The diffraction-free PVDF hydrophone: a new and versatile tool for materials characterisation

The authors have produced a large aperture broadband hydrophone which is insensitive to diffraction effects. If the hydrophone is placed at right angles to the axis of propagation the received pulse signal is identical over the whole field in a non-attenuating medium, and scaled appropriately in an attenuating medium. Variations in received pulse shape are due entirely to properties of the medium and not to diffraction effects. Thus attenuation, reflection, and velocity of ultrasound may be easily studied. A useful property of the hydrophone is that it produces a spatially invariant pulse for focussed as well as planer transducers