Vision and Modeling of Specular Surfaces

We present the combination of a sensor based on “Phase-Measuring Deflectometry” and a new numerical algorithm to obtain the shape of specular free-form surfaces. The sensor measures the local slope of the surface which then is used to reconstruct the object’s shape. The sensor is calibrated and yields absolute slope data. We solved the inherent ambiguity of deflectometric sensors using a novel stereo method for specular surfaces. The presented reconstruction algorithm interpolates the slope data and thus yields an analytic representation of the surface. It can deal with highly curved objects, is stable against noise, and does not require equidistantly sampled data. With the combination of the sensor and the robust numeric algorithm we are able to obtain the global shape of specular free-form surfaces with micron accuracy. Local details can even be measured in a range of a few nanometers depth variation.