Reflective projector

• US 6,478,429 B1
• Filed: 04/08/1999
• Issued: 11/12/2002
• Est. Priority Date: 10/29/1998
• Status: Expired due to Fees

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Matsumoto, Tsuyoshi, Aritake, Hirokazu, Yamagishi, Fumio, Eguchi, Shin
• Primary Examiner(s): DOWLING, WILLIAM C
• Application Number:
  US09/289,143
• Time in Patent Office: 1,314 Days
• Field of Search: 353/31, 353/33, 353/34, 353/37, 353/69, 353/70, 353/97, 349/5, 349/8, 349/9
• US Class Current: 353/31
• CPC Class Codes: G02B 27/123 The splitting element being a lens or a system of lenses, including arrays and surfaces with refractive power
• CPC Class Codes: G02B 27/145 having sequential partially reflecting surfaces
• CPC Class Codes: G02B 27/149 using crossed beamsplitting surfaces, e.g. cross-dichroic cubes or X-cubes
• CPC Class Codes: H04N 9/3105 for displaying all colours simultaneously, e.g. by using two or more electronic spatial light modulators simultaneous projection in colour photography G03B33/10; beam splitting or combining systems per se G02B27/10
• CPC Class Codes: H04N 9/3167 for polarizing the light beam polarizing optical systems per se G02B27/28

Abstract

A reflective projector includes a light source, reflective liquid crystal panels, a dichroic prism for separating a light beam from the light source into light beams of predetermined colors by using interference and for synthesizing the light beams of predetermined colors into a light beam, and a projection lens. The reflective projector further includes a first polarizer provided between the light source and the reflective liquid crystal panels and a second polarizer provided between the reflective liquid crystal panels and the projection lens.

Claims

1. A reflective projector comprising:

an illumination system for generating an illumination light beam with predetermined wavelengths;

a plurality of reflective display elements for generating image light beams by reflecting said illumination light beam emitted from said illumination system;

a polarization controlling element for changing polarization of a predetermined wavelength of light emitted from said illumination system;

a color separation/synthesis unit for separating said illumination light beam into light beams of predetermined colors and for synthesizing said image light beams from said reflective display elements;

a projection lens for projecting said synthesized image light beams;

wherein said reflective projector is formed such that said illumination light beam impinges on a light entering/exiting surface which is one of a plurality of surfaces of said color separation/synthesis unit and said image light beam exits from said light entering/exiting surface toward said projection lens; and

wherein said illumination light beam and said image light beam are separated by controlling an entry angle of said illumination light beam or an exiting angle of said image light beam with respect to said color separation/synthesis unit, or by controlling an entry angle of said illumination light beam or an exiting angle of said image light beam with respect to each of said reflective display elements.

2. The reflective projector as claimed in claim 1, wherein said illumination light beam impinges on said color separation/synthesis unit such that the optical axis of said illumination light beam is parallel to a plane which is parallel to a color separation direction defined by said color separation synthesis unit.

3. The reflective projector as claimed in claim 1, wherein said illumination light beam impinges on said color separation/synthesis unit such that the optical axis of said illumination light beam intersects a plane which is parallel to a color separation direction defined by said color separation/synthesis unit.

4. The reflective projector as claimed in claim 3, wherein the area on which said illumination light beam impinges is separat ed from the area from which said image light beam exits in said light entering/exiting surface, the optical system from said illumination system to said projection lens being formed to be an anamorphic system.

5. The reflective projector as claimed in claim 3, wherein the area on which said illumination light beam impinges is separated from the area from which said image light beam exits in said light entering/exiting surface, the optical system from said illumination system to said projection lens being formed to be axially symmetric with respect to the optical axis of the optical system.

6. The reflective projector as claimed in claim 3, wherein the area on which said illumination light beam impinges overlaps with the area from which said image light beam exits in said light entering/exiting surface, the optical system from said illumination system to said projection lens being formed to be an anamorphic system.

7. The reflective projector as claimed in claim 3, wherein the area on which said illumination light beam impinges overlaps with the area from which said image light beam exits in said light entering/exiting surface, the optical system from said illumination system to said projection lens being formed to be axially symmetric with respect to the optical axis of the optical system.

8. The reflective projector as claimed in claim 3, wherein said color separation/synthesis unit includes a dichroic cross prism which has reflection characteristics depending on polarization for color separation and is formed such that reflected polarized light and transmitted polarized light are different in polarization.

9. The reflective projector as claimed in claim 8, wherein said polarization controlling element has wavelength selection characteristics for filtering light of predetermined wavelengths.

10. The reflective projector as claimed in claim 9, wherein said polarization controlling element generates light of wavelengths for green which light has a polarization vector plane parallel to the color separation direction of said dichroic cross prism, and said polarization controlling element generates light of wavelengths for red and blue which light has a polarization vector plane perpendicular to the color separation direction of said dichroic cross prism.

11. The reflective projector as claimed in claim 9, wherein said polarization controlling element comprises:

a first element having a selected wavelength reflection layer for reflecting light of predetermined wavelengths;

a second element having a selected wavelength reflection layer for reflecting light of predetermined wavelengths; and

a circular polarization generating element provided between said first element and said second element.

12. The reflective projector as claimed in claim 11, wherein said circular polarization generating element comprises a plurality of λ

/4 sheets.

13. The reflective projector as claimed in claim 11, wherein the surface on which said selected wavelength reflection layer is formed is flat or curved.

14. The reflective projector as claimed in claim 3, further comprising a wavelength selection element, provided in said illumination system, for generating light of predetermined wavelengths, wherein said color separation/synthesis unit includes a dichroic cross prism which is formed such that reflected polarized light and transmitted polarized light have the same polarization.

15. The reflective projector as claimed in claim 14, wherein said wavelength selection element comprises:

a first element having a selected wavelength reflection layer for reflecting light of predetermined wavelengths; and

a second element having a selected wavelength reflection layer for reflecting light of predetermined wavelengths.

16. The reflective projector as claimed in claim 15, wherein the surface on which said selected wavelength reflection layer is formed is flat or curved.

17. The reflective projector as claimed in claim 8, further comprising a prism or a wedge substrate, provided on a light entering/exiting surface of said dichroic cross prism, for suppressing aberration.

18. The reflective projector as claimed in claim 3, wherein said reflective display element comprises a time sharing display element.

19. The reflective projector as claimed in claim 18, wherein said time sharing display element is a micro-mirror device.

20. The reflective projector as claimed in claim 3, wherein said reflective display element comprises:

a phase modulation element for modulating phase of impinged light by reflection; and

a light intensity modulation element for modulating light intensity.

21. The reflective projector as claimed in claim 20, wherein said phase modulation element comprises a liquid crystal panel having a λ

/4 modulation amount and said light intensity modulation element comprises a polarizer.

22. The reflective projector as claimed in claim 20, wherein said phase modulation element comprises a liquid crystal panel for changing a direction of polarization by 90°

and said light intensity modulation element comprises a polarizer and a circular polarization generating element.

23. The reflective projector as claimed in claim 20, wherein the reflection surface of said reflective display element and said light intensity modulation element are in absolute contact with one another in parallel.

24. The reflective projector as claimed in claim 20, wherein the reflection surface of said reflective display element and said light intensity modulation element are separated.

25. The reflective projector as claimed in claim 20, wherein the reflection surface of said reflective display element and said light intensity modulation element form an angle with respect to the light entry angle to said reflection surface.

26. The reflective projector as claimed in claim 25, wherein a prism or a wedge substrate is provided on a surface of said color separation/synthesis unit which surface faces said reflective display element, and said light intensity modulation element is provided between said prism and said color separation/synthesis unit or between said wedge substrate and said color separation/synthesis unit.

27. The reflective projector as claimed in claim 25, wherein said light intensity modulation element is bonded to said color separation/synthesis unit.

28. The reflective projector as claimed in claim 26, wherein a gap is formed between said prism and said color separation/synthesis unit or between said wedge substrate and said color separation/synthesis unit.

29. The reflective projector as claimed in claim 3, wherein said illumination system comprises:

a polarization conversion optical system for converting polarization of a light beam emitted from said light source into a predetermined polarization; and

an integrated optical system which allows a light beam from said polarization conversion optical system to enter said color separation/synthesis unit in a slanting direction.

30. The reflective projector as claimed in claim 29, wherein said polarization conversion optical system comprises:

a lens array;

a polarization separation element for shifting light gathered by said lens array in one direction; and

a λ

/2 sheet array arranged in the same direction as the direction in which said polarization separation element spreads.

31. The reflective projector as claimed in claim 29, wherein said integrated optical system comprises:

a first lens array for converging a light beam emitted from said light source;

a second lens array for forming an image of the aperture of said first lens array in which the image has the same size as that of said reflective display element; and

a condenser lens for gathering a light beam which passes through said second lens array on said reflective display element.

32. The reflective projector as claimed in claim 3, further comprising a field lens between said reflective display element and said color separation/synthesis unit.

33. The reflective projector as claimed in claim 3, further comprising a cooling unit for cooling at least one of said reflective display element and said light intensity modulation element.