24 September 2020 
26 June 2018

Sensor+Test: Real-time layer thickness measurement

For the first time, a cost-efficient and compact measurement system that conducts real-time measurements of the thickness of multi-layer systems has been developed by the Fraunhofer Heinrich Hertz Institute HHI. The solution is an essential technology e.g. for lacquering lines. The new terahertz measurement system will be presented live at Sensor+Test.

Photo: Fraunhofer HHIPhoto: Fraunhofer HHI
T-Sweeper is a cost-efficient and compact measurement system that conducts real-time measurements of the thickness of multi-layer systems for the first time.
A research team led by Björn Globisch, head of the terahertz research group at Fraunhofer HHI, has successfully developed a measuring device that replaces the previously used femtosecond pulse laser with compact continuous-wave laser technology. The fact that this continuous-wave measurement system is capable of eight measurements per second is key to allow real-time measurements without the use of a pulsed laser for the first time.

The principle employed by the Fraunhofer HHI to generate terahertz radiation is based on an optoelectronic process. Using a special semiconductor component, the beat of two continuous-wave lasers is converted into terahertz radiation, which corresponds exactly to the difference frequency of the two lasers. The lack of significant success of terahertz technology in the past is largely due to the properties of the semiconductors used. These properties could initially only be achieved with materials that required illumination at a wavelength of 800 nanometers. This rather exotic wavelength means both the lasers and the optical components of the terahertz system are much too expensive and not robust enough for industrial applications.

Fraunhofer HHI is using lasers that can be adjusted extremely fast (Finisar WaveSource) and by modifying electronics, data capture and algorithms to accommodate the high speeds required. This combination has increased measurement speeds by a factor of 160 compared to previous systems. This has made it possible for the first time to conduct material testing in real-time with continuous-wave terahertz systems.

Inspection of paints and coatings is an important application of non-contact terahertz measurement technologies. Here, layer thickness measurement makes up a significant part of quality assurance and production monitoring.



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24/02/2021 - 25/02/2021 in Dortmund
M + R Dortmund


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