Terahertz car paint thickness sensor: Out of the lab and into the factory

A terahertz sensor to determine the individual thicknesses of car paint layers is deployed onto the factory floor of an automotive manufacturer. When illuminated with an incident terahertz pulse, reflections from the interfaces between layers are combined and detected. To precisely measure real paint formulations of representative thickness in situ on large curved panels, detailed calibrations of the refractive indices are required. We describe innovation to ensure that the instrument remains viable in the hostile environment of an industrial production line.