The system consists of an ImSpector N25E imaging spectrograph (Specimcorp, Finland) and a cooled, temperature stabilized MCT detector (9.6 mm detector having 320 (spatial) x 256 (spectral) pixels). The camera operates from 970 to 2500 nm with a spectral resolution of 10 nm. It works as a line scan camera providing full, contiguous spectral data for each pixel. The cooling system (dual Peltier solution, forced convection coolers) is designed to minimize dark current and ensure high stability in the detector operations in a wide ambient temperature range. Two objective lenses are available: A telecentric lens with a focal length of 15 mm (corresponding to a minimal field of view of 20 cm and a maximal resolution of 600 µm) A macroscopic lens with a 1:1 magnification (corresponding to a field of view of 9.6 mm and a spatial resolution of 30 µm) The camera is moving along a motorized bar of around 1.6 m, resting on a portal frame structure. The height of the structure is around 2 m. The artwork is illuminated with 6 halogen lamps (three on each side) placed at 45 degrees from the vertical. The current structure is designed to scan artefact laid flat on a tablebut the configuration can possibly be changed to scan artefact in a vertical position.
Potential Results
This technique is well adapted to characterize organic compounds (binding media, plastic materials…) and some minerals. Hyperspectral Imaging provides spatially resolved information on the nature of chemical species that can be interesting to locate damages (moisture, chemical transformations…), restorations, pentimenti or underdrawings on/in an artwork. Hyperspectral imaging is well adapted for flat or slightly embossed artworks (manuscript, drawing, paintings,…).