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. 04, 2010
Filed:
Dec. 20, 2006
Yoshinori Ishikawa, Yokohama, JP;
Yoshinori Ishikawa, Yokohama, JP;
Hitachi, Ltd., Tokyo, JP;
Hitachi-LG Data Storage, Inc., Tokyo, JP;
Abstract
An object of the present invention is to provide a focus out detecting apparatus which detects focus out with accuracy during reproducing or recording of data from/on an optical disc having a plurality of recording layers. Further, another object of the present invention is to provide an optical disc apparatus in which a recording or reproducing performance of data is improved by use of the focus out detecting apparatus. A focus out detection signal is output when a level of a focus error signal exceeds a first predetermined level, then reflected light quantity from the optical disc becomes lower than a third predetermined level in a predetermined period, and then the level of the focus error signal exceeds a second predetermined level of an opposite polarity to the first predetermined level.