CAPACITIVE TOUCH SYSTEM USING BOTH SELF AND MUTUAL CAPACITANCE

• US 20120113047A1
• Filed: 04/19/2011
• Published: 05/10/2012
• Est. Priority Date: 04/30/2010
• Status: Active Grant

• Current Assignee: Microchip Technology Incorporated
• Original Assignee: Microchip Technology Incorporated
• Inventors: Hanauer, Jerry, O'Connor, Todd
• Granted Patent: US 8,933,907 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G06F 2203/04104 Multi-touch detection in digitiser, i.e. details about the simultaneous detection of a plurality of touching locations, e.g. multiple fingers or pen and finger
• CPC Class Codes: G06F 3/041662 using alternate mutual and self-capacitive scanning
• CPC Class Codes: G06F 3/04186 Touch location disambiguation
• 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

Systems and methods for determining multiple touch events in a multi-touch sensor system are provided. The system may have a touch sensor including nodes defined by a plurality of electrodes, which may comprise a first and second set. The method may include measuring self capacitance for at least two electrodes, detecting a touched electrode, and measuring the mutual capacitance for only a subset of the nodes (e.g., fewer than all of the nodes and including at least the nodes corresponding to the touched electrodes) resulting in the detection of two or more touched nodes. The self capacitance measurements may be performed on each of the electrodes, and the touched electrodes may comprise electrodes from both the first and second sets. Alternatively, the self capacitance measurements may be performed only on electrodes in the first set, and the touched electrodes may comprise electrodes from only the first set.

Claims

1. A method for determining multiple touch events in a multi-touch sensor system having a touch sensor including a plurality of nodes defined by a plurality of electrodes, the method comprising:

performing self capacitance measurements for at least two of the plurality of electrodes;

detecting one or more touched electrodes as a result of the performed self capacitance measurements;

performing a plurality of mutual capacitance measurements for only a subset of the nodes, wherein the subset is fewer than all of the nodes and includes at least the nodes corresponding to the touched electrodes; and

detecting two or more touched nodes as a result of the plurality of mutual capacitance measurements.

2. The method of claim 1 wherein the one or more touched electrodes comprises only one touched electrode.

3. The method of claim 1 wherein:

the plurality of electrodes comprises a first set of electrodes and a second set of electrodes;

the self capacitance measurements are performed on each of the electrodes; and

the touched electrodes comprise electrodes from both the first set of electrodes and the second set of electrodes.

4. The method of claim 3 wherein the subset of nodes comprises only the nodes corresponding to the touched electrodes.

5. The method of claim 3 wherein the subset of nodes comprises nodes that are adjacent to the touched electrodes

6. The method of claim 3 wherein the self capacitance measurements and the mutual capacitance measurements are performed according to at least one of:

a frequency measurement method, a period measurement method, a VACST method, and a TCSV method.

7. The method of claim 3 wherein the touched nodes are detected by a process of elimination.

8. The method of claim 3 wherein exactly one mutual capacitance measurement is performed and, based on that measurement, two touched nodes are detected.

9. The method of claim 3 wherein the first set of electrodes corresponds to a first layer of the touch sensor.

10. The method of claim 9 wherein the second set of electrodes corresponds to a second layer of the touch sensor.

11. The method of claim 3 wherein the touched electrodes are detected when an object is in proximity to, but not directly contacting, the touched electrodes.

12. The method of claim 3 wherein touched nodes are detected when an object is in proximity to, but not directly contacting, the touched nodes.

13. The method of claim 1 wherein:

the plurality of electrodes comprises a first set of electrodes and a second set of electrodes;

the self capacitance measurements are performed on each of the electrodes in the first set of electrodes and not on the electrodes in the second set of electrodes; and

the touched electrodes comprise electrodes from only the first set of electrodes.

14. A system for detecting one or more touch events on a touch sensor, comprising:

a touch sensor having a plurality of nodes defined by a plurality of electrodes;

self capacitance measuring means for measuring the self capacitance of each of the plurality of electrodes;

mutual capacitance measuring means for measuring the mutual capacitance at only a subset of the nodes, wherein the subset is fewer than all of the nodes and is determined based on an output of the self capacitance measuring means; and

means for detecting, based on the output of the self capacitance measuring means and an output of the mutual capacitance measuring means, two or more touched nodes.

15. A system for detecting one or more touch events on a touch sensor, comprising:

a touch sensor having a plurality of nodes defined by a plurality of electrodes; and

a touch controller having a self capacitance measuring means for measuring the self capacitance of each of the plurality of electrodes, and a mutual capacitance measuring means for measuring the mutual capacitance of each of the plurality of nodes;

wherein the touch controller is operable to;

perform, using the self capacitance measuring means, self capacitance measurements for at least two of the plurality of electrodes;

detect one or more touched electrodes as a result of the performed self capacitance measurements;

perform, using the mutual capacitance measuring means, a plurality of mutual capacitance measurements for only a subset of the nodes, wherein the subset is fewer than all of the nodes and includes at least the nodes corresponding to the touched electrodes; and

detect two or more touched nodes as a result of the plurality of mutual capacitance measurements.

16. The system of claim 15 wherein the one or more touched electrodes comprises only one touched electrode.

17. The system of claim 15 wherein:

the plurality of electrodes comprises a first set of electrodes and a second set of electrodes;

the touch controller performs the self capacitance measurements on each of the electrodes; and

the touched electrodes comprise electrodes from both the first set of electrodes and the second set of electrodes.

18. They system of claim 15 wherein:

the plurality of electrodes comprises a first set of electrodes and a second set of electrodes;

the touch controller performs the self capacitance measurements on each of the electrodes in the first set of electrodes and not on the electrodes in the second set of electrodes; and

the touched electrodes comprise electrodes from only the first set of electrodes.