| 摘要 |
PURPOSE:To record and reproduce high-density information by providing a means which detect a tracking signal independently from two of three beam spots and a means which switches operations of the detecting means according to recording areas. CONSTITUTION:When information is recorded in a recording area 41, a clock track 21, the recording area 41, and a tracking track 31 are irradiated with spots S1, S2, and S3 respectively. Those spots are scanned as shown by an arrow (a). Reflected light from the spot S1 strikes a photodetector 17 to reproduce a clock signal and reflected light from the spot S3 is incident on a photodetector 19 to detect a tracking signal. Automatic tracking is carried out with this tracking signal to record recording pits 5 in the recording area 41 accurately with the spot S2. Then when information is recorded in a recording area 42, the spot S1 scans the tracking track 31 and the spot S3 scans a clock track 23 to switch operations of the detecting means. Thus, high-density information is recorded and reproduced with high precision.
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