Optical information recording and reproducing apparatus...

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

Reexamination Certificate

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Details

C369S044320, C369S053190

Reexamination Certificate

active

07843774

ABSTRACT:
An optical information recording and reproducing apparatus for performing, using a light beam, recording of information or reproducing of recorded information with respect to a plurality of recording layers of an information recording medium. An objective lens condenses a light beam onto the recording layers. A light beam expander corrects spherical aberration caused by a difference in substrate thickness by changing one of a divergent angle and a convergent angle of a light beam entering the objective lens. A coma aberration correcting device corrects coma aberration caused by tilt of the recording medium. A drive circuit drives the coma aberration correcting device with a drive signal having a value varied depending on an amount of coma aberration caused in accordance with one of a divergent angle and a convergent angle of the light beam expander, which varies for each recording layer, and an amount of coma aberration caused in each recording layer due to a transmission thickness from a light incidence surface of the recording medium to the recording layers.

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Japanese Office Action dated Aug. 31, 2010, issued in counterpart Japanese patent application No. 2008-21126, with an English translation.

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