Digital tools as 3D (three-dimensional) modelling and imaging techniques are having an increasing role in many applicative fields, thanks to some significative features, such as their powerful communicative capacity, versatility of the results and non-invasiveness. These properties are very important in cultural heritage, and modern methodologies provide an efficient means for analyzing deeply and virtually rendering artworks without contact or damage. In this paper, we present two laser scanner prototypes based on the Imaging Topological Radar (ITR) technology developed at the ENEA Research Center of Frascati (RM, Italy) to obtain 3D models and IR images of medium/large targets with the use of laser sources without the need for scaffolding and independently from illumination conditions. The RGB-ITR (Red Green Blue-ITR) scanner employs three wavelengths in the visible range for three-dimensional color digitalization up to 30 m, while the IR-ITR (Infrared-ITR) system allows for layering inspection using one IR source for analyses. The functionalities and operability of the two systems are presented by showing the results of several case studies and laboratory tests.

The modern 3D digitalization techniques open new scenarios on how to transmit to the next generations the state of health of Cultural Heritage (CH) buildings, paintings, frescos or statues. The final goal of the 3D digitalization is an exact replica of the acquired target, but a standard and unique technique able to digitalize artworks of different size and in different ambient light conditions is still far from being successfully ready for the CH field. Even if both laser scanning and photogrammetry can be considered mature techniques, applied with success in most of the Cultural Heritage study cases, they are limited in terms of colour digitalization and image quality in all the cases where ambient light and big sensor-target distances are crucial factors: differently to standard laser scanners, which collect colour information by the use of a coaxial camera and the distance by an IR laser source, the RGB-ITR (Red, Green and Blue Imaging Topological Radar) scanner, developed in ENEA, is equipped with three different laser sources for the simultaneous colour and distance estimation. The present work shows the results obtained applying the above-mentioned multi-wavelengths laser scanner for collecting a complete high-quality 3D colour model of “The Triumph of Divine Providence” vault, painted by Pietro da Cortona on the ceiling of the noble hall inside Palazzo Barberini in Rome.