Sparse Array Synthetic Aperture Focusing With pth Coherence Factor Weighted Delay and Sum Beamforming for Nondestructive Testing

Abstract

Nondestructive testing (NDT) with ultrasonic imaging is pervasive in industry. Synthetic Aperture Focusing Technique (SAFT) can significantly improve spatial resolution and imaging contrast, but requires intensive computational resources and storage. Additionally, SAFT is typically implemented with delay-and-sum (DAS) beamforming, which suffers from limited resolution and inadequate interference rejection. This article reports $p$ th coherence factor weighted delay and sum beamforming (pCFwDAS), a nonlinear approach that integrates $p$ th root algebra with coherence factor weighting. Data was collected with an aluminum test block and a Verasonics Vantage 128 system equipped with a 32-element linear array transducer (5 MHz frequency) to evaluate imaging performance. A sparse implementation of pCFwDAS was performed with 16 and 8 elements to reduce computational overhead along with graphics processing unit (GPU) implementation. The pCFwDAS approach was compared to $p$ th root DAS and standard DAS approaches. The results shown enhanced contrast-to-noise ratio (CNR) and reduced sidelobe artifacts with pCFwDAS for both the full array and sparse array configurations. With the fully populated array, CNR enhancements of up to $14.7~\pm ~1.3$ dB were observed, and the side lobes were suppressed by up to $33.3~\pm ~5.7$ dB. For sparse array imaging, the CNR was enhanced up to $13.9~\pm ~3.1$ dB, and side lobes were reduced by up to $18.3~\pm ~3.1$ dB. These findings demonstrate the potential of pCFwDAS beamforming to enhance SAFT and enable its implementation with limited computational resources.