Figure 5
Comparison between the optical and THz images regarding the visualization of inscriptions. (a) Photograph of the original Pb cross. (b) Final THz image of the Pb cross after post-processing. (c) Photograph of the Pb cross after chemically removal of the corrosion. Typical regions are highlighted, in which inscriptions are revealed in the THz image but are barely visible in the optical image before removing the corrosion. As can be read from the THz image (b) and confirmed after removal of corrosion (c), the inscriptions in the top right boxes are ‘tuum fiat voluntas tua’ and part of ‘quotidianum’; the ones in the bottom left boxes are a portion of ‘imittimus’ and ‘tentationem’, respectively.
