On scene-adapted illumination techniques for industrial inspection

In many machine vision applications for automated inspection the illumination design is crucial to the robustness and speed of the inspection process. Hence, there is need to investigate and to experimentally evaluate new illumination designs and techniques. We briefly review a representative selection of illumination techniques that aim to minimize the effort of defect detection by adapting the illuminating light field to the nominal state of the inspection task. Based on this principle we propose an illumination technique using a projector-camera system which provides inspection images that directly display differences in the reflectance between two scenes. A comparison with image differencing for deviation detection shows that the proposed illumination technique is in many cases advantageous from a signal-to-noise point of view.