Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Reexamination Certificate
2005-08-16
2005-08-16
Young, W. R. (Department: 2653)
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
C369S112220, C369S112060
Reexamination Certificate
active
06930962
ABSTRACT:
An optical information reading apparatus includes a semiconductor laser, a beam splitter, a collimating lens, a super-resolution cut-off filter, an objective lens having a high numerical aperture, and a photodetector. The super-resolution cut-off filter is disposed immediately in front of the incident side of the objective lens. The photodetector is a well-known eight-division photodetector with a signal processing circuit, reads recorded information and also outputs tracking and focusing control signals to a control circuit. The laser beam is separated into a 0-th order laser beam and ± primary laser beams, which are made incident on the objective lens, pass therethrough, and are made incident on the recording surface of a disk. The 0-th order laser beam is used to read information and to control focussing while the ± primary laser beams are used to control tracking.
REFERENCES:
patent: 6660986 (2003-12-01), Matsumoto et al.
patent: 08077592 (1996-03-01), None
Egawa Motoji
Kitamura Atsushi
Matsumoto Kozo
Nakamura Mizuki
Minebea Co. Ltd.
Oliff & Berridg,e PLC
Pham Van
Young W. R.
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