Active infrared thermography for the analysis of ancient books

Active infrared thermography has revealed to be an effective technique for non destructive analysis of ancient books. The working principle relies on heating the sample through the absorption of visible light and on subsequent detection of the infrared emission by means of a infrared camera. The technique allows one to investigate features buried into the artworks interior, affecting the heat diffusion inside the sample and inducing a variation in the infrared emission. In particular, it is possible to read written scraps used for the end leafs of old books and located between the end papers and the covers, which is of significant importance for scholars studying the manuscripts. This possibility is discussed in the present paper. A mathematical model for computing the signal contrast and the blurring of the thermographic image of a ink layer buried inside a paper sheet is recalled. Some numerical simulations are presented to asses the effectiveness of the model. Finally, some experimental results are also presented, in qualitative agreement with the theoretical predictions.