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. 22, 1990
Filed:
Apr. 26, 1989
Yasuhiro Tanaka, Ashiya, JP;
Masaaki Sunohara, Nishinomiya, JP;
Yasuo Nakajima, Ibaraki, JP;
Shinichi Tanaka, Kyoto, JP;
Matsushita Electric Industrial Co., Ltd., Osaka, JP;
Abstract
A lens controls the chromatic aberration of an objective lens for practical use in an optical disk system. The lens has first and second aspherical surfaces each providing a positive refractive power for focusing a light through a transparent plate and satisfies a condition: ##EQU1## where f.sub.L =focal length of the lens, d.sub.c =thickness of the transparent plate, n.sub.c =refractive index of the transparent plate, .lambda.=center wavelength of the light, NA=numerical apperture of the lens, .nu..sub.L =local dispersion of the lens, and .nu..sub.c =local dispersion of the transparent plate. The local dispersion of each element is expressed by: ##EQU2## where n.sub.80 is refractive index at a center wavelength .lambda. nm, n.sub..lambda. +5 a refractive index at .lambda.+5 nm, and n.sub..lambda. -5 a refractive index at .lambda.-5 nm.