| 摘要 |
PURPOSE: An optical disk is provided to record and reproduce different data items according to insertion direction. CONSTITUTION: An optical disk(101) includes a low-density data recording layer and a high-density data recording layer. When the disk is normally inserted into a recording and playing apparatus, data is recorded in the high-density data recording layer of the disk and reproduced from the high-density data recording layer(105). When the disk is turned and inserted into the recording and playing apparatus, data is recorded in the low-density data recording layer of the optical disk and reproduced from the low-density data recording layer. The low-density data is recorded and reproduced by an optical pick-up placed in close proximity to one side of the disk. The high-density data is recorded and reproduced by an optical pick-up located in close proximity to the other side of the disk.
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