Camera based monitoring of the rigid body displacement of a mandrel in superconducting cable production

We describe a machine vision measurement head that is used to monitor the mandrel in cable production. Two cameras are orthogonally aligned, viewing different sections of the cylindric mandrel surface. The use of telecentric lenses obviates the need for re-calibration after changing the mandrel. All parameters of rigid body motion are obtained in linear theory by using a multi-variate least squares fit procedure on dynamically corresponded sets of target points that vary due to obstruction by rotating wires. A rigorous analysis of measurement uncertainty is given.