Low profile liquid crystal projector and method of using same

• US 5,321,450 A
• Filed: 05/11/1993
• Issued: 06/14/1994
• Est. Priority Date: 05/11/1993
• Status: Expired due to Term

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Proxima Corporation (Ask ASA)
• Inventors: Shapiro, Leonid, Kappel, David W.
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): Dowling, William C.
• Application Number:
  US08/059,550
• Time in Patent Office: 399 Days
• Field of Search: 353/119, 353/70, 353/69, 353/99, 353/98, 353/DIG. 3, 359/40, 359/48, 359/49
• US Class Current: 353/119
• CPC Class Codes: G03B 21/28 Reflectors in projection beam in illumination beam G03B21/2066
• CPC Class Codes: G09G 2340/04 Changes in size, position or resolution of an image
• CPC Class Codes: G09G 2340/0414 Vertical resolution change
• CPC Class Codes: G09G 2340/0421 Horizontal resolution change
• CPC Class Codes: G09G 2340/0471 Vertical positioning
• CPC Class Codes: G09G 2340/0478 Horizontal positioning
• CPC Class Codes: G09G 2340/0485 Centering horizontally or vertically
• CPC Class Codes: H04N 5/7441 the modulator being an array of liquid crystal cells
• CPC Class Codes: H04N 9/3141 Constructional details thereof details not peculiar to the presence of an electronic spatial light modulator G03B21/14

Abstract

An liquid crystal unit, and a novel method of us to project a liquid crystal image with substantially no keystoning effects. A low profile projector optics arrangement directs high intensity light within the housing along an irregularly shaped light path extending angularly through an angularly inclined liquid crystal display panel offset by an angle λ relative to the normal axis plane of the display panel to help reduce image keystoning. An output mirror mounted above the housing is inclined angularly opposite to the liquid crystal display panel and cooperates with a lens set for projecting reflectively a liquid crystal image, formed by the display panel, onto a remote surface. The output mirror is mounted to reflect the liquid crystal image upwardly at an angle θ to the normal axis plane of the remote viewing surface, where the angle λ and the angle θ are substantially equal to help reduce image keystoning. The inventive method of using the liquid crystal projector includes, passing light along an irregularly shaped light path extending angularly through the liquid crystal panel offset by an angle λ relative to the normal axis plane of the display panel and projecting reflectively upwardly at an angle θ relative to the normal axis plane of the remote viewing surface, where the angle λ and the angle θ are substantially equal.

Claims

1. A projector, comprising:

low profile elongated housing means having a hollow interior;

high intensity light means mounted within a rear portion of said low profile housing means for illuminating a light path;

liquid crystal display means disposed within said hollow interior disposed forwardly of said light means along said path for forming a liquid crystal image;

optic means disposed within said hollow interior for defining the light path extending angularly through said liquid crystal display means offset by an angle λ

relative to the normal axis plane of said liquid crystal display means for helping to reduce image keystoning;

top output mirror means disposed above said low profile housing means for projecting reflectively said liquid crystal image onto a remote viewing surface without introducing any substantial image keystoning;

means for mounting said top output mirror means inclined angularly opposite of said liquid crystal display means for reflecting said liquid upwardly at angle θ

relative to the normal axis plane of said remote viewing surface; and

said angle λ and

said angle θ

being substantially equal, whereby the liquid crystal image formed by said liquid crystal display means is illuminated by the high intensity light means, reflected along a portion of said irregularly shaped light path and projected reflectively onto said remote viewing surface without any substantial image keystoning.

2. A projector to claim 1, wherein said optic means includes:

bottom output mirror means for reflecting an incidence liquid crystal image angularly upwardly at about an angle of η

degrees relative to the normal axis plane of said top output mirror means;

adjustable lens means disposed between said top and bottom output mirror means for causing the liquid crystal image projected reflectively by said top output mirror means to be focused onto said remote viewing surface;

top mirror means for reflecting said incidence liquid crystal image angularly downwardly at about an angle of δ

degrees relative to the normal axis plane of said bottom output mirror means; and

bottom mirror means disposed below said liquid crystal display means for reflecting incidence light having a central light ray angularly upwardly at about an angle of δ

degrees relative to the normal axis plane of said top mirror means.

3. A projector according to claim 2, wherein said bottom mirror means includes a mirror having a general trapezoidal shape for causing the light reflected from said bottom mirror means to be angularly offset from the normal axis plane of said liquid crystal display means by about λ

degrees, whereby keystone correction is provided on the input side of said liquid crystal display means.

4. A projector according to claim 3, wherein the angle λ

is between about 1 degrees and about 6.5 degrees.

5. A projector according to claim 4, wherein a more preferred angle λ

is between about 2 degrees and about 5 degrees.

6. A projector according to claim 5, wherein the most preferred angle λ

is about 4 degrees.

7. A projector according to claim 2, wherein the angle φ

is about 49 degrees.

8. A projector according to claim 2, wherein the angle δ

is about 74.9 degrees.

9. A projector according to claim 2, wherein the angle γ

is about 43.0 degrees.

10. A projector according to claim 2, wherein said top output mirror reflects an incidence central light ray toward the normal axis plane of said remote surface, said incidence central light ray being offset from the normal axis plane of said remote surface by an angle of about θ

degrees.

11. A projector according to claim 10, wherein θ

is between about 1.5 degrees and 6.5 degrees.

12. A projector according to claim 11, wherein a more preferred angle θ

is between about 2.5 degrees and 5.5 degrees.

13. A projector according to claim 12, wherein the most preferred angle θ

is about 4.5 degrees.

14. A projector according to claim 1, wherein said high intensity lamp means includes a cold mirror for helping to reduce ultraviolet radiation from being reflected into said hollow interior.

15. A projector according to claim 14, wherein said cold mirror reflects incidence light angularly downwardly at about an angle of β

degrees to the normal axis plane of said bottom mirror means.

16. A projector according to claim 15, wherein said angle β

is about 42.25 degrees.

17. A projector according to claim 1, wherein said low profile housing means includes transparent window means disposed within said irregularly shaped light path for enabling said liquid crystal image to be focused reflectively onto said top output mirror means.

18. A method of projecting a liquid crystal image onto a remote viewing surface, comprising:

energizing liquid crystal display means to form a liquid crystal image, said liquid crystal display means being inclined angularly rearwardly within a low profile housing;

generating high intensity light;

directing the high intensity light along an irregularly shaped light path, said irregularly shaped light path extending angularly through said liquid crystal display means offset by an angle λ

relative to the normal axis plane of said liquid crystal display means for helping to reduce image keystoning;

illuminating said liquid crystal image; and

projecting reflectively the illuminated liquid crystal image onto a remote viewing surface;

said liquid crystal image being projected reflectively upwardly at an angle θ

relative to the normal axis plane of said remote viewing surface; and

said angle λ and

said angle θ

being substantially equal, whereby the liquid crystal image formed by said liquid crystal display means is illuminated by the high intensity light means, reflected along a portion of said irregularly shaped light path and projected reflectively onto said remote viewing surface without any substantial image keystoning.

19. A method according to claim 18, wherein directing includes:

directing the high intensity light along a portion of said path downwardly forwardly incident onto mirror means.

20. A method according to claim 19, wherein said directing includes:

reflecting the high intensity light from said mirror means upwardly forwardly toward said liquid crystal display means along another portion of said path.

21. A method according to claim 20, wherein directing the high intensity light downwardly forwardly toward said mirror means includes:

directing a central light ray of the incident high intensity light forwardly at about an angle β

relative to the normal axis plane of said mirror means.

22. A method according to claim 21, wherein said angle β

is between about 31.3 degrees and about 52.3 degrees.

23. A method according to claim 22, wherein a more preferred angle β

is between about 37.3 degrees and about 43.3 degrees.

24. A method according to claim 23, wherein the most preferred angle β

is about 42.3 degrees.

25. A method according to claim 18 wherein said step of projecting includes:

using a projection lens.

26. A method according to claim 18, wherein said directing includes directing a central light ray of reflected light upwardly and forwardly at about said angle λ

relative to the normal axis plane of said display means.

27. A method according to claim 26, wherein said angle λ

is between about 1.0 degrees and about 6.5 degrees.

28. A method according to claim 27, wherein a more preferred angle λ

is between about 2.0 degrees and about 5.0 degrees.

29. A method according to claim 28, wherein a most prefered angle λ

is about 4.0 degrees.

30. A method according to claim 18, wherein said angle θ

is between about 1.0 degrees and about 6.5 degrees.

31. A method according to claim 30, wherein a more preferred angle θ

is between about 2.0 degrees and about 5.0 degrees.

32. A method according to claim 31, wherein a most preferred angle θ

is about 4.0 degrees.

33. A method according to claim 20, wherein said directing further includes:

directing the high intensity light along another portion of said irregular path from said display means forwardly to said projection lens.

34. A projector, comprising:

low profile housing means having an upper wall member, a lower wall member, a front wall member, a rear wall member, and a pair of side wall members for defining a hollow interior;

top output mirror means disposed above said

image housing for projecting reflectively a liquid crystal onto a remote viewing surface without introducing any substantial keystoning;

window means disposed within said upper wall member for defining an image passageway to enable said liquid crystal image to be reflected by said top output mirror means;

high intensity lamp means mounted within said hollow interior for producing high intensity light;

optic means disposed within said hollow interior for causing the high intensity light to be directed along an optical path within the hollow interior of said low profile housing and for enabling said liquid crystal image to be projected through said transparent window means into said top output mirror means;

liquid crystal display means disposed within said hollow interior for producing said liquid crystal image;

means for mounting said liquid crystal display means inclined angularly rearwardly between said upper wall member and said lower wall member and within said optical path;

whereby the liquid crystal image produced by said liquid crystal display means is illuminated by the high intensity light, transmitted along a portion of said optical path via said optics means, and projected reflectively onto said remote viewing surface by said top output mirror means.

35. A projector, comprising:

low profile elongated housing means having an output window and a hollow interior with a given height;

liquid crystal display means angularly disposed within a light path in said hollow interior for forming a liquid crystal image, said liquid crystal display means having another given height substantially greater than the first-mentioned given height;

optic means disposed within said hollow interior for directing and reflecting light along said light path through said liquid crystal display means and said output window; and

mirror means mounted on the exterior of said housing means adjacent to said output window for reflecting said liquid crystal image towards a remote viewing surface.

36. A projector according to claim 35, wherein said liquid crystal display means is a single liquid crystal display panel assembly.

37. A projector according to claim 36, wherein said mirror means is mounted ajustably relative to said output window for helping to position the reflected liquid crystal image on said remote viewing surface.

38. A projector according to claim 37, wherein said mirror means is mounted pivotally for reflecting the liquid crystal display image upwardly from a horizontal plane toward said remote viewing surface.

39. A projector according to claim 38, wherein said optic means includes lower output mirror means disposed within said light path for directing said liquid crystal image substantially vertically upwardly through said output window;

and

lens means disposed in said light path between said output mirror means and said output window for helping to focus the liquid crystal image for image projection purposes.

40. A projector according to claim 39, wherein said mirror means is adjustable between a fully opened position and a fully closed position.

41. A projector according to claim 40, wherein said mirror means is disposed angularly inclined upwardly relative to the horizontal plane when disposed in said fully opened position.

42. A projector according to claim 41, wherein said mirror means is disposed in a substantially perpendicular position relative to the horizontal plane when disposed in said fully closed position.