System and method for calibration of a capacitive touch digitizer system

• US 20080170046A1
• Filed: 01/16/2008
• Published: 07/17/2008
• Est. Priority Date: 01/16/2007
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: N-Trig Ltd (Microsoft Corporation)
• Inventors: Birnboim, Michael, Rimon, Ori, Kerner, Ariel
• Granted Patent: US 8,866,789 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

A method for calibration of a capacitive touch digitizer system comprises detecting patterns of signals from a plurality of different events over a course of user interaction with the digitizer system, wherein the patterns of signals are outputs from a digitizer sensor of the system, determining a number of times that a pattern of signals is repeated over the different events, and defining a map of offset values as a pattern of signals that is repeated above a pre-defined repetition threshold.

Claims

1. A method for calibration of a capacitive touch digitizer system, the method comprising:

detecting patterns of signals from a plurality of different events over a course of user interaction with the digitizer system, wherein the patterns of signals are outputs from a digitizer sensor of the system;

determining a number of times that a pattern of signals is repeated over the different events; and

defining a map of offset values as a pattern of signals that is repeated above a pre-defined repetition threshold.

2. The method according to claim. 1 wherein the defining a map of offset values is performed automatically without user intervention for invoking the defining.

3. The method according to claim 1 comprising identifying an onset of a new event and selecting a representative pattern of signals from the new event.

4. The method according to claim 3 wherein the new event is detected in response to a change in at least one digitizer sensor output by a magnitude above a pre-defined event threshold.

5. The method according to claim 3 wherein the representative pattern of signals is the first pattern of signals sampled during the event.

6. The method according to claim 3 wherein the representative pattern of signals is an average of a plurality of patterns of signals sampled during the event.

7. The method according to claim 1 wherein the different events include different lift and touch events, wherein the touch events are periods during which a user interaction invokes signals on the digitizer sensor, and wherein the lift events are periods over which the object for user interaction is away from the digitizer sensor such that the object does not invoke signals on the digitizer sensor.

8. The method according to claim 7 wherein the object for user interaction is a finger.

9. The method according to claim 1 comprising:

determining stability of the events, wherein stability is determined for an event that includes a pre-defined number of samples with a consistent pattern of signals; and

excluding events that are not stable from consideration for determining the number of times that the pattern of signals is repeated over the different events.

10. The method according to claim 1 comprising:

detecting a drag event, wherein a drag event is a period over which an object is dragged along the digitizer sensor; and

excluding drag events from consideration when determining the number of times that the pattern of signals is repeated over the different events.

11. The method according to claim 10 comprising:

calculating delta patterns, wherein a delta pattern is the difference between a previous pattern of signals and a current pattern of signals;

determining if the delta pattern depicts a drag event; and

defining the previous and the current pattern of signals as patterns of signals derived from a drag event.

12. The method according to claim 11 wherein the drag event includes outputs with a common sign in a first area on the digitizer sensor and outputs with an opposite sign in a second area adjacent to the first area on the digitizer sensor.

13. The method according to claim 1 wherein the offset values are implemented to calibrate readings of digitizer sensor outputs.

14. The method according to claim 1 comprising:

saving at least one map of offset values in non-volatile memory.

15. The method according to claim 1 comprising saving at least one map of offset values, wherein the map is determined from a manually initiated calibration procedure.

16. The method according to claim 1 comprising saving at least one map of offset values, wherein the map is determined from a previous calibration procedure.

17. The method according to claim 1 comprising updating the map of offset values in response to detection of repetitive patterns of signals that are different than the pattern of signals implemented to define the map.

18. The method according to claim 1 comprising recording at least one of the patterns of signals detected from the plurality of different events in a repetition table.

19. The method according to claim 18 comprising comparing detected patterns of signals to patterns of signals stored in the repetition table.

20. The method according to claim 1 comprising storing a pattern of signals that is repeated at least once in a candidate table.

21. The method according to claim 20 comprising selecting the pattern of signals to be implemented as a map of the offset values from patterns of signals stored in the candidate table.

22. The method according to claim 1 comprising adjusting the pattern of signals implemented as a map of offsets to slow changes detected in the same event.

23. The method according to claim 1 wherein the pattern of signals includes outputs from a plurality of conductive lines of the digitizer sensor arranged in a grid.

24. The method according to claim 1 wherein the outputs from the digitizer sensor are outputs form differential amplifiers of the digitizer sensor.

25. The method according to claim 23 wherein the outputs from the digitizer sensor are outputs from sensor junctions.

26. The method according to claim 1 wherein the pattern of signals forms a two dimensional image.

27. The method according to claim 1 wherein the pattern of signals forms a one dimensional image on each axis of the digitizer sensor.

28. A capacitive touch digitizer system comprising:

a digitizer configured for detecting a presence of an object over a digitizer sensor;

a zero-state detector configured for;

detecting patterns of signals from a plurality of different events over the course of user interaction with the digitizer, wherein the patterns of signals are outputs from the digitizer;

determining a number of times that a pattern of signals is repeated over the different events; and

defining a map of offset values as a pattern of signals that is repeated above a pre-defined repetition threshold.

29. The system according to claim 28 wherein the zero-state detector is configured for defining the map of offset values automatically without user intervention for invoking the defining.

30. The system according to claim 28 wherein the zero-state detector is configured for identifying an onset of a new event and selecting a representative pattern of signals from the new event.

31. The system according to claim 30 wherein the zero-state detector is configured to detect the new event in response to a change in at least one digitizer sensor output by a magnitude above a pre-defined event threshold.

32. The system according to claim 30 wherein the representative pattern of signals is the first pattern of signals sampled during the event.

33. The system according to claim 30 wherein the representative pattern of signals is an average of a plurality of patterns of signals sampled during the event.

34. The system according to claim 28 wherein the different events include different lift and touch events, wherein the touch events are periods during which an object invokes signals on the digitizer, and wherein the lift events are periods over which the object is away from the digitizer sensor such that the object does not invoke signals on the digitizer.

35. The system according to claim 28 wherein the zero-state detector is configured for determining stability of the events, wherein stability is determined for an event that includes a pre-defined number of samples with a consistent pattern of signals;

and for excluding events that are not stable from consideration for determining the number of times that the pattern of signals is repeated over the different events.

36. The system according to claim 28 wherein the zero-state detector is configured for:

detecting a drag event, wherein a drag event is a period over which an object is dragged along the digitizer sensor; and

excluding drag events from consideration when determining the number of times that the pattern of signals is repeated over the different events.

37. The system according to claim 36 wherein the zero-state detector is configured for:

calculating delta patterns, wherein a delta pattern is the difference between a previous pattern of signals and a current pattern of signals; and

determining if the delta pattern depicts a drag event; and

defining the previous and the current pattern of signals as patterns of signals derived from a drag event.

38. The system according to claim 37 wherein the drag event includes outputs with a common sign in a first area on the digitizer sensor and outputs with an opposite sign in a second area adjacent to the first area on the digitizer sensor.

39. The system according to claim 28 comprising a compensator, wherein the compensator is configured using the offset values for calibrating readings of digitizer sensor outputs.

40. The system according to claim 28 comprising a non-volatile memory configured for storing at least one map of offset values.

41. The system according to claim 40 wherein the at least one map of offset values is a map determined from a manually initiated calibration procedure.

42. The system according to claim 40 wherein the at least one map of offset values is a map determined from a previous calibration procedure.

43. The system according to claim 28 wherein the zero-state detector is configured for updating the map of offset values in response to detection of repetitive patterns of signals that are different than the pattern of signals implemented to define the map.

44. The system according to claim 28 wherein the zero-state detector is configured for recording at least one of the patterns of signals detected from the plurality of different events in a repetition table.

45. The system according to claim 44 comprising memory for storing the repetition table.

46. The system according to claim 45 wherein the memory is volatile memory.

47. The system according to claim 44 wherein the zero-state detector is configured for comparing detected patterns of signals to patterns of signals stored in the repetition table.

48. The system according to claim 28 comprising memory configured for storing a pattern of signals that is repeated at least once in a candidate table.

49. The system according to claim 48 comprising memory configured for storing the candidate table.

50. The system according to claim 49 wherein the memory is volatile memory.

51. The system according to claim 48 wherein the zero-state detector is configured for selecting the pattern of signals to be implemented as a map of the offset values from patterns of signals stored in the candidate table.

52. The system according to claim 28 wherein the zero-state detector is configured for adjusting the pattern of signals implemented as a map of offsets to slow changes detected in the same event.

53. The system according to claim 28 wherein the digitizer includes a plurality of conductive lines of the digitizer arranged in a grid;

and wherein the pattern of signals includes outputs from the plurality of conductive lines of the grid.

54. The system according to claim 28 wherein pairs of the conductive lines are coupled to a differential amplifier through which a difference signal is detected and wherein the outputs from the digitizer are outputs form differential amplifiers.

55. The system according to claim 53 wherein the outputs from the digitizer are outputs from junctions of conductive lines of the digitizer.

56. The system according to claim 28 wherein the object is a finger.

57. The system according to claim 28 wherein the pattern of signals forms a two dimensional image.

58. The method according to claim 28 wherein the pattern of signals forms a one dimensional image on each axis of the digitizer.

59. A method for detecting a drag event performed on a capacitive touch digitizer system, wherein a drag event is a period over which an object is dragged along the digitizer sensor, the method comprising:

detecting patterns of signals from a plurality of different events over a course of user interaction with the digitizer system, wherein the patterns of signals are outputs from a digitizer sensor of the system;

calculating delta patterns, wherein a delta pattern is the difference between a previous pattern of signals and a current pattern of signals; and

determining if the delta pattern depicts a drag event.

60. The method according to claim 59 comprising identifying an onset of a new event and selecting a representative pattern of signals from the new event.

61. The method according to claim 60 wherein the new event is detected in response to a change in at least one digitizer sensor output by a magnitude above a pre-defined event threshold.

62. The method according to claim 59 wherein the different events include different lift and touch events, wherein the touch events are periods during which a user interaction invokes signals on the digitizer sensor, and wherein the lift events are periods over which the object for user interaction is away from the digitizer sensor such that the object does not invoke signals on the digitizer sensor.

63. The method according to claim 59 wherein the delta patterns depicting drag events includes outputs with a common sign in a first area on the digitizer sensor and outputs with an opposite sign in a second area adjacent to the first area on the digitizer sensor.

64. The method according to claim 59 comprising:

defining the previous and the current pattern of signals as patterns of signals derived from a drag event in the case that the pattern is determined to be a drag event.

65. The method according to claim 59 wherein the object is a finger.

66. The method according to claim 59 wherein the pattern of signals includes outputs from a plurality of conductive lines of the digitizer sensor arranged in a grid.

67. The method according to claim 59 wherein the outputs from the digitizer sensor are outputs form differential amplifiers of the digitizer sensor.

68. The method according to claim 67 wherein the outputs from the digitizer sensor are outputs from sensor junctions.

69. The method according to claim 59 wherein the pattern of signals forms a two dimensional image.

70. The method according to claim 59 wherein the pattern of signals forms a one dimensional image on each axis of the digitizer sensor.