Fully Automated Terahertz Layer Thickness Measurement System

We present a fully automated terahertz sensor system for layer thickness measurements of paint and coatings. The core of the instrument is a fiber coupled THz TDS platform that achieves a spectral bandwidth > 6 THz and a peak dynamic range of more than 100 dB in less than 20 s, which sets a new record for the signal quality of THz TDS systems. The system enables the characterization of up to five-layer coatings with individual thicknesses between 3 mm and several hundred microns. The accuracy of the thickness determination is better than 500 nm.