Image spectroscopy (IS) is an important tool for the noninvasive analysis of works of art. It generates a wide sequence of multispectral images from which a reflectance spectrum for each imaged point can be recovered. In addition, digital processing techniques can be employed to divide the images into areas of similar spectral behavior. An IS system designed and developed in our laboratory is described. The methodology used to process the acquired data integrates spectral analysis with statistical image processing: in particular, the potential of principal-component analysis applied in this area is investigated. A selection of the results obtained from a sixteenth-century oil-painted panel by Luca Signorelli is also reported.

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Mid-infrared chalcogenide fiber optics coupled with Fourier transform infrared (FT-IR) benches has made it possible to perform noninvasive reflectance measurements of layers of paint. The technique has potential applications for noninvasive analysis of works of art. These measurements can present large distortions in the spectrum, both in band shape and absorption frequency, which may depend on the band strength, on the concentration of the sample, or on the optical layout of the measuring system. Therefore, it is difficult to compare reflectance spectra with those collected in the transmission mode and, consequently, with the available databases. The work deals with an overall survey of the limits and problems involved in the utilization of this analytical technique, an estimate of the reproducibility of the measurements, and the development of a correct measurement procedure.

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A nanosecond pulsed laser setup has been optimized to perform laser-induced breakdown spectroscopy (LIBS) and pulsed Raman spectroscopy measurements in the field of cultural heritage. Three different samples of artistic/architectural interest with different typologies have been analyzed. The results from the two techniques allowed the identification of the materials used in their manufacture or contaminating them, probably coming from atmospheric pollution and biological activity. No sampling and sample preparation was required before the measurements, and no visual or structural damage was observed. Depth profiling using LIBS was performed in one of the samples, providing elemental information along the different layers composing the object and covering its surface. The quality of the results and the rather short time needed for the measurements and for switching between techniques confirmed the instrument's capabilities and specificity for dealing with objects of artistic or historical interest.