Two-Dimensional Distributions of Five Cell Parameters of Twisted Nematic Liquid Crystal Device by Numerical Photometric Ellipsometer

Abstract

A novel numerical photometric ellipsometer (NPE) under the condition of normal incidence and using a single wavelength laser beam is proposed wherein a continuously rotated quarter wave plate (QWP) at constant speed is required. To precisely measure the cell parameters of a twisted nematic liquid crystal device (TNLCD), the calibration of the QWP is necessary before measurement in this method. All five cell parameters of the TNLCD, namely, twisted angle, cell gap, rubbing angle, pretilt angle, and phase retardation, are obtained by least-square fitting of the measurement data versus the rotation angle of the QWP with the calculated intensity ratio of p- and s-polarization components according to our previously developed theory. The NPE can be extended to the two-dimensional distributions of all five cell parameters by using charge-coupled device (CCD) cameras. Experimentally, the results demonstrate the ability of the NPE to characterize the five cell parameters of the TNLCD in two dimensions with high accuracy and good repeatability.