Improvement of ENEA Laser Induced Fluorescence prototypes: an intercalibration between an hyperspectral and a multispectral scanning system

Abstract

Laser Induced Fluorescence (LIF) is a well-recognized spectroscopic technique in cultural heritage for non-destructive surface chemical
analysis. It is particularly suitable for in situ analysis on delicate targets as artworks, because it does not need any sample preparation
nor contact, working remotely also where only optical access is available. Recently ENEA has developed two LIF prototypes with
multispectral (Forlab) and hyperspectral (Lifart) scanning systems, that return different typologies of results, making them necessary
and dependent each other. In fact, Forlab permits by its motorized optics the rapid acquisition of fluorescence maps and images of large
surfaces in specific spectral wavelengths, while Lifart returns complete fluorescence spectra, giving a complete spectral information of
an object. In this paper the intercalibration of two systems is reported, with the data analysis of calibration samples and a software to
automatically correct imaging data, that take into account Forlab filters bandpasses and optical efficiencies, in order to make these two
configurations as much as possible comparable. The new correcting algorithm was also tested on LIF measurements carried out on an
Egyptian casket and sarcophagus, obtaining higher quality fluorescence images.