| 摘要 |
PURPOSE:To detect accurately the revolving angle of an optical disk and to improve the recording/reproducing reliability, by providing a revolving angle detecting mark corresponding to a data recording part of a track to a spacer held between transparent disks. CONSTITUTION:Spacers 14 and 18 are held between inner/outer circumferential parts of two transparent disks 20 and 20', and cuts 32 and 32A are formed at the outer circumference edge of the spacer 14 at angles corresponding to the sector marks of the data recording parts of each track. The cut 32A is discriminated from other cuts 32, and a line D connected to a center line O is defined as an absolute base point of the disk. In a recording/reproducing mode those cuts 32 and 32A are read optically by a light emitting diode 28 and a photodetecting element 30 for accurate detection of both the revolving angle and revolving speed of the disk. Therefore the revolving angle can be detected accurately even though a catching action is incomplete. This ensures the recording/reproducing actions of data with high accuracy. |
