Characterization and optimization of silicon light valves for high-definition projection display

Liquid-crystal-on-silicon (LCOS) light valve has recently been recognized as an alternative approach for the fabrication of active matrix liquid crystal display (AMLCD). The major advantage is matured silicon fabrication technology. Very advanced display drivers and fine pixels can be integrated together as a self-contained and high-resolution display. The aperture ratio of the silicon light valve can be higher than 90% for good light efficiency and picture quality. As a result, the silicon light valve is very suitable for high-definition projection display, and has merits of high resolution, superior picture quality, high light efficiency and low power consumption. However, the silicon light valve used in projection display has a drawback in flicker. In this dissertation research, systematic approaches were used to study flicker mechanisms in silicon light valves. Four experiments were designed, and a variety of silicon light valve samples were prepared for the characterizations. It was found that there were five conduction mechanisms accounting for the flicker. They were residual DC charge on silicon surface, voltage holding capability of liquid crystal cell, voltage holding capability of silicon panel, light leakage and parasitic capacitor coupling. Through the systematic characterizations, major causes of flicker were identified. An empirical model of flicker was proposed with quantitative experimental data and theories. Solutions of flicker minimization were obtained. Among these solutions, offset of common voltage was found very useful to compensate for residual DC charge and parasitic capacitor coupling. Frame rate multiplication was found very useful for reducing the flicker due to low voltage holding capabilities of liquid crystal cell and silicon panel. Material and device optimization could also help minimize the flicker in different manners. With all these optimizations, flicker-free high-definition projection displays based on silicon light valve were demonstrated