Proximity deciding device and proximity deciding method

Abstract

A proximity deciding device includes: a capacitive sensor electrode covered with a cover having a manipulation surface; a measurement circuit that measures capacitance between the capacitive sensor electrode and an indicating body; a proximity deciding unit that makes a decision as to whether a proximity state is in progress according to a difference obtained by subtracting a reference value from the capacitance; and a correcting unit that corrects the reference value. The correcting unit stores, in a storage unit, a lower limit, for accumulated inputs, based on the reference value before the proximity state; calculates, in the proximity state, a cumulative value for a change of the capacitance; updates the reference value according to a cumulative input value (cumulative value or lower limit); and sets the cumulative input value to the cumulative value or lower limit according to whether the cumulative value is larger or smaller than the lower limit.