6 June 2011 New trends in imaging spectroscopy: the non-invasive study of the Scrovegni Chapel stained glass windows
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Imaging spectroscopy (IS) extends the measurement of one-dimensional UV-VIS-NIR spectroscopy to two-dimensional domain providing material characterization and localization. The technique is gaining importance for the study of cultural heritage but its application is mainly focused on the analysis of pigments in paintings. An IS device has been developed and then applied to the study of chromophores in glassy objects. It consists of a visible imaging spectrograph, mounted on a rotation stage, which captures monochromatic images of the sample within a wavelength range from 420 nm to 850 nm. The system has been used for the characterization and mapping of chromophores of hundreds of coloured glass tesserae of the stained glass windows from the Scrovegni Chapel (Padua, Italy). Two measurement methodologies have been performed: transmission and double-transmission modes. In the first case, lamps used to illuminate the sample and the spectrograph are placed on the opposite side of the window, to acquire directly the signal transmitted from the glass. In the latter case, the lamps and the spectrograph are placed on the same side of the window, that is placed on a white scattering screen. The acquired signal comes from the light of the lamps transmitted through the glass, then diffused back by the opaque white screen and finally transmitted again through the glass. Results are discussed comparing both modalities in terms of signal-to-noise ratio and spectral contrast. Visible spectra acquired allow the clear identification of several chromophores, e.g. Co(II), Cr(III) or Mn(III). The IS device acquires numerous spectra in relatively short time in a non-invasive way. According to the authors knowledge, this is the first time in which visible imaging spectroscopy technique has been applied for the study of stained glass windows. As the results show, it could represent a powerful and innovative tool to map chromophores of this kind of artefact, particularly when integrated with other non-invasive techniques as X-ray fluorescence.
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E. Rebollo, E. Rebollo, F. Ratti, F. Ratti, G. M. Cortelazzo, G. M. Cortelazzo, L. Poletto, L. Poletto, R. Bertoncello, R. Bertoncello, "New trends in imaging spectroscopy: the non-invasive study of the Scrovegni Chapel stained glass windows", Proc. SPIE 8084, O3A: Optics for Arts, Architecture, and Archaeology III, 808407 (6 June 2011); doi: 10.1117/12.888839; https://doi.org/10.1117/12.888839

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