Inspection of reflective surfaces with deflectometry

Phase-measuring deflectometry combines the advantages of fringe-phase measurement, with sensitivity about 1/1000th fringe of displacement, and surface-slope measurement, with sensitivity especially to small-scale surface disturbances. As opposed to fringe-projection techniques (which rely on surface scattering), deflectometry requires specular reflections. An overview is given of deflectometric signal capture and processing strategies developed in recent years in the ""Image-based Measurement Systems"" workgroup at the Fraunhofer IOSB.