Inspecting the surface for the smallest grooves and scratches, especially on an inhomogeneous surface, is a major challenge with conventional lighting and evaluation and usually leads to a high proportion of pseudo-scrap. 

The problems can be solved by using SFS technology (shape from shading). GEFRA has been using SFS testing in the OPTISORT testing system for many years if necessary. For most of the stamping parts it is necessary to use SFS from top and buttom. The latest generation SFS can process both stations from top and buttom with one PC and performance of up to 600 / min.

The setting is done using the well-known AutoControl software and so it is easy to handle.
The SFS process is based on 4 images per part or area; each of these images is taken with a different lighting direction.
Different colors on the surface of the part have no influence on the SFS image, only scratches, depressions, particles, etc.

An algorithm combines the information from the 4 images into one image, which is based on a gray value for the center of the surface.

Higher areas are shown brighter, deeper areas are shown darker. All of our standard inspection tools can be used on this image to evaluate the surface defects.