The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Aug. 16, 2005
Filed:
Sep. 10, 2002
Atsushi Kitamura, Iwata-gun, JP;
Kozo Matsumoto, Iwata-gun, JP;
Mizuki Nakamura, Iwata-gun, JP;
Motoji Egawa, Iwata-gun, JP;
Atsushi Kitamura, Iwata-gun, JP;
Kozo Matsumoto, Iwata-gun, JP;
Mizuki Nakamura, Iwata-gun, JP;
Motoji Egawa, Iwata-gun, JP;
Minebea Co., Ltd., Kitasaku-Gun, JP;
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.