Grating-Type Soft-Focus Filter for Improving Picture Quality of Liquid Crystal Displays

A grating-type soft-focus filter was fabricated from a polymer film to transform the discontinuous picture of a liquid crystal display (LCD) into a continuous one. The soft-focus filter having a two-dimensional grating pattern with a sinusoidal cross section was photochemically formed on the film by proximity exposure through a photomask to ultraviolet light. When the LCD surface was covered with the soft-focus filter, the output light beam from the LCD was transformed into mainly nine beams as a result of (0, 0)- to (±1, ±1)-order diffractions with nearly equivalent intensities. Thereby, the picture discontinuity caused by the black matrix of the LCD was removed at a small expense of picture contrast.