Phasenkontrastverfahren zur Messung von Ultraschallfeldern

In this thesis an optical imaging technique was developed for the visualization and the quantitative measurement of acoustic fields generated by ultrasonic transducers with power levels in the medical diagnostic range. The acoustically distorted light wavefront of short laser pulses synchronized to the ultrasound source is analyzed by a two lens optical system with a pixel addressable liquid crystal spatial light modulator as the filtering device in the focal plane of the first lens. Focused phase-contrast images are recorded by a CCD camera for further processing. It is shown that by applying multiple optical phase-only filtering functions the phase shift of the light wavefront caused by the acoustically induced density variations can be acquired. The measured phase shift is proportional, according to the piezo-optical effect, to the local pressure deviation projected along the line of sight.