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:
Jul. 15, 2014
Filed:
Apr. 13, 2012
Akihiro Kuroda, Tokyo, JP;
Akihiro Kuroda, Tokyo, JP;
DMG Mori Seike Co., Ltd, Nara, JP;
Abstract
An optical displacement measurement device in which variations in interference light by stray light are suppressed to improve interpolation accuracy and detection accuracy. The surface of diffraction gratingis coated with protective layerof thickness L and refractive index n. The protective layer has thickness L such that, with angle θ between a line normal to the protective layer and an incident light beam and an angle θ' between diffracted light generated by diffraction grating and reflected by boundary surface of protective layer to become stray light to be re-incident on diffraction grating and a line normal to diffraction grating, interference light is of an intensity of interference such that an optical path difference between stray light and light interfering with stray light represented byΔ(/cos θ′+tan θ′·sin θ)will amount to not higher than% of intensity of interference of interference light with optical path length difference Δ