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:
Nov. 11, 1997
Filed:
Oct. 25, 1995
Tadashi Takeda, Nagano, JP;
Yoshio Hayashi, Nagano, JP;
Kabushiki Kaisha Sankyo Seiki Seisakusho, Nagano, JP;
Abstract
A tracking error signal and a focus error signal can be obtained with those components of the light (plus and minus first-order light) which have been diffracted by a hologram device whereas the undiffracted zero-order light component is for the sole purpose of producing RF signals. As a result, RF signals can be detected without using a segmented photodetector while insuring that output signals of a constant intensity are produced even if there are changes in the spot diameter and position. In addition, any aberrations that are caused by an half-mirror are corrected by optics that is provided in the optical path connecting the half-mirror and the light-receiving elements of a photodetector and this insures that even if an objective lens moves, detection spots on the individual light-receiving elements will move on the latter without causing any offset errors.