Multispectral Image Archiving of Watermarks in Historical Papers

Multispectral imaging is a technique used today in many quality control applications in industry or the cultural heritage field. Determining the origin of documents is an important task of historians. For this task not only is the visible text relevant but also further information about the physical paper document, such as watermarks. Today historic documents are mostly scanned using reflected visible light but such scans does not provide information about watermarks. For this, historians have to examine the original paper document. But the watermark may not be visible even with the original document due to heavy interference with overlaying ink In this paper the digitization of historic papers using different spectral wavelength bands is discussed in general and the use of infrared bands for the detection of watermarks in particular. The details of a watermark detection system are presented and a concept for combining visual and infrared image digitization is shown.