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Laser Doppler Sensors
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Laser Doppler Sensors

A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Electronic Sensors".

Deadline for manuscript submissions: closed (20 March 2021) | Viewed by 18240

Special Issue Editors

Prof. Dr. Christian Rembe

E-Mail Website
Guest Editor
Institute of Electrical Information Technology, Clausthal University of Technology, Leibnizstr. 28, D-38678 Clausthal-Zellerfeld, Germany
Interests: optics; optical measurement techniques; sensors; MEMS
Dr. Ben Halkon

E-Mail Website
Guest Editor
School of Mechanical and Mechatronic Engineering, University of Technology Sydney, Sydney, Australia
Interests: structural analysis; finite element modeling; sports science engineering; structural dynamics; experimental dynamics; FE analysis; dynamic analysis; sport biomechanics; dynamics; laser

Special Issue Information

Dear Colleagues,

Laser Doppler vibrometers, laser Doppler anemometers, laser surface velocimeters, and laser Doppler extensometers are sensors based on laser Doppler technology. Such sensors utilize an interferometric detection scheme and broadband demodulation of the derivative of the interference phase. Since the derivative of the interference phase corresponds to the laser Doppler frequency shift generated by a moving target reflecting or scattering the measuring laser beam, such sensors are called laser Doppler sensors.

Special techniques such as heterodyning, signal diversity, and multiwavelength length detection make laser Doppler sensors reliable, accurate, and highly sensitive. For example, the detection of backscattered measuring light power in the femtowatt range is just as possible as the detection of picometer deflections. Laser Doppler sensors therefore influence many research areas and industrial applications. Such sensors are commercially available and widely used. However, laser speckles for measurement on rough surfaces have a negative influence on laser Doppler sensors. The high intensity dynamics of laser Doppler sensors were the only lever to deal with the influence of laser speckles. Recent developments have even enabled speckle-insensitive laser Doppler sensors. The treatment of laser speckles is only one example of the many research topics in the field of laser-Doppler sensors that are currently being addressed by various research groups worldwide. Other topics include, for example, suppression of the sensor’s self-movement, tracking of moving objects, multichannel detection, fusion of data with that from other sensors and measurements of microscopic objects.

This Special Issue on laser Doppler sensors deals with the latest findings and developments, and contemporary applications in sensors based on laser Doppler techniques.

Dr. Christian Rembe
Dr. Ben Halkon
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sensors is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Published Papers (4 papers)

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Research

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15 pages, 4008 KiB  
Article
Using a Retro-Reflective Membrane and Laser Doppler Vibrometer for Real-Time Remote Acoustic Sensing and Control
by Tong Xiao, Sipei Zhao, Xiaojun Qiu and Benjamin Halkon
Sensors 2021, 21(11), 3866; https://doi.org/10.3390/s21113866 - 03 Jun 2021
Cited by 6 | Viewed by 3290
Abstract
Microphones have been extensively studied for many decades and their related theories are well-established. However, the physical presence of the sensor itself limits its practicality in many sound field control applications. Laser Doppler vibrometers (LDVs) are commonly used for the remote measurement of [...] Read more.
Microphones have been extensively studied for many decades and their related theories are well-established. However, the physical presence of the sensor itself limits its practicality in many sound field control applications. Laser Doppler vibrometers (LDVs) are commonly used for the remote measurement of surface vibration that are related to the sound field without the introduction of any such physical intervention. This paper investigates the performance and challenges of using a piece of retro-reflective film directly as an acoustic membrane pick-up with an LDV to sense its vibration to form a remote acoustic sensing apparatus. Due to the special properties of the retro-reflective material, the LDV beam can be projected to the target over a wide range of incident angles. Thus, the location of the LDV relative to the pick-up is not severely restricted. This is favourable in many acoustic sensing and control applications. Theoretical analysis and systematic experiments were conducted on the membrane to characterise its performance. One design has been selected for sensing sound pressure level above 20 dB and within the 200 Hz to 4 kHz frequency range. Two example applications—remote speech signal sensing/recording and an active noise control headrest—are presented to demonstrate the benefits of such a remote acoustic sensing apparatus with the retro-reflective material. Particularly, a significant 22.4 dB noise reduction ranging from 300 Hz to 6 kHz has been achieved using the demonstrated active control system. These results demonstrate the potential for such a solution with several key advantages in many applications over traditional microphones, primarily due to its minimal invasiveness. Full article
(This article belongs to the Special Issue Laser Doppler Sensors)
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16 pages, 13214 KiB  
Article
Signal Diversity for Laser-Doppler Vibrometers with Raw-Signal Combination
by Marvin Schewe and Christian Rembe
Sensors 2021, 21(3), 998; https://doi.org/10.3390/s21030998 - 02 Feb 2021
Cited by 8 | Viewed by 3116
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Laser Doppler Sensors)
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14 pages, 3455 KiB  
Article
A Contactless Laser Doppler Strain Sensor for Fatigue Testing with Resonance-Testing Machine
by Fangjian Wang, Steffen Krause, Joachim Hug and Christian Rembe
Sensors 2021, 21(1), 319; https://doi.org/10.3390/s21010319 - 05 Jan 2021
Cited by 6 | Viewed by 4088
Abstract
In this article, a non-contact laser Doppler strain sensor designed for fatigue testing with the resonance-testing machine is presented. The compact sensor measures in-plane displacements simultaneously from two adjacent points using the principle of in-plane, laser-Doppler vibrometry. The strain is computed from the [...] Read more.
In this article, a non-contact laser Doppler strain sensor designed for fatigue testing with the resonance-testing machine is presented. The compact sensor measures in-plane displacements simultaneously from two adjacent points using the principle of in-plane, laser-Doppler vibrometry. The strain is computed from the relative displacements divided by the distance between these two points. The optical design, the mathematical model for estimating noise-limited resolution, the simulation results of this model, and the first measurement results are presented. The comparison of the measurement results of our sensor with the results of a conventional strain gauge shows that our design meets the measurement requirements. The maximum strain deviation compared to conventional strain gauges of the laser-Doppler extensometer is below 4×10−5 in all performed experiments. Full article
(This article belongs to the Special Issue Laser Doppler Sensors)
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Review

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25 pages, 5309 KiB  
Review
Miniaturization of Laser Doppler Vibrometers—A Review
by Yanlu Li, Emiel Dieussaert and Roel Baets
Sensors 2022, 22(13), 4735; https://doi.org/10.3390/s22134735 - 23 Jun 2022
Cited by 13 | Viewed by 6520
Abstract
Laser Doppler vibrometry (LDV) is a non-contact vibration measurement technique based on the Doppler effect of the reflected laser beam. Thanks to its feature of high resolution and flexibility, LDV has been used in many different fields today. The miniaturization of the LDV [...] Read more.
Laser Doppler vibrometry (LDV) is a non-contact vibration measurement technique based on the Doppler effect of the reflected laser beam. Thanks to its feature of high resolution and flexibility, LDV has been used in many different fields today. The miniaturization of the LDV systems is one important development direction for the current LDV systems that can enable many new applications. In this paper, we will review the state-of-the-art method on LDV miniaturization. Systems based on three miniaturization techniques will be discussed: photonic integrated circuit (PIC), self-mixing, and micro-electrochemical systems (MEMS). We will explain the basics of these techniques and summarize the reported miniaturized LDV systems. The advantages and disadvantages of these techniques will also be compared and discussed. Full article
(This article belongs to the Special Issue Laser Doppler Sensors)
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