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:
Sep. 21, 2010
Filed:
Nov. 21, 2007
Koji Maezawa, Ibaraki, JP;
Aya Morishima, Ibaraki, JP;
Mitsuhiro Miyauchi, Ibaraki, JP;
Hitachi Maxell, Ltd., Ibaraki-shi, JP;
Abstract
A coupling lens for chromatic aberration correction is placed between a light source and an objective lens for focusing light beams with a plurality of wavelengths on an information recording surface of an optical recording medium, and at least one surface of the coupling lens includes a plurality of annular zones having a step concentric with an optical axis. The coupling lens is designed so that when a wavelength λ=380 to 430 nm and a height of the step is d=mλ/(n−1) where mis an actual number and nis a refractive index of the coupling lens at the wavelength λ, 9.9≦m≦10.1 is satisfied.