Free-form surface reconstruction for adaptive imaging with 2D ultrasound arrays

This paper introduces the Aperture Interpolation Method (AIM) for free-form surface reconstruction using 2D ultrasound arrays. Surface reconstruction plays an essential role in adaptive imaging methods, allowing for effective operation even with imprecise or unknown system geometries. The AIM method leverages the time of flight (TOF) of echos from surface reflections to estimate the surface geometry of a component under test, without requiring a pre-existing component model. In this paper we present the theoretical basis of AIM for three acquisition modes: pulse-echo, pitch-catch, and plane wave. Experimental validation is performed using a complex-shaped aluminum test piece scanned with an 11x11, 3MHz matrix array mounted on a robotic arm. The ultrasonically reconstructed surface is compared with laser scanning data for accuracy analysis. Furthermore, the ultrasonically measured surface data is used to generate Total Focusing Method (TFM) images of the component, which are then compared against micro-CT images for validation. The experimental results validate the AIM method’s capability to accurately reconstruct surfaces, facilitating reliable imaging of the components defects, thereby demonstrating its potential applicability in industrial settings.