Improving the quality of liquid-crystal projection image by multilevel diffractive grating technique

Abstract

A technique using multilevel diffractive gratings to suppress the discrete nature of liquid crystal display (LCD) projection images is demonstrated. The multilevel diffractive gratings, having a cross section similar to a staircase, are fabricated by VLSI processes and plastic molding. Upon positioning the diffractive gratings on the front surface of the LCD panel, the output light beams emitted from each pixel are diffracted mainly into the zeroth and the +/-first diffraction order light beams of equal energy. The light beams transformed by the diffractive gratings into orders higher than zeroth are able to fill up the dead space between each subpixel, and generate an array of images from each subpixel. As a result, the spatial frequency of the color subpixel distribution within the whole image is increased. Accordingly, the grain-like pixel structure in projection images is removed, at a slight expense of image resolution.