Synthetic aperture focusing technique for high-resolution imaging of surface structures with high-frequency ultrasound

In this paper, an approach for the imaging of planar surface structures with high-frequency ultrasound in the 20 MHz frequency range is presented and evaluated. Planar material samples are placed in the far field of a single element transducer, and echo signals are acquired in a monostatic, side looking configuration during one or more scans along the azimuth direction. Synthetic aperture focusing is utilized for the reconstruction of B-mode images, which represent the echogenicity along the two-dimensional planar surface. The concept has been evaluated with a spherically focused transducer under the assumption of a virtual point source and under the approximation that spherical waves emanate from the transducer focus. Results from both, simulated echo data and measurement data from test objects, are presented and discussed.