Spatial light modulator system

• US 5,704,701 A
• Filed: 09/27/1994
• Issued: 01/06/1998
• Est. Priority Date: 03/05/1992
• Status: Expired due to Term

• Current Assignee: Digital Projection Limited
• Original Assignee: Rank Brimar Limited
• Inventors: Kavanagh, Martin, Fielding, Raymond Gordon
• Primary Examiner(s): DOWLING, WILLIAM C
• Application Number:
  US08/302,704
• Time in Patent Office: 1,197 Days
• Field of Search: 353/31, 353/33, 353/37, 353/98, 353/122, 359/212, 359/223, 359/846, 359/847, 359/849, 348/771, 348/768
• US Class Current: 353/33
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G02B 27/18 for optical projection, e.g. combination of mirror and condenser and objective photographic, cine and overhead projectors G03B21/00; photographic projection printing G03B27/32; photolithographic projectors G03F7/20; projection television H04N5/74; colour projection television H04N9/31
• CPC Class Codes: G09F 9/372 the positions of the elements being controlled by the application of an electric field
• CPC Class Codes: H04N 5/74 Projection arrangements for image reproduction, e.g. using eidophor
• CPC Class Codes: H04N 5/7458 the modulator being an array of deformable mirrors, e.g. digital micromirror device [DMD]
• 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

A display apparatus for use in a projection system includes a light source, a beam splitter for splitting light from the source into different color component beams and a deformable mirror device spatial light modulators for each different color beam. The light paths to the beam splitter and modulators are provided within a single prism assembly on which the modulators are mounted.

Claims

1. A display apparatus for use in a projection system comprising a light source, means for splitting light from the source into different color component beams, and a plurality of spatial light modulators each comprising an array of tiltable mirror devices, characterized in that the light paths to said splitting means and modulators are provided within a single prism assembly to which said modulators are mounted.

2. An apparatus according to claim 1, in which the surface of the prism which receives light from the source is convex so as to converge the light beam onto each modulator device.

3. An apparatus according to claim 1 including light absorbing means positioned to absorb light directed by any of the tiltable mirror devices of the modulators when said tiltable mirror device is in an "off" position.

4. Apparatus according to claim 3, in which the light absorbing means includes means for dissipating heat corresponding to the light absorbed.

5. Apparatus according to claim 3 or claim 4, in which the light absorbing means comprises a layer mounted to a face of the prism and having a refractive index corresponding to that of the prism.

6. An apparatus according to claim 5, in which the layer comprises a black, glass layer.

7. An apparatus according to claim 1 including means for filtering the beam from the light source to reject unwanted spectral components prior to entering the modulators device.

8. An apparatus according to claim 7, in which the filter means are such as to reject infrared components.

9. An apparatus according to claim 7 or 8, in which the filter means are arranged to reject ultraviolet components.

10. An apparatus according to claim 7 wherein the filter means are arranged on a convex surface so as to divergingly reflect said unwanted components.

11. An apparatus according to claim 7 wherein the filter means are arranged so as not to refocus rejected radiation onto the light source.

12. An apparatus according to claim 7 wherein the filter means are arranged on a surface of the prism assembly.

13. An apparatus according to claim 1 including means positioned between the light source and the spatial light modulator, for absorbing portions of the beam which would not illuminate the spatial light modulator.

14. An apparatus according to claim 1 including an optical component comprising a surface defining an array of curved reflectors bounded by polygonal edges, the component being arranged to direct light onto the prism assembly.

15. An apparatus according to claim 14, in which the reflectors are concave.

16. An apparatus according to claim 14 or claim 15, in which the array is curved.

17. An apparatus according to claim 14 further comprising optical means for superimposing the rays from each polygonal reflector of said array onto the prism assembly.

18. An apparatus according to claim 17, further comprising an array of polygonal lenses aligned with said reflective array.

19. An apparatus according to claim 1 including a component for producing a polygonal optical beam comprising an array of polygonal optical lenses or reflectors each said lens or reflector being combined with a prism surface, said prism surfaces being progressively tilted, relative to a point on said array, so as to superimpose the polygonal beams from each said lens or reflector into a single uniform polygonal spot at a predetermined distance from the array.

20. An apparatus according to claim 1 including a spatial light modulator light output system, and an output lens arrangement and a mirror arrangement effective to separate the incident and reflected light to and from said reflective spatial light modulator to reduce the physical distance to the lens, permitting a wide aperture lens.

21. An apparatus according to claim 14, in which the optical component is integral with the prism assembly.

22. A display device comprising a light source, a spatial light modulator for modulating the beam therefrom, and means for projecting the modulated beam to a display, and a prism assembly including a number of discrete components cemented together wherein the component closest to the light source includes means for filtering the beam from the light source to reject unwanted spectral components prior to the spatial light modulator device.

25. A projection system comprising a display device according to claim 23 or 22 and a display.

23. A display device which comprises an active matrix spatial light modulator device, including a prism assembly in the light path to the spatial light modulator device, the light modulator device being of the type in which an element of said matrix directs light in a first direction when the element is in a first state and a second direction when the element is in a second state, characterized by light absorbing means positioned to absorb light directed in said second direction of a matching refractive index to that of said prism.

24. An apparatus according to claim 23, wherein the layer of matching refractive index is a black glass layer.