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. 15, 2012
Filed:
May. 17, 2007
Masashi Kubota, Minato-ku, JP;
Hisaya Niizawa, Minato-ku, JP;
Masashi Kubota, Minato-ku, JP;
Hisaya Niizawa, Minato-ku, JP;
NEC Corporation, Tokyo, JP;
Abstract
A position-error-signal calculation circuit () calculates a relative position error between a laser-focused-beam spot () and an information recording layer (), and generates a focus error signal (). A filter () amplifies and passes therethrough a signal component in the vicinity of the natural resonance frequency of at least one mode among the natural vibration modes of the optical disc medium (). A drive amplifier receives through a stabilizing compensator () and a D/A converter () the focus error signal () passed by the filter (), to drive an objective lens (), thereby allowing the laser-focused-beam spot () to track the information recording layer ().