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:
Mar. 20, 2007
Filed:
Oct. 17, 2002
Toshikazu Kobayashi, Tokyo, JP;
Toshikazu Kobayashi, Tokyo, JP;
Sony Computer Entertainment Inc., Tokyo, JP;
Abstract
An objective lens of an optical pick-up is ascended from the disc Far position towards the disc Near position at a constant velocity, and a peak bottom detector detects levels between the peak to the bottom (peak-to-bottom levels) of focus error signals obtained during the focus movement. A servo processing microcomputer counts the number of focus error signals having a peak-to-bottom level not smaller than the predetermined minimum level, out of all peak-to-bottom levels obtained during the focus movement across the recording layer of a disc, and defines the count value as the number of the recording layers of the disc. This allows correct determination of the number of recording layers of recording medium while not being affected by variation in property of the instruments, variation in reflectivity of recording medium, variation in the ambient temperature and fake pulse corresponded to waviness in focus error signal.