Offset projection distortion correction

• US 8,540,375 B2
• Filed: 11/30/2007
• Issued: 09/24/2013
• Est. Priority Date: 11/30/2007
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Destain, Patrick Rene
• Primary Examiner(s): Legasse, Jr., Francis M
• Application Number:
  US11/948,811
• Publication Number:
  US 20090141250A1
• Time in Patent Office: 2,125 Days
• Field of Search: 353 69- 72, 353/101, 359668-671, 359/443, 359/449, 359/451, 359/456, 359/460
• US Class Current: 353/70
• CPC Class Codes: G03B 21/10 Projectors with built-in or built-on screen
• CPC Class Codes: G03B 21/28 Reflectors in projection beam in illumination beam G03B21/2066

Abstract

A system and method for correcting optical distortion in an off-axis system is provided. The offset between the center of a display plane and the optical axis of the projection lens system is configured such that the offset is greater than half the vertical dimension of the display plane. In this manner, the distortion, such as a pincushion-type or barrel-type of distortion, is not symmetrical about the horizontal axis. In this scenario, the display plane, the projection lens system, a folding mirror, and/or the spatial light modulator may be tilted such that a keystone effect is induced. This keystone effect may be used to offset the distortion, particularly the pincushion-type or barrel-type of distortions.

Claims

1. A rear-projection image display system, comprising:

a display screen having a display plane with a vertical height and a vertical height center;

a folding mirror;

a projection system having a projection optical axis; and

a housing enclosing the display plane, folding mirror and projection system;

wherein the folding mirror is positioned relative to the display plane and the projection system for folding the projection optical axis by reflecting light projected rearwardly from the projection system onto itself and onto the display plane;

wherein the projection system is positioned relative to the display plane with a vertical offset between the projection optical axis and the vertical height center of the display plane by an optical offset that is about one-half or greater than the vertical height of the display plane; and

wherein the display plane is tilted relative to a plane orthogonal to the projection optical axis by a vertical offset angle to induce a keystone distortion in the displayed image which substantially compensates for a pincushion or barrel distortion in the orthogonal plane.

2. The system of claim 1, wherein the optical offset is about one-half the vertical height.

3. The system of claim 1, wherein the vertical offset angle is about 0.12°

.

4. The system of claim 1, wherein the keystone distortion is a negative keystone distortion that substantially compensates for a pincushion distortion in the orthogonal plane.

5. The system of claim 1, wherein the keystone distortion is a positive keystone distortion that substantially compensates for a barrel distortion in the orthogonal plane.

6. The system of claim 1, wherein the induced keystone distortion is determined by the relationship:

7. The system of claim 2, wherein the vertical offset angle is about 0.12°

.

8. The system of claim 7, wherein the keystone distortion is a negative keystone distortion that substantially compensates for a pincushion distortion in the orthogonal plane.

9. The system of claim 7, wherein the keystone distortion is a positive keystone distortion that substantially compensates for a barrel distortion in the orthogonal plane.