Tomographic Schlieren imaging for measurement of beam pressure and intensity

The visualization of ultrasonic fields via acousto-optic interaction is an old technique. Shadowgraph and schlieren imaging produce data representing a line integral related to pressure and time-average intensity, respectively. These “projections” can be used in computed tomography. We have compared the reconstructed pressure distribution in a plane obtained via tomographic inversion with those obtained by mechanically scanning a 0.5 mm calibrated hydrophone through the same plane. Schlieren methods result in the reconstruction of a time average intensity approximation. Shadowgraph methods reconstruct pressure at a given point in time. The advantage of the tomographic methods is that they can be done quickly. A fully automated system could produce a three-dimensional image of an ultrasound beam in a few minutes