VELOCITY AND ATTENUATION COEFFICIENT MEASUREMENT TECHNIQUES USING THE INTERFEROMETRIC MODE OF A 100 MHz SCANNING LASER ACOUSTIC MICROSCOPE.

K. Tervola, D. Steiger, W. D. O'Brien

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

An interferogram is produced when the Scanning Laser Acoustic Microscope is operating in its interferometric mode. The interferogram contains the phase and amplitude information of the wavefield, which has penetrated through the specimen of known thickness. The interferogram is visualized on a monitor as equal phase wavefronts and digitized with an A/D converter. The individual raster lines of the interferogram appear as sinusoids. If there has been a localized change in the specimen velocity the phase of the adjacent lines would have been shifted relative to each other in that area. The amplitude of the sinusoids along the specimen is an indication of the acoustic pressure from which the relative changes can be evaluated for the localized attenuation coefficient. The bending of the equal phase wavefronts carries the information of the relative ultrasonic velocity variations along the specimen. When the specimen is immersed into saline, in which the ultrasonic velocity is known, these relative values can be transformed into absolute ones based on Snell's Law. The attenuation coefficient can also be determined from the same interferogram data.

Original languageEnglish (US)
Title of host publicationActa Polytechnica Scandinavica, Applied Physics Series
PublisherFinnish Acad of Technical Sciences
Pages223-227
Number of pages5
Edition150
ISBN (Print)951666203X
StatePublished - Jan 1 1985

Publication series

NameActa Polytechnica Scandinavica, Applied Physics Series
Number150
ISSN (Print)0355-2721

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)

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