Low frequency PVDF transducers for 3D object profiling in air

The feasibility of a 3D ultrasonic scanner in air for the profile reconstruction of a shoe tree is discussed. The severe requirements on the spatial resolution (about 100 μm) stress the ultrasound technique performance. High resolution time-of-flight measurement techniques based on phase measurement are combined with the ellipsoidal back-projection image reconstruction algorithm. A laboratory set-up is assembled to evaluate the achievement of the desired resolution by using wooden phantoms with constant cross sections characterised by sharp edges and low curvature radius. Preliminary experimental results are reported that show the system capability to reconstruct cross section profiles with rms and maximum errors equal to 0.38 mm and 1.2 mm respectively