Already in extensive use in remote sensing (1) and astronomy (2), imaging spectroscopy is still in its infancy in the conservation field. To address this shortfall, research is being undertaken to adapt spectroscopic imaging to the non-destructive examination of works of art. By combining the three technologies of digital imaging, reflectance spectroscopy, and multivariate computer analysis, it is possible to determine the composition of materials insitu. Similar to infrared reflectance technology (3), this involves using a Charge Coupled Device (CCD) camera for image capturing, in this case across the ultraviolet, visible and near infrared regions. In combination with narrow-band interference filters, a series of images is built up into a multi-spectral datacube. Reflectance spectra of individual areas of the painting are obtained by slicing across the datacube. In many cases these can be used to identify and differentiate between pigments, e.g. blues with otherwise the same hue. Unique reflectance spectra also permit developing spatial maps of each pigment used across a given painting. Discussion will focus on its application to several case study paintings. Part of this research will focus on developing an economical imaging and processing system for museums, while in the long term, an imaging system that can capture UV fluorescence, visible spectral reflectance and IR reflectance is proposed, which would enable the complete optical characterisation of paintings and provide a powerful tool for conservation.
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- Centre for Remote Imaging, Sensing, and Processing, National University of Singapore 2001, viewed 29 April 2005, http://www.crisp.nus.edu.sg/~research