Low ground mass correction for capacitive imaging sensors

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.

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.

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.

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.

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.