Mid-Infrared Fiber-Optics Reflectance Spectroscopy: A Noninvasive Technique for Remote Analysis of Painted Layers. Part I: Technical Setup

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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