Inspection of specular surfaces with deflectometry

The Fraunhofer Institute of Optronics, System Technologies and Image Processing IOSB, Karlsruhe, Germany, presents a system for the inspection of specularly reflective surfaces based on deflectometry. The system is suitable for inspecting test parts up to 30 x 10 cm², and in general the size of the testable parts scales with the size of the measurement setup.

The deflectometric method emulates the human eye's perception of defects on reflective surfaces in an excellent way, because a similar physical principle is used: in particular, the local distortion of a regular reference structure provides information about surface defects. These are quickly detected by humans, but are only subjectively evaluated.

The presented measurement method allows a sensitivity that is significantly higher than that of the human eye, and at the same time offers an objectifiable quality criterion through reproducible measurements of the surface curvature.

All types of topographically pronounced defects, such as pimples, dents, waviness, orange peel features or warping can be detected and measured.