Improvement of ENEA laser-induced fluorescence prototypes: An intercalibration between a hyperspectral and a multispectral scanning system

Laser-induced fluorescence (LIF) is a well-recognised spectroscopic technique used in cultural heritage for non-destructive surface chemical analysis. It is particularly suitable for in situ analysis of delicate items such as artworks because it does not require any sample preparation or contact and can be used at a distance in situations where only optical access is available. Recently, ENEA has developed two LIF prototypes with multispectral (Forlab) and hyperspectral (Lifart) scanning systems that each return different types of results, making them necessary for and dependent on each other. Forlab's motorised optics enable the rapid acquisition of fluorescence maps and images of large surfaces in specific spectral wavelengths, while Lifart returns complete fluorescence spectra, providing the complete spectral information of an object. In this paper, the intercalibration of the two systems is reported together with a data analysis of the calibration samples and a software that automatically corrects imaging data, taking Forlab's filter passband and optical efficiencies into account in order to make these two configurations as easy to compare as possible. The new correcting algorithm is also tested on LIF measurements carried out on an Egyptian casket and sarcophagus, obtaining higher quality fluorescence images.