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. 27, 2012
Filed:
May. 13, 2009
Applicant:
Akio Fukushima, Yokohama, JP;
Inventor:
Akio Fukushima, Yokohama, JP;
Assignee:
Hitachi, Ltd., Tokyo, JP;
Attorney:
Primary Examiner:
Assistant Examiner:
Int. Cl.
CPC ...
G11B 7/24 (2006.01);
U.S. Cl.
CPC ...
Abstract
A multilayer optical disc has dimples and/or bumps on a surface of at least one of the layers. Dimensions of the dimples and/or bumps, such as size, frequency and pitch, are selected to generate frequency components in light reflected from the surface that are different from frequency of servo and/or information signals. A disc drive can then use an appropriate filter to remove signals produced by light reflections of an unintended layer.