2016 Vol. 37, No. 5

OE System and Engineering
Color filter design method for multi-channel spectral acquisition system
Li Chan, Wan Xiaoxia, Xie Wei, Li Tianting, Liang Jinxing
2016, 37(5): 639-643. doi: 10.5768/JAO201637.0501001
The spectral reconstruction precision of multi-channel spectral acquisition system based on the commercial digital camera is greatly dependent on the filters used to acquire the image. In order to obtain optimal filter pair, which has excellent spectral reconstruction performance and is applicable to all image scenes, a color filter design method based on the principal component analysis is proposed in this work. Firstly, a number of widelyused color filters are collected and their transmittances are measured and then written in matrix form. Secondly, the proposed method is adopted to extract the first two principal components of the matrix. The normalized principal components are the transmittances of the desired synthetic filters. To compare the spectral reconstruction performance of the synthetic filters with the other filter pair obtained by a common used method, two virtual spectral acquisition systems were constructed with two pairs of filters. The performance of each system was evaluated in terms of chromatic difference and spectral root mean square error. The results indicate that the synthetic filters obtained by the proposed method have a better performance than the common used methods. In addition, the performance of the synthetic filters is stable when the target image scenes change.
Optical system design and stray light analysis on TV camera of vehicle electro-optical system
Wang Ling, Teng Guoqi, Chen Jiao, Zhang Jun
2016, 37(5): 644-650. doi: 10.5768/JAO201637.0501002
A dual-field TV camera was designed, which can realize target tracking in narrow field,and target capturing and observing in wide field. Both of the transfer modulation functions(MTFs) of the optical systems of the two field of views(FOVs) are more than 0.6 at 50 lp/mm frequency, the spot diameters are both smaller than the pixel size of 5.5 μm, and the distortions are less than 0.1%. The two FOVs share a common planar array CCD imaging device. And the light can be split through a prism. Considerting the ghost images due to the stray lights generated by the reflecting on the prism surfaces,the LightTools software was utilized to simulate and analyze the stray lights . The simulation indicates that when the half angle of field is between 5.7°~7.6° in wide field, and 2.6°~3.5° in narrow field,the incidences can be reflected by the down surface of the prism; when the half angle of field is between -2.7°~-3.5° in narrow field,the incidences can be reflected by the back surface of the prism. Then they can be focused on the image surface to form the ghost images and stray lights. The method of eliminating stray light in the rear of the split prism is adopted to suppress stray light. The simulation results show that the simulation analysis is correct,and the resolution proposed to suppress the stray lights can be proved to be valid.
Design and simulation research of InGaAs-MSM photodetector
Li Yong, Li Gang, Shen Hongbin, Zhong Wenzhong, Li Liang
2016, 37(5): 651-656. doi: 10.5768/JAO201637.0501003
An InGaAsmetalsemiconductormetal (MSM) photodetector was designed with interdigitated planar structure. Theoretical models were used to plot the variations of the dark current, the photocurrent, the capacity, and the cutoff frequency of the photodetector as a function of bias voltage and the interelectrode distance. The dark current of the detector was restricted in orders of pA by adding InAlAs Schottky barrier. The simulation results show that the detector has obvious light response. Under certain circumstances, the working frequency of the detector can reach 1.5 THz. Moreover,the samples of detector were fabricated, the dark current and photo response of the samples were tested. The test results are coincident well with the simulation results.
Structure-control co-simulation of electro-optic stabilization system using Matlab and ADAMS
Yang Xiaoqiang, Qi Yuan, Shi Leilei, Hu Bo, Cheng Gang
2016, 37(5): 657-662. doi: 10.5768/JAO201637.0501004
To study the stabilization precision and avoid deducing the complicate dynamic equation of multi-gimbal electro-optic stabilization system, a method for structure-control co-simulation using Matlab and ADAMS was developed. The step response of azimuth and elevation axes, the line-of-sight(LOS) angular velocity in inertial space under triaxis base linear vibration ,and the LOS stabilization precision under tri-axis base angular motion of 2° and 1 Hz were studied. The simulation results and the qualitative analysis are consistent, indicating that the method is useful and can be applied for new product development.
Design of collimating projection system used for target generator of sighting instrument
Han Jun, Shi Yongdong, Chen Wenjian, Yang Jianli, Hu Fei
2016, 37(5): 663-667. doi: 10.5768/JAO201637.0501005
According to the requirements of design specifications for standard dynamic target generator of space,we improved the Cassegrain RC system,namely joining a hyperboloidal mirror between the second lens and image plane. The optical system can collimate the output from liquid crystal light valve in 0.4 μm~0.7 μm and 8 μm~12 μm,and enable an image system to be tested out of 1° field of view. The effective focal length is 1 600 mm and the relative effective aperture is F/1.2 .The result indicates that the diffuse plaque rootmeansquare(RMS) is less than 0.5,the modulation transfer function (MTF)of the coaxial threemirror system values is always greater than 0.7,and close to the diffraction limit at the corresponding spatial frequency of visible and farinfrared band,hence the coaxial threemirror system meets the requirements of image quality.
Design of LED lens based on TIR structure for line-shaped regions
Han Min, Ye Zhengnan, Kang Lianjie, Ju Rongbing, Liu Yan, Ding Guilin
2016, 37(5): 668-672. doi: 10.5768/JAO201637.0501006
We proposed a high-efficient method for the design of the LED lens generating the required irradiance distribution in a rectangular area with a large aspect ratio which was named division-design method:the part of total-internal-reflection(TIR) was designed based on Snell’s law and edge-ray principle,and calculated by iterative integral method,besides,the Matlab programming method was used for its 2D contour;the part of transmission was designed based on the trial and error method; then the two parts were integrated together into a novel arch lens by SolidWorks with the size of 25 mm×18 mm×10 mm. The simulation and experiment results show that the efficiency of the light system is up to 85% while the lens matches with the LED extended source, and the beam angle is about 9°×135° wide at the position of halfvalue of the peak light intensity which means generating the uniform irradiance distribution in a rectangular area with an aspect ratio larger than 15 .
OE Information Acquisition and Processing
Tricolor acquisition and true color images fusion method under low illumination condition
Wu Haibing, Tao Shengxiang, Zhang Liang, Zhang Jing
2016, 37(5): 673-679. doi: 10.5768/JAO201637.0502001
In order to solve the problem of color imaging for low light level(LLL) mainly fused by LLL visible images, infrared images,ultraviolet images and other band images,and actually the fused color images are false color images which cannot reflect the color of object itself,a noval tricolor images acquisted and true color image fusion method was proposed based on filter filtering and image intensifier enhancing.The three primary colors filter was designed by using FebryPerot (FP) filter, and the spectrum transmittance was analyzed.By rotating tricolor wheel filter, the reflected light of the object was separated and then amplified through using a domestic ultra II image intensifier .By means of the fieldprogrammable gate array (FPGA) control program,the precise synchronization of the tricolor wheel filter rotation speed and the charge coupled device (CCD) camera exposure time was achieved ,the CCD camera was adopted to capture the amplified images on image intensifier,and finally the goal for dynamic acquisition of the tricolor images was got . The true color imaging experiments were carried out by prototype system in LLL laboratory,the experimental illumination was 1×10-1 lx (equivalent to moonlight) and 1×10-3 lx(equivalent to startlight),and the tricolor wheel filter rotation speed was set to be 60 f/s ,furthermore,a set of images were adopted to conduct quality assessment.Experiment results show that when the illumination is 1×10-1 lx,compared with the average value of 3 monochrome images,the gray mean value,gray variance and information entropy of fused true color image is increased by 5.06%,5.97% and 1.08%,respectively;and when the illumination is 1×10-3 lx,the gray mean value,gray variance and information entropy of fused true color image is increased by 13.18%,-9.86% and 8.65%,respectively.
Pose measurement of target based on monocular vision and circle structured light
Chen Zhikun, Xu Ao, Wang Fubin, Wang Yi
2016, 37(5): 680-685. doi: 10.5768/JAO201637.0502002
In order to solve the problem that the settled features cannot be set on the target’s surface to achieve pose measurement of target with monocular vision system, the circle structured light was mounted to the monocular vision system. By establishing the visual pose measurement model based on circle stuctured light, a new target’s pose measurement method based on monocular vision and circle structured light was proposed. Firstly, the mathematical parameters of structured light stripe projection on target’s surface in different poses were obtained by image processing. And the parameters were input to the pose measurement algorithm. Then the normal vectors of structured light stripe projection on the target’s face were obtained. Finally, the only solution was determined by the distance constraint relationship between the referential point of target’s surface and the structured light strip center. Experimental results show that this method is effective and feasible,and the average errors are less than 0.5°. This method is more convenient for engineering applications, for example, the robot grasping.
Method and implementation of robot measurement based on visual tracking
Liu Jie, Ping Xueliang, Qi Fi, Jiang Yi
2016, 37(5): 686-692. doi: 10.5768/JAO201637.0502003
In order to calibrate the selfdeveloped industrial robot and improve its movement accuracy, a robot calibration method of dynamic tracking spherical target number by binocular vision was put forward. First we carried out the arbitrary position and orientation measurements in the workspace by markedtargets set on the sphere surface installed on the robotend, which was distinguished and numbered by the particular arrangement and distribution, then accurately identified the geometry parameters of the robot by a leastsquare iterative and compensated them to controller.We established the calibration software including vision measurement, data processing, robot control and other modules by using MFC based on open, modular ideology, finally verified its reliability and accuracy by measuring examples and comparative experiments. Experimental results show that the pose data measured by the software is precise, expanding the field of view of traditional visual tracking; and the identified actual geometry parameters can be compensated, successfully improving the robot positioning accuracy from 3.785 mm to 1.618 mm, as well as the orientation accuracy from 0.235 to 0.139.
Optical encryption method based on joint Fresnel transform correlator and vector decomposition
Dou Shuaifeng, Lei Ming, Shen Xueju, Lin Chao
2016, 37(5): 693-699. doi: 10.5768/JAO201637.0502004
To improve the security of optical image encryption system, a nonlinear optical image encryption system based on doubleopticalwedge joint Fresnel transform correlator and vector decomposition was proposed. The original image was decomposed into two phase masks. One of them, f1(x), was located at the reference window to realize the image encryption; the wave containing the information of the other phase mask, f2(x), interferenced with the decrypted output wave containing the information of the mask f1(x) to obtain the decrypted image. The encryption and decryption processes were numerically simulated. For both grayscale and binary images, the correlation coefficient between the decrypted and original image is 0.812 7 and 0.810 9, respectively, when the wedge angle is 1.8° and the distance between the centers of the mask f1(x) and the key code k(x) is 18 mm. The feasibility of the encryption method was verified by the simulation of the decryption result using incorrect key code with phase distribution error. Analysis results show that the position of the key code k(x) and the wedge angel are proved to be the additional key parameters and can effectively expand the key space. The encryption system is able to defend ciphertextonly attack, knownplaintext attack and chosenplaintext attack.
Influence of different rotating scanning times on photoacoustic tomography
Tan Yi, Li Changhui, Ren Yajie, He Junfeng
2016, 37(5): 700-705. doi: 10.5768/JAO201637.0502005
In order to perform photoacoustic imaging with highcontrast and fast speed, we studied the influence on the reconstructed images of the number of detection positions by a singleelement transducer circularly scanning targets. A Qswitched Nd: YAG laser, operating at 1 064 nm, was used as the illuminating source. The laser has a 7 ns pulse width and a repetition frequency of 20 Hz. A needle polyvinylidene fluoride(PVDF) hydrophone with 1 mm diameter was used to detect photoacoustic signals. We reconstructed the photoacoustic images of 26 letters, 12 hairs, leaf skeleton and simulated blood vessels. Both simulation and experimental results show that an optimized strategy in both imaging quality and speed can be achieved by evenly detecting 100 times around the circle, and the image reconstruction time is 5.903 s. The results of this study would help the performance and design for both scanning singleelement transducer and ring array systems.
Sparse coding based spatial pyramid matching algorithm for image classification
Zhao Song, Feng Xiang
2016, 37(5): 706-711. doi: 10.5768/JAO201637.0502006
Image classification is a hot issue in computer vision field and has been extremely popular in mobile internet applications. A sparse coding based spatial pyramid matching(SCSPM) algorithm was proposed. Firstly, the extracted scaleinvariant feature transform(SIFT) descriptors are encoded by sparse coding method instead of the traditional vector quantization method. The sparse coding step can reduce the quantization errors effectively and generate more discriminative image representation. Furthermore, image classification can be obtained by linear spatial pyramid matching method. The experimental results on Caltech 101, Caltech 256 and 15 Scenes data sets show that our method can significantly improve the image classification accuracy by 4%~12% compared with the bagoffeatwes(BOF) and SPM algorithms.
Optical Metrology and Measurement
Effect of bandpass filter on uncertainty of visibility measurement
Xiao Shaorong, Huang Biao, Huang Xing, Zhou Weiwei
2016, 37(5): 712-718. doi: 10.5768/JAO201637.0503001
In the visibility meter, in order to suppress the impact of uncertainty of measurement by the ambient light changes, the probe beam in optical transmitter was modulated, and the bandpass filter was used in photoelectric signal receiver. Since the frequency response function could change,which was induced by the bandpass filter characteristic parameters changing with the temperature in the working environment, the uncertainty was introduced in the measurement of visibility. Taking a second order active bandpass filter as an example, the band pass filter frequency response amplitude variation with temperature was analyzed from the transfer function, and the the frequency response amplitude variation with temperature was measured by experiment. The results show that the bandpass filter provides about 4.5% uncertainty with the environment temperature changing per 1 ℃, at 15 ℃~40 ℃ in high visibility weather conditions, and the effect of bandpass filter on the measurement of visibility is much smaller in low visibility conditions.
Influence of LED surface characteristics of transmittance meter on visibility measurement
Zhou Shudao, Ma Zhongliang
2016, 37(5): 719-724. doi: 10.5768/JAO201637.0503002
The influence of the source in transmittance meter on the farfield spot of probe beam was analyzed in theory. Combined with the principle of luminescence for LED source,the surface characteristics of LED and the relationship between surface characteristics and measurement of transmittance meter were studied . We proved that the surface characteristics of LED could influence the optical path collimation and the stability of measurement by simulation experiment. The results of the study show that the surface characteristics of LED in transmittance meter can influence the energy distribution of the farfield spot of probe beam and make the center position of probe beam offset 25 mm with the baseline of 50 m, the maximum variation of receiving power is 20%, and hence it can influence the optical path collimation of transmitting terminal and the measurement of the transmittance meter. The energy distribution of the farfield spot can become more uniform and the maximum variation of receiving power is 1% by increasing diffusion chip and aperture.
Application of D-ELM in quantitative analysis of FTIR spectrum of mine gas
Shen Yong, Guo Tiantai, Kong Ming, Zhao Jun, Shen Haidong
2016, 37(5): 725-729. doi: 10.5768/JAO201637.0503003
Three quantitative analysis models for mine gas were established, the support vector machine (SVM) model, the extreme learning machine (ELM) model and the dynamic extreme learning machine (D-ELM) model, to analysis and compare with the result of D-ELM. Since the results of each model were changed in a certain range, taking the average root mean square error (ARMSE), the average correlation coefficient (AR) and the average model running time (AT), all of them were the average values of 10 results of each model, as the standards to evaluate the performance of the model in the quantitative analysis of the mine gas. The results of particle swarm optimization(PSO)-SVM model, ELM model and D-ELM model were as follow: [0.054 2,0.998,200.38], [1.042 1,0.989 4,0.26], [0.043 8,1,2.01]. Considering the predicted accuracy and predicted speed, D-ELM is better than the other two models.
Data acquisition system design of high-precision linear-polarimeter
Gao Xianghua, Hu Yadong, Sun Bin, Hong Jin
2016, 37(5): 730-737. doi: 10.5768/JAO201637.0503004
According to the application requirements of high-precision linear-polarimeter, a signal acquisition system based on capacitive integration method was designed.Firstly,the working principle of the high-precision linear-olarimeter was introduced briefly, as well as its main characteristics, such as large dynamic range of the signal, low sampling frequency and high detection precision. Based on the transimpedance amplification method and the capacitor integral method, two amplification nosie models were established and its SNR formula was derivated.This signal acquisition system,rooting in a DDC112 capacitive integration detector, is capable of reducing the system noise, simplifying the circuit design and improving the system’s flexibility and signaltonoise ratio( SNR). A noise model was also established for the signal acquisition system. At last, laboratory tests were designed to test the dynamic range of the system, equivalent noise radiance, SNR, stability and linear polarization. Field experiments were also carried on. The tests and experiments show that this signal acquisition system has large dynamic range and good equivalent noise radiance. For conventional spectral band of aerosol, the SNR is above 127,for typical spectal band of earth’s surface, the SNR is above 147, the linear polarization measurement accuracy is better than 0.5 % which proves to be a good performance of the signal system.
Transmittance measurement on smog of solid smoke agent in several wavebands
Chen Wenjian, Mu Rangxiu, Zhang Ruofan, Gao Wei, Duan Yuanyuan, Zhang Jia, Zhang Xiangdong
2016, 37(5): 738-741. doi: 10.5768/JAO201637.0503005
In order to obtain attenuation data of several wavebands permeating smog of solid smoke agent,the smog transmittances of 3 smoke agents in 0.4 μm~1 μm visible light waveband,1.06 μm laser wavelength,10.6 μm laser wavelength and 8 μm~14 μm far-infrared waveband were tested by the aid of a smokebox,through which we got the mass extinction coefficients of 3 kinds of interference agent smog in several specified wavebands, and acquired 3 groups of transmittance curves in 4 kinds of wavebands permeating different smog densities with different interference smoke agents. The tested data indicates that the transmittance of 10.6 μm laser is twice as much as that of the 1.06 μm laser in the condition of 4.8 m smog passage and the smog density of smoke agent less than 1.094 7 g/m3 ; And the infrared camera functions are much better than the silicon charge coulped device( CCD) camera.
Optical Element and Fabrication
Design of large FOV projection lens based on ZEMAX
Hou Guozhu, Lyu Lijun, Cao Yiqing
2016, 37(5): 742-746. doi: 10.5768/JAO201637.0505001
For the problem about the design of large fieldofview(FOV) projection lens,a projection lens with large FOV was designed with ZEMAX through limiting the basic parameters and dimensions of the lens by various operating parameters. The optimization process was carried on by using lens frame. The main optical parameters are such that the focal length is 13.6 mm,the full FOV is 60°,the relative aperture is 1/1.6. From the result we can see that the absolute value of maximum distortion of full field lens is less than 3%,the maximum field curve is less than 0.06 mm,the modulation transfer function( MTF) of the whole FOV at 50 lp/mm is greater than 0.6,which is very closed to diffraction limit. The designed optical system is composed of 10 pieces of spherical lenses and has the advantages of compact structure and easy processing.
Optimization design of partially compensating lens for large aperture convex aspheric surface testing
Meng Xiaochen, Zhu Lianqing
2016, 37(5): 747-751. doi: 10.5768/JAO201637.0505002
Optimization design of partially compensating lens is one of the key problems for large aperture convex aspheric surface testing using partcompensating lens and subaperture stitching. A design method for the partcompensating lens based on ZEMAX was proposed, which took the slope of wavefront as the optimization objective, and optimized the lights on the full aperture by observing the radius of dispersive spot. The results indicate that, the large aperture convex aspheric surface can be tested by a simple single partcompensating lens. In different areas of the sub aperture, the maximum radius of the dispersive spot in the ideal focal plane is less than 165 μm, which can always achieve the requirement, verifing the feasibility of testing the large aperture convex aspheric surface by partcompensating lens and subaperture stitching.
Design of 30 nm~110 mm zoom infrared thermal imaging system with large aperture
Zeng Zhenhuang, Lin Feng
2016, 37(5): 752-758. doi: 10.5768/JAO201637.0505003
Zoom system can quickly find and search for the target in a wide range,while more detailed information of the object can be observed in a small range of view.Therefore the application and demand of infrared zoom system in defense, industrial, military and other fields have been growing.We introduced the theory and methods for designing continuous zoom lens,and completed the design of a continuous zoom infrared lens with focal length range of 30mm~110mm, working wavelength of 8 μm~12 μm and F number of 1.0,which was used in conjunction with a 320×240 pixel uncooled detector with the pixel size of 25 μm×25 μm.The total length of the optical system is less than 230 mm, the entire system consists of 7 lenses, and only uses the germanium material, all surfaces are spherical. Finally,we conducted the tolerance analysis the infrared zoom system, and obtained a set of loose machining tolerance.The results show that in the short focus of 30 mm, the modulation transfer function (MTF) value of system is greater than 0.3 at 20 lp/mm,while it is greater than 0.317 4 at 20 lp/mm in the long focus of 110 mm.
Design of multiband terahertz filter
Mi Yang, Wu Qiannan, Yan Shinong
2016, 37(5): 759-764. doi: 10.5768/JAO201637.0505004
Based on the different resonant responses to the electromagnetic fields produced by different sizes of square closed-ring resonator (CRR),a terahertz(THz) multiband filter comprised of 6 CRRs was proposed. By utilizing the finite-difference time-domain method (FDTD),the transmission characteristic of the filter was studied.It is found that the filter can produce six-band filtering performance when the electromagnetic(EM) wave is incident to the plane of the resonant ring normally or obliquely, and the filtering performance of the THz filter is independent to the variation of the incident angle of EM wave due to the symmetry of square closed-ring resonator. This design increases the number of the filtering band so as to improve the frequency sensitivity. The proposed method can provide a theoretical tool to perform multiple angles sensors, THz communication technologies and so on.
Laser Technology
Wind retrieval of airborne fiber Doppler wind lidar and experimental verification
Li Zhigang, Sun Zezhong, Zhao Zengliang, Zhu Xiaopeng, Zhu Jinshan
2016, 37(5): 765-771. doi: 10.5768/JAO201637.0507001
Through the analysis of measurement characteristics for a 1 550 nm allfiber airborne doppler wind lidar, the ways of the velocity correction of plane and the exact wind retrieval algorithms were presented, also a software was completed for the derivation and display of the 3dimension wind field for airborne Doppler lidar. A comparsion experiment between the airborne doppler lidar and sounding balloons was conducted. By the results statistics of 4 airborne campaigns, the bias of wind speed and wind direction is below 1.4 m/s and 10° respectively, and the correlation coefficients of wind speed and wind direction are all higer than 0.95. The performance of the lidar system and the accuracy of wind retrieval algorithms are validated by the experimental results.
Study on multi-wavelength laser attenuation influenced by missile tail smoke
Chen Wenjian, Zhang Ruofan, Chen Shengshi, Duan Yuanyuan, Ma Shiwei, Zhang Xiangdong
2016, 37(5): 772-775. doi: 10.5768/JAO201637.0507002
In order to study the degree of discrepancy for 1.06 μm/3.5 μm/10.6 μm threewavelength laser attenuation due to the missile tail smoke, we established the opening smoke channel test platform. The shrink ratio engines filled up by 3 different kinds of propellant were planted at the head of the smoke channel, and the plume were formed while engines worked. The multiwavelength laser emitter and receiver were placed by the side of smoke channel along the diameter direction, so as to obtain the multiwavelength laser transmittance . The results show that the laser attenuation effected by smoke was related to the particle radius of smoke, and in the 400 m smoke channel environment, the maxim transmittance of 10.6 μm laser is 104 higher than that of 1.06 μm laser. These results are benefit to the improvement and upgrading of laser guiding weapon system.
Influence of aperture diffraction on power distribution of echo wave in cat-eye system
Li Xiaoying, Niu Chunhui, Lyu Yong, Lang Xiaoping
2016, 37(5): 776-782. doi: 10.5768/JAO201637.0507003
The power distribution of the echo wave is a key parameter for cateye detecting system and is usually affected by the aperture diffraction. The field distribution function of the cateye echo wave was derived according to the Collins formula and numerically calculated. The impacts of the caliber and focus length of imaging lens ,the detection distance, the beam waist and the defocusing amount on the power distribution of cat-eye echo wave were investigated. Moreover,a charge coupled device (CCD) based experimental system was set up to observe the power distribution of cateye echo wave and the diffraction pattern. The experiment results indicate that, the optic field of the echo wave carries obvious diffraction information;when the detector locates away from the focus plane of the imaging lens, within a limit detecting distance, the peak power of the cat-eye echo firstly increases and then decreases as the detecting distance increases, the maximum power emerges at about 100 cm. The observing result agrees well with the theoretical analysis,validating that the aperture diffraction can have a significant influence on the power distribution of echo wave. The investigation can provide an instruction for building a cat-eye based detecting system.