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:
Sep. 01, 1998
Filed:
Mar. 17, 1997
Okuma Corporation, Nagoya, JP;
Abstract
The amount of the light beam passing through two diffraction gratings is output as an electrical signal by a photo detector. The amount of relative displacement of the diffraction gratings is detected according to the electric signal (output signal) that changes in proportion to the relative displacement. Groove portions and ridge portions are alternately arranged on the first diffraction grating, through which the light beam passes and undergoes wavefront modulation by mutual interference of the zeroth-order diffracted light. This eliminates interference of the zeroth-order diffracted light with a diffracted light of another order, and eliminates changes in the fundamental wave component of the output signal caused by changes in the gap between the two diffraction gratings. The output signal can be made not to include a high-order component by a predetermined modification to at least one of either the array pitch or width of a transparent portion in the second diffraction grating.