| 摘要 |
PURPOSE:To operate a focus servo function by an information recording part of an optical disk by closing a servo loop when a servo loop switching means decides a position detection signal from a position detection means detecting the position of an actuator in the range of servo loop. CONSTITUTION:A servo loop switching means consists of a servo signal processing circuit 2A, a loop switching circuit 4A and a position detection circuit 9. The position detection signal 13 of the actuator 6 detected and outputted by a position detection sensor 8 is changed linearly according to the servo loop range stored in advance in a servo signal processing circuit 2A corresponding to the position of the actuator 6. The servo signal processing circuit 2A monitors the position detection circuit 9 to recognize whether the position of the actuator 6 is between the upper and lower limit of the servo loop range or not and outputs a position circuit output signal 16 when the position is within the range. The loop switching circuit 4 is thrown to the position of a terminal A by the position circuit output signal 16 to control the focus servo function. |
