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A multispectral tunnel inspection system for simultaneous moisture and shape detection

 
: Vierhub-Lorenz, Valentin; Predehl, Katharina; Wolf, Sebastian; Werner, Christoph; Kühnemann, Frank; Reiterer, Alexander

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Postprint urn:nbn:de:0011-n-5616895 (1.2 MByte PDF)
MD5 Fingerprint: 0d3c2db97555e59ecd86b44419988811
Copyright Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.
Created on: 23.10.2019


Erbertseder, Thilo (Hrsg.) ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Remote Sensing Technologies and Applications in Urban Environments IV : 9-12 September 2019, Strasbourg, France
Bellingham, WA: SPIE, 2019 (Proceedings of SPIE 11157)
Paper 111570T, 7 pp.
Conference "Remote Sensing Technologies and Applications in Urban Environments" <4, 2019, Strasbourg>
English
Conference Paper, Electronic Publication
Fraunhofer IPM ()
tunnel inspection; surface moisture; Water Leakage; laser scanner; Differential Absorption; multispectral

Abstract
In this paper, we present the implementation of a differential-absorption measurement-technique for surface moisture detection into a laser scanner aiding modern tunnel inspections. The use of laser scanners for tunnel inspections can reduce costly tunnel closures and provide digital data, compliant with modern building information modeling (BIM).Unfortunately, available systems are typically limited to pure 3D mapping. The Fraunhofer Institute for Physical Measurement Techniques IPM is developing a novel multi-parameter laser scanning system. For the first time, this system allows the simultaneous measurement of 3D-geometry, remission and surface moisture. The scanner measures simultaneously with two collinear laser beams with distinct wavelengths. One is centered at the absorption band of water at 1450 nm wavelength, while the other, with 1320 nm wavelength, is used as an intensity reference. The intensity ratio gives a good estimate of the surface water content. Additionally, the power of both lasers is modulated with a high frequency. This enables simultaneous measurement of the distance by comparing the phase difference of the backscattered light with a local reference. With this approach, we are able to record up to two million points per second containing distance, intensity and moisture information. Besides the technical implementation, we present point clouds from multiple test objects and surfaces. The presented data nicely demonstrates the ability to differentiate between absolute intensity variations, e.g. caused by dirt, and actual water contamination.

: http://publica.fraunhofer.de/documents/N-561689.html