Multispectral documentation and image processing analysis of the papyrus of tomb II at Daphne,Greece

This paper refers to the study of an ancient papyrus, dated ca. 420/430 BC, found in 1981 during an excavation at Daphne, Athens, Greece, using multispectral imaging combined with image processing analysis. It was assumed that the papyrus contained ancient Greek musical notation but the condition of the object hindered the drawing of any conclusion based only on visual examination. This fact, combined with the significance of the object itself, as it is the oldest papyrus which carries Greek text, pointed to the application of non-invasive techniques to enhance its readability. The multispectral imaging carried out in the range of 420–1000 nm enabled the detection of more letters on surface layers, at various places and orientations. False colour imaging proved to yield better results in distinguishing the letters compared to single wavelength recording. In some cases, letters from several layers underneath are revealed in the infrared. The letters present different greylevels according to the layer they belong. An interesting result coming from a simple subtraction of the infrared image at 1000 nm from the visible one at 660 nm is that different layers of the papyrus can be distinguished. The Application of Principal Component Analysis (PCA) showed that the best results, as far as the extraction of the letters from the background is concerned, are obtained when the second and the third images are merged. The automatic extraction of the letters is feasible to some extent but there is a certain amount of noise with similar characteristics that cannot be removed.