Fully Automatic Mechanical Scan Range Extension of a Lens-Shifted Structured Light System
Darmstadt, Hochschule, Master Thesis, 2020
Cultural heritage are precious goods which need to be preserved for coming generations. Due to many reasons, e.g., wars or natural decay, those objects are in danger of destruction. In order to prevent them from being lost forever, those objects are digitized as 3D models to be accessible for further generations of mankind, the Fraunhofer Institute for computer graphics research offers a fully automatic 3D digitization system called the CultLab3D. There is already a fully functional system for big objects. However, it is more difficult to scan small objects like coins or rings. Those small objects are often referred to as 2.5D objects because they often got engravings and inscriptions on their surface, which cannot even be felt with ones fingers. Scanning such fine detailed objects needs a system that can measure such details. This is accomplished by the MesoScannerV2, an extension of the CultLab3D. It is designed for the digitization of these 2.5D objects without missing details. The MesoScannerV2 is a structured light system which uses a special variation of the phase shift method in order to improve the accuracy of the digitized 3D model of the object. The structured light-based MesoScannerV2 reaches an advanced depth and lateral resolution due to its specialty, the extension of state-of-the-art fringe patterns by a mechanical lens-shifted surface encoding method. Due to bad data acquisition and due to possible uncertainties of numerical algorithms noise is generated which directly influences the digitized 3D models. Therefore, this thesis aims to reduce the generated noise to get cleaner 3D models. Furthermore, the MesoScannerV2 needs to be future-proof, which requires an automation of the scan process of many objects at the same time. The integration of an automation procedure to the MesoScannerV2 is another topic discussed in this thesis. We show that methods are found to reduce the generated noise significantly in particular, we provide a corresponding evaluation. Further, possible solutions to automate the scan process could be found.