What do U.S. federal investigators and anthropologists at the Smithsonian Institute have in common? They are both pioneering the use of 3D scanning technology to solve challenging mysteries.
Physical shapes hold clues that can be essential in solving tough cases, and a transformation is ocurring in how people work with them. Experts from diverse locations collaborate to solve today's mysteries, and sharing physical evidence requires either transporting the evidence or key personnel. Both are expensive, and fragile evidence can be damaged while enroute. Digital 3D models allow authorized professionals to gain quick access to the information they need, regardless of location. Software that analyzes and compares 3D models can provide hard data that can help to convince juries and experts alike. To gain these benefits, the physical shape must somehow be digitally captured.
3D scanning bridges this gap between physical and digital, capturing highly detailed and accurate 3D models of physical objects. While 3D scanning is not a new concept, the availability of affordable, portable, and easy to operate 3D scanners is now putting this capability within widespread reach. When 3D scanners first surfaced a decade ago, they were the cost of a luxury car and required multiple days of training to operate. Now, they're available for the price of a professional laptop and can be picked up very quickly by first time users.
There are two types of 3D scanners employed in forensics. Crime scene scanners capture a large overview map of a crime scene. This overview map is helpful in understanding the relative position of objects, but the objects themselves are rough 3D shapes. New "close up" 3D scanners capture individual objects in full color and high resolution 3D. This level of resolution allows you to experience the object as if you were actually holding it in your hand.High resolution 3D models can even be beamed back into the real world using a 3D printer.
Most 3D scanners today use lasers to measure 3D information. A laser stripe or dot is moved across a target, and is photographed by a camera at a slight angle to the laser source. Depending on how far away the laser strikes a surface, it will appear at different places in the camera's field of view. This type of capture method is non-contact, meaning it does not touch or affect the original physical sample. For fragile or important forensic samples, this is very important.
It's possible to create castings, but for some items there is a danger of damage to the original in this process. Optically capturing the shapes using a 3D laser scanner provides a portable digital 3D model without any damage to the original. Some 3D scanners also capture the color surface of a physical sample, producing a visually accurate replica that would not be possible with plaster casts. Plaster casts work very well for some applications but are still physical objects that are difficult to share across locations and take up physical storage space. Plaster casts are easily captured by a 3D scanner and can be converted into digital models to solve these issues.