Free-form specular surface inspection with adapted coded-light
Abstract
Within the context of optical-based inspection of industrial objects, the automatic characterization of complex free-form surfaces remains a challenging task. In general, different recording modalities, as structured or diffuse lightings, are necessary to interpret the surface to be inspected. Purpose of the paper is to propose a qualitative approach based on previous investigations using the projection of structured patterns. The novelty herein is the adaptation of the pattern to the surface geometry, so that at least surface interpretation can be conducted on the interpretation of regular patterns. The proposed method encompasses (i) an adapted point correspondence specially designed for the processing of specular surfaces, (ii) and an appropriate determination of the transformation between projector and camera images. It is demonstrated that the proposed method is ideally suited for specular surfaces where relevant defects have to be detected. The results are demonst rated by means of examples based on laboratory experiments.
