Highly accurate thickness measurement of multi-layered automotive paints using terahertz technology

Abstract

In 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

Non-Contact, Non-Destructive Testing in Various Industrial Sectors with Terahertz Technology

“…For example, in determining paint layer thickness in the car manufacturing industry, existing ultrasound techniques require physical contact between the sensing head via a gel medium; this restricts the use of ultrasound on dry paint. Terahertz, on the other hand, can be used without any physical contact, providing information on fresh paint layers and the drying process [30].…”

“…Krimi et al demonstrated the successful point measurement of a multilayer paint coating with a fibre-coupled spectrometer [30]. The TDS spectrometer was set up in reflection mode.…”

Design and fabrication of 3-D printed conductive polymer structures for THz polarization control

“…Terahertz (THz) radiation has attracted the attention in a wide range of fields, including, but not limited to, in vivo biomedical characterisation [1,2], the automotive industry [3], botanics [4] cultural heritage [5] and materials characterization [6]. Thus, devices able to manipulate THz radiation are in high demand.…”

Non-destructive analysis of flake properties in automotive paints with full-field optical coherence tomography and 3D segmentation

“…Recently, non-contact terahertz pulsed imaging (TPI) has been applied to automotive coating measurements [8][9][10]. TPI focuses a terahertz pulse onto a sample, then collects and characterises the reflected and backscattered pulse [11][12][13].…”

“…By measuring the time delay between terahertz pulses reflected on the sample surface and its inner structure, the layer thickness can be determined. It has been demonstrated as a tool for measuring the thickness of individual paint layers and mapping the thickness distribution of multi-layered automotive paint samples [8][9][10]. However, the lateral resolution of TPI is limited by its wavelength to no lower than 150 -250µm [13].…”