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:
Jan. 15, 2002
Filed:
Aug. 03, 1999
Keiji Sakai, Nara, JP;
Sharp Kabushiki Kaisha, Osaka, JP;
Abstract
A light receiving element ( ) receiving return light from an optical disk has main light receiving sections ( ) and sub light receiving sections ( ). A focus error signal is found by computing (Sa+Sf )−(Sb+Se), where Sa, Sb, Se, and Sf represent output signals of the light receiving sections ( ), respectively. Each of the sub light receiving sections ( ) has a smaller area than each of the main light receiving sections ( ) has. With the foregoing arrangement, upon access to a multilaminate optical disk in which distances between recording layers are small, respective focus error signals from the recording layers do not interfere with each other, and occurrence of an offset can be suppressed even in the case where an assembly error of the optical element or the like exists.