Non-contact thickness measurement of coatings on metallic substrate using pulsed terahertz technology

The thickness of aviation materials, including coating thickness, is an important process parameter, which plays an important role in product quality, process control, and cost control. In this paper, a theoretical model of the time-of-flight (TOF) of the coating reflection signal is established by using the terahertz time-domain spectroscopy system, and the method of measuring the thickness of the coating by using the TOF is proposed. The measurement error of the coating sample is less than 5% according to the refractive index information of the coating sample, which has important application value in aerospace coating inspection.