Stereo camera calibration with diffractive optical elements

In order to use stereo camera based measurements in machine vision high accuracy geometric camera calibration is absolutely essential. For many applications it is necessary to use the epipolar constraint to improve matching algorithms or to rectify images with high accuracy which is most important to compute dense disparity maps. The objective is to determine the interior camera parameters including a distortion model as well as the exterior orientation. Therefor we introduce a two-step approach to calibrate a stereo camera system by means of diffractive optical elements. Working as a beam splitter with precisely defined diffraction angles, it produces a well known diffraction point pattern. As the virtual sources of the diffracted beams are points at infinity, the object to be imaged is invariant against translation. This particular feature allows a complete camera calibration with a single image avoiding complex bundle adjustments, resulting in a very fast and reliable single camera calibration procedure. This procedure has been extended for stereo systems to determine the exterior orientation of both cameras. The compact calibration setup also allows an in-field calibration.