Speckle-free display system using coherent light

• US 5,313,479 A
• Filed: 07/29/1992
• Issued: 05/17/1994
• Est. Priority Date: 07/29/1992
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Florence, James M.
• Primary Examiner(s): Scott, Jr., Leon
• Application Number:
  US07/921,869
• Time in Patent Office: 657 Days
• Field of Search: 372/26, 372/9, 372/28, 372/99, 372/108
• US Class Current: 372/26
• CPC Class Codes: G02B 27/48 Laser speckle optics
• CPC Class Codes: G02B 5/02 Diffusing elements; Afocal elements
• CPC Class Codes: G02B 5/0236 the diffusion taking place within the volume of the element
• CPC Class Codes: G02B 5/0278 used in transmission
• CPC Class Codes: H04N 9/3129 scanning a light beam on the display screen scanning a light beam on a screen in displays other than projection devices G09G3/02; scanning systems in general G02B26/10; projectors using laser light sources in general H04N9/3161

Abstract

A speckle-free display system using coherent light is disclosed. The light is directed through a spinning diffusing element to illuminate a spatial light modulator. The spinning element is operable to move the interference patterns around the screen at a speed where it is undetectable to the human eye. The diffusing element is more than likely comprised of ground glass.

Claims

1. A speckle-free display system comprising:

a. at least one coherent light source generating at least one coherent light beam;

b. a diffusing element located in a plane intercepts said coherent light beam such that light leaves said diffusing element as a diffused light beam which includes interference patterns;

c. a means for moving said diffusing element in said plane while said diffusing element is intercepting said coherent light beam;

d. a spatial light modulator for receiving said diffused light beam and for generating an image light beam; and

e. a viewing surface located such that said image bearing light beam impinges thereon to produce a visible image, and wherein said movement of said diffusing element causes said speckle interference pattern to move on said viewing surface so that said speckle pattern is substantially and thereby an improved image is provided.

2. The system as claimed in claim 1 wherein said at least one coherent light source further comprises three lasers, one red, one green and one blue.

3. The system as claimed in claim 1 wherein said at least one coherent light source further comprises a tunable laser.

4. The system as claimed in claim 1 wherein said diffusing element has no gain.

5. The system as claimed in claim 1 wherein said diffusing element has a gain.

6. The system as claimed in claim 1 wherein said diffusing element is comprised of ground glass.

7. The system as claimed in claim 1 wherein said means for moving is a motor.

8. The system as claimed in claim 1 wherein said means for moving is a coil.

9. The system as claimed in claim 1 wherein said diffusing element is rotated.

10. The system as claimed in claim 1 wherein said diffusing element is rotated at more than 40 rpm.

11. The system as claimed in claim 1 wherein said diffusing element is vibrated.

12. The method of producing a speckle-free display comprising:

a. providing at least one coherent light beam;

b. providing a diffusing element to intercept said at least one coherent light beam such that light leaves said diffusing element as a widened beam of light, said widened beam of light containing interference patterns;

c. moving said diffusing element while said diffusing element is intercepting said at least one coherent light beam such that said interference patterns move within said widened beam of light;

d. modulating said widened coherent light beam with a spatial light modulator to form an image bearing light beam; and

e. locating a viewing surface such that said image bearing light beam impinges thereon and produces a visible image, and wherein movement of said diffusing element causes speckle interference patterns to move on said viewing surface so that said speckle patterns are substantially invisible.

13. The method of claim 12 wherein said moving step comprises rotating said diffusing element.

14. The method of claim 12 wherein said moving step comprises rotating said diffusing element at a more than 40 rpm.

15. The method of claim 12 wherein said moving step comprises vibrating said diffusing element.