Signal Processing Scheme for Increasing System Resolution in Determination of the Scattering Position in an OCT System

1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　　Ｉｔｉｓａｄｉｆｆｉｃｕｌｔａｎｄｃｈａｌｌｅｎｇｉｎｇｐｒｏｂｌｅｍｉｎｍｏｄｅｒｎｏｐｔｉｃａｌｔｅｃｈｎｏｌｏｇｙｔｏｏｂｔａｉｎｔｈｅｎｏｎｉｎｖａｓｉｖｅｎｅａｒｉｎｆｒａｒｅｄｉｍａｇｉｎｇｏｆｍｉｃｒｏｓｔｒｕｃｔｕｒｅｉｎｏｂｓｃｕｒｅｍｅｄｉａｄｕｅｔｏｔｈｅｅｘｉｓｔｅｎｃｅｏｆｍｕｌｔｉｐｌｅｓｃａｔｔｅｒｉｎｇ ,ｗｈｉｃｈｄｅｇｒａｄｅｓｔｈｅｃｏｎｔｒａｓｔａｎｄｓｐａｔｉａｌｒｅｓｏｌｕｔｉｏｎｏｆｉｍａｇｉｎｇ ｇｒｅａｔｌｙ[1,2 ] .Ｏ…     

Enhanced Temperature Sensing by Multi-Mode Coupling in an On-Chip Microcavity System

The microcavity is a promising sensor platform, but any perturbation will disturb its linewidth, cause resonance shift or splitting. However, such sensing resolution is limited by the cavity's optical quality factor and mode volume. Here, an on-chip integrated microcavity system is proposed and demonstrated that the resolution of a self-referenced sensor can be enhanced with multi-mode coupling. In experiments, inter-mode coupling strength is carefully optimized with a pulley waveguide and observed a resolution improvement of nearly 3 times in the frequency domain. While experiencing small refractive index change tuned by temperature, mode-coupled system shows a 7.2 times sensitivity enhancement that is than the uncoupled system on the same chip and a very significant lineshape contrast ratio change as great reference for minor frequency shifts. This approach will help design microcavity sensors to improve detection sensitivity and resolution under limited manufacture precision.     

反射式光纤共焦扫描成像的研究

建立了反射式光纤共焦扫描成像系统,分析了光纤－集光透镜参数Ａ及物透镜有效数值孔径等对系统成像分辨率的影响。并在此基础上选择了合适参数的透镜,获得了优化的反射式光纤共焦扫描成像系统,测试结果表明,该系统具有亚微米级横向成像能力,微米级向层析能力,成像稳定性那,它将应用于材料及生物组织三维成像检测中。     

FFT-LB Modeling of Thermal Liquid-Vapor System

We present an improved lattice Boltzmann(LB) model for thermal liquid-vapor system.In the new model,the Windowed Fast Fourier Transform(WFFT) and its inverse are used to calculate both the convection term and the external force term of the LB equation.By adopting the WFFT scheme,Gibbs oscillations can be damped effectively in unsmooth regions while high resolution feature of the spectral method can be retained in smooth regions.As a result,spatial discretization errors are dramatically decreased,conservation of the total energy is much better preserved,and the spurious velocities near the liquid-vapor interface are significantly reduced.The high resolution,together with the low complexity of the WFFT approach,endows the proposed method with considerable potential for studying a wide class of problems in the field of multiphase flows.     

红外扫描和频振动光谱系统的激光线宽与光谱分辨率

本文报道了一个简化的利用可见光和红外光带宽来计算和频光谱分辨率的公式. 公式显示和频振动光谱的Voigt线宽可以通过振动模式的均匀线宽(洛伦兹线宽)、非均匀线宽(高斯线宽)、红外光与可见光的高斯线宽计算获得. 利用本实验室新搭建的频率分辨及偏振分辨的皮秒和频光谱系统验证了该公式的准确性. 实验结果显示,本激光系统获取的红外光的高斯线宽为1.5 cm^-1. 本激光系统的光谱分辨率约为4.6 cm^-1,结果与胆固醇单层膜光谱获取的光谱分辨率(3.5~5 cm^-1)基本一致.     

基于浏览器的Kicker踢轨控制系统软件设计

兰州重离子加速器冷却储存环(HIRFL-CSR)现有的Kicker踢轨控制系统为多板结构,需要安装多个控制软件对其进行参数配置,系统的时间分辨率为5 ns;新研制的踢轨控制系统采用单板结构,将系统的时间分辨率提高至2.5 ns。界面设计采用流行的浏览器/服务器模式,在嵌入式系统中移植Boa Web服务器,用来实现浏览器和底层硬件的通信,操作人员通过浏览器即可对Kicker控制系统各项参数进行配置。实验验证,该软件系统具有免安装、操作简单、易于与其他软件系统集成的优点,能够满足踢轨控制系统的需要。The existed Kicker Control System for HIRFL-CSR in Lanzhou is multi-board and many software interfaces have been installed to have the parameters to be con gurated. The time resolution for the beam to be identi ed is 5 ns. The newly designed Kicker Control System is designed with single-board architecture and raises the system time resolution to 2.5 ns. The B/S model has been applied to upgrade the software interface.In order to realize the target, we use the browser to communicate with hardware for the purpose of con guring the controller, the Boa web server has been transplanted into embedded system. The experiments showed that this software system is easy to use and integrate with other control system, without setup process, and is of great research value and popularization.     

一种精密触发定时系统

提出并研制了一种精密触发定时系统.它主要利用多个光电倍增管和闪烁体组成的探测系统,对同一事件的时间信息进行多次测量.通过对多个时间信息的离线处理,来获得时间分辨为57ps的精密触发定时系统.该系统可以用于快时间探测器性能的研究.     

微细光刻中部分相干系统成像研究

分析了投影光刻系统中部分相干成像的过程，结果表明部分相干成像的像强是相干成像的像强对光源上每一点互相干强度的权重和，得出了近年来改进照明条件提高分辨力的物理本质，部分相干成像系统是一个空间频率可变的系统，频率的调制是通过照明函数的变化来实现的提出了进一步提高光刻分辨力的新途径。     

预放大数字全息系统的成像分辨率分析

基于菲涅耳衍射理论,详细推导了预放大数字全息系统的点扩散函数表达式,并由此分析了该成像系统的分辨率.通过分别对整个系统、显微物镜以及CCD的点扩散函数幅值的计算机模拟,讨论了显微物镜与CCD分辨率之间的匹配问题.指明了现有文献中一些含糊说法.结果表明:恰当选择记录参量,使MO的成像分辨率接近于其极限分辨率,同时还要使CCD在满足抽样条件与再现像分离条件的情况下,再现像分辨率等于或略高于MO的分辨率.     

一种测量电视跟踪系统摄像头分辨率的新方法

提出了利用“辐射状分辨率图案”测量电视跟踪系统摄像头分辨率的新方法，它取了“分辨率板法”的优点，避免了目视分辨率板法的缺点。介绍了一种基于图像时空域特征的数字化测试系统。该系统利用图像采集卡实时采集电视跟踪系统摄像头输出的视频图像信号，通过数据和图像处理后计算出摄像头的分辨率。测试过程实现了自动化，试验重复性好，测试结果客观可靠，能够更加合理、准确地反映电视跟踪系统摄像头的成像质量。     

基于拉曼散射的光纤分布式温度测量系统的空间分辨力

基于自发拉曼散射的光纤分布式温度测量系统是一种真正的分布传感系统且已商品化。本文从光学的角度出发较详细地分析了此类系统的空间分辨力理论极限及其影响因素。分析表明， 对于一个１ ｋｍ 的多模系统， 若接收机的最小可分辨光功率优于３．５ ｐＷ， 则其在０～４００℃的范围内且温度精度为±１℃时的空间分辨力极限为２ ｃｍ ； 当接收机的最小可分辨光功率小于０．５ ｐＷ， 单模系统的空间分辨力极限优于对应的多模系统。因此， 把基于自发拉曼散射机理的光纤分布式温度测量系统用于短距离高分辨力的系统理论上是可行的。     

湍流大气成像系统分辨率的研究

采用基于Kolmogorov 1941串级湍流模型建立的调制湍流折射率谱模型、简单透镜成像系统传递函数的高斯函数近似和平方近似,从理论上分析了大气成像系统的光学传递函数,研究了有限湍流尺度(湍流内、外尺度)对湍流大气中成像系统光学分辨率的影响。给出了成像系统长曝光光学传递函数和积分分辨率的近似解析关系。结果表明在采用大孔径成像系统成像时,应该考虑湍流尺度对大气系统成像的作用。     

基于FPGA的红外焦平面信息获取系统设计

基于红外焦平面探测器的红外遥感技术是实现多通道和高空间分辨率的重要手段,而随着焦平面探测器中探测单元的增加探测数据也急剧增加,研究基于FPGA的高速并行处理技术对解决红外探测领域多通道高速信息获取有重要意义。以FPGA作为控制器件,设计了16通道,数字分辨率为16bit的ADC采集方案,实现对32×32元的红外焦平面探测器数据并行获取,并设计了数据宽度为16bit的数据输出接口,用来完成采样数据的上传功能。实验结果表明该方案设计简洁,数据上传速度控制灵活,可以满足焦平面探测器的信号获取与传输。     

微型差动式共焦自聚焦光聚焦探测系统

为解决微小内轮廓尺寸为代表的微小尺寸的非接触式超精密测量问题，提出了将自聚焦透镜体积小的特点与共焦显微技术的高分辨率和绝对位置跟踪特性相结合的差动式自聚焦共焦微型显微技术的光探测技术，建立了相应的传感系统，介绍了系统的工作原理和构成，自聚焦透镜测头直径为1mm，两个探测器差动设置，不但消除了光源的光强漂移和探测器的电子漂移产生的共模噪声，提高了测量信噪比，而且有效地提高了系统的轴向分辨率，初步实验表明，系统轴向分辨率在倾斜率小于20度的范围内可达5nm。     

显微热成像系统自适应位置标定方法

利用光学微扫描技术,可在不改变探测器结构的情况下,提高显微热成像系统空间分辨率。但为了获得高质量过采样重构图像,微扫描位置需要标定。基于零点定标,提出一种各点自适应定标的微扫描位置标定方法。模拟实际系统在定标前后的欠采样图像,采用不同重构方法进行仿真对比验证;完成了实际采集的欠采样显微热图像序列的重构对比实验。实验结果表明该方法明显改善了显微热成像系统的过采样重构图像质量,提高了系统空间分辨率。此方法还可以应用在其他光电成像系统中。     

应用电光调制干涉系统对甲烷气体浓度监测的研究

对甲烷气体浓度的监测应用领域很多,而目前绝大多数采用的是化学反应方法,存在安全性低、稳定性差等缺点,而采用光学干涉法定性定量分析稳定性高、抗干扰能力强。设计了电光调制的干涉系统进一步提高其探测精度。在干涉系统中,利用可变折射率晶体LiNbO₃的电光调制特性,对晶体折射率进行调制,增大静态光程扫描范围,提高光谱分辨率。系统对晶体两侧分别加载相位相反的调制信号,使其在不改变干涉具尺寸的条件下提高光谱分辨率。通过推导折射率调制度与光程差的函数关系,仿真计算可知比同尺寸干涉系统光谱分辨率提高了近一个数量级。实验采用SGT-3型声光调制器,1 650 nm红外激光器对不同浓度的甲烷气体进行检测,实验结果显示,此方法比传统的热释电法精度好、稳定性高,更适合在矿井等复杂环境下应用。     

The Limitations of Nonlinear Fluorescence Effect in Super Resolution Saturated Structured Illumination Microscopy System

Classically, optical systems are considered to have a fundamental resolution limit due to diffraction. Many strategies for improving both axial and lateral resolutions are based on a priori information about the input signal. These strategies lead to a numerical aperture improvement. However these are still limited by the wave nature of light. By using fluorescence technique one theoretically can reach unlimited resolution. The key point is to use the nonlinear dependence of the fluorescence emission rate on the intensity of the applied illumination. In this paper we present simulation as well as experimental results which show the advantage and the problems of using the nonlinear fluorescence effect in super resolution systems as well as discussing the nonlinear phenomena concerning the fluorescence process. The results show that the nonlinear fluorescence effect is accompanied by severe quenching, bleaching and saturation phenomena. As consequence, super resolution using saturated structured illumination method in living biological samples becomes severely restricted.     

折/反混合式长波红外成像光谱仪光学系统设计

为了实现遥感目标的长波红外高光谱成像,满足目标探测对多信息量的需求,设计了高光谱分辨率长波红外(8~12 μm)成像光谱仪。前置望远系统采用离轴三反系统,以实现无遮拦、大口径及宽视场成像设计;光谱分光系统分别采用折射式和反射式结构进行优化设计。设计结果显示,采用折射式结构,可得到通光孔径为100 mm,F数为2,光谱分辨率16 nm,空间分辨率150 μrad,冷光阑效率100%,成像质量接近衍射极限的光学系统;采用反射式结构,为了保证光学系统无挡光,需采用多片离轴反射镜,增加了系统的非对称性,使得系统的像散、彗差和场曲难以校正到最佳状态。设计结果表明：折/反混合式成像光谱系统具有光谱分辨率高、成像质量好和结构合理等优点,点斑均方根直径与国内现有探测器像素尺寸匹配。     

大气水汽探测地基差分吸收激光雷达系统设计与性能仿真

为持续获得对流层低层高精度、高时空分辨率的水汽浓度分布数据,提出了一套改进的大气水汽探测地基差分吸收激光雷达系统方案.详细描述了系统主要组成部分,对主要误差进行了分析与估计,并提出了一种差分吸收截面实时测量装置用于补偿发射激光器带来的测量误差.针对该系统,并结合上海地区不同季节的水汽浓度状况,对935 nm水汽吸收带中四个水汽吸收峰的差分光学厚度、雪崩二极管的倍增系数M与回波信噪比的关系、水汽浓度随机测量误差等进行了详细的仿真与分析.仿真结果表明,根据不同的季节和天气状况,可以选择不同的吸收峰以达到最佳探测效果;在300—5000 m高度范围内,最大可以达到300 m的垂直分辨率与5 min的时间分辨率,水汽浓度随机测量误差不超过18%.     

Transillumination Laser Computed Tomography System with Fiber-Optic-Based Coherent Detection Imaging Method - High Spatial-Resolution and Quantitative Tomographic Imaging of Highly Scattering Objects -

We recently proposed and developed a novel transillumination laser computed tomography (CT) imaging system using a fiber-optic method based on coherent detection imaging (CDI) for biomedical use. Use of optical fibers enables portability and robustness against environmental changes in a room, such as variable temperature, air-flow shifts, and unexpected vibrations. In addition, motion-artifact-free images can be obtained because measurements can be performed with the object fixed. In the present paper, we experimentally investigate in detail the fundamental imaging properties of the system, which has a spatial resolution of 500 μm, a dynamic range of approximately 120 dB, and a minimum-detectable-optical power of 10⁻¹⁴W as a result of the excellent properties of the heterodyne detection. Based on experimental observations, the proposed system can reconstruct tomographic images of highly scattering objects in the transillumination mode, similar to X-ray CT, at sub-millimeter spatial resolution and with quantitativeness. Finally, we demonstrate with experiments using a physical phantom that the imaging system possesses high resolution and quantitative imaging abilities for highly scattering objects.