Liquid crystal cell design of VGA field sequential color LCoS display

Abstract

The design of liquid crystal cell is an important factor to determine the display quality of LCoS display device. The goal of this paper is to gain VGA field sequential color (FSC) LCoS device used for near-to-eye system. The characteristics of optics and electrooptics for the twist nematic liquid crystal material and the material requirements of the FSC LCoS were studied. The LCOS liquid crystal cell optimized by dynamic parameter space method had an uniform reflectivity (about 90%) for the light with wave length from 450nm to 650nm. Both considering the electrooptic response curve of liquid crystal and the relationship between the contrast ratio and pixel size, we determined to use high speed twist nematic liquid crystal working in normally white mode. The liquid crystal cell gap and the pixel size were determined as 2.5um and 12um, respectively. The VGA FSC LCoS device was fabricated with SMIC 0.35um CMOS process and filled with LC-A liquid crystal of Merck in Varitronix. The measurement showed that the response time of liquid crystal from light to dark was 1.8ms and from dark to light was 4.4ms. The contrast ratio is bigger than 50:1. The LCoS displays well.