2013
2013
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Record 121 of
Title:A deployable telescope imaging system with coilable tensegrity structure for microsatellite application
Author(s):Zhao, Chao(1,2); Li, Chuang(1); Zhou, Nan(1,2)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 8908 Issue: DOI: 10.1117/12.2033266 Published: 2013Abstract:Microsatellites will be widely applied as an earth-observing platform in coming future for their low costs. Such satellite missions require optical payloads with low cost, low mass and small volume. In order to meet these requirements, one way is to develop deployable telescopes. They not only maintain the capabilities of the traditional non-deployable telescopes, but also have compacter launch volume and lighter weight. We investigate a telescope with precise deployable structure based on coilable tensegrity. Before launch, the secondary mirror support structure is coiled, and when the satellite is in orbit, the secondary mirror is deployed with the elastic strain energy from the coiled longerons. There are mainly three parts in this paper. Firstly, the telescope optics is presented. A Ritchey-Chretien (RC) type optical system with 150mm aperture is designed. Secondly, the deployable telescope structure is designed for the RC system. The deployable structure mainly consists of coilable longerons, batten rings, and diagonal stringers. The finite element method (FEM) is used to analyze the dynamics of the unfolded telescope structure. Thirdly, the adjusting mechanism for secondary mirror is discussed. Piezoelectric actuators can be used to achieve remote alignment to improve the performance of the imaging system. ? 2013 SPIE.Accession Number: 20134216857673 -
Record 122 of
Title:Space camera image degradation induced by satellite micro-vibration
Author(s):Wang, Hong-Juan(1,2); Wang, Wei(1); Wang, Xin(1,2); Zou, Gang-Yi(1); Li, Gang(1,2); Fan, Xue-Wu(1)Source: Guangzi Xuebao/Acta Photonica Sinica Volume: 42 Issue: 10 DOI: 10.3788/gzxb20134210.1212 Published: October 2013Abstract:In order to evaluate the space camera image degradation induced by micro-vibration, an integrated modeling was utilized. During the CCD integrated time, the image motion of dynamical imaging system equaled to static image spot blurring, dynamical imaging evaluation criterion was proposed and dynamical imaging was analyzed. All kinds of disturbance sources were introduced, the finite element model (FEM) of space camera was founded, and the jitter values of optical elements were acquired by dynamic analysis with finite element software. The analysis results were imported to optical design software CODE V, the system spot diagram and MTF were attained, and the image motion was calculated quickly. The integrated modeling which shortens the computational quantity effectively suits to any type of micro-vibration. This method was utilized to simulate the space camera image degradation induced by micro-vibration, and the dynamical imaging evaluation criterion was used to estimate the effects on imaging system. The relationship between micro-vibration and image degradation was achieved, that provides important references for system optimum design and vibration isolation.Accession Number: 20135117103924 -
Record 123 of
Title:A correction algorithm on reducing energy excursion phenomenon
Author(s):Wang, Zheng-Jie(1,2); Du, Yun-Fei(1); Hu, Bing-Liang(1); Liu, Lei(1); Kong, Liang(1); Yan, Peng(1); Wu, Qi-Jing(1)Source: Guangzi Xuebao/Acta Photonica Sinica Volume: 42 Issue: 8 DOI: 10.3788/gzxb20134208.0891 Published: August 2013Abstract:The imaging principle and the structure of a Hadamard transform spectral imager with a digital micro-mirror device are presented. A phenomenon of energy excursion which is caused by mismatching of the mask unit size and the detector pixel size is expatiated. To fix the recovery images, a matrix correction algorithm is proposed. The 7-order images of plants acquired by the Hadamard transform spectral imager are used and the correction algorithm is operated on the recovery images with error, which reduces the phenomenon of dark stripes effectively. In order to improve the image quality of the recovery images, two dots in and off two adjacent dark stripes are selected to show the spectrum curves. The results show the close spectrum curves of the dot off dark stripes and the different curves of the dot in dark stripes. The comparison illustrates the validity of the correction algorithm.Accession Number: 20134216860585 -
Record 124 of
Title:Auto-exposure algorithm for scenes with high dynamic range based on image entropy
Author(s):Yang, Zuo-Ting(1,2); Ruan, Ping(1); Zhai, Bo(1)Source: Guangzi Xuebao/Acta Photonica Sinica Volume: 42 Issue: 6 DOI: 10.3788/gzxb20134206.0742 Published: June 2013Abstract:Automatic exposure control is a process of optimizing image brightness by controlling the exposure. To achieve auto exposure in digital cameras, image brightness is widely used because of its direct relationship with exposure value. Although entropy has been used in various image processing applications, it has not been used for AE application. A new auto-exposure algorithm was proposed based on the image entropy. The proposed method calculated the entropy of captured images to estimate lighting conditions. By comparing the image entropy and entropy threshold, the images were divided into the regions of interest and regions of no interest. After that, assign different weights to the regions of interest and regions of no interest, so that the overall brightness level was made to carry more information of the regions of interest. At last, the image can get accurate automatic exposure. The algorithm is mainly based on the image entropy, so the exposures are not affected by the location of objects in the image. It can make the algorithm more flexible. The experiment results show that the algorithm can accurately detect high-contrast lighting conditions and improve the dynamic range of output images for a camera system, at the same time the algorithm can also increases the accuracy of auto exposure.Accession Number: 20132816483962 -
Record 125 of
Title:Wedge-plate shear for focus-shifting testing in single-shot laser system
Author(s):Zhao, Juanning(1,2); Dong, Xiaona(1); Gao, Limin(1); Li, Hongguang(1)Source: Applied Optics Volume: 52 Issue: 18 DOI: 10.1364/AO.52.004237 Published: June 20, 2013Abstract:A method using a wedge-plate shear shifting system with adjustable accuracy and measuring range is proposed for measuring the focus shifting caused by thermal distortion in a single-shot laser system. Two beam splitter groups are used in this method to precisely split a single beam into multiple beams with different optical path difference. The focus shifting is determined by position change of the minimum spot on the detector. This method is convenient and economic, especially as it powerfully solves the problem of catching focus shifting in an ultrashort time. ? 2013 Optical Society of America.Accession Number: 20132916502497 -
Record 126 of
Title:Design of an outer baffle based on scattering model
Author(s):Mei, Chao(1,2); Zhou, Sizhong(1); Yan, Peipei(1); Jiang, Kai(1,2)Source: Guangxue Xuebao/Acta Optica Sinica Volume: 33 Issue: 1 DOI: 10.3788/AOS201333.0122005 Published: January 2013Abstract:By the analysis of the scattering situation of the rough surface, it is found that the ordinary metal material scattering energy is centralized in 10°. Based on the scattering characteristics, the method of the outer baffle design is put forward, the baffle rings' restraint angle is 5° larger than the stray light suppression angle which is calculated based on reflection theory, and the effect of the outer baffle to suppress the stray light is very good. The baffle is designed for a Ritchey-Chirtien (R-C) system and the model is built in the TracePro software for analysis. With the contrast of different models and the designs, the results show that the consideration of the scattering is more accurate, the effect of the outer baffle is better, and the point source transmittance (PST) of the system is lower than others.Accession Number: 20131016077661 -
Record 127 of
Title:Image definition evaluation algorithm based on color relativity
Author(s):Guo, Huinan(1); Cao, Jianzhong(1); Zhou, Zuofeng(1); Tang, Linao(1); Wang, Hua(1); Ma, Nan(2)Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 42 Issue: 11 DOI: Published: November 2013Abstract:Definition evaluation function of digital image plays an important role in digital camera auto-focus. Due to the existing definition evaluation functions are of some marked disadvantages, a spatial domain evaluation algorithm for digital color image was proposed. The colorful property of each pixel was judged and definition chromatic difference parameters was created by using chromatic difference between their tri-stimulus values. Besides, nonlinear function was used to improve the gradient coefficient of each pixel which made the evaluation function be more sensitive to some images in extreme cases. Experimental results show the superiority of our algorithm over the most of existing evaluation algorithms in dealing with natural images. And our method also is of a good ability of robustness as well as reducing calculation complexity and it can be easily achieved on hardware.Accession Number: 20140317209496 -
Record 128 of
Title:Method of first-order ghost-image analysis in imaging system based on Code V and Tracepro
Author(s):Mei, Chao(1,2); Zhou, Sizhong(1); Zhang, Hengjin(1); Duan, Jing(1); Jiang, Kai(1,2)Source: Guangxue Xuebao/Acta Optica Sinica Volume: 33 Issue: 4 DOI: 10.3788/AOS201333.0411003 Published: April 2013Abstract:During optical designing, ghost images of optical system should be avoided, so fast and precise analysis of ghost images appears to be very important. The way of first-order ghost-image analysis of imaging system based on Code V and Tracepro is proposed. The surfaces which can cause serious ghost image are found out. The optical system model is established in Tracepro. The image is separated into several parts. Different parts are setted as different spot sources, then, the spot sources are analyzed one by one. During analysis, the order of the ghost is controlled by threshold and ghost-surface is controlled by the surface property. Through analysis, the position of ghost image, and power distribution of ghost image can be obtained.Accession Number: 20132116362334 -
Record 129 of
Title:Blind equalization algorithm of wireless optical communication using subcarrier modulation over turbulence channel
Author(s):Chen, Dan(1); Ke, Xi-Zheng(1); Li, Jian-Xun(1,2)Source: Guangzi Xuebao/Acta Photonica Sinica Volume: 42 Issue: 9 DOI: 10.3788/gzxb20134209.1025 Published: September 2013Abstract:Blind equalization system model is established with atmospheric turbulence time-varying channel. Under different scintillation distribution conditions, performances of two kinds of adaptive blind equalization algorithms are compared such as convergence, mean square error (MSE) and stability, and clustering in constellation of wireless optical subcarrier signal are analyzed. With the increasing of turbulence intensity, variable step-size constant modulus algorithm (CMA) algorithm based MSE has faster convergence, smaller MSE but poor stability, and scale factor must be decreased to ensure convergence compared with CMA algorithm. Meanwhile, compared with Gaussian channel, under the same signal-to-noise ratio, iterative step length factor and scale factor under the turbulence channel is smaller, but mean square error is bigger than in Gaussian channel. The simulation results show that two kinds of algorithms can effectively improve the convergence of constellation diagram, and have important significance in improving detection rate of constellation diagram.Accession Number: 20134216860607 -
Record 130 of
Title:Precise alignment of separated Sagnac interferometer
Author(s):Zhang, Xuemin(1,2); Wei, Ruyi(1,2); Yan, Su(1); Duan, Jiayou(1); Li, Hua(1); Yang, Jianfeng(1)Source: Zhongguo Jiguang/Chinese Journal of Lasers Volume: 40 Issue: 4 DOI: 10.3788/CJL201340.0416001 Published: April 2013Abstract:A separated Sagnac interferometer with optical diameter of 60 mm and spectral channel of 65 is introduced based on its working principle. Ideal interference fringes and interference fringes are simulated when reflector has an angle deviation, and the effect of alignment error to the interference fringes is analyzed. The position accuracy and angle accuracy of alignment are induced based on the optical design parameters. The method of precision alignment is introduced in detail, which includes the installation of primary alignment plane, the precise location of splitting prism, the precise adjustment of long-arm and short-arm reflectors. Through the installation of alignment refrence and the masterly refrence transformation, the precise alignment of separated Sagnac interferometer is achieved based on the principle of auto-collimation, whose position accuracy is better than 0.01 mm, angle accuracy is better than 1″, super possition accuracy of primary working plane is better than 1″.Accession Number: 20132216376032 -
Record 131 of
Title:The applications of laser tracking and ranging technology in space rendezvous and docking
Author(s):She, Wenji(1,2); Gao, Limin(1); Zhou, Liang(2); Li, Dawei(1); Wang, Rong(3)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 8905 Issue: DOI: 10.1117/12.2033065 Published: 2013Abstract:With the development of space technology, more and more Rendezvous and Docking (RVD) mission require more precise measurement of relative position and attitude between tracking spacecraft and target spacecraft. In the procedure of docking between near spacecraft, the optical retroreflector on the target Spacecraft were tracked by the laser tracking and ranging device on the tracking spacecraft, the distance data were provided by laser ranging system, and the azimuth data were provided by tracking gimbal, Synthesized the distance data and azimuth data, the relative position information between two spacecraft were provided to the target spacecraft. Furthermore, through tracking more than three point on the target spacecraft,the complete information of relative position and attitude between two spacecraft were calculated rapidly by the measurement system, which were presented to the control system during the whole RVD operating stage. The laser tracking technology guaranteed continuous measurement and supplied accurate azimuth information, and the laser ranging technology ensured high accuracy of distance information. In addition, the untouched measure mode give no disturbance to the docking operation, moreover, the monochromaticity of laser make the tracking and ranging procedure avoiding to be disturbed by parasitic light of space, thus there will be a effective measurement accompanying the whole docking operating procedure and affording valid data to the control system of docking. ? 2013 SPIE.Accession Number: 20134817032699 -
Record 132 of
Title:Fast automatic exposure approach for color digital camera
Author(s):Guo, Huinan(1,2); Cao, Jianzhong(1); Zhou, Zuofeng(1); Liao, Jiawen(1); Liu, Qing(1)Source: Guangxue Xuebao/Acta Optica Sinica Volume: 33 Issue: 10 DOI: 10.3788/AOS201333.1011003 Published: October 2013Abstract:Exposure accuracy of color digital camera directly affects the performance of color image and the sensory effects of human visual. An automatic exposure method of digital camera based on the color perceiving properties of human visual system, is proposed. A novel kind of exposure estimation function is also established through objective evaluating the sharpness, color saturation and brightness of input images. According to the statistical theory and empirical formulas, the functional relationship between the exposure estimation values and exposure step increment is calibrated and the exposure increment function is established as well. For different brightness properties of current frame, using the exposure increment function, the ideal exposure value of next frame in real time is calculated. A large number of experimental results show that the proposed method for different scenes and different lighting conditions always has a good performance in adjusting exposure value of the captured image. Meanwhile, the algorithm has good robustness which can achieve adjustment for input frames in short time.Accession Number: 20134817030485