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. 30, 1993
Filed:
Nov. 12, 1991
Ko Ishizuka, Urawa, JP;
Tetsuharu Nishimura, Kawasaki, JP;
Yoichi Kubota, Yokohama, JP;
Masaaki Tsukiji, Tokyo, JP;
Satoshi Ishii, Tokyo, JP;
Canon Kabushiki Kaisha, Tokyo, JP;
Abstract
An interferometer for measuring the displacement of a diffraction grating includes a multi-mode semiconductor laser for generating a laser beam; a device for supplying a predetermined current to the laser so that at least five vertical modes occur in an oscillation spectrum of the laser beam generated by the laser at an intensity ratio of at least 0.05; and an optical system for splitting the laser beam generated by the laser into first and second beams. The optical system also directs the first and second beams to the diffraction grating and effects interference between a first diffracted light beam generated by the diffraction of the first beam at the diffraction grating and a second diffracted light beam generated by the diffraction of the second beam at the diffraction grating to produce an interference light beam. Also provided is a photoelectric convertor for converting the interference light beam into an electrical signal.