Touch sensor device and capacitance calibration method

1. A touch sensor device, comprising:

a plurality of capacitance sensors arranged on a touchscreen;

a touch determination processor that determines whether the touchscreen is in a touched state or a non-touched state based on capacitance detected by each of the capacitance sensors;

a calibration processor that calibrates the capacitance;

a delay processor that delays the calibration processor over a specified period after the touch determination processor determines that the touchscreen is in the non-touched state; and

a residual capacitance determination unit that monitors the capacitance while delaying and after delaying the calibration and determines whether a residual capacitance in the non-touched state resulted from a parasitic capacitance or a touch capacitance,

wherein the calibration processor calibrates the capacitance when the residual capacitance determination unit determines that the residual capacitance resulted from the parasitic capacitance, and

wherein the residual capacitance determination unit

obtains a capacitance in a present non-touched state after the specified period elapses from when determined that the touchscreen is in the non-touched state,

compares an absolute value of a capacitance difference between the capacitance in the present non-touched state and a capacitance in a preceding non-touched state with a lower limit threshold value, and

determines whether the residual capacitance resulted from the parasitic capacitance based on the comparison result.

2. The touch sensor device according to claim 1 , wherein the specified period is set to a duration for determination that a user is successively performing intermittent touch operations.

3. The touch sensor device according to claim 1 , wherein the calibration processor does not perform calibration of the capacitance when the residual capacitance determination unit determines that the residual capacitance did not result from the parasitic capacitance.

4. The touch sensor device according to claim 1 , wherein the calibration processor does not perform calibration of the capacitance when the capacitance changes to a value that exceeds a re-touch determination threshold value while delaying calibration over the specified period.

5. A method for calibrating capacitance of each of a plurality of capacitance sensors arranged on a touch sensor device, the method comprising:

determining whether a touchscreen is in a touched state or a non-touched state based on the capacitance detected by each of the capacitance sensors;

delaying calibration of the capacitance over a specified period after determining that the touchscreen is in the non-touched state;

determining whether a residual capacitance in the non-touched state resulted from a parasitic capacitance or a touch capacitance by monitoring the capacitance while delaying and after delaying the calibration; and

calibrating the capacitance when determining that the residual capacitance resulted from the parasitic capacitance,

wherein the determining whether a residual capacitance in the non-touched state resulted from a parasitic capacitance or a touch capacitance includes:

obtaining a capacitance in a present non-touched state after the specified period elapses from when determined that the touchscreen is in the non-touched state;

comparing an absolute value of a capacitance difference between the capacitance in the present non-touched state and a capacitance in a preceding non-touched state with a lower limit threshold value; and

determining whether the residual capacitance resulted from the parasitic capacitance based on the comparison result.

6. A non-transitory machine readable memory medium that stores one or more programs executed by one or more processors, the one or more programs comprising instructions causing the one or more processors to execute the method of claim 5 .