| 摘要 |
PURPOSE:To execute extensively and surely the pull-in of a focussing lens irrespective of the original position of the lens of an optical pickup, by moving reversely the lens of the optical pickup once moved to an external area, to a focussing condition. CONSTITUTION:A focus error signal alpha obtained by processing the output of a focus sensor 57 and having a value corresponding to the distance between a disk and lens is passed through an offset switching device 4, where an offset quantity is removed from the signal alpha, and inputted into a focus servo switch 2 after the signal alpha is compensated by a gain-phase conpensating circuit 1. On the other hand, a focus pull-in start signal gamma for starting the focus pulling-in operation is generated at a focus pull-in start signal generator S which is used as an ON/ OFF signal generating means. The output of the focus pull-in starting signal circuit 5 which is used as a moving signal generating means is superimposed on the output of the focus servo switch 2 and inputted to an actuator driving circuit 3. By the output beta of the actuator driving circuit 3, the actuator 55 of a condenser lens is driven. |
