High-resolution FMCW millimeter-wave and terahertz thickness measurements

Schreiner, Nina S.; Baccouche, B.; Sauer-Greff, W.; Urbansky, R.; Friederich, Fabian

doi:10.23919/eumc.2017.8231061

Cited by 5 publications

(2 citation statements)

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“…In the millimeter wave and lower terahertz regime, FMCW systems provide a high dynamic range of up to 70 dB at measurement rates of several kilohertz in connection with higher signal penetration depth than pulsed terahertz systems. Recently, we demonstrated the suitability of such systems for thickness measurements and proved that layer thicknesses even below the Rayleigh resolution limit can be resolved by taking advantage of a model-based signal processing technique [23,24]. In a basic approach, modeled versions of the measurement signal are computed a priori based on estimated properties of the multilayer material system under test.…”

Section: Fmcw Thickness Measurementsmentioning

confidence: 99%

Terahertz Quality Inspection for Automotive and Aviation Industries

Ellrich

Bauer

Schreiner

et al. 2019

J Infrared Milli Terahz Waves

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131

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Nondestructive quality inspection with terahertz waves has become an emerging technology, especially in the automotive and aviation industries. Depending on the specific application, different terahertz systems-either fully electronic or based on optical laser pulses-cover the terahertz frequency region from 0.1 THz up to nearly 10 THz and provide high-speed volume inspections on the one hand and high-resolution thickness determination on the other hand. In this paper, we present different industrial applications, which we have addressed with our terahertz systems within the last couple of years. First, we show three-dimensional imaging of glass fiber-reinforced composites and foam structures, and demonstrate thickness determination of multilayer plastic tube walls. Then, we present the characterization of known and unknown multilayer systems down to some microns and the possibility of measuring the thickness of wet paints. The challenges of system reliability in industrial environments, e.g., under the impact of vibrations, and effective solutions are discussed. This paper gives an overview of state-of-the-art terahertz technology for industrial quality inspection. The presented principles are not limited to the automotive and aviation industries but can also be adapted to many other industrial fields.

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Section: Fmcw Thickness Measurementsmentioning

confidence: 99%

Terahertz Quality Inspection for Automotive and Aviation Industries

Ellrich

Bauer

Schreiner

et al. 2019

J Infrared Milli Terahz Waves

Self Cite

131

View full text Add to dashboard Cite

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“…1, interfere [14], and thus, the distance between the pulse maxima does not resemble the electrical path length anymore, as was assumed in (1). In [11] and [14] computational costly correlation based approaches in time (echo) domain are pursued that need to be implemented on graphic processing units to meet real-time requirements. Instead, we propose to estimate the wall thickness in the domain of the intermediate frequency (IF) signal.…”

Section: B Measuring Thin Pipesmentioning

confidence: 99%

Millimeterwave Radar Systems for In-Line Thickness Monitoring in Pipe Extrusion Production Lines

et al. 2020

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This letter presents algorithms and considerations for the applicability of millimeter wave radar systems as monitoring sensors in the field of plastic pipe extrusion. Since a constant wall thickness of the pipe is a major quality factor of the product, monitoring systems that in-line measure the thickness during the extrusion process are commonly used. Modern ultrawideband radar systems achieve target resolutions in the range of millimeters, allowing competition with wellestablished methods, such as ultrasound sensors, and even expensive photonic Terahertz devices. The authors describe a novel accurate and efficient method to measure the pipe-wall's thickness based on frequency domain evaluation of the material reflection. The general feasibility of W-band radar sensors, as well as the accuracy of the proposed method, is demonstrated by measurements using a moderate size polyvinyl chloride pipe.

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