Application of a circularly homogeneously aligned liquid-crystal cell to real-time measurements of twist angles in twisted-nematic liquid-crystal cells

A novel system which employs a pair of circularly homogeneously aligned liquid crystal cells (CH-LC cells) for measuring the time-dependent twist angles of twisted-nematic liquid crystal (TN-LC) cells is proposed. A unique polarization-converting property of a CH-LC cell is discussed. A scheme of calculating the twist angle is derived by the Jones matrix. The applicability of the proposed system is confirmed by measuring the time-dependent twist angle of a TN-LC cell with partially saponified polyvinyl alcohol (PVA) films in real time. Two factors, on which the measurement accuracy depends, are discussed: deviations of the polarizer and the analyzer from both x and y-axes and the resolution of the measured transmission image. The measurement accuracy in this paper is estimated to be within about 1 degrees.