Patent ID: 7971461

Claim:
A method of manufacturing a metal strip which is guided over a number of rolls ( 2 , 3 , 4 , 5 ) in a transporting direction under a strip tension that insures that the strip is flat to a large extent at least between two rolls ( 2 , 3 ), comprising the step of providing a system for making inner tensile stresses in the movable metal strip ( 1 ) optically visible and having a light source ( 6 ) operable for illuminating an area of the strip ( 1 ) as it moves in the transporting direction, and two cameras ( 7 , 8 ) located in a region of the light source ( 6 ) at a distance from each other and operable for photographing the area of the metal strip ( 1 ) illuminated by the light source from two different directions.