3D scanner for forensic applications

A new mobile optical scanner for forensic evidence recovery was developed based on fringe projection technique. This scanner is used handheld to acquire quickly the 3D geometry of footwear or tire track impressions directly at the site of crime. The measurement volume is about 320 x 200 x 100 mm³. The lateral resolution is 0.17 mm and the height resolution about 0.04 mm. The 3D scanner can be used outside at least for one hour without interruption or external power supply using rechargeable batteries. The 3D measurement result is present immediately after performing the fringe projection scan. Time synchronized to the 3D dataset a calibrated, high resolution color image can be captured additionally by a mountable digital camera in order to detect 2D features and distortions in the trace. Furthermore, the complete chain of forensic investigation can be performed by a newly developed software system. The software follows the classical investigation methods of plaster casted impression traces with use of the new 3D data instead. It also includes the possibility to compare scanned traces with traces stored in a database. The 3D scanner and examples of scan results are presented.