Range sensors on marble surfaces: quantitative evaluation of artifacts

While 3D imaging systems are widely available and used, clear statements about the possible influence of material properties over the acquired geometrical data are still rather few. In particular a material very often used in Cultural Heritage is marble, known to give geometrical errors with range sensor technologies and whose entity reported in the literature seems to vary considerably in the different works. In this article a deep investigation with different types of active range sensors used on four types of marble surfaces, has been performed. Two triangulation-based active sensors employing laser stripe and white light pattern projection respectively, and one PW-TOF laser scanner have been used in the experimentation. The analysis gave rather different results for the two categories of instruments. A negligible light penetration came out from the triangulation-based equipment (below 50 microns with the laser stripe and even less with the pattern projection device), while with the TOF system this came out to be two orders of magnitude larger,quantitatively evidencing a source of systematic errors that any surveyor engaged in 3D scanning of Cultural Heritage sites and objects should take into account and correct.