DIFFERENTIAL SENSING FOR A TOUCH PANEL

• US 20100079401A1
• Filed: 09/26/2008
• Published: 04/01/2010
• Est. Priority Date: 09/26/2008
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Staton, Kenneth Lawrence
• Granted Patent: US 9,927,924 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 touch panel can configured to reduce adverse effects associated with noise that can be injected into the panel when touched by performing a sensing operation at each sensor in both a panel-stimulated and non panel-stimulated state. The touch panel can detect a touch event by sensing touch in a non-stimulated state to quantify a noise level injected into the touch panel by the touch, and subtracting that noise level from a detection signal sensed in the stimulated state. In one embodiment, a sensing operation can be performed for a particular sensor at two successive time periods—one for each state—within a single scan cycle. In another embodiment, a sensing electrode configuration can be provided that enables a sensing operation to be performed for a particular sensor in both a panel-stimulated and non panel-stimulated state concurrently.

Claims

1. A computing device comprising:

a touch sensor panel including a plurality of driving elements, a plurality of sensing elements, and a plurality of sensors, each sensor formed by a driving element and a sensing element pair; and

panel subsystem logic configured for filtering a first signal generated by a first sensing element of a particular sensor in response to a stimulus applied to a driving element of the particular sensor to reduce noise injected into the first sensing element by a touch caused by an object.

2. The computing device of claim 1, wherein the touch sensor panel is grounded to the computing device and the object is grounded to earth.

3. The computing device of claim 1, wherein the panel subsystem logic is configured to filter the first signal using a second signal generated by the first sensing element when not being stimulated.

4. The computing device of claim 1, wherein the panel subsystem is configured to filter the first signal using a second signal generated by a second sensing element.

5. The portable computing device of claim 4, wherein

the driving element and the first and second sensing elements are arranged relative to one another such that, upon stimulation of the driving element and touching of the touch sensor panel by the object,

a capacitance formed between the object and the first sensing element is substantially similar to a capacitance formed between the object and the second sensing element, and

a capacitance formed between the driving element and the second sensing element is substantially less than a capacitance formed between the driving element and the first sensing element.

6. The computing device of claim 5, wherein the driving element, the first sensing element and the second sensing element occupy the same layer.

7. The computing device of claim 5, wherein the driving element, the first sensing element and the second sensing element occupy different layers.

8. The computing device of claim 5, wherein the driving element occupies a first layer, and the first sensing element and the second sensing element occupy a second layer.

9. A method for reducing noise coupled into a touch sensor panel from an object, comprising:

applying a stimulus to a driving element of a particular sensor in the touch sensor panel to enable detection of a touch on the touch sensor panel by the object; and

filtering a first signal generated by the first sensing element of the particular sensor in response to the stimulus to reduce noise injected into the first sensing element by a touch caused by the object.

10. The method of claim 9, wherein the touch sensor panel is grounded to the portable computing device and the object is grounded to earth.

11. The method of claim 9, wherein the first signal is filtered using a second signal generated by the first sensing element when not being stimulated by the stimulus.

12. The method of claim 9, wherein the first signal is filtered using a second signal generated by a second sensing element.

13. The method of claim 12, wherein

the driving element and the first and second sensing elements are arranged relative to one another such that, upon stimulation of the driving element and touching of the touch sensor panel by the object,

a capacitance formed between the object and the first sensing element is substantially similar to a capacitance formed between the object and the second sensing element, and

a capacitance formed between the driving element and the second sensing element is substantially less than a capacitance formed between the driving element and the first sensing element.

14. A sensor for detecting a touch by an object on a touch sensor panel, comprising:

a driving element;

a first sensing element; and

a second sensing element,

wherein the driving element and the first and second sensing elements are arranged relative to one another such that, upon stimulation of the driving element and touching of the touch sensor panel by the object,

a capacitance formed between the object and the first sensing element is substantially similar to a capacitance formed between the object and the second sensing element, and

a capacitance formed between the driving element and the second sensing element is substantially less than a capacitance formed between the driving element and the first sensing element.

15. The sensor of claim 14, wherein the driving element, the first sensing element and the second sensing element occupy the same layer.

16. The sensor of claim 14, wherein the driving element, the first sensing element and the second sensing element occupy different layers.

17. The sensor of claim 14, wherein the driving element occupies a first layer, and the first sensing element and the second sensing element occupy a second layer.

18. The sensor of claim 17, the sensor being incorporated within a computing device.

19. A mobile telephone comprising:

a touch sensor panel including a plurality of driving elements, a plurality of sensing elements, and a plurality of sensors, each sensor formed by a driving element and a sensing element pair; and

panel subsystem logic configured for filtering a first signal generated by a first sensing element of a particular sensor in response to a stimulus applied to a driving element of the particular sensor to reduce noise injected into the first sensing element by a touch caused by an object.

20. A portable media player comprising:

a touch sensor panel including a plurality of driving elements, a plurality of sensing elements, and a plurality of sensors, each sensor formed by a driving element and a sensing element pair; and

panel subsystem logic configured for filtering a first signal generated by a first sensing element of a particular sensor in response to a stimulus applied to a driving element of the particular sensor to reduce noise injected into the first sensing element by a touch caused by an object.