Suppression of geometrical artifacts from acoustic lenses through low-rank approximation

Acoustic lenses have recently been used in non-destructive testing (NDT) for pipeline inspections. They decrease inspection time by increasing the spatial coverage of linear phased array ultrasonic transducers. However, the acoustic lens also introduces geometrical artifacts in the acquired signal, which worsen the flaw contrast. Usually, artifact suppression methods rely on simulations or additional inspections to generate reference signals, which are then subtracted from the signals of interest. In this work, we propose a method of reducing geometrical artifacts through a truncated Singular Value Decomposition (SVD). In a mechanical sweep, if the geometric artifacts remain constant throughout the sweep and flaws are spatially localized, the low-order SVD components represent geometric artifacts, while the higher-order components contain information about the flaws. In a circumferential sweep of a pipe with a side-drilled hole, the proposed method’s best improvement, compared to the raw signal, occurred when the flaw intensity was minimal, resulting in an approximately 3.87 dB increase in CNR. Overall, our method effectively enhances the ability to detect flaws by exploiting the spatial behavior of specific types of flaws.

Proceedings of the 14th European Conference on Non-Destructive Testing (ECNDT 2026)