The cholophor: A passive polarization-switched liquid crystal screen for multicolor laser displays

Cholophors are passive polarization-switched color display elements suitable for use with lasers or white light. Their hybrid structure, consisting of a thin layer of cholesteric liquid crystal over a layer of photoluminescent phosphor, provides properties of particular interest for large-screen optically scanned multicolor display applications. Cholophors permit more efficient use of available laser power while providing a solution to the problem of color registration for two-primary displays and a partial solution for three-primary displays. Two-primary or Land-color displays can be obtained with only one color of laser light and three-primary displays with only two colors. A three-primary cholophor display using a single argon ion laser would have over 7 times the efficiency of a typical state-of-the-art system using an argon-krypton mixed-gas laser. The liquid crystal layer provides polarization selectivity, and the phosphor layer produces the additional color not furnished by the laser. The liquid crystal transmits one sense of laser polarization while totally reflecting the other, thereby permitting polarization selective excitation of the underlying phosphor. The color selection information is coded into the polarization of the incident laser beam.