Patent ID: 6980260

Claim:
An optical system for a reflection type liquid crystal projector arranged to a split a beam of uniformly polarized white illuminating light, which is projected from a light source, into first, second and third wavelength components of three primary colors, to reflect said three wavelength components, respectively, by means of liquid crystal display panels to produce image light of the first, second and third wavelength components, and to synthesize the image light of said wavelength components together for projection as a full-color image, the optical system comprising: a dichroic mirror adapted to separate a first wavelength component of said white illuminating light from second and third wavelength components; a first polarizing beam splitter including a polarizing surface adapted to transmit or reflect said first wavelength component of said illuminating light toward a first liquid crystal display panel adapted to reflect image light of said first wavelength component; a half-wave plate adapted to rotate a plane polarization of one of said second and third wavelength components through 90 degrees on passage therethrough, without rotating a plane of polarization of the other wavelength component; a second polarizing beam splitter including a polarizing surface adapted to reflect or transmit said second wavelength component of the illuminating light from said half-wave plate toward a second liquid crystal display panel adapted to reflect image light of said second wavelength component, while transmitting or reflecting the third wavelength component of the illuminating light toward a third liquid crystal display panel adapted to reflect image light of said third wavelength component of the illuminating light; and a dichroic prism adapted to synthesize the image light of the first to third wavelength components coming in from said first and second polarizing beam splitters; wherein said polarizing surfaces of said first and second polarizing beam splitters are adapted to reflect s-polarization light and transmit p-polarization light; and said dichroic prism is adapted to reflect the image light of said first wavelength component and to transmit the image light of said second and third wavelength components, said image light of said first and third wavelength components being s-polarization light and said image light of said second wavelength component being p-polarization light when transmitted or reflected by said dichroic prism.