Determination of a navigation window in an optical navigation system

• US 20050281466A1
• Filed: 06/17/2004
• Published: 12/22/2005
• Est. Priority Date: 06/17/2004
• Status: Active Grant

• Current Assignee: PixArt Imaging Incorporated
• Original Assignee: Avago Technologies ECBU IP Singapore Pte Limited (Broadcom, Inc.)
• Inventors: Siah, Tiong Hong, Kong, Heng Yew
• Granted Patent: US 7,565,034 B2
• Time in Patent Office: Days
• US Class Current: 382/199
• CPC Class Codes: G06F 3/0317 in co-operation with a patterned surface, e.g. absolute position or relative movement detection for an optical mouse or pen positioned with respect to a coded surface
• CPC Class Codes: G06F 3/0383 Signal control means within the pointing device

Abstract

A technique for reducing navigation errors that are caused by uneven illumination involves using only the portion of the image data that is properly illuminated in the correlation process. The portion of the image data that is used for optical navigation is established by summing the image data on a per-slice basis, comparing the per-slice sums to a pre-established intensity threshold, and defining boundaries of the navigation window in response to the comparison. Boundaries are set at the points where the per-slice sums equal the pre-established intensity threshold.

Claims

1. An optical navigation method comprising:

establishing a threshold;

obtaining image data;

summing the image data on a per-slice basis to create per-slice sums;

comparing the per-slice sums to the threshold; and

defining a boundary of a navigation window in response to the comparison.

2. The optical navigation method of claim 1 wherein the defining of the boundary includes setting the boundary in response to a per-slice sum that is less than the threshold.

3. The optical navigation method of claim 1 wherein the summing of the image data on a per-slice basis comprises summing the image data on a per-column basis and on a per-row basis.

4. The optical navigation method of claim 3 wherein the establishing of the threshold comprises establishing a column threshold and a row threshold and wherein the comparing of the per-slice sums to the threshold comprises comparing the per-column sums to the per-column threshold and comparing the per-row sums to the per-row threshold.

5. The optical navigation method of claim 4 wherein the defining of the boundary comprises:

defining a first boundary in response to the comparison of the per-column sums to the column threshold; and

defining a second boundary in response to the comparison of the per-row sums to the row threshold.

6. The optical navigation method of claim 5 wherein:

the first boundary is parallel to the columns over which the per-column sums are obtained; and

the second boundary is parallel to the rows over which the per-row sums are obtained.

7. The optical navigation method of claim 1 wherein summing the image data on a per-slice basis comprises adding intensity values from image sensor photodetectors in the same column or the same row.

8. The optical navigation method of claim 1 wherein the image data is an array of digital intensity values.

9. The optical navigation method of claim 1 further comprising dynamically adjusting the boundary of the navigation window in response to newly acquired image data.

12. The optical navigation method of claim 1 wherein:

establishing the first boundary further comprises establishing the boundary in response to a per-column sum that is less than the column threshold; and

establishing the second boundary further comprises establishing the boundary in response to a per-row sum that is less than the row threshold.

10. An optical navigation method comprising:

obtaining image data;

summing the image data on a per-column basis and on a per-row basis; and

defining boundaries of a navigation window in response to the summing.

11. The optical navigation method of claim 10 wherein defining the boundaries comprises:

establishing a column threshold and a row threshold;

comparing the per-column sums to the column threshold;

establishing a first boundary of the navigation window in response to the comparison of the per-column sums to the column threshold;

comparing the per-row sums to the row threshold; and

establishing a second boundary of the navigation window in response to the comparison of the per-row sums to the row threshold.

13. The optical navigation method of claim 11 wherein:

the first boundary is parallel to the columns over which the per-column sums are obtained; and

the second boundary is parallel to the rows over which the per-row sums are obtained.

14. The optical navigation method of claim 10 wherein summing the image data on a per-column basis comprises adding intensity values from image sensor photodetectors in the same column and wherein summing the image data on a per-row basis comprises adding intensity values from image sensor photodetectors in the same row.

15. The optical navigation method of claim 10 wherein the boundaries are dynamic boundaries that are changed in response to new image data.

16. The optical navigation method of claim 10 wherein defining the boundaries comprises:

establishing a column threshold and a row threshold;

comparing the per-column sums to the column threshold;

establishing a first pair of parallel boundaries of the navigation window in response to the comparison of the per-column sums to the column threshold, wherein the first pair of parallel boundaries is parallel to the columns over which the per-column sums are established;

comparing the per-row sums to the row threshold; and

establishing a second pair of parallel boundaries of the navigation window in response to the comparison of the per-row sums to the row threshold, wherein the first pair of parallel boundaries is parallel to the rows over which the per-row sums are established.

17. A system for processing image data for optical navigation comprising:

an image sensor configured to obtain image data;

pre-processing logic configured to sum intensity values of first image data on a per-column basis and on a per-row basis; and

boundary logic configured to define boundaries of a navigation window in response to the per-column and per-row sums.

18. The optical navigation system of claim 17 wherein boundary logic is further configured to:

establish a column threshold and a row threshold;

compare the per-column sums to the column threshold;

establish a first boundary of the navigation window in response to the comparison of the per-column sums to the column threshold;

compare the per-row sums to the row threshold; and

establish a second boundary of the navigation window in response to the comparison of the per-row sums to the row threshold.

19. The optical navigation system of claim 18 wherein the boundary logic is further configured to:

establish the boundary in response to a per-column sum that is less than the column threshold; and

establish the boundary in response to a per-row sum that is less than the row threshold.

20. The optical navigation system of claim 18 wherein:

the first boundary is parallel to the columns over which the per-column sums are obtained; and

the second boundary is parallel to the rows over which the per-row sums are obtained.