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:
Apr. 27, 1999
Filed:
Oct. 16, 1996
Takashi Yoshizawa, Yokohama, JP;
Kabushiki Kaisha Toshiba, Kawasaki, JP;
Abstract
In an optical head unit, a shift of a laser beam is corrected by a parallel flat plate such that the center of an intensity distribution of the laser beam incident on an objective lens with a greatest numerical aperture among at least two objective lenses coincides substantially with the optical axis of the objective lens with the greatest numerical aperture. The parallel flat plate is disposed in an optical path of the laser beam traveling toward the lens such that a predetermined angle is defined between a surface of the parallel flat plate and the laser beam. Thereby, optical disks with different recording densities can be reproduced with high precision, without influence of the shift of the beam.