Ultrasound field characterisation in air using light diffraction tomography

In English The aim of this work was to show the applicability of light diffraction tomography on airborne ultrasound. Different air-coupled transducers in the frequency range 40 kHz - 2 MHz were measured to show the method's performance. A calibrated microphone and the pulse-echo method were used to evaluate the results. The absolute measurements agreed within the calibrated microphone's uncertainty range. Pulse waveforms and corresponding FFT-diagrams show the method's higher bandwidth compared to the microphone. Further, the method offers non-perturbing measurements with high spatial resolution, which was especially advantageous for measurements close to the transducer surfaces. The S/N-ratio was larger than or in the same range as that of the two comparing methods.