Keystone correction system and method

• US 7,441,906 B1
• Filed: 07/05/2005
• Issued: 10/28/2008
• Est. Priority Date: 07/05/2005
• Status: Active Grant

• Current Assignee: Pixelworks Semiconductor Technology Company Limited
• Original Assignee: Pixelworks Incorporated
• Inventors: Morel, Dennis, Wang, Zhongde, West, Mike, Aravamudhan, Ashok
• Primary Examiner(s): Sever; Andrew T
• Application Number:
  US11/175,786
• Time in Patent Office: 1,211 Days
• Field of Search: 353/69, 353/70, 353/121, 348745-747
• US Class Current: 353/70
• CPC Class Codes: G03B 21/14 Details
• CPC Class Codes: H04N 9/3185 Geometric adjustment, e.g. keystone or convergence optical or mechanical adjustment of convergence H04N9/317; using scanning means H04N3/22; optical or mechanical adjustments of projectors not peculiar to the presence of an electronic spatial light modulator G03B21/14

Abstract

We describe a keystone correction system and method. A vertical scalar vertically scales an input image and stores the results to a line buffer. A horizontal scalar retrieves the stored results from the line buffer and horizontally scales the stored results using the relatively small number of lines from the line buffer. The system repeats the vertically scaling, storing, and horizontal scaling until it processes all input image lines.

Claims

1. A method for keystone correction, comprising:

calculating at least one corner point of a predistorted image;

horizontally scaling an input image responsive to the calculating;

storing N lines of the horizontally scaled input image in a line buffer, where N is an integer and is less than a total number of lines in the horizontally scaled input image; and

generating the predistorted image by continuously vertically scaling the N lines; and

storing the predistorted image in a frame buffer.

2. The method of claim 1 where calculating the at least one corner point occurs responsive to receiving at least one projector parameter.

3. The method of claim 2 where receiving the at least one projector parameter includes receiving one of a horizontal pan angle and a vertical tilt angle.

4. The method of claim 1 where storing the N lines includes storing the N lines in a line memory.

5. The method of claim 1 where generating the predistorted image by continuously vertically scaling includes scanning the N lines column by column.

6. The method of claim 5 where scanning the N lines includes:

determining if there is an output pixel corresponding to a currently scanned column of pixels;

skipping the currently scanned column of pixels to advance to another adjacent column responsive to the determining;

vertically scaling the currently scanned column of pixels to generate a horizontal keystone corrected pixel responsive to the determining;

selecting a location in the output frame to place the horizontal keystone corrected pixel;

placing the horizontal keystone corrected pixel in the location; and

repeating the determining, skipping, vertically scaling, selecting, and placing until a final column of the N lines is reached.

7. The method of claim 1 comprising projecting the predistorted image on a surface.

8. A keystone correction system, comprising:

a horizontal scalar to horizontally scale an input image responsive to at least one corner of a predistorted image;

a line memory to store N lines of the horizontally scaled input image, where N is an integer and is less than a total number of lines in the horizontally scaled input image;

a vertical scalar to continuously vertically scale the N lines to generate the predistorted image;

a frame buffer to store the predistorted image; and

a projector to project the predistorted image on a surface.

9. The keystone correction system of claim 8 where the horizontal scalar is adapted to calculate the at least one corner of the predistorted image responsive to projector parameters.

10. The keystone correction system of claim 9 where the projector parameters include one of a horizontal pan and vertical tilt angle.

11. The keystone correction system of claim 8 where the vertical scalar is adapted to scan the N lines column by column.

12. The keystone correction system of claim 8 where the vertical scalar includes a processor adapted to:

determine if there is an output pixel corresponding to a currently scanned column of pixels;

skip the currently scanned column of pixels to advance to another column responsive to the determining;

vertically scale the currently scanned column of pixels to generate a horizontal keystone corrected pixel responsive to the determining;

select a location in the output frame to place the horizontal keystone corrected pixel; and

place the horizontal keystone corrected pixel in the location.

13. A keystone correction system, comprising:

means for calculating at least one corner point of a predistorted image;

means for horizontally scaling an input image responsive to the means for calculating;

means for storing N lines of the horizontally scaled input image, where N is an integer and is less than a total number of lines in the horizontally scaled input image;

means for continuously vertically scaling the N lines to generate the predistorted image;

means for storing the predistorted image; and

means for projecting the predistorted image on a surface.

14. The system of claim 13 where the means for calculating the at least one corner point includes means for calculating the at least one corner point responsive to receiving at least one projector parameter.

15. The system of claim 13 where the means for receiving the at least one projector parameter includes means for receiving one of a horizontal pan angle and a vertical tilt angle.

16. The system of claim 13 where the means for storing the N lines includes a line memory means.

17. The system of claim 13 where the means for continuously vertically scaling includes means for scanning the N lines column by column.

18. The system of claim 13 where the means for scanning includes:

means for determining if there is an output pixel corresponding to a currently scanned column of pixels;

means for skipping the currently scanned column of pixels to advance to another adjacent column responsive to the means for determining;

means for vertically scaling the currently scanned column of pixels to generate a horizontal keystone corrected pixel responsive to the means for determining;

means for selecting a location in the output frame to place the horizontal keystone corrected pixel; and

means for placing the horizontal keystone corrected pixel in the location.

19. An article comprising a storage medium, the storage medium having stored instructions, that, when executed by a machine result in:

calculating at least one corner point of a predistorted image;

horizontally scaling an input image responsive to the calculating;

storing N lines of the horizontally scaled input image in a line buffer, where N is an integer and is less than a total number of lines of the horizontally scaled input image;

continuously vertically scaling the N lines to generate the predistorted image;

storing the predistorted image in a frame buffer; and

projecting the predistorted image on a surface.

20. The article of claim 19 where calculating the least one corner occurs responsive to receiving at least one projector parameter.

21. The article of claim 19 where receiving the at least one projector parameter includes receiving one of a horizontal pan angle and a vertical tilt angle.

22. The article of claim 19 where storing the N lines includes storing in a line memory.

23. The article of claim 19 where continuously vertically scaling includes scanning the N lines column by column.

24. The article of claim 23 where scanning the N lines column by column includes:

determining if there is an output pixel corresponding to a currently scanned column of pixels;

skipping the currently scanned column of pixels to advance to another adjacent column responsive to the determining;

vertically scaling the currently scanned column of pixels to generate a horizontal keystone corrected pixel responsive to the determining;

selecting a location in the output frame to place the horizontal keystone corrected pixel;

placing the horizontal keystone corrected pixel in the location; and

repeating the determining, skipping, vertically scaling, selecting, and placing until a final column of the N lines is reached.