A calibration methodology of ultrasonic transducers: Evaluation of spatial propagation characteristics of pulse-echo

Abstract

This study aims to develop a novel methodology, a combined system of optical and ultrasonic measurements, for evaluating spatial propagation characteristics of ultrasonic pulse-echo. The system can record pulse-echo profiles except in the near field where the ultrasound is not well-focused. An in-house-developed stereo-vision system is utilized as a reference to measure the three-dimensional coordinates in spherical particle dispersion in water. Ultrasonic pulse-echo from the particles is identified to the three-dimensional coordinates obtained by the stereo-vision system. Acquiring numerous data of randomly-dispersed particles in water gives higher data density in three-dimensional space than the conventional method using a hydrophone sensor. The method realizes a highly-accurate evaluation of the tilt angle of the pulse emission against the transducer casing axis within O(0.01∘). The fact that the pulse-echo waveform in the three-dimensional space, rather than the radiation sound pressure field of the conventional method, can be converted into a database is crucial.