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Optical Engineering

Wide-field time-resolved luminescence imaging and spectroscopy to decipher obliterated documents in forensic science
Author(s): Mototsugu Suzuki; Norimitsu Akiba; Kenji Kurosawa; Kenro Kuroki; Yoshinori Akao; Yoshiyasu Higashikawa
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Paper Abstract

We applied a wide-field time-resolved luminescence (TRL) method with a pulsed laser and a gated intensified charge coupled device (ICCD) for deciphering obliterated documents for use in forensic science. The TRL method can nondestructively measure the dynamics of luminescence, including fluorescence and phosphorescence lifetimes, which prove to be useful parameters for image detection. First, we measured the TRL spectra of four brands of black porous-tip pen inks on paper to estimate their luminescence lifetimes. Next, we acquired the TRL images of 12 obliterated documents at various delay times and gate times of the ICCD. The obliterated contents were revealed in the TRL images because of the difference in the luminescence lifetimes of the inks. This method requires no pretreatment, is nondestructive, and has the advantage of wide-field imaging, which makes it is easy to control the gate timing. This demonstration proves that TRL imaging and spectroscopy are powerful tools for forensic document examination.

Paper Details

Date Published: 13 January 2016
PDF: 6 pages
Opt. Eng. 55(1) 014101 doi: 10.1117/1.OE.55.1.014101
Published in: Optical Engineering Volume 55, Issue 1
Show Author Affiliations
Mototsugu Suzuki, Metropolitan Police Dept. (Japan)
Norimitsu Akiba, National Research Institute of Police Science (Japan)
Kenji Kurosawa, National Research Institute of Police Science (Japan)
Kenro Kuroki, National Research Institute of Police Science (Japan)
Yoshinori Akao, National Research Institute of Police Science (Japan)
Yoshiyasu Higashikawa, National Research Institute of Police Science (Japan)

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