Colorimetric Study on Optical Data from 3D Laser Scanner Prototype for Cultural Heritage Applications

Cultural Heritage digitalization and 3D visualization are by now key applications of technology development for several purposes in historical, artistic and cultural heritage conservation fields. One of the most challanging aspects of the work of art's digitalisation process is the colour definition and transposition. Nowadays, several systems could give an accurate colour characterisation but most of them requires reduced working distances and produces unpleasent logistic problems, such as the use of scaffolds. The RGB-ITR 3D laser scanner, entirely designed and developed at ENEA laboratories, is a system which allows remote diagnosis, collecting simultaneously five types of information per each sample point: two distances and three target reflectivity signals for each channel (red, green and blue). The combination of these informations makes the RGB-ITR a good starting point for remote colorimetry allowing diagnoses without the use of scaffolds. For both colour and structural analysis several calibration methodologies were introduced in order to observe changes-in-time of the investigated artworks. The present work shows how the laser beam incidence angle influences the collected information and introduces the correction coefficient for balancing the affected data, with the final aim to reduce the time spent for in situ calibration. The formulated procedure has been applied to the case study of the Blue Daemons Tomb in the Etruscan Tarquinia Necropoli (VT, Italy).