Optical system for three color liquid crystal light valve image

Abstract

A two lens optical system for a three primary color liquid crystal light valve image projection system. The first lens projects the red and green primary colors, while the other lens projects the blue primary color. The light from the illumination system is partially prepolarized by a first prism before being split into two optical paths by a first beam splitter. Red light having a first and second polarization and green light having a first polarization is transmitted along a first optical path to a second, or main beam splitter, from the first beam splitter. The red light is transmitted to a first light valve, the green light being reflected to a second light valve. With the first and second light valves 'on' state, the light incident thereon is directed back to the main beam splitter, recombined and then directed to the first projection lens. Green and blue light of the second polarization is reflected along a second optical path by the first beam splitter, the blue color light being transmitted through a third beam splitter to a third light input valve. The third light valve 'on' state, the blue light incident thereon is directed to the third beam splitter and then to the second projection lens. By utilizing the two different optical paths, high image contrast is achieved. The optical system utilizes a minimum of optical components such that light losses in the system are reduced, thus increasing overall system collection efficiency.