Multispectral imaging of paintings by optical scanning

In the last few years, there has been a growing interest on multispectral imaging as non-destructive technique for painting diagnostics. Providing spectral and colorimetric characterization of the whole paint layer, such a technique is suitable to document the conservation state of an artwork. In this work we present a scanning system for multispectral imaging of paintings in the 380-800 nm spectral region, specifically developed to overcome most of the problems related to the traditional detection systems based on CCD or Vidicon camera. The device is composed of a spectrometer for contact-less single-point spectral measurements, moved by two orthogonally mounted translation stages. It scans an area of 1 m2 with 16 dots/mm2 spatial resolution and 10 nm spectral resolution. Spectral reflection factor and tristimulus value measurements were carried out on coloured ceramic tiles and the results were compared with the corresponding certified values. We also present the first application to an ancient painting.