一种新的测量扭曲向列相液晶盒盒厚和扭曲角的Stokes矢量法

Novel Stokes Parameter Method for Determination of Cell Thickness and Twist Angle of Twisted Nematic Liquid Crystal Cells

提出了一种新的测量扭曲向列相液晶盒盒厚和扭曲角的Stokes矢量法。根据Jones矩阵推导出了Stokes矢量与液晶盒参数的关系,其原理是通过确定经过液晶盒之后偏振光的偏振特性来求解液晶盒盒厚和扭曲角。该方法在测量一个Stokes矢量时,在液晶盒后依次放两种波片,目的是改变经过液晶盒后的光的偏振态,再置一偏振分光棱镜分开水平Ip和垂直Is线偏振分量,测得两组光强,根据公式算得该Stokes矢量,从而求解液晶盒盒厚以及扭曲角。实验中我们用该方法测量了不同盒厚、扭曲角度的TN液晶盒。实验结果证明该方法可行,结果准确,并且可以测量盒厚较小的液晶盒。最后,我们理论分析了实验误差。

A novel method of determining the cell thickness and the twist angle of twisted nematic liquid crystal（TNLC）cells by measurement of Stokes parameters of light transmitted through the cell is presented.The relationships of the Stokes parameters of transmission light to the cell thickness and the twist angle are determined by use of Jones matrix representation.The main principle is that utilizing the polarization properties of transmission light to determine the cell thicknesses and twist angles of TNLC cells.In this method,when measuring a Stokes parameter,two kinds of waveplates is put behind TNLC cell in turn to change the polarization of light that travelling through the liquid crystal cell.Then a polarizer beam splitter is used to disjoin linear polarization components Ip and Is in the horizontal and vertical directions.Finally,two group data will be detected and then used to solve the Stokes parameter,thereby the cell thickness and the twist angle are determined.The cell thickness and the twist angle of some TNLC cells are determined practically by this simple method.The experimental results indicate that this method is valid,even thin thickness of TNLC cells can be determined.Furthermore,some properties of this method are discussed and an accuracy analysis by theoretical calculation is undertaken.