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. 01, 2008
Filed:
Nov. 05, 2002
Keiji Sakai, Nara, JP;
Takahiro Miyake, Soraku-gun, JP;
Tetsuo Ueyama, Nara, JP;
Renzaburo Miki, Soraku-gun, JP;
Hiroshige Makioka, Tenri, JP;
Noboru Fujita, Kitakatsuragi-gun, JP;
Osamu Miyazaki, Soraku-gun, JP;
Keiji Sakai, Nara, JP;
Takahiro Miyake, Soraku-gun, JP;
Tetsuo Ueyama, Nara, JP;
Renzaburo Miki, Soraku-gun, JP;
Hiroshige Makioka, Tenri, JP;
Noboru Fujita, Kitakatsuragi-gun, JP;
Osamu Miyazaki, Soraku-gun, JP;
Sharp Kabushiki Kaisha, Osaka, JP;
Abstract
An object of the present invention is to attain stable tracking servo performance by suppressing an offset caused by a shift of an object lens or a tilt of a disk, despite the one-beam method which does not cause reduction in light quantity of the main beam. A diffraction grating is provided between a hologram and a light receiving section, and a diffraction efficiency of the diffraction grating is varied in a grating longitudinal direction. For example, if an incident light beam on the diffraction grating is shifted in the grating longitudinal direction, the quantity of received light in each light receiving section varies to cause offset. By performing tracking servo so as to cancel the change, it is possible to correct the offset, thereby attaining stable tracking servo performance.