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. 02, 1996
Filed:
Feb. 22, 1995
Koh Ishizuka, Urawa, JP;
Tetsuharu Nishimura, Kawasaki, JP;
Canon Kabushiki Kaisha, Tokyo, JP;
Abstract
A rotary detector has a diffraction grating arranged circumferentially and a center at substantially the center of rotation. The rotary detector measures rotational information of a rotating object. The rotary detector is provided with a light source, an irradiating optical system for irradiating luminous flux from the light source to a first point on the diffraction grating, and an optical system for guiding two diffracted luminous fluxes emerging from the first point at an emerging angle and diffracted to have a same order but different signs to be incident at a second point on the diffraction grating at an incident angle relative to a rotational direction of the grating, with the second point positioned substantially opposite to the first point on the diffraction grating with respect to the center of the rotation, and the incident angle is the same angle as the emerging angle. A wave superposing optical system superposes two rediffracted lights diffracted at the second point with the order of the same signs at the first point, respectively, and a detector detects the superposed rediffracted lights. The rotational information of the rotating object is thus measured by the detector.