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Record 325 of
Title:Cavity dumped laser using fast GaAs photoconductive switch
Author(s):Zhu, Shaolan(1,2); Zhao, Wei(1); Liu, Baiyu(1); Shi, Wei(3); Yang, Yanlong(1,2)
Source: Zhongguo Jiguang/Chinese Journal of Lasers Volume: 38 Issue: 5 DOI: 10.3788/CJL201138.0502003 Published: May 2011
Abstract:Cavity dumping is an effective technique for generating Q-switched laser pulses of relatively large energy and extremely short time duration, and the width of Q-switched pulses is primarily a function of the oscillator cavity length. The solid state lateral semi-insulating GaAs photoconductive semiconductor switch (PCSS) has the unique ability to handle high power at very fast response time with very little timing jitter. A novel and effective technique of cavity dumping laser for generating short Q-switched laser pulses with a GaAs PCSS is presented. In a flashlamp pumped Nd:YAG laser with 20 cm long stable resonator, 1.7 ns short laser pulses have been obtained, and the pulse to pulse duration instability is less than 7% and energy instability is less than 3%.
Accession Number: 20112414058020
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Record 326 of
Title:Temporal resolution of X-ray detector for pulsar navigation
Author(s):Sheng, Li-Zhi(1,2); Zhao, Bao-Sheng(1); Hu, Hui-Jun(1,2); Wang, Peng(1,2); Yan, Qiu-Rong(1,2); Chen, Bao-Mei(1,2); Liu, Yong-An(1); Ouyang, Xiao-Ping(3); Chen, Ding(4)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 8196 Issue: DOI: 10.1117/12.900678 Published: 2011
Abstract:Pulsar navigation is a promising new technique for space exploration because of its autonomous and deep space capability. Since the baseline of pulsar navigation approach is to observe the X rays (0.2～20keV) emitted from pulsars, a compact high temporal resolution X-ray detector is needed. In this paper an micro-channel plate(MCP) photon counting detector sensitive to X-rays is proposed. The detection system consists of a CsI photocathode, a 50mm diameter micro-channel plate (MCP) stack, a collection anode, a preamplifier, a constant fraction discriminator(CFD) and data acquisition(DAQ). The incident X-rays photons are absorbed by CsI and converted to photoelectrons, the electrons are multiplied by MCP and collected by the anode. Anode output signal is a fast pulse which need to be amplified by preamplifier and then fed to CFD circuit and DAQ for a precise timing. The total temporal resolution(ΔT) of the entire detection system could be determined by ΔtD, the intrinsic temporal resolution of cathode-MCP-anode, and ΔtE the resolution of electronic system including preamplifier and CFD. The resolution of the detection system is tested to be 18.4ns in experiment. ? 2011 SPIE.
Accession Number: 20113614296276
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Record 327 of
Title:Over 300 nm tunable broadband one-crystal noncollinear optical parametric amplification
Author(s):Long, H.B.(1,2); Li, X.F.(3); Liu, H.J.(1)
Source: Laser Physics Volume: 21 Issue: 1 DOI: 10.1134/S1054660X11010130 Published: January 2011
Abstract:An over 300 nm tunable broadband noncollinear optical parametric amplification in visible scale as well as the generation of blue pump pulses in one BBO crystal are demonstrated. Micro-joule energies are achieved in the signal branch, and the signal central wavelength can be tuned from 475 to 800 nm. The near-transform-limited sub-50 fs pulse duration is attainable over the whole tuning range after compression by a pair of prisms. ? 2011 Pleiades Publishing, Ltd.
Accession Number: 20110913704035
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Record 328 of
Title:Nonlinear frequency conversion in bismuth-doped tellurite suspended core fiber
Author(s):Ryasnyanskiy, Aleksandr(1); Lin, Aoxiang(1,2); Belwalkar, Amit(3); Guintrand, Cyril(1); Biaggio, Ivan(1); Toulouse, Jean(1)
Source: Optics Communications Volume: 284 Issue: 16-17 DOI: 10.1016/j.optcom.2011.04.019 Published: August 1, 2011
Abstract:We have developed a new kind of tellurite glass with composition 70.5TeO2-12ZnO-10Na2O-7.5Bi2O3 by conventional melting-quenching techniques. A suspended-core fiber (SCF) with a triangular-shaped core (~ 2.9 μm) has been drawn from an extruded perform. Several nonlinear frequency conversion processes are being demonstrated, which point to the potential of such a fiber. ? 2011 Elsevier B.V. All rights reserved.
Accession Number: 20112314032151
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Record 329 of
Title:Design of high ratio middle infrared continuous zoom optical system
Author(s):Fan, Zheyuan(1,2); Cao, Jianzhong(2); Yang, Hongtao(1,2); Qu, Enshi(2); Wu, Dengshan(2)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 8193 Issue: DOI: 10.1117/12.900176 Published: 2011
Abstract:In recent years, the demand for infrared zoom systems is increasing in proportion with the development of infrared technology and its applications. To meet this demand a variety of zoom lenses have been designed. Infrared cameras operating in the 3-5μm spectral band are used in a wide variety of applications such as targeting, rescue, guidance and surveillance systems as well as other equipment. This paper using cool 320x240 detector with staring focal plane array and secondary imaging, a mid-wave optical system using mechanical-compensated with large-aperture and a zoom range of 10:1 is designed. The Pixel Dimensions of the detector is 30μm, and the wavelength between 3.7μm ～4.8μm.The system adopts negative group variable times and positive group of compensation which can realize 33mm～330mm continuous zoom and FOV =20.61°～2.08°,it consists of 7 lenses including 3 aspheric surface. The length of the system is 262mm with the reflection mirror multipass optical path. The results show that the modulation transfer function(MTF)are above 0.4 within the whole focal range at spatial frequency of 17 lp/mm, and Root Mean Square (RMS) value of spot diameter were smaller than the Pixel Dimensions. After the image quality being optimized, the narcissus analysis is done and 100% cold shield efficiency is obtained. Finallythe monotonic and smooth Cam curve is given. The curve shows that the imaging plane is stable and the cam is easy to process. The system has advantages of simple structure, high image quality and short zoom path etc. ? 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).
Accession Number: 20114114420330
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Record 330 of
Title:Design of bipod flexures for space mirror
Author(s):Chu, Chang-Bo(1,2); Li, Ying-Cai(1); Chai, Wen-Yi(1); Fan, Xue-Wu(1)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 8196 Issue: DOI: 10.1117/12.902227 Published: 2011
Abstract:Bipod flexures are used in many high-precision space mirror mount applications. The flexures are used to provide moment isolation for the mirror to minimize surface figure distortion resulting from mount assembly error or distortion of the mount temperature-change-induced. In this paper, we developed a bipod flexure for the Zerodur primary mirror with diameter 520 mm and thickness 70 mm. The characteristic of the bipod flexure is the two-strip flexure on the top and bottom of each leg. By those, the bending stress in mirror resulting from the mount assembly is remarkably reduced. Thanking to a semi-open structure with small mouth and big stomach in the back and a six parts symmetrical honeycomb structure for the primary mirror, using the FEA (Finite Element Analysis) method we analyze that how the axial and circumferential locations of the three bipod flexures impact mirror surface figure and gain the better result after optimization. In the design of the detail bipod flexures, thickness of the blade is analyzed and compared; also we achieve an optimization design. The two results demonstrate that the bipod flexures could keep the precision of the mirror surface figure under the load of external force and thermal constraints and meanwhile they could keep stability of structure. ? 2011 SPIE.
Accession Number: 20113614296319
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Record 331 of
Title:A fast and low complexity approach for H.264/AVC intra mode decision
Author(s):Su, Xiuqin(1); Ji, Lei(1); Li, Xiang(1)
Source: Multimedia Tools and Applications Volume: 52 Issue: 1 DOI: 10.1007/s11042-009-0452-z Published: March 2011
Abstract:As one of the main features of H.264/AVC, intra prediction coding technique acts as a basis for encoding performance and efficiency. In official reference software Joint Model (JM), it employs the rate distortion optimization (RDO) technique to get to the best encoding performance. By full searching (FS) all of the candidate modes under the rule of RDO, peak-signal-noise-rate (PSNR) decreases to a very low level, but at the same time, the complexity of calculation increases a lot. Many researchers had devoted to searching the fast algorithm which can decrease the complexity, and had designed so many excellent and intelligent fast algorithms. In this paper we introduced a low complexity and fast approach for H.264/AVC intra prediction algorithm. The new approach is based on reducing the number of candidate modes for further RDO calculation, and decreasing the computational complicacy. It can decide the interpolation direction accurately by calculating the directional pixel-value differences (DPD) of target block, and then do statistic with the obtained values to choose the most probable modes. The experimental results demonstrate that the proposed algorithm can achieve more than 70% time saving than JM, but only a tiny degradation of encoding performance is brought in. ? 2010 Springer Science+Business Media, LLC.
Accession Number: 20110713659835
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Record 332 of
Title:Optical design of aerial digital camera based on large planar array CCD
Author(s):Yan, Aqi(1,2); Yang, Jianfeng(1); Cao, Jianzhong(1)
Source: Guangxue Xuebao/Acta Optica Sinica Volume: 31 Issue: 6 DOI: 10.3788/AOS201131.0622003 Published: June 2011
Abstract:Optical system of an aerial digital camera based on large planar array CCD with 50 million pixels is designed, considering aerospace environment and imaging quality. The focal length of aerial digital camera is 75 mm, F number is 4, and distortion is less than 0.1%. The required working temperature is between -40°C~60°C. After carefully research on the influence of temperature on imaging quality of optical system, a new approach is put forward. Aerial digital camera can reach excellent imaging quality when soaking in a large temperature change by this new technique. This approach can not only eliminate defocusing effect of optical system caused by temperature change, but also make the aerial digital camera be smaller and less weighty.
Accession Number: 20112714124022
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Record 333 of
Title:The extracting system design of small dim targets in complex background
Author(s):Liang, Dong Sheng(1,2); Liu, Hui(1); Liu, Wen(1)
Source: Advanced Materials Research Volume: 328-330 Issue: DOI: 10.4028/www.scientific.net/AMR.328-330.2324 Published: 2011
Abstract:For the moving small dim targets in visible image sequences with low SNR and complex background, whose contained characters are simple and poor, they are extracted difficultly. This paper proposes a new method to detect and extract positions of small dim moving targets. According to the features of moving targets, in a very short time interval, the target trajectory is considered as a straight line approximately. Firstly, it makes use of threshold segmentation methods to extract the positions of targets in each frame, then building the motion line equations after the joint of multi-frame processing results. Finally, the position of small dim targets are detected out and extracted, and false targets are eliminated accurately. Hardware system was designed and the algorithm is implemented on hardware systems successfully. The experiment results show related functions of the system and extracting algorithm is feasible, the system is stable and has a strong process ability, which can effectively detect and extract small and dim target in complex background correctly. ? 2011 Trans Tech Publications.
Accession Number: 20113914373355
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Record 334 of
Title:LUT: A Lunar-based Ultraviolet Telescope
Author(s):Cao, Li(1); Ruan, Ping(2); Cai, HongBo(1); Deng, JinSong(1); Hu, JingYao(1); Jiang, XiaoJun(1); Liu, ZhaoHui(2); Qiu, YuLei(1); Wang, Jing(1); Wang, Shen(1); Yang, JianFeng(2); Zhao, Fei(1); Wei, JianYan(1)
Source: Science China: Physics, Mechanics and Astronomy Volume: 54 Issue: 3 DOI: 10.1007/s11433-011-4255-7 Published: March 2011
Abstract:The Lunar-based Ultraviolet Telescope (LUT) is a funded lunar-based ultraviolet telescope dedicated to continuously monitoring variable stars for as long as dozens of days and performing low Galactic latitude sky surveys. The slow and smooth spin of the Moon makes its step by step pointing strategy possible. A flat mirror mounted on a gimbal mount is configured to enlarge the sky coverage of the LUT. A Ritchey-Chrétien telescope with a Nasmyth focus configuration is adopted to reduce the total length of the system. A UV enhanced back illuminated AIMO CCD 47-20 chip together with the low noise electric design will minimize the instrumental influence on the system. The preliminary proposal for astrometric calibration and photometric calibration are also presented. ? Science China Press and Springer-Verlag Berlin Heidelberg 2011.
Accession Number: 20112113998893
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Record 335 of
Title:Design of catadioptric infrared optical system with wide field
Author(s):Wang, Wen-Fang(1,2); Yang, Xiao-Xu(1); Zhang, Hen-Jin(1); Li, Gang(1)
Source: Procedia Engineering Volume: 15 Issue: DOI: 10.1016/j.proeng.2011.08.858 Published: 2011
Abstract:Many infrared optical systems usually adopt catoptric systems. Because that the system does not have chromatism and restriction of the working wave. But the coma and astigmatism of off-axis point is large, so the field of view that we can use is restricted. In the needs of infrared early warning system for sea-based, a large field of catadioptric infrared optical system is designed. The optical system breaks the limitation of traditional reflective optical system with small field of view. The system adopts two methods to expand the field of view. One is adding the calibration group before the reflecting system. The other one is that the primary and secondary reflective mirror system are used of Mangin mirror. So the optical system avoids any high-order aspheric surface. In order to match the cold aperture exactly, lens group is inserted after the first image plane. The system's field can reach 8 degree, and the ratio of obscuration is less than 0.4, and also optical transfer function achieves diffraction limit. ? 2011 Published by Elsevier Ltd.
Accession Number: 20115214631568
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Record 336 of
Title:Tracking of moving object based on optical flow detection
Author(s):Chen, Zhiwen(1,2); Cao, Jianzhong(1); Tang, Yao(1); Tang, Linao(1)
Source: Proceedings of 2011 International Conference on Computer Science and Network Technology, ICCSNT 2011 Volume: 2 Issue: DOI: 10.1109/ICCSNT.2011.6182151 Published: 2011
Abstract:Object tracking is one of the most important fields in computer vision and image processing community. In this paper, a novel method for tracking of moving object is proposed. We analyze many methods which are used to segment the Video Object (VO). Then we propose a way, which is based on optical flow, to track object by using the object contour. This algorithm achieves the effective object tracking in spatial position. The experiment result shows that moving object tracking is accurate, rapid and stable by using this algorithm. ? 2011 IEEE.
Accession Number: 20121915002630
