Optical focus error control pickup device for an optical recordi

Details Optical focus error control pickup device for an optical recordi Optical focus error control pickup device for an optical recordi

1987-09-17

1989-08-29

Richardson, Robert L.

Dynamic information storage or retrieval

Specific detail of information handling portion of system

Radiation beam modification of or by storage medium

369 45, 369 46, 369124, G11B 735

Patent

active

048624462

ABSTRACT:
In an optical pickup device comprising an optical detector which is divided into first, second and third regions for detection of a light beam reflected from a disk, the detector is arranged in such a manner that the first region is located between the second and third regions and has a width determined so that the effects of diffracted light of the tracks on the disk are cancelled. Optical means give astigmatism and other aberrations to the light beam applied to the optical detector. A differential amplifier receives a first signal outputed by the first region and a second signal which is the sum of the output signals of the second and third regions, to form a focus error signal. Gain control means control the gain of at least one of the first and second signals to eliminate the resultant offset between the first and second signals. Thus, focus servo can be carried out with high accuracy at all times.

REFERENCES:
patent: 4296316 (1981-10-01), Tsuji et al.
patent: 4625303 (1986-11-01), Shikama et al.
patent: 4658391 (1987-04-01), Nozu et al.
patent: 4663750 (1987-05-01), Hamanaka et al.
patent: 4707648 (1987-11-01), Minami
patent: 4769801 (1988-09-01), Funada et al.

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