Focus servo control device

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

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Details

369 54, G11B 7095

Patent

active

052028712

ABSTRACT:
A focus servo control device is provided with a focus search signal generating portion for generating a focus search signal whose first half cycle is short and whose second half cycle is long, a level detecting portion for detecting the level of a focus error signal when an object lens first passes near the focus point in response to the focus search signal, a gain adjusting portion for adjusting the focus servo gain based on the detected focus signal level, and a signal switch circuit for outputting a focus error signal instead of the focus search signal when the object lens reaches the focus point or the adjacency of the focus point for a second time in response to the focus search signal. The object lens is moved to a position where the focus servo control can be performed in response to the focus search signal, and then focused on the surface of a disc in response to the focus error signal in accordance with the distance between the object lens and the disc surface.

REFERENCES:
patent: 4866690 (1989-09-01), Tamaru et al.
patent: 5010538 (1991-04-01), Takeda et al.
patent: 5103439 (1992-04-01), Bierhoff et al.
patent: 5113384 (1992-05-01), McDonald et al.
patent: 5136566 (1992-08-01), Iwazaki
patent: 5146442 (1992-09-01), Skikichi
patent: 5157644 (1992-10-01), Rokutan

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