Non-contact scanning: Creating three dimensional images

Over recent years, forensic archaeologists and anthropologists have become interested in new ways of recording the crime scene, the body and important evidence. One such approach is by making 3D models of these objects, so that they can be analysed in greater detail later.

There are different methods of scanning. We can use:

• active or passive – methods that fire a beam of energy at an object, and those that just record what is there (like photography)

• surface or internal – methods that only record the surface features or those that record the internal features (like x-rays)

• contact or non-contact – methods that mean you must touch the object with the equipment, and those that do not.

So for example, photography is a passive / surface / non-contact method, while ultrasound is an active / internal / contact method. For forensic work, we tend to need to record the surface of objects in a non-intrusive way. A key advantage of these scanning methods is that they produce 3D models. Standard photography reduces 3D reality to a 2D copy and this can affect how we analyse and interpret interesting features. If you look at the image below you will see how much more effective the 3D image is for interpretation.

Laser scanning

Laser scanning is an active / surface / non-contact method for recording objects. The method works by firing a laser at the area of interest and recording the laser as it bounces back. It can work well on very large objects (we have used it on a train and on a cliff at the beach) but can also be applied to smaller objects. The method is quick, but the equipment can be a little inconvenient.

Laser scanning of a skull

Structured-light scanning

Structured-light scanning (SLS) is also an active / surface / non-contact method, but instead of firing a laser, it uses a grid of white light. The method is better for smaller objects and has the advantage of being cheaper than laser scanning. It is also safer to use on living people since it uses light and not a laser.

We have used this method very successfully, and have created best practice guides for its use on skeletal remains and also for its use in forensic medicine on soft tissues. To access these articles and the ones below, after you click the link, click on ‘full text’ or ‘publication’ in the right hand panel.

You can read about other examples of our use of SLS to examine footwear evidence in crime scene situations, and to analyse sharp force trauma in the Roman period.