| 摘要 |
PROBLEM TO BE SOLVED: To provide a focus control technique of laser light for an optical disk, for attaining stable pulling-in of a focus by reducing bad influence by stray light. SOLUTION: In the laser focus control for controlling the focus position of the laser light, by obtaining reflected light which can be acquired by irradiating the loaded optical disk with the laser light, the pulling-in of the focus is carried out by detecting beforehand, unwanted light gain higher than a normal operation gain of an electrical signal, obtained on the basis of the light reflected from the loaded optical disk, while performing focus sweep operation of the laser light, in a direction sequentially approaching to the recording surface of the optical disk, counting the number of signals produced due to the unwanted light; thereafter, detecting the electrical signals obtained, on the basis of the light reflected from the loaded optical disk, and using an electrical signal, immediately after the number of the detections reaches the number of the signals produced due to the unwanted light, as the signal of the recording surface of the loaded optical disk. COPYRIGHT: (C)2008,JPO&INPIT
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