The parameters of a twisted-nematic liquid-crystal display (TN-LCD) are measured with no ambiguity when we measure the intensity transmittance of a system that simply consists of a TN-LCD, two polarizers, a quarter-wave plate, and a monochromatic beam. First we show analytically that the director angle can have a 90° ambiguity and the twist angle of the liquid-crystal molecules a 180° ambiguity. Then we uniquely measure the parameters by fitting the theoretical predictions to the intensity transmittance measured with and without the quarter-wave plate and by using the quasi local-adiabatic condition. The birefringence of the TN-LCD is measured next as a function of the applied voltage. We design a phase spatial light modulator by using the measured parameters and measure the phase delay of the output beam to excellent agreement with the theoretical prediction.
© 2005 Optical Society of America
Hyun Kim and Yeon H. Lee, "Unique measurement of the parameters of a twisted-nematic liquid-crystal display," Appl. Opt. 44, 1642-1649 (2005)