| 摘要 |
PROBLEM TO BE SOLVED: To perform stable high-density signal recording/reproducing by preventing a collision between an objective lens and a disk without making any special change of a photodetector or the like even if recording/reproducing is carried out in the disk of large surface wobbling or warpage by using the objective lens of a narrow working distance. SOLUTION: The high-frequency component of the output signal of a focus control circuit 12 is attenuated by an LPF 4, and inputted to a comparator circuit 15 to be compared with the output of a reference voltage circuit 16. When the result of the comparison is not in a predetermined reference voltage range, the focus control circuit 12 is not operated, but an objective lens retreating circuit 19 is operated to move an objective lens 3 away from an optical disk 1. COPYRIGHT: (C)2006,JPO&NCIPI
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