Back to Main Menu QUANTITATIVE HYPERSPECTRAL IMAGING OF HISTORICAL DOCUMENTS: TECHNIQUE AND APPLICATIONS

Hyperspectral imaging describes the technique of photographing an object using several well-defined optical bands in a broad spectral range. Using satellite- and aircraft-based instruments, macro-scale hyperspectral imaging is well established for geo-observation with applications in many different fields such as geology, archaeology and defence. Microscope-based hyperspectral instruments and analysis techniques are successfully employed in bio-medical research. In order to transfer this technique to a non-destructive analysis method of historical documents kept in archives and libraries, a dedicated instrument has been specifically designed by request of the Nationaal Archief (National Archive of the Netherlands). This novel tool provides fully calibrated spectral reflectance data at 70 wavelengths ranging from the near-UV (365 nm) via the visible into the near-infrared spectral region (1100 nm). Recordings are made over an area of 125 mm x 125 mm, using low-intensity wavelength-tunable light sources, while the temperature and relative humidity in the instrument measurement cabinet are constantly monitored. Even when recording all wavelength bands, a document is exposed for less than 15 minutes and analysis can be subsequently carried out using the digital dataset at any time for various purposes. This guarantees that the instrument is a completely non-invasive tool that can be applied safely even to objects of great value. Quantitative analysis of the extracted calibrated data can be performed, usin