Low ground mass correction for capacitive imaging sensors

1. A capacitive sensing input system comprising:

a plurality of sensor electrodes disposed in a sensor electrode pattern, wherein, when under a low ground mass (LGM) condition:

proximity-sensing pairs of electrodes formed by a first selective pairing of the plurality of sensor electrodes have an increased sensitivity to a presence of an input object in comparison to

LGM-sensitive pairs of electrodes formed by a second selective pairing of the plurality of sensor electrodes that are primarily sensitive to the LGM condition; and

a processing system configured to, while under the LGM condition:

prior to determining a first LGM term:

determine a size of the input object, and

depending on the size of the input object, select a spatial separation of the two sensor electrodes of a first of the LGM-sensitive pairs of electrodes,

determine the first LGM term using a mutual capacitance sensing with the first of the LGM-sensitive pairs of electrodes,

obtain a first transcapacitance sensing signal for a sensing element formed by a first of the proximity-sensing pairs of electrodes, and

generate an LGM-corrected transcapacitance sensing signal by correcting the first transcapacitance sensing signal using the first LGM term.

2. The capacitive sensing input system of claim 1 , wherein the processing system is further configured to, prior to generating the LGM-corrected transcapacitance sensing signal:

map the first LGM term onto the sensing element.

3. The capacitive sensing input system of claim 1 , wherein determining the first LGM term comprises:

determining that the input object is located at the sensing element.

4. The capacitive sensing input system of claim 3 , wherein the determination is made based on at least one selected from the group consisting of:

an absolute capacitance profile sensing, and

a transcapacitance profile sensing.

5. The capacitive sensing input system of claim 1 , wherein the two sensor electrodes of the first of the LGM-sensitive pairs of electrodes are non-intersecting.

6. The capacitive sensing input system of claim 5 , further comprising an additional electrode disposed between the two sensor electrodes of the first of the LGM-sensitive pairs of electrodes.

7. The capacitive sensing input system of claim 6 , wherein the additional electrode is one selected from the group consisting of:

a ground electrode, and

a guard electrode.

8. The capacitive sensing input system of claim 1 , wherein the two sensor electrodes of the first of the proximity-sensing pairs of electrodes are intersecting.

9. A capacitive sensing input system comprising:

a plurality of sensor electrodes disposed in a sensor electrode pattern, wherein, when under a low ground mass (LGM) condition:

proximity-sensing pairs of electrodes formed by a first selective pairing of the plurality of sensor electrodes have an increased sensitivity to a presence of an input object in comparison to

LGM-sensitive pairs of electrodes formed by a second selective pairing of the plurality of sensor electrodes that are primarily sensitive to the LGM condition; and

a processing system configured to, while under the LGM condition:

determine a first LGM term using a mutual capacitance sensing with a first of the LGM-sensitive pairs of electrodes, wherein the first LGM term is in a first direction of the sensor electrode pattern, based on the first of the LGM-sensitive pairs of electrodes,

obtain a second LGM term with a second of the LGM-sensitive pairs of electrodes, in a second direction of the sensor electrode pattern, perpendicular to the first direction,

obtain a first transcapacitance sensing signal for a sensing element formed by a first of the proximity-sensing pairs of electrodes, and

generate an LGM-corrected transcapacitance sensing signal by correcting the first transcapacitance sensing signal using the first LGM term and the second LGM term.

10. A processing system interfacing with a plurality of sensor electrodes disposed in a sensor electrode pattern,

wherein, when under a low ground mass (LGM) condition:

proximity-sensing pairs of electrodes formed by a first selective pairing of the plurality of sensor electrodes have an increased sensitivity to a presence of an input object in comparison to

LGM-sensitive pairs of electrodes formed by a second selective pairing of the plurality of sensor electrodes that are primarily sensitive to the LGM condition,

wherein the processing system, while under the LGM condition, is configured to:

prior to determining a first LGM term:

determine a size of the input object, and

depending on the size of the input object, selecting a spatial separation of the two sensor electrodes of a first of the LGM-sensitive pairs of electrodes,

determine the first LGM term using a mutual capacitance sensing with the first of the LGM-sensitive pairs of electrodes,

obtain a first transcapacitance sensing signal for a sensing element formed by a first of the proximity-sensing pairs of electrodes, and

generate an LGM-corrected transcapacitance sensing signal by correcting the first transcapacitance sensing signal using the first LGM term.

11. The processing system of claim 10 , further configured to, prior to generating the LGM-corrected transcapacitance sensing signal:

map the first LGM term onto the sensing element.

12. The processing system of claim 10 , wherein determining the first LGM term comprises:

determining that the input object is located at the sensing element.

13. The processing system of claim 12 , wherein the determination is made based on at least one selected from the group consisting of:

an absolute capacitance profile sensing, and

a transcapacitance profile sensing.

14. A processing system interfacing with a plurality of sensor electrodes disposed in a sensor electrode pattern,

wherein, when under a low ground mass (LGM) condition:

proximity-sensing pairs of electrodes formed by a first selective pairing of the plurality of sensor electrodes have an increased sensitivity to a presence of an input object in comparison to

LGM-sensitive pairs of electrodes formed by a second selective pairing of the plurality of sensor electrodes that are primarily sensitive to the LGM condition,

wherein the processing system, while under the LGM condition, is configured to:

determine a first LGM term using a mutual capacitance sensing with a first of the LGM-sensitive pairs of electrodes, wherein the first LGM term is in a first direction of the sensor electrode pattern, based on the first of the LGM-sensitive pairs of electrodes,

obtain a second LGM term with a second of the LGM-sensitive pairs of electrodes, in a second direction of the sensor electrode pattern, perpendicular to the first direction,

obtain a first transcapacitance sensing signal for a sensing element formed by a first of the proximity-sensing pairs of electrodes, and

generate an LGM-corrected transcapacitance sensing signal by correcting the first transcapacitance sensing signal using the first LGM term and the second LGM term.

15. A method of capacitive sensing,

the method operating on a plurality of sensor electrodes disposed in a sensor electrode pattern, wherein, when under a low ground mass (LGM) condition:

proximity-sensing pairs of electrodes formed by a first selective pairing of the plurality of sensor electrodes have an increased sensitivity to a presence of an input object in comparison to

LGM-sensitive pairs of electrodes formed by a second selective pairing of the plurality of sensor electrodes that are primarily sensitive to the LGM condition;

the method comprising, while under the LGM condition:

prior to determining a first LGM term:

determining a size of the input object, and

depending on the size of the input object, selecting a spatial separation of the two sensor electrodes of a first of the LGM-sensitive pairs of electrodes,

determining the first LGM term using a mutual capacitance sensing with the first of the LGM-sensitive pairs of electrodes;

obtaining a first transcapacitance sensing signal for a sensing element formed by a first of the proximity-sensing pairs of electrodes; and

generating an LGM-corrected transcapacitance sensing signal by correcting the first transcapacitance sensing signal using the first LGM term.

16. The method of claim 15 , wherein obtaining the first LGM term comprises:

determining that the input object is located at the sensing element.

17. A method of capacitive sensing,

the method operating on a plurality of sensor electrodes disposed in a sensor electrode pattern, wherein, when under a low ground mass (LGM) condition:

proximity-sensing pairs of electrodes formed by a first selective pairing of the plurality of sensor electrodes have an increased sensitivity to a presence of an input object in comparison to

LGM-sensitive pairs of electrodes formed by a second selective pairing of the plurality of sensor electrodes that are primarily sensitive to the LGM condition;

the method comprising, while under the LGM condition:

determining a first LGM term using a mutual capacitance sensing with a first of the LGM-sensitive pairs of electrodes, wherein the first LGM term is in a first direction of the sensor electrode pattern, based on the first of the LGM-sensitive pairs of electrodes;

obtaining a second LGM term with a second of the LGM-sensitive pairs of electrodes, in a second direction of the sensor electrode pattern, perpendicular to the first direction;

obtaining a first transcapacitance sensing signal for a sensing element formed by a first of the proximity-sensing pairs of electrodes; and

generating an LGM-corrected transcapacitance sensing signal by correcting the first transcapacitance sensing signal using the first LGM term and the second LGM term.