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:
Aug. 26, 2003
Filed:
Aug. 02, 2002
Takeshi Shimano, Hachioji, JP;
Kenchi Ito, Hachioji, JP;
Yooji Maruyama, Iruma, JP;
Hiroyuki Awano, Nagareyama, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
An optical head including a semiconductor laser source, a condenser lens, a photodiode for detecting a laser light emitter from said semiconductor laser source, and an optical coupler unit for collecting the laser light to the photodiode. A chromatic aberration W of condenser lens is satisfied by an expression W(h, NA)={(NA) &Dgr;&lgr;/4&lgr;}h, where h is a height of incident light from an optical axis on a hologram, NA is a numerical aperture, &Dgr;&lgr; is a wavelength fluctuation, and a &lgr; is a wavelength at recording. The height h is determined so that the chromatic aberration W becomes equal to or less than &lgr;/4.