Reading hidden writing and drawings on papyrus using speckle optical technique and multispectral images

Abstract

We carried out an experimental set-up for reading a hidden drawing under papyrus using an optical technique based on the speckle phenomenon that is observed when a rough surface is illuminated by laser light. We propose the use of several wavelengths of light illumination and adaptive algorithms to process the speckle images. We employ a set of filters to produce better discrimination of the results as visually judged. This approach is a cheap and relatively simple non-destructive and non-invasive procedure that could be extended to other painted objects or subsurface hidings of archaeological interest, as well as, to other dynamic speckle experiments.