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:
Mar. 19, 1991
Filed:
May. 03, 1989
Tetsuharu Nishimura, Kawasaki, JP;
Masaaki Tsukiji, Tokyo, JP;
Satoshi Ishii, Tokyo, JP;
Koh Ishizuka, Urawa, JP;
Yoichi Kubota, Kawasaki, JP;
Canon Kabushiki Kaisha, Tokyo, JP;
Abstract
In an optical type encoder for projecting a light beam onto an optical type scale having a diffraction grating formed thereon, forming an interferenced light by the use of a diffracted light from the scale, and photoelectrically converting the interferenced light to thereby measure the displacement of the scale, first and second light beams are caused to enter substantially the same position on the scale from different first and second directions, first and second diffracted light beams emerging from the scale by the first and second light beams being diffracted by the scale are directed to the aforementioned position by a reflecting device, the diffracted light beams emerging in the first and second directions by the first and second diffracted light beams being diffracted by the scale are superposed one upon the other to thereby form an interferenced light, and light components created by the first and second light beams being regularly reflected at the aforementioned position are not included in the interferenced light.