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:
May. 08, 2012
Filed:
Sep. 07, 2007
Akihiro Arai, Kyoto, JP;
Yoshiaki Komma, Osaka, JP;
Akihiro Arai, Kyoto, JP;
Yoshiaki Komma, Osaka, JP;
Panasonic Corporation, Osaka, JP;
Abstract
An optical head includes a diffraction element capable of improving the quality of a TE signal by a DPP method even if light amounts of two sub-spots are unbalanced for optical discs having different groove pitches. In a three-beam optical head, a diffraction element is divided in a radial direction of an optical disc into a first area, a second area and a third area, wherein the second area is further divided into a fourth area and a fifth area. The periodic structure of the first area is displaced from that of the fourth area by a ¼ period, the periodic structure of the third area is displaced from that of the first area by a ½ period, and the periodic structure of the fifth area is displaced from that of the third area by a ¼ period and from that of the fourth area by a ½ period.