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. 24, 1996
Filed:
Feb. 01, 1995
Donald K Mitchell, Marblehead, MA (US);
MicroE, Inc., Needham, MA (US);
Abstract
The apparatus disclosed herein employs a grating or scale which concentrates light at a preselected wavelength into the positive and negative first orders while minimizing the zeroth order. The scale is illuminated with monochromatic light of the selected wavelength and a poly-phase periodic detector has its sensing plane spaced from the scale a distance less than ##EQU1## where W is the width of the illuminated region of the scale. The period of the poly-phase detector is equal to P/2 so that each detector element or phase responds principally to interference between the positive and negative first orders without requiring magnification or redirection of the diffracted light. Preferably, the distance of the sensing plane from the scale is greater than ##EQU2## so that the detector response does not include substantial components from diffraction orders higher than the first.