2017 Vol. 38, No. 6

OE System and Engineering
Design of sensor layout in photoelectric platform based on finite circle method
Liu Hu, Zhu Lei, Gao Yu, Tian Jie, Duan Wenbo, Zhao Wei
2017, 38(6): 857-862. doi: 10.5768/JAO201738.0601001
To improve the optical axis stabilization, the static unbalance torque of airborne photoelectric platform must be minimized with the help of balancing weight in assembling stage.An effective layout optimization method of multiple sensors in the airborne photoelectric platform in two-axis four-gimbal form was proposed to reduce the static unbalance torque in the design stage.The finite circle method was employed to establish the module overlap constraint and the optimization algorithm of globally convergent method of moving asymptotes was used to solve the layout optimization problem fast.Results show that this method succeeds in reducing the static unbalanced torques of the inner azimuth and pitch axes by 45% and 68%, respectively, which effectively reduces the balancing weight and improves the performance of EO platform.
Research on a kind of precision rotary drive mechanism
Wang Xinguang, Fan Dapeng, Liu Hua, Tan Ruoyu, Xie Xin, Chen Ning
2017, 38(6): 863-871. doi: 10.5768/JAO201738.0601002
The inner gimbal of electro-optical pod with two-axis and four-gimbal structure is usually driven directly by torque motor, its stability accuracy is only tens of micro radians. To achieve the stability accuracy of several micro radians, a flexure-based precision rotary drive mechanism driven by piezoelectric actuators was proposed, which acted as the inner drive of electro-optical pod. The configuration scheme of precision rotary drive mechanism was introduced, and the drive capability of piezoelectric ceramics was explored. The rotation stiffness, resonance frequency and geometric parameters were designed in detail. The electromechanical simulation model was obtained. In addition, a prototype was fabricated and tested for performance verification. The results show that the travel range is 509.1 μrad, the resolution is better than 0.5 μrad, the sinusoidal signal tracking error of 1 Hz and 100 μrad is less than 3 μrad, and the resonance frequency is about 1 KHz. These results can all meet the design goals.
Research and implementation of OPD algorithm for spatial gravitational wave telescope based on ZEMAX and Python softwares
Xu Mingming, Xu Teng, Hu Zhongwen, Zhang Huatao, Ji Hangxin, Jiang Haijiao, Wang Lei
2017, 38(6): 872-876. doi: 10.5768/JAO201738.0601003
The optical design softwares ZEMAX and Python were used to realize the precision solution of optical path difference (OPD) for spatial gravitational wave telescope.The dynamic data exchange(DDE) closed-loop communication between ZEMAX and Python was realized. First, the Python software processed the data of telescope mirror after the finite element analysis, and transmitted the analysis results to the ZEMAX with DDE for tracing ray.Secondly, the ZEMAX software transferred the ray coordinate value to the Python software through the DDE. Lastly, the Python software calculated the OPD and wavefront changes caused by rigid body translation through the global coordinate system. Through simulating the deformation of the gravitational wave telescope with the temperature change of 1 mK, the OPD and wavefront variation of the spatial gravitational wave telescope was solved by means of ZEMAX software and Python software. The results show that the OPD precision reaches the order of 1e-13 meter, which can satisfy the requirements of telescope for pico-level stability.It is concluded that the method is feasible to calculate the OPD, and it provides a technical reference for the OPD analysis for the further mechanism design of the gravitational wave telescope.
Optical receiver design of open-path TDLAS detection system for gas Wu Guozhong, Wang Di, Li Dong, Qi Hanbing
Wu Guozhong, Wang Di, Li Dong, Qi Hanbing
2017, 38(6): 877-883. doi: 10.5768/JAO201738.0601004
In the open-optic path tunable diode laser absorption spectroscopy(TDLAS) detection system for gas, due to the surface finish degeneration of corner reflector during production and using and the atmospheric transmission disturbance, the incident direction of echo signal and the optical axis of receiving lens are not strictly parallel, resulting in the decrease of the system detection sensitivity.Aiming at this problem, firstly the offset of convergence point with the incident direction of echo signal different from the the optical axis of the Fresnel lens was analyzed, then a secondary optical element consisting of a conical reflector and a parabolic reflector was designed and its parameters were optimized by TracePro software.Moreover, the condensing performance simulation under the deviation range of echo incident angle in -6° ~ 6° was carried out.The simulation results show that the receiving angle of the optimized optical receiving module is 4.9° and the optical efficiency is 78.24%, the condensing performance is obviously improved comparing to the independent Fresnel lens and Fresnel lens-compound parabolic concentrator(CPC), the optimized component is applicable to the actual detection process.
High-precision alignment system of machine vision based on Hough transform
Wei Li, Guo Yujing, Lu Xiangning
2017, 38(6): 884-889. doi: 10.5768/JAO201738.0601005
As the integrated circuit(IC) characteristic size continues to decrease, the number of I/O pins is increasing. For high-density packaging, especially in 2.5D/3D packages, fast and accurate alignment of electronic components and substrates is critical. A precise optical vision alignment system was set up by using the high precision charge coupled device (CCD), and the Hough transform algorithm was utilized to calibrate the chip and the substrate. The image captured was preprocessed to remove the noise, and the alignment marks were extracted by using morphological edge detection method, and 4 sets of parallel straight lines were obtained by Hough transform. Finally, the displacement and the rotation angle of the substrate were calculated and the alignment was completed. The running time of the Matlab program is about 4.2 s, the rotation parameter error is less than 1.2 °, x and y axis translation errors are less than 1 pixel. The experimental results demonstrate that the optical visual alignment system based on the Hough transform algorithm can realize chip and substrate alignment quickly and accurately to meet the IC packaging requirements.
Optical design of endoscope telecentric measuring instrument with 90° visual angle
Wu Shuang, Xiang Yang
2017, 38(6): 890-895. doi: 10.5768/JAO201738.0601006
For the deep holes, tiny holes or blind holes within deep cavity, due to the limitation of the size, shape and structure of cavity, it is very difficult to detect the inner surface and the aperture location information in the cavity.Aiming at this problem, an endoscope optical probe for detecting the small hole features and state in cavity was designed.This probe is a small diameter endoscope which can achieve 90 ° angle of view, 20 mm large depth of field with the large magnification of -0.71×, the maximum distortion of 0.5%, and the full field-of-view modulation transfer function(MTF)near 0.1 at 166 lp/mm.The aperture detection accuracy is 0.01 mm, the resolution is 0.005 mm, and the optical system outer diameter is less than 5 mm.It can be used for detecting small aperture shape and location information in cavity parts with the cavity diameter range of 15 mm~45 mm and the aperture diameter range of 0.01 mm~4 mm.
Polarization calibration method of ground-based polarization imaging system for low earth orbit space objects
Wang Guocong, Chang Weijun, Hu Bo
2017, 38(6): 896-902. doi: 10.5768/JAO201738.0601007
For the polarization imaging system which was constructed in the adaptive optics system of ground-based telescope and imaged for low earth orbit space objects, a broadband polarization calibration method based on unpolarized standard star and onboard polarization state generator was proposed. This method, which contained two steps for polarization calibration based on nonlinear least-square fitting polarization calibration method, used the unpolarized standard stars as the light source and utilized the polarization state generator inserted in the first image plane of telescope system to modulate the polarization state of incident light. Then to verify the performance of this polarization calibration method, a simulation model based on coherent matrices and polarization ray tracing was constructed and corresponding simulation was carried out by Matlab. The simulation results show that this polarization calibration method can effectively decrease the influence of telescope polarization on the accuracy of polarization detection. And under the influence of random initial angle errors of polarization calibration elements within ±5°, the performance of this polarization calibration method can be affected tinily.
OE Information Acquisition and Processing
Moving object detection with adaptive threshold based on FPGA
Shao Peng, Yang Chen, Zhang Jinmin
2017, 38(6): 903-909. doi: 10.5768/JAO201738.0602001
Frame difference is one of the most widely used methods in moving object detection, for its advantages such as simple algorithm, less data to be processed, easy to be implemented and so on; however, frame difference method usually detects a moving object by using a specific threshold value measured under an invariable lightness condition, which limits its application in variable illumination situations. According to the above problem, the illumination-lightness-threshold table was created based on the lightness in the hue, saturation, lightness (HSL) color space to dynamically adjust the threshold value for different illumination conditions. After simulation, a detection system was implemented by field-programmable gate array (FPGA), and an experimental setup was built to verify the system. Experimental results show that, the recognition rate reaches 93% and 95% for a moving target with 3.0 m/s and 0.5 m/s velocity under 90 W/m2 illumination by the adaptive method, which is similar to the method with a large fixed threshold; under 0.59 W/m2 illumination, the recognition rate reaches 84% and 92% respectively for the two moving speeds above, which is similar to the fixed threshold method with a small threshold value.
Binocular vision navigation algorithm for AAR of flying boom UAV
Bao Jiyu, Wang Long, Dong Xinmin
2017, 38(6): 910-916. doi: 10.5768/JAO201738.0602002
Aiming at the estimation problem of relative position and attitude of autonomous aerial refueling(AAR) of flying boom UAV in close formation stage, the relative pose estimation algorithm based on binocular vision is studied. The algorithm uses Harris method to extract feature points and quickly matches them. The 3D coordinates of feature points in camera coordinate system are obtained by Sampson method, and the objective function is established with the minimum square sum of reconstructed error. The position and pose parameters are solved by unit quaternion method. Finally simulation platform is used to verify the effectiveness of the algorithm. Results show the relative position error is better than 0.1 m, the relative attitude error is less than 0.5°, and the accuracy meets the requirements of AAR relative navigation performance.
Total least square algorithm applied in multi-stationintersection of optical theodolite
Yu Guodong, Wu Kexin, Wang Chunyang
2017, 38(6): 917-922. doi: 10.5768/JAO201738.0602003
Horizontal projection method, which is applied in calculating coordinates of aerial bursting points, has major problem in exploiting redundancy observations and in filtrating optimal results from multi-group solutions. Intersection algorithm based on least square, although able to solve the above problems, is influenced by initial value of a larger, iterative slow or even divergent.An intersection algorithm based upon total least square is proposed. In the process of iterative computation, weight matrix is adjusted continuously until a certain precision requirement is satisfied. This algorithm is validated by combining simulation data. Results show that proposed algorithm can obtain better results when initial value is larger, and it is not easy to diverge. It can get better results by 10 iterations or less, and precision can reach 0.3 m when distance from station to target is 1 500 m. This algorithm takes into account both observation error and model linearization error, which greatly reduces influence of initial value and improves convergence speed, and can accurately calculate three-dimensional coordinates of aerial bursting points.
Analysis of Mie scattering spectrum based on guided filtering
Xiao Shaorong, Zhou Weiwei
2017, 38(6): 923-930. doi: 10.5768/JAO201738.0602004
In order to improve the accuracy of particle size inversion, eliminate the scattering spectrum noise, the Mie scattering spectrum data of different angles were filtered by one dimensional guided filter, and the characteristics of the guided filter were analyzed. In order to solve the problem of local noise caused by the guidance data, a wavelet-guided filtering algorithm was proposed. The results show that the filtering result is similar to that of the wavelet filter in the small scattering angle, but the filtering effect is better than the wavelet filter in the large scattering angle, and the pulse noise may be filtered out. The result of wavelet-guided joint filtering is the same as that of the guided filter at 15°, the filtering effect is better than that of the wavelet filter or the guided filter at 45° to 90°, and the local noise caused by the guidance data can be removed.
Wire harness terminals microscopic image segmentationin chromaticity brightness space
Lu Bibo, Liu Tiantian, Guo Hairu
2017, 38(6): 931-936. doi: 10.5768/JAO201738.0602005
In order to extract relative data for quality control of wire harness terminals, an microscope image segmentation for wire harness terminals in chromaticity brightness space was proposed. This method divided the harness terminal by threshold method using the color distribution characteristic of the harness terminal micrograph.After analyzing the color distribution character, the microscopic image was first converted to brightness chromaticity space, and to insure the color homogenization within the image, the chromaticity vector was filtered. Then for the color channel, an optimal thresholding was determined for the two cases: the histogram with two peaks and one valley and the histogram with two peaks and two or more valleys. Finally, the mathematical morphology was performed on the binary image to produce the inner contour. The experimental results show that the circumference deviation of the inner diameter of the terminal is less than 0.1%, which indicates that the method can segment the harness terminal image completely and accurately.
Double-image encryption algorithm based on discrete fractionalrandom transform and weighted histogram cross permutation
Zhao Yulan, Yuan Quande, Meng Xiangping
2017, 38(6): 937-946. doi: 10.5768/JAO201738.0602006
In order to achieve the synchronously encryption of two images, reduce the transmission load and improve the ability of anti-plaintext attack, a double-image encryption algorithm was proposed by discrete fractional random transform and weighted pixel chaos scrambling. A new Tent map was designed by introducing two order parameters into the Tent mapping. Then the weighted histogram model was constructed according to the plain pixel value to generate the initial value of new tent map by combining with the 256 bits external key. Two sets of random sequences were outputted by using the initial value to iterate the fractional order Tent map to confuse the two pixel positions for obtaining two scrambling cipher. The sparse representation of two scrambling cipher was done by discrete wavelet transform (DWT) technology. The random circular matrix was defined according to the chaotic sequence, and the measurement matrix of two scrambling cipher was obtained by jointing sparse representation. The image fusion model was established based on random mask and modulation phase mask to take two measurement matrices into composite image. The composite image was diffused based on discrete fractional random transform to obtain the cipher. Experimental results show that the proposed algorithm has stronger ability to resist plaintext attack which NPCR、UACI of cipher is up to 99.83%, 34.57%, and higher user response in comparison with current multi-image encryption scheme. This algorithm has high encryption security which can effectively resist external attacks in the network and ensure the safe transmission of images.
Optical Metrology and Measurement
Measurement of dual frequency interference fringe morphologyunder parallel optical wavefront modulation
Wang Yi, Liu Huiyan, Song Baogen
2017, 38(6): 947-952. doi: 10.5768/JAO201738.0603001
The grating projection is usually used in traditional profilometry, and the non-sinusoidal of fringe and the limitation of fringe density can affect the accuracy of topography measurement. In order to realize the adjustability of high-density sinusoidal fringe projection, the parallel light interference projection is used to form bright and high contrast sinusoidal fringe, so that the sine distortion of fringes is avoided. In parallel wavefront modulation, the desired fringe frequency is obtained by adjusting the intersection angle of the two beams by phased array, and the adjustable fringe projection is realized, then the modulated dual frequency are applied to improve the phase unwrapping accuracy. The restoration of an object with maximum height of 35.80 mm under the condition of single frequency and dual frequency unwrapping was compared, and the relative error of the highest point recovery was 2.7% and 1.6%, respectively. The experimental results show that the method is effective and feasible, and has high precision.
Method for measuring delivery trajectory and attitudeof a certain type of airborne weapon
Zhang Jianhua
2017, 38(6): 953-957. doi: 10.5768/JAO201738.0603002
Due to the special characteristics of the installation location for testing camera in the flight test of a certain type of airborne weapon, the field intersection area of camera is smaller, so as the trajectory and attitude motion parameters of the weapon delivery process cannot be calculated by using the conventional image measurement method.Aiming at this problem, a set of scheme for measuring airborne weapon delivery test image under conditions of close range and large dip angle was designed.Through designing the 90° bend lens and the 120° bend lens to change the camera mounting position, the problem of weapon delivery image acquisition was solved.By establishing the large dip angle multi-camera data-joint calculation model, the trajectory and attitude measurement of the weapon was realized.The simulation results show that using the maximum trajectory measurement error by this program is less than 2 cm, which can meet the flight test accuracy requirements.
Accuracy angular measurement method in alignmentprocess for Cassegrain telescope
Li Bin, Chen Jiayi, Wang Haichao, Huo Tengfei
2017, 38(6): 958-962. doi: 10.5768/JAO201738.0603003
In order to accurately measure the tilt amount of the secondary mirror in coaxial three reverse camera, a new method for measuring angle was proposed, which used the combination of a large-aperture interferometer and a theodolite. Taking the primary mirror as the measuring reference, while the included angle of two mirrors was small, the large-aperture interferemeter was used to measure the interference fringes of two mirror simultaneously. While the included angle was too large and the secondary mirror did not involve the interference fringes, a theodolite was added for autocollimation from the interferometer and secondary mirror to measure the included angle of two mirrors indirectly. Examples and analog computations show that for the secondary mirror tilt angle, its measuring error can be within 0.5″. The results indicate that the measurement method has the characteristics of strong universality and high precision, and can overcome the problem of insufficient measurement accuracy of traditional detection method.
Measurement method of response matrix for adaptiveoptics systems based on turbulence model
Li Mingxing, Xiao Xiangguo, Kang Wenli
2017, 38(6): 963-967. doi: 10.5768/JAO201738.0603004
In order to improve the correction accuracy of liquid crystal (LC) adaptive optical systems, a method based on turbulence model for measuring the interaction matrix (IM) was proposed. The wavefronts applied to the LC corrector are the linear combination of Karhunen-Loeve modes which are used to fit the measured aberrations and the coefficients of these modes obey the Kolmogorov atmospheric turbulence model. Comparing with traditional single mode and multiple modes method, the new method has a stronger anti-noise ability and can produce a significant improvement on IM measurement. Under the condition of the signal-to-noise ratio (SNR) of 10, when the repetition rate is 1, 5 and 10, respectively, the corresponding Strehl ratio is 0.06, 0.02, 0.49 and 0.23, 0.40, 0.67, corrected by using the IM obtained with the tradional single mode method and multi-mode method, respectivily, while that of the new method can reach 0.34, 0.56, 0.68.
Optical Element and Fabrication
Difference analysis of non-standard light source in color measurement
Zhao Youquan, Liang Xiuli, Liu Xiao, Zhang Yihe, Guo Dexia, Wang Xianquan
2017, 38(6): 968-973. doi: 10.5768/JAO201738.0605001
Due to spectral power distribution differences, different light sources have different color temperatures and color rendering indices, and color measurement differences vary widely. D65 standard light source closest to daylight color, is standard light source color measurement recommended by international commission on illumination (CIE). But its price expensive, working conditions harsh and difficult to get, non-standard light source is commonly used in actual color measurement instead. In order to study color measurement difference of non-standard light source, a set of solution colorimetric system was designed. Using high pressure pulsed xenon lamp, LED lamp and halogen lamp as light source, and nitrite color experiment as the basis, color difference of three light source were calculated with chromaticity principle. Results show that xenon lamp, LED lamp spectrum distribution is more uniform, the chromaticity coordinates are close to white E (0.33, 0.33), the measured color is close to real color, and halogen tungsten color measurement error is relatively large. Average color difference ΔEab of Xenon lamp and LED lamp in L*a*b* space color measurement is within 10 NBS, while average color difference ΔEab of both and halogen tungsten is above 20 NBS.
Optical Element And Fabrication
Residual intensity modulation of Y-waveguide modulator
Weng Cangjie, Yang Dewei, Zheng Yuansheng, Zhao Yan, Yao Tianlong
2017, 38(6): 974-978. doi: 10.5768/JAO201738.0605002
In order to improve modulation performance of Y waveguide modulator so as to improve the overall performance of fiber optical gyroscope(FOG), mechanism for residual intensity modulation (RIM) of Y-waveguide phase modulator used in FOG are analyzed, namely waveguide defects and substrate stray light reflection. Then the influence of RIM on characteristics of FOG system, and calibration factor of RIM influence mainly on FOG are described. Waveform characteristic of RIM of different Y-waveguide phase modulators and its value of linear components and interference are tested. Difference of RIM of different Y waveguide modulators is large. The value of RIM with good performance Y-waveguide modulator can be controlled within 1‰. Influences of temperature on waveform characteristic of RIM are tested. Fluctuations of RIM value can reach 20% under extreme temperature. Finally according to RIM mechanism and ratio of linear interference components, the measures for improving Y waveguide technology are put forward.
Design of microscope system based on depth from focus
Chen Jian, Wang Lingyang, Chen Dequan, Zhang Maolin
2017, 38(6): 979-984. doi: 10.5768/JAO201738.0605003
According to the problems of low degree of automation, slow process of focusing and high requirement of operator experience caused by traditional manual focusing microscope, a new optical microscope system based on depth from focus was proposed. Firstly, according to the general microscope structure with auto-focusing based on image processing, a set of microscope system was designed, constituted of ARM development board, touch-sensitive LCD, Arduino UNO development board, infrared tube, industrial digital microscope and stepping motor, etc. Then, a focusing window selection method combining regions of interest with different sizes was proposed based on the characteristics of touch-sensitive LCD screen.And an improved method with fault tolerant was put forward based on the mountain climb searching algorithm and the common gradient function as the image definition evaluation function. Furthermore, the real-time, sensitivity and fault-tolerant performance for different image definition evaluation functions and sizes for selection window were tested in the experiment.The results show that the system has high reliability.
Design and implementation of portable LED uniform light source with diffuse reflection
Yang Chaopu, Fang Wenqing, Liu Mingbao, Li Chun, Han Xi, Zhang Meili, Liu Yanfeng
2017, 38(6): 985-989. doi: 10.5768/JAO201738.0605004
In order to meet the needs for standard light source of photoelectric detectors during calibration and correction, using the integrating sphere technology, it was designed that a button battery-powered portable LED uniform light source with diffuse reflection. The assembly drawings, main parts 3D drawing and circuit diagram of the light source were given and detailed described. By analyzing the gray value of each pixel of charge coupled device (CCD) photograph at light source outlet using Matlab, it was found that the light intensity evenness was 95.1% in ϕ14 mm range of light outlet. Besides, through the analysis of light intensity uniformity and diffuse reflection of light outlet by Ocean Optics USB 2000+ spectrometer, it was found that the light intensity dropped by 2.93% and 6.30%, respectively, at two positions along the light outlet radial direction, compared with the central position.The light intensity of central position was suppressed by 6.30% when the flat of light outlet was rotated 10°.Test analysis results show that the light source has a good uniformity and diffuse reflection, the design has some practical and reference values for photoelectric detectors calibration.
Infrared Technology
NETD and SNR analysis of laser jamming infrared imaging system
Xu Qiang, Pan Feng, Huang Li, Wang Xingtao
2017, 38(6): 990-994. doi: 10.5768/JAO201738.0606001
Noise equivalent temperature difference(NETD) and signal to noise ratio(SNR) are one of the important parameters to measure performance of infrared imaging system, which is related to various performance parameters of the detector. Performance parameters of different types of infrared detectors are analyzed after laser irradiation interfering infrared detection system. Through theoretical calculation and calculation, system NETD and SNR curve before and after YAG (wavelength 1.06 μm) laser jamming are compared. NETD after laser damage is two to three orders of magnitude larger than that of pre-damage. At the same time, SNR after laser jamming is two orders of magnitude smaller than that before laser jamming. Influence of laser jamming on infrared detection system is derived.
High-precision measurement of focal length for long-focus infrared optical system
Huang Yang, Wang Chunyu, Niu Jinchuan, Wang Cong, Zhang Shengjie, Zong Xiaoying
2017, 38(6): 995-998. doi: 10.5768/JAO201738.0606002
In order to improve the accuracy of focal length measurement for long-focus focal infrared optical system, a new method is proposed, that includes interferometry, photoelectric auto-collimation, and laser tracking technique. Based on the wavefront interferometry optical path, it can be realized that the focal length for long-focus infrared optical system is measured with high accuracy, by using the features that the power of wavefront is very sensitive to the position of spherical mirror, and combining with the high-precision position measurement function by laser tracker and the high-precision angle measurement function by photoelectric autocollimator.A long-focus infrared optical system for aerial reconnaissance was tested in the experiment, whose theoretical focal length was 1 520 mm, and the testing error was analyzed according to the accuracy of the equipments. The standard deviation of 5 measurments results was 0.930 mm, and the measurement error was less than 0.2%, meeting the test technical requirements. The experimental result shows that the method is successful and effective to measure the focal length of long-focus infrared optical system accurately.
Thermal radiation characteristics of conformal dome in aero-dynamic environment
Xue Wenhui, Wang Hui, Bao Chunhui, Fan Zhigang
2017, 38(6): 999-1005. doi: 10.5768/JAO201738.0606003
The high-temperature dome produces intense infrared radiation, which forms the background noise on the detector receiving surface and seriously affects the image quality. To assess the performance degradation as a result of aerodynamic heating of the conformal dome flying at high speed, this paper established the multi-physics coupling model of conformal domes under aerodynamic heating environment, the dome thermal radiation emission and transmission model. Based on these models, the temperature field, the stress field, the strain field and the deformation field of conformal domes were obtained, and the imaging quality of high-speed aircraft affected by heat radiation of conformal dome was analyzed. Results show that as time goes on, the maximum irradiance of the detector is increasing. At 10 s, the minimum value of the thermal interference irradiance of the conformal shroud at 0° attack angle is 0.094 W/m2, and the maximum value is 0.108 W/m2. Compared with conformal domes under the same working condition, the maximum irradiance of the spherical dome at 10 s is about 12 times and 7 times of the maximum irradiance of ellipsoid and parabolic dome, respectively. Conditions thermal radiation interference of the conformal dome has less effect on the detection system comparing with spherical dome, and does not have a fatal effect on the detection performance of the detector.
Laser Technology
Spatial coupling of semiconductor laser in guidance of laser remote control
Ou Qiuye, Kang Tingting, Wang Cheng, Xi Weisheng, Xu Jing, Wu Yingchun
2017, 38(6): 1006-1011. doi: 10.5768/JAO201738.0607001
Aiming at the far field property of high power pulsed semiconductor laser and the requirement of laser power density and spot uniformity by laser guidance, the coupling scheme of multi-aperture space is proposed and the advantages are analyzed theoretically. For nanometer multilayer chip high power semiconductor laser polarization, the polarization beam combining of two high power semiconductor array lasers is studied based on the principle of polarization multiplexing. Experimental results show that output power of the system is almost twice as high as that of a single laser, and the coupling of multi-aperture coupling and polarization coupling can meet the light spot requirements of remote control guidance.
Effect of concentration on propagation characteristics of polarized laser in oil-mist diffusion
Sun Chen, Zhao Yiwu, An Zhongde, Fu Qiang, Zhan Juntong, Duan Jin
2017, 38(6): 1012-1017. doi: 10.5768/JAO201738.0607002
Aiming at the influence of particle concentration on the laser transmission process in the atmospheric environment, taking the oil mist particles as the research object, the semi-physical simulation experiment of polarization laser transmission was carried out by using the inhomogeneous environment generated by the oil mist particles during the diffusion process. In the experiment, 532 nm lasers were used to study the polarization state variation of horizontal linearly polarized light, 45° linearly polarized light and left circularly polarized light during oil mist diffusion. The diffusion environment was quantitatively calibrated using the particle size analyzer. The experimental results show that the higher the concentration is, the greater the randomness of the change of polarization, and the polarization-maintaining ability of the circularly polarized light is better than that of the linearly polarized light. At the same concentration, the polarization-maintaining ability of 0°linearly polarized light is better than 45 ° linearly polarized light. In the case of extremely high concentrations, when the volume concentration is 2 mg/L or above, the linearly polarized light tends to coincide with the retention of circularly polarized light.
Modeling and simulation of multi-color CCD detector under super-continuum laser jamming
Song Dongsheng, Guo Liang, Guo Bingtao, Li Shiyao, Wang Tan
2017, 38(6): 1018-1024. doi: 10.5768/JAO201738.0607003
Considering the spectral characteristics of super-continuum laser and the signal conversion mechanism of multi-color charge coupled-device (CCD) detector, the simulation model of multi-color CCD detector imaging under super-continuum laser jamming was built. On the basis of the working principle of multi-color CCD, the transfer and transport rules of saturated and crosstalk signal were theoretically analyzed. Then, according with the structure of multi-color CCD, the spatial distribution characteristic of laser energy on the CCD surface was studied with the aid of optical design software. Taking into account the above researches, the simulation model of monochromatic CCD saturation crosstalk effect interfered by super-continuum spectrum laser was established, based on this, combined with the CCD imaging multi-color visualization principle, it was realized to simulate the multi-color CCD output image interfered by super-continuum laser. Finally, the influence of different laser energy on the image quality of multi-color CCD was studied by introducing the image quality evaluation factor. Experimental result indicates that the laser power density is an important influence factor of the laser interference effect. As the laser energy increases, the image quality of the multi-color CCD decreases.