Under CopyrightKrimi, SoufieneSoufieneKrimiKlier, JensJensKlierJonuscheit, JoachimJoachimJonuscheitFreymann, Georg vonGeorg vonFreymannUrbansky, RalphRalphUrbanskyBeigang, RenéRenéBeigang2022-03-0530.8.20162016https://publica.fraunhofer.de/handle/publica/24470810.1063/1.495540710.24406/publica-r-244708In this contribution, we present a highly accurate approach for thickness measurements of multilayered automotive paints using terahertz time domain spectroscopy in reflection geometry. The proposed method combines the benefits of a model-based material parameters extraction method to calibrate the paint coatings, a generalized Rouard's method to simulate the terahertz radiation behavior within arbitrary thin films, and the robustness of a powerful evolutionary optimization algorithm to increase the sensitivity of the minimum thickness measurement limit. Within the framework of this work, a self-calibration model is introduced, which takes into consideration the real industrial challenges such as the effect of wet-on-wet spray in the painting process.enTerahertz Time Domain Spectroscopythickness measurementTerahertz radiation621621journal article