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:
Nov. 16, 2010
Filed:
Apr. 12, 2007
Koichi Murata, Tokyo, JP;
Yoshiharu Ooi, Tokyo, JP;
Koichi Murata, Tokyo, JP;
Yoshiharu Ooi, Tokyo, JP;
Asahi Glass Company, Limited, Tokyo, JP;
Abstract
An optical head apparatus includes a light source and an objective lens focusing a light source light on an optical recording medium. Also included is a light detector receiving a return light, and a variable diffraction device including a first polarized light diffraction grating; and a second polarized light diffraction grating. Provided that a polarizing direction diffracted by the first polarized light diffraction grating is defined as a first polarizing direction and a polarizing direction that is orthogonal to the first polarizing direction and not diffracted by the first polarized light diffraction grating is defined as a second polarizing direction, a ratio obtained from dividing a diffraction efficiency in the second polarizing direction by a diffraction efficiency in the first polarizing direction, of the first polarized light diffraction grating, is 0 to 0.5, and a ratio obtained from dividing a diffraction efficiency in the first polarizing direction by a diffraction efficiency in the second polarizing direction, of the second polarized light diffraction grating, is 0 to 0.5.