| 摘要 |
PURPOSE:To attain fault observation in which the kind of fault is discriminated by including information concerning a faulty part in the record of a form alteration area and an optical constant alteration area or an area whose magnetic direction is different near the faulty part. CONSTITUTION:In an optical disk reproducing optical system, as soon as the faulty part 1 of the optical disk is detected and the kind of fault is decided, and immediately after the decision, a recording laser light beam modulated by the information about the fault records in a certain period so as to form a marking area 2. At the time of retrieving the fault position 1, the marking area 2 is retrieved first and the faulty part 1 can be found by tracing back the marking area 2 in a direction opposite to a recording direction. Moreover, it can be informed that a reproducing optical system and a signal process system decides what kind of fault the fault is.
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