Efficient optical system for a high resolution projection display employing reflection light valves

• US 5,786,934 A
• Filed: 08/25/1997
• Issued: 07/28/1998
• Est. Priority Date: 03/23/1995
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Doany, Fuad Elias, Singh, Rama Nand, Rosenbluth, Alan Edward, Chiu, George Liang-Tai, Cipolla, Thomas Mario, Dove, Derek Brian, Wilczynski, Janusz Stanislaw
• Primary Examiner(s): SHAFER, RICKY D
• Application Number:
  US08/917,400
• Time in Patent Office: 337 Days
• Field of Search: 359/40, 359/41, 359/634, 359/638, 359/487, 359/490, 359/494, 359/495, 359/496, 359/497, 353/30, 353/31, 353/32, 353/33, 353/34, 353/81, 349/62, 348/750, 348/751, 348/752, 348/756, 348/757, 348/761, 348/762, 348/766, 348/779, 348/780
• US Class Current: 359/487.04
• 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

Abstract

An optical system is described consisting of reflection birefringent light valves, polarizing beam splitter, color image combining prisms, illumination system, projection lens, filters for color and contrast control, and screen placed in a configuration offering advantages for a high resolution color display. In particular, the present invention includes a color splitting prism assembly having a plurality of output faces through which a separate color component is directed to be reflected by a respective light valve. Color absorbing filters are disposed at each of the output faces to absorb the color components not corresponding to the color directed through each output face.

Claims

1. An apparatus for projecting an image onto a screen comprising:

a light source for providing light;

a polarizing beam splitting means for splitting the light into first and second polarized lights having first and second polarizations respectively;

a color splitting prism assembly having a plurality of output faces, said color splitting prism assembly splitting the first polarized light into a plurality of color components and directing each color component through a corresponding one of said output faces;

color absorbing means at each of said output faces for absorbing beach of said plurality of color components not corresponding to the color components of light directed through each of said output faces;

a spatial light modulator at each of said output faces for reflecting said color components passed through each of said output faces as a reflected color component of the image passed back into said prism assembly;

said color splitting prism assembly recombining the reflected color components of the image to form a combined reflected image, and said polarizing beam splitting means splitting the combined reflected image into first and second polarized images and directing said second polarized image to a projection lens, said projection lens projecting said second polarized image as the image onto the screen.

2. The apparatus of claim 1 further including:

means for directing the light from said source into said polarizing beam splitting means.

3. The apparatus of claim 2 wherein said means for directing the light from said light source to said polarizing beam splitting means includes an illumination assembly having means for filtering out ultraviolet and infrared light and means for providing uniform light intensity to the light directed to the polarizing beam splitting means.

4. The apparatus according to claim 2 further including pre-polarizing filter means disposed within a light path between the light source and said polarizing beam splitting means for absorbing one of said first or second polarizations.

5. The apparatus according to claim 2 further including a post-polarizing filter means disposed within a light path between said polarizing beam splitting means and said projection lens for absorbing one of said first or second polarizations.

6. The apparatus according to claim 2 further including a post-polarizing filter means disposed within a light path between said polarizing beam splitting means and said projection lens for absorbing one of said first or second polarizations.

7. The apparatus according to claim 6 further including a color absorbing film disposed between said light source and said polarizing beam splitting means.

8. The apparatus of claim 1 wherein said spatial light modulator includes a liquid crystal light valve assembly.

9. The apparatus of claim 1 wherein said prism assembly is comprised of three solid glass prisms forming two color separating surfaces located internally of said assembly.

10. The apparatus of claim 1 wherein said polarizing beam splitting means is comprised of two solid glass prisms forming a polarization separating surface internally of said beam splitting means.

11. The apparatus according to claim 1 wherein said color absorbing means includes means for absorbing band edges of each of said plurality of color components.

12. The apparatus according to claim 1 further including a color absorbing film disposed between said light source and said polarizing beam splitting means.

13. The apparatus of claim 1 further comprising an illumination assembly having a lens and means for filtering out ultraviolet and infrared light, said means for filtering out ultraviolet and infrared light being located between said lens and said light source.