Capacitive touch systems and methods using differential signal techniques

• US 10,168,825 B2
• Filed: 12/22/2014
• Issued: 01/01/2019
• Est. Priority Date: 01/03/2014
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Geaghan, Bernard O.
• Primary Examiner(s): Amadiz, Rodney
• Application Number:
  US15/107,113
• Publication Number:
  US 20160342265A1
• Time in Patent Office: 1,471 Days
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• 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

An approach for determining touch location on a touch panel includes receiving information indicative of which of the electrodes in the first set of electrodes are not experiencing, or are unlikely to experience, a touch is received. Based on the received information, at least one electrode is selected from the first set of electrodes to function as a first reference electrode, remaining ones of the first set of electrodes referred to as first remaining electrode. Touch signals are measured for at least some of the touch panel nodes using a differential technique. The differential technique for each such node utilizes the first reference electrode in combination with at least one of the first remaining electrodes and with at least one of the electrodes from the second set of electrodes.

Claims

1. A method of determining touches on a touch panel, the touch panel comprising a plurality of electrodes arranged in an electrode matrix comprising a first set of electrodes capacitively coupled to a second set of electrodes at an array of nodes defining an active touch-sensitive area of the touch panel, the method comprising:

receiving information indicative of which of the electrodes in the first set of electrodes are not experiencing, or are unlikely to experience, a touch;

selecting, based on the received information, at least one electrode from the first set of electrodes that are not experiencing, or are unlikely to experience, a touch to function as a first reference electrode, remaining ones of the first set of electrodes referred to as first remaining electrodes; and

measuring touch signals for at least some of the nodes using a differential technique, the differential technique for each such node utilizing the first reference electrode in combination with at least one of the first remaining electrodes and with at least one of the electrodes from the second set of electrodes.

2. The method of claim 1, wherein the differential technique comprises a differential drive technique in which a first drive signal is coupled to the first reference electrode and a second drive signal is coupled to the at least one of the first remaining electrodes, the first and second drive signals being out of phase with each other, and the at least one of the electrodes from the second set of electrodes is coupled to a measurement circuit.

3. The method of claim 1, wherein the differential technique comprises a differential receive technique in which the at least one of the electrodes from the second set of electrodes is coupled to a drive signal, and the first reference electrode and the at least one of the first remaining electrodes are coupled to a difference circuit.

4. The method of claim 3, wherein the difference circuit comprises an amplifier having an inverting input and a non-inverting input, and wherein the first reference electrode is coupled to the inverting input or to the non-inverting input, and the at least one of the first remaining electrodes is coupled to the non-inverting input or to the inverting input, respectively.

5. The method of claim 3, wherein the difference circuit comprises a switched capacitor circuit.

6. The method of claim 1, wherein the differential technique comprises both a differential drive technique and a differential receive technique.

7. The method of claim 1, further comprising:

monitoring the measured touch signals for an indication that the first reference electrode is experiencing a touch.

8. The method of claim 7, wherein the measured touch signals have an expected phase or polarity, and wherein the indication comprises at least one of the measured touch signals being of opposite phase or polarity to the expected phase or polarity.

9. The method of claim 7 further comprising:

in response to the indication, selecting at least one different electrode from the first set of electrodes to function as the first reference electrode.

10. The method of claim 1, further comprising:

measuring self-capacitances of at least some of the electrodes in the first set of electrodes;

wherein the received information comprises the measured self-capacitances.

11. The method of claim 1, wherein the measuring is part of a scan of touch data for the array of nodes, and wherein the received information comprises touch data for the array of nodes from a previous scan.

12. The method of claim 1, wherein the received information comprises historical touch data for the array of nodes.

13. The method of claim 1, wherein the touch panel is used with a display, and wherein the received information comprises display information for the display.

14. A method of determining touches on a touch panel, the touch panel comprising a plurality of electrodes arranged in an electrode matrix comprising a first set of electrodes capacitively coupled to a second set of electrodes at an array of nodes defining an active touch-sensitive area of the touch panel, the method comprising:

selecting at least one electrode from the first set of electrodes to function as a first reference electrode, remaining ones of the first set of electrodes referred to as first remaining electrodes;

measuring touch signals for at least some of the nodes using a differential technique, the differential technique for each such node utilizing the first reference electrode in combination with at least one of the first remaining electrodes and with at least one of the electrodes from the second set of electrodes;

monitoring the measured touch signals for an indication that the first reference electrode is experiencing a touch; and

in response to the indication, selecting at least one different electrode from the first set of electrodes to function as the first reference electrode.

15. The method of claim 14, wherein the measured touch signals have an expected characteristic, and wherein the indication comprises at least one of the measured touch signals not having the expected characteristic.

16. The method of claim 15, wherein the expected characteristic comprises an expected phase or polarity.

17. The method of claim 14, wherein the differential technique comprises a differential drive technique in which a first drive signal is coupled to the first reference electrode and a second drive signal is coupled to the at least one of the first remaining electrodes, the first and second drive signals being out of phase with each other, and the at least one of the electrodes from the second set of electrodes is coupled to a measurement circuit.

18. The method of claim 14, wherein the differential technique comprises a differential receive technique in which the at least one of the electrodes from the second set of electrodes is coupled to a drive signal, and the first reference electrode is coupled to an inverting input or a non-inverting input of an amplifier, and the at least one of the first remaining electrodes is coupled to the non-inverting input or the inverting input, respectively, of the amplifier.

19. The method of claim 14, wherein the differential technique comprises a differential receive technique in which the at least one of the electrodes from the second set of electrodes is coupled to a drive signal, and the first reference electrode and the at least one of the first remaining electrodes are coupled to a difference circuit.

20. The method of claim 19, wherein the difference circuit comprises an amplifier having an inverting input and a non-inverting input, and wherein the first reference electrode is coupled to the inverting input or to the non-inverting input, and the at least one of the first remaining electrodes is coupled to the non-inverting input or to the inverting input, respectively.

21. The method of claim 19, wherein the difference circuit comprises a switched capacitor circuit.

22. A device, comprising:

a touch panel comprising a plurality of electrodes arranged in an electrode matrix comprising a first set of electrodes capacitively coupled to a second set of electrodes at an array of nodes defining an active touch-sensitive area of the touch panel; and

controller electronics coupled to the touch panel, the controller electronics configured to;

receive information indicative of which of the electrodes in the first set of electrodes are not experiencing, or are unlikely to experience, a touch;

select, based on the received information, at least one electrode from the first set of electrodes that are not experiencing, or are unlikely to experience, a touch to function as a first reference electrode, remaining ones of the first set of electrodes referred to as first remaining electrodes; and

measure touch signals for at least some of the nodes using a differential technique, the differential technique for each such node utilizing the first reference electrode in combination with at least one of the first remaining electrodes and with at least one of the electrodes from the second set of electrodes.

23. A device, comprising:

a touch panel comprising a plurality of electrodes arranged in an electrode matrix comprising a first set of electrodes capacitively coupled to a second set of electrodes at an array of nodes defining an active touch-sensitive area of the touch panel; and

controller electronics coupled to the touch panel, the controller electronics configured to;

select at least one electrode from the first set of electrodes to function as a first reference electrode, remaining ones of the first set of electrodes referred to as first remaining electrodes;

measure touch signals for at least some of the nodes using a differential technique, the differential technique for each such node utilizing the first reference electrode in combination with at least one of the first remaining electrodes and with at least one of the electrodes from the second set of electrodes;

monitor the measured touch signals for an indication that the first reference electrode is experiencing a touch; and

in response to the indication, select at least one different electrode from the first set of electrodes to function as the first reference electrode.