Lens actuating system for an optical disk drive having a driven mass for cancelling forces

摘要

A lens actuating system for an optical disk drive has an objective lens movably mounted in a movable frame with orthogonal X-, Y-, and Z- axes. A seeking servo moves the frame in the X-direction. A tracking servo moves the objective lens in the X-direction. A focusing servo moves the objective lens in the Z-direction. An optoelectronic sensor detects the relative position of the objective lens and frame in the X-direction, so that the tracking servo can maintain a fixed relative position during track-seeking, or in the Z-direction, to establish a neutral point on the Z-axis for the focusing servo. Force applied by the focusing servo or tracking servo to move the objective lens in one direction can be opposed by an equal and opposite force applied to a driven mass, so that a net zero force is transmitted to the frame.