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:
Feb. 15, 2011
Filed:
Aug. 07, 2008
Masaharu Fukakusa, Miyazaki, JP;
Hideki Yoshinaka, Fukuoka, JP;
Mayumi Tsukamoto, Nagasaki, JP;
Satoshi Nagata, Fukuoka, JP;
Eizo Ono, Kumamoto, JP;
Masaharu Fukakusa, Miyazaki, JP;
Hideki Yoshinaka, Fukuoka, JP;
Mayumi Tsukamoto, Nagasaki, JP;
Satoshi Nagata, Fukuoka, JP;
Eizo Ono, Kumamoto, JP;
Panasonic Corporation, Osaka, JP;
Abstract
A light source emits light with a first wavelength and light with a second wavelength longer than the first wavelength toward an optical disk from adjacent positions. An optical receiver detects light reflected from the optical disk. An astigmatism-generating element generates light used for focus control in a condition where a focusing position on one of two perpendicular cross sections including an optical axis of the light reflected from the optical disk is located ahead of the optical receiver and a focusing position on the other cross section is located behind the optical receiver are included. The astigmatism-generating element is a Fresnel mirror configured to include a plurality of reflecting mirrors. A level difference between the reflecting mirrors adjacent to each other is distributed in a range from a depth of substantially (natural number/2) times the first wavelength to (natural number/2) times the second wavelength.