2011
2011
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Record 349 of
Title:Simulation of transmitted light through atmosphere by Monte Carlo method
Author(s):Wu, Zhen(1,2); He, Junfang(2); Wu, Dengke(2); Lü, Baida(1)Source: Qiangjiguang Yu Lizishu/High Power Laser and Particle Beams Volume: 23 Issue: 3 DOI: 10.3788/HPLPB20112303.0779 Published: March 2011Abstract:Different turbid media have different optical parameters such as absorption coefficient, scattering coefficient, anisotropic factor and refractive index. Monte Carlo method was used to simulate the influence of optical parameters on the transmitted photons for light transmitted through different atmospheres. The result shows that the temporal distribution of transmitted light has two peaks corresponding to ballistic photons and diffuse photons, respectively. Every optical parameter affects both the number and time range of ballistic photons, snake photons and diffuse photons. From the angle of statistical simulation, it is explained why atmosphere imaging is difficult when the refractive index of atmosphere is large.Accession Number: 20111613926464 -
Record 350 of
Title:An improved, real-time method for removing the cyclic error of a homodyne interferometer
Author(s):Zhao, Suwen(1,2); Wen, Desheng(1); Zhu, Shaolan(1); Liang, Shitong(1,2)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 8192 Issue: DOI: 10.1117/12.902439 Published: 2011Abstract:The nonlinear error of a homodyne interferometer is presented: the amplitudes, the phase and the offsets. An improved compensation method is introduced since the conventional Heydeman modal' calculation is very time-consuming. First, the "zero drift" problem is solved with the polarization phase-shifting technology; second, a fast algorithm based on the Heydeman method is introduced to calculate the errors; and third, electronic circuit is used to remove the nonlinear errors timely. The test result shows that the nonlinearity of the homodyne interferometer could be reduced to subnanometer over the measuring range of 20cm, and the accuracy can be improved more than tenfold by the dynamic compensation method. ? 2011 SPIE.Accession Number: 20113714320176 -
Record 351 of
Title:Research on underwater single-pixel imaging system
Author(s):Lü, Pei(1,2); Zhou, Ren-Kui(1); He, Jun-Hua(1); Liu, Hai-Ying(3)Source: Guangdianzi Jiguang/Journal of Optoelectronics Laser Volume: 22 Issue: 9 DOI: Published: September 2011Abstract:Owing to the complicated underwater imaging conditions which seriously restrict the development of underwater imaging, especially the remote underwater imaging, a novel underwater imaging framework based on the compressive sensing (CS) is proposed in this paper. The single-pixel camera based on CS is firstly applied to the underwater imaging field. Incorporating the range gate and laser pulse illumination technology, we design the architecture of the underwater CS single-pixel camera system, and construct the measurement matrix and the reconstruction algorithm for this system. By the theory analysis and simulated experiment, the image resolution and the imaging distance of our method are compared with those of range-gate imaging and other underwater imaging methods respectively. The results show that the proposed method not only increases the imaging distance but also improves the image quality.Accession Number: 20114114415123 -
Record 352 of
Title:Design of collective optic system for Thomson scattering measurements on Shenguang-III facility
Author(s):Yan, Yadong(1); Lu, Weitao(1,2); Dong, Xiaona(1); He, Junhua(1); Liu, Xizhan(1); Zhang, Min(1); Zhang, Pengshun(1)Source: Guangxue Xuebao/Acta Optica Sinica Volume: 31 Issue: 6 DOI: 10.3788/AOS201131.0611002 Published: June 2011Abstract:A Thomson scattering signal collective optic system is designed for Thomson scattering measurements on Shenguang-III facility. The optical system is composed of two coupled Cassegrain systems, and has an intermediate image plane. This configuration makes the optical path length long enough to transmit the scattering signal to the camera outside the target chamber. The catadioptric system makes it easier to balance chromatic aberration as there are few ultraviolet materials available. The corrector lens which has a long focal length is replaced by two faster corrector lenses, which make the fabrications and measurements easier. The obscuration ratio is reduced by choosing a proper intermediate magnification. The two refraction lenses beside the intermediate image plane help to couple the two systems well. A reticle is set at the intermediate image plane for system aiming and can be removed before event recording. This system has the total length of more than 5 m, with the maximal elements diameter of 190 mm. The field of view is 2 mm, the magnification is 1.5, and the object space F-number is 10, and the resolution is better than 20μm.Accession Number: 20112814124861 -
Record 353 of
Title:Fabrication and characterization of Yb3+-doped gain-guided index-antiguided fiber with D-shaped inner cladding
Author(s):Li, Weinan(1); Lu, Min(1); Yang, Zhi(1); Guo, Haitao(1); Wang, Pengfei(1); Peng, Bo(1)Source: Journal of the Optical Society of America B: Optical Physics Volume: 28 Issue: 6 DOI: 10.1364/JOSAB.28.001498 Published: June 2011Abstract:Yb3doped gain-guided index-antiguided fibers based on phosphate glasses are drawn using the rod-in-tube technique. These fibers have a circular core with 200 μm diameter and a D-shaped inner cladding with a 630=480 μm diameter for the longer/shorter axis. The negative index profile is present in these fibers, in which the core index of refraction is 0.019% lower than that of the inner cladding. Moreover, their laser amplifier characteristics are experimentally demonstrated, and the method of further improvement in laser performance is suggested. ? 2011 Optical Society of America.Accession Number: 20112514073743 -
Record 354 of
Title:Interferogram spectrum reconstruction using modern spectral estimation
Author(s):Han, Gang(1,2); Liu, Xue-Bin(1); Hu, Bing-Liang(1); Wang, Cai-Ling(1,2)Source: 2011 International Conference on Electronics, Communications and Control, ICECC 2011 - Proceedings Volume: Issue: DOI: 10.1109/ICECC.2011.6066337 Published: 2011Abstract:In this paper, we first discussed basic spectral estimation concepts and algorithms, then pointed out that the conventional spectrum reconstruction algorithm is virtually the same with Blackman-Tukey (BT) algorithm in spectral estimation. Then we use two different method (Auto-Regressive parametric model and eigenvector spectral estimation method) to reconstruct light spectrum from interferogram, and compared the results with conventional method for spectrum reconstruction. From the comparison we concluded that the modern spectrum estimation methods can well be adopted in Fourier Transform (FT) spectrum reconstruction and would perform excellent, especially when to get higher spectrum resolution from a short series of data recorded. Later we discussed the disadvantages and restrictions of the two methods used in the simulation. From these results and discussions, we suggested to implement various new spectral estimation method in FT spectrum reconstruction to get better performance. ? 2011 IEEE.Accession Number: 20114714544621 -
Record 355 of
Title:Improved fourier descriptors in model-based pose estimation
Author(s):Tang, Hui-Jun(1,2); Wen, Jia(1,2); Ma, Cai-Wen(1); Hu, Hai-Bin(3); Zhou, Ren-Kui(1)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 8004 Issue: DOI: 10.1117/12.901770 Published: 2011Abstract:We use Fourier descriptors (FD's) to represent shape in model-based pose estimation. Specific invariance and normalization requirements for shape descriptors concerning to pose estimation are proposed. FD's are improved to meet such requirements. Common issues and techniques for such application are focused on. Starting point of the shape contour is fixed to the upper left corner point. Distance pairs instead of edge coordinate pairs recast the shape sequence. Moving average filtering is proceeded to remove the noises of the shape sequence. Shape sequence is re-sampled to make it definite length. FD's amplitude is normalized to the range of 0 to 1. Variance of sequences between observed and library FD's is defined as the shape matching objective function. For simulation, we use a missile model of Milkshape3d format. Results show that by adopting the improved FD's, we can arrive at a pose estimation practically by randomly optimal search of library FD's. ? 2011 SPIE.Accession Number: 20115214631766 -
Record 356 of
Title:Refluxing of fast electrons in solid targets irradiated by intense, picosecond laser pulses
Author(s):Quinn, M.N.(1); Yuan, X.H.(1,5); Lin, X.X.(2); Carroll, D.C.(1); Tresca, O.(1); Gray, R.J.(1); Coury, M.(1); Li, C.(2); Li, Y.T.(2); Brenner, C.M.(3); Robinson, A.P.L.(3); Neely, D.(3); Zielbauer, B.(4); Aurand, B.(4); Fils, J.(4); Kuehl, T.(4); McKenna, P.(1)Source: Plasma Physics and Controlled Fusion Volume: 53 Issue: 2 DOI: 10.1088/0741-3335/53/2/025007 Published: February 2011Abstract:The propagation of fast electrons produced in the interaction of relativistically intense, picosecond laser pulses with solid targets is experimentally investigated using Kα emission as a diagnostic. The role of fast electron refluxing within the target, which occurs when the electrons are reflected by the sheath potentials formed at the front and rear surfaces, is elucidated. The targets consist of a Cu fluorescence layer of fixed thickness at the front surface backed with a propagation layer of CH, the thickness of which is varied to control the number of times the refluxing fast electron population transits the Cu fluorescence layer. Enhancements in the Kα yield and source size are measured as the thickness of the CH layer is decreased. Comparison with analytical and numerical modelling confirms that significant refluxing occurs and highlights the importance of considering this phenomenon when deriving information on fast electron transport from laser-solid interaction experiments involving relatively thin targets. ? 2011 IOP Publishing Ltd.Accession Number: 20110613651240 -
Record 357 of
Title:Noise immunity research on the measurement method of image motion of the space camera based on optical correlator
Author(s):Fan, Chao(1); Li, Ying-Cai(2); Jin, Ting(1); Fu, Hong-Liang(1)Source: Yuhang Xuebao/Journal of Astronautics Volume: 32 Issue: 12 DOI: 10.3873/j.issn.1000-1328.2011.12.025 Published: December 2011Abstract:To research the influence of the noise on the measurement accuracy of the image motion of the space camera when using the optical joint transform correlator (JTC), the background noise and the pattern noise are added to the JTC respectively firstly. Then the measurement errors at different noise levels for the five kinds of different processing methods are emulated, and the validity of the image motion measured by the JTC is verified by an experimental platform. The results show that the measurement accuracy for the method of power spectrum subtraction and binaryzation with zero threshold is better compared with the other processing methods, the measurement error is no more than 0.12 pixel for the input image with SNR=1 and the background noise, thus meeting the operating requirement of the space camera completely.Accession Number: 20120214676488 -
Record 358 of
Title:Incipient fault detection for aero-engine rotor based on frequency compression of stochastic resonance
Author(s):Wang, Guo-Fu(1,2); Zhang, Hai-Ru(1); Zhang, Fa-Quan(1); Ye, Jin-Cai(1)Source: Hangkong Dongli Xuebao/Journal of Aerospace Power Volume: 26 Issue: 3 DOI: Published: March 2011Abstract:A frequency compression based on stochastic resonance (SR) for detecting incipient fault weak signal was presented because of the benefits of SR for detecting weak signals. The frequency limitation of SR was eliminated by introducing frequency compression. The incipient fault signal was detected from heavy noise under the condition of adiabatic approximation. Theoretical analysis and experiment results show that: to deal with the unknown incipient fault signals mixed with heavy noise, the mixed signal is compressed continuously to achieve a suitable frequency and then input to SR system. According to the change of resonance spectral peak value, the unknown incipient fault frequency can be obtained from heavy noise by inverse transform algorithm. Compared with traditional methods, the computing speed is increased by four magnitudes. The target signal is detected under -50 dB.Accession Number: 20112013987451 -
Record 359 of
Title:A novel de-noising method based on Independent Component Analysis(ICA) for DMD based Hadamard Transform Spectral Imager
Author(s):Qian, QingMing(1,2); Hu, BingLiang(1); Xu, Jun(1,2); Liu, CaiFang(1,2); Tan, XiaoBing(1,2)Source: Proceedings of 2011 Cross Strait Quad-Regional Radio Science and Wireless Technology Conference, CSQRWC 2011 Volume: 2 Issue: DOI: 10.1109/CSQRWC.2011.6037236 Published: 2011Abstract:A new de-noising method based on Independent Component Analysis (ICA) is proposed for imaging characteristics of Digital Micro-mirror Device (DMD) based Hadamard Transform Spectral Imager. As the ubiquitous Gaussian white noises caused by diffractions and other unknown factors in the optical instrument severely confine the usage of the spectral image. ICA is a powerful technique in recovering latent independent sources given only from the mixtures. Based on the fundamental analyzing mode of ICA, the projection of the spectral image is calculated under the transform bases. Then the de-noising processing is carried out by using the soft threshold arithmetic operators. The rebuild spectral image can be acquired by an inverse transform at last. Experiments demonstrate that the proposed ICA algorithm achieves a higher peak signal noise ration (PSNR) and subjective vision effects compared with traditional spectral image de-noising methods. ? 2011 IEEE.Accession Number: 20114414464506 -
Record 360 of
Title:Study on characteristic of Yb3+-gain guided index-antiguided fiber
Author(s):Li, Weinan(1); Lu, Min(1); Peng, Bo(1)Source: Guangxue Xuebao/Acta Optica Sinica Volume: 31 Issue: SUPPL.1 DOI: 10.3788/AOS201131.s100109 Published: June 2011Abstract:The core glass and cladding glass of gain guided index-antiguided (GGIAG) fiber doped with Yb3+ are prepared and Yb3+GGIAG fiber with core diameter of 120 μm, inner cladding diameter 220 μm and outer cladding diameter 260 μm is drawn by the rod-in tube technique. Yb3+GGIAG fiber has a lower core refractive index than the surrounding cladding's, Δn=-0.00094. The beam quality factors in both horizontal and vertical directions are observed, Mx2≈2.724 and My2≈2.642 when signal light (at 1040 nm) with single mode is propagating in Yb3+GGIAG fiber with different length, which indicates single mode approximation behavior of Yb3+GGIAG fiber. The mode field diameter of Yb3+GGIAG is calculated to be more than 150 μm.Accession Number: 20113114199058