Patent ID: 8106668

Claim:
A proximity detector for detecting approach of an object based on a stray capacitance, the proximity detector comprising: at least one differential electrode having an apparent stray capacitance that varies in response to an approaching object, the at least one differential electrode comprising a pair of electrodes having a positive element electrode and a negative element electrode; an individual capacitance detector for detecting an individual stray capacitance of the differential electrode based on stray capacitances of the pair of electrodes obtained by repeatedly charging and discharging the pair of electrodes at the same time in opposite phases, and by repeatedly charging and discharging the pair of electrodes at the same time in the same phase; and a proximity calculator for detecting the approach of the object based on the detected individual stray capacitance; wherein the individual capacitance detector comprises a capacitance sum detector that detects a sum of the obtained stray capacitances of the pair of electrodes, a capacitance difference detector that detects a difference between the obtained stray capacitances of the pair of electrodes, and an individual capacitance calculator that calculates a capacitance of each of the positive and negative electrodes based on the sum detected by the capacitance sum detector and the difference detected by the capacitance difference detector; and wherein the capacitance difference detector comprises a common-mode charger/discharger that charges and discharges the pair of electrodes in the same phase, and a capacitance difference accumulation unit that accumulates a characteristic of the charge/discharge in the common-mode charger/discharger for a plurality of times and that detects the electrostatic capacitances of the positive and negative electrodes to obtain the differences between the electrostatic capacitances.