3D SCAN (A)HEAD

Abstract

Maatbril delivers personalized 3D-printed glasses by making a 3D scan of their client’s head and modelling the glasses around this 3D model. This is especially handy for people with cranio-facial differences or other conditions that prevent them from wearing regular glasses. A large proportion of Maatbril’s clients are children and/or have a mental disability. Interviews and observations during scanning procedures showed that the 3D scanning procedure is often perceived as scary. Moreover, it is often challenging to get the client to sit still for about 20 to 30 seconds, which is the time it takes to capture the 3D scan. The goal of this project is to design a non-invasive and versatile 3D scanning solution that produces high-accuracy 3D head scans near instantaneously, with simple controls for a single user. This 3D scanner will mainly be used by Maatbril employees, but it might occur as well 3D scanners will be located at healthcare institutions such Bartiméus and people that are no experts in 3D scanning will perform the 3D scan. Experiments and roleplaying with different interaction concepts showed that not all participants have the mental capability to actively contribute in the scanning procedure, ruling out principles like gamification to get the client to sit still. Eventually, it was chosen to attract the client's attention with an integrated tablet which displays videographical content. This requires little mental effort, but still allows for the client to have something interesting to focus on, so he/she will sit (relatively) still. In the meantime, the 3D scan can be captured. The final 3D Head Scanner makes use of 2 Azure Kinect DK sensors to capture the subject’s face along with the requisite landmarks in about 25 milliseconds, with only the click of a button. These sensors work with Amplitude Modulated Continuous Wave (AMCW) Time-of-Flight technology, which was selected after evaluating all options and fit to this use case. About 20 seconds after clicking the button, both scans have been aligned and the quality can be evaluated in the User Interface. The client probably didn't even notice any of this, as he/she was watching their favourite show on the digital tablet. Repeatedly testing and optimizing the interaction of the final 3D Head Scanner resulted in a relaxed and non-invasive 3D scanning procedure, where no force or bribing of the client was required to obtain the 3D scans. After optimizing the alignment algorithm, 3D scans with an accuracy of 1.2 mm can be expected, which is in the range of accuracy Maatbril requires when designing their glasses.