HoloTop is an optical measurement system for contactless, high-precision, and fast 3D-surface topography of building blocks during the production process. This becomes possible through using the Multi-Lambda-Digital-Holographie (MLDH). The system is so stable and fast that it accurately finds and detects even small defects on functional surfaces during the quality control in step with the industrial production. In particular, the topography of rough object surfaces can be measured without limits in depth-of-field, with interferometric accuracy. http://www.vision.fraunhofer.de/de/presse/315.html