Apparatus and method for focus control of read light irradiated

Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system

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369 4425, 369 4429, 369 4436, G11B 709

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active

061011576

ABSTRACT:
Apparatus and method for focus control are devised to cope with a fluctuation of an optimum gain of a focus servo loop due to a difference between light reflectance of recording surfaces or the like and to allow an optimum focal position of read light to preferably trace a target recording surface. The focus control apparatus of the invention includes: reading device for generating a read signal of a recording medium 1; a focus servo loop for allowing an optimum converging position of the read light to trace the target recording surface in accordance with a focus error signal FE by using a focusing actuator to displace the optimum converging position of the read light in the optical axial direction; a level detecting unit of the read signal; a level detecting unit of an error signal FE; amplifiers and of a read signal RF and the error signal FE; and a control unit for driving the actuator so as to allow the optimum converging position of the read light to approach the recording surface in the set-up mode and for controlling gains of the amplifiers so that a detection level by the detecting unit in the set-up mode reaches a predetermined level and a detection level by a detecting unit reaches a predetermined level.

REFERENCES:
patent: 5610886 (1997-03-01), Hayashi et al.
patent: 5682372 (1997-10-01), Yamakawa et al.
patent: 6011762 (2000-01-01), Watanabe et al.
patent: 6028826 (2000-02-01), Yamamoto et al.

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