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

A technique using multilevel diffractive gratings to suppress the discrete nature of liquid crystal display (LCD) projection images is demonstrated. T he multilevel diffractive gratings, having a cross section similar to a sta ircase, are fabricated by VLSI processes and plastic molding. Upon position ing the diffractive gratings on the front surface of the LCD panel, the out put light beams emitted from each pixel are diffracted mainly into the zero th and the +/-first diffraction order light beams of equal energy. The ligh t beams transformed by the diffractive gratings into orders higher than zer oth 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 o f the color subpixel distribution within the whole image is increased. Acco rdingly, the grain-like pixel structure in projection images is removed, at a slight expense of image resolution.