| 摘要 |
PROBLEM TO BE SOLVED: To discriminate the kinds of a disk with less load in constitution. SOLUTION: The threshold value of a comparator 11A which compares a focus error signal FE within a focus servo circuit 7a with the prescribed threshold and outputs a focus zero cross signal FZC is made changeable over to a value for focus searching and a value for disk kind discrimination. In rising the focus servo, a controller 13A changes over the threshold of the comparator 11A to the prescribed value THF for focus search, then outputs a focus search signal and outputs the FZC signal rising down just before a laser beam emitted by an optical pickup 3 focuses at the signal plane of an optical disk 1. In discriminating the disk kind, the threshold of the comparator 11A is changed over for THD for disk kind discrimination and the focus search signal is outputted to monitor whether FZC goes to a high or not. The discrimination of whether the optical disk 1 is a CD or CD-R or CD-RW is thus made possible.
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