Techniques for reducing jitter for taps

• US 7,932,896 B2
• Filed: 06/13/2007
• Issued: 04/26/2011
• Est. Priority Date: 06/13/2007
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Westerman, Wayne Carl
• Primary Examiner(s): Eisen; Alexander
• Assistant Examiner(s): YEUNG, MATTHEW M
• Application Number:
  US11/818,476
• Publication Number:
  US 20080309630A1
• Time in Patent Office: 1,413 Days
• Field of Search: None
• US Class Current: 345/173
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/04883 for inputting data by handwriting, e.g. gesture or text

Abstract

Distinguishing sloppy taps from sliding motions is disclosed using an algorithm that can take into account both a time instability factor Tinst and a touch instability factor Zinst. A limited amount of motion per frame can be subtracted off immediately following the detection of a touch event. Small lateral motions indicative of a sloppy tap can be suppressed, while fast finger motions indicative of a quick, long cursor movement can immediately pass through the filter without being suppressed by a significant amount. A motion pass-through suppression factor can be applied subtractively to motion in particular direction as a function of Zinst and Tinst, wherein Zinst can represent a suppression value given as a finger speed for a particular percentage change in touch instability per frame, and Tinst can represent a suppression value given as finger speed for a particular tpress.

Claims

1. A method for suppressing position change in a detected image of touch to assist in distinguishing tapping motions from sliding motions on a touch sensor panel, comprising:

computing a time instability factor in accordance with a time instability function that provides a first amount of suppressed position change per frame for a given time since the image of touch was detected;

subtracting the first amount of suppressed position change per frame from a first position change per frame value for the detected image of touch to obtain a suppressed position change per frame for the detected image of touch; and

utilizing the suppressed position change per frame for the detected image of touch to assist in distinguishing tapping motions from sliding motions on the touch sensor panel.

2. The method of claim 1, the time instability function starting at a maximum suppressed position change per frame value at a time when the image if touch is first detected and tapering off to a minimum suppressed position change per frame value for a time greater than or equal to a predetermined delay after the image of touch was first detected.

3. The method of claim 1, wherein the first amount of position change per frame is a detected position change per frame.

4. The method of claim 1, further comprising:

applying a hysteresis filter to a detected position change per frame to generate a reported position change per frame that delays the detected position change per frame by a predetermined number of pixels;

wherein the first position change per frame is the reported position change per frame.

5. The method of claim 4, further comprising identifying the reported position change per frame as an actionable position change per frame if an event flag is set.

6. The method of claim 5, further comprising setting the event flag if the reported position change per frame is not from a detected hover event.

7. The method of claim 5, further comprising setting the event flag if the suppressed position change per frame is non-zero.

8. A method for suppressing position change in a detected image of touch to assist in distinguishing tapping motions from sliding motions on a touch sensor panel, comprising:

computing a touch instability factor in accordance with a touch instability function that provides a first amount of suppressed position change per frame for a given amount of touch instability per frame;

subtracting the first amount of suppressed position change per frame from a first position change per frame value for the detected image of touch to obtain a suppressed position change per frame for the detected image of touch; and

utilizing the suppressed position change per frame for the detected image of touch to assist in distinguishing tapping motions from sliding motions on the touch sensor panel.

9. The method of claim 8, the touch instability function starting at a minimum suppressed position change per frame value at zero percentage change in touch instability per frame and reaching a maximum suppressed position change per frame value for percentage changes in touch instability per frame greater than or equal to a predetermined percentage.

10. The method of claim 8, wherein the first amount of position change per frame is a detected position change per frame.

11. The method of claim 8, further comprising:

applying a hysteresis filter to a detected position change per frame to generate a reported position change per frame that delays the detected position change per frame by a predetermined number of pixels;

wherein the first position change per frame is the reported position change per frame.

12. The method of claim 11, further comprising identifying the reported position change per frame as an actionable position change per frame if an event flag is set.

13. The method of claim 12, further comprising setting the event flag if the reported position change per frame is not from a detected hover event.

14. The method of claim 12, further comprising setting the event flag if the suppressed position change per frame is non-zero.

15. A method for suppressing position change in a detected image of touch to assist in distinguishing tapping motions from sliding motions on a touch sensor panel, comprising:

computing a time instability factor in accordance with a time instability function that provides a first amount of suppressed position change per frame for a given time tpress since the image of touch was detected;

computing a touch instability factor in accordance with a touch instability function that provides a second amount of suppressed position change per frame for a given amount of touch instability per frame;

subtracting a larger of the first and second amount of suppressed position change per frame from a first position change per frame value for the detected image of touch to obtain a suppressed position change per frame for the detected image of touch; and

utilizing the suppressed position change per frame for the detected image of touch to assist in distinguishing tapping motions from sliding motions on the touch sensor panel.

16. The method of claim 15, the touch instability function starting at a maximum suppressed position change per frame value at a time when the image if touch is first detected and tapering off to a minimum suppressed position change per frame value for a time greater than or equal to a predetermined delay after the image of touch was first detected.

17. The method of claim 15, the touch instability function starting at a minimum suppressed position change per frame value at zero percentage change in touch instability per frame and reaching a maximum suppressed position change per frame value for percentage changes in touch instability per frame greater than or equal to a predetermined percentage.

18. The method of claim 15, wherein the first position change per frame is a detected position change per frame.

19. The method of claim 15, further comprising:

applying a hysteresis filter to a detected position change per frame to generate a reported position change per frame that delays the detected position change per frame by a predetermined number of pixels;

wherein the first position change per frame is the reported position change per frame.

20. The method of claim 19, further comprising identifying the reported position change per frame as an actionable position change per frame if an event flag is set.

21. The method of claim 20, further comprising setting the event flag if the reported position change per frame is not from a detected hover event.

22. The method of claim 20, further comprising setting the event flag if the suppressed position change per frame is non-zero.

23. A method for suppressing position change in a detected image of touch to assist in distinguishing tapping motions from sliding motions on a touch sensor panel, comprising:

computing a time instability factor in accordance with a time instability function that provides a first amount of suppressed position change per frame immediately after the image of touch is detected to account for position changes during touchdown, and tapering off thereafter;

computing a touch instability factor in accordance with a touch instability function that provides a second amount of suppressed position change per frame for large amounts of touch instability per frame to account for position changes during touchdown and liftoff;

subtracting a larger of the first and second amount of suppressed position change per frame from a first position change per frame value for the detected image of touch to obtain a suppressed position change per frame for the detected image of touch; and

utilizing the suppressed position change per frame for the detected image of touch to assist in distinguishing tapping motions from sliding motions on the touch sensor panel.

24. The method of claim 23, the touch instability function starting at a maximum suppressed position change per frame value at a time when the image if touch is first detected and tapering off to a minimum suppressed position change per frame value for a time greater than or equal to a predetermined delay after the image of touch was first detected.

25. The method of claim 23, the touch instability function starting at a minimum suppressed position change per frame value at zero percentage change in touch instability per frame and reaching a maximum suppressed position change per frame value for percentage changes in touch instability per frame greater than or equal to a predetermined percentage.

26. The method of claim 23, wherein the first position change per frame is a detected position change per frame.

27. The method of claim 23, further comprising:

applying a hysteresis filter to a detected position change per frame to generate a reported position change per frame that delays the detected position change per frame by a predetermined number of pixels;

wherein the first position change per frame is the reported position change per frame.

28. The method of claim 27, further comprising identifying the reported position change per frame as an actionable position change per frame if an event flag is set.

29. The method of claim 28, further comprising setting the event flag if the reported position change per frame is not from a detected hover event.

30. The method of claim 28, further comprising setting the event flag if the suppressed position change per frame is non-zero.

31. A computer-readable medium comprising program code for suppressing position change in a detected image of touch to assist in distinguishing tapping motions from sliding motions on a touch sensor panel, the program code for causing performance of a method comprising:

computing a time instability factor in accordance with a time instability function that provides a first amount of suppressed position change per frame for a given time since the image of touch was detected;

subtracting the first amount of suppressed position change per frame from a first position change per frame value for the detected image of touch to obtain a suppressed position change per frame for the detected image of touch; and

utilizing the suppressed position change per frame for the detected image of touch to assist in distinguishing tapping motions from sliding motions on the touch sensor panel.

32. The computer-readable medium of claim 31, the time instability function starting at a maximum suppressed position change per frame value at a time when the image if touch is first detected and tapering off to a minimum suppressed position change per frame value for a time greater than or equal to a predetermined delay after the image of touch was first detected.

33. The computer-readable medium of claim 31, wherein the first amount of position change per frame is a detected position change per frame.

34. The computer-readable medium of claim 31, the program code further for causing performance of a method comprising:

applying a hysteresis filter to a detected position change per frame to generate a reported position change per frame that delays the detected position change per frame by a predetermined number of pixels;

wherein the first position change per frame is the reported position change per frame.

35. The computer-readable medium of claim 34, the program code further for causing performance of a method comprising identifying the reported position change per frame as an actionable position change per frame if an event flag is set.

36. The computer-readable medium of claim 35, the program code further for causing performance of a method comprising setting the event flag if the reported position change per frame is not from a detected hover event.

37. The computer-readable medium of claim 35, the program code further for causing performance of a method comprising setting the event flag if the suppressed position change per frame is non-zero.

38. A computer-readable medium comprising program code for suppressing position change in a detected image of touch to assist in distinguishing tapping motions from sliding motions on a touch sensor panel, the program code for causing performance of a method comprising:

computing a touch instability factor in accordance with a touch instability function that provides a first amount of suppressed position change per frame for a given amount of touch instability per frame;

subtracting the first amount of suppressed position change per frame from a first position change per frame value for the detected image of touch to obtain a suppressed position change per frame for the detected image of touch; and

utilizing the suppressed position change per frame for the detected image of touch to assist in distinguishing tapping motions from sliding motions on the touch sensor panel.

39. The computer-readable medium of claim 38, the touch instability function starting at a minimum suppressed position change per frame value at zero percentage change in touch instability per frame and reaching a maximum suppressed position change per frame value for percentage changes in touch instability per frame greater than or equal to a predetermined percentage.

40. The computer-readable medium of claim 38, wherein the first amount of position change per frame is a detected position change per frame.

41. The computer-readable medium of claim 38, the program code further for causing performance of a method comprising:

applying a hysteresis filter to a detected position change per frame to generate a reported position change per frame that delays the detected position change per frame by a predetermined number of pixels;

wherein the first position change per frame is the reported position change per frame.

42. The computer-readable medium of claim 41, the program code further for causing performance of a method comprising identifying the reported position change per frame as an actionable position change per frame if an event flag is set.

43. The computer-readable medium of claim 42, the program code further for causing performance of a method comprising setting the event flag if the reported position change per frame is not from a detected hover event.

44. The computer-readable medium of claim 42, the program code further for causing performance of a method comprising setting the event flag if the suppressed position change per frame is non-zero.

45. A computer-readable medium comprising program code for suppressing position change in a detected image of touch to assist in distinguishing tapping motions from sliding motions on a touch sensor panel, the program code for causing performance of a method comprising:

computing a time instability factor in accordance with a time instability function that provides a first amount of suppressed position change per frame for a given time since the image of touch was detected;

computing a touch instability factor in accordance with a touch instability function that provides a second amount of suppressed position change per frame for a given amount of touch instability per frame;

subtracting a larger of the first and second amount of suppressed position change per frame from a first position change per frame value for the detected image of touch to obtain a suppressed position change per frame for the detected image of touch; and

utilizing the suppressed position change per frame for the detected image of touch to assist in distinguishing tapping motions from sliding motions on the touch sensor panel.

46. The computer-readable medium of claim 45, the time instability function starting at a maximum suppressed position change per frame value at a time when the image if touch is first detected and tapering off to a minimum suppressed position change per frame value for a time greater than or equal to a predetermined delay after the image of touch was first detected.

47. The computer-readable medium of claim 45, the touch instability function starting at a minimum suppressed position change per frame value at zero percentage change in touch instability per frame and reaching a maximum suppressed position change per frame value for percentage changes in touch instability per frame greater than or equal to a predetermined percentage.

48. The computer-readable medium of claim 45, wherein the first position change per frame is a detected position change per frame.

49. The computer-readable medium of claim 45, the program code further for causing performance of a method comprising:

applying a hysteresis filter to a detected position change per frame to generate a reported position change per frame that delays the detected position change per frame by a predetermined number of pixels;

wherein the first position change per frame is the reported position change per frame.

50. The computer-readable medium of claim 49, the program code further for causing performance of a method comprising identifying the reported position change per frame as an actionable position change per frame if an event flag is set.

51. The computer-readable medium of claim 50, the program code further for causing performance of a method comprising setting the event flag if the reported position change per frame is not from a detected hover event.

52. The computer-readable medium of claim 50, the program code further for causing performance of a method comprising setting the event flag if the suppressed position change per frame is non-zero.

53. A computing system comprising the computer-readable medium of claim 45.

54. A mobile telephone comprising the computing system of claim 53.

55. A digital audio player comprising the computing system of claim 53.

56. A mobile telephone including a computer-readable medium comprising program code for suppressing position change in a detected image of touch to assist in distinguishing tapping motions from sliding motions on a touch sensor panel, the program code for causing performance of a method comprising:

computing a time instability factor in accordance with a time instability function that provides a first amount of suppressed position change per frame for a given time since the image of touch was detected;

computing a touch instability factor in accordance with a touch instability function that provides a second amount of suppressed position change per frame for a given amount of touch instability per frame;

subtracting a larger of the first and second amount of suppressed position change per frame from a first position change per frame value for the detected image of touch to obtain a suppressed position change per frame for the detected image of touch; and

utilizing the suppressed position change per frame for the detected image of touch to assist in distinguishing tapping motions from sliding motions on the touch sensor panel.

57. A digital audio player including a computer-readable medium comprising program code for suppressing position change in a detected image of touch to assist in distinguishing tapping motions from sliding motions on a touch sensor panel, the program code for causing performance of a method comprising:

computing a time instability factor in accordance with a time instability function that provides a first amount of suppressed position change per frame for a given time since the image of touch was detected;

computing a touch instability factor in accordance with a touch instability function that provides a second amount of suppressed position change per frame for a given amount of touch instability per frame;

subtracting a larger of the first and second amount of suppressed position change per frame from a first position change per frame value for the detected image of touch to obtain a suppressed position change per frame for the detected image of touch; and

utilizing the suppressed position change per frame for the detected image of touch to assist in distinguishing tapping motions from sliding motions on the touch sensor panel.

58. An apparatus for suppressing position change in a detected image of touch to assist in distinguishing tapping motions from sliding motions on a touch sensor panel, comprising:

means for computing a time instability factor in accordance with a time instability function that provides a first amount of suppressed position change per frame for a given time since the image of touch was detected;

means for computing a touch instability factor in accordance with a touch instability function that provides a second amount of suppressed position change per frame for a given amount of touch instability per frame, wherein Z represents a total finger signal for the detected image of touch;

means for subtracting a larger of the first and second amount of suppressed position change per frame from a first position change per frame value for the detected image of touch to obtain a suppressed position change per frame for the detected image of touch; and

utilizing the suppressed position change per frame for the detected image of touch to assist in distinguishing tapping motions from sliding motions on the touch sensor panel.

59. A computer-readable medium comprising program code for suppressing position change in a detected image of touch to assist in distinguishing tapping motions from sliding motions on a touch sensor panel, the program code for causing performance of a method comprising:

computing a time instability factor in accordance with a time instability function that provides a first amount of suppressed position change per frame immediately after the image of touch is detected to account for position changes during touchdown, and tapering off thereafter;

computing a touch instability factor in accordance with a touch instability function that provides a second amount of suppressed position change per frame for large amounts of touch instability per frame to account for position changes during touchdown and liftoff;

subtracting a larger of the first and second amount of suppressed position change per frame from a first position change per frame value for the detected image of touch to obtain a suppressed position change per frame for the detected image of touch; and

utilizing the suppressed position change per frame for the detected image of touch to assist in distinguishing tapping motions from sliding motions on the touch sensor panel.

60. The computer-readable medium of claim 59, the time instability function starting at a maximum suppressed position change per frame value at a time when the image if touch is first detected and tapering off to a minimum suppressed position change per frame value for a time greater than or equal to a predetermined delay after the image of touch was first detected.

61. The computer-readable medium of claim 59, the touch instability function starting at a minimum suppressed position change per frame value at zero percentage change in touch instability per frame and reaching a maximum suppressed position change per frame value for percentage changes in touch instability per frame greater than or equal to a predetermined percentage.

62. The computer-readable medium of claim 59, wherein the first position change per frame is a detected position change per frame.

63. The computer-readable medium of claim 59, the program code further for causing performance of a method comprising:

applying a hysteresis filter to a detected position change per frame to generate a reported position change per frame that delays the detected position change per frame by a predetermined number of pixels;

wherein the first position change per frame is the reported position change per frame.

64. The computer-readable medium of claim 63, the program code further for causing performance of a method comprising identifying the reported position change per frame as an actionable position change per frame if an event flag is set.

65. The computer-readable medium of claim 64, the program code further for causing performance of a method comprising setting the event flag if the reported position change per frame is not from a detected hover event.

66. The computer-readable medium of claim 64, the program code further for causing performance of a method comprising setting the event flag if the suppressed position change per frame is non-zero.