| 摘要 |
PROBLEM TO BE SOLVED: To avoid the collision of an objective lens with an optical disk in an optical disk device. SOLUTION: The first peak-hold circuit 31 and the second peak-hold circuit 32 each peak-hold an RF signal outputted by an RF processor, a differential circuit 33 generates the differential signal of the RF signal thus peak-held, a comparator circuit 34 compares it with a default value and generates a binary- digit RFdif signal, and a RFdif signal-detecting circuit 35 detects the RFdif signal, and then a focus-hold circuit 36 controls a biaxial actuator based on the RFdif and holds the objective lens.
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