METHOD AND APPARATUS FOR CONTROLLING MOVEMENT OF OBJECTIVE LENS

摘要

A control signal based on a focus error signal is masked to avoid the influence of an unnecessary light component during a period based on the moving speed of an objective lens at the time of layer jump. Subsequently, observation of the control signal based on the focus error signal is resumed and a brake signal is delivered to the objective lens thus turning a focus servo on. Accuracy of layer jump is thereby enhanced when an unnecessary lig ht component exists at the interlayer part of the focus error signal.