The Application of GaAlAs Lasers to High-Resolution Liquid-Crystal Projection Displays

In this review we describe a high-resolution liquid-crystal (LC) display that uses multiple GaAlAs lasers to write on the LC cell. Arrays of high-powered lasers were needed to meet the writing speed requirements of the display. A fiber optic delivery system was developed to allow high-resolution, multi-spot writing on the cell, regardless of the laser configuration used. The fiexibility and unconstrained length of the fiber optics also permitted simplification in the design of the scanner system which moved the optical beams over the LC cell. Because of the proximity of the injection laser's wavelength to the visible spectrum used in the display projection system and because of divergence of the beams in the optical delivery system, a reflective LC cell was designed. Almost total absorption of the GaAlAs laser beam was achieved. This paper discusses the thermal and optical properties of the cell and their effect on the writing characteristics and the quality of the projected image (contrast and brightness). An off-axis projection system, which was designed for use with the reflective cell, creates a high-resolution image on the screen.