Low-Cell-Gap Measurement by Rotation of a Wave Retarder

Abstract

A simple method of measuring the cell gap of a low-cell-gap twisted nematic liquid crystal (TNLC) cell is proposed. Unlike the conventional methods which make use of a rotatable polarizer and analyzer or a compensator set between a pair of crossed polarizers, the proposed method uses a wave plate set on top of a motor by which we rotate the plate by 360°. With the proposed method, we can measure the cell gap of TNLC cells with a low cell gap below 4 µm. The proposed method can also be applied to single-polarizer reflective LC cells.