Terahertz Paint Thickness Measurements : from lab to automotive and aeronautics Industry

For terahertz sensors to enter the industrial sector, idealized measurements on simplified samples are not sufficient. It must be efficient on any type of substrate. Then, a noncontact sensor to determine the individual thicknesses of multiple paint layers is highly recommended. We report on development of terahertz systems for measuring the thicknesses of multiple paint films for non-contact quality control. The principle of operation is comparable to pulsed ultrasonic imaging but uses broadband terahertz-frequency pulses to which many materials are partially transparent. Then, analysis of time-domain data is described, and the results of measurements made on real industrially-applied structures containing up to five layers found in both automotive and aeronautic industries are presented.