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:
Jul. 28, 2009
Filed:
Jan. 16, 2007
Applicant:
Minoru Ohyama, Kanagawa-ken, JP;
Inventor:
Minoru Ohyama, Kanagawa-ken, JP;
Assignee:
Primary Examiner:
Int. Cl.
CPC ...
G11B 7/135 (2006.01);
U.S. Cl.
CPC ...
Abstract
In a photo pickup device, a hologram elementis divided into eight areas. In operation, the hologram elements adds different lens powers to four diffraction lights forming two pairs of diffraction-light groups. In the photo pickup device, a light receiving elementis divided into four areas to receive these diffraction lights. The photo pickup device outputs signals corresponding to four quadrants A, B, C and D forming a reflection light from an optical disc, allowing a focus-error signal to be calculated in the same logic as an 'astigmatism method'.