Parasitic capacitance filter for single-layer capacitive imaging sensors

Patent metadata

Field	Value
Publication number	US-9495046-B2
Application number	US-201314061593-A
Country	US
Kind code	B2
Filing date	Oct 23, 2013
Priority date	Oct 23, 2013
Publication date	Nov 15, 2016
Grant date	Nov 15, 2016

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.

First claim

The invention claimed is:

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;
calculating an updated third pixel response by:
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,
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,
calculating a difference between the first pixel response and the second pixel response,
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,
calculating a correction amount based on a location of the first trace along the pixel response line segment, and
removing the correction amount from the third pixel response, the correction amount being based on the determination that the input object is positioned near the first trace.

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

3. 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.

4. 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.

5. 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, the correction amount being based on the determination that the input object is positioned near the first trace,
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.

6. A non-transitory 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:
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,
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,
calculating a difference between the first pixel response and the second pixel response,
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,
calculating a correction amount based on a location of the first trace along the pixel response line segment, and

subtracting the correction amount from the third pixel response, the correction amount being based on the determination that the input object is positioned near the first trace.

7. The non-transitory computer readable storage medium of claim 6 , wherein the sensor is a single layer sensor.

8. The non-transitory computer readable storage medium of claim 6 , 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.

9. The non-transitory computer readable storage medium of claim 6 , wherein the updated third pixe

Assignees

• Synaptics Inc

Inventors

• Moore Tyler
• Solven Derek

Classifications

• G06F3/044 Primary

  by capacitive means · CPC title

• G06F3/0418

  for error correction or compensation, e.g. based on parallax, calibration or alignment · CPC title

• G06F2203/04104

  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 title

• G06F3/0443

  using a single layer of sensing electrodes · CPC title

• G06F3/04186 Primary

  Touch location disambiguation · CPC title