| 摘要 |
PURPOSE:To improve the detection accuracy of the distance between a head and an optical disk by detecting the distance between the head and optical disk roughly by the 1st detecting mechanism and then detecting it accurately by the 2nd detecting mechanism. CONSTITUTION:The 1st detecting mechanism detects light emitted by a light emitting element 86a and reflected by a timing disk 85 by a photodetecting element 86b. Peaks of the detection level of the photodetecting element 86b in the rotation of the timing disk 85 are counted by a control part to detect the position of the head 48 roughly. The 2nd detecting mechanism, on the other hand, uses the focus mechanism composed of a projection lens 63 and a photodetector 64. The output waveform of the detection signal of the photodetector 64 has a constant pattern as the optical disk 5 rotates while rough position control is performed by the 1st detecting mechanism. The control part positions the head 58 accurately at invariably specific distance from the optical head 5 according to the relation between the pattern of the output waveform of the photodetector 64 and the distance between the optical disk 5 and head 48. |
