Methods and systems for detecting a position-based attribute of an object using digital codes

• US 7,868,874 B2
• Filed: 11/15/2005
• Issued: 01/11/2011
• Est. Priority Date: 11/15/2005
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Reynolds, J. Kurth
• Primary Examiner(s): Nguyen; Kevin M
• Application Number:
  US11/274,999
• Publication Number:
  US 20070109274A1
• Time in Patent Office: 1,883 Days
• Field of Search: 345/173
• US Class Current: 345/173
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
• CPC Class Codes: G06F 3/0416 Control or interface arrangements specially adapted for digitisers
• CPC Class Codes: G06F 3/04182 Filtering of noise external to the device and not generated by digitiser components
• CPC Class Codes: G06F 3/04186 Touch location disambiguation
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: H03K 17/962 Capacitive touch switches

Abstract

Methods, systems and devices are described for detecting a position-based attribute of a finger, stylus or other object with a touchpad or other sensor having a touch-sensitive region that includes a plurality of electrodes. Modulation signals for one or more electrodes are produced as a function of any number of distinct digital codes. The modulation signals are applied to an associated at least one of the plurality of electrodes to obtain a resultant signal that is electrically affected by the position of the object. The resultant signal is demodulated using the plurality of distinct digital codes to discriminate electrical effects produced by the object. The position-based attribute of the object is then determined with respect to the plurality of electrodes from the electrical effects.

Claims

1. A method of detecting a position of a pointer with respect to a touch-sensitive region comprising a plurality of electrodes, the method comprising the steps of:

simultaneously applying a first one of a plurality of distinct modulation signals to an associated first one of the plurality of electrodes and a second one of the plurality of distinct modulation signals to an associated second one of the plurality of electrodes to obtain a resultant signal that is electrically affected by the position of the pointer, wherein each of the plurality of distinct modulation signals is based on a different one of a plurality of distinct digital codes;

demodulating the resultant signal using the plurality of distinct digital codes to thereby discriminate electrical effects produced by the pointer; and

determining the position of the pointer with respect to the plurality of electrodes from the electrical effects.

2. The method of claim 1 wherein the determining step comprises determining the position of the pointer with respect to the plurality of electrodes based upon a peak value of the electrical effects.

3. The method of claim 1 wherein the determining step comprises determining the position of the pointer with respect to the plurality of electrodes based upon a computed centroid of the electrical effects.

4. The method of claim 1 wherein the determining step comprises determining a difference between the electrical effects associated with at least two electrodes.

5. The method of claim 1 wherein the determining step comprises comparing the electrical effects to previously-determined baseline effects.

6. The method of claim 1 wherein determining comprises determining the position of the pointer as the pointer moves with respect to the touch sensitive region.

7. The method of claim 1 further comprising providing an output based upon the position that describes a motion of the pointer with respect to the plurality of electrodes.

8. The method of claim 1 further comprising providing an output based upon the position that describes a change in the position from a previous position.

9. The method of claim 1 further comprising providing an output based upon the position that describes a velocity of the pointer.

10. The method of claim 1 further comprising providing an output based upon the position that describes an acceleration of the pointer.

11. The method of claim 1 wherein each of the plurality of distinct digital codes is substantially orthogonal to the remainder of the plurality of distinct digital codes.

12. The method of claim 1 wherein each of the plurality of distinct digital codes is a substantial portion of a code derived from a maximum length shift register sequence.

13. The method of claim 1 wherein at least some of the plurality of distinct digital codes are selected to avoid the effects of noise in the resultant signal.

14. The method of claim 1 further comprising the step of generating each of the plurality of distinct digital codes.

15. The method of claim 14 wherein the generating step comprises producing the plurality of distinct digital codes using at least one shift register.

16. The method of claim 1 wherein the applying step comprises applying a same one of the plurality of distinct modulation signals substantially simultaneously to at least two of the plurality of electrodes.

17. The method of claim 1 wherein the demodulating step comprises receiving signals from at least two of the plurality of electrodes on a common signal path as the resultant signal.

18. The method of claim 1 wherein the electrical effects result from an electrical coupling between the pointer and at least some of the associated electrodes.

19. The method of claim 18 wherein the electrical coupling is a capacitive coupling.

20. The method of claim 18 wherein the resultant signal is received as electrical effects obtained from an integrating capacitor coupled to at least two of the plurality of electrodes.

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

applying a plurality of complementary modulation signals to at least one of the associated first one of the plurality of electrodes and the associated second one of the plurality of electrodes to obtain a plurality of complementary sensed signals, the plurality of complementary modulation signals based on complements of the plurality of distinct digital codes.

22. The method of claim 21 further comprising the steps of:

demodulating each of the plurality of complementary sensed signals using the distinct digital code associated with the at least one of the associated first one of the plurality of electrodes and the associated second one of the plurality of electrodes to thereby identify complementary electrical effects from the plurality of electrodes; and

comparing the electrical effects with the complementary electrical effects to thereby perform dual differential conversion.

23. The method of claim 1 further comprising the step of adjusting at least one of the distinct digital codes in response to the resultant signals.

24. The method of claim 1 further comprising the step of adjusting at least one of the distinct modulation signals in response to the resultant signal.

25. The method of claim 1 further comprising the step of processing the resultant signal to determine a second position of a second pointer in proximity to the touch-sensitive region that is independent of the pointer.

26. The method of claim 25 wherein the pointer and the second pointer are separate parts of a human hand.

27. The method of claim 25 further comprising the step of rejecting information relating to the second pointer.

28. The method of claim 1 wherein the determining step comprises defining an image of the pointer.

29. The method of claim 28 wherein the image represents a two-dimensional topography of the pointer projected upon the touch-sensitive region.

30. The method of claim 28 further comprising the step of processing the resultant signal to determine a position of a second pointer in proximity to the touch-sensitive region, the second pointer being independent of the pointer and having a second image.

31. The method of claim 30 further comprising the step of tracking movements of the pointer and of the second pointer with respect to the touch-sensitive region.

32. The method of claim 30 further comprising the step of determining whether the second pointer represents an undesired input, and if so, rejecting the second pointer.

33. The method of claim 1 wherein the distinct digital codes have more than two states.

34. The method of claim 1 wherein the applying step comprises amplitude modulating a carrier signal with each of the plurality of distinct digital codes.

35. The method of claim 1 wherein the plurality of electrodes comprises a first plurality of electrodes having a first orientation and a second plurality of electrodes having a second orientation.

36. The method of claim 35 wherein each of the plurality of distinct modulation signals is applied to the first plurality of electrodes and received via the second plurality of electrodes.

37. The method of claim 35 further comprising the step of applying a guard signal to at least one inactive electrode of the second plurality of electrodes.

38. The method of claim 1 wherein the applying step comprises applying a same one of the plurality of distinct modulation signals to at least two of the plurality of electrodes.

58. The method of claim 1 wherein the resultant signal is directly affected by the position of the pointer.

59. The method of claim 1 wherein the pointer is a finger.

60. The method of claim 1 wherein the pointer is a stylus.

61. The method of claim 1 wherein the electrodes are substantially rigidly fixed in position with respect to each other.

66. The method of claim 1 wherein each of the plurality of distinct digital codes is strictly orthogonal to the other digital codes.

39. A touch-sensitive device for detecting a position of a pointer, the device comprising:

a touch-sensitive region comprising a plurality of electrodes having electrical characteristics configured to be affected by the proximity of the pointer;

circuitry associated with each of the electrodes;

a demodulator coupled to the touch-sensitive region; and

a processor coupled to the circuitry and to the demodulator, wherein the processor is configured to initiate production of a plurality of distinct modulation signals, wherein each of the plurality of distinct modulation signals is produced as a function of a different one of a plurality of distinct digital codes, to initiate simultaneous application of a first one of the plurality of distinct modulation signals to a first one of the plurality of electrodes and a second one of the plurality of distinct modulation signals to a second one of the plurality of electrodes via the circuitry, to demodulate a sensed signal received from the touch-sensitive region using the distinct digital codes to discriminate electrical effects produced by the pointer upon at least one electrode, and to determine the position of the pointer with respect to the plurality of electrodes using the electrical effects.

40. The device of claim 39 wherein the circuitry comprises an analog signal generator configured to generate a carrier signal and a modulator configured to amplitude modulate the carrier signal with each of the plurality of distinct digital codes to thereby produce the distinct modulation signals.

41. The device of claim 39 wherein the touch sensitive device further comprises a substantially rigid surface configured to provide tactile feedback to the user.

42. The device of claim 41 wherein the substantially rigid surface is further configured to provide the tactile feedback without substantially affecting the electrical effects.

43. The device of claim 41 wherein the substantially rigid surface is further configured to provide the tactile feedback without substantially affecting the positions of the plurality of electrodes relative to each other.

44. The device of claim 39 wherein presence of the pointer to the touch-sensitive region reduces electrical coupling between at least two of the plurality of electrodes.

45. The device of claim 44 wherein the at least two of the plurality of electrodes comprise a first electrode having a first orientation and a second electrode having a second orientation substantially perpendicular to the first orientation.

46. The device of claim 39 further comprising a capacitor electrically coupled to at least some of the plurality of electrodes and to the demodulator.

47. The device of claim 46 wherein the capacitor is configured to integrate charge received from the at least some of the plurality of electrodes.

48. The device of claim 39 wherein the pointer is a finger.

49. The device of claim 39 wherein the pointer is a stylus.

50. The device of claim 39 wherein the electrodes are formed on a flexible substrate.

62. The device of claim 39 wherein the electrodes are substantially rigidly fixed in position with respect to each other.

63. The device of claim 39 wherein the resultant signal is directly affected by the position of the pointer.

64. The device of claim 39 wherein the processor is further configured to determine a second position of an independent second pointer that is in proximity to the touch-sensitive region, wherein the second position is determined from the electrical effects.

65. The device of claim 39 wherein the processor is further configured to determine the position of the pointer as the pointer moves with respect to the touch sensitive region.

67. The device of claim 39 wherein each of the plurality of distinct digital codes is strictly orthogonal to the other digital codes.

51. A device for detecting a position of a pointer with respect to a touch-sensitive region comprising a plurality of electrodes, the device comprising:

means for simultaneously applying a first one of a plurality of distinct modulation signals to an associated first one of the plurality of electrodes and a second one of the plurality of distinct modulation signals to an associated second one of the plurality of electrodes to obtain a resultant signal that is electrically affected by the position of the pointer, wherein each of the plurality of distinct modulation signals is based on a different one of a plurality of distinct digital codes;

means for demodulating the resultant signal using the plurality of distinct digital codes to thereby discriminate electrical effects produced by the pointer; and

means for determining the position of the pointer with respect to the plurality of electrodes from the electrical effects.

52. The device of claim 51 wherein the means for determining is configured to determine the position of the pointer as the pointer moves with respect to the touch sensitive region.

53. The device of claim 51 wherein the resultant signal is directly affected by the position of the pointer.

54. The device of claim 51 wherein the pointer is a finger.

55. The device of claim 51 wherein the pointer is a stylus.

56. The device of claim 51 wherein the electrodes are substantially rigidly fixed in position with respect to each other.

57. The device of claim 51 wherein the determining means is further configured to determine a second position of an independent second pointer that is in proximity to the touch-sensitive region, wherein the second position is determined from the electrical effects.

68. The device of claim 51 wherein each of the plurality of distinct digital codes is strictly orthogonal to the other digital codes.