Hyperspectral image spectroscopy: a 2D approach to the investigation of polychrome surfaces

A hyperspectral scanner operating in the visible (VIS) to near infrared (NIR) range (400-1000 nm) and based on a prism-grating-prism line-spectrograph connected to a silicon CCD camera is presented. The characteristics of this scanner are 0.1 mm spatial sampling over a 1 × 1 m2 surface and approximately 1 nm spectral sampling in the wavelength range 400-900 nm. The results provide useful information, in particular or the characterisation of pigments and dyes. Furthermore, the acquired images can also be used for colorimetric applications. In addition, application of a principal components analysis (PCA) algorithm to the spectral data, with the pixels as objects and the wavelengths as variables, has made it possible to show areas painted with different materials as statistically uncorrelated images. Results obtained using this hyperspectral scanner on different polychrome surfaces will be discussed.