2014
2014
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Record 73 of
Title:Compressed sensing based on the improved wavelet transform for image processing
Author(s):Pang, Peng(1,2); Gao, Wei(1); Song, Zongxi(1); Xi, Jiang-Bo(1,2)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 9284 Issue: DOI: 10.1117/12.2069221 Published: 2014Abstract:Compressed sensing theory is a new sampling theory that can sample signal in a below sampling rate than the traditional Nyquist sampling theory. Compressed sensing theory that has given a revolutionary solution is a novel sampling and processing theory under the condition that the signal is sparse or compressible. This paper investigates how to improve the theory of CS and its application in imaging system. According to the properties of wavelet transform sub-bands, an improved compressed sensing algorithm based on the single layer wavelet transform was proposed. Based on the feature that the most information was preserved on the low-pass layer after the wavelet transform, the improved compressed sensing algorithm only measured the low-pass wavelet coefficients of the image but preserving the high-pass wavelet coefficients. The signal can be restricted exactly by using the appropriate reconstruction algorithms. The reconstruction algorithm is the key point that most researchers focus on and significant progress has been made. For the reconstruction, in order to improve the orthogonal matching pursuit (OMP) algorithm, increased the iteration layers make sure low-pass wavelet coefficients could be recovered by measurements exactly. Then the image could be reconstructed by using the inverse wavelet transform. Compared the original compressed sensing algorithm, simulation results demonstrated that the proposed algorithm decreased the processed data, signal processed time decreased obviously and the recovered image quality improved to some extent. The PSNR of the proposed algorithm was improved about 2 to 3 dB. Experimental results show that the proposed algorithm exhibits its superiority over other known CS reconstruction algorithms in the literature at the same measurement rates, while with a faster convergence speed.Accession Number: 20150800546034 -
Record 74 of
Title:Design of three-field middle-wave infrared zoom system
Author(s):Fan, Zheyuan(1,2); Gao, Limin(1); Zhang, Zhi(1); Chen, Weining(1); Yang, Hongtao(1,2); Zhang, Jian(1); Wu, Li(1); Cao, Jianzhong(1)Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 43 Issue: 2 DOI: Published: February 2014Abstract:Three-field zoom system has advantages of simple mechanical structure, better reliability, short time of changing focal relative to other pattern zoom systems. Using 320×240 resolution cooled detector with 30 μm×30 μm pixel dimension, a middle-wave three-field optical system was designed by secondary imaging way. The system's F number is 4, FOV range is 1.4°-23.8°, it can realize 30 mm/100 mm/500 mm three position focal length. In designing process, the Germanium material and Silicon material were adopted to balance chromatic aberration, introducing one asphere to balance sphere aberration. The system use two mirrors reducing the axis dimension. The dimension of system better than 210 mm×160 mm×120 mm, it has characteristics of small dimension, simple zoom structure, good image quality etc. The modulation transfer function (MTF) is above 0.5 at spatial frequency of 17 lp/mm and energy concentration ratio is greater than 70% within the sensing element of the detector.Accession Number: 20141317523532 -
Record 75 of
Title:Effects of mirror surface roughness on encircled energy for far ultraviolet telescopes
Author(s):Fu, Huaiyang(1,2); Zhou, Sizhong(1); Jiang, Kai(1); Mei, Chao(1,2); Zhang, Hui(1,2)Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 43 Issue: 8 DOI: Published: August 25, 2014Abstract:The image quality was degraded by the surface roughness of astronomy imaging applications, and it might be specified in terms of fractional encircled energy. Relationship between the encircled energy and roughness RMS was qualitatively analysed by cosine phase grating model, moreover, the effective transfer function of the surface was built drew on Fourier optical linear systems theory, then the associated angle spread function as well as encircled energy were deduced. For 1 216?(1?=0.1 nm) far ultraviolet telescope which closed to diffraction limit and in the terms of primary and secondary mirrors roughness RMS were far less than one wavelength, encircled energy versus RMS roughness and autocovariance width could be infered. So resolution error caused by surface roughness was limited in 0.171 5, the manufacturing requirement for mirrors roughness RMS was less than 31 ?and autocovariance width was longer than one wavelength. It's useful for our manufacturing guiding significance.Accession Number: 20143900069794 -
Record 76 of
Title:Color fusion method for low-level light and infrared images
Author(s):Yang, Shaokui(1,2); Liu, Wen(1)Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 43 Issue: 5 DOI: Published: May 2014Abstract:The complementary nature of low-level light image intensifiers and thermal infrared cameras makes them possible to observe the scene under almost any conditions (day/night/smoke/fog). A color fusion method of low-level-light and infrared images was introduced to render multiband imagery in comparative realistic color appearance. Firstly, the center-surround opponent-color fusion scheme was used to yield color imagery. Next, the histograms of the image were matched to those of the reference image in YCbCr color space. This transfered the natural color characteristics of daylight imagery into multispectral night vision images. In order to enhance the contrast of the fused imagery, a grayscale fused image was used to replace the luminance component of the multiband imagery and then implement the histogram matching. The experiment results demonstrate the proposed method is effective in displaying the fused imagery in natural colors and popping out targets. This fused data can help observers or machine vision systems to process this type of images efficiently, therefore reducing detection and recognition times and improving situational awareness.Accession Number: 20142617873697 -
Record 77 of
Title:Theory of circular plate for mirrors on back-point support
Author(s):Liang, Yuanqing(1,2); Zhou, Sizhong(1); Jiang, Bo(1,2)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 9280 Issue: DOI: 10.1117/12.2067980 Published: 2014Abstract:In space reflective optical system, the back-point support is one of the widely used support means. For back-point support method, the support points position are important for the deformation of the reflective surface, find the best support points position of the mirror is particularly important. A new technique of mass allocation was discovered by using the theory of circular plate in this paper, and then the mass allocation method was used to look for the locations of the back support points on a single ring for a circular mirror having a central hole (primary mirror of Cassegrain telescope). Then the Ansys software was used to calculate the deformation of the reflective surface when the mirror supported under different radius. It was validated that the mirror surface deformation is minimized due to gravity when supported in these positions which confirmed by mass allocation. It was proved that mass allocation is a simple and effective way to find the optimum support location of back-point support. ? 2014 SPIE.Accession Number: 20150800541562 -
Record 78 of
Title:Method of focal length measurement for infrared optical system with long focal length
Author(s):Yao, Zhen(1,2); Wu, Yiming(1); Gao, Limin(1); Wu, Cuigang(1); Mei, Chao(1,2)Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 43 Issue: 6 DOI: Published: June 2014Abstract:In strong laser host device, various optical lens with different focal length are needed to expand and collimate the beam, the accurate of the lens'focal length directly affect the overall performance of the system, so it is particularly important to accurately measure the focal length of lens. A new method of measuring the infrared optical system with long focal length by using the Hartmann- Shack wave-front detected device and rotated plane mirror was proposed. The measuring principle of the system was given. Using optical simulation software ZEMAX, the influence of different aperture on the measurement of focal length was analyzed. Then the relationship between the rotation angle of the plane mirror and the system measurement error was deducted by using error theory. Finally the experiment was done to obtain the real result, the result of measurement shows that when the plane mirror rotated to a certain angle, set an appropriate optical aperture, the system measurement precision can be better than 3‰, much higher than the traditional measuring method. In addition, the measurement method is also conveniently to use, high stability in measure, etc..Accession Number: 20142917960095 -
Record 79 of
Title:Laser communication optical system based on reflective eccentric-pupil cassegrain antenna
Author(s):Yan, Peipei(1); Deng, Xiaoguo(1); Zhang, Hengjin(1); Mei, Chao(1)Source: Guangxue Xuebao/Acta Optica Sinica Volume: 34 Issue: DOI: 10.3788/AOS201434.s122003 Published: September 10, 2014Abstract:The concept of reflective eccentric-pupil Cassegrain antenna is introduced. Because the traditional on-axis Cassegrain antenna used in laser communication has obscuration, the efficiency of transmitting and receiving power is decreased greatly. This new kind of reflective eccentric-pupil Cassegrain antenna is unobscured, so it improves the efficiency of transmitting power and receiving power effectively. Its properties such as gain, image quality, and transmission efficiency are analyzed. The power decline curve is obtained by detailed analyzing the antenna system in partial axis situation. Besides, it is transceiver, so the system volume and weight are reduced greatly. The complexity is reduced enormously at the same time.Accession Number: 20144100087850 -
Record 80 of
Title:Research on nonsmooth H∞ control for the adaptive optics system
Author(s):Zhao, Xin(1,2); Ma, Cai-Wen(1)Source: Guangzi Xuebao/Acta Photonica Sinica Volume: 43 Issue: 9 DOI: 10.3788/gzxb20144309.0901003 Published: September 1, 2014Abstract:To design an adaptive optics robust controller with the characteristics of simple structure and low orders, a nonsmooth H∞ control method for the adaptive optics system was proposed. The full order H∞ controller and the reduced order H∞ controller were designed by conventional H∞ control method combined with model reduction based on Hankel singular values. And the orders of the controllers are 226 and 163 respectively, whereas the nonsmooth H∞ controller designed for the system is simply the product of a constant matrix and a 4 order single input single output transfer function. For the sake of control performance verification and comparation, the dynamic atmospheric turbulence wavefront phase was simulated, as well as the residual wavefront phase corrected by adaptive optics systems with the full order H∞ controller and with the nonsmooth H∞ controller. The simulation demonstrates that the two adaptive optics systems achieve approximate control performance, and proves the efficiency of nonsmooth H∞ control method for the adaptive optics system.Accession Number: 20144500153448 -
Record 81 of
Title:Secrecy outage and diversity analysis of cognitive radio systems
Author(s):Zou, Yulong(1); Li, Xuelong(2); Liang, Ying-Chang(3,4)Source: IEEE Journal on Selected Areas in Communications Volume: 32 Issue: 11 DOI: 10.1109/JSAC.2014.141121 Published: November 1, 2014Abstract:In this paper, we investigate the physical-layer security of a multi-user multi-eavesdropper cognitive radio system, which is composed of multiple cognitive users (CUs) transmitting to a common cognitive base station (CBS), {while multiple eavesdroppers may collaborate with each other or perform independently in intercepting the CUs-CBS transmissions, which are called the coordinated and uncoordinated eavesdroppers, respectively. Considering multiple CUs available, we propose the round-robin scheduling as well as the optimal and suboptimal user scheduling schemes for improving the security of CUs-CBS transmissions against eavesdropping attacks. Specifically, the optimal user scheduling is designed by assuming that the channel state information (CSI) of all links from CUs to CBS, to primary user (PU) and to eavesdroppers are available. By contrast, the suboptimal user scheduling only requires the CSI of CUs-CBS links without the PU's and eavesdroppers' CSI. We derive closed-form expressions of the secrecy outage probability of these three scheduling schemes in the presence of {the coordinated and uncoordinated eavesdroppers. We also carry out the secrecy diversity analysis and show that the round-robin scheduling achieves the diversity order of only one, whereas the optimal and suboptimal scheduling schemes obtain the full secrecy diversity, {no matter whether the eavesdroppers collaborate or not. In addition, numerical secrecy outage results demonstrate that for both the coordinated and uncoordinated eavesdroppers, the optimal user scheduling achieves the best security performance and the round-robin scheduling performs the worst. Finally, upon increasing the number of CUs, the secrecy outage probabilities of the optimal and suboptimal user scheduling schemes both improve significantly. ? 2014 IEEE.Accession Number: 20145200371523 -
Record 82 of
Title:Nonlinear absorption of SWNT film and its effects to the operation state of pulsed fiber laser
Author(s):Li, Xiaohui(1); Wang, Yonggang(2); Wang, Yishan(2); Zhao, Wei(2); Yu, Xuechao(1); Sun, Zhipei(3); Cheng, Xueping(4); Yu, Xia(5); Zhang, Ying(5); Wang, Qi Jie(1)Source: Optics Express Volume: 22 Issue: 14 DOI: 10.1364/OE.22.017227 Published: 2014Abstract:We study a single-wall carbon nanotube (SWNT) Polyvinyl alcohol (PVA) composite as a saturable absorber (SA) for pulse generation in Yb-doped fiber lasers. The saturable absorption and optical limiting (OL) characteristics of the SWNT device are investigated. By combing these two nonlinear effects, we find out for the first time, to the best of our knowledge, that mode-locking can be obtained in the dissipative soliton regime at low pumping followed by Q-switching at high pumping, which is quite different from conventional pulse dynamic evolutions. The Qswitched state operating at higher pump powers is due to the OL effect. The inverted operating fiber laser can be applied in various potential applications such as versatile material processing, optical communication and radar system etc. ? 2014 Optical Society of America.Accession Number: 20143017972266 -
Record 83 of
Title:A method to measure off-axis fabrication and off-axis angle of axis aspheric mirror precisely
Author(s):Zhang, Xuemin(1,2); Wei, Ruyi(1,2); Yu, Tao(1); Hou, Xiaohua(1); Duan, Jiayou(1); Li, Hua(1)Source: Zhongguo Jiguang/Chinese Journal of Lasers Volume: 41 Issue: 4 DOI: 10.3788/CJL201441.0416001 Published: April 2014Abstract:The alignment method of off-axis three-mirror anastigmat combines initial positioning and computer-aided alignment. During manufacturing, due to the limit of testing methods, the off-axis fabrication and off-axis angle cannot be measured precisely. The initial positioning based on the manufacturing off-axis parameter can bring large initial aberration, which can not be converged when using computer-aided alignment. The optical path is analyzed based on the auto-collimation principle, and the mathematic relationship between the position of off-axis mirror and the reflected image is derived. A system based on the relationship is given to measure the off-axis fabrication and off-axis angle, it includes the right angle plate of high precision, linear guides of high precision, the special center orientation tool, internal focusing telescope and self-standardized micro-flat optical tube. The measurement accuracy of off-axis fabrication and off-axis angle is ±0.05 mm and ±10″ respectively.Accession Number: 20142117752736 -
Record 84 of
Title:Measurement of extinction ratio by dual modulation
Author(s):Li, Chun-Yan(1,2); Wu, Yi-Ming(1); Gao, Li-Min(1); Lu, Wei-Guo(1); Xiao, Mao-Sen(1)Source: Guangxue Jingmi Gongcheng/Optics and Precision Engineering Volume: 22 Issue: 3 DOI: 10.3788/OPE.20142203.0582 Published: March 2014Abstract:A method by using magneto-optical modulation and light source modulation techniques was proposed to measure the extinction ratio of a polarizing prism precisely, and an extinction ratio measurement system was also established based on the two modulation techniques. Firstly, the system's measurement model was derived according to the Jones matrix describing manner of polarized light. By using a magneto-optical modulator, the optical axis angle between a polarizer and a measured polarizing prism was precisely located. Then, by using a chopper to modulate the square wave of a light source, the impact of noises on the system measurement accuracy was eliminated and the system could measure the light intensity value accurately after the measured polarizing prism's axis was located precisely. Finally, the polarizing prism was measured for a number of times and the data were averaged. The experimental results indicate that the measurement accuracy of extinction ratio for the polarizing prism can be 10-6, which verifies the effectiveness and stability of the method. The system is characterized by high stability, high accuracy, and can offer the references for the performance test and engineering applications of polarized devices.Accession Number: 20141817659555