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:
Oct. 28, 2008
Filed:
Dec. 23, 2004
Yu Kitahara, Saitama, JP;
Tetsuya Ori, Koshigaya, JP;
Toshiaki Katsuma, Tokyo, JP;
Masao Mori, Saitama, JP;
Hiromitsu Yamakawa, Saitama, JP;
Yu Kitahara, Saitama, JP;
Tetsuya Ori, Koshigaya, JP;
Toshiaki Katsuma, Tokyo, JP;
Masao Mori, Saitama, JP;
Hiromitsu Yamakawa, Saitama, JP;
Fujinon Corporation, Saitama, JP;
Abstract
An objective optical system includes a diffractive optical element on the light source side of an objective lens for focusing incident light of three different wavelengths with two different numerical apertures onto three different optical recording media. The diffractive optical element is formed of two lens elements made of different materials that are cemented together at a diffractive surface. Three conditions are satisfied so as to achieve optimum imaging. The diffractive surface may be shaped so that the order of the diffracted light of the shortest wavelength λhaving the largest diffracted intensity is different from the order of the diffracted light of the second wavelength λhaving the largest diffracted intensity, and the order of the diffracted light of the first wavelength λhaving the largest diffracted intensity is also different from the order of the diffracted light of the third wavelength λhaving the largest diffracted intensity.