PARASITIC CAPACITANCE FILTER FOR SINGLE-LAYER CAPACITIVE IMAGING SENSORS

• US 20150109233A1
• Filed: 10/23/2013
• Published: 04/23/2015
• Est. Priority Date: 10/23/2013
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: MOORE, Tyler, SOLVEN, Derek
• Granted Patent: US 9,495,046 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 3/04186 Touch location disambiguation
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes

Abstract

An approach is provided for estimating and correcting parasitic responses of a touch sensor device. The input device measures a first capacitance signal generated by a first pixel that is covered at least partially by an input object. The input device measures a second capacitance signal generated by a second pixel that is covered at least partially by the input object. The input device measures a third capacitance signal generated by a third pixel. Based on at least the first capacitance signal and the second capacitance signal, the input device identifies a position of the input object within the sensing region. Based on the position of the input object, the input device identifies a trace covered by the input object and associated with the third pixel. The input device calculates an updated third capacitance signal by subtracting a correction amount from the third capacitance signal.

Claims

1. A computer-implemented method of sensing a position of an input object, comprising:

determining a first pixel response of a first pixel covered at least partially by an input object;

determining a second pixel response of a second pixel covered at least partially by the input object;

determining a third pixel response of a third pixel, wherein the first pixel, the second pixel, and the third pixel are disposed within a capacitive sensing region of a touch sensor device;

based on at least the first pixel response and the second pixel response, identifying a position of the input object within the capacitive sensing region;

based on the position of the input object, determining that the input object is positioned near a first trace, wherein the first trace is associated with the third pixel; and

calculating an updated third pixel response by removing a correction amount from the third pixel response after determining that the input object is positioned near the first trace.

2. The method of claim 1, wherein calculating the updated third pixel response further comprises:

generating a pixel response line segment between the first pixel and the second pixel by interpolating a line across a distance between the first pixel and the second pixel using information received from the first pixel response and the second pixel response; and

based on a location of the first trace along the pixel response line segment, calculating the correction amount.

3. The method of claim 2, further comprising calculating a number of traces between the first pixel and the second pixel, wherein a length of the pixel response line segment is related to the number of traces disposed between the first pixel and the second pixel, and wherein the location of the first trace is between the first pixel and the second pixel.

4. The method of claim 3, further comprising:

calculating a difference between the first pixel response and the second pixel response; and

calculating a slope of the pixel response line segment by dividing the difference by the number of traces between the first pixel and the second pixel.

5. The method of claim 1, wherein the sensor is a single layer sensor.

6. The method of claim 1, wherein calculating the updated third pixel response further comprises:

calculating a number of covered traces;

calculating a width of each covered trace; and

based on the number of covered traces and the width of each covered trace, calculating a parasitic scale factor and a location scale factor for the correction amount.

7. The method of claim 1, further comprising:

determining a fourth pixel response of a fourth pixel, wherein the fourth pixel is disposed within the capacitive sensing region of the touch sensor device;

based on the position of the input object, determining that the input object is positioned near a second trace, wherein the second trace is associated with the fourth pixel; and

calculating an updated fourth pixel response by subtracting another correction amount from the fourth pixel response after determining that the input object is positioned near the second trace.

8. The method of claim 1, wherein the updated third pixel response is associated with an analysis of a first row of the capacitive sensing region, the method further comprising:

proceeding to a second row of the capacitive sensing region;

determining a fourth pixel response of a fourth pixel associated with an analysis of a second row of the capacitive sensing region, wherein the fourth pixel is disposed within the capacitive sensing region of the touch sensor device;

based on the position of the input object, determining that the input object is positioned near a second trace, wherein the second trace is associated with the fourth pixel; and

calculating an updated fourth pixel response by subtracting another correction amount from the fourth pixel response after determining that the input object is positioned near the second trace.

9. A computer readable storage medium comprising instructions that in response to execution by a computing device cause the computing device to perform operations, comprising:

determining a first pixel response of a first pixel covered at least partially by an input object;

determining a second pixel response of a second pixel covered at least partially by the input object;

determining a third pixel response of a third pixel, wherein the first pixel, the second pixel, and the third pixel are disposed within a capacitive sensing region of a touch sensor device;

based on at least the first pixel response and the second pixel response, identifying a position of the input object within the capacitive sensing region;

based on the position of the input object, determining that the input object is positioned near a first trace, wherein the first trace is associated with the third pixel; and

calculating an updated third pixel response by subtracting a correction amount from the third pixel response after determining that the input object is positioned near the first trace.

10. The computer readable storage medium of claim 9, wherein calculating the updated third pixel response further comprises:

generating a pixel response line segment between the first pixel and the second pixel by interpolating a line across a distance between the first pixel and the second pixel using information received from the first pixel response and the second pixel response; and

based on a location of the first trace along the pixel response line segment, calculating the correction amount.

11. The computer readable storage medium of claim 10, further comprising calculating a number of traces between the first pixel and the second pixel, wherein a length of the pixel response line segment is related to the number of traces disposed between the first pixel and the second pixel, and wherein the location of the first trace is between the first pixel and the second pixel.

12. The computer readable storage medium of claim of 11, further comprising:

calculating a difference between the first pixel response and the second pixel response; and

calculating a slope of the pixel response line segment by dividing the difference by the number of traces between the first pixel and the second pixel.

13. The computer readable storage medium of claim 9, wherein the sensor is a single layer sensor.

14. The computer readable storage medium of claim 9, wherein calculating the updated third pixel response further comprises:

calculating a number of covered traces;

calculating a width of each covered trace; and

based on the number of covered traces and the width of each covered trace, calculating a parasitic scale factor and a location scale factor for the correction amount.

15. The computer readable storage medium of claim 9, further comprising:

determining a fourth pixel response of a fourth pixel, wherein the fourth pixel is disposed within the capacitive sensing region of the touch sensor device;

based on the position of the input object, determining that the input object is positioned near a second trace, wherein the second trace is associated with the fourth pixel; and

calculating an updated fourth pixel response by subtracting another correction amount from the fourth pixel response after determining that the input object is positioned near the second trace.

16. The computer readable storage medium of claim 9, wherein the updated third pixel response is associated with an analysis of a first row of the capacitive sensing region, the method further comprising:

proceeding to a second row of the capacitive sensing region;

determining a fourth pixel response of a fourth pixel associated with an analysis of a second row of the capacitive sensing region, wherein the fourth pixel is disposed within the capacitive sensing region of the touch sensor device;

based on the position of the input object, determining that the input object is positioned near a second trace, wherein the second trace is associated with the fourth pixel; and

calculating an updated fourth pixel response by subtracting another correction amount from the fourth pixel response after determining that the input object is positioned near the second trace.

17. A method of sensing a position of an input object within a sensing region of an input device, comprising:

measuring a first capacitance signal generated by a first pixel that is covered at least partially by an input object;

measuring a second capacitance signal generated by a second pixel that is covered at least partially by the input object;

measuring a third capacitance signal generated by a third pixel;

based on at least the first capacitance signal and the second capacitance signal, identifying a position of the input object within the sensing region;

based on the position of the input object, determining that the input object is positioned near a trace, wherein the trace is associated with the third pixel; and

calculating an updated third capacitance signal by subtracting a correction amount from the third capacitance signal after determining that the input object is positioned near the trace.

18. The method of claim 17, further comprising:

generating the correction amount by a process that comprises;

generating a pixel response line segment between the first pixel and the second pixel by interpolating a line across a distance between the first pixel and the second pixel using the first capacitance signal and the second capacitance signal; and

based on a location of the trace along the pixel response line segment, determining the correction amount.

19. The method of claim 18, further comprising calculating a number of traces between the first pixel and the second pixel, wherein a length of the pixel response line segment is represented by the number of traces between the first pixel and the second pixel, and wherein the location of the first trace is between the first pixel and the second pixel.

20. The method of claim 17, calculating the updated third pixel response comprises:

calculating a number of covered traces;

calculating a width of each covered trace; and

based on the number of covered traces and the width of each covered trace, calculating a parasitic scale factor and a location scale factor for the correction amount.