Determination of a navigation window in an optical navigation system

• US 7,565,034 B2
• Filed: 06/17/2004
• Issued: 07/21/2009
• 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 Heng, Kong, Heng Yew
• Primary Examiner(s): Ahmed; Samir A.
• Assistant Examiner(s): TSAI, TSUNG YIN
• Application Number:
  US10/870,192
• Publication Number:
  US 20050281466A1
• Time in Patent Office: 1,860 Days
• Field of Search: 382/305, 382144-151, 382168-172, 382/181
• US Class Current: 382/305
• 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:

a processor to implement the step of;

establishing an illumination threshold, wherein the illumination threshold is defined in terms of a minimum intensity value sum for an entire slice of image data;

obtaining sets of image data, wherein the step of obtaining sets of image data comprises illuminating a navigation surface and detecting light that is reflected from the navigation surface;

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

comparing the per-slice sums to the illumination threshold;

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

wherein the illumination threshold is related to a minimum illumination that is acceptable within the navigation window to determine relative displacement between the obtained sets of image data; and

determining relative displacement between the obtained sets of image data using only portion of the obtained sets of image data that falls within the navigation window.

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 illumination 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 illumination threshold comprises establishing a column illumination threshold and a row illumination threshold and wherein the comparing of the per-slice sums to the illumination threshold comprises comparing the per-column sums to the per-column illumination threshold and comparing the per-row sums to the per-row illumination 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 illumination threshold; and

defining a second boundary in response to the comparison of the per-row sums to the row illumination 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 4 wherein the column and row illumination thresholds are related to a minimum illumination that is acceptable within a navigation window.

8. 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.

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

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

11. An optical navigation method comprising:

a processor to implement the steps of;

obtaining sets of image data, wherein the step of obtaining sets of image data comprises illuminating a navigation surface and detecting light that is reflected from the navigation surface;

summing the obtained sets of 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, wherein defining the boundaries of the navigation window comprises;

establishing a column illumination threshold and a row illumination threshold, wherein the column illumination threshold is defined in terms of a minimum intensity value sum for an entire column of image data and wherein the row illumination threshold is defined in terms of a minimum intensity value sum for an entire row of image data and wherein the column and row illumination thresholds are related to a minimum illumination that is acceptable within the navigation window to determine relative displacement between the obtained sets of image data;

comparing the per-column sums to the column illumination threshold;

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

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

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

determining relative displacement between the obtained sets of image data using only portions of the obtained sets of image data that falls within the navigation window.

12. The optical navigation method of claim 11 wherein:

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

establishing the second boundary further comprises establishing the boundary in response to a per-row sum that is less than the row illumination 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 11 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 11 wherein the boundaries are dynamic boundaries that are changed in response to new image data.

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

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

a light source configured to illuminate a navigation surface;

an image sensor configured to obtain sets of image data in response to light that is reflected from the navigation surface;

pre-processing logic configured to sum intensity values of the obtained sets 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, wherein the boundary logic is further configured to;

establish a column illumination threshold and a row illumination threshold, wherein the column illumination threshold is defined in terms of a minimum intensity value sum for an entire column of image data and wherein the row illumination threshold is defined in terms of a minimum intensity value sum for an entire row of image data and wherein the column and row illumination thresholds are related to a minimum illumination that is acceptable within the navigation window to determine relative displacement between the obtained sets of image data;

compare the per-column sums to the column illumination threshold;

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

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

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

a processing unit configured to determine relative displacement between the obtained sets of image data using only portions of the obtained sets of image data that falls within the navigation window.

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

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

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

19. The optical navigation system of claim 17 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.