Driving sensor electrodes for absolute capacitive sensing

Patent metadata

Field	Value
Publication number	US-9753587-B2
Application number	US-201414297373-A
Country	US
Kind code	B2
Filing date	Jun 5, 2014
Priority date	Jun 5, 2014
Publication date	Sep 5, 2017
Grant date	Sep 5, 2017

Abstract

In an example, a processing system includes a sensor module having sensor circuitry. The sensor module is configured to drive sensor electrodes with a capacitive sensing signal to acquire first changes of capacitance between each of the sensor electrodes and at least one input object; and drive at least one sensor electrode in a first set of the sensor electrodes with a reference signal and at least one sensor electrode in a second set of the sensor electrodes with a capacitive sensing signal to acquire second changes of capacitance between the at least one sensor electrode in the second set and the at least one input object. The processing system further includes a capacitive measurer module configured to determine a capacitive image based at least in part on the first and second changes of capacitance.

First claim

What is claimed is:

1. A processing system, comprising:
a sensor module comprising sensor circuitry, the sensor module configured to:
drive sensor electrodes with a capacitive sensing signal to measure first changes of capacitance between each of the sensor electrodes and at least one input object; and
drive at least one sensor electrode in a first set of the sensor electrodes with a reference signal and at least one sensor electrode in a second set of the sensor electrodes with a capacitive sensing signal to measure second changes of capacitance between the at least one sensor electrode in the second set and the at least one input object; and

a capacitive measurer module configured to determine a capacitive image based at least in part on the first and second changes of capacitance.

2. The processing system of claim 1 , wherein the first set of the sensor electrodes is disposed orthogonal to the second set of the sensor electrodes.

3. The processing system of claim 1 , wherein the sensor module is configured to drive the at least one sensor electrode in the first set of the sensor electrodes with a reference signal and the at least one sensor electrode in the second set of the sensor electrodes with a capacitive sensing signal to measure the second changes of capacitance by:
driving a first sensor electrode in the first set with a reference signal while driving the at least one sensor electrode in the second set with a capacitive sensing signal; and
driving a second sensor electrode in the first set with a reference signal while driving the at least one sensor electrode in the second set with a capacitive sensing signal.

4. The processing system of claim 1 , wherein the capacitive measurer module is configured to determine the capacitive image by differencing the first changes of capacitance and the second changes of capacitance.

5. The processing system of claim 1 , wherein the sensor module is configured to drive the sensor electrodes with a capacitive sensing signal to measure the first changes of capacitance by driving the sensor electrodes concurrently with a capacitive sensing signal.

6. The processing system of claim 1 , wherein the sensor module is configured to drive the sensor electrodes with a capacitive sensing signal to measure the first changes of capacitance by:
driving the first set of the sensor electrodes with a capacitive sensing signal while driving the second set of the sensor electrodes with a guard signal during a first time period; and
driving the first set of the sensor electrodes with a guard signal while driving the second set of the sensor electrodes with a capacitive sensing signal during a second time period.

7. The processing system of claim 1 , wherein the sensor module is configured to drive the at least one sensor electrode in the first set of the sensor electrodes with a reference signal and the at least one sensor electrode in the second set of the sensor electrodes with a capacitive sensing signal to measure the second changes of capacitance by:
obtaining a first capacitive profile along an axis defined by a first plurality of the sensor electrodes and a second capacitive profile along an axis defined by a second plurality of sensor electrodes; and
selecting the first set of the sensor electrodes as either the first plurality of the sensor electrodes or the second plurality of the sensor electrodes based on numbers of local maxima in the first and second capacitive profiles.

8. The processing system of claim 1 , wherein the sensor module is configured to drive the at least one sensor electrode in the first set of the sensor electrodes with a reference signal and the at least one sensor electrode in the second set of the sensor electrodes with a capacitive sensing signal to measure the second changes of capacitance by:
obtaining a capacitive profile along an axis defined by the first set of sensor electrodes; and
selecting the at least one electrode in the first set to be driven with a reference signal based on the capacitive profile.

9. The processing system of claim 1 , wherein the sensor module is configured to drive the at least one sensor electrode in the first set of the sensor electrodes with a reference signal and the at least one sensor electrode in the second set of the sensor electrodes with a capacitive sensing signal to measure the second changes of capacitance by:
driving a plurality of sensor electrodes in the first set with a reference signal while driving at least one sensor electrode in the second set with a capacitive sensing signal.

10. The processing system of claim 1 , wherein the sensor module is configured to:
drive at least one sensor electrode in the second set of the sensor electrodes with a reference signal and at least one sensor electrode in the first set of the sensor electrodes with a capacitive sensing signal to measure third changes of capacitance between the at least one sensor electrode in the first set and the at least one input object; and
wherein the capacitive measurer module is configured to determine the capacitive image based at least in part on the first changes of capacitance and an average of the second changes of capacitance and the third changes of capacitance.

11. A method of driving sensor electrodes for capacitive sensing, comprising:
driving the sensor electrodes with a capacitive sensing signal to measure first changes of capacitance between each of the sensor electrodes and at least one input object;
driving at least one sensor electrode in a first set of the sensor electrodes with a reference signal and at least one sensor electrode in a second set of the sensor electrodes with a capacitive sensing signal to measure second changes of capacitance between the at least one sensor electrode in the second set and the at least one input object; and
determining a capacitive image based at least in part on the first and second changes of capacitance.

12. The method of claim 11 , wherein the step of determining the capacitive image comprises:
differencing the first changes of capacitance and the second changes of capacitance.

13. The method of claim 11 , wherein the step of driving the sensor electrodes with a capacitive sensing signal to measure the first changes of capacitance comprises:
driving the sensor electrodes concurrently with a capacitive sensing signal.

14. The method of claim 11 , wherein the step of driving the sensor electrodes with a capacitive sensing signal to measure the first changes of capacitance comprises:
driving the first set of the sensor electrodes with a capacitive sensing signal while driving the second set of the sensor electrodes with a guard signal during a first time period; and
driving the first set of the sensor electrodes with a guard signal while driving the second set of the sensor electrodes with a capacitive sensing signal during a second time period.

15. The method of claim 11 , wherein the step of driving the at least one sensor electrode in the first set of the sensor electrodes with a reference signal and the at least one sensor electrode in the second set of the sensor electrodes with a capacitive sensing signal to measure the second changes of capacitance comprises:
obtaining a first capacitive profile along an axis defined by a first plurality of the sensor electrodes and a second capacitive profile along an axis defined by a second plurality of sensor electrodes; and
selecting the first set of the sensor electrodes as either the first plurality of the sensor electrodes or the second plurality of the sensor electrodes based on numbers of local maxima in the firs

Assignees

• Synaptics Inc

Inventors

• Hoch David

Classifications

• G01R27/2605

  Measuring capacitance (capacitive sensors G01D5/24) · CPC title

• G01V3/088 Primary

  operating with electric fields (G01V3/082 takes precedence) · CPC title

• G06F3/044 Primary

  by capacitive means · CPC title

• G06F3/0416

  Control or interface arrangements specially adapted for digitisers · CPC title

• G06F3/0446 Primary

  using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes · CPC title