Tracking Servo For Small Size Optical Disk System.

Abstract

This paper describes a tracking servo system developed for a small size optical disk system. In this tracking servo system, new techniques, such as two stage servo system and tracking error integration memory, are applied for improving track access time and data transfer rate. The two stage tracking servo system has a unique position detector, which outputs a lens position error signal relative to the optical head. Using this detecting signal, the objective lens and the optical head are controlled co-operatively. Therefore direct track access from the current track to the target track is achieved without lens vibration. Also, average track access time is reduced. The tracking error integration memory integrates track error signal synchronized with disk rotation. This memory output signal is equivalent to track eccentricity after several disk rotations. Therefore, a tracking servo system with this tracking error integration memory can achive highly accurate track following even under highspeed disk rotation and large track eccentricity. As a result, disk rotation speed can be upped and data transfer rate can be improved.