Inspection of electrodes in battery production using a multi-channel photonic terahertz radar

Terahertz non-destructive testing offers a highly attractive solution for inline testing of electrode thicknesses in battery production for electric vehicles. Measuring systems with high spectral bandwidths are required to address the thin layers of typically less than 100 μm. In addition, multiple measuring heads are desired at different location on a production line to ensure adequate control at high throughput. We solve this by means of a highly scalable photonic terahertz radar. Its measuring principle is based on frequency-modulated continuous wave technology in conjunction with two-color laser radiation. The number of measuring heads can be easily scaled through the use of laser amplifiers. Another advantage of a photonic continuous wave system is the simple possibility of distributing fiber-coupled measuring heads over long fiber lengths of even more than 100 m. In this article, we show the potential of the system concept by the implementation of an 8-channel system and demonstration of relevant thickness measurements.