Touch sensor panel calibration

• US 8,890,854 B2
• Filed: 11/19/2010
• Issued: 11/18/2014
• Est. Priority Date: 08/27/2010
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Tenuta, Matthew D., Bokma, Louis W.
• Primary Examiner(s): Beck, Alexander S
• Assistant Examiner(s): RAYAN, MIHIR K
• Application Number:
  US12/950,981
• Publication Number:
  US 20120050229A1
• Time in Patent Office: 1,460 Days
• Field of Search: 345/178
• US Class Current: 345/178
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• 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

Abstract

A method for calibrating a touch sensor panel including a plurality of touch electrodes is provided. The method includes determining, for each of the plurality of touch electrodes, a contribution in terms of capacitance to a total capacitance of the touch sensor panel; and allocating a fraction of a fixed period of time for measuring a capacitance of each of the plurality of electrodes based on the electrode'"'"'s contribution to the total capacitance.

Claims

1. An apparatus for calibrating a touch sensor panel including a plurality of touch electrodes, the apparatus comprising a processor programmed for:

measuring individual capacitances of each of the touch electrodes by scanning each of the touch electrodes for a same duration;

computing a total capacitance of the touch sensor panel from the individual capacitances;

determining a percentage contribution of each of the plurality of touch electrodes to the total capacitance of the touch sensor panel; and

scanning each touch electrode for a fraction of a touch sensing time period proportional to the percentage contribution of that electrode to the total capacitance of the touch sensor panel.

2. The apparatus of claim 1, wherein the processor is further programmed for scanning one or more of the plurality of electrodes to obtain the capacitance of the electrodes during the respective portion of the touch sensing time period.

3. The apparatus of claim 2, wherein the processor is further programmed for creating a touch image from the obtained capacitance of the electrodes.

4. The apparatus of claim 1, wherein the portion of the touch sensing time comprises a LCM black window.

5. The apparatus of claim 1, wherein the processor is further programmed for applying a fixed set of scan parameters to all of the electrodes of the touch sensor panel to record a baseline measurement of the total capacitance and capacitance of each of the plurality of touch electrodes.

6. The apparatus of claim 1, wherein determining a percentage contribution of each of the plurality of touch electrodes further comprises dividing the capacitance of each of the plurality of electrodes by the total capacitance.

7. A method for calibrating a touch sensor panel including a plurality of touch electrodes, the method comprising:

measuring individual capacitances of each of the touch electrodes by scanning each of the touch electrodes for a same duration;

computing a total capacitance of the touch sensor panel from the individual capacitances;

determining, for each of the plurality of touch electrodes, a contribution in terms of capacitance to the total capacitance of the touch sensor panel; and

scanning each touch electrode for allocating a fraction of a fixed period of time for measuring a capacitance of each of the plurality of electrodes based on, the fixed period of time proportional to the electrode'"'"'s contribution to the total capacitance.

8. The method of claim 7, wherein the fixed period of time comprises a LCM blank window.

9. The method of claim 7, wherein the fraction of the fixed period of time allocated to each of the plurality of electrodes is proportional to the electrode'"'"'s contribution to the total capacitance.

10. The method of claim 7, further comprising selecting a duty cycle for each of the plurality of electrodes of the touch sensor panel.

11. The method of claim 10, further comprising applying a fixed set of scan parameters to all of the electrodes of the touch sensor panel to record a baseline measurement of the total capacitance and capacitance of each of the plurality of electrodes.

12. The method of claim 11, wherein determining, for each of the plurality of touch electrodes, contribution in terms of capacitance to a total capacitance of the touch sensor panel further comprises dividing the capacitance of each of the plurality of electrodes by the total capacitance.

13. The method of claim 7, further comprising scanning one or more of the plurality of electrodes to obtain the capacitance of the electrodes during the respective fraction of the fixed period of time allocated to the electrode.

14. The method of claim 13, further comprising creating a touch image from the obtained capacitance of the electrodes.

15. A non-transitory computer readable storage medium storing instructions executed by a processor for calibrating a touch sensor panel including a plurality of touch electrodes, the instructions comprising:

measuring individual capacitances of each of the touch electrodes by scanning each of the touch electrodes for a same duration;

computing a total capacitance of the touch sensor panel from the individual capacitances;

determining, for each of the plurality of touch electrodes, a contribution in terms of capacitance to the total capacitance of the touch sensor panel; and

scanning each touch electrode for a fraction of a fixed period of time for measuring a capacitance of each of the plurality of electrodes based on, the fixed period of time proportional to the electrode'"'"'s contribution to the total capacitance.

16. The non-transitory computer readable storage medium of claim 15, further comprising selecting a duty cycle for each of the plurality of electrodes of the touch sensor panel.

17. The non-transitory computer readable storage medium of claim 15, further comprising applying a fixed set of scan parameters to all of the electrodes of the touch sensor panel to record a baseline measurement of the total capacitance and capacitance of each of the plurality of electrodes.

18. The non-transitory computer readable storage medium of claim 15, further comprising scanning one or more of the plurality of electrodes to obtain the capacitance of the electrodes during the respective fraction of the fixed period of time allocated to the electrode.

19. The non-transitory computer readable storage medium of claim 18, further comprising creating a touch image from the obtained capacitance of the electrodes.