OPTICAL MEASUREMENT SYSTEM OF SOUND PRESSURE WITH REFRACTED LASER-LIGHT PROPAGATED THROUGH AN ACOUSTIC FIELD

An optical measurement method using a laser beam is described for the quantitative measurement of acoustic fields. The light beam is refract ed in the acoustic field because the distribution of densities forced by sound pressure generates a refractive index gradient in the medium. The characteristics of the acoustic field can be measured using a las er beam refracted by the acoustic field. To confirm the validity of th e method, the acoustic field generated by a lead zirconate titanate (P ZT) circular-plane transducer was measured for comparison with the cha racteristics obtained from a conventional hydrophone. We also measured harmonic contents, wave distortion due to the nonlinear effect of wat er, and subharmonics of the n/2th order (n: integer) caused by cavitat ion in water.