Touch system and pointer coordinate detection method therefor

• US 8,659,577 B2
• Filed: 06/11/2010
• Issued: 02/25/2014
• Est. Priority Date: 08/28/2009
• Status: Expired due to Fees

• Current Assignee: PixArt Imaging Incorporated
• Original Assignee: PixArt Imaging Incorporated
• Inventors: Su, Tzung Min, Chen, Hsin Chia, Lu, Chih Hung
• Primary Examiner(s): Lefkowitz, Sumati
• Assistant Examiner(s): FOX, JOSEPH PATRICK
• Application Number:
  US12/813,599
• Publication Number:
  US 20110050644A1
• Time in Patent Office: 1,355 Days
• Field of Search: 345156-175
• US Class Current: 345/175
• CPC Class Codes: G06F 3/0428 by sensing at the edges of the touch surface the interruption of optical paths, e.g. an illumination plane, parallel to the touch surface which may be virtual sensing beam interruptions in a planar beam grid of an optical touch-screen G06F3/0421

Abstract

A pointer coordinate detection method for a touch system includes the steps of: capturing an image window looking across a plate surface with at least one image sensor; identifying a height coordinate of a pointer relative to the touch system according to a variation of each column of pixels in the image window; and calculating a plane coordinate of the pointer relative to the touch system according to an image position of the pointer in the image window. The present invention further provides a touch system.

Claims

1. A pointer height detection method for a touch system, the pointer height detection method comprising:

capturing an image window looking across a plate surface with at least one image sensor;

calculating a variation of each column of pixels in the image window;

calculating a smallest variation of a variation of each column of pixels in the image window when the image window contains an image of a pointer; and

comparing a value of the smallest variation with at least one threshold to identify a height of the pointer relative to the plate surface, wherein

the at least one threshold defines a predetermined height of the pointer associated with the value of the smallest variation.

2. The pointer height detection method as claimed in claim 1, further comprising:

controlling an image display to execute a corresponding function according to the height identified.

3. The pointer height detection method as claimed in claim 2, wherein the corresponding function is a cursor motion, a writing function or a drawing function.

4. The pointer height detection method as claimed in claim 1, further comprising:

activating the touch system when the variation of any column of pixels in the image window is smaller than a first threshold.

5. The pointer height detection method as claimed in claim 4, further comprising:

processing the image window to detect at least one image position associated with pointer in the image window; and

calculating a plane coordinate of the pointer relative to the plate surface according to the image position.

6. The pointer height detection method as claimed in claim 1, further comprising:

identifying that the pointer contacts the plate surface when the variation of any column of pixels in the image window is smaller than a second threshold.

7. The pointer height detection method as claimed in claim 1, wherein a field of view of the image sensor encompasses the plate surface.

8. The pointer height detection method as claimed in claim 1, further comprising:

providing at least one reflecting unit to reflect light needed by the image sensor for capturing images, wherein a longitudinal field of view of the image sensor is larger than a height of the reflecting unit.

9. The pointer height detection method as claimed in claim 1, wherein the variation is a standard deviation of one column of pixels or an average of absolute values of the differences between each pixel value and an average pixel value of one column of pixels.

10. A pointer coordinate detection method for a touch system, the pointer coordinate detection method comprising:

capturing an image window looking across a plate surface with at least one image sensor;

calculating a smallest variation of a variation of each column of pixels in the image window when the image window contains an image of a pointer;

identifying a height coordinate of the pointer relative to the touch system according to a relationship between a value of the smallest variation and at least one threshold, wherein the at least one threshold defines a predetermined height coordinate of the pointer associated with the value of the smallest variation; and

calculating a plane coordinate of the pointer relative to the touch system according to an image position associated with the pointer in the image window.

11. The pointer coordinate detection method as claimed in claim 10, further comprising:

providing at least one reflecting minor and at least one reflecting unit to reflect light needed by the image sensor for capturing images, wherein the image in the image window is formed by the pointer blocking the reflecting minor or the reflecting unit.

12. The pointer coordinate detection method as claimed in claim 10, further comprising:

calculating a variation of each column of pixels in the image window; and

comparing the variation of at least one column of pixels with the smallest variation and the at least one threshold to identify the height coordinate.

13. The pointer coordinate detection method as claimed in claim 12, further comprising:

activating the touch system when the variation of any column of pixels in the image window is smaller than a first threshold.

14. The pointer coordinate detection method as claimed in claim 12, further comprising:

identifying that the pointer contacts the plate surface when the variation of any column of pixels in the image window is smaller than a second threshold.

15. The pointer coordinate detection method as claimed in claim 10, further comprising:

controlling an image display to execute a corresponding function according to the height coordinate and the plane coordinate.

16. The pointer coordinate detection method as claimed in claim 15, wherein the corresponding function is a cursor motion, a writing function and a drawing function.

17. The pointer coordinate detection method as claimed in claim 10, wherein the variation is a standard deviation of one column of pixels or an average of absolute values of the differences between each pixel value and an average pixel value of one column of pixels.

18. A touch system, comprising:

a plate, having a plate surface;

at least one light source, configured to illuminate the plate along the plate surface;

at least one reflecting unit, configured to reflect light from the light source;

at least one image sensor, configured to capture an image window containing an image of a pointer blocking the reflecting unit; and

a processing unit configured to

process the image window,

calculate a smallest variation of a variation of each column of pixels in the image window when the image window contains an image of a pointer, and

identify a height coordinate of the pointer relative to the plate surface according to a relationship between a value of the smallest variation and at least one threshold, wherein the at least one threshold defines a predetermined height coordinate of the pointer associated with the value of the smallest variation.

19. The touch system as claimed in claim 18, wherein the image sensor is disposed in a corner intersected by two sides of the plate surface, and the touch system further comprises a reflecting mirror disposed at a side of the plate surface not adjacent to the image sensor.

20. The touch system as claimed in claim 18, wherein the processing unit is further configured to compare the variation of at least one column of pixels with the smallest variation and the at least one threshold to identify the height coordinate.

21. The touch system as claimed in claim 18, wherein the processing unit is further configured to identify a plane coordinate of the pointer relative to the plate surface according to an image position associated with the pointer in the image window.

22. The touch system as claimed in claim 21, further comprising:

an image display coupled to the processing unit, wherein the processing unit is further configured to control the image display to execute a corresponding function according to the height coordinate and the plane coordinate.

23. The touch system as claimed in claim 18, wherein the variation is a standard deviation of one column of pixels or an average of absolute values of the differences between each pixel value and an average pixel value of one column of pixels.