The Scientific Working Group for Shoeprint and Tire Tread Evidence (SWGTREAD) recommends it is necessary to “evaluate the viability of imaging and reproducing a shoe or tire impression in snow or soil without the need for, or in lieu of, traditional casting methods”. Despite substantial advancements that have been made in developing noninvasive optical 3D imaging methods, the existing 3D imaging techniques are mainly good for diffuse objects having relatively low surface contrast and high optical surface reflectivity. Research Design and Methods: The proposed project is to develop a novel and portable high-resolution (e.g., 600 dots per inch, or dpi) optical 3D scanning system to measure shoe or tire impressions. The 3D imaging technique is based on the binary defocusing technique and the auto-exposure control method that were recently invented by our team. Preliminary study has demonstrated that this approach permits camera-pixel-resolution 3D imagery capture and enables precise timing control, and thus has the potential to achieve sufficient accuracy and resolution for capturing shoe or tire impression in both snow and soil. Products: Deliverables will include: 1) 3D imaging system that will produce unprecedentedly higher resolution images (i.e., 600 dpi) than any existing technology, remove the need for on-site calibration, be ultra portable (i.e., hand-size and a few pounds) and affordable (i.e., $5,000, or approximately 1/10 of alternatives), be eye safe, and be faster than either casting or alternative 3D imaging technologies; and 2) a few prototype systems will be available for forensic community to test and evaluate. Published papers and presentations on the study results will be provided for others in the field to examine, enabling further development. Impact: This proposed project addresses the Development Goal in this solicitation and is intended to produce a novel system and method for collecting 3D images of tire tread and footwear impressions in difficult materials – snow and soil. The 3D imaging system can also accurately capture prints on uneven surfaces (in blood, dust, dirt, etc.) in an application that is common, problematic, and unreasonably difficult and time consuming for the competing technology (3D laser scanning). This technology will meet the stated objective of improving “front end” evidence collection at crime scenes with a non-contact, rapid, high-resolution method for impression collection. Note: This project contains a research and/or development component, as defined in applicable law.

Song Zhang
Purdue University