| 摘要 |
PURPOSE:To obtain a servo to be locked surely by giving a signal driving an objective lens in the servo pulling-in direction before the closing of a start switch at the servo start to an objective lens driver. CONSTITUTION:In closing a switch 19, a drive signal of a prescribed voltage from a constant voltage circuit 18 is applied to the objective lens driver 15, i.e., a power amplifier 14. The polarity, magnitude and applied time of the drive signal are selected so that a focus actuator 13 moves the objective lens 4 to a position spaced sufficiently from an optical disk 3. A sequence circuit 20 opens the switch 19 at a prescribed time after the switch 19 is closed to close a start switch 16. An output E of a differential amplifier Ef is positive at this point of time, a signal bringing the objective lens 4 close to the optical disk 5 is applied to the focus actuator 13 to complete pulling-in to a focused point B. Even if the initial position of the objective lens 4 exists in any position, the lens is driven to a position to be pulled in at the closing of the start switch 16. |
