Optical engine for front or rear screen SLM display systems

• US 6,619,804 B2
• Filed: 12/31/2001
• Issued: 09/16/2003
• Est. Priority Date: 12/29/2000
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Anderson, Douglas W., Davis, Michael T.
• Primary Examiner(s): Adams, Russell
• Assistant Examiner(s): NGUYEN, MICHELLE P
• Application Number:
  US10/036,588
• Publication Number:
  US 20020085181A1
• Time in Patent Office: 624 Days
• Field of Search: 353/69, 353/70, 353/74-77, 353/79, 353/84, 353/97, 353/98, 349/5, 349/7, 348/742, 348/743, 348/771
• US Class Current: 353/98
• CPC Class Codes: G02B 13/22 Telecentric objectives or lens systems
• CPC Class Codes: G02B 17/08 Catadioptric systems used in non-imaging applications G02B19/00
• 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: H04N 9/3114 by using a sequential colour filter producing one colour at a time

Abstract

An optical engine (15) for an SLM-type display system, which may be either a front or rear projection system (10, 20). The optical engine (15) provides for a high contrast, telecentric illumination angle to the SLM (33) without compromising brightness by vignetting due to offset in the pupil. The resulting offset pupil is converted to a telecentric, on-axis image by a relay path (34) between the SLM (33) and the projection lens (37). The relay path (34) places the image at an intermediate image plane accessible by a the projection lens (37), which permits the projection lens (37) to be telecentric without an offset pupil.

Claims

1. An image path for use in an optical engine of an SLM-based display system, comprising:

relay optics for receiving light reflected from the SLM, the relay path having;

a first set of lenses that receives the light from the SLM, a mirror that receives the light from the first set of lenses, and a second set of lenses that receives the light reflected from the mirror;

wherein the first set of lenses is operable to receive the light from the SLM as an offset pupil;

wherein the second set of lenses is operable to place the image at an intermediate image plane; and

a projection lens operable to receive the image from the intermediate image plane and to project and/or magnify the image to a display image plane.

2. The image path of claim 1, wherein the SLM is a DMD type SLM and wherein the first set of lenses directs light from flat pixel elements away from the mirror.

3. The image path of claim 1, wherein the SLM is a DMD and light reflected from off pixel elements is directed away from the mirror.

4. The image path of claim 1, further comprising a mask aperture at the intermediate image plane.

5. The image path of claim 1, wherein the projection lens is telecentric relative to the image from the intermediate image plane.

6. The image path of claim 1, wherein the intermediate image plane is on-axis with no offset, and wherein the relay path includes an offset pupil.

7. An optical engine for use in an SLM-based display system, comprising:

a light source;

an SLM for receiving light from the light source and for reflecting an image;

relay optics for receiving the image reflected from the SLM, the relay path having;

a first set of lenses that receives the image from the SLM, a mirror that receives the image from the first set of lenses, and a second set of lenses that receives the image reflected from the mirror;

wherein the first set of lenses is operable to receive the image from the SLM as an offset pupil;

wherein the second set of lenses is operable to place the image at an intermediate image plane; and

a projection lens operable to receive the image from the intermediate image plane and to project the image to a display image plane.

8. The optical engine of claim 7, wherein the SLM is a digital micromirror device.

9. The optical engine of claim 7, wherein the SLM is a DMD type SLM and wherein light from flat pixel elements is directed away from the mirror.

10. The optical engine of claim 7, wherein the SLM is a DMD and light reflected from off pixel elements is directed away from the mirror.

11. The optical engine of claim 7, further comprising a mask aperture at the intermediate image plane.

12. The optical engine of claim 7, wherein the projection lens is telecentric relative to the image at the intermediate image plane.

13. The optical engine of claim 7, further comprising a color wheel for filtering light from the light source.

14. A method of generating images for an SLM-type projection display system, comprising the steps of:

illuminating the SLM with a light source;

generating an image, using the SLM, such that an image is reflected from the SLM;

receiving the image reflected from the SLM into a relay path having the following elements;

a first set of lenses that receives the image from the SLM, a mirror that receives the image from the first set of lenses, and a second set of lenses that receives the image reflected from the mirror;

such that the first set of lenses receives the image from the SLM as an offset pupil;

and such that the second set of lenses places the image at an intermediate image plane;

placing a projection lens in front of or inclusive to the intermediate image plane; and

projecting the image to a screen.

15. The method of claim 14, wherein the placing step is performed by placing the projection lens telecentric to the image.

16. The method of claim 15, wherein the telecentric projection lens has any amount of offset to the relay axis, including zero.

17. The method of claim 14, wherein the illuminating step is performed with an illumination angle that results in the offset pupil.

18. The method of claim 14, further comprising the step of masking the border of the image at the intermediate image plane.

19. The method of claim 14, wherein the SLM is a digital micromirror device.