| 摘要 |
PURPOSE:To eliminate actually the generation of a focus error (DC component) due to the variance of optical distance between the disk reflecting surface and a pickup which is generated by the variance, etc. of thickness and reflective index of a recording disk, by using a delay compensating circuit having the DC gain set infinite. CONSTITUTION:A delay phase compensating circuit 9 is provided between an advance phase compensating circuit 2 and a driver circuit 3 as shown in the diagram. In other words, an operational amplifier OP1 having the DC gain set infinite logically is used as an inverse amplifier. The input of the circuit 9 can be set approximately at zero since the DC gain of the circuit 9 is set infinite. Therefore, the output of a focus error signal generator 1 is also set approximately at zero. That is, a shift degree can be compensated after eliminating actually the generation of the focus error signal. |
