Full-color subtractive light valve for display applications

Abstract

A full-color miniature light valve is being investigated for display applications. The light valve is based on a subtractive rather than an additive approach to color mixture. In utilizing a subtractive color approach, a full-color information display is created using a single broadband light source whose energy passes through a stack of three thin liquid crystal cells.Each cell contains a different dichroic dye (e.g. cyan, magenta, and yellow) in a guest/host arrangement with the liquid crystal medium. Each dichroic guest/host liquid crystal cell constitutes an electronic color filter, switchable by the application of an appropriate voltage across the two plates of the cell. In one extreme state, the cells simply pass all spectral components of the light, while in the other extreme state the spectral composition of light passing through the cells is altered by the particular dichroic dye so that the complementary color of the dye is blocked or subtracted from passage through the cell.Voltages between the extremes produce the gradations in spectral throughput required for fullcolor operation. The achievable color gamut will be approximately equal to a shadow-mask color CRT.With a pixel addressing mechanism in each of the cells, a full color information display is created with complete color control at each individual pixel.