Novel hydrophone for two dimensional imaging of wideband acoustic pulses

The use of very wideband ultrasonic imaging systems for clinical medicine and industrial NDE (nondestructive evaluation) applications has stimulated a requirement for hydrophones capable of evaluating very-high-performance transducer arrays. It is demonstrated that two-dimensional scans of submicrosecond pulsed acoustic fields with carrier frequencies around 5 MHz can be achieved using an optically scanned hydrophone. Real-time imaging of pulsed acoustic fields in water, including the capability of displaying acoustic waveforms at any point in the plane, is shown to be achieved with signal-to-noise ratio in excess of 50 dB. These hydrophones must be able to respond at frequencies well above 20 MHz because of the nonlinear behaviour of aqueous media. The ultimate limitations of both the hydrophone package and the differential time domain sampling signal-processing scheme used are discussed with this requirement in mind