More stringent customer requirements and productivity give steelmakers an incentive to deliver higher surface quality strips. To controland to improve the surface properties, CRM has developed a sensorgrabbing highly magnified images of a moving product. The chosenmethod is based on the principle of triangulation: a very thin line is projected on the surface and the relief is calculated by the analysis of linedeformation. The result is an on-line 3D analysis sensor for assessing topography.