OPTICAL NAVIGATION SYSTEM WITH OBJECT DETECTION

• US 20120274606A1
• Filed: 04/27/2011
• Published: 11/01/2012
• Est. Priority Date: 04/27/2011
• Status: Active Grant

• Current Assignee: PixArt Imaging Incorporated
• Original Assignee: Avago Technologies ECBU IP Singapore Pte Limited (Broadcom, Inc.)
• Inventors: Song, Willie, Tan, Zi Hao, Tan, Shan Chong
• Granted Patent: US 8,928,626 B2
• Time in Patent Office: Days
• 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; and

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.

2. The optical navigation system of claim 1, wherein the object detection engine is configured to calculate the scaled-up pixel value based on the first set number, the second set number and the shutter value.

3. 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.

4. 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.

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

6. The optical navigation system of claim 4, wherein the threshold value is a predetermined minimum scaled-up value at which the object detection engine detects the presence of an object.

7. The optical navigation system of claim 2, wherein the object detection engine further comprises a calculator configured to calculate the scaled-up pixel value, wherein the calculator:

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

determines a ratio of the pixel difference to the shutter value, and

multiplies the ratio with a multiplying factor.

8. 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.

9. The optical navigation system of claim 8, wherein the object detection engine is configured to calculate subsequent scaled-up pixel value without a light-on frame.

10. The optical navigation system of claim 9, 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.

11. 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, and

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

12. The method of claim 11, further comprising calculating the scaled-up pixel value based on the first set number, the second set number and the shutter value.

13. The method of claim 11, further comprising reporting the motion data upon determining the scaled-up pixel value is greater than the threshold value.

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

15. The method of claim 14, further comprising:

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.

16. The method of claim 11, wherein the threshold value is a predetermined minimum scaled-up value at which the object detection engine detects the presence of an object.

17. The method of claim 11, further comprising storing the first and the second set number and the threshold value in a memory.

18. The method of claim 17, 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.

19. 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.

20. The optical navigation device of claim 19, wherein the object detection engine is configured to report the motion data if the scaled-up pixel value is greater than the threshold value