Enhanced terahertz nondestructive evaluation and stratigraphic reconstruction with filtered deconvolution

Terahertz pulsed imaging (TPI) is a valuable tool for nondestructive evaluation (NDE), enabling high-resolution stratigraphic characterization and structural inspection of various materials. However, its accuracy — defined by both the precise localization of peaks and the reduction of spurious peaks — can be limited by challenges such as low signal-to-noise ratio (SNR) and temporally overlapping echoes when layers are thin. While advanced signal-processing methods such as sparse deconvolution (SD) and orthogonal matching pursuit (OMP) have shown promise in addressing these issues, their effectiveness often hinges on careful parameter selection, which typically requires significant expertise. This paper presents a novel approach that enhances the accuracy and simplifies parameter determination in THz TPI by applying SD to a filtered impulse response function in the time domain. This method also aids in OMP parameter determination, further advancing the precision and usability of THz TPI for NDE applications. We demonstrate the effectiveness of the proposed approach by applying it to experimental data obtained from Willow glass on silicon and mill scale on hot-rolled steel strip, showcasing its versatility across different material systems.