Extracting the Shape and Roughness of Specular Lobe Objects Using Four Light Photometric Stereo
CARNEGIE-MELLON UNIV PITTSBURGH PA ROBOTICS INST
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Two important aspects of part inspection are the measurement or surface shape and surface roughness. A noncontact method is proposed for measuring surface shape and surface roughness. The method, call four light photometric stereo, uses four lights which sequentially illuminate the object under inspection, and a video camera for taking images of the object. Conceptually, the problem solving has three parts shape extraction, pixel segmentation, and roughness extraction. The shape information is produced directly by three light and four light photometric stereo methods. After one has shape information, we can apply statistical segmentation techniques to determine which pixels are specular and which are nonspecular. Then, one can use the specular pixels and shape information, in conjugation with the simplified Torrance-Sparrow reflectance model to determine the surface roughness. The method has successfully been applied to a number of synthetic and real objects.
- Optical Detection and Detectors