2012
2012
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Record 169 of
Title:Shifted natural frequency with increasing excitation level of moon-based telescope gamble in vibration test
Author(s):Li, Zhi-Guo(1,2); Gao, Li-Min(1); Zhang, Bo-Ni(3); Wang, Zhen-Yu(1); Cui, Kai(2)Source: Guangxue Jingmi Gongcheng/Optics and Precision Engineering Volume: 20 Issue: SUPPL. DOI: 10.3788/OPE.20122013.0230 Published: December 2012Abstract:The natural frequency shifts like structure stiffness decreased, damping increased and natural frequency decreased with excitation level increasing in the vibration test of a moon-based telescope gimble are analyzed in this paper. The mathematics model between bearing stiffness and vibration load is established based on Hertz theory. The simulation shows that the bearing stiffness will decrease to the minimum when the vibration load goes up to 2.83 times of the preload and then the bearing stiffness will increase with the increasing of vibration load. The qualitative analysis of structure joint is given. In order to obtain the law of frequency shift, a special test is performed. The models of single degree of freedom based on linear theory and Duffing hypothesis are presented and simulated. The stiffness and damping coefficients of both models are identified. It suggests that the accuracy of gimbal analysis should be achieved by adjusting the bearing stiffness dynamically according to the load instead of setting a fixed one.Accession Number: 20132216372310 -
Record 170 of
Title:Design and analysis of flexure hinge in the double crystal monochromator
Author(s):Zhao, Xiangguo(1,2); Zhou, Sizhong(1); Jiang, Bo(1,2); Jiang, Kai(1,2); Mei, Chao(1,2)Source: Applied Mechanics and Materials Volume: 226-228 Issue: DOI: 10.4028/www.scientific.net/AMM.226-228.2175 Published: 2012Abstract:This paper analyzes the relationship between the parameters of CFH (Cosine Flexure Hinge) and the adjustable angle in the measurement and micro-adjustment of yaw, pitch and roll angle in the DCM (Double Crystal Monochromator). We derive the motion equations of CFH during the measurement and adjustment process, and get accurate expression formulas. Then we use ANSYS software to simulate the CFH and compare the simulation value and the theoretical value. It shows that the maximum angular deflection error is less than 3.5 percent. We compare the CFH to the RCFH (Right Circular Flexure Hinge), and get that the maximum angular deflection θ y and the linear displacements of RCFH are all about 1.56 times than the CFH when the parameters are equivalent. Therefore, we provide a simple flexure hinge to improve the stability and accuracy of angular measurement and micro- adjustment in the DCM. ? (2012) Trans Tech Publications, Switzerland.Accession Number: 20125215834667 -
Record 171 of
Title:Study on correlation-tracking method based on edge detection in long-wave infrared image
Author(s):Hao, Wei(1); Zhang, Kun(1,2); Zhan, Zhenhuan(1,2)Source: Chinese Optics Letters Volume: 10 Issue: SUPPL.2 DOI: 10.3788/COL201210.S21005 Published: December 2012Abstract:This letter presents a correlation tracking algorithm based on edge detection, in allusion to the phenomenon that the target is susceptible to interference in long-wave infrared image. Firstly, the collected imageis processed by median filtering to remove the defects in the detector. Then thegradient information of the background is filtered out by edge detection method. Secondly, to enhance the edge information, the image is dealt with mathematical morphology (MM). And finally, the correlation matching method is done to acquire the miss-distance information of the target in the image. Through theoretical simulation and practical verification, it is proved that the algorithm has a better effect on inhibiting most of the background information, protecting the target's information effectively, enlarging the weight of the target's information in the correlation operation and improving stability of the detector. ? 2012 Chinese Optics Letters.Accession Number: 20131016087929 -
Record 172 of
Title:A new illuminating source for the ship wake detection
Author(s):Tang, Jing(1,2); Xie, Zheng-Mao(1); He, Jun-Hua(1); Cang, Yu-Ping(1,2)Source: Guangdianzi Jiguang/Journal of Optoelectronics Laser Volume: 23 Issue: 2 DOI: Published: February 2012Abstract:The quality of bubble image is determined by the efficiency of underwater optical system in ship wake detection, while the illuminating source is an important factor that affects the performance of the underwater imaging system. A new sheet laser source is proposed in order to solve the problem, and the utilization rate and feasibility are analyzed and proved. The test results show that the new illuminating source can not only solve the lighting of the imaging system, but also avoid excess images overlapping within the depth region of the optical field. The proposed light source creates significant terms for acquiring the parameters of the bubble curtain. This new design can be used in under-water optical systems because of its unique advantages.Accession Number: 20121114852826 -
Record 173 of
Title:The melioration on spectra response heterogeneity of hadamard transform spectral imager
Author(s):Liu, Cai-Fang(1,2); Hu, Bing-Liang(1); Wei, Ru-Yi(1); Yan, Peng(1)Source: Guang Pu Xue Yu Guang Pu Fen Xi/Spectroscopy and Spectral Analysis Volume: 32 Issue: 5 DOI: 10.3964/j.issn.1000-0593(2012)05-1427-04 Published: May 2012Abstract:Hadamard transform optics has been developed in the past decades. It has been used in distinguishing targets, detecting feeble signals and so on. Hadamard transform spectral imager (HTSI), based on Digital Micro-Mirror Device, is a new dispersion spectral imager. HTSI has been developed in our laboratory. The spectral heterogeneity of encoded image captured by HTSI has been researched according to spectrum calibration in this paper. Relative and absolute spectrum emittance calibration algorithms have been proposed first time on HTSI to meliorate the spectrum heterogeneity. It aims at the problem that the accuracy of recovered spectrum is depressed by the heterogeneity noise and disorder encoding spectrum in spectral image. Simulation and experiment result have demonstrated that the meliorated spectral curve is close to the standard spectrum, and the variance of the recovered spectrum ranges from 2.4% to 4.2% with regard to the spectral image of 7 waves. This is fully satisfied for the requirement of laboratory and projects.Accession Number: 20122615178952 -
Record 174 of
Title:Investigation of the arbitrary waveform semiconductor laser as seed light source for high energy laser
Author(s):Wang, Hongyun(1,2); Da, Zhengshang(1); Liu, Baiyu(1); Liu, Hui(1,2)Source: Microwave and Optical Technology Letters Volume: 54 Issue: 3 DOI: 10.1002/mop.26652 Published: March 2012Abstract:A pulse semiconductor laser modulated by arbitrary shaping electrical waveform is produced and the generated optical pulse can be taken as the seed resource for high-power laser facilities. Based on ultrawide band microwave device and microstrip line transmission delay application, an all-solid-state circuit for generating arbitrary modulation pulse to modulate the semiconductor laser is fabricated. For improving the semiconductor laser power, the output laser pulse is sent into erbium-doped fiber master oscillator power amplifier architecture for amplification. In the experiment, the output laser pulse can be arbitrarily adjusted at 1547.9 nm center wavelength, less than 10 ns duration, lower than 100 kHz repetition rate, and 330 ps time domain adjustment. ? 2012 Wiley Periodicals, Inc.Accession Number: 20120914816819 -
Record 175 of
Title:An alignment of primary and secondary mirrors for optical system in large telescopic
Author(s):Han, Juan(1); Duan, Jiayou(1); Chen, Jianjun(1); Zhang, Jun(2); Kang, Jian(1)Source: Zhongguo Jiguang/Chinese Journal of Lasers Volume: 39 Issue: 7 DOI: 10.3788/CJL201239.0716001 Published: July 2012Abstract:In order to realize the alignment of primary and secondary mirrors in large aperture telescopic system and improve optical imaging quality, a new method for adjusting comparative position and pose between primary and secondary mirrors is introduced named high-precision alignment machining. Other than a traditional method of adjusting washer, the method can eliminate astigmatism aroused from inclination between primary and secondary mirrors, and coma aberration aroused from secondary mirror's eccentricity at the same time. The method reduces the alignment difficulty markedly and avoids systemic instability. In addition, a new method for primary and secondary mirrors test is established by combination of interference auto-collimating tests and cross wire application which replaces optical axis. The alignment and test's result from the Φ520 mm primary and secondary mirrors shows that root-mean-square (RMS) value of wave aberration hardly changes before and after assembling, and is entirely less than 0.03λ (λ=632.8 nm), axial angles swaying in primary and secondary mirrors are 0.72″ and 2″, respectively, the verticalities of two mirrors optical axis and respective frames are less than 0.005 mm, primary and secondary mirrors's concentricity is less than 0.01 mm, and the RMS value of the system is less than 0.7 λ after interation, which achieves design requirements.Accession Number: 20123715431662 -
Record 176 of
Title:Aerial target automatic classification based on improving bag of words model
Author(s):Zhu, Xufeng(1,2); Ma, Caiwen(1); Liu, Bo(1)Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 41 Issue: 5 DOI: Published: May 2012Abstract:In order to solve three types of aerial target (aircraft, helicopter, missile) images automatic classification, an improving bag of words model for recognizing aerial targets was proposed. Firstly, many grey images of three types of aerial targets were collected and segmented for extracting target from background. Secondly, those images, which only included target, were sampled and extracted using scale-invariant feature transform (SIFT) descriptored by sparse sampling. Thirdly, fuzzy C means (FCM) clustering was used and plenty of visual words on target images were acquired. Finally, histograms of visual words were used to training support vector machine (SVM) classifier and aerial target type would be identified. Experiments are shown that the proposed algorithm can distinguish the types of aerial targets effectively. Moreover, combining with the SVM classifier, the recognition rate by the proposed algorithm is better than traditional bag of words model by K means clustering and affine moments.Accession Number: 20122915259978 -
Record 177 of
Title:Design of high-speed photography optical system for air bubbles in water
Author(s):Xie, Zhengmao(1,2); Gao, Limin(1); He, Junhua(1)Source: Guangxue Xuebao/Acta Optica Sinica Volume: 32 Issue: 4 DOI: 10.3788/AOS201232.0422002 Published: April 2012Abstract:For the purpose of study on diameter, velocity and concentration of air bubbles in water, an optical system of illumination and 3D photography based on high-speed imaging charge-coupled device is proposed. Based on Galileo structure with three cylindrical lens and semiconductor laser of wavelength 532 nm, a light sheet with thickness of 1.5 mm and width of 44 mm is designed. Three groups of imaging lens with magnification of 0.4×, 1× and 2.5×, having a uniform conjugate distance of 530 mm are designed. Each group relayed by collimated light includes frontal lens and focusing lens. A simple and reliable structure of 2D high-speed photography for the area of 60 mm×40 mm and 1D scan with length of 5 mm along the optical axis, is achieved by moving light sheet and frontal lens synchronously. The imaging quality of the optical system with magnification of 0.4×, 1× and 2.5× is evaluated, it shows that the modulation transfer function of 0.707ω has reached 0.58, 0.55 and 0.38 respectively at the spatial frequency of 50 lp/mm, as well as the diameter resolution of air bubbles in water has been from 10 μm to 450 μm.Accession Number: 20122415111302 -
Record 178 of
Title:Optical design of off-axis three-mirror anastigmatic system for imaging spectrometer
Author(s):Wang, Meiqin(1,2); Wang, Zhonghou(1); Bai, Jiaguang(1)Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 41 Issue: 1 DOI: Published: January 2012Abstract:Imaging spectrometer requires its optical system have high spatial resolution and spectral resolution over wide field of view and waveband range. A design method for unobstructed, off-axis, reflective optical system was proposed. When pupil and field of view were off-axis properly, obstructing between mirrors was avoided based on the three-mirror anastigmatic. According to the parameters, the unobstructed, off-axis three-mirror anastigmatic systems were designed, when the aperture stop was in front of primary mirror, or on the secondary mirror or focal point of third mirror. The optical system has a spectral region from 1.0 μm to 2.5 μm, focal length of 1600 mm, relative aperture of f′/5, field of view of angle of 6.86°×1.48°. Their imaging qualities reach the diffraction limit and meet the requirements of the imaging spectrometer's optical system, which has wide field of view and large relative aperture.Accession Number: 20121114853069 -
Record 179 of
Title:Infrared image de-noising based on K-SVD over-complete dictionaries learning
Author(s):Shan, Bin(1); Hao, Wei(1); Zhao, Rui(2)Source: 2012 5th International Congress on Image and Signal Processing, CISP 2012 Volume: Issue: DOI: 10.1109/CISP.2012.6469839 Published: 2012Abstract:The sparse representation of image based on over-complete dictionaries is a new image representation theory. Using the redundancy of over-complete dictionaries can effectively capture the various structure detail characteristics of an image, so as to realize the efficient representation of the image. In this paper we propose an infrared image de-noising algorithm based on K-SVD over-complete dictionaries learning using the over-complete dictionary image sparse representation theory. The experimental results compared with the common de-noising algorithm processing results prove the effectiveness of the proposed method. ? 2012 IEEE.Accession Number: 20131216133900 -
Record 180 of
Title:Wave aberration measuring system of optical lens with small-field of view based on auto-collimating principle
Author(s):Zhang, Xuemin(1,2); Wei, Ruyi(1,2); Li, Hua(1); Duan, Jiayou(1); Yang, Jianfeng(1)Source: Zhongguo Jiguang/Chinese Journal of Lasers Volume: 39 Issue: SUPPL.1 DOI: 10.3788/CJL201239.s108011 Published: June 2012Abstract:In order to measure the wave aberration of optical lens with small field of view rapidly and precisely, a new wave aberration measuring system based on both auto-collimation principle and Fizeau spherical laser interferometer measurement principle is described. The wave aberration measurement principle by Fizeau spherical laser interferometer is introduced. The assembling and measuring methods of this new auto-collimation-based wave aberration system are discussed and analyzed in detail. By using the characteristic of auto-collimation optics, the in-terferometer's axis, the optical lens's optical axis and the high-precision reflector's axis are precisely determined, and the fast assembly of the optical system is implemented too. Analyses reveal that this system can be an effective solution to the optical axis deviation problem in measuring the wave aberration of optical lens with small-field of view, and implementing the wave aberration test of optical lens rapidly and accurately.Accession Number: 20123715432062