Fig. 4.

(a) Recorded A-scans after spatial filtering (Eq. (2)), then processed and filtered in the frequency domain using Eq. (3) (as described in [48], [49] in detail), and finally TGC-corrected using Eq. (4) to form TGC-corrected full-bandwidth LU B-scans. (b) Recorded A-scans processed as in (a) but with LPF added using a cutoff frequency f₁ = 5 MHz. (c) X-ray micro-CT B-scan for the same sample cross-section.

A complete set of all LU B-scan frames for sample A₁ is shown in Movie 1.