Method and apparatus for focusing servo control

Details Method and apparatus for focusing servo control Method and apparatus for focusing servo control

1986-12-09

1988-05-24

McElheny, Jr., Donald

Dynamic information storage or retrieval

Control of storage or retrieval operation by a control...

Mechanism control by the control signal

369 46, 369124, G11B 700, G11B 2022

Patent

active

047470895

ABSTRACT:
A focusing control method and apparatus employing a photodetector for generating a focusing error signal, a tracking error signal and an RF signal, and a closed loop focusing servo circuit responsive to the focusing error signal applied thereto for focusing a light spot in position on an optical disc. The focusing error signal is detected synchronously with the tracking error signal to produce a first periodic function signal. The focusing error signal is detected synchronously with the RF signal to produce a second periodic function signal. The tracking error signal is converted into a sin-wave signal having a predetermined amplitude. The RF signal is converted into a cos-wave signal having a predetermined amplitude. The first periodic function signal is multiplied by the cos-wave signal to produce a first component signal. The second periodic function signal is multiplied by the sin-wave signal to produce a second component signal. The first and second component signals are added to produce a composed disturbance signal. The composed disturbance signal is subtracted from the focusing error signal applied to the focusing servo circuit, thereby canceling a disturbance superimposed on the focusing error signal applied to the focusing servo circuit.

REFERENCES:
patent: 4163149 (1979-07-01), Sawano et al.
patent: 4446545 (1984-05-01), Van Dijk

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