| 摘要 |
PURPOSE:To optimize the recording reproducing action of a reproducing exclusive-use optical (R/O) disk having a data recordable area by controlling the servo gain of a device based on a detected data field identifying flag. CONSTITUTION:For tracks of a data reproducing exclusive-use area 4 and a data recording area 3 of an optical disk 1, an optical sensitive recording member 7 is formed, for respective sector identifier parts ID, the address information of a sector is formed, and for a data field part DF of the area 4, the data the recorded by the uneven pit 8 as well as the ID. By loading the disk 1, a reading part 31 reproduces the ID with a laser light, reads the address information of the ID and a data field identifying flag from a reproducing signal 32 and outputs an address signal 33 and a flag signal 34. At a focus servo circuit 22, a focus error signal 24 is used, a signal 26 to drive a contraction lens in the direction where the signal 24 comes to be zero is outputted. The signal 34 changes over a gain so that the loop gain of a focus servo can be constant.
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