Patent ID: 7332847

Claim:
A method for driving an electret actuator comprising a fixed substrate having driving electrodes of a plurality of phases arranged therein; a movable element arranged on the fixed substrate and made electret in similar polarity at predetermined pitch in portions which face the driving electrodes; and drive controlling means for moving the movable element relative to the fixed substrate, the method comprising: a floating voltage pattern applying step of applying a pattern of voltage of the same polarity as that of the movable element, which has been made electret, to the driving electrodes; and a driving voltage pattern applying step of applying a pattern of voltage to the plurality of phases set at stages; wherein the floating voltage pattern applying step is carried out before the driving voltage pattern applying step by the drive controlling means; and wherein the driving electrodes on the fixed substrate have four phases, the movable element has electret areas having a width to face two of the driving electrodes of the fixed substrate, and the driving voltage pattern applying step applies the pattern of voltage in two-phase excitation.