| 摘要 |
PROBLEM TO BE SOLVED: To provide a highly reliable optical disk drive by preventing a condenser lens or the optical disk from being damaged in the manner of evading the collision of the optical disk with the condenser lens. SOLUTION: The optical disk drive is provided with light receiving areas of light beams divided in the almost concentric circular state, and a photodetector 21 is used for outputting a signal corresponding to the reflected light quantity from the optical disk. By a surface vicinity detector 61, the signals from each light receiving area of the photodetector 21 are summed up and the detecting signal continuously changing so that a focal point of the light beam has one maximum point in the part from a surface of the optical disk to an information surface, is outputted. The approaching state of the focal point of the light beam to the information surface of the optical disk 1 is discriminated by an information surface detector 62 by detecting the inclination of the detected signal. Since the approach of the optical disk to the condenser lens 14 is judged by the result of this discrimination, the collision of the optical disk 1 with the condenser lens 14 is prevented. COPYRIGHT: (C)2003,JPO
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