偏振控制器的完全扰偏算法研究

从一种偏振度测试系统的系统结构出发建立光路传输模型,在分析光纤挤压型偏振控制器的工作原理后,给出整个光路传输模型的穆勒矩阵。在此基础上,文中重点研究了偏振控制器的完全扰偏算法,并用MatLab对算法进行了仿真。仿真结果表明该算法能够实现完全扰偏并有效提高偏振度测试精度。     

大尺寸旋光晶体内反射偏振特性的研究

用标准水溶液法生长出的长30.62mm、宽29.20mm、高28.34mm的透明的大尺寸立方体氯酸钠晶体。以一束线偏振的He-Ne激光入射到氯酸钠晶体,使在其内部以布儒斯特角33.42°内反射并再经过全反射出射。首次从理论和实验的两方面对该大尺寸氯酸钠晶体内反射时的偏振特性做了研究,发现在消光位置,氯酸钠晶体入射光的偏振取向较之普通玻璃的入射光偏振取向旋过了87.43°。     

施密特棱镜偏振特性的研究

为了分析施密特棱镜对自然光和部分偏振光的传输特性,使用Pauli旋转矩阵把施密特棱镜的Jones矩阵转换成Mueller矩阵。将一束部分偏振光经过施密特棱镜后分成两路偏振度相同的部分偏振光,再把两路部分偏振光各自分解为自然光与椭圆偏振光,发现两路椭圆偏振光的椭率角相同,方位角不同,由此可知两路部分偏振光是不相同的。理论和实验分析均表明,在部分偏振光入射时的偏振度和方位角的关系一定时,出射后两路部分偏振光中的椭圆偏振光的椭率角相等,方位角不等。     

基于偏振干涉滤光片的宽波带偏振方向旋转器的设计

首次提出了基于偏振干涉滤光片设计方法的宽波带偏振方向旋转器。该旋转器实现了 380 nm～ 780 nm全波长范围内的偏振方向旋转。与普通的只针对某一特定波长的半波片相比 ,该偏振旋转器特性大大超越了普通 1 /2波片 ,并且入射角在± 2 0°范围仍实现偏振方向旋转 90°的要求。将该偏振方向旋转器用作 LCD或 LCOS投影仪中的偏振转换器 ,将大大提高系统的光能利用率以及投影系统的对比度。     

Nanographite analyzer of laser polarization

An optical analyzer of laser polarization has been designed and manufactured. The principle of operation of this analyzer is based on the recording of the polarization-dependent surface photocurrents in nanographite films. The analyzer does not contain additional optical elements and consists of a cylindrical bushing with a gauge of its angular position, a nanographite film grown on a silicon substrate, two parallel measurement electrodes placed on the film surface, and an electrical measuring instrument. The nanographite film is placed on the bushing obliquely so that the measuring electrodes are parallel to the axial cross section of the bushing, which is oriented perpendicular to the film tilt plane. The analyzer can operate in the wavelength range from 266 to 4000 nm.     

分焦平面偏振图像传感器偏振主轴方向的标定

分焦平面偏振图像传感器的偏振主轴方向对后续使用斯托克斯矢量进行偏振参数解算的结果准确性有重要影响.为了标定该类型传感器,提出一种基于测量分焦平面偏振图像传感器中各偏振主轴方向像素输出平均值所拟合曲线相位差的方法,并对该方法进行了仿真与实际测试.控制照射到传感器表面的线偏振光,按照设定步长旋转若干周期,传感器同时拍摄图片...     

天空偏振光测量系统的设计

根据一束光的偏振特性可以由斯托克斯矢量来表征的原理,设计搭建了一种天空偏振光测量系统。该系统由计算机、赤道仪、光纤光谱仪和配备了可旋转偏振片的改进式天文望远镜组成,在400~900 nm的光谱分辨率为1.4 nm。赤道仪经过标定后可以实现0~180°方位角以及0~90°高度角的调整,角度分辨率为2.5°。系统的光学全视场为4.5°,使用该系统可以测量全天空的光强辐射度、偏振度以及偏振方位角。由标定结果可知,系统光强测量的重复率在450~500 nm为99%,在500~900 nm为(95±3)%;在400~750 nm偏振度测量误差＜2%,在475 nm处达到1.2%。偏振方位角的测量误差＜2°。     

On the extinction coefficient in confocal polarization microscopy

The extinction coefficient in conventional polarized light microscopes is non-zero, even with perfect polars, solely because of the image formation process in these instruments. The imaging in confocal microscopes is different from conventional instruments and it is shown that in this case an infinite extinction coefficient results in the ideal case whereas a finite value is always to be expected with conventional instruments. Images of the same microelectronic specimen taken in both conventional and confocal polarized light microscopes are compared.     

消光比与探测器噪声对基于纳米线栅偏振成像系统偏振精度的影响

消光比和探测器噪声是决定纳米线栅偏振成像偏振精度的两个重要参数。为解决两参数在系统优化时的取值问题,本文建立了两参数与偏振噪声的数学模型,采用像元组接收光电子数作为衡量探测器噪声与系统偏振噪声的桥梁量化了两者关系。仿真分析比较了两参数在入射光偏振态变化时对偏振噪声的作用。然后搭建消光比和曝光时间可调的偏振成像系统精度实验平台,验证该数学模型和仿真结果。仿真与实验共同表明,系统消光比大于20后,通过提高像元组接收的光电子数以抑制探测器噪声要比继续提升消光比对提高系统偏振精度的贡献大。     

LED magneto-optical ellipsometer with the switching of orthogonal polarization states

A light-emitting diode (LED) magneto-optical ellipsometer with the switching of orthogonal polarization states is described. The distinctive features of the ellipsometer are the implementation of the maximally deep azimuthal modulation, application of two-channel detector, use of a set of LEDs ensuring a high signal-to-noise ratio, and the absence of moving polarization elements. These features have substantially increased the precision of measurements of ellipsometric parameters ψ and Δ for ferromagnetic materials and their changes (δψ and δΔ) in the magnetic field, which are connected for the transverse Kerr configuration by simple relations with magneto-optical parameters. At wavelengths of 365, 372, 390, 405, 420, and 465 nm, the precision of ψ-δψ and Δ-δΔ measurements of metal films is about 0.0003° and 0.001°, respectively. The spectral resolution is 4 nm; the minimal measurement time of ψ and Δ in the continuous spectral range of 270–1000 nm is 20 s; the magnetic field is varied from–2500 to +2500 Oe; and the step of the magnetic field setting is 0.5 Oe.     

牛顿环偏振效应的探讨

采用霍尔型牛顿环实验装置以及多角度入射的偏振光源,对牛顿环实验进行了研究,发现其有明显的偏振效应。在P光和S光入射时,牛顿环的可见度随入射角变化有很大不同。利用P光和S光在界面上反射时有不同的振幅反射率,来对P光和S光入射时的可见度进行了理论计算,较好的解释了该现象。于是将传统的牛顿环等厚干涉推广到可同时演示光的偏振,扩大了牛顿环的教学与技术应用范围。     

荧光偏振法测定生物膜的流动性

本文采用荧光偏振法 ,研究剧烈运动前后线粒体质膜的流动性与粘度的关系     

基于像素级偏振相机的超像素校正

针对像素级偏振相机中偏振片单元由于刻划精度和透过率的差异导致偏振片阵列的非均匀性,提出了一种带有角度约束的最小二乘超像素校正方法。建立了带有角度约束的校正优化算法的数学模型,加入了超像素的标量增益和暗补偿参数。最后,搭建了以微偏振片为核心的积分球标定系统,进行了仿真实验和成像实验。结果表明:与最小二乘法相比,本文算法在有效地校正偏振度和非均匀性的同时也校正了超像素内振幅的非均匀性,重建角度的准确度提高了10%。经过插值处理后,边缘表现更为明显,有效减少了插值过程中所产生的噪声,提升了成像质量。     

基于大气偏振模式的三维姿态信息获取

现有的偏振光导航方法提供的二维方向信息不能满足导航的实际需求,因此,本文提出了一种利用大气偏振模式获取三维姿态信息的方法,选取太阳作为空间显著特征点,利用大气偏振模式信息计算出载体在两次不同状态下的太阳空间位置信息,通过建立姿态变换矩阵获得了载体的三维姿态信息。最后,对不同天气条件、不同太阳空间位置、不同波段以及天空被部分遮挡情况下太阳空间位置计算的误差分布情况进行了仿真分析和实际测量。实验结果显示,当天空有气溶胶粒子分布时,蓝色波段下的计算误差最小,方位角和高度角的误差分别为1.50°和2.10°;当观测视场中有树木遮挡时,方位角和高度角的平均误差分别为0.91°和1.97°,由此表明本文方法能够有效提取太阳的空间位置,获得载体的三维姿态信息,并满足实际导航的需求。     

Improving DIC microscopy with polarization modulation

It is demonstrated experimentally, as well as analytically, that when the polarization of the light incident upon the first Nomarski–Wollaston prism in a differential interference contrast (DIC) light microscope is switched by 90°, image highlights are changed into shadows and vice versa. Using an inexpensive ferroelectric liquid-crystal modulator, which is easily installed in the microscope, this switching can be done at 30 frames s⁻¹, synchronized to the camera. Subtraction of alternate digitized frames generates a stream of images in which contrast is doubled, compared with conventional video-enhanced DIC, while image defects and noise tend to cancel. Subtraction of alternate images is carried out efficiently by frame buffer operations and amounts to massively parallel synchronous detection. The new method eliminates the problems inherent in obtaining a separate background image, as required by current video-enhanced DIC practice, without loss of resolution.     

Methods for the measurement of polarization optical properties: I. Birefringence

A simple birefringence detection system has been developed that can be used with any standard polarizing microscope. A Foster prism is utilized in separating the orthogonal components of the resultant linearly polarized light coming from a properly oriented λ/4 plate. The light intensities of the orthogonal components are measured simultaneously and a mathematical manipulation yields a direct read-out of phase retardation (nm). The theory and practical use of this technique is discussed, as well as the present and future applications.     

An LED multichannel spectral ellipsometer with binary modulation of the polarization state

The use of a set of eight light-emitting diodes (LEDs) in a multichannel spectral ellipsometer with binary modulation of the polarization state allowed the development of a simple ellipsometer with a fully spanned wavelength range of 350–810 nm and high performance characteristics. The obtained reproducibility and stability of measurements of the ellipsometric parameters Ψ and Δ are 0.01° and 0.03°, respectively. The minimum times of measuring Ψ and Δ in the wavelength range of 435–690 nm and in the total range of 350–810 nm are 0.5 and 5 s, respectively.     

基于支持向量机预测偏振模式

基于多光谱多角度偏振辐射探测研究了大气偏振模式预测方法。首先,介绍了航空多角度偏振辐射计的探测原理与支持向量机回归算法;然后,从矢量传输模型出发,说明大气状况不变时,偏振模式主要取决于地表特征与观测几何,并介绍了观测几何与姿态之间的关系以及地表特征的表达形式;最后,在考虑平台姿态与地表特征的情况下,利用支持向量机回归算法预测了航空多角度偏振辐射计的探测偏振度,并对预测与实际试验探测的偏振度进行了比较。结果显示:偏振度预测误差小于1%,影响模型精度的主要因素不是姿态变化本身,而是姿态改变造成的观测地表特性变化。     

Accurate hyper-Rayleigh scattering polarization measurements

Apparatus and methods are described for measurement of the polarization dependence of hyper-Rayleigh scattering near 90° scattering angle with 0.1% accuracy for all four configurations where the incident and scattered light is linear polarized either parallel or perpendicular to the scattering plane. Measurements are made with large collection aperture and extrapolated to zero collection numerical aperture (NA = 0). Fiber coupling allows the system to be easily reconfigured for either polarization or spectral measurements.