Optical measurement of wideband ultrasound fields via Gabor holography

In this experiment a wide band ultrasound pulse (center frequency 2.25 MHz) is stroboscopically illuminated with a collimated diode laser (wavelength 810 nm). Light passing through the imaging volume scatters off the ultrasonically induced spatially varying refractive index. On exit from the sound field the accumulated optical phase delay constitutes one line of the Radon transform of the instantaneous pressure. Optical phase is retrieved digitally from the measured intensity images in planes immediately following and 8.5 cm subsequent to the scattering event via iterated projection onto constrained sets. Fourier slice reconstruction is then used to reconstruct the instantaneous three-dimensional pressure distribution.