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:
Aug. 06, 1991
Filed:
Feb. 26, 1990
Tetsuharu Nishimura, Kawasaki, JP;
Yoichi Kubota, Kawasaki, JP;
Satoshi Ishii, Tokyo, JP;
Koh Ishizuka, Urawa, JP;
Masaaki Tsukiji, Tokyo, JP;
Canon Kabushiki Kaisha, Tokyo, JP;
Abstract
An encoder in which a light beam emitted from a semiconductor laser or the like is applied to a diffraction grating from a predetermined direction which is not contained in a reference plane defined by direction of relative movement of the diffraction grating and a direction normal to the diffraction grating. A diffracted light created from the diffraction grating by the application of the light beam by the light applying means is reflected by re-entering means and the reflected light is caused to re-enter the diffraction grating at substantially the same position as the position at which the diffracted light is created. At this time, an interference light formed by the other re-diffracted lights than O-order light created from the diffraction grating substantially in the same direction as the predetermined direction by the re-entrance of the diffracted light by the re-entering means is detected, and the information of the relative displacement of the light beam and the diffraction grating is obtained from a variation in the intensity of the interference light.