A light beam is directed towards a surface along a direction normal to the surface. The surface is caused to move so that the beam scans the surface along a spiral path. An ellipsoidal mirror is placed with its axis along the surface normal to collect light scattered by the surface and any anomalies...http://www.google.com.au/patents/US6606153?utm_source=gb-gplus-sharePatent US6606153 - Process and assembly for non-destructive surface inspections
