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:
Nov. 23, 2010
Filed:
Sep. 28, 2006
Daisuke Koreeda, Saitama, JP;
Koichi Maruyama, Tokyo, JP;
Shuichi Takeuchi, Saitama, JP;
Yoshiyuki Tashiro, Tokyo, JP;
Daisuke Koreeda, Saitama, JP;
Koichi Maruyama, Tokyo, JP;
Shuichi Takeuchi, Saitama, JP;
Yoshiyuki Tashiro, Tokyo, JP;
Hoya Corporation, Tokyo, JP;
Abstract
There is provided an optical disc drive for recordation/reproduction for three types of optical discs by selectively using one of three types of light beams. The optical disc drive comprises an objective lens. The objective lens has a step structure which gives an optical path length difference to an incident beam at each step. When the third laser beam passes through the objective lens, the objective lens produces normal diffraction order light converging to a recording surface of the third optical disc and undesired diffraction order light converging to a point deviating from the recording surface of the third optical disc. A distance from a point to which the normal diffraction order light converges to a point to which the undesired diffraction order light converges is larger than or equal to twice a pull-in range of a focus error signal obtained when the third optical disc is used.