CONCURRENT TOUCH AND NEGATIVE PIXEL SCAN

• US 20130069905A1
• Filed: 09/15/2011
• Published: 03/21/2013
• Est. Priority Date: 09/15/2011
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Christoph Horst Krah
• Inventors: KRAH, Christoph Horst, Yousefpor, Marduke
• Granted Patent: US 9,746,967 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 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

A concurrent touch and negative pixel scan performed at a touch panel is disclosed. The concurrent scan can include sensing an object proximate to the touch panel and sensing a negative pixel effect, based the object'"'"'s grounding condition, at the touch panel, at the same time. As a result, sense signals indicative of the proximity of the object and coupling signals indicative of the negative pixel effect'"'"'s magnitude can be captured concurrently. Because the negative pixel effect can cause errors or distortions in the sense signals, the coupling signals can be used to compensate the sense signals for the negative pixel effect.

Claims

1. A method for scanning a touch panel comprising:

performing a concurrent touch and negative pixel scan at a touch panel, the scan sensing an object proximate to the touch panel and sensing a negative pixel effect at the touch panel at substantially the same time; and

capturing concurrently sense signals indicative of the proximity of the object to the touch panel and coupling signals indicative of a magnitude of the negative pixel effect on the touch panel.

2. The method of claim 1, where performing the concurrent scan comprises:

driving a first set of conductive lines of the touch panel with stimulation signals,

generating the sense signals on a second set of conductive lines of the touch panel in response to the stimulation signals, the sense signals formed by a capacitive coupling between pairs of a conductive line in the first set of conductive lines and a conductive line in the second set of conductive lines, and

generating the coupling signals on the first set of conductive lines in response to the stimulation signals, the coupling signals formed by a capacitive coupling between one or more pairs of the first set of conductive lines.

3. The method of claim 1, wherein capturing concurrently the sense signals and the coupling signals comprises:

capturing the coupling signals on a first set of conductive lines of the touch panel; and

capturing the sense signals on a second set of conductive lines of the touch panel.

4. The method of claim 1, comprising:

compensating the sense signals for the negative pixel effect, the compensating including applying the coupling signals to the sense signals.

5. The method of claim 1, comprising:

capturing noise signals indicative of noise introduced into the touch panel by adjacent circuitry; and

rejecting the noise from the touch panel by subtracting the noise signals from the coupling signals and the sense signals.

6. The method of claim 1, comprising:

processing the sense signals to determine a capacitance indicative of the proximity of the object, the processing including, for m captured sense signals, applying a matrix to the captured sense signals to produce m capacitance values, wherein m is an integer.

7. The method of claim 1, comprising:

processing the coupling signals to determine a capacitance indicative of the negative pixel effect on the touch panel, the processing including, for n captured coupling signals, applying a matrix to the captured coupling signals to produce n capacitance values, wherein n is an integer.

8. The method of claim 1, performing a second touch and negative pixel scan at the touch panel during a same scan period as the first touch and negative pixel scan.

9. A touch sensitive device comprising:

a touch panel including drive lines and sense lines, the drive lines configured to drive the touch panel to sense a proximate object and to generate coupling signals indicative of a grounding condition of the object and the sense lines configured to generate sense signals indicative of a proximity of the object; and

touch circuitry including

a first circuit configured to capture the sense signals based on capacitive coupling between pairs of the drive and sense lines, and

a second circuit configured to capture the coupling signals based on capacitive coupling between pairs of the drive lines,

wherein the sense signals and the coupling signals are captured concurrently.

10. The device of claim 9, wherein the first circuit of the touch circuitry comprises:

a drive circuit configured to supply a driving voltage to the drive lines to drive the touch panel; and

a sense circuit configured to capture the sense signals and to process the captured sense signals.

11. The device of claim 9, wherein the second circuit of the touch circuitry comprises:

a coupling circuit configured to capture the coupling signals, to isolate the captured coupling signals, and to process the isolated coupling signals.

12. The device of claim 9, wherein the touch circuitry comprises:

a switching circuit configured to switch between multiple configuration of the drive and sense lines.

13. The device of claim 9, wherein the touch circuitry comprises:

a noise rejection circuit configured to reject noise introduced into the touch panel by adjacent circuitry.

14. The device of claim 9 incorporated into at least one of a mobile telephone, a digital media player, or a portable computer.

15. A method for performing a concurrent touch and negative pixel scan at a touch panel, the method comprising:

performing a first concurrent touch and negative pixel scan at a touch panel, the touch panel being in a first configuration;

switching the touch panel from the first configuration to a second configuration; and

performing a second concurrent touch and negative pixel scan at the touch panel, the touch panel being in the second configuration.

16. The method of claim 15, wherein performing the first scan comprises:

stimulating the touch panel to sense a proximate object;

generating sense signals indicative of the proximity of the object; and

generating coupling signals indicative of a negative pixel effect at the touch panel based on a grounding condition of the object.

17. The method of claim 15, wherein the touch panel comprises a first set of conductive lines and a second set of conductive lines crossing the first set of conductive lines, the switching comprises:

switching from the first configuration, in which the first set of conductive lines act as drive lines to stimulate the touch panel to sense a proximate object and to cross-couple so as to generate coupling signals indicative a negative pixel effect at the touch panel and in which the second set of conductive lines act as sense lines to generate sense signals indicative of the proximity of the object, to the second configuration, in which the second set of conductive lines act as the drive lines and the first set of conductive lines act at the sense lines.

18. The method of claim 15, wherein performing the second scan comprises:

stimulating the touch panel to sense a proximate object;

generating sense signals indicative of the proximity of the object; and

generating coupling signals indicative of a negative pixel effect at the touch panel based on a grounding condition of the object.

19. The method of claim 15, comprising:

during the first scan, capturing a first set of sense signals indicating a touch at the touch panel and a first set of coupling signals indicating a negative pixel effect at the touch panel; and

during the second scan, capturing a second set of sense signals indicating the touch at the touch panel and a second set of coupling signals indicating the negative pixel effect at the touch panel.

20. The method of claim 19, comprising:

compensating for the negative pixel effect, the compensating including

combining the first and second sets of sense signals to form combined sense signals,

combining the first and second sets of coupling signals to form combined coupling signals, and

subtracting the combined coupling signals from the combined sense signals to compensate for the negative pixel effect.

21. A circuit for scanning a touch panel comprising:

a sensing circuit configured to sense an object proximate to a touch panel;

a coupling circuit configured to sense a negative pixel effect at the touch panel; and

scan logic configured to perform a scan of the touch panel so as to concurrently capture sense signals for sensing the proximate object and coupling signals for sensing the negative pixel effect.

22. The circuit of claim 21, wherein the sensing circuit comprises:

at least one touch buffer configured to supply stimulations signals to the touch panel to drive the touch panel; and

at least one sense amplifier configured to process the sense signals, the sense signals generated by the touch panel in response to the stimulation signals and indicative of the proximity of the object to the touch panel.

23. The circuit of claim 21, wherein the coupling circuit comprises:

at least one resistor configured to sense the coupling signals, the coupling signals caused by a coupling between touch panel components and indicative of the negative pixel effect; and

at least one differential analog-to-digital converter configured to isolate the coupling signals for processing.

24. The circuit of claim 21, wherein the coupling signals are subtracted from the sense signals to compensate the sense signals for the negative pixel effect.

25. A touch sensitive device comprising:

a touch panel configured to sense a proximate object;

touch circuitry including

a sensing circuit configured to capture touch panel sense signals indicative of a proximity of the object,

a coupling circuit configured to capture touch panel coupling signals indicative of a negative pixel effect due to a grounding condition of the object,

wherein the coupling signals and the sense signals are captured concurrently during a scan of the touch panel, and

a noise rejection circuit configured to reject noise introduced into the touch panel by adjacent circuitry; and

a processor configured to apply the coupling signals to the sense signals so as to compensate the sense signals for the negative pixel effect.