Ultrasonic Imaging and PROFILOMETRY Using Synthetic Aperture with MHz PMUTs in Air

In this work, we demonstrate the functionality of using a single channel 15% Scandium doped Aluminum nitride (ScAlN) 3 mm × 3 mm, silicon-on-nothing (SON) piezoelectric micromachined ultrasonic transducer (PMUT) array to provide accurate profilometry and imaging via synthethic aperture (SA) in contrast to traditional delay-multiply-and-sum image reconstruction. The 16 × 15 array in parallel, with resonant frequency of 1.15 MHz, was used to send and receive pulse-echo signals to and from various jigs to reconstruct and measure the surface profiles of the 2D scans. A precision stage controller was used to move the PMUT chip in 50 µm steps in the x-y plane and a sub-resonant signal of 750kHz was transmitted. The array of signals was then digitally processed to achieve high-resolution images and profile scans with minimum lateral resolution of 0.8 mm and axial resolution of less than 0.05 mm.