Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences
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Imaging ellipsometer with large field of view
No full textA polarizer-compensator- sample-analyzer (PCSA) imaging ellipsometer with large field of view is presented. The sample is imaged on a CCD sensor by a telecentric imaging system and its tilt is monitored by an optical autocollimator. The sample, the telecentric imaging system and the CCD sensor satisfy the Scheimpflug condition. In measurement, the light extinction measurement method and the four quadrants average method are used to improve the accuracy. In experiments, a chromium thin film sample is measured by the imaging ellipsometer and a spectroscopic ellipsometer. The measurement results by two ellipsometers are consistent. The usefulness of the imaging ellipsometer is verified
血管内扫频光学相干层析成像系统
No full text血管内光学相干层析成像(IV-OCT)是光学相干层析成像技术在内窥成像方面的一种重要应用,其系统样品臂利用成像探头进入血管对血管壁进行成像。临床研究表明,检测厚度小于65μm的薄纤维帽是发现易损斑块的关键,而易损斑块的早期发现、早期干预是降低心血管疾病发病率和死亡率的关键。目前只有IV-OCT能够对血管中小于65μm的薄纤维帽厚度进行检查,因此该技术自发明以来便成为检测血管壁易损斑
扫频光学相干层析成像系统的光谱标定方法
No full text光学相干层析成像(Optical Coherence Tomography,OCT)是一种非侵入、高分辨率、可在体检测生物组织内部微结构信息的生物医学光学成像技术。OCT可分为时域OCT和频域OCT,而频域OCT又可分为基于光谱仪的SDOCT和基于扫频光源的SSOCT。在频域OCT中,样品深度和光源波数是一对傅里叶变换对,将采集的干涉信号对波数进行傅里叶变换(FFT),获得样品的层析结构图像。非波数等间隔的干涉信号直接
3D human face reconstruction based on band-limited binary patterns
No full textNational Natural Science Foundation of China [61308073]; Science and Technology Commission of Shanghai Municipality [15JC1403500]Face recognition technology has great prospects for practical applications. Three-dimensional (3D) human faces are becoming more and more important in consideration of the limits of two-dimensional face recognition. We propose an active binocular setup to obtain a 3D colorful human face using the band-limited binary patterns (BBLP) method. Two grayscale cameras capture the BBLP projected onto the target of human face by a digital light processing (DLP) projector synchronously. Then, a color camera captures a colorful image of the human face. The benefit of this system is that the 3D colorful human face can be obtained easily with an improved temporal correlation algorithm and the precalibration results between three cameras. The experimental results demonstrated the robustness, easy operation, and the high speed of this 3D imaging setup
An approach for generating the first order structure of multi-movable zoom lens
No full textScience and Technology Commission of Shanghai Municipality [14YF1406300]; International Science & Technology Cooperation Program of China [2011DFR10010]; National Natural Science Foundation of China [61377005]This work provides a method to obtain the first order structure of a zoom system based on particle swarm optimization (PSO) algorithm. The kinematic rule of a zoom system with fixed image plane is described by differential equations. PSO algorithm is introduced to solve the differential equations with considering both the merit functions and the boundary constraint. The smooth of the kinematic function of the zoom system is checked for considering the fabrication feasibility. Examples with two types of zoom system are presented for verifying the proposed method. This approach provides a powerful and practical tool for construction of a zoom structure. (C) 2015 Elsevier B.V. All rights reserved
A facile method to fabricate superamphiphobic polytetrafluoroethylene surface by femtosecond laser pulses
No full textNational Natural Science Foundation of China [61178024, 11374316]; National Basic Research Program of China [2011CB808103]We report a simple method to fabricate superamphiphobic polytetrafluoroethylene (PTFE) surfaces by femtosecond laser direct irradiation. After femtosecond laser direct writing, a dual-scale composite structure combined a groove-like microstructure with a lamellar submicron structure forms on the PTFE surface, enhancing its hydrophobic properties with a contact angle increasing from 109 degrees to 156.88 degrees, as well as exhibiting transition from intrinsic oleophilicity to superoleophobicity. Meanwhile, the wett-ability of the surface can be tuned by changing the roughness and the interval between two adjacent micro-grooves. Furthermore, we also explain the relationship between the interval width and the contact angle using the Cassie-Baxter model. (C) 2015 Elsevier B.V. All rights reserved
A method for selecting training samples based on camera response
No full textNational Basic Research Program of China (973 Program) [2015CB352004]; National Natural Science Foundation of China [61405115]; Natural Science Foundation of Shanghai [14ZR1428400]; Innovation Project of Shanghai Municipal Education Commission [14YZ099]In the process of spectral reflectance reconstruction, sample selection plays an important role in the accuracy of the constructed model and in reconstruction effects. In this paper, a method for training sample selection based on camera response is proposed. It has been proved that the camera response value has a close correlation with the spectral reflectance. Consequently, in this paper we adopt the technique of drawing a sphere in camera response value space to select the training samples which have a higher correlation with the test samples. In addition, the Wiener estimation method is used to reconstruct the spectral reflectance. Finally, we find that the method of sample selection based on camera response value has the smallest color difference and root mean square error after reconstruction compared to the method using the full set of Munsell color charts, the Mohammadi training sample selection method, and the stratified sampling method. Moreover, the goodness of fit coefficient of this method is also the highest among the four sample selection methods. Taking all the factors mentioned above into consideration, the method of training sample selection based on camera response value enhances the reconstruction accuracy from both the colorimetric and spectral perspectives
Effective dispersion compensation of variable-linewidth fiber amplifier by single-multilayer dielectric grating
No full textNational High Technology Research and Development Program of China [2014AA041901]; NSAF Foundation of the National Natural Science Foundation of China [U1330134]; National Natural Science Foundation of China [61308024]We achieve effective dispersion compensation by employing a single-multilayer dielectric diffraction grating and a variable-linewidth fiber amplifier. Both theoretical and experimental studies on the diffracted beam quality have been performed. The experimental results show that when the linewidth reaches 0.41 nm the beam quality in the dispersive plane reduces dramatically from 5.4 for the first-time diffracted beam to 2.08 for the second-time diffracted beam. This dispersion compensation technology relaxes the requirement on the linewidth of the incident beam source, which is beneficial for high-brightness spectral beam combining
Ultra-wide wavelength tuning of a cascaded Raman random fiber laser
No full textNational Natural Science Foundation of China (NSFC) [61378026, 61505229]An ultra-broadband tunable cascaded Raman random fiber laser pumped by a tunable (1020-1080 nm) ytterbium-doped fiber laser is investigated. By continuously adjusting the pump laser wavelength, the Raman random laser tunes accordingly due to the Raman gain competition. By increasing the pump power, up to the 5th order Raman random laser is achieved. As a result, 300 nm of continuous wavelength tuning from 1070 to 1370 nm is achieved by adjusting the pump wavelength and power altogether. The highest output power is 1.8 W at 1360 nm with an optical efficiency of 15% from 1080 nm. To the best of our knowledge, this is the widest wavelength tuning range reported for a random fiber laser so far. (C) 2016 Optical Society of Americ
Acousto-Optically Q-Switched and Vortex NdYAG Laser by Using Circular Dammann Grating for Annular Pumping
No full text研究了圆环达曼光栅(CDG)整形的环形光抽运的声光调Q NdYAG激光器。该激光器的腔体由激光晶体、声光调制器以及平面输出耦合镜组成。所用抽运源为光纤耦合808nm半导体激光器,其发射光经过CDG发生一级衍射,产生的环形光场强度分布用于端面抽运NdYAG激光晶体。实验获得了高光束质量、线偏振、且具有螺旋相位的主动调Q脉冲光输出。当吸收抽运功率为5.6W、声光调制器工作频率为5kHz时,激光脉冲的平均功率为470mW,峰值功率达到588W,脉冲宽度为160ns。国家自然科学基金An acousto-optically Q-switched vortex NdYAG laser by annular pumping of circular Dammann grating (CDG)shaping is investigated.The cavity of the laser is composed of a laser crystal,an acousto-optical modulator and a planar output coupling mirror.The pump source is a fiber coupling semiconductor laser of 808nm.The annular intensity distribution of pump light is formed by the first-order diffraction of a CDG with high diffraction efficiency,which is used to end pumped NdYAG laser crystal.The active Q-swith pulse laser is obtained with high optical quality,linear polarization and spiral phase.The obtained power of laser pulse is 470mW,the peak power of laser pulse reaches 588Wand pulse width is 160ns,when the absorbed pump power is 5.6Wand the frequency of acousto-optical modulator is 5kHz