While flat or spherical specular reflecting surfaces can be measured by interferometric methods, the optical three-dimensional measurement of reflecting free formed surfaces is still a demanding task, especially if the contour features geometric discontinuities. For this scope of application, the authors have developed two techniques for the direct three-dimensional measurement of reflecting surfaces, which are based on the evaluation of the mirror image of a grid-like reference structure. One of these techniques employs a pseudo three-dimensional reference structure in combination with one camera for the recording of the virtual image of the reference pattern, while the other, completely new approach utilises a stereo-photogram-metric camera system in conjunction with a merely two-dimensional reference structure. Both systems allow the unambiguous measurement of reflecting free formed surfaces and may be extended by the photogrammetric combination of numerous single measurements, thus even allowing the measurement of rather complex geometries. In this contribution, the calibration procedure for both systems - in particular the determination of the intrinsic and extrinsic parameters of the reference structure - are discussed. Furthermore, the measuring uncertainty of the present setups is analysed, considering measurements of a plane and a spherical reference object.
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