一种液晶透镜盒间隙的测试方法

针对当前液晶透镜盒间隙测试存在的难题, 文中提出采用线偏振干涉法测试方法, 采用光强均匀分布的单色光入射, 检偏器的偏光轴方向与起偏器的偏光轴垂直或者平行, 液晶透镜的液晶取向层的摩擦方向与起偏器偏振轴夹角为45°, 此时干涉条纹亮暗差别最明显. 利用液晶透镜中心保持预倾角不变的透过率以及其他位置透过率最大值来计算液晶透镜的盒间隙, 该方法简单、可靠, 因采用光学手段测试, 其精确度相对较高. 关键词： 液晶透镜 盒间隙 线偏振光干涉 透过率     

一种确定偏振元件透光方向的简单方法

<正> 两块偏振片,很容易使它们的透光方向正交(消光)。但如果没有其他透光方向已知的偏振元件,如何确定它们的透光方向?下面提供一种简易方法。若如图1所示,起偏器透光方向P_1位于竖直方向上,检偏器透光方向P_2位于水平方向上(起偏器、检偏器都平行于纸面放置,光线由纸面向着观察者),则看到消光;若这时把起偏器或检偏器绕竖直轴翻转180°,则视场仍将保持消光。这一现象提供了起偏器和检偏器的     

四区域法消除偏振棱镜缺陷对波片相位延迟测量的影响

在起偏器-待测波片-检偏器系统基础卜提出一种四区域测量波片相位延迟量的方法.调整待测波片和检偏器的方位角,获得相应的四组光强值,通过线性运算得到待测波片的相位延迟量,完全消除了起偏器和检偏器不完全消光带来的误差.由于测量系统中不存在标准波片或其他相位调制元件,允许测量波长仅受偏振棱镜和探测器的限制,因此四区域法可适用于很大波长范围内的波片测量.以λ/4波片为例,理论分析了测量系统利用四区域测量法后的仪器误差为σφ≤士3.49065×10-3rad(约0.2°),精度比原算法提高约1个数量级.实验验证了四区域法能有效提高系统精度.     

基于最小二乘拟合的波片相位延迟测量

提出一种精密测量波片相位延迟的新方法.将待测波片置于起偏器和检偏器之间,通过步进电机控制波片匀速旋转,基于最小二乘法拟合出射光强随波片方位角变化的曲线,进而得到波片延迟.根据上述原理,建立了一套波片延迟测量系统,并分析了系统的稳定性、可测量的延迟范围、接收器件的非线性效应、系统误差源这4个影响测量精度的主要方面.结果表...     

样品校准法在单波长椭偏仪中的应用

椭偏仪是薄膜测量的重要工具。从模拟和实验两方面,描述一种新颖的单波长椭偏仪的校准方法。该方法的基本思路是:如果被测样品的相关信息(折射率n,吸收系数k,厚度d)已知,则可以通过测量光强变化的傅里叶系数,采用最小二乘法原理反演出此时椭偏系统的信息(即校准参数,包括起偏器方位角P,检偏器方位角A,波片起始旋转角Cs,波片位相延迟δ,系统入射角θ0)。利用校准得到的系统参数和测量未知样品得到的光强傅里叶系数,求得未知样品的厚度。该方法具有操作简单、节约成本等优点。分别针对2～6个样品尝试了校准,对该校准方法做了模拟分析。将该方法用于实际测量,考证校准后的测量效果,并做了误差分析,最大误差为0.26nm。     

液晶磁控偏光特性的研究

利用偏光干涉理论,通过对BL-009型向列相液晶透射比的测试,分析了液晶透射比随磁场的变化情况,并对液晶的磁控双折射效应进行了研究.实验在室温20℃下用JG-3型连续可调磁场仪对液晶盒施加垂直于其表面的磁场,用CT5A型特斯拉计准确读出磁场强度数值,使液晶盒光轴方向与起偏镜和检偏镜偏振方向成45°,分别测出了起偏镜和检偏镜偏振方向平行和垂直时的透射光强度.通过数学函数拟合,得出了液晶的双折射率随磁场的变化规律,即：当磁场强度大于液晶的阈值磁场时,拟合函数能很好地描述液晶磁控双折射率的变化规律.     

旋转波片偏振仪波片方位误差研究

旋转波片Stokes偏振仪是最常用的测量光束偏振态的仪器。波片快轴方位误差是影响旋转波片Stokes偏振仪的主要误差源之一。为了研究波片方位偏差对测量精度的影响,提出了一种描述波片快轴方位误差向最终的偏振测量误差传递的数学模型,并引入协方差矩阵法表征偏振测量误差。根据这一模型,获得最优的偏振仪配置参数。在推导过程中,假设波片方位误差服从同一高斯分布。基于此误差模型,得到如下结论：(1)由波片方位误差引入的测量误差与光强测量次数N成反比;(2)测量误差独立于入射光强度,但是依赖于入射光偏振态(s₁, s₂, s₃)和波片的位相延迟量δ;(3)波片位相延迟量在(103.22°, 116.13°)范围内时波片方位误差引入的测量误差最小。最后,经过仿真实验证明,所得解析结果与仿真模拟结果相一致。     

光谱型椭偏仪对各向异性液晶层的测量

探讨了利用普通光谱型椭偏仪对各向异性液晶层进行综合性测量的可行性. 并利用法国Jobin Yvon公司的UVISEL SPME(Spectroscopic Phase Modulated Ellipsometer)光谱型椭偏仪测量了光学各向异性液晶层的折射率n_o和n_e及液晶层厚d，进一步利用椭偏仪在透射方式下测量了平行排列液晶层的光延迟特性Δnd，二者取得了很好的一致性，说明利用光谱型椭偏仪可以实现对光学单轴性液晶层及其他材料的测量，测厚精度为纳米量级. 关键词： 光谱型椭偏仪 各向异性 折射率 相位延迟     

基于旋转波片的斯托克斯参量检测与精度分析

用于偏振光学遥感器定标的参考光源,其偏振态的检测精度会直接影响偏振光学遥感器的定标精度,进而影响目标特性的反演水平。选用870 nm波段的水平线偏振光作为被测试的定标参考光源,通过旋转1/4波片(quarter-wave plate, QWP)对其光强进行调制。调制光强可表达为波片快轴旋转角度的傅里叶级数,采用傅里叶变换法反演出级数的系数,根据该系数即可计算出被测试光源的Stokes参量。给出10次测量各参量及偏振度的平均值、标准偏差、合成不确定度以及测量平均值与理论值的相对偏差。为提高测试精度,通过对波片快轴初始定位角度偏差Δα、延迟量偏差Δδ与检偏器透光轴角度偏差Δβ进行分析,提出了偏差修正模型。该模型通过Stokes参量检测偏差随Δδ和Δβ的变化趋势及实际偏差值,确定Δδ和Δβ的大小。结合模拟出的波片快轴初始定位角度偏差Δα,对实验装置加以调整,再次对光源的偏振态进行检测。结果表明,基于该修正模型测得光源的各Stokes参量与理论值最大偏差从未经修正的3.77%降低至1.41%。证实了基于本实验的原理、装置、测量方法及所提出的偏差修正模型可有效提高定标参考光源偏振态检测的精度。     

共孔径偏振耦合分光的旋转四分之一波片相位补偿技术

 在地平式折轴望远镜中开展自适应光学激光导星实验，研究了共孔径发射接收信标激光束偏振耦合分光效率随望远镜方位角和天顶角变化的补偿技术。提出了一种由四分之一波片和法拉第旋光器构成的相位补偿器，通过旋转四分之一波片以实时补偿由于望远镜旋转导致的光路相位延迟量的变化。数值计算表明，望远镜处于任意方位角和天顶角位置时，通过1°步长旋转四分之一波片，可使补偿后的偏振分光效率理论上达到99.90％以上。实验从原理上定性地验证了该方法的有效性。只要测量出镜面的相位延迟，便可计算得到望远镜处于不同方位角和天顶角情况下有效补偿所需的四分之一波片旋转角度，据此可建立实用的旋转波片偏振补偿装置。     

Modified total intensity ratio methods for measuring cell gap of twisted nematic liquid crystal cells

This paper modifies the total intensity ratio method (TIRM) used to measure the cell gap of twisted nematic liquid crystal (TNLC) cells. Compared to the conventional TIRM in which a mechanical mechanism is used to physically rotate the polarizer, the modified TIRM methods presented in this study measure the total intensity ratio using a polarization rotation modulator. Two modified measurement methods are introduced. In the first, the saw-tooth signal applied to the electro-optic (EO) modulator is used as a reference signal in order to determine the polarization state of the measured signal. In the second method, a beam splitter and an additional quarter wave plate are added to the optical configuration. The quarter wave plate is adjusted such that a phase-matching condition is obtained between the reference and measured signals. The experimental results confirm that the modified TIRM approaches yield comparable accuracy to the conventional TIRM. Furthermore, in the proposed approaches, sufficient intensity signals to determine the cell gap can be obtained in just 2 s.     

Two-dimensional birefringence measurement system with a polarization modulator and a rotating analyzer

The measuring system of two-dimensional birefringence distribution with a polarization modulator and a rotating analyzer using a rotating analyzer method is presented. The system simply consists of a laser diode, two polarizers, two quarter wave plates and a CCD camera. Thanks to an imaging system, the mechanism to scan a sample is unnecessary and two-dimensional measurement is possible and easy. The birefringence of retardation and orientation of the optic axis can be determined by the azimuth angle of an elliptically polarized light passing through a sample. The azimuth angle is obtained by applying the phase shifting algorithm to measure the polarization properties; by improving the calculation algorithm, wide range measurement is accomplished. The measurement procedure and a number of results are described.     

Jones矩阵在偏振光实验中的应用

将Jones矩阵应用于偏振光实验研究,通过偏振光的Jones矢量表示和偏振器件的Jones矩阵,分析了偏振光通过偏振器件后偏振态的变化,准确方便地解释了偏振光实验中的实验现象。     

应变液晶散射偏光片的试制

介绍了聚合物分散液晶(PDLC)和应变液晶(SLC)以及散射偏光片的概念,实验制备了应变液晶散射偏光片样品,样品由两张胶片夹层聚合物分散液晶膜在紫外光固化过程中施加剪切应力所形成。给出了样品偏光显微镜照片和可见光分光光度计偏光特性光谱分析。实验结果表明,应变液晶散射偏光片样品外观半透明,在正交偏光场中转动样品有颜色变化,通过样品观察液晶显示器屏幕,在不同角度下有透射和散射作用,在偏光显微镜中观察样品有衬垫料被拉动的痕迹,光谱分析显示样品在绿光550nm波长处最大透光率T∥≈50%,最小透光率T⊥≈5%,偏振度P≈82%。实验结果对于研制实用的拉伸液晶散射偏光片具有参考意义。     

Leakage of light in liquid crystal displays and birefringent thin film compensators

This paper elucidates the physical origin of leakage of light in the dark state of liquid crystal displays (LCDs) and describes birefringent thin film compensators to mitigate the problems. There are two fundamental sources of leakage of light in LCDs. They are the leakage of light through a pair of ideal crossed polarizers, and the leakage of light due to elliptical state of polarization after transmitting through the liquid crystal (LC) cell. The leakage of light in the dark state leads to poor contrast ratios and color instability, particularly at large viewing angles. The paper then describes the employment of sixth-wave (λ/6) plates as well as various wave plates that function as birefringent compensators for eliminating the leakage of light in LCDs.     

聚合物网络稳定液晶的电光偏振片

制备了一种散射偏振片,它是由非晶态单体形成的聚合物网络、向列液晶和涂有聚酰亚胺的ＩＴＯ玻璃基板组成。聚酰亚胺被反向平行摩擦,液晶分子则沿摩擦方向取向,并被单体形成的网络所稳定。根据聚合物网络液晶的电光特性可知。入射偏振光束被散射或透射相应地取决于其偏振方向平行还是生趣于基板的摩擦方向。平行时,光的散射强度通过电场可被强烈地调节;垂直时,光的透过率很高,几乎不依赖施加的电场。这种偏振器件具有低的驱动     

Full field automated evaluation of the quarter wave plate retardation by phase stepping technique

Quarter wave plates are optical elements commonly used in photoelasticity to obtain circularly polarized light. They divide the incident light field into two linearly polarized orthogonal components with a phase difference of a quarter of the light wavelength. Due to the tolerance in manufacturing, however, the actual phase shifting produced by the plates is affected by an error, which noticeably influences the photoelastic measurements performed by means of various automated methods. This paper presents a technique, based on the phase stepping method, for the full field automatic evaluation of the quarter wave plate error.     

A NEW METHOD TO ALIGN LIQUID CRYSTAL MOLECULES BY LINEAR PHOTO-POLYMERIZATION FOR LIQUID CRYSTAL DISPLAY

A new technique to uniformly align liquid crystal molecules is presented. The technique is based on producing an anisotropic surface on the glass substrate coated with photo-polymers by photo-polymerization of linear polarized UV-light. The orientation of liquid crystal molecules is governed by the direction of the polarized vector of UV-light. Using this method, we have studied the photo-polymer PSi-CM aligning LC 6710A molecules. The liquid crystal microscopic texture between crossed polarizers, optical retardation from liquid crystal layers and electro-optical properties of twisted nematic liquid crystal display cell are obtained, which was prepared with one side -photo-alignment and the other side-rebbed substrate.