2012
2012
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Record 289 of
Title:Research and approach on video stabilization algorithm
Author(s):Liao, Jiawen(1); Cao, Jianzhong(1); Tang, Linao(1); Wang, Hua(1)Source: Proceedings of 2012 International Conference on Image Analysis and Signal Processing, IASP 2012 Volume: Issue: DOI: 10.1109/IASP.2012.6425047 Published: 2012Abstract:This paper presents a video stabilization algorithm based on Scale Invariant Feature Transform and the improved RANdom SAmple Consensus (RANSAC) algorithm. Feature points of the video images are extracted using the SIFT algorithm, and then a compensation matrix is obtained using the improved RANSAC algorithm. Pre-detection is used to accelerate the computation by discarding those temporary models that are not candidate models. The experiment result shows that this algorithm largely reduces the amount of computation, as well as improves the speed of video stabilization without changing the accuracy notably. ? 2012 IEEE.Accession Number: 20131016092695 -
Record 290 of
Title:Highly stable, passively mode-locked fiber laser with low pump power for subpicosecond pulse generation
Author(s):Tang, Dingkang(1,2); Zhang, Jian-Guo(1,3); Liu, Yuanshan(1)Source: Laser Physics Volume: 22 Issue: 10 DOI: 10.1134/S1054660X12100052 Published: October 2012Abstract:We present the design of highly stable, passively mode-locked fiber lasers which are based on a simple configuration and require a low pump power for the generation of optical pulses with subpicosecond pulsewidth. Our designed fiber laser uses a semiconductor saturable absorber mirror to realize the self-starting, passive mode locking at a low pump power of 29 mW, with which a stable optical pulse train is obtained at the fundamental repetition rate of 52.5 MHz and the central wavelength of 1557 nm. The output modelocked optical pulses have a pulsewidth of 881 fs and an average output power of 1.78 mW, respectively. ? Pleiades Publishing, Ltd., 2012.Accession Number: 20124615674502 -
Record 291 of
Title:Research and implementation of brushless DC motor drive controller based on FPGA
Author(s):Lei, Yangjie(1); Zheng, Jinkun(1); Yan, Aqi(1); Cao, Jianzhong(1); Zhou, Zuofeng(1); Chen, Weining(1); Zhang, Hui(1); Liu, Guangsen(1); Wang, Hao(1); Tang, Linao(1)Source: Advanced Materials Research Volume: 580 Issue: DOI: 10.4028/www.scientific.net/AMR.580.387 Published: 2012Abstract:In the paper, a design method of brushless DC motor drive controller and its pure hardware implementation on FPGA is proposed. First, we design each module of the controller, including the proportional integral (PI) speed and current PI regulator, current detection module, position and speed detection module, PWM generator and commutation control module, which focuses on a PI regulator and the current detection section. Then, the logical design structure diagrams and the timing simulation waveforms are given. Finally, the overall system circuit are implemented on FPGA which can improve system integration, stability and reliability and easier to modify and upgrade. Simulation and experiment results indicate that this controller design method is reasonable and has stable operation. ? (2012) Trans Tech Publications, Switzerland.Accession Number: 20124815717736 -
Record 292 of
Title:3-D noise model and evaluation of scientific grade CCD
Author(s):Liu, Lili(1); Da, Zhengshang(1); Tian, Xinfeng(1); Li, Kun(1); Chen, Yongquan(1)Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 41 Issue: 4 DOI: Published: April 2012Abstract:To evaluate the influences resulted by CCD noise in laser near field distribution measurement, 3-D noise model was used to analyze the characters of CCD noise which was classified into spatial noise and temporal noise. Spatial noise was used to evaluate influences resulted by no-uniformity between different pixels, and temporal noise was used to evaluate influences resulted by multiple measurements. To measure system noise, CCD 3-D noise measurement system was designed, it was composed of semiconductor laser, integrating sphere, attenuating plate, scientific grade CCD, optical power meter and computer. Integrating sphere was used to unify the input laser and CCD was connected to one of its output ports. Optical power meter was used to record optical power accepted by CCD which could be changed by adjusting attenuating plate. CCD output data to export PC were used to analyze CCD noise. By testing for one type of scientific grade CCD, it was concluded that spatial noise and temporal noise were signal-dependent terms and followed normal distribution. The relationship model between standard deviation of noise and signal was studied, and one way of identifying the parameters of model was proposed. The experiments verified that this model was effective.Accession Number: 20122415111468 -
Record 293 of
Title:Design and simulation of tilt mirror for space image stabilized system
Author(s):Xu, Guangzhou(1); Ruan, Ping(1); Li, Fu(1); Lu, Di(1); Ge, Wei(1)Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 41 Issue: 4 DOI: Published: April 2012Abstract:As the core part of space image stabilized system, the main constraint of design and assembly for tilt mirror is tilt mirror component's performance parameter and the influence on mirror surface under the external load. According to the design constraint, the material of tilt mirror and fixing structure was selected and the lightweight design for tilt mirror and fixing structure was to be processed. In order to check the influence law of tilt mirror surface under external load, the assembly of tilt mirror was analyzed using contact nonlinear finite element method. The rigid displacement was eliminated by using opto-mechanical integrated simulation method based on Zernike polynomials and the surface parameter of tilt mirror after eliminating rigid displacement was gained. The simulation result demonstrates the rigid displacement obviously exists under the external load; piston term occupies the main aspects of the whole rigid displacement under the pretightening force; when the gravity is in the optical direction, the static load plays the dominating role on the surface change, otherwise the dynamic load plays the leading role under the dynamic load. On the basis of simulation, the tilt mirror parts were manufactured and assembled and the surface was also tested after assembling. The test result illustrates tilt mirror surface can satisfy the design requirement and also shows the rationality of the design of tilt mirror and validity of the simulation method.Accession Number: 20122415111445 -
Record 294 of
Title:Design of 8× dual field of view zoom and large relative aperture infrared hybrid refractive-diffractive system
Author(s):Xu, Liang(1); Zhao, Jianke(1); Zhou, Yan(1); Liu, Feng(1)Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 41 Issue: 8 DOI: Published: August 2012Abstract:A set of 8-12 μm infrared hybrid refractive-diffractive dual field of view zoom system was designed based on the triturating requirement of the photoelectric tracking system. The system broke through the flaw that the conventional system always had small relative aperture, small zoom ratio and complex structure. A simple dual field of view system with large relative aperture and high zoom ratio was designed. DOE was used to calibrate the chromatic aberration and temperature difference by its internal characteristics. Ge and ZnS were utilized to calibrate the spherochromatic aberration. The final designed result was that F# was 1.1(relative aperture), and the zoom ratio is 8×. The result indicates that the MTF is above 0.55 abroad and narrow field of view which is at the spatial frequency of 18 lp/mm, and the MTF is approaching to the diffraction limit. The energy permeance ratio is greater than 78.5% when the system receiving radius in the detecting sensor is smaller than 15 μm. It shows that the imaging quality of the zoom system is very good, and it calibrates the temperature difference in real circumstance of the application.Accession Number: 20124415622964 -
Record 295 of
Title:Catadioptric dual-zone Fresnel condenser with super relative aperture
Author(s):Wang, Jing(1); Qu, En-Shi(1); Yang, Hong-Tao(1); Cao, Jian-Zhong(1); Fan, Zhe-Yuan(1)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 8333 Issue: DOI: 10.1117/12.916939 Published: 2012Abstract:The paper introduces a kind of super relative aperture condenser which has the strcuture of spherical Fresnel surface with catadioptric projection optical system, it would improve the condensing capacity and light efficiency substantially. The condenser is composed of two sections with a center and an outer ring, the center region adopted the basic structure of the Fresnel lens with the Fresnel of laplace domain continuous curve transmission type, and the outer structure which achieve light collimating or focusing by total reflection is stepped. The paperstudies the parameter and alforithm of this catadioptric dual-zone Fresnel condenser and gives the surface data of total reflection region. Based on the method of establishing the entity model, we design a set of lens with the relative aperture F=0.3, simulate the condensing ability of the lens by the simulation software, and verify that the lens have a very good effect on focusing. ? 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).Accession Number: 20121014832669 -
Record 296 of
Title:Detectability calibration of lunar-based optical telescope on ground
Author(s):Xu, Liang(1); Zhao, Jian-Ke(1); Xue, Xun(1); Liu, Feng(1); Hu, Dan-Dan(1)Source: Guangxue Jingmi Gongcheng/Optics and Precision Engineering Volume: 20 Issue: 5 DOI: 10.3788/OPE.20122005.0972 Published: May 2012Abstract:The Signal-to-noise Ratio (SNR) of star-level detection and the energy concentration of a dispersed spot for an lunar-based Optical Telescope (LOT) are tested by using a simulation experiment on ground to verify its detection capability. Unlike the conventional methods that use the effect of CCD hardware parameters on the noise to test the SNR, the new test method directly uses the observation information to compute the SNRs of star targets and the tested uncertainty of object SNRs can be better than 8%. In the test of energy concentration, the centroid algorithm is used to computer the center of the dispersed spot and a Gaussian fitting method is proposed to fit the curve of the energy distribution. The Gaussian fitting method can significantly improve the detection precision of the energy concentration for the dispersed spot, and the testing precision has been improved by 10%. Finally, the detection capability of +15Mv of the LOT is verified by an experiment on the SNR of star level detection and the energy concentration of dispersed spot for the LOT.Accession Number: 20122615178963 -
Record 297 of
Title:Thermal modeling and analysis of high power semiconductor laser arrays
Author(s):Zhang, Zhiyong(1); Zhang, Pu(1); Li, Xiaoning(1,2); Xiong, Lingling(1); Liu, Hui(1); Nie, Zhiqiang(1); Wang, Zhenfu(1); Liu, Xingsheng(1,3)Source: ICEPT-HDP 2012 Proceedings - 2012 13th International Conference on Electronic Packaging Technology and High Density Packaging Volume: Issue: DOI: 10.1109/ICEPT-HDP.2012.6474681 Published: 2012Abstract:With the continuous increase of the output power of semiconductor laser array, the heat generation in the active region also increases continuously, which influences the performances and lifetime of semiconductor laser array seriously. In order to improve the performances and lifetime, understanding of the thermal behavior of high power semiconductor laser array packages and optimizing the thermal performance are crucial. By means of numerical analysis, a three-dimensional thermal model has been established, and the static and transient thermal characteristics in continuous-wave (CW) and quasi-continuous-wave (QCW) modes also have been studied systematically for a hard solder, conduction-cooled-packaged 808nm semiconductor laser array. Based on the thermal modeling and analysis, the approaches to reduce thermal resistance have been proposed. The results show that: compared with copper-tungsten (CuW), adopting the copper-diamond composite material as the submount can decrease the thermal crosstalk behavior between emitters, and reduce the thermal resistance by about 30%. In addition, a novel thermal design for the packaging structure of the mounting heat-sink is demonstrated, which has the ability of reducing the thermal resistance of the devices significantly. ? 2012 IEEE.Accession Number: 20131416160755 -
Record 298 of
Title:Design of optical element combining Fresnel lens with microlens array for uniform light-emitting diode lighting
Author(s):Wang, Guangzhen(1,2); Wang, Lili(1); Li, Fuli(2); Kong, Depeng(1)Source: Journal of the Optical Society of America A: Optics and Image Science, and Vision Volume: 29 Issue: 9 DOI: 10.1364/JOSAA.29.001877 Published: September 1, 2012Abstract:One kind of optical element combining Fresnel lens with microlens array is designed simply for LED lighting based on geometrical optics and nonimaging optics. This design method imposes no restriction on the source intensity pattern. The designed element has compact construction and can produce multiple shapes of illumination distribution. Taking square lighting as an example, tolerance analysis is carried out to determine tolerance limits for applying the element in the assembly process. This element can produce on-axis lighting and off-axis lighting. ? 2012 Optical Society of America.Accession Number: 20123915471540 -
Record 299 of
Title:Hard solder 20-kW QCW stack array diode laser
Author(s):Li, Xiaoning(1,2); Kang, Lijun(3); Wang, Jingwei(3); Zhang, Pu(1); Xiong, Lingling(1); Liu, Xingsheng(1,3)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 8241 Issue: DOI: 10.1117/12.909772 Published: 2012Abstract:With the increasing applications of high power semiconductor lasers in industry, advanced manufacturing, aerospace, medical systems, display, entertainment, etc., semiconductor lasers with high power and high performances are required. The performance of semiconductor lasers is greatly affected by packaging structure, packaging process and beam shaping. A novel macro channel cooler (MaCC) for stack array laser with good heat dissipation capacity and high reliability is presented in this work. Based on the MaCC package, a high power stack array diode laser is successfully fabricated. A series of techniques such as spectrum control and beam control are used to achieve narrow spectrum and high beam quality. The performances of the semiconductor laser stack array are characterized. A high power 20kW QCW hard solder packaged stack array laser is fabricated; a narrow spectrum of 3.94 nm and an excellent rectangular beam shape are obtained. The lifetime of the stack array laser is tested as well. ? 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).Accession Number: 20121014830325 -
Record 300 of
Title:Controllable cascaded four-wave mixing by two chirped femtosecond laser pulses
Author(s):Zhang, H.(1); Zhou, Z.(2); Lin, A.(2); Cheng, J.(1); Liu, H.(1); Si, J.(1); Chen, F.(1); Hou, X.(1)Source: Applied Physics B: Lasers and Optics Volume: 108 Issue: 3 DOI: 10.1007/s00340-012-5038-1 Published: September 2012Abstract:We investigated the generation of cascaded fourwave mixing (CFWM) sidebands by using two crossing chirped femtosecond pulses with the same central wavelength in tellurite glass (Te glass). Sidebands of broadband spectra, which contained non-degenerate and degenerate CFWM signals, were obtained at different delay time between two input pulses. The CFWM sidebands observed on different sides of input beams were flexibly controlled by adjusting the delay time. ? Springer-Verlag 2012.Accession Number: 20124615661357