Abstract: Surface defects on a substrate (11) are detected by raster scanning the surface (10) with a laser beam (12). Light scattered by the substrate at a large angle with respect to a normal to the surface is collected by at least two bundles of light guide fibers (21,22) located nearly in the plane of the substrate surface, one fiber bundle parallel to the laser scan with the other positioned perpendicularly thereto. The light collected by each bundle is separately processed by a computer (20) to determine the size, in three dimensions, and orientation of defects on the substrate surface. In a preferred embodiment, four light guide fiber bundles (31,32,33 and 34) are used around the substrate surface with the outputs being separately processed.