| 摘要 |
A laser beam reflected on a storage surface of a DVD is detected with a light-receiving device to allow a matrix circuit to generate a push-pull signal. The push-pull signal is converted into a binary signal, and a base-n counter, having an upper-limit count which is set to a certain value, counts the resulting signal. A count circuit 8e having a prescribed count time period counts a carry signal which is delivered by the base-n counter. Then, a detection factor is determined from the ratio of the count of the carry signal to the count time period. When the detection factor is below a prescribed value, the upper-limit count of the base-n counter or the count time period is adjusted to control the detection sensitivity. A judgment portion compares a plurality of detection factors with a prescribed threshold to find a determination rate or the ratio of the number of detection factors to be compared with to the number of detection factors which exceed the prescribed threshold. When the determination rate exceeds the prescribed determination threshold, the process determines that wobbles are formed on the information read and/or write media. The determination threshold is adjusted when the determination rate does not exceed the determination threshold.
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