电控液晶光阀中的指向矢分布特性

液晶分子具有介电和光学各向异性,在外电场作用下,液晶指向矢将会重新分布,具有高效的光学相位调制能力.本文从实验和理论角度对电控液晶光阀的光学调制特性进行了研究,结果表明:光阀阈值电压约为4V,且当外加电压高于阈值电压时,液晶光阀的透射强度随外加电压表现出非周期性特性.根据液晶连续体弹性理论,对电场作用下液晶光阀的指向矢分布特性进行数值分析,分析结果表明液晶光阀对透射光强的非周期调制特性取决于液晶体系的偏转状态,为研究液晶的偏振光调制特性提供理论依据及实验基础.     

向列相液晶盒中的挠曲电体积效应

基于液晶弹性理论研究了电压作用下向列相液晶盒中的挠曲电体积效应.通过变分理论得到了液晶指向矢倾角θ满足的微分方程,利用差分迭代的方法计算了强锚定平行排列液晶盒和混合排列液晶盒中液晶指向矢的分布情况,利用琼斯矩阵的方法计算了两种液晶盒中电光特性曲线.结合计算结果分析了挠曲电体积效应对混合排列液晶盒中液晶指向矢分布及电光特性曲线的影响.     

液晶指向矢分布的模拟和比较研究

用差分迭代法计算了扭曲、超扭曲以及混合排列丝状液晶在电场中指向矢的空间分布,与牛顿法和张弛法的计算作了比较;并应用于液晶电光特性的模拟计算 关键词： 液晶 指向矢 差分迭代     

挠曲电效应对向列相液晶盒电光效应的影响

研究挠曲电效应对向列相液晶盒电光效应的影响.通过变分理论得到液晶指向矢满足的微分方程和边界条件,利用差分迭代的方法计算强锚定和弱锚定液晶盒中液晶指向矢的分布情况.借助琼斯矩阵的方法,计算两种液晶盒电光特性曲线.此外,在计算中同时考虑了挠曲电表面和体积效应.     

液晶光阀的电光色散特性研究

分析液晶光阀(LCLV)的电光色散特性,重点研究扭曲向列型液晶光阀TB3639的电光色散特性。在温度为27 ℃时, 将TB3639液晶光阀置于频率为1 000 Hz的交流电场中,测出电光特性T-λ曲线,同时得到不同波长的T-V电光特性曲线,确定对比度与光波波长的函数关系k(λ),并得出电光色散特性关系曲线k(λ)～λ。分析结果表明, TB3639液晶光阀在可见光区域,具有相对较高的对比度,其色散较小。波长在450～750 nm区域其对比度均大于0.8;其中波长在550～670 nm区域其对比度变化不大,均大于0.95,其色散最小。     

频率驱动液晶光阀的电光特性研究

讨论了液晶光阀频率驱动方式的原理, 并分析了液晶光阀在频率驱动方式下的电光特性。在特定的交流电压下改变外加电场频率, 测量了TB3639型液晶光阀在频率驱动方式下的电光特性关系曲线。测量结果表明,TB3639液晶光阀在可见光区域具有电光显示灰度变化特性,不仅能实现黑白显示,也能实现不同灰度级显示。频率驱动方式在可见光的范围内对不同波长的透射率变化趋势影响大致相同,在应用中可避免出现色差较大的现象。这种新型频率驱动方式对液晶器件的显示有改善作用,将开拓液晶显示器件的新应用, 具有实际应用价值。     

液晶光阀的偏光显示特性分析

讨论了液晶光阀的偏光扭曲向列性效应, 分析了液晶光阀中液晶分子在交流电场作用下重新取向后的扭曲, 测量了TB3639型液晶光阀在特定的频率连续改变外加交流电压条件下,液晶分子重新取向后的扭曲角度以及液晶光阀的电光特性。测量结果表明,在外加电压连续改变时,入射线偏振光的透射率呈现连续非线性变化,这种非线性变化可以由液晶分子的扭曲量来改变。同时液晶分子180°的扭曲使得液晶光阀具有较陡的电光特性曲线,这对于多通道矩阵寻址方式的液晶光阀而言在矩阵显示中可有更多的通道寻址线和更高的对比度。     

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     

外电场作用下液晶指向矢分布差分迭代求解及液晶盒视角电光特性研究

根据液晶连续体弹性形变理论,本文首次提出液晶指向矢在外电场作用下分布的差分迭带求解法,实践表明该方法具有稳定性好,速度快,结果准确等特点,并适用于各种模式的液晶盒.在运用该方法求得液晶指向矢分布的前提下,结合消法布里-珀罗干涉快速4×4矩阵法,对液晶显示器的视角光学特性作了研究.     

基于液晶光阀的防眩目眼镜

基于常开型液晶光阀的电光特性设计了一种司机夜间行车时佩戴的液晶眼镜．液晶眼镜能够主动根据外界光强变化改变自身的透射率,从而使透射光强趋于稳定值．实验结果表明液晶眼镜能有效防止对面车灯引起的眩目, 同时不影响司机对路面的观察．     

液晶光阀实时图像变换实验

利用“液晶光阀变换系统”,开发和设计了“液晶光阀实时图像变换实验”。该实验内容包括：测试液晶光阀的工作曲线,确定液晶光阀的对比度,测试液晶光阀的响应时间,观察单缝的频谱,图像实时反转和微分,图像实时相减。     

液晶光阀用于光学傅里叶变换

结合我校开设的液晶光阀实验，介绍了几个典型的静态傅里叶变换实验内容，以液晶光阀在计算全息扫描器中的应用为例，对其在动态傅里叶变换中的应用进行了讨论。     

Threshold and saturation properties of the field-induced twist cell with two parameters weak anchoring boundaries

On the basis of two-parameter formula of weak surface coupling anchoring energy of nematic liquid crystals proposed by Zhao et al recently, the general torque equilibrium equation and boundary conditions of the director have been obtained and the threshold field as well as the saturation field of the field-induced twist cell have been analysed for three kinds of configurations, i.e. homogeneous, splay and Pi cells formed by different rubbing conditions and pretilt angles. The results indicated that the polar anchoring has no effect on the threshold field. It is determined only by the twist anchoring and pretilt angle. But, the polar anchoring and twist anchoring are coupling with each other and have a great influence on the saturation field. The formulae for calculating the threshold field and saturation field are given. These results will be very useful in understanding surface physics and the design of liquid crystal cells.     

栅状表面液晶盒的光学属性

基于栅状表面等效锚定能公式和弹性理论,对Bryan-Brown等人提出的混和排列向列相液晶盒进行研究.通过变分理论得到指向矢倾角和扭曲角满足的方程和边界条件.根据这些方程和边界条件,利用差分迭代方法计算出指向矢倾角和扭曲角对应某一个δ/λ值在不同电压下的分布.应用琼斯矩阵方法,研究这种液晶盒的电光效应.这些结果都与栅状表面的几何参数有关,即与周期λ和振幅δ有关.     

介绍一个现代化的普物实验--液晶光阀

介绍了晶光阀实验的原理、内容、方法和结果,着重讨论了该实验作为一个新的现代化的普通物理实验的优点。     

棱镜晶体旋转法测量液晶器件大预倾角

晶体旋转法是测量液晶分子预倾角的常用方法,但不适用于测量20°~70°之间的预倾角。提出一种棱镜辅助晶体旋转法测量预倾角的方案。把液晶盒夹在两个直角棱镜间,入射光从前面棱镜一个面入射,经过液晶盒从后面棱镜出射,改变入射光的入射角,测量出射光透过率,能得到对应双折射相位差为零、透射光强最大的入射角,进而由几何光学关系确定预倾角。数值模拟和实验结果显示该方法具有可行性。     

ON THE SATURATION BEHAVIOUR OF TWISTED NEMATIC LIQUID CRYSTAL CELLS WITH A NONZERO PRETILT ANGLE

Equations are obtained for the surface tilt angle and the twist angle of the director in a twisted nematic liquid crystal cell under a high magnetic field. Under a zero pretilt angle, the two equations reduce to those obtained by Sugimura et al. This fact has also been demonstrated numerically. With finite field strength and nonzero pretilt angle, no saturation transition exists.     

Dynamics of reorientation of a constrained nematic elastomer

A model is proposed for the reorientation dynamics of a confined nematic liquid crystal elastomer, where the effect of crosslinks is to couple the director to deformations of the elastic matrix. The model combines the (equilibrium) `neo-classical' theory of liquid crystal rubber elasticity with the simplest time evolution equations for a system described by two coupled, non-conserved order parameters. Relaxation from an orientation imposed by an electric field is studied as a function of elastic softness, starting angle, surface pretilt, and the relative mobilities of director and strain. Most importantly, the absence of a `semi-soft' elastic threshold changes the long-time behaviour of the effective refractive index of the medium from exponential to inverse power law decay. Predictions are compatible with recent experimental results by Chang, Chien and Meyer [Phys. Rev. E 56, 595 (1997)]. Received 22 June 1998     

The Effect of Pretilt and Twisted Angle on Twisted Nematic Liquid Crystal Filter

The effect of pretilt and twisted angle on twisted nematic liquid crystal filter (TNLCF) is studied theoretically and experimentally in this paper, based on the birefringence and distortion characteristic of twisted nematic liquid crystal, the output performance of TNLCF has been analyzed through numerical simulation firstly, then the corresponding experiment results verify the correctness of the simulation results, which show that the output performance of TNLCF is indeed related to pretilt angle and twisted angle of liquid crystal–with the increasing of the twisted angle the central wavelength of TNLCF will shift to the long wavelength, with the increasing of pretilt angle for the top glass substrate and the decreasing of pretilt angle for the bottom glass substrate the central wavelength of TNLCF will shift to the short wavelength, and if the pretilt angle of the bottom glass substrate is increased and the pretilt angle of the top glass substrate is reduced at the same time in some certain value or otherwise the shift trend of the central wavelength will be not evident. These results will offer an important reference value for the design and application of TNLCF as we believe.