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:
Jun. 22, 2010
Filed:
May. 23, 2006
Daisuke Koreeda, Saitama-ken, JP;
Koichi Maruyama, Tokyo, JP;
Shuichi Takeuchi, Saitama-ken, JP;
Hoya Corporation, Tokyo, JP;
Abstract
An objective lens, for an optical information read/write device that performs read/write operations on each of a plurality of optical discs using a corresponding one of three laser beams having first, second, and third wavelengths λ1, λ2, and λ3 (nm) satisfying a relationship λ1<λ2<λ3, respectively, includes a phase shift structure having a plurality of ring-shaped refractive surface zones into which at least one surface of the objective lens is concentrically divided. The objective lens is made of material with an Abbe number νd satisfying a condition 40≦νd≦80. The phase shift structure has a step between each couple of the adjacent refractive surface zones that gives an optical path difference to an incident laser beam, so that a condition 2N+1.00<|ΔOPD/λ1|<2N+1.30 is satisfied, where ΔOPD represents the optical path difference (nm) that the step gives to the laser beam with the first wavelength, and N represents a non-negative integer.