It is essential to track welded junction in the process of tube laser welding. During the process of shaping the slot tube of a strip joint during movement toward welding zone moves also on the Y-axis. Every welding system must be equipped with joint-contact watching system and that is why welding head together with laser beam will be able to follow on Y-axis, right after the edge of welded material. Nowadays two methods of joint watching are used, one is mechanical, and the other one is optical (electronic). Mechanical method is watching the joint by "jumping roll", which is placed in a slit of a joint. The roll following the edges of welded material is giving the signals of movement to welding head. The second method used for few years in production of tubes is the CCD sensing system.