Full-color projector system with a tricolor-separating prism

• US 4,687,301 A
• Filed: 07/12/1985
• Issued: 08/18/1987
• Est. Priority Date: 07/12/1985
• Status: Expired due to Term

• Current Assignee: Victor Company of Japan Limited (JVC Kenwood Corporation)
• Original Assignee: Hughes Aircraft Company (Rtx Corporation)
• Inventors: Ledebuhr, Arno G.
• Primary Examiner(s): ARNOLD, BRUCE
• Application Number:
  US06/754,802
• Time in Patent Office: 767 Days
• Field of Search: 350/337, 350/331 R, 350/401-403, 350/408, 350/345, 350/394, 350/342, 353/31, 353/34, 353/37, 358/60, 358/61
• US Class Current: 359/634
• CPC Class Codes: G02B 27/142 Coating structures, e.g. thin films multilayers
• CPC Class Codes: G02B 27/145 having sequential partially reflecting surfaces
• 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 liquid crystal light valve projector is disclosed which includes a first color separator responsive to unmodulated polarized light for reflecting light of a first primary color, for transmitting the remaining portion of the incident unmodulated polarized light, and for internally reflecting incident light; a transparent plate window for transmitting incident unmodulated polarized light to the first color separator and for internally reflecting the light of the first primary color reflected by the first color separator; a second color separator responsive to the light transmitted by the first color separator for reflecting light of a second primary color and for transmitting the remaining portion of the incident light which includes a third primary color, whereby the second color separator reflects the light of the second primary color to the first color separator which internally reflects such second primary color light; and light modulators respectively responsive to the light of the first, second, and third primary colors.

Claims

1. A projector comprising:

first color separating means responsive to unmodulated polarized light for reflecting light of a first primary color and for transmitting the remaining portions of the incident unmodulated polarized light, said first color separating means further for internally reflecting incident light;

optical means for transmitting incident unmodulated polarized light to said first color separating means, and for internally reflecting said light of said first primary color as first primary color incident light;

second color separating means responsive to the light transmitted by said first color separating means for reflecting light of a second primary as second primary color incident light and for transmitting the remaining portion of the incident light which includes a third primary color incident light, said second color separating means reflecting said light of said second primary color to said first color separating means which internally reflects said second primary color light as second primary color incident light;

index matching optical fluid for optically coupling said first color separating means, said optical means, and said second color separating means; and

modulating means responsive to said first primary color incident light, said second primary color incident light, and said third primary color incident light.

2. The projector of claim 1 wherein said first color separating means comprises a parallel plate assembly having parallel plates separated by a small air gap for minimizing astigmatism.

3. The projector of claim 2 wherein one of said parallel plates includes a dichroic coating on the side adjacent the air gap and which is illuminated by the incident unmodulated polarized light, and wherein the other of said parallel plates includes an anti-reflection coating on the side adjacent the air gap which provides a coating/air boundary for achieving said internal reflection of said second primary color light.

4. The projector of claim 3 wherein said optical means comprises a transparent plate having an air boundary on the side illuminated by the unmodulated polarized light and having a refractive index matched boundary with said index matching optical fluid on the other side.

5. The projector of claim 4 wherein said second color separating means comprises a dichroic color separator.

6. The projector of claim 5 wherein said parallel plate assembly and said dichroic color separator are positioned to provide small angles of incidence to reduce polarization sensitivity.

7. The projector of claim 5 wherein said transparent plate, said parallel plate assembly, and said dichroic color separator are positioned to provide substantially equal optical paths to the respective light of said first primary color, said second primary color, and said third primary color.

8. The projector of claim 5 wherein said first primary color incident light, said second primary color incident light, and said third primary color incident light are respectively incident on coplanar axes.

9. A color separating assembly comprising:

a housing for containing an optical fluid;

first color separating means within said housing responsive to unmodulated polarized light for reflecting light of a first primary color and for transmitting the remaining portions of the incident unmodulated polarized light, said first color separating means further for internally reflecting incident light;

optical means in said housing for providing an air boundary on one side which is illuminated with unmodulated polarized light that is transmitted to said first color separating means, and for internally reflecting said light of said first primary color reflected by said first color separating means;

second color separating means within said housing responsive to the light transmitted by said first color separating means for reflecting light of a second primary color and for transmitting the remaining portion of the incident light which includes light of a third primary color, said second color separating means reflecting said light of said second primary color to said first color separating means which internally reflects said second primary color light; and

index matching optical fluid within said housing for optically coupling said first color separating means, said optical means, and said second color separating means.

10. The color separating assembly of claim 9 wherein said first color separating means comprises a parallel plate assembly having parallel plates separated by a small air gap.

11. The color separating assembly of claim 10 wherein one of said parallel plates includes a dichroic coating on the side adjacent said air gap and which is illuminated by the incident unmodulated polarized light, and wherein the other of said parallel plates includes an anti-reflection coating on the side adjacent said air gap which provides a coating/air boundary for achieving said internal reflection of said second primary color light.

12. The color separating assembly of claim 11 wherein said optical means comprises a transparent plate having an air boundary on the side illuminated by the unmodulated polarized light and having a refractive index matched boundary with said index matching optical fluid on the other side.

13. The color separating assembly of claim 12 wherein said second color separating means comprises a dichroic color separator.

14. The color separating assembly of claim 13 wherein said parallel plate assembly and said dichroic color separator are positioned to provide small angles of incidence to reduce polarization sensitivity.

15. The color separating assembly of claim 13 wherein said transparent plate, said parallel plate assembly, and said dichroic color separator are positioned to provide substantially equal optical paths to the respective light of said first primary color, said second primary color, and said third primary color.

16. The color separating assembly of claim 13 wherein said first primary color light, said second primary color light, and said third primary color light respectively travel along coplanar paths.

17. A light combining assembly for combining respective projection illumination of first, second and third primary colors, comprising:

optical means for internally reflecting the first primary color projection illumination as internally reflected first primary color illumination, and for transmitting other illumination;

first color combining means for reflecting said internally reflected first primary color illumination to said optical means and for internally reflecting the second primary color projection illumination as internally reflected second primary color illumination, said first color combining means further for transmitting other illumination;

second color combining means for reflecting said internally reflected second primary color illumination to said first color combining means and for transmitting the third primary color projection illumination to said first color combining means, whereby said first color combining means transmits said reflected second primary color illumination and said third primary color illumination received from said second color combining means, and whereby said optical means transmits said reflected first primary color illumination received from said first color separating means and also transmits said second and third primary color illumination received from said second color combining means; and

index matching fluid for optically coupling said optical means, said first color combining means, and said second color combining means.

18. The light combining assembly of claim 17 wherein said optical means comprises a transparent plate having a refractive index matched boundary with said index matching optical fluid on one side, and having an air boundary on the other side for achieving said internal reflection of the first primary color incident illumination.

19. The light combining assembly of claim 18 wherein said first color combining means comprises a parallel plate assembly having parallel plates separated by a small air gap.

20. The light combining assembly of claim 19 wherein one of said parallel plates includes a dichroic coating on the side adjacent said air gap and which is illuminated by said first primary color illumination internally reflected by said optical means, and wherein the other of said parallel plates includes an anti-reflection coating on the side adjacent said air gap which provides a coating/air boundary for achieving said internal reflection of said second primary color illumination.

21. The light combining assembly of claim 20 wherein said second color combining means comprises a plate with a dichroic coating.

22. The light combining assembly of claim 21 wherein said parallel plate assembly and said dichroic coated plate are positioned to provide small angles of incidence to reduce polarization sensitivity.

23. The light combining assembly of claim 21 wherein said transparent plate, said parallel plate assembly, and said dichroic coated plate are positioned to provide substantially equal optical paths to the respective illumination of said first primary color, said second primary color, and said third primary color.

24. The light combining assembly of claim 21 wherein said first primary color illumination, said second primary color illumination, and said third primary color illumination respectively travel along coplanar paths.