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. 08, 1992
Filed:
May. 13, 1991
Applicant:
Inventors:
Carolyn R Mercer, Cleveland, OH (US);
Glenn Beheim, Hiram, OH (US);
Primary Examiner:
Assistant Examiner:
Int. Cl.
CPC ...
G01B / ;
U.S. Cl.
CPC ...
356356 ; 356360 ; 356376 ; 382 26 ; 364575 ;
Abstract
A projected fringe interferometer for measuring the topography of an object periodically steps the phase angle between a pair of light beams emanating from a common source. The steps are .pi./2 radians (90.degree.) apart and at each step a video image of the fringes is recorded and stored. Photodetectors measure either the phase angle .theta. of the beams or 2.theta. either of which is used to control one of the light beams so the 90.degree. .theta. is accurately maintained. A camera, a computer, a phase controller and a phase modulator established closed-loop control of .theta.. Measuring the phase map of a flat surface establishes a calibration reference.