Reflection Characterization: 3D shape measurement of a surface using its diffuse and specular reflections

The geometric optical metrology methods Pattern Projection and Deflectometry are designed for the measurement of objects with diffusely reflective and specular reflective surfaces respectively. Real surfaces however show a reflection behaviour which cannot be described by using one of these reflection models solely. Especially for technical, comparably diffusely reflective and specular reflective surfaces, choosing which of the two measurement techniques mentioned above is best suitable for measurement is difficult; for objects with unknown reflection characteristics, it is impossible. In this contribution the Reflection Characterization method is presented, which is based on evaluating the reflective behaviour of a measurement surface by performing phase measurements with a combined pattern projection / deflectometry setup, and adaptive fusion of the recorded data for shape evaluation based on the determined reflection properties.