Characterization of Ultrasonic Sources Using Schlieren and Phase-Contrast Methods

To rapidly characterize ultrasonic sources with power levels in the medical diagnostic range optical measurement techniques provide an alternative to time consuming hydrophone measurements. In this paper, the concept of schlieren photography is extended to a highly flexible solution by using a spatial light modulator as a replacement for the schlieren stop. By using short laser pulses as the light source, synchronized to the ultrasonic source, high quality images of the actual acoustic waves are acquired. The optical system is modeled by means of Fourier optics, a demonstrator setup and measurement results are presented.