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:
Dec. 23, 2003
Filed:
Apr. 21, 2000
Koichi Maruyama, Saitama-ken, JP;
Hisashi Konno, Saitama-ken, JP;
Suguru Takishima, Saitama-ken, JP;
Wataru Kubo, Saitama-ken, JP;
Hiroshi Nishikawa, Saitama-ken, JP;
Hiroshi Yamamoto, Tokyo, JP;
Pentax Corporation, Tokyo, JP;
Abstract
An optical disc apparatus includes a fixed portion having a light source portion and a movable portion that holds an objective lens and moves along a radial direction of an optical disc. The fixed portion includes the light source portion for selectively emitting short and long wavelength laser beams, and a collimator lens for collimating the laser beams. The objective lens includes a positive refractive lens and a diffractive lens structure formed on a surface of the refractive lens. The diffractive lens structure has wavelength dependence such that spherical aberration varies in the undercorrected direction as wavelength of incident light increases. The objective lens converges the short wavelength laser beam of a predetermined diffraction order onto an informatlon layer of a thin cover type optical disc, and converges the long wavelength laser beam of the identical diffraction order onto an information layer of a thick cover type optical disc.