Terahertz time-domain technology for thickness determination of industrial relevant multi-layer coatings

Nowadays, aircrafts and cars are coated with several layers of coating. Hence, demands for thickness monitoring of each individual layer within a multi-layer coating system are rising. Industrially established techniques for coating thickness control have limits when analyzing multi-layer systems. Terahertz technology using time-domain spectroscopy with a time-of-flight-measurement principle has shown a great potential to fulfill all the desired requirements. Combining different evaluation algorithms we are able to determine all layer thicknesses from 5 mm to 500 mm with an accuracy down to 1 mm within only one second. We demonstrate this ability at relevant industrial coating systems.