Multiple fingers contact sensing method for emulating mouse buttons and ...

1. A method for detecting the operative coupling of multiple fingers to a touch sensor involving the steps of

scanning the touch sensor to (a) identify a first maxima in a signal corresponding to a first finger, (b) identify a minima following the first maxima, (c) identify a second maxima in a signal corresponding to a second finger following said minima, and

providing an indication of the simultaneous presence of two fingers in response to identification of said first and second maxima.

2. The method of claim 1 further including the step of causing a pointing device click function to occur in response to the detection of at least a second maxima.

3. The method of claim 1 further including the step of enabling a "drag" function to occur in response to the detection of at least a second maxima.

4. The method of claim 1 further including the step of enabling a "select" function in response to the detection of at least a second maxima.

5. The method of claim 1 further including the step of enabling an "ink" function in response to the detection of at least a second maxima.

6. The method of claim 1 wherein said touch sensor includes a plurality of lines, said maxima being a largest local variation in a signal value on one of said lines due to capacitive coupling of a finger.

7. The method of claim 6 wherein said maxima are peaks.

8. The method of claim 1 further comprising the step of comparing a distance between said first maxima and said second maxima to a predefined threshold.

9. The method of claim 1 further comprising the steps of:

providing a first control function in response to the detection of the movement of two fingers:

detecting the reaching of an edge of said touch sensor by said two fingers;

detecting a first time corresponding to the removal of said fingers from said touch sensor;

detecting a second time corresponding to the replacement of said two fingers on said touch sensor; and

continuing said first control function if said first and second times are within a predetermined time limit of each other.

10. The method of claim 1 further comprising the step of:

detecting a distance between said first and second maxima.

11. The method of claim 1 further comprising the step of:

providing a drag control function in response to detecting a movement in substantial unison of two said fingers.

12. The method of claim 1 further comprising the step of:

providing a click function in response to the removal and reappearance of said second maxima within a predetermined period of time.

13. The method of claim 1 further comprising the steps of:

detecting a movement of said first maxima;

detecting a removal and replacement of said maxima within a predetermined time period;

controlling a cursor function in response to said movement of said first maxima; and

providing a control function in response to said removal and replacement of said second maxima.

14. The method of claim 1 further comprising the step of:

selecting an appropriate control function based on a combination of a number of fingers detected, an amount of time said fingers are detected, and any movement of said fingers.

15. The method of claim 1 further comprising the step of determining if said first and second maxima are within 5 centimeters, and only providing said indication of the presence of two fingers if said first and second maxima are within 5 centimeters.

16. The method of claim 1 further comprising the step of calculating first and second centroids corresponding to said first and second fingers.

17. The method of claim 1 wherein said first and second maxima are required to be higher than a first threshold, and said minima is required to be less than a second threshold.

18. A touch sensor for detecting the operative coupling of multiple fingers comprising:

means for scanning the touch sensor to (a) identify a first maxima in a signal corresponding to a first finger, (b) identify a minima following the first maxima, and (c) identify a second maxima in a signal corresponding to a second finger following said minima, and

means for providing an indication of the simultaneous presence of two fingers in response to identification of said first and second maxima.

19. The touch sensor of claim 18 further comprising:

means for selecting an appropriate control function based on a combination of a number of fingers detected, an amount of time said fingers are detected, and any movement of said fingers.

20. The touch sensor of claim 18 wherein said touch sensor includes a plurality of lines, said maxima being a largest local variation in a signal value on one of said lines due to capacitive coupling of a finger.

21. The touch sensor of claim 18 wherein said maxima are peaks.

22. The touch sensor of claim 18 further comprising means for comparing a distance from said first maxima to said second maxima to a predefined threshold.

23. The touch sensor of claim 18 further comprising:

means for providing a first control function in response to the detection of the movement of two fingers:

means for detecting the reaching of an edge of said touch sensor by said two fingers;

means for detecting a first time corresponding to the removal of said fingers from said touch sensor;

means for detecting a second time corresponding to the replacement of said two fingers on said touch sensor; and

means for continuing said first control function if said first and second times are within a predetermined time limit of each other.

24. The touch sensor of claim 18 further comprising:

means for detecting a distance between said first and second maxima.

25. The touch sensor of claim 18 further comprising:

means for providing a drag control function in response to detecting a movement in substantial unison of two said fingers.

26. The touch sensor of claim 18 further comprising:

means for providing a click function in response to the removal and reappearance of said second maxima within a predetermined period of time.

27. The touch sensor of claim 18 further comprising:

means for detecting a movement of said first maxima;

means for detecting a removal and replacement of said maxima within a predetermined time period;

means for controlling a cursor function in response to said movement of said first maxima; and

means for providing a control function in response to said removal and replacement of said second maxima.

28. The touch sensor of claim 18 further comprising:

means for selecting an appropriate control function based on a combination of a number of fingers detected, an amount of time said fingers are detected, and any movement of said fingers.

29. The sensor of claim 18 further comprising means for determining if said first and second maxima are within 5 centimeters, and only providing said indication of the presence of two fingers if said first and second maxima are within 5 centimeters.

30. The sensor of claim 18 further comprising means for calculating first and second centroids corresponding to said first and second fingers.

31. The sensor of claim 18 wherein said first and second maxima are required to be higher than a first threshold, and said minima is required to be less than a second threshold.