| 摘要 |
PURPOSE:To attain highly accurate focus control by repeating holding and releasing of a focus error signal by a holding circuit according to specified level of a tracking error signal. CONSTITUTION:When a pickup 20 is moved, a tracking error signal 15 becomes as shown in the figure. At this time, a groove crossing detecting circuit 22 outputs a signal 23 that indicates that the extent is crossed, and a signal 24 that indicates that the tracking error signal is zero. A normal close contact switch 17, a normal open contact switch 25 and a holding circuit 26 operate responding to signals 23, 24. The pickup 20 moves to other recording tracks or detects flaws etc. on the disk surface. When a tracking error signal exceeds the limits of +V, -V, the signal 23 is outputted from the groove crossing detecting circuit 22, and the switch 25 becomes the closed state, and the switch 17 becomes the open state. Accordingly, a focus error signal held by the holding circuit 26 is inputted as a focus error signal to a phase compensation circuit 18 and a driving circuit 19 of the pickup. |
