| 摘要 |
PURPOSE:To dissolve a locked loop, by superposing a bias, which is moved in the transportation direction of an optical pickup, to servo loops of the tracking servo and the transporting servo of the optical pickup. CONSTITUTION:A tracking error signal is supplied to a terminal 1 and is supplied to a tracking coil 4 through a resistor 2 and a servo amplifier 3. At reproducing and fast-forwarding time, a positive bias voltage 11 is connected to the amplifier 3 through a fixed contact 10a of a switch 10. If the positive bias is applied when an input signal shown by A in Fig. at reproducing and fast- forwarding time, the input signal of the amplifier 3 is shown by C in Fig. In Fig., (c) is the bias level, and Ranges (a) and (b) indicate the period when the servo loop is opened. Consequently, since the output signal has always the positive direction even if the servo loop is opened because of a drop-out or the like, the pickup is always deflected to the outside circumference and the inside circumference, and the locked loop is not generated. |
