4 March 2015 Capturing latent fingerprints from metallic painted surfaces using UV-VIS spectroscope
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Abstract
In digital crime scene forensics, contactless non-destructive detection and acquisition of latent fingerprints by means of optical devices such as a high-resolution digital camera, confocal microscope, or chromatic white-light sensor is the initial step prior to destructive chemical development. The applicability of an optical sensor to digitalize latent fingerprints primarily depends on reflection properties of a substrate. Metallic painted surfaces, for instance, pose a problem for conventional sensors which make use of visible light. Since metallic paint is a semi-transparent layer on top of the surface, visible light penetrates it and is reflected off of the metallic flakes randomly disposed in the paint. Fingerprint residues do not impede light beams making ridges invisible. Latent fingerprints can be revealed, however, using ultraviolet light which does not penetrate the paint. We apply a UV-VIS spectroscope that is capable of capturing images within the range from 163 to 844 nm using 2048 discrete levels. We empirically show that latent fingerprints left behind on metallic painted surfaces become clearly visible within the range from 205 to 385 nm. Our proposed streakiness score feature determining the proportion of a ridge-valley pattern in an image is applied for automatic assessment of a fingerprint’s visibility and distinguishing between fingerprint and empty regions. The experiments are carried out with 100 fingerprint and 100 non-fingerprint samples.
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Andrey Makrushin, Tobias Scheidat, Claus Vielhauer, "Capturing latent fingerprints from metallic painted surfaces using UV-VIS spectroscope", Proc. SPIE 9409, Media Watermarking, Security, and Forensics 2015, 94090B (4 March 2015); doi: 10.1117/12.2078876; https://doi.org/10.1117/12.2078876
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