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Portable Advanced 3D Imaging for Footwear and Tire Impression Capture

Event Dates
Event Duration
90 minutes

This webinar will explain the principles and capabilities of a fully automated portable system with an easy-to use-graphical user interface (GUI) for shoe and tire impression capture. We have four prototype systems ready to be evaluated by interested examiners or practitioners, providing opportunities for users to interact with the system and provide feedback to further improve the technology.

The entire hardware system includes a digital complementary metal-oxide semiconductor (CMOS) camera, a digital-light-processing (DLP) projector, and a laptop computer. The 3D scanning system is being developed in Professor Song Zhang’s laboratory at Purdue University. The system is calibrated during initial assembly and simply needs to be plugged into an outlet and a laptop via a USB3.0 port for immediate data capture. The camera and the projector are precisely synchronized to allow a sequence of defocused binary structured light patterns to be captured by the camera. The captured images are processed to create a 3D surface map at camera-pixel spatial resolution, and simultaneously record a color image (or texture) that is 100% aligned with the 3D surface using the same camera. The image acquisition takes a fraction of a second, and the automated 3D reconstruction takes a few seconds. 3D data can be immediately visualized on the screen for monitoring capture quality or saved to digital storage media in standard 3D mesh formats (e.g., OBJ, STL, PLY).

The graphical user interface (GUI) includes the camera control, visualization, and data handling modules. The entire GUI was developed with Qt, C++, OpengGL, and OpengCV by Professor Song Zhang’s team with the special emphasis on making the GUI intuitive and easy to use. The camera control module allows a user to manually or automatically adjust camera exposure, and then click a button for 3D image acquisition.  The visualization module enables the user to examine the quality of data in both 2D and 3D. This module allows the 3D data manipulation such as zoom-in and zoom-out, rotation, and translation, as well as different visualization mode selections such as shaded, textured, wired or different depth colorization. The data handling module offers data reading and writing, as well as screenshot creation.

The prototype system was designed to capture an area of approximately 14”x10” with a spatial resolution of approximately 137 ppi (pixels per inch).  Our team has conducted two workshops, one at 2018 IPTES (Alexandria, Virginia) and the second one at the 2018 IAI Annual conference (San Antonio, Texas). The system has been extensively tested by our team, the workshop participants, a team of forensic examiners from Omaha Police Department, as well as some volunteers. We have received extremely positive comments on the performance and usability of the system from workshop participants and other evaluators.

Detailed Learning Objectives:

– Familiarize with one advanced 3D imaging instrument specifically for tire and shoe impression capture
– Familiarize with the principle behind such an advanced 3D imaging technology
– Learn how to use such an advanced imaging technology for evidence collection

Date Created: September 23, 2019