Measurement of the particle displacement in pulsed acoustic waves using optical heterodyne technique

Abstract

An optical heterodyne method is described for studying the particle displacement of the pulsed acoustic wave in the megahertz frequency range. The acoustic wave falls on a thin plastic film and its motion is measured with the optical heterodyne technique, which allows to resolve local acoustic beam profiles and provides a means to measure the absolute displacement. The acoustic fields from a 2.25MHz flat transducer and a 5MHz focused one are investigated quantitatively. The measured beam patterns agree well with the theoretical ones. The absolute value of the displacement is also discussed. This method is proposed as a calibration procedure for the parameters related to the acoustic fields.