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Article

Signal Diversity for Laser-Doppler Vibrometers with Raw-Signal Combination

Institute of Electrical Information Technology, Clausthal University of Technology, Leibnizstr. 28, D-38678 Clausthal-Zellerfeld, Germany
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Author to whom correspondence should be addressed.
Academic Editor: Steve Vanlanduit
Sensors 2021, 21(3), 998; https://doi.org/10.3390/s21030998
Received: 28 December 2020 / Revised: 23 January 2021 / Accepted: 27 January 2021 / Published: 2 February 2021
(This article belongs to the Special Issue Laser Doppler Sensors)
The intensity of the reflected measuring beam is greatly reduced for laser-Doppler vibrometer (LDV) measurements on rough surfaces since a considerable part of the light is scattered and cannot reach the photodetector (laser speckle effect). The low intensity of the reflected laser beam leads to a so-called signal dropout, which manifests as noise peaks in the demodulated velocity signal. In such cases, no light reaches the detector at a specific time and, therefore, no signal can be detected. Consequently, the overall quality of the signal decreases significantly. In the literature, first attempts and a practical implementation to reduce this effect by signal diversity can be found. In this article, a practical implementation with four measuring heads of a Multipoint Vibrometer (MPV) and an evaluation and optimization of an algorithm from the literature is presented. The limitations of the algorithm, which combines velocity signals, are shown by evaluating our measurements. We present a modified algorithm, which generates a combined detector signal from the raw signals of the individual channels, reducing the mean noise level in our measurement by more than 10 dB. By comparing the results of our new algorithm with the algorithms of the state-of-the-art, we can show an improvement of the noise reduction with our approach. View Full-Text
Keywords: speckle; laser-doppler vibrometry; LDV; diversity reception; signal diversity; laser speckle speckle; laser-doppler vibrometry; LDV; diversity reception; signal diversity; laser speckle
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MDPI and ACS Style

Schewe, M.; Rembe, C. Signal Diversity for Laser-Doppler Vibrometers with Raw-Signal Combination. Sensors 2021, 21, 998. https://doi.org/10.3390/s21030998

AMA Style

Schewe M, Rembe C. Signal Diversity for Laser-Doppler Vibrometers with Raw-Signal Combination. Sensors. 2021; 21(3):998. https://doi.org/10.3390/s21030998

Chicago/Turabian Style

Schewe, Marvin, and Christian Rembe. 2021. "Signal Diversity for Laser-Doppler Vibrometers with Raw-Signal Combination" Sensors 21, no. 3: 998. https://doi.org/10.3390/s21030998

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