An Image Spectroscopy System for the Analysis and Documentation of Paintings

Infrared reflectography, one of the most powerful nondestructive techniques to investigate works of art, has been extensively used to evidence possible underdrawings or pentimenti. Spectrum analyzers equipped with fiber optic probes make it easy to extract reliable spectrum profiles both in the visible and near infrared regions, providing useful information about the composition of pigments. While the former technique gives qualitative information on a wide painting area at the same time, the latter can be extremely accurate, but its use is limited to small areas. The experimental technique proposed here aims to acquire a sequence of multispectral images, in order to get spectral information in the visible and near infrared regions (VNIR-Image Spectroscopy) about the whole painting at the same time. The multispectral image sequences thus obtained can represent an important document of the work of art to be used for monitoring its state of conservation, for comparison after restoration, and for research purposes. Several experimental problems have to be faced in order to make the system reliable and sensitive enough. An approach and possible solutions are discussed and preliminary experimental results presented.