Projection apparatus and method

• US 5,633,755 A
• Filed: 03/05/1996
• Issued: 05/27/1997
• Est. Priority Date: 03/08/1995
• Status: Expired due to Fees

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Okamoto, Kazuya, Manabe, Yuji, Iwasaki, Yutaka, Okubo, Yukiharu
• Primary Examiner(s): Metjahic, Safet
• Assistant Examiner(s): Malley, D. P.
• Application Number:
  US08/611,304
• Time in Patent Office: 448 Days
• Field of Search: 359/443, 359/453, 359/456, 359/460, 359/224, 359/230, 355/67, 348/789, 348/791, 348/744
• US Class Current: 359/443
• CPC Class Codes: H04N 9/3108 by using a single electronic spatial light modulator
• CPC Class Codes: Y10S 359/904 Micromirror

Abstract

A projection apparatus is disclosed that can be used for projection TV and related applications. The apparatus comprises a light source, a projection optical system, a DMD with multiple micromirrors, and a controller for individually controlling the tilt of the micromirrors. The projection optical system comprises, in order from the DMD side, a first lens group, an aperture stop, and a second lens group. An illumination stop is situated between the first and second lens groups. Light from the light source passes through the illumination stop and the first lens group to impinge on the DMD. The controller coordinatedly controls the tilt of the micromirrors in the DMD so that the impinging light is selectively reflected to one or the other of the aperture stop and the illumination stop, thereby eliminating ghost-forming reflections of light not projected onto a screen.

Claims

1. A projection apparatus, comprising:

(a) a light source;

(b) a DMD having micromirrors;

(c) a projection optical system comprising a first lens group, an illumination stop, and an aperture stop; and

(d) a controller;

(e) wherein light from the light source passes through the illumination stop and first lens group to the DMD, and the controller individually controls the orientation of each micromirror of the DMD so that light impinging on the DMD is selectively reflected by any of the micromirrors through the first lens group toward either the aperture stop or the illumination stop.

2. The projection apparatus of claim 1, wherein the projection optical system has a DMD side and is telecentric on the DMD side.

3. The projection apparatus of claim 1, wherein the first lens group has a front side, and the illumination stop is situated at a focal plane of and disposed on the front side of the first lens group.

4. The projection apparatus of claim 3, wherein the aperture stop is situated at the focal plane of and on the front side of the first lens group.

5. The projection apparatus of claim 1, wherein the aperture stop and the illumination stop are situated symmetrically around an optical axis of the projection optical system.

6. The projection apparatus of claim 5, wherein the aperture stop and the illumination stop are defined by a planar stop plate disposed normally to the optical axis.

7. The projection apparatus of claim 1, further comprising a light-converging system operable to converge light from the light source, the light-converging system being arranged so as to form a light-source image at the illumination stop.

8. The projection apparatus of claim 1, wherein the controller is operable to receive video data.

9. The projection apparatus of claim 1, further comprising a second lens group disposed between the aperture stop and a viewing screen, the second lens group being operable for refracting light passing through the aperture stop to the viewing screen.

10. A projection apparatus, comprising:

(a) a light source;

(b) a DMD including micromirrors;

(c) a projection optical system comprising a first lens group and a second lens group, with an aperture stop and an illumination stop disposed between the first and second lens groups, the projection optical system being operable to direct light from the light source through the illumination stop and first lens group to the DMD and from the DMD through the first lens group, aperture stop, and second lens group to a viewing surface; and

(d) a controller;

(e) wherein light from the light source sequentially passes through the illumination stop and the first lens group so as to impinge on the DMD, the controller individually controlling the orientation of each micromirror in the DMD so that the light impinging on the DMD can be selectively reflected by any of the micromirrors toward either the illumination stop to inhibit light scattering or the aperture stop for refraction by the second lens group to a viewing screen.

11. The projection apparatus of claim 10, wherein the controller operates to cause each micromirror to independently tilt to either an ON state or an OFF state, wherein light reflected from OFF-state micromirrors is directed by the first lens group to the illumination stop, and light reflected from ON-state micromirrors is directed by the first lens group to the aperture stop.

12. The projection apparatus of claim 11, further comprising a viewing screen disposed so as to receive light conducted by the second lens group.

13. The projection apparatus of claim 11, further comprising a video data apparatus connected to the controller, the video data apparatus being operable to provide video data to the controller suitable to create an image-creating pattern of ON and OFF micromirrors on the DMD.

14. A method for reducing ghosts in an image projected from a DMD comprised of micromirrors, the method comprising:

(a) illuminating the micromirrors of the DMD with light generated by a light source and passed through an illumination stop and a first lens group;

(b) providing an aperture stop for receiving light reflected from the DMD through the first lens group; and

(c) independently controlling the micromirrors on the DMD to selectively assume an ON orientation or an OFF orientation, wherein light reflected from micromirrors in the ON orientation are directed by the first lens group to the aperture stop to become the image, and light reflected from micromirrors in the OFF orientation are directed by the first lens group to the illumination stop.