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

• US 20070109274A1
• Filed: 11/15/2005
• Published: 05/17/2007
• Est. Priority Date: 11/15/2005
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Reynolds, J.
• Granted Patent: US 7,868,874 B2
• Time in Patent Office: Days
• 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-based attribute of an object with respect to a touch-sensitive region comprising a plurality of electrodes, the method comprising the steps of:

producing a plurality of distinct digital codes used to create a plurality of modulation signals 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;

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

determining the position-based attribute of the object with respect to the plurality of electrodes from the electrical effects.

2. The method of claim 1 wherein the determining step comprises identifying at least one peak value of the electrical effects.

3. The method of claim 1 wherein the determining step comprises computing a centroid of the electrical effects.

4. The method of claim 1 wherein the determining step comprises determining a difference between the electrical effects received from 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 the position-based attribute corresponds to a position of the object with respect to the plurality of electrodes.

7. The method of claim 1 wherein the position-based attribute describes a motion of the object with respect to the plurality of electrodes.

8. The method of claim 1 wherein the position-based attribute describes a change in position from a previous value.

9. The method of claim 1 wherein the position-based attribute describes a velocity of the object.

10. The method of claim 1 wherein the position-based attribute describes an acceleration of the object.

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

12. The method of claim 1 wherein each of the plurality of 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 sensed signals.

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 modulation signals are applied substantially simultaneously for at least two of the plurality of electrodes.

17. The method of claim 1 wherein the demodulating step comprises receiving at least two of the sensing signals from the sensing region on a common signal path.

18. The method of claim 1 wherein the electrical effects result from an electrical coupling between the object 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 electrical effects are obtained from an integrating capacitor coupled to at least two of the plurality of electrodes.

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

producing each of a plurality of complementary modulation signals as a function of complements of the plurality of distinct digital codes; and

applying each of the complementary modulation signals to the associated at least one of the plurality of electrodes to obtain a plurality of complementary sensed signals.

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 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 the distinct digital code subsequently applied to at least one of the plurality of electrodes in response to the plurality of sensed 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 sensed signals.

25. The method of claim 1 further comprising the step of processing the resultant signal to obtain information about a second object in proximity to the touch-sensitive region.

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

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

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

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

30. The method of claim 28 further comprising the step of processing the resultant signal to obtain information about a second object in proximity to the touch-sensitive region, the second object having a second image.

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

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

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

34. The method of claim 1 wherein the step of producing the plurality of unique modulation signals 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 unique modulation signals are 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 at least one of the unique modulation signals to at least two of the plurality of electrodes.

39. A touch-sensitive device for detecting a position-based attribute of an object, the device comprising:

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

drive circuitry associated with each of the electrodes;

a demodulator coupled to the touch-sensitive region; and

a processor coupled to the drive circuitry and to the demodulator, wherein the processor is configured to initiate production of a plurality of modulation signals as a function of a plurality of distinct digital codes, to initiate application of each of the plurality of modulation signals to said plurality of electrodes via the drive circuitry, to demodulate a sensed signal received from said sensing region using the digital codes to discriminate electrical effects produced by the object upon at least one sensing electrode, and to determine the position-based attribute of the object with respect to the plurality of electrodes from the electrical effects.

40. The device of claim 39 wherein the drive 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 unique 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 contact between the object and 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 object is a finger.

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

50. The device of claim 39 wherein the touch-sensitive region is formed on a flexible substrate.

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

means for producing a plurality of distinct digital codes used to create a plurality of modulation signals 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;

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

means for determining the position-based attribute of the object with respect to the plurality of electrodes from the electrical effects.