| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical disk drive which can achieve focusing servo in multi-layer optical disk. SOLUTION: The drive includes a servo signal generating circuit generating FES (a-FES) by an astigmatic method and FES (d-FES) by a differential astigmatic method from a detected signal, and a FES switching processing circuit switching a-FES and d-FES, a control circuit controlling the FES switching processing circuit so that when a time at which focusing is started using a-FES is assumed to T1, after T1 a time at which seek is started during focusing is assumed to T2, switching from a-FES to d-FES is performed between T1 and T2, and a control circuit controlling the FES switching processing circuit so that after T2, when a time at which seek is finished during focusing is assumed to T3, and a time at which search is started again after T3 is assumed to T4, switching from d-FES to a-FES is performed between T3 and T4. COPYRIGHT: (C)2008,JPO&INPIT
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