| 摘要 |
PURPOSE:To prevent a focus lens from striking a disk surface by driving the lens so that when the lens approaches the disk surface too much, it separates from the disk surface. CONSTITUTION:A switch 10 is closed and a switch 11 is opened immediately after a circuit operates; and a signal from a lamp wave generator 7 is applied to an adder 13 and a focus lens approaches a disk recording surface gradually. When the focus lens passes through its focal point, i.e., a point F, the output K of a comparator 8 is inverted to a positive potential. The switch 11 is closed and an error detection signal serves as a focus-lens driving signal to attain normal servo operation. As the focus lens approaches the disk recording surface, the output G of a comparator 12 goes down to a negative potential and is applied to the adder 13, where it is added to the error detection signal to generate a large negative potential, thereby driving the focus lens so that it is forced to separate from the disk recording surface. |
