Optical navigation system with object detection

• US 8,928,626 B2
• Filed: 04/27/2011
• Issued: 01/06/2015
• Est. Priority Date: 04/27/2011
• Status: Active Grant

• Current Assignee: PixArt Imaging Incorporated
• Original Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Inventors: Song, Willie, Tan, Zi Hao, Tan, Shan Chong
• Primary Examiner(s): Lefkowitz, Sumati
• Assistant Examiner(s): Tung, David
• Application Number:
  US13/095,576
• Publication Number:
  US 20120274606A1
• Time in Patent Office: 1,350 Days
• Field of Search: 345156-184
• US Class Current: 345/175
• CPC Class Codes: G06F 2203/0338 Fingerprint track pad, i.e. fingerprint sensor used as pointing device tracking the fingertip image
• CPC Class Codes: G06F 3/03547 Touch pads, in which fingers can move on a surface
• CPC Class Codes: G06F 3/042 by opto-electronic means

Abstract

An optical finger navigation system with object detection is provided for preventing cursor movement if a user'"'"'s finger has been lifted from the navigation surface. The optical finger navigation system may include a light source, an image sensor and an object detection engine. The object detection engine may be operatively coupled with the image sensor and the light source to selectively report motion data upon determining the presence of an object by comparing a scaled-up pixel value with a threshold value. The lift detection engine may be incorporated in a microcontroller, wherein the microcontroller may be added to a navigation system to provide an additional object detection feature.

Claims

1. An optical navigation system comprising:

a light source configured to emit light;

a sensor configured to capture a light-on frame and a light-off frame;

wherein both frames are captured at a shutter value;

an object detection engine coupled to the sensor, the object detection engine configured to determine a first set number for photosensitive pixel elements used in acquiring the light-on frame and a second set number for photosensitive pixel elements used in acquiring the light-off frame, the object detection engine is configured to report a motion data by comparing a scaled-up pixel value with a threshold value; and

a calculator of the object detection engine configured to calculate the scaled-up pixel value, wherein the calculator is configured to determine a pixel difference between the first set number and the second set number to determine a ratio of the pixel difference to the shutter value, and to multiply the ratio with a multiplying factor.

2. The optical navigation system of claim 1, wherein the object detection engine is configured to report the motion data if the scaled-up pixel value is greater than the threshold value.

3. The optical navigation system of claim 1, wherein the object detection engine is configured to report a presence of an object if the scaled-up pixel value is greater than the threshold value.

4. The optical navigation system of claim 3, wherein the object detection engine is configured to report the motion data upon determining the presence of the object.

5. The optical navigation system of claim 3, wherein the threshold value is a predetermined minimum scaled-up value at which the object detection engine detects the presence of the object.

6. The optical navigation system of claim 1, further comprising a memory configured to store the threshold value, the first set number and the second set number.

7. The optical navigation system of claim 6, wherein the object detection engine is configured to calculate subsequent scaled-up pixel value without the light-on frame.

8. The optical navigation system of claim 7, wherein the object detection engine is configured to calculate subsequent scaled-up value based on the first set number and the shutter value stored in the memory, and a new second set number from a current light-off frame.

9. An optical navigation method comprising:

capturing a light-on frame and a light-off frame at a same shutter value;

determining a first set number for photosensitive pixel elements used in acquiring the light-on frame and a second set number for photosensitive pixel elements used in acquiring the light-off frame;

calculating the scaled-up pixel value based on the first set number, the second set number and the shutter value at least by;

determining a pixel difference between the first set number and the second set number; and

determining a ratio of the pixel difference to the shutter value, and multiplying the ratio with a multiplying factor;

reporting a motion data upon determining a presence of an object by comparing the scaled-up pixel value with a threshold value.

10. The method of claim 9, further comprising reporting the motion data upon determining the scaled-up pixel value is greater than the threshold value.

11. The method of claim 9, further comprising reporting the presence of the object if the scaled-up pixel value is greater than the threshold value.

12. The method of claim 9, wherein the threshold value is a predetermined minimum scaled-up value at which the object detection engine detects the presence of the object is detected.

13. The method of claim 9, further comprising storing the first set number and the second set number and the threshold value in a memory.

14. The method of claim 13, further comprising calculating a subsequent scaled-up value based on the first set number and the shutter value stored in the memory, and a new second set number from current light-off frame.

15. An optical navigation device comprising:

a light source configured to emit light;

a sensor configured to capture a light-on frame and a subsequent light-off frame wherein both frames are captured at a same shutter value;

a navigation engine configured to provide a navigation operation; and

an object detection engine coupled to the sensor and the navigation engine, the object detection engine configured to determine a first set number for photosensitive pixel elements used in acquiring the light-on frame and a second set number for photosensitive pixel elements used for acquiring the light-off frame, the object detection engine is configured to report a motion data for navigation operation by comparing a scaled-up pixel value with a threshold value;

wherein the object detection engine is configured to calculate the scaled-up pixel value using the first set number, the second set number and the shutter value, and

wherein the object detection engine is configured to calculate subsequent scaled-up pixel value without a light-on frame.

16. The optical navigation device of claim 15, wherein the object detection engine is configured to report the motion data if the scaled-up pixel value is greater than the threshold value.

17. The optical navigation device of claim 15, wherein the object detection engine comprises a calculator configured to calculate the scaled-up pixel value.

18. The optical navigation device of claim 17, wherein the calculator is configured to determine a pixel difference between the first set number and the second set number.

19. The optical navigation device of claim 18, wherein the calculator is configured to determine a ratio of the pixel difference to the shutter value, and configured to multiply the ratio with a multiplying factor.