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Terahertz thickness determination with interferometric vibration correction for industrial applications

: Pfeiffer, T.; Weber, S.; Klier, J.; Bachtler, S.; Molter, D.; Jonuscheit, J.; Freymann, G. von

Volltext urn:nbn:de:0011-n-4942007 (17 MByte PDF)
MD5 Fingerprint: b91ca95aa5382c4fac781623396d745f
Erstellt am: 23.5.2018

Optics Express 26 (2018), Nr.10, S.12558-12568
ISSN: 1094-4087
Zeitschriftenaufsatz, Elektronische Publikation
Fraunhofer ITWM ()
terahertz thickness determination

In many industrial fields, like automotive and painting industry, the thickness of thin layers is a crucial parameter for quality control. Hence, the demand for thickness measurement techniques continuously grows. In particular, non-destructive and contact-free terahertz techniques access a wide range of thickness determination applications. However, terahertz time-domain spectroscopy based systems perform the measurement in a sampling manner, requiring fixed distances between measurement head and sample. In harsh industrial environments vibrations of sample and measurement head distort the time-base and decrease measurement accuracy. We present an interferometer-based vibration correction for terahertz time-domain measurements, able to reduce thickness distortion by one order of magnitude for vibrations with frequencies up to 100 Hz and amplitudes up to 100 µm. We further verify the experimental results by numerical calculations and find very good agreement.