cylinder, whose surface material with diffuse lambertian reflectance, is given in this paper. The scattering direction of laser bi-static scattering imaging is arbitrary direction. The scattering direction of backward two-dimensional scattering imaging is at opposite direction of the incident direction of laser. The backward two-dimensional scattering imaging is special case of bi-static two dimensional scattering imaging. The scattering intensity of a micro-element on the target could be obtained based on the laser radar equation. The intensity is related to local angle of incidence, local angle of scattering and the infinitesimal area on the surface of cylinder. According to the incident direction of incident laser and normal of infinitesimal area, the local incidence angle can be calculated. According to the scattering direction and normal of infinitesimal area, the local angle of scattering can be calculated. Through surface integration and the introduction of the rectangular function, we can get the intensity of imaging unit on the imaging surface, and then get mathematical model of bi-static laser two dimensional scattering imaging about lambert cylinder. From the results given, one can see that the simulation results of laser bi-static scattering about lambert cylinder is correct.
Use of the fluorescence of rhodamine B for the pH sensing of a glycine solution
Weiwei Zhang, Kaixing Shi, Jiulin Shi, et al.
The fluorescence of rhodamine B can be strongly affected by its environmental pH value. By directly introducing the dye into various glycine solution, the fluorescence was used to monitor the pH value in the range of 5.9 ~ 6.7. Two newly developed techniques for broadband analysis, the barycenter technique and the self-referenced intensity ratio technique, were employed to retrieve the pH sensing functions. While compared with traditional techniques, e.g. the peak shift monitoring, both the two new techniques presented finer precision. The obtained sensing functions may find their applications in the test of biochemical samples, body tissue fluid, water quality, etc.
Synthetic aperture LADAR at 1550 nm: system demonstration, imaging processing and experimental result
Guangzuo Li, Ran Wang, Peisi Wang, et al.
In this manuscript, we propose and experimentally demonstrate our synthetic aperture LADAR (SAL) system. The system could obtain imageries in a few milliseconds with resolution of 5 cm from a long distance. Fine resolution in the range dimension was obtained by transmitting LADAR signal with large bandwidth. While in the cross-range dimension, the large synthetic aperture diameter provided fine resolution. By employing continuous translational motion of SAL system, a large aperture diameter was obtained through synthetic aperture processing. So the diffraction limit of real aperture diameter was overcome and finer resolution was achieved. Indoor and outdoor experiments were both performed and the corresponding results were showed. Results validated the feasibility of our system and processing algorithm.
The microstructure measurement of surface defects of optical component based on digital image-plane holographic microscopy
Zhu Chen, Hongzhen Jiang, Xu Liu, et al.
In order to measure the three-dimensional microstructure of surface defects on optical component, a novel measuring method based on digital image-plane holographic microscopy (DIPHM) is proposed in this paper. The experimental system has been designed and built to measure the microstructure of optical component’s surface defects. The object light wavefront can be reconstructed by using the algorithm based on the angular spectrum theory, and the technique of phase correction is contributive to eliminate the system error. There is a definite relationship between the object light wavefront and the surface topography, so the 3D microstructure of surface defects can be measured. This measuring technique is helpful to judge the damage degree of the optical component and analysis the influence of the surface defects, and it is of great significance to ensure the laser system security running.
Extinction characteristic of graphite smoke for terahertz wave
Qi-chao Wang, Jia-chun Wang, Da-peng Zhao, et al.
Graphite with good extinction performance can be used as electro-optical passive jamming material for infrared and laser detection. In order to acquire the extinction characteristic of graphite smoke for terahertz wave (THz wave), graphite powder was dispersed in a KBr matrix with concentrations of 0.6 wt% and 1.0 wt% respectively, and those composites were processed in the stoving system and were then pressed into pellets. Meanwhile, the pure KBr powder pellet was prepared with same method under same condition. By utilizing THz-TDS, the THz transmission spectrums of those samples were measured in the frequency range 0.2-1.1 THz. Then, the absorption coefficients of those samples were deduced based on the material parameter estimation method. The experimental results indicate that the absorption coefficients of those samples are enhanced with the increasing THz frequency and that of them are improved with the concentrations of graphite at the same frequency. The results obtained demonstrate that THz wave has strong penetration capacity through graphite smoke and THz radar will be promising for use to make up for the deficiency of the infrared and laser detection system and to detect the targets coated with graphite smoke.
Object reconstruction from thermal and shot noises corrupted block-based compressive ultra-low-light-level imaging measurements
In this paper, block-based compressive ultra low-light-level imaging (BCU-imaging) is studied. Objects are divided into blocks. Features, or linear combinations of block pixels, instead of pixels, are measured for each block to improve system measurement SNR and thus object reconstructions. Thermal noise and shot noise are discussed for object reconstruction. The former is modeled as Gaussian noise. The latter is modeled as Poisson noise. Linear Wiener operator and linearized iterative Bregman algorithm are used to reconstruct objects from measurements corrupted by thermal noise. SPIRAL algorithm is used to reconstruct object from measurements with shot noise. Linear Wiener operator is also studied for measurements with shot noise, because Poisson noise is similar to Gaussian noise at large signal level and feature values are large enough to make this assumption feasible. Root mean square error (RMSE) is used to quantify system reconstruction quality.
Study on design and experiment of safe illumination system based on optical fiber guiding light
Jie Liu, Fei Yu, Yang Yan
The optical fiber lighting is a new development on fiber application techniques in recent years. On the basic of Fresnel lens and optical fiber coupling models, the coupling device is designed reasonably through optical simulation, and then it verifies the effects of coupling through experiments. According to the experimental data, lens coupling mode and high efficiency optical fiber are chosen. At last, output device is fixed on the optical fiber. Its layout method is confirmed that have reached the requirements of the lighting standard, which provides a great technical support for realizing the large scale safety lighting system in the future.
A segmental dispersion compensation method to improve axial resolution of specified layer in FD-OCT
Bochen Wang, Zhuqing Jiang, Yujie Hu, et al.
A segmental dispersion compensation method is proposed to compensate the dispersion in frequency domain optical coherence tomography. Tomographic imaging for epidermal layer of an onion slice is achieved in the experimental setup using optical fiber. The axial resolution of the tomography can be improved by using segmental dispersion compensation, because this dispersion compensation method employs segmental dispersion coefficients for the different lateral positions in one specific layer. Comparing with the traditional dispersion compensation method, segmental dispersion compensation method has the capability of separating the specified layer of sample and eliminating the dispersion broadening effect of specified layer.
Error analysis of standard wave-front reconstruction based on spatial light modulator
Xiao Ma, Shijie Liu, Zhigang Zhang, et al.
The invention of spatial light modulator (SLM) promotes the development of aspheric surface test. SLM has the advantage of real-time and low-cost in comparison with the etching computer-generated hologram(CGH) plate. The pixel-structure of SLM, which includes the pixel pitch, gray-level number and black matrix, has great significance on the reconstructed wave-front quality. In this paper, the effects of SLM pixel pitch, gray-level number and black matrix are analyzed by Fresnel diffraction theory and computer simulation. In the simulation, a concave spherical wave-front with a radius of 1000 mm is generated by the SLM with different pixel pitch, gray-level numbers and aperture ratios, respectively. The results show that the quality of the reconstructed wave-front gets poorer as the pixel pitch increases, the gray-level number decreases or the aperture ratio reduces. This work can guide the selection of the SLM in the aspheric surface test.
Steady-state and time-resolved fluorescence spectroscopic studies on the interaction between bovine serum albumin and Ag-nanoparticles
Manping Ye, Yarong Shi, Huacai Chen
The interaction between bovine serum albumin(BSA) and Ag-nanoparticles was studied under a pH 7.4 buffer system by time-resolved fluorescence technique combined with the steady-state absorption and fluorescence spectrum. With Ag-nanoparticles, the BSA showed blue shift of fluorescence from 335nm to 332.5nm, accompanied by the fluorescence intensity decreasing. When adding the Ag-nanoparticles to the three fluorescent amino acids tryptophan(Trp), tyrosine(Tyr)and phenylalanine(Phe), only Trp displayed peak shift which from 346.5nm to 341nm. Strong interaction between BSA and the Ag-nanoparticles may come from Trp residue. Time-resolved fluorescence gave that BSA had only one fluorescence lifetime around 6ns from 308 to 313K. When adding Ag-nanoparticles, two fluorescence lifetimes appeared. One is a little above than 6ns and the other is around 3ns. The two Trp residues in 134th and 212th position may give contribution to the changes of the fluorescence lifetime. The 134th Trp residue is probably protected by BSA molecule structure and basically don't contact with Ag-nanoparticles, which shows little change of fluorescence lifetime. The 212th Trp residue is likely the target of the Ag-nanoparticles. The Ag-nanoparticles changed the microenvironment of BSA around the 212th Trp residue and therefore increases the exposure of the 212th Trp and the 134th Trp .
Variable angle transmittance of silver grid transparent electrodes
Yuan-Yuan Zhao, Mei-Ling Zheng, Xian-Zi Dong, et al.
We focus on investigating the optical transmittance of silver grid transparent electrodes (SGTEs) in variable angle view theoretically and experimentally, rather than the optical transmittance under the normal incidence. The variable angle transmittance (VAT) values of SGTEs are measured on a home-made experimental setup. The experimental results about difference of the transmittance difference under different angles are small and negligible, although the measured angle is changed. Theoretically, the physical mechanism on nearly constant transmittance for different angle view can be well explained according to the theory of geometrical optics. This study provides an approach for investigating the VAT values of SGTEs in a controllable fashion and the influence of viewing angle of the touch screen.
Measurement accuracy analysis for crystal plane spacing of nitride epitaxial layer by x-ray diffraction
Jianjun Cui, Sitian Gao
In order to realize high accuracy measurement of the physical dimension of unit cells in a crystal lattice, the measurement accuracy analysis for crystal plane spacing of nitride epitaxial layer is discussed. An angular analysis for X-ray diffractometer system is established and the measurement uncertainty from the experimental apparatus, measurement method are also analyzed. Experimental results indicate that the accuracy of the system’s angular can get U = ±0.01° (k=2) and the measuring accuracy of lattice plane spacing is within 0.01% of the d-spacing. These results represent an improvement in the existing measurement capabilities by more than an order of magnitude and make more numerous systematic effects visible and reproducible.
Method to fabricate orthogonal crossed gratings by an interference fringe based alignment technique
Hengyan Zhou, Lijiang Zeng
In order to fabricate orthogonal crossed gratings, we propose an interference fringe based alignment technique to adjust the angle between the two Lloyd’s mirrors to be 90° in the dual Lloyd’s mirror interferometer. An exposed crossed grating is put back to the exposure system and rotated about 90° around its normal direction. By observing the fringe spacing of the interference fringes generated by the diffracted beams of different orders, we can adjust the angle between the two Lloyd’s mirrors to be 90°. Simulation results indicate an orthogonality error smaller than 4″ can be obtained by this method. We fabricated a crossed grating with 0.30″ orthogonality error.
Characterization of Akiyama probe applied to dual-probes atomic force microscope
Hequn Wang, Sitian Gao, Wei Li, et al.
The measurement of nano-scale line-width has always been important and difficult in the field of nanometer measurements, while the rapid development of integrated circuit greatly raises the demand again. As one kind of scanning probe microscope (SPM), atomic force microscope (AFM) can realize quasi three-dimensional measurement, which is widely used in nanometer scale line-width measurement. Our team researched a dual-probes atomic force microscope, which can eliminate the prevalent effect of probe width on measurement results. In dual-probes AFM system, a novel head are newly designed. A kind of self-sensing and self-exciting probes which is Nanosensors cooperation’s patented probe—Akiyama probe, is used in this novel head. The Akiyama probe applied to dual-probe atomic force microscope is one of the most important issues. The characterization of Akiyama probe would affect performance and accuracy of the whole system. The fundamental features of the Akiyama probe are electrically and optically characterized in “approach-withdraw” experiments. Further investigations include the frequency response of an Akiyama probe to small mechanical vibrations externally applied to the tip and the effective loading force yielding between the tip and the sample during the periodic contact. We hope that the characterization of the Akiyama probe described in this paper will guide application for dual-probe atomic force microscope.
Model-based x-ray energy spectrum estimation algorithm from CT scanning data with spectrum filter
With the development of technology, the traditional X-ray CT can’t meet the modern medical and industry needs for component distinguish and identification. This is due to the inconsistency of X-ray imaging system and reconstruction algorithm. In the current CT systems, X-ray spectrum produced by X-ray source is continuous in energy range determined by tube voltage and energy filter, and the attenuation coefficient of object is varied with the X-ray energy. So the distribution of X-ray energy spectrum plays an important role for beam-hardening correction, dual energy CT image reconstruction or dose calculation. However, due to high ill-condition and ill-posed feature of system equations of transmission measurement data, statistical fluctuations of X ray quantum and noise pollution, it is very hard to get stable and accurate spectrum estimation using existing methods. In this paper, a model-based X-ray energy spectrum estimation method from CT scanning data with energy spectrum filter is proposed. First, transmission measurement data were accurately acquired by CT scan and measurement using phantoms with different energy spectrum filter. Second, a physical meaningful X-ray tube spectrum model was established with weighted gaussian functions and priori information such as continuity of bremsstrahlung and specificity of characteristic emission and estimation information of average attenuation coefficient. The parameter in model was optimized to get the best estimation result for filtered spectrum. Finally, the original energy spectrum was reconstructed from filtered spectrum estimation with filter priori information. Experimental results demonstrate that the stability and accuracy of X ray energy spectrum estimation using the proposed method are improved significantly.
Fixtureless nonrigid part inspection using depth cameras
Hanwei Xiong, Jun Xu, Chenxi Xu, et al.
In automobile industry, flexible thin shell parts are used to cover car body. Such parts could have a different shape in a free state than the design model due to dimensional variation, gravity loads and residual strains. Special inspection fixtures are generally indispensable for geometric inspection. Recently, some researchers have proposed fixtureless nonridged inspect methods using intrinsic geometry or virtual spring-mass system, based on some assumptions about deformation between Free State shape and nominal CAD shape. In this paper, we propose a new fixtureless method to inspect flexible parts with a depth camera, which is efficient and low computational complexity. Unlike traditional method, we gather two point cloud set of the manufactured part in two different states, and make correspondences between them and one of them to the CAD model. The manufacturing defects can be derived from the correspondences. Finite element method (FEM) disappears in our method. Experimental evaluation of the proposed method is presented.
Analysis of the mechanics and deformation characteristics of optical fiber acceleration sensor
Zong-kai Liu, Yu-ming Bo, Ben-mou Zhou, et al.
The optical fiber sensor holds many advantages such as smaller volume, lighter weight, higher sensitivity, and stronger anti-interference ability, etc. It can be applied to oil exploration to improve the exploration efficiency, since the underground petroleum distribution can be obtained by detecting and analyzing the echo signals. In this paper, the cantilever beam optical fiber sensor was mainly investigated. Specifically, the finite element analysis method is applied to the numerical analysis of the changes and relations of the optical fiber rail slot elongation on the surface of the PC material fiber winding plate along with the changes of time and power under the action of sine force. The analysis results show that, when the upper and lower quality blocks are under the action of sine force, the cantilever beam optical fiber sensor structure can basically produce synchronized deformation along with the force. And the optical fiber elongation length basically has a linear relationship with the sine force within the time ranges of 0.2~0.4 and 0.6~0.8, which would be beneficial for the subsequent signal acquisition and data processing.
Digital holographic imaging for diffuse-reflection metal surface with strong feature
A method of digital holographic imaging for strong diffuse-reflective metal surface is presented. For a strong diffuse-reflection object, the DC term of Fourier spectrum of the hologram is removed by subtracting the patterns the reference beam and object beam from the hologram, which effectively eliminates the influence of the zero-order of the spectrum image on actual information. In view of the more extensive area of Fourier-spectrum region of the hologram for a diffuse reflection object, the spectrum filtering windows is taken as a half area of the Fourier-spectrum region. According the removal of the zero-order term and the use of the half area of filtering windows, the reconstruction imaging for the surface of an alloy plate is achieved, in which both amplitude and phase images are obtained, respectively.
Development of automated self-calibration spectra-radiometer
Xin Li, Li-na Xun, En-chao Liu, et al.
Test site vicarious calibration provides an absolute radiometric calibration for sensors. Surface reflectance is a critical parameter to be measured during a vicarious calibration field campaign. In order to realize long-term high precision observations of surface spectral reflectance in solar reflective bands, Automated Self-Calibration Spectra-Radiometer (ASCSR) was developed. ASCSR measures the global irradiance and the ground reflected radiance respectively with high spectral resolution from 400nm-2400 nm, the ratio of the two measurements is the surface reflectance. The degradation influences of instrument sensors and optical elements are removed by ratio-measurements and self-calibration. In the past two years ASCSR deployed in Dunhuang test site for continuous spectral reflectance measurements over 4 weeks. The measurements result of ASCSR is compared with traditional measurements which used SVC spectra-radiometer.
S-F graphic representation analysis of photoelectric facula focometer poroo-plate glass
Yilin Tong, Xuecai Han
Optical system focal length is usually based on the magnification method with focal length measurement, poroo-plate glass is used as base element measuring focal length of focometer. On the basis of using analysis of magnification method to measure the accuracy of optical lens focal length, an expression between the ruling span of poroo-plate glass and the focal length of measured optical system was deduced, an efficient method to work out S-F graph with AUTOCAD was developed, the selecting principle of focometer parameter was analyzed, and Applied examples for designing poroo-plate glass in S-F figure was obtained.
Dynamic three-dimensional shape measurement for specular freeform surfaces with the quaternary orthogonal grid fringes
Xueyang Xu, Xiangchao Zhang, Min Xu
Deflectometry is a promising method for freeform surfaces due to its wide applications and ease of implementation, but it is not robust against environmental noise and vibrations. A new deflectometry method using the quaternary orthogonal grid fringes is proposed to retrieve the surface slopes. Combined with a classic N-step phase-shifting technique, only one image is required to extract the two perpendicular directional phases instead of two groups of phase shifted fringes. The color of each pixel can be encoded by red, green and blue components. In each color component, two perpendicular fringe patterns compose quaternary orthogonal grid fringes. In practice, the relative shift between different colors is set depending on the lateral resolution of the camera lens and the zoom relation of the object-image. The object-image relationship can be established by using only one distorted colorful orthogonal fringe pattern reflected via the surface. This process is fast and stable because the RGB codes of every block are significantly different to its neighbor in at least one color component. This method is suitable for dynamic measurement of specular objects, and the influence of varying environment and moving objects can then be eliminated.
Front Matter: Volume 10155
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Front Matter: Volume 10155
This PDF file contains the front matter associated with SPIE Proceedings Volume 10155 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.