  Interferometric imaging is a well established method to image phase objects
by mixing the image wavefront with a reference one on a CCD camera. It has also
been applied to fast transient phenomena, mostly through the analysis of single
interferograms. It is shown that for repetitive phenomena multiphase
acquisition brings significant advantages. A 1 MHz focused sound field emitted
by a hemispherical piezotransducer in water is imaged as an example.
Quantitative image analysis provides high resolution sound field profiles.
Pressure at focus determined by this method agrees with measurements from a
fiber-optic probe hydrophone. This confirms that multiphase interferometric
imaging can indeed provide quantitative measurements.
