利用會聚光線在偏光儀上量測液晶預傾角

Abstract

本論文利用偏光儀測量水平配向液晶盒的預傾角；首先使用光彈調變式偏光儀作單點量測，將量測到的值與理論曲線進行擬合，以求得預傾角和液晶盒厚度。本文也比較了偏光儀量測與晶體旋轉法、外差干涉儀量測的結果，以確認其量測上的精確度。而後我們轉換為影像式偏光儀，影像式偏光儀是由偏光片、樣品、析光片所組成，利用電荷耦合元件量測三個析光片方位角的光強度即可推算出橢圓偏光參數的平面分布，故可對水平配向液晶盒作二維量測。在影像式偏光儀中加入一柱狀平凸透鏡可使平行擴束光聚光，因此不需要轉動液晶盒就可以量測到不同入射角的橢圓偏光參數，進而可推算出不同位置的液晶預傾角和厚度的變化。

The polarimetry can measure the pretilt angle of a homogeneous liquid crystal. According to the theoretical model, we can use the photoelastic modulated polarimetry to deduce the pretilt angle and cell gap by fitting the phase retardation measured at different incident angles. The results are comparable with the measurements of crystal rotation method and heterodyne interferometry. We also measured the two-dimensional ellipsometric parameters of a homogeneous liquid crystal by using a CCD. The three-intensity-measurement technique has been used to determine the ellipsometric parameters in a polarizer-sample-analyzer (PSA) imaging polarimetry. We can measure the pretilt angle by applying the convergent light emerging from a cylindrical plano-convex lens in this imaging polarimetry. Pretilt angle and cell gap in two dimensions can thereby deduce without rotating liquid crystal cell.