2015
2015
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Record 217 of
Title:Research of wind loading on optical window for airborne optoelectronic equipment based on CFD
Author(s):Deng, Xiaoguo(1); Yang, Xiaoxu(1); Li, Gang(1); Zheng, Xiaoqiang(1,2)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 9449 Issue: DOI: 10.1117/12.2076597 Published: 2015Abstract:In order to improve the reliability and working performance of the optical window for airborne optoelectronic equipment, we conduct the aerodynamic analysis of airborne optoelectronic equipment under different flight speed, and get the aerodynamic load distribution of optical window under three different typical flight speed. By building the model of the optical window and simulating the model with the method of CFD, the deformation and stress caused by aerodynamic loading under different thickness of the optical window have been got. The results shows that the thickness of the optical window at 10mm could best meet the requirements of structural strength and quality. Then we analysis the impact of the deformation of the optical window on the imaging quality of the optical system. The deformation of the optical window is very tiny, and it is deformed from the flat into a spherical whose radius is very large. The MTF of the optical system after deformation are basically the same as its MTF before deformation. Thus, the impact of the deformation of the optical window on the imaging quality of the optical system can be ignored. The results of the analysis provide important reference for the design of the optical window for airborne optoelectronic equipment. ? 2015 SPIE.Accession Number: 20151100635581 -
Record 218 of
Title:A deep structure for human pose estimation
Author(s):Zhao, Lin(1); Gao, Xinbo(1); Tao, Dacheng(2); Li, Xuelong(3)Source: Signal Processing Volume: 108 Issue: DOI: 10.1016/j.sigpro.2014.07.031 Published: March 2015Abstract:Articulated human pose estimation in unconstrained conditions is a great challenge. We propose a deep structure that represents a human body in different granularity from coarse-to-fine for better detecting parts and describing spatial constrains between different parts. Typical approaches for this problem just utilize a single level structure, which is difficult to capture various body appearances and hard to model high-order part dependencies. In this paper, we build a three layer Markov network to model the body structure that separates the whole body to poselets (combined parts) then to parts representing joints. Parts at different levels are connected through a parent-child relationship to represent high-order spatial relationships. Unlike other multi-layer models, our approach explores more reasonable granularity for part detection and sophisticatedly designs part connections to model body configurations more effectively. Moreover, each part in our model contains different types so as to capture a wide range of pose modes. And our model is a tree structure, which can be trained jointly and favors exact inference. Extensive experimental results on two challenging datasets show the performance of our model improving or being on-par with state-of-the-art approaches. ? 2014 Elsevier B.V.Accession Number: 20144300114803 -
Record 219 of
Title:Influence of earth's reflective radiation on space target for space based imaging
Author(s):Yan, Pei-Pei(1,2); Ma, Cai-Wen(1); She, Wen-Ji(1)Source: Wuli Xuebao/Acta Physica Sinica Volume: 64 Issue: 16 DOI: 10.7498/aps.64.169501 Published: August 20, 2015Abstract:The space-based surveillance, which would mainly use the space-based visible, has great value for civil and military applications currently and for a fairly long future period. In space-based surveillance, the visible and near-infrared radiation characteristics of the space target are influenced by its attitude variation. This influence is especially prominent in space-based imaging. In some ways, solar radiation cannot arrive at the surface of the space target, or the arriving radiation is not uniformly distributed because of the space target's strong reflection at a particular position. In order to solve these problems, the visible and near-infrared illumination characteristics of the space target surface are analyzed. Moreover, a notion that earth's reflective radiation can be used as illumination for space target imaging is given, and an accurate modeling method is proposed. Firstly, based on diffuse reflectance model, a method of mathematically calculating the illumination at space target's position from earth's reflective radiation is established. And a formula for calculating illumination is derived. Secondly, the coordinates of sun and space target at any time can be obtained by the Satellite tool kit software, in which the complicated multiplying matrix and coordinate transformation algorithm introduced in some references are avoided. Thirdly, the method of estimating earth's reflective radiation region at arbitrary moment is introduced. The grid division method is generated and the uniform sampling is used in each small area. Fourthly, the position of a surface cell is transformed from the sphere reference frame into the J2000.0 inertial frame. The earth's reflective radiation can be calculated through numerical integration. Finally, the illumination from earth's reflective radiation to a sun synchronous orbit satellite in an imaging mission based on space is calculated by the given parameters. The results show that the earth's reflective radiation is luminous enough for space target imaging when the satellite passes through arctic. When the satellite moves on the orbit, we can obtain more detailed information about target satellites' bottom then the ground simulation imaging. The on-orbit imaging results demonstrate the validity of the modeling method, which could support the foundation of our space-based surveillance system theoretically and technically and could be used as a reference of space-based orbit measurement and determination in deep space exploration. ?, 2015, Chinese Physical Society. All right reserved.Accession Number: 20153801290097 -
Record 220 of
Title:Device-free mobile target tracking using passive tags
Author(s):Ding, Han(1); Xi, Min(1); Li, Zhe(2); Zhao, Jizhong(3)Source: International Journal of Distributed Sensor Networks Volume: 2015 Issue: DOI: 10.1155/2015/870204 Published: 2015Abstract:We propose a low-cost device-free mobile target tracking system using passive tags, namely, DTrack, to detect and track a human object in a certain surveillance area. The idea is that when a human object moves, he may block or reflect the RF signals between the reader and tags. Based on the estimation of Doppler Shift and Tag Read Rate variations, DTrack can detect whether a human object enters in the system and further track the moving direction of the object. DTrack uses commercial readers and off-the-shelf passive tags and is scalable and easy for large-scale deployments. Experimental results show that our system is effective in detecting the direction of moving human objects with high accuracy. ? 2015 Han Ding et al.Accession Number: 20154701590934 -
Record 221 of
Title:High-precision positioning system of four-quadrant detector based on the database query
Author(s):Zhang, Xin(1); Deng, Xiao-Guo(1); Su, Xiu-Qin(1); Zheng, Xiao-Qiang(1,2)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 9449 Issue: DOI: 10.1117/12.2075695 Published: 2015Abstract:The fine pointing mechanism of the Acquisition, Pointing and Tracking (APT) system in free space laser communication usually use four-quadrant detector (QD) to point and track the laser beam accurately. The positioning precision of QD is one of the key factors of the pointing accuracy to APT system. A positioning system is designed based on FPGA and DSP in this paper, which can realize the sampling of AD, the positioning algorithm and the control of the fast swing mirror. We analyze the positioning error of facular center calculated by universal algorithm when the facular energy obeys Gauss distribution from the working principle of QD. A database is built by calculation and simulation with MatLab software, in which the facular center calculated by universal algorithm is corresponded with the facular center of Gaussian beam, and the database is stored in two pieces of E2PROM as the external memory of DSP. The facular center of Gaussian beam is inquiry in the database on the basis of the facular center calculated by universal algorithm in DSP. The experiment results show that the positioning accuracy of the high-precision positioning system is much better than the positioning accuracy calculated by universal algorithm. ? 2015 SPIE.Accession Number: 20151100635592 -
Record 222 of
Title:Thermal/structural/optical integrated design for optical window of a high-speed aerial optical camera
Author(s):Zhang, Gaopeng(1); Yang, Hongtao(1,2); Mei, Chao(1); Shi, Kui(1); Wu, Dengshan(1); Qiao, Mingrui(1,2)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 9676 Issue: DOI: 10.1117/12.2199812 Published: 2015Abstract:In order to obtain high quality image of the aero optical remote sensor, it is important to analysis its thermal-optical performance on the condition of high speed and high altitude. Especially for the key imaging assembly, such as optical window, the temperature variation and temperature gradient can result in defocus and aberrations in optical system, which will lead to the poor quality image. In order to improve the optical performance of a high speed aerial camera optical window, the thermal/structural/optical integrated design method is developed. Firstly, the flight environment of optical window is analyzed. Based on the theory of aerodynamics and heat transfer, the convection heat transfer coefficient is calculated. The temperature distributing of optical window is simulated by the finite element analysis software. The maximum difference in temperature of the inside and outside of optical window is obtained. Then the deformation of optical window under the boundary condition of the maximum difference in temperature is calculated. The optical window surface deformation is fitted in Zernike polynomial as the interface, the calculated Zernike fitting coefficients is brought in and analyzed by CodeV Optical Software. At last, the transfer function diagrams of the optical system on temperature field are comparatively analyzed. By comparing and analyzing the result, it can be obtained that the optical path difference caused by thermal deformation of the optical window is 149.6 nm, which is under PV ≤1 4λ.The simulation result meets the requirements of optical design very well. The above study can be used as an important reference for other optical window designs. ? 2015 SPIE.Accession Number: 20155201717481 -
Record 223 of
Title:Research on the error model of airborne celestial/inertial integrated navigation system
Author(s):Zheng, Xiaoqiang(1); Deng, Xiaoguo(1); Yang, Xiaoxu(1); Dong, Qiang(2)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 9449 Issue: DOI: 10.1117/12.2075874 Published: 2015Abstract:Celestial navigation subsystem of airborne celestial/inertial integrated navigation system periodically correct the positioning error and heading drift of the inertial navigation system, by which the inertial navigation system can greatly improve the accuracy of long-endurance navigation. Thus the navigation accuracy of airborne celestial navigation subsystem directly decides the accuracy of the integrated navigation system if it works for long time. By building the mathematical model of the airborne celestial navigation system based on the inertial navigation system, using the method of linear coordinate transformation, we establish the error transfer equation for the positioning algorithm of airborne celestial system. Based on these we built the positioning error model of the celestial navigation. And then, based on the positioning error model we analyze and simulate the positioning error which are caused by the error of the star tracking platform with the MATLAB software. Finally, the positioning error model is verified by the information of the star obtained from the optical measurement device in range and the device whose location are known. The analysis and simulation results show that the level accuracy and north accuracy of tracking platform are important factors that limit airborne celestial navigation systems to improve the positioning accuracy, and the positioning error have an approximate linear relationship with the level error and north error of tracking platform. The error of the verification results are in 1000m, which shows that the model is correct.. ? 2015 SPIE.Accession Number: 20151100635511 -
Record 224 of
Title:Enhancing visibility of hazy images based on the estimation of the polarization value
Author(s):Shen, Dan(1); Yang, Fanchao(1)Source: Proceedings of 6th International Conference on Intelligent Control and Information Processing, ICICIP 2015 Volume: Issue: DOI: 10.1109/ICICIP.2015.7388228 Published: January 20, 2016Abstract:This paper introduces an algorithm based on the estimation of the polarization value. There is a physical model introduced and applied in this algorithm. One of the necessary polarization value is calculated and the other is estimated. The final result image is good. ? 2015 IEEE.Accession Number: 20161702290796 -
Record 225 of
Title:Magneto-optical modulation measurement method of glass internal stress
Author(s):Li, Chunyan(1,2); Wu, Yiming(1); Gao, Limin(1); Lu, Weiguo(1)Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 44 Issue: 3 DOI: Published: March 25, 2015Abstract:In order to achieve the high-precision measurement of glass internal stress, a new method of magneto-optical modulation was proposed, and the system of internal stress measurement based on the magneto-optical modulation was established. First, measurement model of the system was derived according to the Mueller matrix description method of polarized light, by using separation of the direct current, fundamental frequency and the second harmonic component of detected signals, and "normalized" approach, the impact of the light source intensity fluctuation on the measurement result was eliminated. The direction of glass internal stress and the size of stress birefringence values were received by processing the respective signal components. By measuring the glass at different positions, the validity of the method is verified, and the measurement accuracy of internal stress direction is 5″, the measurement accuracy of stress birefringence value is below 0.5 nm/cm. This system has high stability and high accuracy. ?, 2015, Chinese Society of Astronautics. All right reserved.Accession Number: 20151800813118 -
Record 226 of
Title:Tunable photonic nanojet formed by generalized Luneburg lens
Author(s):Mao, Xiurun(1); Yang, Yang(2); Dai, Haitao(1); Luo, Dan(3); Yao, Baoli(4); Yan, Shaohui(4)Source: Optics Express Volume: 23 Issue: 20 DOI: 10.1364/OE.23.026426 Published: October 5, 2015Abstract:Nanojet has been emerging as an interesting topic in variety photonics applications. In this paper, inspired by the properties of generalized Luneburg lens (GLLs), a two-dimensional photonic nanojet system has been developed, which focal distance can be tuned by engineering the refractive index profile of GLLs. Simulation and analysis results show that the maximum light intensity, transverse and longitudinal dimensions of the photonic nanojet are dependent on the focal distance of the GLLs, thereby, by simply varying the focal distance, it is possible to obtain localized photon fluxes with different power characteristics and spatial dimensions. This can be of interest for many promising applications, such as high-resolution optical detection, optical manipulation, technology of direct-write nano-patterning and nano-lithography. ? 2015 Optical Society of America ? 2015 OSA.Accession Number: 20154201387533 -
Record 227 of
Title:Gimbals periodic error suppression based on fiber optic gyroscope
Author(s):Yang, Yongqing(1,2); Liang, Yanbin(1,2); Li, Zhiguo(1,2); Liang, Dongsheng(1,2)Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 44 Issue: 6 DOI: Published: June 25, 2015Abstract:In order to suppress the periodic angle measuring error's fluctuation on gimbals and the imaging effect of photoelectric tracking, a measuring error model and an error control algorithm were established. Firstly, the mechanism of the measurement error of angular measuring system was analyzed, and a mathematical model for the periodic error was established in this paper. Secondly, a measuring error acquisition system based on the high precision fiber optic gyroscope and Fourier was established, and a specific expression of angle measurement error model was established through seven experimental procedures. Then, the periodic system error was compensated according to the measured angle error expressions through four steps. Finally, the effectiveness of control compensation was verified by tracking imaging experiments, and the experimental results show that speed error is reduced to 0.04 (°)/s, is reduced 8 times. The error meets the requirement of the imaging system less than 0.1 (°)/s, and the stripe imaging effect is greatly improved. ?, 2015, Chinese Society of Astronautics. All right reserved.Accession Number: 20153501219872 -
Record 228 of
Title:Design and verification of focal plane assembly thermal control system of one space-based astronomy telescope
Author(s):Yang, Wen-Gang(1,2); Fan, Xue-Wu(1); Wang, Chen-Jie(1); Wang, Ying-Hao(1,2); Feng, Liang-Jie(1); Du, Yun-Fei(1); Ren, Guo-Rui(1,2); Wang, Wei(1); Li, Chuang(1); Gao, Wei(1)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 9678 Issue: DOI: 10.1117/12.2199517 Published: 2015Abstract:One space-based astronomy telescope will observe astronomy objects whose brightness should be lower than 23th magnitude. To ensure the telescope performance, very low system noise requirements need extreme low CCD operating temperature (lower than -65°C). Because the satellite will be launched in a low earth orbit, inevitable space external heat fluxes will result in a high radiator sink temperature (higher than -65°C). On ly passive measures can't meet the focal plane cooling specification and act ive cooling technologies must be utilized. Based on detailed analysis on thermal environment of the telescope and thermal characteristics of focal plane assembly (FPA), act ive cooling system which is based on thermo-electric cooler (TEC) and heat rejection system (HRS) which is based on flexible heat pipe and radiator have been designed. Power consumption of TECs is dependent on the heat pumped requirements and its hot side temperature. Heat rejection capability of HRS is mainly dependent on the radiator size and temperature. To compromise TEC power consumption and the radiator size requirement, thermal design of FPA must be optimized. Parasit ic heat loads on the detector is minimized to reduce the heat pumped demands of TECs and its power consumption. Thermal resistance of heat rejection system is minimized to reject the heat dissipation of TECs from the hot side to the radiator efficiently. The size and surface coating of radiator are optimized to compromise heat reject ion requirements and system constraints. Based on above work, transient thermal analysis of FPA is performed. FPA prototype model has been developed and thermal vacuum/balance test has been accomplished. From the test, temperature of key parts and working parameters of TECs in extreme cases have been acquired. Test results show that CCD can be controlled below -65°C and all parts worked well during the test. All of these verified the thermal design of FPA and some lessons will be presented in this paper. ? 2015 SPIE.Accession Number: 20161602271452