Adaptive mechanical change compensation for force detector
First Claim
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1. A method of operating a capacitive sensing device having a plurality of sensor electrodes and at least one force electrode, the method comprising:
- storing a baseline capacitance of the force electrode with no force applied to an input surface of the capacitive sensing device;
determining a first change in capacitance of the force electrode, relative to the baseline capacitance, caused by an input object contacting the input surface;
determining a mechanical change compensation factor associated with the capacitive sensing device by applying a pre-determined calibration force to the input surface and measuring a second change in capacitance of the force electrode in response to the pre-determined calibration force being applied to the input surface, wherein the mechanical change compensation factor comprises a ratio between the second change in capacitance to an arithmetic product of the pre-determined calibration force times an arithmetic sum of the baseline capacitance plus the second change in capacitance; and
determining force information for the force electrode based on at least the mechanical change compensation factor, and the first change in capacitance of the force electrode.
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Abstract
A capacitive sensing device is configured to detect force being applied to an input surface of the device by an input object, in addition to the position of the input object using touch sensing methods. Embodiments generate a compensation factor that is used to determine the force information in order to compensate for physical changes to the capacitive sensing device over time, air-gap non-uniform distribution, and other mechanical variations and changes.
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Citations
20 Claims
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1. A method of operating a capacitive sensing device having a plurality of sensor electrodes and at least one force electrode, the method comprising:
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storing a baseline capacitance of the force electrode with no force applied to an input surface of the capacitive sensing device; determining a first change in capacitance of the force electrode, relative to the baseline capacitance, caused by an input object contacting the input surface; determining a mechanical change compensation factor associated with the capacitive sensing device by applying a pre-determined calibration force to the input surface and measuring a second change in capacitance of the force electrode in response to the pre-determined calibration force being applied to the input surface, wherein the mechanical change compensation factor comprises a ratio between the second change in capacitance to an arithmetic product of the pre-determined calibration force times an arithmetic sum of the baseline capacitance plus the second change in capacitance; and determining force information for the force electrode based on at least the mechanical change compensation factor, and the first change in capacitance of the force electrode. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A processing system for a capacitive sensing device having an input surface, wherein the capacitive sensing device comprises at least one force electrode and a plurality of sensor electrodes, the processing system comprising:
a sensor module including sensor circuitry configured to be coupled to the plurality of sensor electrodes and the at least one force electrode, wherein the sensor module is configured to; store a baseline capacitance of the force electrode with no force applied to the input surface of the capacitive sensing device; determine a first change in capacitance of the force electrode, relative to the baseline capacitance, caused by an input object contacting the input surface; determine a mechanical change compensation factor associated with the capacitive sensing device by applying a pre-determined calibration force to the input surfaced and measuring a second change in capacitance of the force electrode in response to the pre-determined calibration force being applied to the input surface, wherein the mechanical change compensation factor comprises a ratio between the second change in capacitance to an arithmetic product of the pre-determined calibration force times an arithmetic sum of the baseline capacitance plus the second change in capacitance; and determine force information for the force electrode based on at least the mechanical change compensation factor and the first change in capacitance of the force electrode. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. A capacitive sensing device having an input surface, the capacitive sensing device comprising:
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at least one force electrode; a plurality of sensor electrodes; and a processing system coupled to the plurality of sensor electrodes and the at least one force electrode, the processing system comprising a sensor module having sensor circuitry, wherein the sensor module is configured to; store a baseline capacitance of the force electrode with no force applied to the input surface of the capacitive sensing device; determine a first change in capacitance of the force electrode, relative to the baseline capacitance, caused by an input object contacting the input surface; determine a mechanical change compensation factor associated with the capacitive sensing device by applying a pre-determined calibration force to the input surface and measuring a second change in capacitance of the force electrode in response to the pre-determined calibration force being applied to the input surface, wherein the mechanical change compensation factor comprises a ratio between the second change in capacitance to an arithmetic product of the pre-determined calibration force times an arithmetic sum of the baseline capacitance plus the second change in capacitance; and determine force information for the force electrode based on at least the mechanical change compensation factor and the first change in capacitance of the force electrode. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification