Projector

• US 5,153,752 A
• Filed: 02/20/1991
• Issued: 10/06/1992
• Est. Priority Date: 02/22/1990
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Yanagi, Haruyuki, Mitsutake, Hideaki, Kanashiki, Masaaki, Kurematsu, Katsumi, Minoura, Nobuo
• Primary Examiner(s): Epps, Georgia Y.
• Application Number:
  US07/658,046
• Time in Patent Office: 594 Days
• Field of Search: 353/31, 353/34, 358/60, 358/61, 359/34, 359/40, 359/41, 359/62, 359/63, 359/64, 359/70, 359/246, 359/247, 359/253, 359/281
• US Class Current: 349/9
• CPC Class Codes: H04N 9/3167 for polarizing the light beam polarizing optical systems per se G02B27/28

Abstract

A liquid crystal type video projector is disclosed which has a reflection type optical modulator for effective use of beams from a radiation source such as a lamp or the like. The projector further comprises means for modulating the plane of polarization of a polarized beam entering the radiation source and for reflecting the polarized beam, thereby causing a reflection beam and an optical arrangement. The optical arrangement includes a first polarizing beam splitter for separating the beam from the radiation source into P and S polarized components and for directing the S polarized component to the modulator and a converter for rotating the plane of polarization of the P polarized component and converting into another S polarized component for enhanced efficiency of beam utilization. It further includes a second polarizing beam splitter for reflecting the other S polarized component and directing the other S polarized component and directing to the modulator. The polarizing beam splitters are caused to act as an analyzer for colored reflected beams via a dichroic mirror system.

Claims

1. A projector comprising:

a radiation source;

an illuminating system having an arrangement of first and second polarizing beam splitters and a phase plate, dividing surfaces of both of said polarizing beam splitters being parallel with each other, the phase plate being arranged between both of said dividing surfaces, the first polarizing beam splitter reflecting an S-polarized beam of a white beam emitted from said radiation source and transmitting a P polarized beam of the white beam to be directed to the phase plate, the second polarizing beam splitter reflecting another S-polarized beam generated by the phase plate;

a dichroic mirror system for receiving the S-polarized beams from said arrangement;

a first optical modulator for generating a first reflected beam indicative of a first image by modulating the plane of polarization of a red component of the S-polarized beams from the mirror system and reflecting said red component;

a second optical modulator for generating a second reflected beam indicative of a second image by modulating the plane of polarization of a green component of the S-polarized beam from the mirror system and reflecting said green component;

a third optical modulator for generating a third reflected beam indicative of a third image by modulating the plane of polarization of a blue component of the S-polarized beam from the mirror system and reflecting said blue component; and

a projection optical system for receiving said first to third reflected beams through the mirror system and both of the dividing surfaces of said polarizing beam splitters and for projecting a color image by said first to third reflected beams, wherein said polarizing beam splitters are caused to act as an analyzer for said first to third reflected beams.

2. A projector according to claim 1, wherein the phase plate has a half wavelength film.

3. A projector according to claim 1, wherein the phase plate has a 90°

twisted nematic liquid crystal layer.

4. A projector according to claim 1, wherein the first to third optical modulators have liquid crystal layers for rotating the polarizing planes of the beams in accordance with the video signal.

5. A projector according to claim 1, wherein the phase plate is arranged close to the dividing surface of the first polarizing beam splitter.

6. A projector according to claim 1, wherein each of the first and second polarizing beam splitters has a cube-like outer shape and the phase plate is sandwiched by both of said polarizing beam splitters.

7. A projector according to any one of claims 1 to 6, wherein the dichroic mirror system comprises cross dichroic mirrors.

8. A projector comprising:

a radiation source;

an illuminating system having an arrangement of first, second and third polarizing beam splitters and a phase plate dividing surfaces of the first and second polarizing beam splitters being parallel with each other, the phase plate being arranged between both of said dividing surfaces, the first polarizing beam splitter reflecting an S-polarized beam of a white beam emitted from the radiation source to be directed to the third polarizing beam splitter and transmitting a P-polarized beam of the white beam to be directed to the phase plate, the second polarizing beam splitter reflecting another S-polarized beam generated by the phase plate to be directed to the third polarizing beam splitter, the third polarizing beam splitter directing the S-polarizing beams to a path;

a dichroic mirror system disposed in the path, for receiving the S-polarized beams from the third polarizing beam splitter;

a first optical modulator for generating a first reflected beam indicative of a first image by modulating the plane of polarization of a red component of the S-polarized beam from the mirror system and reflecting said red component;

a second optical modulator for generating a second reflected beam indicative of a second image by modulating the plant of polarization of a green component of the S-polarized beam from the mirror system and reflecting said green component;

a third optical modulator for generating a third reflected beam indicative of a third image by modulating the plane of polarization of a blue component of the S-polarized beam from the mirror system and reflecting said blue component; and

a projection optical system for receiving the first to third reflected beams through the mirror system and the third polarizing beam splitter and for projecting a color image by said first to third reflected beams, wherein said third polarizing beam splitter is caused to act as an analyzer for said first to third reflected beams.

9. A projector according to claim 8, wherein the phase plate has a half wavelength film.

10. A projector according to claim 8, wherein the phase plate has a 90°

twisted nematic liquid crystal layer.

11. A projector according to claim 8, wherein the first to third optical modulators have liquid crystal layers for rotating the polarizing planes of the beams in accordance with the video signal.

12. A projector according to claim 8, wherein the phase plate is arranged close to the dividing surface of the first polarizing beam splitter.

13. A projector according to claim 8, wherein each of the first and second polarizing beam splitters has a cube-like outer shape and the phase plate is sandwiched by both of said polarizing beam splitters.

14. A projector according to claim 8, wherein the illuminating system has a bending mirror and both of the S polarizing components are led to the third polarizing beam splitter by said bending mirror.

15. A projector according to any one of claims 8 to 14, wherein the dichroic mirror system comprises cross dichroic mirrors.

16. An optical modulation system comprising:

a radiation source;

modulator for modulating the plane of polarization of a polarized beam entered therein and for reflecting said polarized beam to thereby generate a reflected beam; and

an optical arrangement having a first polarizing beam splitter for dividing beam from the radiation source into P- and S-polarized components and directing the S-polarized component to the modulator, a converter for rotating the plane of polarization of the P-polarized component and converting into another S-polarized component, and a second polarizing beam splitter for reflecting said another S-polarized component to be directed to the modulator.

wherein said polarized beam is found by both of said S-polarized components, and said first and second polarizing beam splitters are caused to act as an analyzer for the reflected beam.

17. A system according to claim 16 further having a projection optical system for projecting the reflected beam from the polarizing beam splitters in a predetermined direction.

18. A system according to claim 17, wherein the modulator executes the modulation in accordance with a video signal and a projection optical system projects an image by the reflection beam.

19. A system according to claim 16, wherein the optical arrangement has an optical system for leading the beam from the radiation source to the first polarizing beam splitter.

20. A system according to claim 16, wherein the polarizing beam splitters and the converter are integratedly arranged.

21. A projector comprising:

a radiation source;

an illuminating system having an arrangement of first polarizing beam splitter and a reflecting surface, a phase plate, and a second polarizing beam splitter, a dividing surface of the first polarizing beam splitter and the reflecting surface being parallel with each other, the first polarizing beam splitter reflecting an S-polarized beam of a white beam from the radiation source to be directed to the second polarizing beam splitter and transmitting a P-polarized beam of the white beam to be directed to the reflecting surface, the reflecting surface reflecting the P-polarized beam to be directed to the second polarizing beam splitter, wherein said phase plate makes polarized directions of both of the polarized beams to coincide with each other, and said second polarizing beam splitter directs the polarized beam to a path;

a dichroic mirror system, disposed in the path, for receiving the polarized beams from said arrangement;

a first optical modulator for generating a first reflected beam indicative of a first image by modulating the plane of polarization of a red component of the S-polarized beams from the mirror system and reflecting said red component;

a second optical modulator for generating a second reflected beam indicative of a second image by modulating the plane of polarization of a green component of the S-polarized beams from the mirror system and reflecting said green component;

a third optical modulator for generating a third reflected beam indicative of a third image by modulating the plane of polarization of a blue component of the S-polarized beams from the mirror system and reflecting said blue component; and

a projection optical system for receiving the first to third reflected beams through the mirror system and the third polarizing beam splitter and for projecting a color image by said first to third reflected beams, wherein said third polarizing beam splitter is caused to act as an analyzer for said first to third reflected beams.

22. A projector according to claim 21, wherein the phase plate has a half wavelength film.

23. A projector according to claim 21, wherein the phase plate has a 90°

twisted nematic liquid crystal layer.

24. A projector according to claim 21, wherein the phase plate is arranged on a path of the S polarizing component from the first polarizing beam splitter and converts the S polarizing component into another P polarizing component, thereby making polarizing directions of both of said polarizing components coincide.

25. A projector according to claim 24, wherein the illuminating system has a bending mirror, and by reflecting the P polarizing component and said another P polarizing component by said bending mirror, both of said polarizing components are led to the second polarizing beam splitter as an S polarizing beam.

26. A projector according to claim 21, wherein the phase plate is arranged on a path of the P polarizing component from the first polarizing beam splitter, and by converting the P polarizing component into another S polarizing component, polarizing directions of both of said polarizing components coincide.

27. A projector according to claim 21, wherein the first to third optical modulators have liquid crystal layers for rotating the polarizing planes of the beams in accordance with a video signal.

28. A projector according to any one of claims 21 to 27, wherein the dichroic mirror system comprises cross dichroic mirrors.

29. An optical modulator system comprising:

a radiation source;

a modulator for generating a reflected beam by rotating the plane of polarization of a polarized beam entered therein and reflecting said polarizing beam;

an optical arrangement for generating said polarized beam by dividing beams from said radiation source into a P-polarized component and an S-polarized component whose polarized planes are orthogonal to each other, and causing the polarized directions of said P- and S-polarized components to be coincident with each other; and

a polarizing beam splitter for receiving said polarized beam from said optical arrangement to be directed to said modulator, wherein said polarizing beam splitter is made act as an analyzer for said reflected beam from said modulator.

30. A system according to claim 29 further comprising a projection optical system for projecting said reflected beam from said polarizing beam splitter in a predetermined direction.