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Record 97 of
Title:Design and experiment of momentum balance wheels for optoelectric tracking gimbals
Author(s):Li, Zhi-Guo(1,2); Gao, Li-Min(1); Zhang, Bo-Ni(3); Cui, Kai(2); Wang, Zhen-Yu(1)
Source: Guangxue Jingmi Gongcheng/Optics and Precision Engineering Volume: 21 Issue: 1 DOI: 10.3788/OPE.20132101.0062 Published: January 2013
Abstract:A balance wheel to offset output torques and momentums of the gimbals during working was researched to eliminate the influence of movement of an optoelectronic tracking system on the satellite attitude. The balance wheels used in gimbals based on satellites are characterized by starting frequently, changing extensively in velocity and acceleration, and passing zero of velocity, which are quite different from that used to control satellite attitude. Therefore, a new balance wheel was designed based on angular momentum balance principle to meet the requirements of optoelectronic tracking gimbals for acquiring and tracking targets. The model and structure of the balance wheel were analyzed and optimized by finite element methods. Then an electromechanical dynamic model for describing the dynamic characteristics of optoelectronic tracking gimbals with the balance wheels was established, and the simulation for an azimuth rotor was researched by Matlab/Simulink and the reasonable results were presented. To verify the feasibility, a model prototype was developed. Then the experiment method based on an air bearing table was presented and the residual angular momentum was tested. Analysis and test results show that the residual angular momentum has reduced by 96%. The research verifies that the balance wheel can satisfy the application requirements of satellites.
Accession Number: 20130916060636
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Record 98 of
Title:Stray light analysis of catadioptric infrared optical system with large field
Author(s):Wang, Wenfang(1,2); Yang, Xiaoxu(1); Jiang, Kai(1,2); Mei, Chao(1,2); Li, Gang(1); Zhang, Hengjin(1)
Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 42 Issue: 1 DOI: Published: January 2013
Abstract:Stray light analysis in optical system is a key technology to ensure the system's quality. According to the definition of stray light, the sources of stray light in infrared optical system and the effect of stray light were pointed out in this paper. In view of stray light source, a structure of suppressing stray light was established. In order to reduce the internal radiation, reflective vanes were used. TracePro software was also used to build the system model and simulate analysis of the system. The results indicate that stray light is well suppressed, and the system's PST can achieve a level of 10-5-10-8. At the same time, the internal radiation energy that gets to imager can achieve a level of 10-10 W. So the system can achieve a clear image.
Accession Number: 20131316153574
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Record 99 of
Title:Harmonic diffractive optical element wave crest drift with incident angles
Author(s):Yu, Deng-Qun(1,2); Cao, Jian-Zhong(1); Yan, A-Qi(1); Zhang, Jian(1); Qu, En-Shi(1); Wang, Feng(1,2)
Source: Guangzi Xuebao/Acta Photonica Sinica Volume: 42 Issue: 10 DOI: 10.3788/gzxb20134210.1208 Published: October 2013
Abstract:According to phase shift method of binary optics, the phase delay expression and the diffraction efficiency of Harmonic Diffractive Optical Element (HDOE) at oblique incidence were derived. And the relationship between the diffraction efficiency and the beam incident angle was qualitatively analyzed. The results show that in the visible spectral range, resonant wavelength of HDOE becomes longer with incidence angle increasing, otherwise in the short-wave part wave crest drift more violently; with incident angle of monochromatic light increasing, the diffraction order sequence appears; with the incidence angle increasing, the wave crest of ordinary binary element drift much faster than HDOE; beam incidence angle has a greater impact on diffraction efficiency of short wave.
Accession Number: 20135117103923
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Record 100 of
Title:Optimized H.264 motion estimation algorithm based on UMHexagonS
Author(s):Chen, Liu(1,2); Cao, Jian-Zhong(1); Tang, Li-Nao(1); Huang, Ji-Jiang(1); Guo, Hui-Nan(1,2); Dong, Xiao-Kun(1,2)
Source: Proceedings of the 2013 International Conference on Intelligent Control and Information Processing, ICICIP 2013 Volume: Issue: DOI: 10.1109/ICICIP.2013.6568063 Published: 2013
Abstract:H.264 has adoptedUMHexagonS algorithm as fast motion estimation algorithm for integer pixel formally, but this algorithm has some shortages such as searchpointsare lots, quantity of operation is kind of big, costs much time, and so on. These need to be solved as soon as possible. This paper introduces and analyses UMHexagonS algorithm. In order to solve these problems, this paper brings forwardclassification strategy for search algorithm according to statistical properties of the motion vector prediction value, and improvesthe template basedon original algorithm according to the characteristic of center bias of motion vector. The results of experimentsshow that the improved algorithm in this paper reduces the time of motion estimation by 15%～27%. At the meantime, it can ensure PSNR and rate basically unchanged. ? 2013 IEEE.
Accession Number: 20133616702277
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Record 101 of
Title:An enhanced infrared and visible image fusion method based on wavelet transform
Author(s):Xu, Fan(1,2); Su, Xiuqin(1)
Source: Proceedings - 2013 5th International Conference on Intelligent Human-Machine Systems and Cybernetics, IHMSC 2013 Volume: 2 Issue: DOI: 10.1109/IHMSC.2013.255 Published: 2013
Abstract:In some researches of infrared(IR) and visible image fusion, the IR images often contribute more useful information. However, the IR sensor is sensitive to the temperature of a scene. Therefore, the IR images have low definition and contain much noise which affects the quality of the fused image. In a decomposed image Based on wavelet transform, the contrast of an image is proportional to the relative variation of the gray scale. And with the scale increasing, at least the mean and variance of impulse noise and Gaussian noise linearly decrease. Thus, a novel image fusion method Based on the wavelet transform is proposed in this paper. Firstly, both the IR image and visible image are decomposed by wavelet transform and their multi-scale sub images are achieved. Then, the contrast of IR image is improved by modifying the modulus of the sub images in scale space and stretching the dynamic scope of smooth sub image at coarser resolution level. Finally, the improved IR images and visible images are fused at different scales and reconstructed to the fused image. Experiments are carried out Based on discrete wavelet transform (DWT) and dual tree complex wavelet transform (DTCWT). The results turn out that the enhanced method is effective compared with the original methods. ? 2013 IEEE.
Accession Number: 20140317201777
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Record 102 of
Title:Joint optimization toward effective and efficient image search
Author(s):Wei, Shikui(1,2); Xu, Dong(2); Li, Xuelong(3); Zhao, Yao(4,5)
Source: IEEE Transactions on Cybernetics Volume: 43 Issue: 6 DOI: 10.1109/TCYB.2013.2245890 Published: December 2013
Abstract:The bag-of-words (BoW) model has been known as an effective method for large-scale image search and indexing. Recent work shows that the performance of the model can be further improved by using the embedding method. While different variants of the BoW model and embedding method have been developed, less effort has been made to discover their underlying working mechanism. In this paper, we systematically investigate the image search performance variation with respect to a few factors of the BoW model, and study how to employ the embedding method to further improve the image search performance. Subsequently, we summarize several observations based on the experiments on descriptor matching. To validate these observations in a real image search, we propose an effective and efficient image search scheme, in which the BoW model and embedding method are jointly optimized in terms of effectiveness and efficiency by following these observations. Our comprehensive experiments demonstrate that it is beneficial to employ these observations to develop an image search algorithm, and the proposed image search scheme outperforms state-of-the-art methods in both effectiveness and efficiency. ? 2013 IEEE.
Accession Number: 20135117094996
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Record 103 of
Title:Experiment on two dimensional quadrilateral position sensing detector
Author(s):Zhang, Min(1,2); Liang, Yanbing(1)
Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 42 Issue: 2 DOI: Published: February 2013
Abstract:Position sensing detector (PSD) is an optics sensor that can detect the center of the incident light. It has the advantages of fast response, high position resolution and simple circuit, these characteristics make it a wide range of application in precision measurement such as angle and position detection. A optical experiment on a optic bench A823 was chose for data acquisition under the DOS operating system and Borland C ++ builder, C program was written for a real-time transformation between analog voltage and digital voltage, then position coordinate was calculated and the error was analyzed. 2L10_SU65_SPC02 PSD used in this experiment is from Sitek corporation in Sweden, through the error analysis the main conclusions include fringe effect of PSD, the main influence about the position error are natural daylight and fluorescent light. If eliminate influence factor precision will improve a lot.
Accession Number: 20131616213967
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Record 104 of
Title:Improved design of support for large aperture space lightweight mirror
Author(s):Wang, Chao(1,2); Ruan, Ping(1); Liu, Qimin(1,2)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 8908 Issue: DOI: 10.1117/12.2034456 Published: 2013
Abstract:In order to design a kind of rational large aperture space mirror which can adapt to the space gravity and thermal environment, by taking the choice of material, the lightweight of the mirror and the design of support into account in detail, a double-deck structure with traditional flexible hinge was designed, then the analytical mathematical model of the mirror system was established. The design adopts six supports on back. in order to avoid the constraints, mirror is connected to three middle transition pieces through six flexible hinges, and then the three transition pieces are connected to support plate through another three flexible hinges. However, the initial structure is unable to reach the expected design target and needs to be made further adjustments. By improving and optimizing the original structure, a new type of flexible hinge in the shape of the letter A is designed finally. Compared with the traditional flexible hinge structure, the new structure is simpler and has less influence on the surface figure accuracy of mirror. By using the finite element analysis method, the static and dynamic characteristics as well as the thermal characteristics of the mirror system are analyzed. Analysis results show that the maximum PV value is 37 nm and the maximum RMS value is 10.4 nm when gravity load is applied. Furthermore, the maximum PV value is 46 nm and the maximum RMS value is 10.5 nm under the load case of gravity coupled with 4a.,uniform temperature rise. The results satisfy the index of optical design. The first order natural frequency of the mirror component is 130 Hz according to the conclusion obtained by modal analytical solution, so the mirror structure has high enough fundamental frequency. And, the structural strength can meet the demand under the overload and the random vibration environment respectively. It indicates that the mirror component structure has enough dynamic, static stiffness and thermal stability, meeting the design requirements. ? 2013 SPIE.
Accession Number: 20134216857687
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Record 105 of
Title:Design and analysis of flexible support of the grating in space spectrometer
Author(s):Liu, Qimin(1,2); Ruan, Ping(1); Li, Fu(1); Pan, Haijun(1,2)
Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 42 Issue: 9 DOI: Published: September 2013
Abstract:In order to obtain high-stiffness and good thermal stability of main supporting structure in space remote sensor, a flexible support structure was proposed to solve the contradiction of force and thermal constraints availably, which are two key environmental constraints on the imaging of the grating spectrometer. Firstly, according to the optical design requirements, the structure of the grating blank was determined. Secondly, the sensitivity of the sizes of the flexible support was analyzed by theoretical calculation, and their effects on bend rigidity were obtained. Optimum design was utilized to determine the final sizes. Finally, the surface figure precision and dynamic stiffness of the grating component in the thermal-structural coupling state were analyzed with finite element analysis (FEA) software. Simulation results demonstrate that design of the grating blank and its flexible support structure is reasonable, which can meet the requirements of the space application and supply the reference for further study and application.
Accession Number: 20134817040199
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Record 106 of
Title:An improved image fusion algorithm based on wavelet transform
Author(s):Duan, Zewei(1,2); Wen, Desheng(1); Song, Zongxi(1)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 8907 Issue: DOI: 10.1117/12.2031878 Published: 2013
Abstract:Image fusion takes a significant part in the technology of information enhancement. By analyzing the advantages and disadvantages of previous methods , this paper proposes an improved wavelet-transform-algorithm, which both considers the fusion methods of low-frequency and high-frequency components: On the low-frequency sub-band aspect, introducing a border detector operator in order to collect the border information of images that can be the basis of selective fusion method; On the high-frequency sub-band aspect, applying the local-standard-deviation to being the basis of selective and weighted-averaging fusion method. The experiments reveal that the proposed algorithm contributes to enhancing the definition and contract ratio of the fused images, thereby it's a valid method. ? 2013 Copyright SPIE.
Accession Number: 20141317510098
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Record 107 of
Title:Resolution performance of the extra ultraviolet telescopes
Author(s):Fu, Huai-Yang(1,2); Zhou, Si-Zhong(1); Jiang, Kai(1,2); Mei, Chao(1,2)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 8908 Issue: DOI: 10.1117/12.2032376 Published: 2013
Abstract:The Extreme Ultraviolet Telescopes (EUT) Operates at wavelengths between 100-1000 ?. As an important parameter of the telescope system, before the launch, angular resolution is necessary to be calibrated for testing the imaging performance of EUT. However, the difficulty and expense of fabricating optical testing systems capable of imaging the characteristic EUV wavelengths, has precluded in working wavelength resolution testing. This article taken a Ritchey-Chrétien normal incidence optical system as sample and resolution tests were carried out at visible wavelength. Based on this measurement, the angular resolution error budget at visible wavelength was calculated. At working wavelength, we added the squares of the pointing jitter error, the resolution focusing error and the scattering error, to the theoretical Rayleigh diffraction limit at the wavelength of operation, and then take the square root of this sum, an upper limit estimate of telescope's resolution was obtained about 0.4705 arcsec. This result proved that the EUT worked at diffraction-limited level and the resolution performance has met the demand of design. ? 2013 SPIE.
Accession Number: 20134216857643
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Record 108 of
Title:A new infrared image processing method based on compressed sensing
Author(s):Mu, Chenhao(1,2); Qiu, Yuehong(1); Chen, Zhi(1)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 8907 Issue: DOI: 10.1117/12.2033567 Published: 2013
Abstract:In order to improve the efficiency of processing the large amount of data of infrared image, in this paper we develop a new infrared image processing method based on compressed sensing (CS) and simulate the method. The basic idea behind CS is that a signal or image, unknown but supposed to be compressible by a known transform, (eg. wavelet), can be subjected to fewer measurements than the nominal number of pixels, and yet be accurately reconstructed. According to the properties of wavelet transform sub-bands, firstly we make wavelet transform which change the infrared image into a wavelet coefficients matrix. Acquired the features of infrared image, the characters of the wavelet coefficients can be concluded. When deeply analyzing the data of the wavelet coefficient, we can easily find the high-pass wavelet coefficients of the image are sparse enough to measure, while the low-pass wavelet coefficients are not appropriate for measure. So in this second part, only measured the high-pass wavelet coefficients of the image but preserving the low-pass wavelet coefficients. For the reconstruction, the third part, by using the orthogonal matching pursuit (OMP) algorithm, high-pass wavelet coefficients could be recovered by the measurements. Finally the image could be reconstructed by the inverse wavelet transform. The simulation proves that applying the CS theory to the realm of infrared picture can decrease the amount of data which must be collected. Besides, compared with the original compressed sensing algorithm, simulation results demonstrated that the proposed algorithm improved the quality of the recovered image significantly. ? 2013 Copyright SPIE.
Accession Number: 20141317510175
