Gradient space analysis of surface defects using a photometric stereo derived bump map

摘要

An innovative method has been developed for the quantification of the surface quality of Lambertian component materials, while in the presence of a complex coincident albedo pattern. The technique uses a generic lighting configuration and is insensitive to component object pose. This is of considerable advantage for the relaxation of environmental structuring during on-line component inspection. A two-stage inspection strategy is proposed, consisting of an initial global surface assessment, together with the subsequent classification of segmented surface defect features. The technique has particular application for the detection of characteristic surface faults, such as indentations, protrusions or missing surface topology, typical of a range of manufacturing processes, including injection moulding, machining and stone polishing. The technique has been validated using a variety of flat and curved specimen components. Experimental results are presented in the paper.