Date of Award:
Master of Science (MS)
Electrical and Computer Engineering
Dr. Doran J. Baker
This thesis presents the application of ash thermography techniques to the analysis of documents. The motivation for this research is to develop the ability to non-destructively reveal covered writings in archaeological artifacts such as the Codex Selden or Egyptian car- tonnage. Current common signal processing techniques are evaluated for their effectiveness in enhancing subsurface writings found within a set of test documents. These processing techniques include: false colorization, contrast stretching, histogram equalization, median altering, Gaussian low-pass altering, layered signal reconstruction and thermal signal reconstruction (TSR), several contrast image definitions, differential absolute contrast (DAC), correlated contrast, derivative images, principal component thermography (PCT), dynamic thermal tomography (DTT), pulse phase thermography (PPT), tying-correlation analysis (FCA), Hough transform thermography (PTHTa), and transmission line matrix tying algorithm (TLMFa). New processing techniques are developed and evaluated against the existing techniques. The ability of ash thermography coupled with processing techniques to reveal subsurface writings and document strikeouts is evaluated. Flash thermography parameters are evaluated to determine most eeffective value for the document. In summary, this thesis reports the following contributions to the existing scientific knowledge: 1. A comprehensive analysis of existing pulsed thermography processing techniques. 2. New pulsed thermography processing techniques that improve upon the results of the existing techniques were developed. 3. A proof-of-concept for detecting subsurface ink writings in documents. 4. Varies the capability of pulsed thermography techniques to detect document strike- outs. 5. Demonstrates the ability to enhance surface writings based on differences in thermal characteristics when optical characteristics do not vary significantly. 6. Demonstrates that pulsed thermography significantly improves upon multi-spectral imaging for subsurface and surface writing enhancement. 7. Provides an evaluation of ash thermography parameters for the most effective document imaging.
Larsen, Cory A., "Document Flash Thermography" (2011). All Graduate Theses and Dissertations. 1018.
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