Phase changes of ultrasonic surface and bulk waves through focusing measured using non-contact ultrasonic methods

Focusing an ultrasonic surface or bulk wave to a point can maximise the amount of ultrasonic energy at a point and increase the sensitivity of a measurement. Using noncontact ultrasonic methods we focus an ultrasonic wave pulse on or in a sample. Focusing can be achieved by using a shaped source or by the surface profile of the sample itself. Experiments and modelling confirm the known result that once the wave pulse passes through the focal point, it will undergo a phase shift. Using non-contact ultrasonic methods on a sample with spherical or cylindrical geometry, one can exploit the surface profile of the sample to focus an ultrasonic wave, as there is no refraction to consider at the sample surface under the transducer.