| 摘要 |
PURPOSE:To retrieve a fault in a low magnification and to improve the efficiency in observation of the fault by using an optical system to retrieve a form alteration area, an optical constant alteration area or an area whose magnetic direction is different, near the position of the fault recorded on an optical disk by using a microscope, and retrieving the position of the fault. CONSTITUTION:Just after the faulty part 1 of the optical disk is detected in the reproducing optical system of the optical disk, recording a certain period to form alteration area, the optical constant alteration area or a marking area 2 which is the area whose magnetic direction is different, for recording near the position of the fault detected in the reproducing optical system of the optical disk. At the time of retrieving the position of the fault, the marking area 2 is retrieved first and the faulty part 1 can be easily found by tracing the marking area in a direction opposite to a recording direction. Thus, the efficiency of the observation of the faults can be improved.
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