| 摘要 |
PURPOSE:To prevent the breakdown of a data being on a recording/reproducing surface, even in case when power exceeding a prescribed value is generated due to an overshoot at the time of light emission of a laser power, or a circuit abnormality, etc., by starting a light source after keeping a stop-down optical system apart from a recording medium. CONSTITUTION:First of all, a motor is started and thereafter a lens system is moved in a lower direction immediately and kept apart from a disk. By lowering a lens enough before starting a laser when the laser is activated (shown by a dotted line B), the focus of an objective lens does not conform with the recording/reproducing surface, therefore, the recording/reproducing surface is not broken down at all. Thereafter, before an automatic focus control is started, the lens is raised gradually and brought closed to the disk, that the focus and the recording/reproducing surface are made coincident with each other is confirmed and the automatic focus control is started. Accordingly, an error signal for detecting a shift from the focus goes into a linear area when the control is started, after a signal having a large S-character characteristic is generated before the automatic focus control is started, and the error signal is scarcely generated. |
