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:
Apr. 15, 1997
Filed:
Sep. 26, 1994
Yasushi Kaneda, Tokyo, JP;
Koh Ishizuka, Ohmiya, JP;
Canon Kabushiki Kaisha, Tokyo, JP;
Abstract
An apparatus for measuring the relative displacement information between it and a scale on which a diffraction grating is formed has a light source, a separating device for separating a light beam from the light source into a plurality of light beams, a wave combining device for wave-combining the diffracted lights of the plurality of light beams separated by the separating device which are diffracted by the diffraction grating, a light receiver for receiving the interfering lights by the plurality of light beams wave-combined by the wave combining device, the relative displacement information between the apparatus and the scale being measured by the light reception of the light receiver, and an optical device adapted to collimate the plurality of light beams or to form a spherical wave having so large a radius of curvature that it can be regarded as a plane wave of the plurality of light beams in the direction of light beam separation of the separating device and to condense the plurality of light beams in the optical path from the separating device to the wave combining device in a direction perpendicular to the direction of light beam separation.