单轴晶体的光程差和Lyot型滤光器的视场

 建立了以光线入射方向和晶体光轴方向为基准的入射坐标系，利用波法线反曲面方程和电磁场在晶体折射界面处切向分量连续性的边界条件，得到了晶体中波法线方向、射线方向、波法线折射率和射线折射率的表达式。从非常光的射线方向和射线折射率出发，得到了在任意的晶体光轴方向和入射角条件下，光通过单轴晶体后寻常光、非常光的光程差表达式。对Lyot型滤光单元的透射率和视场进行了计算分析后发现，滤光单元的透射率随光线入射角的变化呈现一定的周期性，视场随光轴倾角的增大而减小。得出了透射率和视场随光轴倾角(光轴与晶体表面的夹角)和光线入射角(光线在晶体表面的入射角)的变化规律。讨论了通过改变晶体倾角实现滤光器调谐和补偿晶体厚度加工误差等技术问题。     

天基激光告警系统成像特征及信噪比研究

目标成像特征和信噪比是天基激光告警系统优化设计、目标检测及攻击事件判定的重要依据.在介绍告警系统结构的基础上,分析计算了攻击激光成像光斑的情况,并进行了实验验证,讨论了系统的背景光噪声环境,计算了入瞳处的背景光辐照度,推导了系统成像信噪比公式,并得到了攻击激光成像信噪比.结果表明:攻击激光在正入射情况下的理论光斑直径约...     

谐振式集成光学陀螺噪声分析与实验研究

针对目前谐振式集成光学陀螺(IORG)输出检测精度与其理论极限灵敏度存在两个数量级差别的情况,分析了IORG系统中存在的主要噪声源;搭建了基于单光路锁频和单光路输出的IORG噪声分离系统;分别对无光情况下信号检测系统中各部分的噪声以及陀螺静态频率锁定情况下各部分的噪声影响进行了测试与分析;得到了系统的噪声分布情况。实验结果表明:光路噪声以及包括探测器热噪声和散粒噪声的电路固有噪声为系统的主要噪声源。     

Optical filter with tunable wavelength and bandwidth based on cholesteric liquid crystals

An optical filter with tunable wavelength and bandwidth has been demonstrated using two cholesteric liquid crystals configured in a reflection mode, in which the incident light is first reflected by one cholesteric liquid crystal and then by the other one. The central wavelength can be tuned from 527 nm to 574 nm and the bandwidth can be changed from 10 nm to 80 nm. It has potential applications in many fields, especially in optical communications and multispectral and hyperspectral imaging systems.     

A volume holographic optical element for optical coupling to single-mode fibers

We propose and demonstrate a volume holographic optical element (VHOE) for signal-mode fiber coupling and the sending of conjugate waves of reference light for the construction of holographic elements. Given the inherent Bragg conditions of the VHOE, the angular tolerances of the conjugate reading light in both the horizontal and vertical directions are studied under different conditions.     

X射线光场成像技术研究

X射线三维成像技术是目前国内外X射线成像研究领域的一个研究热点.但针对一些特殊成像目标,传统X射线计算层析(CT)成像模式易出现投影信息缺失等问题,影响CT重建的图像质量,使得CT成像的应用受到一定的限制.本文主要研究了基于光场成像理论的X射线三维立体成像技术.首先从同步辐射光源模型出发,对X射线光场成像进行建模;然后,基于光场成像数字重聚焦理论,对成像目标场在深度方向上进行切片重建.结果表明:该方法可以实现对成像目标任一视角下任一深度的内部切片重建,但是由于光学聚焦过程中的离焦现象,会引入较为严重的背景噪声.当对其原始数据进行滤波后,再进行X射线光场重聚焦,可以有效消除重建伪影,提高图像的重建质量.本研究既有算法理论意义,又可应用于工业、医疗等较复杂目标的快速检测,具有较大的应用价值.     

Compact optical correlator based on one phase-only spatial light modulator

An optical correlator that utilizes one phase-only spatial light modulator (SLM) combined with a mirror is proposed and demonstrated. This system is compressed by displaying the input and filter pattern on different parts of the same SLM. The background noise is separated from the correlation signal by superimposing a high-frequency carrier with the filter pattern except in the zero-frequency regions, which will improve the signal-to-noise ratio in pattern recognition. Our architecture is compact and the cost is relatively low by utilizing only one SLM.     

用于探测生物芯片的制冷型ICCD系统

利用光锥耦合的ICCD系统探测荧光染料标记的生物芯片,并对CCD芯片和像增强器制冷,以提高探测灵敏度。基于实验分析结果,指出背景噪声的主要来源为杂散光和生物芯片基底所发的荧光,指出用镜头成像限制了系统探测灵敏度的提高,可采用低荧光物质作为生物芯片的基底对系统加以改进。     

Collinear diffraction of divergent optical beams

Two variants of anisotropic collinear diffraction of light on a sinusoidal diffraction grating are studied theoretically with forth and back light scattering relative to the direction of the incident beam. For both variants, two-dimensional transfer functions are calculated and their modification with optical wavelength and diffraction grating period is analyzed. The dependence of integral diffraction efficiency and filter passband on optical beam divergence is examined.     

与人射线偏振光振动方向无关的低偏振度消偏器

消偏器是光纤传感器、光放大器等偏振敏感性光学系统中的关键器件,用于减小输入光的偏振度(DOP)。设计了一种与入射线偏振光振动方向无关的低偏振度消偏器,该器件中利用人为的偏振相关延迟代替了保偏光纤的双折射,并在偏振相关型消偏器前增加了一个1/4波片,从而对任意方向振动的线偏振光具有相同的消偏能力,结构紧凑。对消偏性能随波片阶数、入射光中心波长和振动方向的变化作了数值计算。实验中采用半峰全宽为0．13 nm的光源,入射线偏振光在任意方向振动时,输出光偏振度小于2．6%,消偏器的插入损耗为0．6 dB,损耗起伏小于0．11 dB。实验和数值计算结果表明,该消偏器具有低偏振度、低插入损耗和适合于宽光谱应用的优点。     

与入射线偏振光振动方向无关的低偏振度消偏器

消偏器是光纤传感器、光放大器等偏振敏感性光学系统中的关键器件,用于减小输入光的偏振度(DOP).设计了一种与入射线偏振光振动方向无关的低偏振度消偏器,该器件中利用人为的偏振相关延迟代替了保偏光纤的双折射,并在偏振相关型消偏器前增加了一个1/4波片,从而对任意方向振动的线偏振光具有相同的消偏能力,结构紧凑.对消偏性能随波片阶数、入射光中心波长和振动方向的变化作了数值计算.实验中采用半峰全宽为0.13 nm的光源,入射线偏振光在任意方向振动时,输出光偏振度小于2.6%,消偏器的插入损耗为0.6 dB,损耗起伏小于0.11 dB.实验和数值计算结果表明,该消偏器具有低偏振度、低插入损耗和适合于宽光谱应用的优点.     

Effect of binary phase plate on incident radially polarized hollow Gaussian beam

Effect of a pure binary phase filter on the three-dimensional light intensity distributions in focal region is theoretically investigated in this paper. The results show that the proposed binary phase filter may induce flat top profile with large depth of focus and reduced focal spot by properly adjusting the geometrical parameters of the binary phase filter of incident radially polarized hollow Gaussian beam (HGB) beam. On the other hand, the HGB beam benefits the most from the use of an annulus. Such kind of system is potentially useful for lithography, imaging, optical data storage, optical trapping, optical excitation of molecules, or coupling to optical fibers.     

Detection of infrared small target based on fusion of multi-filters北大核心CSCD

Aiming at solving accuracy problem of infrared small target detection in sky and ocean background scenarios of infrared image sequences, a novel infrared small target detection based on multi-filters algorithm fusion method is presented in this paper. Firstly infrared small target and imaging, time and space characteristics of the corresponding background noise are analyzed. Tophat algorithm with improved Robinson guard filter are then integrated to highlight target and suppress clutter background by using infrared small target imaging features. Adaptive threshold segmentation is used to extract candidate targets, while Unger smoothing filter and multi-objects association filter are used to eliminate random noise and false targets in the candidate targets. Multiple experiments of infrared small target image sequences are implemented, and experimental results show that proposed method can detect infrared small targets at 99% detection rate with high reliability and good real-time performance. © 2017, Editorial Board, Journal of Applied Optics. All right reserved.     

高斯型弱散射屏产生的像面散斑场的分布特性研究

弱散射屏产生的远场散斑由一个中央亮斑和一个分布于亮斑周围而与正态散斑类似的散斑结构, 根据弱散射屏远场的散斑图样, 人们假设弱散射屏产生的像面散斑为均匀背景与正态散斑两者相干叠加的结果, 但这种假设与实际像面散斑存在歧异, 基于上述情况, 本文利用4f高通滤波光学成像系统, 研究了高斯型弱散射屏产生的像面散斑场的统计特性, 得出只有表面均方根粗糙度与入射光波的波长相差不多时上述假设才是可行的结论. 关键词： 弱散射屏 f光学成像系统')" href="#">4f光学成像系统 像面散斑     

Acousto-optic filter of nonpolarized electromagnetic radiation

An acousto-optic tunable filter that is insensitive to the polarization of incident light is studied both theoretically and experimentally. The fundamental possibility of designing an acousto-optic filter of nonpolarized light is demonstrated. The filter operates in the visible range of electromagnetic waves with λ=480–750 nm and provides a high spatial and temporal resolution. The number of resolvable spots of the filtered image reaches a value of 400×400 with the spectral bandwidth of the device being Δλ=1.7 nm. The results of the processing of optical images formed by arbitrarily polarized light beams are discussed. An acousto-optic filter based on a TeO₂ crystal can be used in optics and spectroscopy in the processing of light beams with an arbitrary polarization, as well as in analyzing optical images formed by light beams whose polarization varies with time.     

Design and performance evaluation of the imaging payload for a remote sensing satellite

In this paper an analysis method and corresponding analytical tools for design of the experimental imaging payload (IMPL) of a remote sensing satellite (SINA-1) are presented. We begin with top-level customer system performance requirements and constraints and derive the critical system and component parameters, then analyze imaging payload performance until a preliminary design that meets customer requirements. We consider system parameters and components composing the image chain for imaging payload system which includes aperture, focal length, field of view, image plane dimensions, pixel dimensions, detection quantum efficiency, and optical filter requirements. The performance analysis is accomplished by calculating the imaging payload's SNR (signal-to-noise ratio), and imaging resolution. The noise components include photon noise due to signal scene and atmospheric background, cold shield, out-of-band optical filter leakage and electronic noise. System resolution is simulated through cascaded modulation transfer functions (MTFs) and includes effects due to optics, image sampling, and system motion. Calculations results for the SINA-1 satellite are also presented.     

激光相干场成像散斑噪声复合去噪方法

噪声是影响激光相干场高分辨成像系统像质的重要因素,激光相干场成像系统既受背景光加性噪声影响,又受激光乘性散斑噪声影响.为解决激光相干场成像系统受激光乘性散斑噪声和背景光加性噪声叠加引起的成像像质退化效应问题,从噪声抑制角度提高激光相干场系统高分辨成像像质,研究建立了激光散斑乘性噪声和背景光加性噪声对大气下行链路激光回波场信号影响干扰模型,并基于该模型提出了一种基于同态滤波和稀疏基追踪级联复合去噪算法.首先基于同态滤波理论将激光乘性散斑噪声转化为加性噪声,再由高通滤波器滤除散斑噪声,最后采用基追踪稀疏理论方法抑制背景光等加性噪声对像质的影响.研究表明,较现有单一去噪方法,该级联复合去噪方法可一次性消除激光乘性散斑噪声和背景加性噪声两种不同性质的噪声,有效改善了激光相干场成像质量.     

Strain- and twist-engineered optical absorption of few-layer black phosphorus

Density functional and many-body perturbation theories calculations were carried out to investigate fundamental and optical bandgap, exciton binding energy and optical absorption property of normal and strain- and twist-engineered few-layer black phosphorus (BP). We found that the fundamental bandgaps of few layer BP can be engineered by layer stacking and in-plane strain, with linear relationships to their associated exciton binding energies. The strain-dependent optical absorption behaviors are also anisotropic that the position of the first absorption peak monotonically blue-shifts as the strain applies to either direction for incident light polarized along the armchair direction, but this is not the case for that along the zigzag direction. Given those striking properties, we proposed two prototype devices for building potentially more balanced light absorbers and light filter passes, which promotes further applications and investigations of BP in nanoelectronics and optoelectronics.     

基于数字滤波的主动式高光谱成像系统及其波长标定

基于数字滤波技术,提出了获取物体反射光谱数据立方体和光谱响应曲线的主动式新型高光谱成像系统。对传统WDF型瓦兹渥斯反射式单色仪进行了改装,在入射光一定的情况下,增大出射光通量,提高了照射在物体表面的光强。利用数字滤波方式代替光学窄带滤波器,解决了多个光学滤光片不能连续可调和其他滤波器成本高的问题,建立了波长连续可调,带宽可调的高光谱成像系统。针对系统的特点和采集方式,提出了适当的定标方式,其波长误差2nm。得到了绿色树叶效果良好的光谱数据立方体和响应曲线,表明提出的系统适用于实验室中小视场内的光谱成像测量研究。     

光波p分量在单轴晶体表面反射和折射的相位特性

根据单轴晶体的双折射和双反射性质,通过数值计算研究了光轴在入射面内并与晶体界面成任意角时光波p分量在单轴晶体表面反射和折射的相位特性.结果表明,光轴取向对相位变化有较大影响,光从光疏各向同性介质射入单轴晶体时,光轴方向改变反射光p分量的相位突变点,但对折射光p分量相位无影响.光从光密各向同性介质射入单轴晶体未发生全反射时,光轴方向同时影响p分量反射光和折射光的相位突变|发生全反射后,光轴方向影响反射光p分量的相位变化曲线.从单轴晶体出射到光疏各向同性介质未发生全反射时,光轴方向改变反射光p分量的相位跃变规律,折射光p分量在光轴方向和晶面成小角度时在布儒斯特角附近发生相位突变|发生全反射后,反射光p分量的相位变化曲线随光轴方向的改变发生较大变化.