Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Patent
1989-08-23
1991-11-12
Envall, Jr., Roy N.
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
369109, 369 4441, 359569, G11B 700
Patent
active
050653806
ABSTRACT:
An optical pickup device for focusing an irradiating ray from a light emitting element on a recording medium and letting a reflected ray reflected from this recording medium focus on a light receiving element is characterized in comprising a diffracting element disposed before the light emitting element and the light receiving element, at least a first diffraction region included in the diffracting element for separating the irradiating ray from the light emitting element into a main beam and sub-beams shifted from the main beam in a direction perpendicular to a track direction of the track where the main beam is focused, a second diffraction region included in the diffracting element for directing a reflected ray of the main beam reflected from the recording medium onto a main light receiving element and directing reflected rays of the sub-beams onto sub-light receiving elements, and an arithmetic circuit for detecting a tilt error signal showing the sub-beam's focusing condition according to the output of the sub-light receiving elements, whereby an optical pickup device does not require installment of any separate tilt sensor for detection of a tilt signal, and also enables prevention of increasing the number of components and the increase of cost as a result of increased assembly steps and/or the required man-hours.
REFERENCES:
patent: 4425034 (1984-01-01), von Rosmalen
patent: 4733065 (1988-03-01), Hoshi et al.
patent: 4945529 (1990-07-01), Ono et al.
patent: 4983017 (1991-01-01), Tsuji et al.
Envall Jr. Roy N.
Sharp Kabushiki Kaisha
Tran Thang V.
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