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:
Jun. 21, 1983
Filed:
Jul. 01, 1981
Walter Kaule, Cologne, DE;
Krautkramer-Branson, Inc., Stratford, CT (US);
Abstract
In an apparatus for receiving ultrasonic waves by optical means a laser beam illuminates a workpiece surface at which ultrasonic waves are manifest in the form of cyclically occurring surface deformations. The reflected light is transmitted to an optical interferometer as a measuring light beam and the beam exiting from the interferometer is converted to an electrical signal and amplified to provide a measuring beam responsive electrical signal. A portion of the laser beam immediately before being incident on the workpiece surface is also passed through the interferometer as a comparison beam. The exiting comparison beam light is converted to an electrical signal, amplified and time delayed to provide a comparison beam responsive electrical signal. By means of a subtracting circuit the comparison beam responsive electrical signal is subtracted from the measuring beam responsive electrical signal to provide a difference signal which is evaluated. The time delay is adjusted to cause the difference signal to be free of the frequency and amplitude responsive variations of the laser beam. In a Michelson type interferometer both light beams traverse the same paths in the same direction, but spatially separated. In a Mach-Zehnder interferometer both light beams traverse the same paths in respective opposite directions.