30 May 2001 Measurement of transducer directivity function
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A method for measuring the directivity function of transient fields with a new type of hydrophone that can be located at any convenient distance from the transducer is presented. Fields from planar and focused transducers, for both continuous wave and pulsed excitation, are measured via the new method, and the results compared against conventional measurements as well as against theoretical predictions. The directivity function for pulsed fields is best expressed as a complex directivity spectrum, and images of this fundamental transducer field characteristic are shown to encode a number of unexpected features. The definition and measurement of the directivity function, is not dependent on continuous wave or far-field conditions, and laboratory implementation of the theory is via a new type of hydrophone, with some unusual properties. It is concluded that precise and unambiguous measurement of transducer directivity patterns are straight forward to perform provided a relatively simple, but novel, technique is used. Images of the informative directivity spectrum may be obtained with ease.
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Sidney Leeman, Andrew J. Healey, Eduardo Tavares Costa, Hayram Nicacio, Ricardo G. Dantas, Joaquim Miguel Maia, "Measurement of transducer directivity function", Proc. SPIE 4325, Medical Imaging 2001: Ultrasonic Imaging and Signal Processing, (30 May 2001); doi: 10.1117/12.428234; https://doi.org/10.1117/12.428234

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