Infrared, Terahertz and Air-Coupled Ultrasonic Non-invasive Inspection for Artworks: A Comparative Study on an Old Hand-Bound Book of the XIXth Century

This work presents a comparative study for the inspection of an old book, which was bound in the XIXth century. Infrared thermography (IRT), terahertz time-domain spectroscopy (THz-TDS) and air-coupled ultrasonic C-scan (ACU) were used to retrieve the damages and defects in the book cover. Image processing techniques including Fast Fourier Transform (FFT), peak-to-peak and time-delay analysis in time domain were applied in order to highlight the shapes of subsurface features. X-ray radiography was used to anticipate the inspection results. Overall, this work appears useful to investigate the feasibility of different non-invasive inspection (NII) techniques applied to ancient books.