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. 27, 2009
Filed:
Sep. 29, 2004
Katsushige Masui, Nara, JP;
Kazuhiro Tsuchida, Kashihara, JP;
Kazunori Matsubara, Nara, JP;
Masahiro Ikehara, Nara, JP;
Keiji Sakai, Nara, JP;
Tetsuo Ueyama, Nara, JP;
Toshiya Nagahama, Kashiba, JP;
Katsushige Masui, Nara, JP;
Kazuhiro Tsuchida, Kashihara, JP;
Kazunori Matsubara, Nara, JP;
Masahiro Ikehara, Nara, JP;
Keiji Sakai, Nara, JP;
Tetsuo Ueyama, Nara, JP;
Toshiya Nagahama, Kashiba, JP;
Sharp Kabushiki Kaisha, Osaka, JP;
Abstract
To read information from a target information recording surface reliably by canceling DC offsets in tracking-signal detection signals is provided. In effecting tracking servo by 3-beam method, auxiliary light receiving domains D, D, D, Dare provided. The auxiliary light receiving domain receives images formed by the light returned from a different information recording surface from the one targeted for reading. Sub beams of ± first-order diffracted light enter the light receiving domains D, D, D, D. With respect to the diffraction direction of the hologram, the auxiliary light receiving domains D, D(D, D) are provided on both sides of the light receiving domain D(D). Since signals are computed as: D−(D+D); and D−(D+D) with the internal connection, DC offsets can be canceled in RES signals (D+D, D+D) used in the DPP method.