| 摘要 |
PROBLEM TO BE SOLVED: To provide a disk player provided with a pre-pit detection circuit preventing a lowering of a pre-pit detection margin due to a detection delay, having high detective precision and resistant to a noise. SOLUTION: A photodetector receiving a reflection beam from a DVD-RW (rewritable) is divided into four areas of A, B, C, D, and respective areas output detection signals. A delay ofΔt appears for a pre-pit on the disk by a characteristic of a phase pit. First of all, after difference signals between A-C and D-B are respectively obtained, a phase difference pulse showing a phase difference between both is generated, and after it is integrated, it is held by a sample pulse outputted accompanying the 14T space detection, and a control voltage proportional to the phase difference is generated. A delay time of a voltage control delay line is controlled by the control voltage, and a correction signal (D-B)' delaying the difference signal D-B is obtained. Then, by outputting a pre-pit detection signal (A-C)+(D-B)', a detection margin m is secured, and an effect due to the fluctuation of the noise, etc., is reduced.
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