Accession Number : ADA115930

Title :   Interferometric Detection of Ultrasound.

Descriptive Note : Final rept. 1 Sep 80-1 Jul 81,

Corporate Author : BOLT BERANEK AND NEWMAN INC CAMBRIDGE MA

Personal Author(s) : Rudd,Michael J

PDF Url : ADA115930

Report Date : 01 Jul 1981

Pagination or Media Count : 39

Abstract : This report describes the development of an interferometer to measure ultrasonic surface vibrations. The output from a low power helium-neon laser was focused onto the surface to be measured, and the phase of the reflected light was measured. The type of interferometer used was an Optical Heterodyne Interferometer, in which the frequency of the reference beam was shifted by 40 MHz and a phased-locked loop was built to track the 40-MHz signal. The sensitivity, frequency response, and pulse response were measured and compared with those from a PZT transducer. The effects of different surface finishes were also studied, and the sensitivity was compared with theoretical values. The actual sensitivity was 15A on a 10-MHz bandwidth, and 0.02A on a 1-Hz bandwidth. Finally, suggestions are made to improve the sensitivity still further.

Descriptors :   *Ultrasonics, *Detection, *Interferometers, Helium Neon lasers, Optical interferometers, Reflection, Frequency response, Pulses, Surface finishing, Bandwidth, Low power, Loops, Phase locked systems, Heterodyning, Light sources, Transducers

Subject Categories : Acoustic Detection and Detectors
      Acoustics

Distribution Statement : APPROVED FOR PUBLIC RELEASE