Optical head structure

Details Optical head structure Optical head structure

1989-08-25

1992-06-30

Envall, Jr., Roy N.

Dynamic information storage or retrieval

With servo positioning of transducer assembly over track...

Optical servo system

369 4442, 369 4423, 369 4424, 369 4414, G11B 700

Patent

active

051269880

ABSTRACT:
An optical head structure, comprising: a light source; an optical system for projecting a first light beam from the light source upon an optical data recording medium and guiding a second light beam produced from the optical data recording medium as a result of projecting the first light beam, as a converging light beam; a light detecting element having at a photoelectric surface area divided into at least three surface parts, consisting of a central band part extending centrally and diametrally across the surface area and a pair of adjoining outer parts which are arranged on either side of the central band part, to receive the second light beam at a position in a path of the second light beam slightly displaced from a focal point of the second light beam; and a subtracter for producing a difference between an output from the central band part and a sum of outputs of the adjoining parts; the central band part being progressively narrower as it extends away from a central part of the photoelectric surface area. Thus, the sensitivity of focal error detection can be improved, and a desired linearity can be attained in the focal error detection property.

REFERENCES:
patent: 4881216 (1989-11-01), Deguchi et al.
patent: 4920527 (1990-04-01), Maeda
patent: 4929823 (1990-05-01), Kato et al.

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