Up to four rails can be inserted in a marking machine for stainless steel rails. The position in which these rails are lying must be detected so that marking is done only there. The rails are about 2 mm away from the background; the working distance is about 200 mm.
This problem is solved by positioning four laser diffuse sensors with background suppression above the rails to check where the rails are inserted. The LHT 81 is ideally suited in this application because of its high function reserve, very good background suppression and 2 mm real detection range at a distance of 200 mm.