Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Patent
1995-11-02
1997-06-24
Young, W. R.
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
369 4426, 369 54, G11B 700
Patent
active
056423420
ABSTRACT:
A first servo unit controls a rotational speed of an optical disc using a reproduced signal obtained as a result of reading a signal previously written on the optical disc. A second servo unit controls rotation of the optical disc using a rotation detection signal obtained as a result of measuring a rotational speed of a disc motor which drives the optical disc. A determining unit determines that the second servo unit is to perform a disc-rotation-speed control operation when it is determined that a disc-rotation-speed control operation performed by the first servo unit is not possible. The determining unit determines that the first servo unit is to perform the disc-rotation-speed control operation when the rotation speed of the optical disc is a predetermined one. The optical disc has a plurality of recording regions, the plurality of recording regions having different recording modes for recording signals therein such that a polarity of the reproduced signal relevant in a tracking control operation is different in response to a change of a currently scanned recording region among the plurality of recording regions. The determining unit further changes the polarity of the reproduced signal relevant in the tracking control operation when it is determined that the disc-rotation-speed control operation performed by the first servo unit is not possible.
REFERENCES:
patent: 4542423 (1985-09-01), Kotake et al.
patent: 4815063 (1989-03-01), Aoshima et al.
patent: 5109369 (1992-04-01), Maeda et al.
patent: 5351132 (1994-09-01), Sawabe et al.
Japanese journal, "Rado Technique", for Mar. 1993, pp. 165-180, All of Sony MD (Mini-Disc) Technique.
Meller Michael N.
Teac Corporation
Young W. R.
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