2015
2015
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Record 277 of
Title:Fast frame scanning camera system for light-sheet microscopy
Author(s):Wu, Di(1); Zhou, Xing(1); Yao, Baoli(1); Li, Runze(1); Yang, Yanlong(1); Peng, Tong(1); Lei, Ming(1); Dan, Dan(1); Ye, Tong(2)Source: Applied Optics Volume: 54 Issue: 29 DOI: 10.1364/AO.54.008632 Published: October 10, 2015Abstract:In the interest of improving the temporal resolution for light-sheet microscopy, we designed a fast frame scanning camera system that incorporated a galvanometer scanning mirror into the imaging path of a home-built light-sheet microscope. This system transformed a temporal image sequence to a spatial one so that multiple images could be acquired during one exposure period. The improvement factor of the frame rate was dependent on the number of sub-images that could be tiled on the sensor without overlapping each other and was therefore a tradeoff with the image size. As a demonstration, we achieved 960 frames/s (fps) on a CCD camera that was originally capable of recording images at only 30 fps (full frame). This allowed us to observe millisecond or sub-millisecond events with ordinary CCD cameras. ? 2015 Optical Society of America.Accession Number: 20170603329360 -
Record 278 of
Title:Online anomaly detection in crowd scenes via structure analysis
Author(s):Yuan, Yuan(1); Fang, Jianwu(1,2); Wang, Qi(3)Source: IEEE Transactions on Cybernetics Volume: 45 Issue: 3 DOI: 10.1109/TCYB.2014.2330853 Published: March 1, 2015Abstract:Abnormal behavior detection in crowd scenes is continuously a challenge in the field of computer vision. For tackling this problem, this paper starts from a novel structure modeling of crowd behavior. We first propose an informative structural context descriptor (SCD) for describing the crowd individual, which originally introduces the potential energy function of particle's interforce in solid-state physics to intuitively conduct vision contextual cueing. For computing the crowd SCD variation effectively, we then design a robust multi-object tracker to associate the targets in different frames, which employs the incremental analytical ability of the 3-D discrete cosine transform (DCT). By online spatial-temporal analyzing the SCD variation of the crowd, the abnormality is finally localized. Our contribution mainly lies on three aspects: 1) the new exploration of abnormal detection from structure modeling where the motion difference between individuals is computed by a novel selective histogram of optical flow that makes the proposed method can deal with more kinds of anomalies; 2) the SCD description that can effectively represent the relationship among the individuals; and 3) the 3-D DCT multi-object tracker that can robustly associate the limited number of (instead of all) targets which makes the tracking analysis in high density crowd situation feasible. Experimental results on several publicly available crowd video datasets verify the effectiveness of the proposed method. ? 2014 IEEE.Accession Number: 20150900579295 -
Record 279 of
Title:Generation of low repetition rate sub-nanosecond pulses in doubly QML Nd:Lu0.5Y0.5VO4 and Nd:YVO4 lasers with EO and transmission SSA
Author(s):Zhang, Haijuan(1); Zhao, Shengzhi(1); Zhao, Jia(1); Yang, Kejian(1); Li, Guiqiu(1); Li, Dechun(1); Li, Tao(1); Qiao, Wenchao(1); Wang, Yonggang(2)Source: Optics and Laser Technology Volume: 69 Issue: 1 DOI: 10.1016/j.optlastec.2014.12.017 Published: June 2015Abstract:By employing the mixed crystal Nd:Lu0.5Y0.5VO4 and the single crystal Nd:YVO4 as the laser media, the characteristics of the QML laser doubly modulated by electro-optic (EO) modulator and transmission semiconductor saturable absorber (T-SSA) are studied. Under the same cavity parameters, the properties of the low repetition rate sub-nanosecond pulses generated from Nd:Lu0.5Y0.5VO4 and Nd:YVO4 laser are compared. The experimental results show that Nd:Lu0.5Y0.5VO4 laser can generate shorter pulse width than Nd:YVO4 laser, and meanwhile, needs lower pump power to generate low repetition rate sub-nanosecond pulses. The shortest pulse durations obtained from the doubly QML Nd:Lu0.5Y0.5VO4 and Nd:YVO4 lasers are estimated to be 204 and 294 ps, with the corresponding peak power of 3.4 and 3.04 MW, respectively. ? 2014 Elsevier Ltd.All rights reserved.Accession Number: 20152901039798 -
Record 280 of
Title:Image pair analysis with matrix-value operator
Author(s):Tang, Yi(1); Yuan, Yuan(2)Source: IEEE Transactions on Cybernetics Volume: 45 Issue: 10 DOI: 10.1109/TCYB.2014.2363882 Published: October 2015Abstract:Image pair analysis provides significant image pair priori which describes the dependency between training image pairs for various learning-based image processing. For avoiding the information loss caused by vectorizing training images, a novel matrix-value operator learning method is proposed for image pair analysis. Sample-dependent operators, named image pair operators (IPOs) by us, are employed to represent the local image-to-image dependency defined by each of the training image pairs. A linear combination of IPOs is learned via operator regression for representing the global dependency between input and output images defined by all of the training image pairs. The proposed operator learning method enjoys the image-level information of training image pairs because IPOs enable training images to be used without vectorizing during the learning and testing process. By applying the proposed algorithm in learning-based super-resolution, the efficiency and the effectiveness of the proposed algorithm in learning image pair information is verified by experimental results. ? 2013 IEEE.Accession Number: 20150400458665 -
Record 281 of
Title:High peak power sub-nanosecond mode-locked pulse characteristics of Nd:GGG laser
Author(s):Zhao, Jia(1); Zhao, Shengzhi(1); Li, Tao(1); Li, Yufei(1); Yang, Kejian(1); Li, Guiqiu(1); Li, Dechun(1); Qiao, Wenchao(1); Feng, Chuansheng(1); Wang, Yonggang(2)Source: Optics and Laser Technology Volume: 73 Issue: DOI: 10.1016/j.optlastec.2015.04.025 Published: May 26, 2015Abstract:Based on the dual-loss modulation, i.e. electro-optic (EO) modulator and GaAs saturable absorber, a sub-nanosecond mode-locked pulsed Nd:GGG laser with kHz repetition rates is presented for the first time. The repetition rate (0.5-10 kHz) of this pulsed laser is controlled by the modulation rate of EO modulator, so high stability can be obtained. The sub-nanosecond pulse width depends on the mode-locked pulse underneath the Q-switched envelope in the Q-switched mode-locked (QML) laser and high peak power can be generated. The condition on the generation of sub-nanosecond pulse and the needed threshold power for different modulation rates of EO are given. The average output power, the pulse width and the peak power versus pump power for different repetition rates are demonstrated. The shortest pulse width is 426 ps and the highest peak power reaches 239.4 kW. The experimental results show that the dual-loss modulation technology with EO and GaAs saturable absorber in QML laser is an efficient method to generate sub-nanosecond mode-locked pulsed laser with kHz repetition rates. ? 2015 Elsevier Ltd. All rights reserved.Accession Number: 20152200883484 -
Record 282 of
Title:Pulse contrast improvement for chirped pulse amplification lasers by spectro-temporal filtering
Author(s):Wang, Xianglin(1,2); Wang, Yishan(1,2); Hu, Xiaohong(1); Liu, Yuanshan(1); Zhang, Wei(1); Yang, Zhi(1)Source: Journal of Modern Optics Volume: 62 Issue: 7 DOI: 10.1080/09500340.2014.994682 Published: April 16, 2015Abstract:A spectro-temporal filtering method is proposed to increase the contrast ratio of chirped pulses. The advantages of this method include easy cascading, high transmission, and it can also be used in the high-energy chirped pulse amplifier (CPA) system. The effectiveness of the proposed method was experimentally verified by operating the spectro-temporal filtering method on a Ti:sapphire CPA system and then measuring the contrast ratio of pulse based on optical Kerr gate effect(OKG). The measuring result demonstrated that, after passing through one-stage spectro-temporal filtering system with transmittance up to 70%, the contrast ratio of the pulse was improved by an order of magnitude. ? 2015 Taylor & Francis.Accession Number: 20150700506767 -
Record 283 of
Title:Line-plane-switching infrared bundle for push-broom sensing fiber imaging
Author(s):Zhan, Huan(1,3); Yan, Xingtao(1); Guo, Haitao(1); Xu, Yantao(1); He, Jianli(1); Li, Fu(1); Yang, Jianfeng(1); Si, Jinhai(3); Zhou, Zhiguang(1); Lin, Aoxiang(2)Source: Optical Materials Volume: 42 Issue: DOI: 10.1016/j.optmat.2015.02.008 Published: April 1, 2015Abstract:We reported line-plane-switching infrared (IR) fiber bundle with high-resolution of 0.027 μm-1, small numerical aperture (NA) of 0.20 (±0.02), high filling-factor, and bending radius of around 5.0 mm, i.e. extremely good flexibility. This fiber bundle is made from chalcogenide glass fibers, possessing core (As40S58Se2) of 45 μm, cladding (As40S60) of 50 μm, and error of 1% in diameter. Based on the lens used to demonstrate IR push-broom imaging, the format of matching fiber bundle we chose is 64 × 9 in system to implement 192 × 3 format linear array imaging. By principle-demonstrating system incorporated this fiber bundle coupled with small scale Infrared Focal Plane Array (IRFPA), wide-field and long-array IR push-broom image was successfully demonstrated. ? 2015 Elsevier B.V. All rights reserved.Accession Number: 20150900578167 -
Record 284 of
Title:Ultrafast pump-probe detection of X-ray induced transient optical reflectivity changes in GaAs
Author(s):Wang, Bo(1,2,3); Bai, Yonglin(1,2); Xu, Peng(2); Gou, Yongsheng(2,3); Zhu, Bingli(2); Bai, Xiaohong(1); Liu, Baiyu(2); Qin, Junjun(1)Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 44 Issue: 10 DOI: Published: October 25, 2015Abstract:The optical index modulation was theoretically estimated and demonstrated under short X-ray excitation in low-temperature-grown GaAs (LT_GaAs). Hot-electron thermalization time ?, 2015, Editorial Board of Journal of Infrared and Laser Engineering. All right reserved.Accession Number: 20154701593574 -
Record 285 of
Title:Picosecond resolving detection method and experiment for ultrafast X-ray by modulation of an optical probe
Author(s):Wang, Bo(1,2,3); Bai, Yong-Lin(3); Cao, Wei-Wei(3); Xu, Peng(3); Liu, Bai-Yu(3); Gou, Yong-Sheng(1,2,3); Zhu, Bing-Li(3); Hou, Xun(1)Source: Wuli Xuebao/Acta Physica Sinica Volume: 64 Issue: 20 DOI: 10.7498/aps.64.200701 Published: October 20, 2015Abstract:Diagnostic measurement of single picosecond event in high energy density physics, laser fusion, plasma radiation, and combustion, is of great importance. However, the measuring of the shape of the single X-ray pulse and the synchronization of X-ray and the laser pulse in picosecond resolution is still a great challenge. Restricted by the transit time of electrons, the time-resolution limit of a conventional framing camera based on the microchannel plate is 40 ps. Centered on the full-optical modulation effect of the light-probe, a novel method for X-ray detection of picoseconds temporal resolution based on low temperature GaAs is proposed in this work. The basic physical mechanism of the detector can be explained in both macroscopical and microcosmic ways. In the macroscopical way, the X-ray radiation absorption in the sensor material produces a transient, non-equilibrium electron-hole pair distribution that results in a transient differential change of the local refractive index, which is then sensed by the reflectivity changes of the optical probe beam. In the microcosmic way, X-ray absorption creates photoelectrons and the core level holes are subsequently filled through Auger or fluorescence processes. These excitations ultimately increase conduction and valence band carriers that perturb optical reflectivity. To verify the proposed X-ray detection method, a Fabry-Perot detector is designed, which consists of a 5 μm thick GaAs layer surrounded by a GaAs/AlAs distributed Bragg reflector. The test is carried out on a femtosecond laser facility, where the X-ray source is produced by focusing the 56 fs Ti: Sapphire facility laser, with a central wavelength of 800 nm, onto an aluminum foil. Then the X-ray pulse induces a transient optical reflectivity change in GaAs, which is a powerful tool for establishing the high-speed X-ray detection. The experimental results indicate that this technology can be used to provide X-ray detectors with a temporal resolution of tens of picoseconds. By optimizing the material, the temporal resolution can be enhanced to be less than 1 ps. Through further development, this X-ray detector could provide an insight into previously unmeasurable phenomena in many fields. Future work will focus on developing much faster devices characterizing both the rise and fall time and imaging array technology. ? 2015 Chinese Physical Society.Accession Number: 20154901649527 -
Record 286 of
Title:High-Pulse-Energy All-Normal-Dispersion Yb-Doped Fiber Laser Based on Nonlinear Polarization Evolution
Author(s):Wang, Jun-Li(1); Wang, Xue-Ling(1); He, Bo-Rong(1); Wang, Yong-Gang(3); Zhu, Jiang-Feng(1); Wei, Zhi-Yi(2)Source: Chinese Physics Letters Volume: 32 Issue: 11 DOI: 10.1088/0256-307X/32/11/114202 Published: November 1, 2015Abstract:We report an all-normal-dispersion ytterbium fiber laser mode locked by nonlinear polarization evolution. With a 347-m-long all-fiber ring cavity, a pulse energy of 263 nJ at a repetition rate of 613 kHz is achieved, which is the highest per-pulse energy directly obtained from an all-fiber mode-locked laser doped by ytterbium ions. The compact and operation-robust laser yields a well-shaped spectrum centered at 1032nm with a bandwidth (FWHM) of 4 nm, and the slope efficiency is as high as 27.5%. The proposed low-repetition-rate high-pulse-energy mode-locked fiber laser will be a promising seed for all-fiber chirped pulsed amplification systems. ? 2015 Chinese Physical Society and IOP Publishing Ltd.Accession Number: 20220711654842 -
Record 287 of
Title:High-energy pulse generation using Yb-doped Q-switched fiber laser based on single-walled carbon nanotubes
Author(s):Wang, Jun-Li(1); Wang, Xue-Ling(1); He, Bo-Rong(1); Zhu, Jiang-Feng(1); Wei, Zhi-Yi(2); Wang, Yong-Gang(3)Source: Chinese Physics B Volume: 24 Issue: 9 DOI: 10.1088/1674-1056/24/9/097601 Published: September 1, 2015Abstract:An all-fiber laser using a single-walled carbon nanotube (SWCNT) as the saturable absorber (SA) for Q-switched operation in the 1031 nm region is demonstrated in this work. A lasing threshold as low as 17 mW was realized for continuous wave operation. By further increasing the pump power, stable Q-switched pulse trains are obtained when the pump power ranges from 38 mW to 125 mW, corresponding to repetition rate varying from 40.84 kHz to 66.24 kHz, the pulse width from 2.0 μs to 1.0 μs and the highest single pulse energy of 40.6 nJ respectively. ? 2015 Chinese Physical Society and IOP Publishing Ltd.Accession Number: 20153701265618 -
Record 288 of
Title:InGaAs-MSM photodetector with low dark current
Author(s):Yan, Xin(1,3); Wang, Tao(1); Yin, Fei(1); Ni, Hai-Qiao(2); Niu, Zhi-Chuan(2); Xin, Li-Wei(1); Tian, Jin-Shou(1)Source: Guangzi Xuebao/Acta Photonica Sinica Volume: 44 Issue: 6 DOI: 10.3788/gzxb20154406.0604002 Published: June 1, 2015Abstract:MSM (Mental-Semiconductor-Mental) photodetector has been widely used for its low capacitance and high bandwidth. For example, it can be used for space communication, remote sense and so on. But the development of MSM devices is still hindered by the dark current. In this paper, the 100×100 μm2 InGaAs-MSM photodetector is successfully fabricated. The dark current density is reduced to 0.6 pA/μm2 (5 V) by designing InAlGaAs/InGaAs short period superlattices and InAlAs Schottky barrier enhancement and this improves the SNR. Parameters of the device are characterized as follows: the 3dB bandwidth is 6.8 GHz, the rise time is 58.8 ps, the responsibility is 0.55 A/W at 1550 nm and the external quantum efficiency of the absorption region is 88%. Inhibition mechanisms of the short period superlattices and Schottky barrier enhancement are analyzed. ?, 2015, Chinese Optical Society. All right reserved.Accession Number: 20152901043463