Study on the vibrational characteristics of ultrasonic transducers using tapered piezoelectric ceramic elements

Any nonuniformity in the flatness of a crystal element used in an ultrasonic transducer may lead to significant variations in transducer response. An accurate estimation of such variations could obviously be a measure of the nonuniformity involved, whatever its extent may be. Studies are reported on the effect of nonparallelism between two major plane surfaces of the crystal element on transducer response by studying the normal displacement amplitude pattern and its distribution over one of the vibrating (plane) surfaces at resonance. Measurements are carried out in air using a phase-locked laser interferometry technique where the effect of tapering in disk thickness on the transducer performance is manifested through the variation in vibrational patterns. Results of these measurements are compared with those obtained from electrical (conductance) response to highlight the importance of the former. Other comparison measurements, such as the conventional method of determination of acoustic response and pulse waveforms of the radiated signals in water, are also reported as a function of tapering in disk thickness. A correlation is discussed between results obtained from different measurements. (C) 1997 Acoustical Society of America.