Focus control method and focus controller

Details Focus control method and focus controller Focus control method and focus controller

2005-01-18

2005-01-18

Tran, Sinh (Department: 2697)

Dynamic information storage or retrieval

With servo positioning of transducer assembly over track...

Optical servo system

C369S044240, C369S044250

Reexamination Certificate

active

06845066

ABSTRACT:
The present invention aims to perform high-accuracy focus control in an optical disk drive, even if a solid immersion lens (SIL) or a solid immersion mirror (SIM) is set between an objective lens and the optical disk in order to increase a numerical aperture, by accurately detecting a change of the distance between an SIL or SIM and an optical disk.The present invention comprises light detection means (8) for detecting the light incoming to an SIL (2) or an SIM from an objective lens (1) at an incidence angle at which a numerical aperture is larger than 1 and reflected from a plane of the SIL (2) or SIM facing an optical disk, light detection means10for detecting the light incoming to the objective lens (1), comparison means (11) for finding a ratio between light amounts of the light detected by light detection means (8) and (10), and control means (11) for controlling operations of a focus actuator in accordance with the ratio.

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