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:
Jun. 21, 2011
Filed:
Jun. 30, 2010
Toshiteru Nakamura, Yokohama, JP;
Shigeharu Kimura, Yokohama, JP;
Kunikazu Ohnishi, Yokosuka, JP;
Toshio Sugiyama, Yokohama, JP;
Toshiteru Nakamura, Yokohama, JP;
Shigeharu Kimura, Yokohama, JP;
Kunikazu Ohnishi, Yokosuka, JP;
Toshio Sugiyama, Yokohama, JP;
Hitachi Media Electronics Co., Ltd., Iwate, JP;
Abstract
When recording/reproducing an optical disc having a recording layer of multi-layer structure, an unwanted optical beam reflected from a recording layer other than a target layer for recording/reproduction is incident on a photodetector to cause an unwanted disturbance component to leak to a detection signal, giving rise to a degradation in the quality of a tracking control signal. In an optical pickup apparatus, for suppression of the degradation, an optical element is mounted having a diffraction area for diffracting part of the optical beam and light receiving planes for sub-optical beams are provided each of which has a light shielding zone or dead zone of a predetermined width on its central sectioning line.