CALIBRATION FOR PRESSURE EFFECTS ON TOUCH SENSOR PANELS

• US 20130234977A1
• Filed: 06/06/2012
• Published: 09/12/2013
• Est. Priority Date: 03/06/2012
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Albert Lin
• Inventors: LIN, Albert, Kwon, Joon Heup
• Granted Patent: US 9,459,738 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 touch sensor panel which has been calibrated to be insensitive to effects from an external force applied to the panel is provided. Touch sense circuitry settings are adjusted during a calibration procedure so that when a force is exerted on the device, no change in the touch signal DC level is seen. In this way, the ability of the touch sensor panel to detect touch or proximity events is not affected by a force being applied to the panel.

Claims

1. A method for calibrating a touch sensor panel, comprising:

with a force applied to the touch sensor panel, varying a parameter of touch sensor panel drive or sense circuitry associated with at least one touch node of the panel and capturing a range of first output values of the sense circuitry;

with no force applied to the touch sensor panel, varying the parameter of the touch sensor panel drive or sense circuitry associated with the at least one touch node and capturing a range of second output values of the sense circuitry; and

selecting a particular value of the parameter of the touch sensor panel drive or sense circuitry that improves a performance metric that is a function of the first and second output values.

2. The method of claim 1, wherein selecting the particular value of the parameter includes substantially minimizing a difference between the first and second outputs.

3. The method of claim 1, further comprising selecting the particular value of the parameter for which the first and second output values are substantially the same.

4. The method of claim 1, wherein the parameter is a phase of the sense circuitry, and the particular value is an optimum phase.

5. The method of claim 4, wherein the phase of the sense circuitry is varied by adjusting a phase of a local oscillator of the sense circuitry.

6. The method of claim 5, wherein:

with the force applied to the touch sensor panel, varying the parameter for a plurality of nodes while capturing corresponding ranges of the first output values;

with no force applied to the touch sensor panel, varying the parameter for the plurality of nodes while capturing corresponding ranges of the second output values;

selecting optimum phases of the sense circuitry that substantially minimizes a difference between the first and second output values for each node;

wherein the plurality of touch nodes share a common local oscillator and wherein the phase of the common local oscillator is set to a value based on the selected optimum phases of the plurality of touch nodes sharing the common local oscillator.

7. The method of claim 6 wherein the phase of the local oscillator is set to a value such that an error between the set value and the optimum phases of the plurality of touch nodes is minimized.

8. The method of claim 1 wherein the force is applied to the touch sensor panel by at least one non-conductive probe.

9. The method of claim 1 wherein the force is applied to the touch sensor panel by a plurality of conductive probes.

10. The method of claim 1, further comprising determining difference between the first and second output values at that particular value and terminating calibrating if the difference is below a pre-determined threshold.

11. An apparatus for calibrating a touch sensor panel of a device, the apparatus comprising:

a processor capable of;

controlling a force actuator that engages one or more probes for making contact with a touch sensor panel

applying signals to drive circuitry and receiving signals from sense circuitry of the touch sensor panel, the drive circuitry operative for applying a stimulation signal to a plurality of drive lines of the touch sensor panel, and the sense circuitry operative to sensing a capacitance coupled to a plurality of sense lines of the touch sensor panel.

12. The apparatus of claim 11, wherein the probes are non-conductive.

13. The apparatus of claim 11, wherein the probes are conductive.

14. The apparatus of claim 11, wherein the processor is further capable of receiving a first data from the sense circuitry when the force actuator applies the force to the surface of the touch sensor panel and a second data from the sense circuitry when the probe does not apply the force to the surface of the touch sensor panel.

15. The apparatus of claim 11, wherein the processor is further capable of adjusting a setting of the touch sensor panel to reduce a difference in performance of the touch sensor panel when the touch sensor panel is operating with the applied force and without the applied force.

16. The apparatus of claim 15, wherein adjusting includes changing a phase of a stimulation signal being applied to the touch sensor panel by the drive circuitry.

17. The apparatus of claim 15, wherein adjusting includes changing a phase of a local oscillator of the sense circuitry of the touch sensor panel.

18. A non-transitory computer readable storage medium having stored thereon a set of instructions for calibrating a touch sensor panel, that when executed by a processor causes the processor to:

engage one or more actuators for applying a force to a surface of the touch sensor panel using one or more non-conductive probes;

with a force applied to the touch sensor panel, vary a parameter of touch sensor panel drive or sense circuitry and capturing a range of first output values of the sense circuitry;

disengage the actuator in order to remove the force from the touch sensor panel;

with no force applied to the touch sensor panel, vary the parameter of the touch sensor panel drive or sense circuitry and capturing a range of second output values of the sense circuitry; and

select a particular value of the parameter of the touch sensor panel drive or sense circuitry that reduces a difference between the first and second output values at that particular value.

19. The non-transitory computer readable storage medium of claim 18, wherein the setting of the touch sensor panel includes setting a phase of a stimulation signal used to drive the touch sensor panel.

20. The non-transitory computer readable storage medium of claim 18, wherein the parameter is a phase of the sense circuitry and the processor is further caused to select an optimum phase that represents the phase of the sense circuitry for which the first and second output values are substantially the same.

21. The non-transitory computer readable storage medium of claim 18, wherein the phase of the sense circuitry is set by adjusting a phase of local oscillator of the sense circuitry.

22. The non-transitory computer readable storage medium of claim 21, wherein a plurality of touch nodes share a common local oscillator and wherein the phase of the local oscillator is set to a particular value based on the optimum phases of the plurality of touch nodes sharing a common local oscillator.

23. The non-transitory computer readable storage medium of claim 22, wherein the phase of the local oscillator is set to a value such that an error between the set value and the optimum phases of the plurality of touch nodes is minimized.

24. The non-transitory computer readable storage medium of claim 18, wherein the processor is further caused to determine the difference between the first and second output values at that particular value and terminate the calibration if the difference is below a pre-determined threshold.

25. A method for calibrating a touch sensor panel, comprising:

with a force applied to the touch sensor panel, varying a parameter of touch sensor panel drive or sense circuitry of the panel and capturing a range of first output values of the sense circuitry;

with no force applied to the touch sensor panel, varying the parameter of the touch sensor panel drive or sense circuitry and capturing a range of second output values of the sense circuitry; and

selecting a particular value of the parameter of the touch sensor panel drive or sense circuitry that improves a performance metric that is a function of the first and second output values.

26. A touch sensor panel calibrated in accordance with claim 25.