Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Patent
1996-01-30
1997-10-07
Tran, Thang V.
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
369 4429, 369 4432, 369 4435, G11B 7095
Patent
active
056755619
ABSTRACT:
An optical disc reproducing apparatus of the present invention has an objective lens for focusing light from the light source on a disc surface as a light spot, a focus actuator for driving the objective lens in the vertical direction to the disc surface, a light detector for converting the reflected light from the disc surface into electric signal, a focus error signal generator for generating a focus error signal representing a vertical deviation of the focal point from the disc surface based on the output from the light detector, a first comparator for detecting the focus error signal level in excess of a first reference level as the defocus representing signal by comparing the focus error signal with the predetermined first reference level, an area weighted average reflected light intensity detector for detecting an area weighted average reflected light intensity from the disc surface based on the output from the light detector, a second comparator for comparing the area weighted average reflected light intensity with a predetermined second reference level, and a lens evacuator for driving the focus actuator to evacuate the objective lens from the disc surface when it is detected by the second comparator that the area weighted average reflected light intensity has decreased below the second reference level within a prescribed period of time after the defocus representing signal has been detected by the first comparator.
REFERENCES:
patent: 4541084 (1985-09-01), Oku et al.
patent: 4733066 (1988-03-01), Komo et al.
patent: 4769801 (1988-09-01), Funada et al.
patent: 5060215 (1991-10-01), Kawamura et al.
patent: 5361246 (1994-11-01), Tominaga
Kabushiki Kaisha Toshiba
Tran Thang V.
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