L5_CHEM480_JCCYu - Forensic Light Sources 75 Watt 300 Watt...

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1 75 Watt Quartz Halogen Vis (visible only) 300 Watt Xenon UV-Vis-IR Crime-lite LED 5 watt wave length specific 400 Watt Metal Halide UV-Vis-IR Forensic Light Sources 500 Watt Xenon UV-Vis-IR 80S Crime-lite LED 16 LED array wave length specific Note: Xenon has flat response in visible region. Metal Halide has sharp peaks in visible region. LED’s provide color specific output.
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2 Forensic Light Sources ± Quartz Halogen - Has no UV ² Metal Halide - Has limited UV and has very sharp peaks within the visible region which means the barrier filter has to “work harder” Xenon Has good UV and a flat (relatively) ² Xenon - Has good UV and a flat (relatively) response in the VIS region – use only small % of their output power ² LED - Wave Length Specific – exceptionally long life and use nearly all of their output Application of Forensic Light Source ± Major manufacturer of forensic light source ± Spex Forensics, http://www.crimescope.com/ ± Coherent, http://www.coherent.com/index.cfm ± forster+freeman, http://www.fosterfreeman.com/ ± projectina, http://www.projectina.ch/ ± Rofin Polilight® PL500, http://www.redwop.com/
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3 Expanding our Detection Limits ± Light Sources allow us to find and visualize more evidence ± To work efficiently we need to understand how they work. ± Understand light ± How to detect light (Imaging) Light as a tool Light as a tool is used to gather information in all fields of forensic science Document Crime Scene Shoe Print Biological Fluids Examination Examination Examination Examination Gun Shot Residue Detection Latent Fingerprint Detection Fibers Detection Three modes of operation 1. Absorption Mode – Ex: Blood Prints absorb @415nm 2. Specific Illumination Mode – Ex: Enhancing contrast against a colored background by varying the angle of incidence of the source light others refer to this as spectral illumination 3. Fluorescence Mode – Ex: fluorescence of DFO/Rhodamine 6G
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This note was uploaded on 04/02/2009 for the course CHM 480 taught by Professor Yu during the Spring '09 term at Sam Houston State University.

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L5_CHEM480_JCCYu - Forensic Light Sources 75 Watt 300 Watt...

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