Reflection type liquid crystal projector
While illuminating light is separated into a first wavelength component illuminating light and second and third wavelength component illuminating lights by a dichroic mirror, the first illuminating light is reflected off a first liquid crystal display element to form a first wavelength component image light which is then reflected off or passed through the polarizing surface of a first polarizing beam splitter, whereas one of the second and third wavelength component illuminating lights has its polarizing surface 90°-converted by a ½ phase difference plate, the other one is passed through the plate without having its polarizing surface converted, the second and third wavelength components are separated from each other by a second polarizing beam splitter and respectively reflected off second and third liquid crystal display elements to obtain second.
1. 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.
2. An optical system for a reflection type liquid crystal projector as defined in claim 1 , wherein said illuminating light beam from said light source is p-polarization light,
said dichroic mirror is adapted to transmit said first wavelength component and to reflect said second and third wavelength components of the illuminating light,
said polarizing surface of said first polarizing beam splitter is adapted to transmit said first wavelength component of the illuminating light toward said first liquid crystal display panel and to reflect said image light of said first wavelength component received from said first liquid crystal display panel,
said half-wave plate is adapted to direct said second and third wavelength components of the illuminating light toward said second polarizing beam splitter as s-polarization light and p-polarization light, respectively,
said polarizing surface of said second polarizing beam splitter is adapted to reflect said second wavelength component of s-polarization light toward said second liquid crystal display panel and to transmit said third wavelength component of p-polarization light toward said third liquid crystal panel,
said second polarizing beam splitter is adapted to transmit said image light of said second wavelength component received from said second liquid crystal display panel and to reflect image light of said third wavelength component received from said third liquid crystal display panel.
3. An optical system for a reflection type liquid crystal projector as defined in claim 2 , wherein said first, second and third wavelength components of the illuminating light are blue, green and red components, respectively.
4. An optical system for a reflection type liquid crystal projector as defined in claim 2 , wherein said first, second and third wavelength components of the illuminating light are red, green and blue components, respectively.
5. An optical system for a reflection type liquid crystal projector as defined in claim 1 , wherein said illuminating light beam from said light source is s-polarization light, said dichroic minor is adapted to transmit said first wavelength component and reflect said second and third wavelength components of the illuminating light, another half-wave plate is positioned in front of said first polarizing beam splitter thereby to convert the first wavelength component into p-polarization light, letting same pass through said first polarizing beam splitter toward said first liquid crystal display panel and reflecting the image light of the first wavelength component from said first liquid crystal display panel by said first polarizing beam splitter, said half-wave plate in front of said second polarizing beam splitter is adapted to direct said second and third wavelength component of the illuminating light toward said second polarizing beam splitter as s-polarization light and p-polarization light, respectively, and said polarizing surface of said second polarizing beam splitter is adapted to reflect wavelength component of s-polarization light toward said second liquid crystal display panel for reflection by the panel and transmit said third wavelength component of p-polarization light through toward said third liquid crystal display panel for reflection by the panel, then transmitting and reflectingimage light of said second and third wavelength components reflected from said second and third liquid crystal display panels, respectively.
6. An optical system for a reflection type liquid crystal projector as defined in claim 1 , wherein said half-wave plate is provided as a film formed on a light incident surface of said second polarizing beam splitter.
7. An optical system for a reflection type liquid crystal projector as defined in claim 1 , wherein optical elements of said first and second polarizing beam splitters and said dichroic prism are bonded together and integrated into a unitary optical structure in such a way as to eliminate boundary surfaces between said optical elements.