Analysis of the spectra of degraded documents

The intent of this research was to examine the spectral reflectance of degraded documents to determine whether information is available in regions visible to the human eye. Ultimately we attempt to determine the practicality of manipulating visible (RGB) images to obtain similar information commonly obtained by using infrafred (IR) imaging methods. Charred newspaper was tested as an example of a degraded document. Spectral reflectance of the degraded documents was measured using a fiber optic grating spectrometer. In addition, images were taken of the documents in both the visible (RGB) and infrared (IR) regions of the spectrum. By examining the spectral reflectance at different wavelengths in different areas of the documents, we were able to locate information (i.e., characters) on the documents, and determine the wavelengths where the greatest contrast exists between the text and the charred paper. The areas of interest on the charred pages were imaged in several wavelength bands of the spectrum, including the near-ultraviolet and near-infrared regions. Useful information was observed in the IR images, and we attempted to obtain similar results by digitally manipulating visible light (RGB) images. Our hypothesis, that manipulation of the RGB images (specifically subtraction of channels) will find similar contrasts between text and parchment as found in the IR images, was supported by the research