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Proceedings Paper

Online terahertz thickness measurement in films and coatings
Author(s): Irl N. Duling III; Jeffrey S. White
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Paper Abstract

Pulsed terahertz systems are currently being deployed for online process control and quality control of multi-layered products for use in the building products and aerospace industries. While many laboratory applications of terahertz can allow waveforms to be acquired at rates of 1 – 40 Hz, online applications require measurement rates of in excess of 100Hz. The existing technologies of thickness measurement (nuclear, x-ray, or laser gauges) have rates between 100 and 1000 Hz. At these rates, the single waveform bandwidth must still remain at 2THz or above to allow thinner layers to be measured. In the applications where terahertz can provide unique capability (e.g. multi-layer thickness, delamination, density) long-term stability must be guaranteed within the tolerance required by the measurement. This can mean multi-day stability of less than a micron. The software that runs on these systems must be flexible enough to allow multiple product configurations, while maintaining the simplicity required by plant operators. The final requirement is to have systems that can withstand the environmental conditions of the measurement. This might mean qualification in explosive environments, or operation in hot, wet or dusty environments. All of these requirements can put restrictions on not only the voltage of electronic circuitry used, but also the wavelength and optical power used for the transmitter and receiver. The application of terahertz systems to online process control presents unique challenges that not only effect the physical design of the system, but can also effect the choices made on the terahertz technology itself.

Paper Details

Date Published: 24 February 2017
PDF: 11 pages
Proc. SPIE 10103, Terahertz, RF, Millimeter, and Submillimeter-Wave Technology and Applications X, 101030T (24 February 2017); doi: 10.1117/12.2256363
Show Author Affiliations
Irl N. Duling III, Luna Innovations (United States)
Jeffrey S. White, Luna Innovations (United States)

Published in SPIE Proceedings Vol. 10103:
Terahertz, RF, Millimeter, and Submillimeter-Wave Technology and Applications X
Laurence P. Sadwick; Tianxin Yang, Editor(s)

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