Patent ID: 7227294

Claim:
An arrangement for electrically driving a piezoelectric transducer to mechanically oscillate a mirror at a mechanical resonant frequency in opposite circumferential directions about an axis, comprising: a) an inductor having an inductance electrically connected to the transducer having an inherent capacitance to form a series resonant circuit having an electrical resonant frequency which is greater than the mechanical resonant frequency throughout variations in temperature, ageing and tolerances of the transducer and the inductor; b) means for driving the resonant circuit with an electrical drive signal having a drive frequency which differs from the electrical resonant frequency by a parameter, the driving means including a bridge circuit having two arms connected across a supply of DC voltage, each arm having a pair of actuatable switches and a junction therebetween, the series resonant circuit being connected between each junction of the arms; and c) means for adjusting the parameter to make the drive frequency correspond to the mechanical resonant frequency to oscillate the mirror at the same angular speed in both the circumferential directions and to compensate for said variations in the electrical resonant frequency, the adjusting means including a controller for cyclically controlling actuation of the switches, at least one of the switches being actuated at a different time than another of the switches, the different time being the parameter to be adjusted.