Multispectral scanner

The multispectral scanner developed at CNR-INO is characterized by 32 spectral channels, 16 in the visible (395 – 765 nm) and 16 in the near-infrared range (750 – 2500 nm). The system is designed to guarantee safe measurement conditions, avoiding any damage to the analysed object. The XY scanning stages moves jointly the lighting and the collecting systems, thus preventing the painting from extended light exposure. Furthermore, no contact between the optical head and the object’s surface is ensured by the laser-based autofocus system (mounted on the Z axis), which keeps the working distance at approximately 12 cm during the whole scanning. The boustrophedon movement of the scanning unit allows surveying areas up to 1 m2 in about 3 hours, with a spatial sampling of 250 μm (4 points/mm) and unitary magnification factor. The acquisition is regularly adjusted with certified standard references. The resulting image-cube is completely free of chromatic and optical aberrations, thanks to a catoptric system, which focuses the backscattered radiation on a bundle of 36 optical fibres. For each vertical scanning line, the distance-meter output is acquired and processed to generate real-time motion profiles, providing morphological information on the scanned surface, which can be displayed either as 3D map or raking light image. The system is computer driven by a custom-made software, which controls simultaneously the axes movement, the autofocus data processing and the images acquisition. The instrument can be disassembled to be transferred and, once set up, covers a volume of 1.5 m3.