A piezoelectric actuator with a motion-decoupling amplifier for optical disk drives

Abstract

In this paper, an optical pick-up actuator is studied using a multilayered PZT (lead-zirconate-titanate) for possible application to slim and small-form-factor optical disk drives or mobile devices. A theoretical modeling and analysis of the PZT actuator including the dynamics of piezoelectric, electrode and substrate layers are performed to estimate the dynamic properties such as natural frequencies, resultant forces and maximum displacements. In particular, we suggest a novel stroke-amplifying structure enabling the decoupled tracking and focusing motions actuated by four parallel multimorphs. A flexure hinge mechanism is used as the displacement amplifier to extend the allowable stroke of the actuator. Experimental results using a cantilever actuator agree well with the analytical predictions. Based on the theoretical and experimental investigations, we have designed the final model of the optical pick-up actuator with a height of 2.5 mm, showing that the moving range is +/- 400 mu m at 15 V in the focusing direction, which is appropriate for slim or small-form-factor optical disk drives.