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:
Dec. 15, 1992
Filed:
Sep. 19, 1991
Koichiro Komatsu, Tokyo, JP;
Hideo Mizutani, Yokohama, JP;
Nobutaka Magome, Kawasaki, JP;
Kazuya Ota, Tokyo, JP;
Nikon Corporation, Tokyo, JP;
Abstract
A position detection apparatus has a substrate on which a diffraction grating is formed and an alignment optical system for illuminating the diffraction grating with a pair of coherent light beams having different frequencies from each other from different directions. The intensity of interference fringes formed due to the interference of diffracted beams generated in the diffraction grating is detected photo-electrically. The alignment optical system forms the pair of coherent light by using an optical modulator, and two luminous fluxes from the optical modulator pass through independent optical paths positioned symmetrically with the optical axis of the alignment optical system therebetween and reach the diffraction grating from different directions. The alignment optical system has a stop having an opening having an inclined edge with respect to the direction of the grating components of the diffraction grating, the opening being in conjugation with the substrate.