Multicolor projector employing diffraction grating type liquid crystal light modulators

Claim 1

A projector comprising an illumination system including, a light source emitting a white light, a conversion system for converting said white light into a polarized light, and a color separation system for splitting said polarized light into red, green and blue lights for generating first, second and third lights of mutually different colors; light modulation means including, a first light modulator for modulating said first light according to a first image, a second light modulator for modulating said second light according to a second image, a third light modulator for modulating said third light according to a third image, wherein each of said first, second and third light modulators is provided with a grating including grooves liquid crystal filled in the grooves of said grating and a driver for driving molecules of said liquid crystal, said driver being adapted to drive the molecules of liquid crystal in such a manner that the liquid crystal and the grating have mutually substantially matching refractive indexes in a certain state but have mutually unmatched refractive indexes in another state, thereby generating or substantially erasing a diffraction grating by said grating and said liquid crystal, said first and second light modulators are positioned in a mutually common optical path, different from the optical path in which said third light modulator is positioned, betwen said illuminating system and said projection optical system, are arranged in such a manner that the direction of grooves of said gratings are mutually substantially perpendicular, and are adapted to orient said molecules of the liquid crystal along the grooves of said gratings in said another state; a projection optical system for projecting a first and second images of mutually different colors by said first and second lights from said first and second light modulators, said projection optical system further adapted to project a third image of a color different from those of said first and second lights, by said third light from said third light modulator, and superposes said third image with said first and second images; and said illuminating system is adapted to rotate the polarizing plane of one of said first and second lights from said color separation system substantially perpendicularly to the polarizing plane of the other, thereby substantially matching the polarizing plane of the first light with the direction of grooves of said grating of said first light modulator and substantially matching the polarizing plane of said second light with the direction of grooves of said grating of said second light modulator, and direct said first and second lights to said common optical path and said third light to said optical path in which said third light modulator is positioned.