TOUCH DETECTION FOR TOUCH INPUT DEVICES

• US 20100079402A1
• Filed: 09/26/2008
• Published: 04/01/2010
• Est. Priority Date: 09/26/2008
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Grunthaner, Martin Paul, Hotelling, Steve Porter
• Granted Patent: US 8,614,690 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G06F 3/04182 Filtering of noise external to the device and not generated by digitiser components
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes

Abstract

Methods and apparatus for correcting electrical noise coupling from a liquid crystal module to a plurality of sense elements disposed within a touch sensor panel, and for reducing errors in touch detection algorithms. Erroneous signal values detected by the sense elements may be corrected by utilizing a set of reference elements for detecting noise common to both the sense elements and the reference elements, and a correction module for effectively subtracting out the noise from the sensed values. Errors in touch detection algorithms may be reduced by providing a more uniform spacing between successive sense elements. In some embodiments, one or more dummy ground elements may be inserted between adjacent sense elements in order to reduce signal interference.

Claims

1. A touch sensor panel adapted to compensate for received electromagnetic noise, the touch sensor panel comprising:

a plurality of drive elements;

a plurality of sense elements in proximity to one or more of the drive elements and adapted to capacitively couple to one or more of the drive elements and detect touch events; and

one or more reference elements in proximity to one or more of the sense elements, the reference elements adapted for capacitively coupling electromagnetic noise.

2. The touch sensor panel of claim 1, wherein each reference element is dedicated to one or more sense elements.

3. The touch sensor panel of claim 2 further comprising a set of correction modules, wherein each correction module is connected to a respective reference element, and wherein each correction module is adapted to correct for noise in the detected touch events based at least in part upon an output from the respective reference element.

4. The touch sensor panel of claim 3 further comprising a set of scaling modules, wherein each scaling module of the set is connected to a respective reference element, and wherein each scaling module is adapted to scale an output from the respective reference element.

5. The touch sensor panel of claim 1, wherein each reference element is situated between adjacent sense elements.

6. The touch sensor panel of claim 1, wherein each reference element is commonly routed.

7. The touch sensor panel of claim 1 further comprising a first module coupled to the sense and reference elements and adapted to correct for the noise in the detected touch events based at least in part upon an output from the reference elements.

8. The touch sensor panel of claim 7 further comprising a second module adapted to generate an average of the signals detected by each of the reference elements.

9. The touch sensor panel of claim 8 further comprising a third module adapted to scale the average generated by the second module.

10. The touch sensor panel of claim 9, wherein the third module is adapted to scale the average based at least in part upon a size of a sense element relative to a size of a reference element.

11. The touch sensor panel of claim 1, wherein each reference element comprises an area that is a fraction of an area of a sense element.

12. The touch sensor panel of claim 1, wherein the electromagnetic noise comprises common mode noise generated by a liquid crystal display module.

13. The apparatus of claim 1, wherein the centers of touch sensitivity of the drive-sense elements are evenly spaced.

14. A method of compensating for common mode noise in a touch sensor panel comprising a plurality of sense elements, the method comprising:

providing one or more reference elements in a touch sensor panel, the one or more reference elements adapted for sensing the common mode noise;

detecting a set of signals from said reference elements; and

creating a correction value based at least in part upon the set of signals.

15. The method of claim 14, wherein the number of reference elements provided is smaller than the number of sense elements disposed within the touch sensor panel.

16. The method of claim 14, further comprising modulating a sensed touch signal based at least in part upon the correction value.

17. The method of claim 16, wherein said modulating a sensed touch signal based at least in part upon the correction value comprises reducing the value of the sensed touch signal by the correction value.

18. The method of claim 14, wherein the touch sensor panel further comprises a set of drive elements, wherein each of the reference elements is positioned such that the amount of capacitive coupling between a reference element and an associated drive element is smaller than the amount of capacitive coupling between an associated sense element and the associated drive element.

19. The method of claim 14, wherein said creating a correction value based at least in part upon the set of signals comprises creating an average signal value and scaling the average signal value.

20. The method of claim 19, wherein the average signal value is scaled based at least in part upon a size of a sense element relative to a size of a reference element.

21. The method of claim 14, wherein each of the centers of touch sensitivity of the drive-sense elements are evenly spaced using one or more dummy ground conductors between adjacent sense elements.

22. The method of claim 21, wherein each reference element is positioned between two dummy ground conductors.

23. A touch sensor panel adapted to reduce errors in centroid detection, the touch sensor panel comprising:

a plurality of sets of drive elements; and

a sense element in proximity to each set of drive elements,

wherein at least one sense element is adjacent to another sense element, and wherein each of the sense elements are evenly spaced.

24. The touch sensor panel of claim 23, wherein a size of each sense element is based at least in part upon an amount of separation between successive sense elements.

25. The touch sensor panel of claim 23, wherein a size of each sense element is based at least in part upon a desired pixel size.

26. The touch sensor panel of claim 23, wherein said at least one sense element is separated from said another sense element by one or more dummy ground elements.

27. The touch sensor panel of claim 23 further comprising:

one or more reference elements, wherein each of the one or more reference elements is interleaved between adjacent sense elements; and

a correction module adapted to generate a correction for common mode noise, the correction based at least in part upon output from the one or more reference elements.

28. The touch sensor panel of claim 23, the touch sensor panel incorporated within a computing system.

29. A method for forming a touch sensor panel capable of reducing errors in centroid detection, comprising:

arranging a plurality of sense elements in proximity to a plurality of drive elements on the touch sensor panel, the sense elements grouped in pairs and having even spacing with respect to each other; and

forming a reference element between each pair of sense elements.

30. The method of claim 29, further comprising selecting a width for each sense element based at least in part upon a desired amount of separation between sense elements.

31. The method of claim 29, further comprising selecting a width for each sense element based at least in part upon a desired pixel size.

32. The method of claim 29, further comprising separating at least one sense element from said another sense element by one or more dummy ground elements.

33. A mobile telephone including a touch sensor panel adapted to compensate for received electromagnetic noise, the touch sensor panel comprising:

a plurality of drive elements;

a plurality of sense elements in proximity to one or more of the drive elements and adapted to capacitively couple to one or more of the drive elements and detect touch events; and

one or more reference elements in proximity to one or more of the sense elements, the reference elements adapted for capacitively coupling electromagnetic noise.

34. A digital media player including a touch sensor panel adapted to compensate for received electromagnetic noise, the touch sensor panel comprising:

a plurality of drive elements;

a plurality of sense elements in proximity to one or more of the drive elements and adapted to capacitively couple to one or more of the drive elements and detect touch events; and

one or more reference elements in proximity to one or more of the sense elements, the reference elements adapted for capacitively coupling electromagnetic noise.

35. A personal computer including a touch sensor panel adapted to compensate for received electromagnetic noise, the touch sensor panel comprising:

a plurality of drive elements;

a plurality of sense elements in proximity to one or more of the drive elements and adapted to capacitively couple to one or more of the drive elements and detect touch events; and

one or more reference elements in proximity to one or more of the sense elements, the reference elements adapted for capacitively coupling electromagnetic noise.