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:
Aug. 23, 2005
Filed:
Apr. 20, 2004
Takeshi Shimano, Tokorozawa, JP;
Shigeru Nakamura, Tachikawa, JP;
Kunikazu Ohnishi, Yokosuka, JP;
Masayuki Inoue, Yokohama, JP;
Yukio Fukui, Machida, JP;
Takeshi Shimano, Tokorozawa, JP;
Shigeru Nakamura, Tachikawa, JP;
Kunikazu Ohnishi, Yokosuka, JP;
Masayuki Inoue, Yokohama, JP;
Yukio Fukui, Machida, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
An optical head having a semiconductor laser and a generation of a plurality of reflected light beams from an optical disk which have polarities of intensity distribution variations which are substantially inverted to each other when a periodic structure of the optical disk crosses at least one focused spot on the disk. An optical detection system splits the plurality of reflected light beams and detects the split reflected light beams. An electrical circuit provides a focus error signal of the at least one focused spot and a tracking error signal from the plurality of reflected light beams. The electrical circuit adds focus error signals provides a difference signal between the focus error signals, amplifies tracking error signals with a gain, and obtains a difference between amplified tracking error.