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:
Apr. 08, 1997
Filed:
Sep. 15, 1995
Fujitsu Limited, , JP;
Abstract
An optical information recording-and-reproducing unit includes a diffraction section provided with a reflected optical beam reflected on a storage medium. The diffraction section has at least first and second areas, and from each of the first and second areas, a +1-order diffraction light and a -1-order diffraction light are produced. The unit further includes first and second optical detection sections respectively provided with one of a pair of +1-order diffraction lights and a pair of -1-order diffraction lights produced from the first and second areas of the diffraction section. The unit still further includes a first circuit section for generating a tracking error signal based on output signals of the first and second optical detection sections. In the unit, the light provided to the first optical detection section forms a first spot in a far-field state before convergence, and the light provided to the second optical detection section forms a second spot in a far-field state after convergence.