| 摘要 |
PURPOSE:To increase the gain of a focus control system to the low band component of a DC disturbance which is due to a shift of a disk produced by its attachment, the warp of the disk, etc. and applied to the focus control system, by incorporating an integrator to the focus control system. CONSTITUTION:The light beam of a light source 1 is focused and irradiated to a disk 7 which is capable of optical record and reproduction. The focusing state of the light beam on the disk 7 is detected by the output of a differential amplifier 11, and a driving circuit 14 is driven so that the light beam has a fixed focusing state on the disk 7 in response to the detection output of the amplifier 11. The output of the amplifier 11 is supplied to an integration circuit 25 after passing through a phase compensating circuit 12. The circuit 25 is provided with an operational amplifier 26 having sufficiently large input impedance and gain, resistances 27 and 28, and a capacitor 29. Thus the low band gain of a focus control system is increased with reduction of a focus control error. |
