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:
Jul. 26, 2011
Filed:
Mar. 15, 2010
Applicants:
Jun-ichi Asada, Hyogo, JP;
Kazuo Momoo, Osaka, JP;
Inventors:
Jun-ichi Asada, Hyogo, JP;
Kazuo Momoo, Osaka, JP;
Assignee:
Panasonic Corporation, Osaka, JP;
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
G11B 7/00 (2006.01);
U.S. Cl.
CPC ...
Abstract
An optical pickup includes a wave plate on an optical path to be followed by every light beam emitted from three light sources (with wavelengths λ, λand λ, respectively) both on their way toward an optical disc and back from the disc toward a photodetector. The wave plate has two layers with different retardations and different optic axis directions. The sum of the retardations of the first and second layers is defined to be approximately,andto the light beams with the wavelengths λ, λand λ.