Indirect Measurement of Vibrating Surface of Ultrasonic Transducer Using Optical Computerized Tomography and Acoustical Holography

Abstract

We propose a method for the indirect measurement of the vibrating surface of an ultrasonic transducer using a combination of the Michelson interference method, optical computerized tomography (O-CT), and acoustical holography (AH). Ultrasonic fields affect the phase of a light passing through the fields. The phase change, including information on the sound pressure, is acquired using a Michelson interferometer. Projection data along the optical axis is obtained by one-way linear scanning, and complex sound fields are reconstructed in a region of 64×64 mm2 by CT using 36 projections. Then using AH, the complex sound pressure in the vibrating surface of the transducer is reconstructed in a region of 24×24 mm2, which is 10.0 mm distant from the transducer, using the acquired sound fields. The method does not require that the light irradiates the vibrating surface of the transducer. The experimental results are in agreement with the numerical results.