A piezoelectric actuator for operating a mechanical component, in particular for an injector for metering fuel in an internal combustion engine, is proposed in which one head part and one foot part are present, between which a piezoelectric element is clamped in the direction of operation. The calibration system includes an autocollimator detecting the inclined angle of the stage of a disc drive. With the present invention, redundancy of channel configuration may be decreased, channel configuration of the conventional art is simplified, hence reducing resource occupancy and improving resource utilization of channels. Another viewability-enhancing features is the use of polarizing elements having substantially matched bandwidth responses andor comprising an achromatic design.