Harutaka Sekiya

Stabilization of Focus Servo System for High-Speed Access in a 90 mm MO Disk Drive

Stability of a focus servo system was studied in a 90 mm magneto-optical (MO) disk drive that uses a separated optical system for high-speed access. The separated optical system had two major problems of focus servo system instability-one is caused by a mechanical feedback (MFB) due to mechanical resonance of a disk and the other is caused by a complex feed-back of both mechanical and optical crosstalks. The mechanisms of these problems are clarified, and high-speed access of less than 30 ms is achieved. In this paper, the mechanisms are discussed and effective solutions are presented.