Projection-type display device having light source means including a first and second concave mirrors

• US 5,142,387 A
• Filed: 04/09/1991
• Issued: 08/25/1992
• Est. Priority Date: 04/11/1990
• Status: Expired due to Term

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Kida, Hiroshi, Shikama, Shinsuke, Usui, Masahiro, Toide, Eiichi, Kondo, Mitsushige
• Primary Examiner(s): Miller, Stanley D.
• Assistant Examiner(s): MAI, HUY KIM
• Application Number:
  US07/682,626
• Time in Patent Office: 504 Days
• Field of Search: 350/338, 350/345, 350/334, 350/620, 350/630, 362/298, 362/302, 362/303, 359/49, 359/40, 359/41, 359/70, 353/122, 358/60, 358/61
• US Class Current: 349/9
• CPC Class Codes: F21V 7/0025 Combination of two or more reflectors for a single light source array of reflectors for a cluster of light sources F21V7/0083
• CPC Class Codes: F21V 7/04 Optical design
• CPC Class Codes: G02B 19/0028 refractive and reflective surfaces, e.g. non-imaging catadioptric systems
• CPC Class Codes: G02B 19/0047 for use with a light source G02B19/009, G02B19/0095 take precedence; details of lighting devices in general F21V; non-semiconductor lasers having optical devices external to the laser cavity H01S3/005
• CPC Class Codes: G02B 27/30 Collimators
• CPC Class Codes: G02B 5/005 Diaphragms for cameras G03B9/02
• CPC Class Codes: G02B 5/10 with curved faces
• CPC Class Codes: H04N 9/3152 for shaping the light beam beam shaping per se G02B27/09

Abstract

The projection-type display device has a light source emitting a parallel luminous flux, a liquid crystal light valve disposed on the luminous flux and outputs a rectangular two-dimensional image to be projected on a screen, and a projection lens magnifying the rectangular two-dimensional image output. The light source has a first concave mirror (parabolic mirror) the reflective surface of which is oriented in the direction of emission of the luminous flux, a lamp laced in front of the first concave mirror, and a second concave mirror (parabolic mirror or spherical mirror), the reflective surface of which is oriented toward the first concave mirror. In the second concave mirror is formed an aperture window, which is a rectangle of substantially similar to that of the liquid crystal light valve and emits a rectangular luminous flux. The beam from the lamp is reflected by the first concave mirror, and one or more times by the second concave mirror, becoming a parallel beam oriented in the direction of the optical axis. The parallel light beam is made into a luminous flux of rectangular cross section by the rectangular aperture window. Accordingly, luminous flux is not blocked wastefully, but serves to increase the brightness of the projected image.

Claims

1. A projection-type display device comprising:

light source means for emitting a parallel luminous flux in a single direction;

liquid crystal light valve means disposed in a path of the parallel luminous flux emitted from said light source means, having a rectangular display area, for outputting a rectangular two-dimensional image from the rectangular display area;

a projection lens for magnifying the two-dimensional image output from said liquid crystal light valve means and projecting the magnified image on a screen;

said light source means including,

a first concave mirror, a reflecting surface of which is oriented in the direction of emission of the parallel luminous flux,

a lamp placed in front of said first concave mirror, and

a second concave mirror, a reflecting surface of which is oriented toward said lamp and the reflecting surface of said first concave mirror, said second concave mirror having an aperture window that is of a rectangular configuration substantially similar to the configuration of the rectangular display area of said liquid crystal light valve means, for emitting a rectangular two-dimensional luminous flux, which is parallel to an optical axis of said first and second concave mirrors, toward said liquid crystal light valve means thereby increasing an amount of the parallel luminous flux which impinges on said liquid crystal light valve means and increasing the magnified two-dimensional image brightness.

2. The projection-type display device of claim 1, in which said first concave mirror is a first parabolic mirror, and said second concave mirror is a second parabolic mirror.

3. The projection-type display device of claim 2, in which an optical axis of said first parabolic mirror and an optical axis of said second parabolic mirror are in alignment, and a focal point of said first parabolic mirror and a focal point of said second parabolic mirror are collocated.

4. The projection-type display device of claim 3, in which said lamp has a center of luminescence which is located at said focal point of said first parabolic mirror and said focal point of said second parabolic mirror.

5. The projection-type display device of claim 1, in which said first concave mirror is a parabolic mirror, and said second concave mirror is a spherical mirror.

6. The projection-type display device of claim 5, in which an optical axis of said parabolic mirror and an optical axis of said spherical mirror are in alignment, and a focal point of said parabolic mirror and a center of curvature of said spherical mirror are collocated.

7. The projection-type display device of claim 6, in which said lamp has a center of luminescence which is located at said focal point of said parabolic mirror and said center of curvature of said spherical mirror.

8. The projection-type display device of claim 5, in which said parabolic mirror, when viewed from a direction opposite said lamp, has a rectangular configuration substantially similar to said rectangular display area of said liquid crystal light valve means.

9. The protection-type display device of claim 8, in which an optical axis of said parabolic mirror and an optical axis of said spherical mirror are in alignment, and a focal point of said parabolic mirror and a center of curvature of said spherical mirror are collocated.

10. The projection-type display device of claim 9, in which said lamp has a center of luminescence which is located at said focal point of said parabolic mirror and said center of curvature of said spherical mirror.

11. The projection-type display device of claim 1, in which said aperture window of said concave mirror is a hole.

12. The projection-type display device of claim 1, in which said aperture window of said concave mirror is made of a transparent material.

13. The projection-type display device pf claim 1, in which said second concave mirror is made of a transparent material and a reflecting film disposed on said transparent material.

14. The projection-type display device of claim 12, further comprising;

a non-reflective coating to visible light disposed on a surface of said transparent material of said aperture window.

15. The projection-type display device of claim 12, further comprising a coating reflecting ultraviolet rays and a coating reflecting infrared rays, both of them disposed on a surface of said transparent material of said aperture window.

16. The protection-type display device of claim 1, in which a peripheral edge of said first concave mirror and a peripheral edge of said second concave mirror are attached so as to form a sealed space between said first and second concave mirrors.

17. The projection-type display device of claim 4, wherein a depth of said first parabolic mirror is equal to a focal length of said second parabolic mirror and a depth of said second parabolic mirror is equal to a focal length of said first parabolic mirror.

18. The projection-type display device of claim 7, wherein a depth of said spherical mirror is double a focal length of said parabolic mirror.

19. The projection-type display device of claim 10, wherein a radius of curvature of said spherical mirror is equal to a depth of said parabolic mirror plus a focal length of said parabolic mirror and the focal length of said parabolic mirror is less than a shorter side length of said rectangular aperture window divided by four.

20. A projection-type display device comprising:

light source means for emitting a parallel luminous flux in a predetermined direction;

dichroic mirror means for separating the parallel luminous flux into red, blue and green luminous fluxes;

liquid crystal light valve means disposed in a path of the red, blue, and green luminous fluxes having a rectangular display area, for outputting a red, blue, and green rectangular two-dimensional image from rectangular display areas;

a projection lens for magnifying the red, blue and green two-dimensional images from said liquid crystal light valve means and projecting the magnified image on a screen;

said light source means including,

a first concave mirror, a reflecting surface of which is oriented in the direction of emission of the parallel luminous flux,

a lamp placed in front of said first concave mirror, and

a second concave mirror, a reflecting surface of which is oriented toward said lamp and the reflecting surface of said first concave mirror, said second concave mirror having an aperture window substantially equivalent in size to the rectangular display areas of said liquid crystal light valve means, for allowing a rectangular two-dimensional beam of the parallel luminous flux, which is parallel to an optical axis of said first and second concave mirrors, to impinge on said dichroic mirror means and said liquid crystal light value means in order to increase an amount of the parallel luminous flux which impinges on said liquid crystal light valve means, thereby increasing the projected image brightness.

21. The projection-type display device of claim 20, in which said first concave mirror is a first parabolic mirror, and said second concave mirror is a second parabolic mirror.

22. The projection-type display device of claim 21, in which an optical axis of said first parabolic mirror and an optical axis of said second parabolic mirror are in alignment, and a focal point of said first parabolic mirror and a focal point of said second parabolic mirror are collocated.

23. The projection-type display device of claim 22, in which said lamp has a center of luminescence which is located at said focal point of said first parabolic mirror and said focal point of said second parabolic mirror.

24. The projection-type display device of claim 20, in which said first concave mirror is a parabolic mirror and said second concave mirror is a spherical mirror.

25. The projection-type display device of claim 24, in which an optical axis of said parabolic mirror and an optical axis of said spherical mirror are in alignment, and a focal point of said parabolic mirror and a center of curvature of said spherical mirror are collocated.

26. The projection-type display device of claim 25, in which said lamp has a center of luminescence which is located at said focal point of said parabolic mirror and said center of curvature of said spherical mirror.

27. The projection-type display device of claim 24, in which said parabolic mirror, when viewed from a direction opposite said lamp, has a rectangular configuration substantially similar to said rectangular display areas of said liquid crystal light valve means.

28. The projection-type display device of claim 27, in which an optical axis of said parabolic mirror and optical axis of said spherical mirror are in alignment, and a focal point of said parabolic mirror and a center of curvature of said spherical mirror are collocated.

29. The projection-type display device of claim 28, in which said lamp has a center of luminescence which is located at said focal point of said parabolic mirror and said center of curvature of said spherical mirror.

30. The projection-type display device of claim 20, in which said aperture window of said concave mirror is a hole.

31. The projection-type display device of claim 20, in which said aperture window of said concave mirror is made of a transparent material.

32. The projection-type display device of claim 20, in which said second concave mirror is made of a transparent material and a reflecting film disposed on said transparent material.

33. The projection-type display device of claim 31, further comprising:

a non-reflective coating to visible light disposed on a surface of said transparent material of said aperture window.

34. The projection-type display device of claim 31, further comprising a coating reflecting ultraviolet rays and a coating reflecting infrared rays, both of them disposed on a surface of said transparent material of said aperture window.

35. The projection-type display device of claim 20, in which a peripheral edge of said first concave mirror and a peripheral edge of said second concave mirror are attached so as to form a sealed space between said first and second concave mirrors.

36. The projection-type display device of claim 23, wherein a depth of said first parabolic mirror is equal to a focal length of said second parabolic mirror and a depth of said parabolic mirror equal to a focal length of said first parabolic mirror.

37. The projection-type display device of claim 26, wherein a depth of said spherical mirror is double a focal length of said parabolic mirror.

38. The projection-type display device of claim 29, wherein a radius of curvature of said spherical mirror is equal to a depth of said parabolic mirror plus a focal length of said parabolic mirror and the focal length of said parabolic mirror is less than a shorter side length of said rectangular aperture window divided by four.

39. A projection-type display device, comprising:

light source means for emitting a parallel luminious flux in a predetermined direction;

polarized beam splitter means for separating the parallel luminous flux into first P-polarized light and S-polarized light by reflecting only the S-polarized light;

liquid crystal light valve means disposed in a path of the S-polarized light, having a rectangular display area, a glass substrate and a plurality of pixels formed in a matrix, for converting the S-polarized light into second P-polarized light when a voltage in excess of a threshold is not applied and for transmitting the second P-polarized light through said polarized beam splitter means; and

projection means for projecting the second P-polarized light, which has been transmitted through said polarized beam splitter on a screen;

said light source means including,

a first concave mirror, a reflecting surface of which is oriented in the direction of emission of the parallel luminous flux,

a lamp placed in front of said concave mirror, and

a second concave mirror, a reflecting surface of which is oriented toward said lamp and the reflecting surface of said first concave mirror, said second concave mirror having an aperture window substantially equivalent in size to the rectangular display area of said liquid crystal light valve means, for allowing a rectangular two-dimensional beam of the parallel luminous flux, which is parallel to an optical axis of said first and second concave mirrors, to impinge on said liquid crystal light valve means in order to increase an amount of the parallel luminous flux which impinges on said liquid crystal light valve means, thereby increasing the projected image brightness.

40. The projection-type display device of claim 39, in which said first concave mirror is a first parabolic mirror, and said second concave mirror is a second parabolic mirror.

41. The projection-type display device of claim 40, in which an optical axis of said first parabolic mirror and an optical axis of said second parabolic mirror are in alignment, and a focal point of said first parabolic mirror and a focal point of said second parabolic mirror are collocated.

42. The projection-type display device of claim 41, in which said lamp has a center of luminescence which is located at said focal point of said first parabolic mirror and said focal point of said second parabolic mirror.

43. The projection-type display device of claim 39, in which said first concave mirror is a parabolic mirror, and said second concave mirror is a spherical mirror.

44. The projection-type display device of claim 43, in which an optical axis of said parabolic mirror and an optical axis of said spherical mirror are in alignment, and a focal point of said parabolic mirror and a center of curvature of said spherical mirror are collocated.

45. The projection-type display device of claim 44, in which said lamp has a center of luminescence which is located at said focal point of said parabolic mirror and said center of curvature of said spherical mirror.

46. The projection-type display device of claim 43, in which said parabolic mirror, when viewed from a direction opposite said lamp, has a rectangular configuration substantially similar to said rectangular display area of said liquid crystal light valve means.

47. The projection-type display device of claim 46, in which an optical axis of said parabolic mirror and an optical axis of said spherical mirror are in alignment, and a focal point of said parabolic mirror and a center of curvature of said spherical mirror are collocated.

48. The projection-type device of claim 47, in which said lamp has a center of luminescence which is located at said focal point of said parabolic mirror and said center of curvature of said spherical mirror.

49. The projection-type display device of claim 39, in which said aperture window of said concave mirror is a hole.

50. The projection-type display device of claim 39, in which said aperture window of said concave mirror is made of a transparent material.

51. The projection-type display device of claim 39, in which said second concave mirror is made of a transparent material and a reflecting film disposed on said transparent material.

52. The projection-type display device of claim 50, further comprising:

a non-reflective coating to visible light disposed on a surface of said transparent material of said aperture window.

53. The projection-type display device of claim 50, further comprising a coating reflecting ultraviolet rays and a coating reflecting infrared rays, both of them disposed on a surface of said transparent material of said aperture window.

54. The projection-type display device of claim 39, in which a peripheral edge of said first concave mirror and a peripheral edge of said second concave mirror are attached so as to form a sealed space between said first and second concave mirrors.

55. The protection-type display device of claim 42, wherein a depth of said first parabolic mirror is equal to a focal length of said second parabolic mirror and a depth of said second parabolic mirror is equal to a focal length of said first parabolic mirror.

56. The projection-type display device of claim 45, wherein a depth of said spherical mirror is double a focal length of said parabolic mirror.

57. The projection-type display device of claim 45, wherein a radius of curvature of said spherical mirror is equal to a depth of said parabolic mirror plus a focal length of said parabolic mirror and the focal length of said parabolic mirror is less than a shorter side length of said rectangular aperture window divided by four.