All-Electronic High-Resolution Terahertz Thickness Measurements

Broadband laser based terahertz systems become currently established for inline multilayer paint inspection in the automotive industry. This technology has also proven to be suitable for inspections of certain multilayer plastic structures with up to a few millimeters of thickness. We present a complementary technique for the measurement of dielectric multilayer structures with thicknesses of sub millimeter to several centimeters, using frequency-modulated continuous-wave electronic transceivers. In order to resolve layers below the inherent resolution limit by the modulation bandwidth, we take advantage of model-based signal processing techniques.