Separation-type optical information recording and reproducing ap

Details Separation-type optical information recording and reproducing ap Separation-type optical information recording and reproducing ap

1990-04-19

1992-09-29

Shaw, Dale M.

Dynamic information storage or retrieval

With servo positioning of transducer assembly over track...

Optical servo system

369 4411, 369 4441, 2502015, G11B 700

Patent

active

051518872

ABSTRACT:
An optical information recording and reproducing apparatus includes a separation type pick-up including a stationary unit having a laser diode for emitting a light beam, first and second beam splitters, first and second photodetectors and a focus error detecting optical element such as a critical angle prism and a cylindrical lens, and a movable unit having a reflecting member and an objective lens for projecting the light beam emanating from the stationary unit onto an optical record disk as a light spot and for directing a light beam reflected by the optical record disk to the stationary unit. The light beam reflected by the disk and received by the stationary unit is divided by the second beam splitter into first and second sub-beams, the first sub-beam being made incident upon the first photodetector having two light receiving regions arranged in the tangential direction of the disk via the focus error detecting optical element, and the second sub-beam being made incident upon the second photodetector having two light receiving regions aligned in the tangential direction. A difference signal derived from outputs of the light receiving regions of the second photodetector is subtracted from a difference signal derived from outputs of the light receiving regions of the first photodetector to generate an actual focus error signal from which an offset component is eliminated.

REFERENCES:
patent: 4819220 (1989-04-01), Miyazaki et al.
patent: 4959824 (1990-09-01), Ueda et al.
patent: 4977552 (1990-12-01), Gotoh
patent: 5050152 (1991-09-01), Honda
patent: 5060213 (1991-10-01), Kamisada

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