BACKGROUND CAPACITANCE COMPENSATION FOR A CAPACITIVE TOUCH INPUT DEVICE

• US 20120162123A1
• Filed: 01/25/2011
• Published: 06/28/2012
• Est. Priority Date: 12/22/2010
• Status: Active Grant

• Current Assignee: Elo Touch Solutions, Inc.
• Original Assignee: Elo Touch Solutions, Inc.
• Inventors: Kent, Joel C., Li, Selina, Yi, Jong
• Granted Patent: US 9,152,278 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 3/0443 using a single layer of sensing electrodes

Abstract

A location of contact with a touch sensitive device is determined. Values associated with each electrode of a plurality of electrodes formed on a single layer of the touch sensitive device are sampled. A determination is made as to whether a contact with the touch sensitive device has occurred. Values sampled subsequent to the contact are adjusted based on selected stored sampled values. A location of contact is then determined based on the adjusted values.

Claims

1. A method for determining a location of contact with a touch sensitive device, the method comprising:

sampling a value associated with each electrode of a plurality of electrodes of the touch sensitive device, the touch sensitive device comprising a single electrode layer device;

storing at least some of the sampled values;

determining whether a contact with the touch sensitive device has occurred;

adjusting values sampled subsequent to the contact based on at least some of the stored sample values; and

determining a location of contact based on the adjusted values.

2. The method according to claim 1, further comprising determining whether a rate of change of a value associated with one or more electrodes of the plurality of electrodes exceeds a threshold.

3. The method according to claim 1, further comprising:

determining a rate of change of a value associated with one or more electrodes of the plurality of electrodes; and

selecting the at least some of the stored samples based on the determined rate of change.

4. The method according to claim 1, further comprising ceasing storing of the sampled values after contact with the touch sensitive device has occurred.

5. The method according to claim 4, continuously determining the location of contact based on the at least some of the stored sample values until contact with the touch sensitive device has ceased.

6. The method according to claim 4, further comprising:

determining whether contact with the touch sensitive device has ceased, and

resuming storing of samples after contact with the touch sensitive device has occurred.

7. The method according to claim 1, further comprising subtracting from values sampled subsequent to the contact by the at least some of the stored sample values.

8. The method according to claim 1, wherein the touch sensitive device comprises a transparent surface and the electrodes are arranged on the transparent surface, the touch sensitive device surface is positioned over a display surface, and the location of contact corresponds to a location where a user touches the touch sensitive device.

9. A system for determining a location of contact with a capacitive touch sensitive device, the method comprising:

one or more analog-to-digital converters configured to sample signals at a plurality of electrodes; and

a processor configured to;

store values for at least some of the sampled signals;

determine whether a contact with the touch sensitive device has occurred;

select a background value for each of the electrodes of the plurality based on the stored values;

adjust the values or subsequent values for each of the electrodes by the respective background values; and

determine a location of contact based on the adjusted values.

10. The system according to claim 9, wherein the processor is configured to determine whether a rate of change of a value associated with one or more electrodes of the plurality of electrodes exceeds a threshold.

11. The system according to claim 9, wherein the processor is configured to:

determine a rate of change of a value associated with one or more electrodes of the plurality of electrodes; and

select stored values based on the determined rate of change.

12. The system according to claim 9, wherein the processor is configured to cease storage of the values after contact with the touch sensitive device has occurred.

13. The system according to claim 12, wherein the processor is configured to continuously determine the location of contact based on the stored values until contact with the touch sensitive device has ceased.

14. The system according to claim 12, wherein the processor is configured to:

determine whether contact with the touch sensitive device has ceased, and

resume storage of values after contact with the touch sensitive device has occurred.

15. The system according to claim 9, wherein the processor is configured to subtract from values sampled subsequent to the contact by the stored values.

16. The system according to claim 9, wherein the touch sensitive device comprises a transparent surface and the electrodes are arranged on the transparent surface, the touch sensitive device surface is positioned over a display surface, and the location of contact corresponds to a location where a user touches the touch sensitive device.

17. In a non-transitory computer readable storage medium having stored therein data representing instructions executable by a programmed processor for determining a location of contact with a touch sensitive device, the storage medium comprising instructions for:

identifying background capacitance from prior to a contact with the touch sensitive device;

removing the background capacitance from measurements of a plurality of electrodes;

determining a location of the contact based on the measurements with the background capacitance removed.

18. The non-transitory computer readable storage medium according to claim 17, wherein identifying comprises:

determining a rate of change of values associated with one or more electrodes of the plurality of electrodes; and

selecting the background capacitance based on the determined rate of change.

19. The non-transitory computer readable storage medium according to claim 17, further comprising:

storing values sampled prior to the contact, the background capacitance based on the stored values; and

ceasing storing of the values after contact with the touch sensitive device has occurred.

20. The non-transitory computer readable storage medium according to claim 19, wherein the location of contact is continuously determined based on the removing of the background capacitance until contact with the touch sensitive device has ceased.