Optical diffraction tomography of ultrasonic fields with algebraic reconstruction techniques

The authors describe a light diffraction technique, optical diffraction tomography (ODT), which allows a measurement of ultrasonic pressure and phase in the cross-section of an ultrasonic beam. ODT measurements are based on the Raman-Nath equations describing the interaction between ultrasonic fields and light. The reconstruction of the measurement plane is done with algebraic reconstruction techniques (ARTs) combined with nearest-neighbor averaging. A limiting factor on reconstruction accuracy in tomography is the number of projections. With ART satisfactory results are obtained with 10 projections for both near- and far-field measurements. Measurements with different transducers at 2 and 3.5 MHz are presented. The measurements present pressure and phase-angle mappings. A comparison with hydrophone measurements is included