There is a need for tools that can rapidly survey a crime scene and provide nearly real-time (approximately ~1 second processing time, not video rate) information that can assist in planning and prioritizing an investigation; under the current grant, Teledyne Scientific and Imaging Company conducted a proof-of-concept trade study for such a camera and related software processes.
The project fabricated a breadboard prototype imaging system by using strictly commercial off-the-shelf components. The testing of the prototype imaging system demonstrated its functionality in a laboratory environment, using simulated targets likely to be of interest for forensic investigators, e.g., blood and saliva stains, latent prints, chemical stains, powder residue, etc. Contrast enhancement and improved detection threshold were achieved across a wide range of targets. In several cases, the prototype camera was able to capture the target imagery that was invisible to the naked eye and a conventional color digital camera. The illuminator unit of the breadboard has six different illumination channels (one UV, three visible, and two near-infrared) set by emission bands of light-emitting diodes (LEDs). For the camera unit, the project team used a monochrome camera with a multi-spectral lens that can selectively image the targets within the pass-band of six spectral filters matched to LED wavelengths. The polarization of transmit and receive paths can also be controlled. Target images were acquired in different modes (multi-spectral, polarization, and fluorescence). Various contrast-enhancement, filtering, and image-rendering algorithms were applied to the imagery. Frequency domain filtering was applied in numerous cases. False color rendering was used when needed to combine and present information in various imaging channels for viewing. This report describes the hardware fabrication, presents the trade study results in detail, describes various contrast enhancement algorithms, and recommends what is needed to move forward toward a field-portable brass board. 89 figures, 5 tables, 42 references, and a description of research dissemination activities
Date Published: August 1, 2012