| 摘要 |
PURPOSE:To attain a stable recording and reproduction from the same direction by detecting the number of the layers of the recording films at an arbitrary position after activation, operating a focus pull-in to the recording film to be reproduced, and operating a focus control and a tracking control, in a multilayer recording medium. CONSTITUTION:The rotation of an optical disk 1 is controlled by the command of a drive control circuit 13, and an optical head 3 is controlled to a reproduction power and transmitted to the middle periphery of the disk 1. Then, the path of an S-character number detecting circuit 21 is selected by an S-character number detecting circuit changeover switch 20 by a recording film number detecting command from the control circuit 13, and the S-speed waveform of the recording film is outputted by a driving signal for vibrating the lens of the head 3 up and down. The S-character is detected by an S-shaped comparator 16, the number is detected by the number detecting circuit 21, and the focus pull-in is operated at the arbitrary position. After the focus pull-in, it is switched to the focus gain and the tracking gain suited to the layer by switches SW 18 and 19 in order to operate the focus control and the tracking control. |
