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In this study, the potential of visible and near-infrared spectral imaging as a technique of document inspection was
examined. Doubtful documents are often found in economic cases, distinguished between original and added strokes and
detected blurry characters are very useful for judgment. Burned, covered and rinsed documents in which the characters
can't be identified with naked eyes were experimentally studied with a visible spectral imaging technique. Meanwhile,
the same color inks were detected by both visible and near-infrared imaging spectrometers. Classification of spectral
images was carried out in specialist spectral imaging software packager Misystem provided by Institute of Forensic
Science. The technique significantly improved the detection of many documents, especially those that might be
considered of poor quality or borderline characters. The visible spectral imaging was successful in detecting the burnt
Chinese characters produced using pencils. It was possible to form spectral images showing the strokes even covered by
Chinese ink by means of imaging at characteristic frequencies. As inks have very different spectral from the clothes,
contribution and contrast of the rinsed lines and illegible seal words on clothes were clearly enhanced. By examining the
spectral images from the inks, it was possible to determine whether the same color inks were written by the different
pens. The results also show that the near-infrared spectrometer is better than visible one in distinguishing the same inks.
In blind testing, spectral imaging was shown to achieve an average 85.1% chance of success. The results reveal the wide
applications of spectral imaging in document evidence analysis. The potential of this technique in forensic science will
be more apparent along with the further and deeper studies.
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