Topic
Laser Doppler vibrometer
About: Laser Doppler vibrometer is a research topic. Over the lifetime, 6319 publications have been published within this topic receiving 76068 citations.
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TL;DR: In this paper, the sensitivities of heterodyne and direct-detection systems at CO2 laser wavelengths are compared to illuminate the design principles involved, and it is shown that destruction of the temporal coherence of scattered radiation is a significant effect when heter-odyne systems are used on targets with internal motion.
Abstract: The sensitivities of heterodyne and direct-detection systems at CO2 laser wavelengths are compared to illuminate the design principles involved. It is shown that destruction of the temporal coherence of scattered radiation is a significant effect when heterodyne systems are used on targets with internal motion. The complete system and the results obtained are then described. The compact optics head contains a waveguide laser, an acousto-optic modulator and SAW chirp devices; it has 45 mm diameter transmit and receive apertures. Whem many returns are integrated, ranges of several kilometres are obtained off natural targets with an accuracy of 10 m. From the Doppler shift off a moving target, radial velocity can be determined simultaneously with the range when an up-chirp/down-chirp technique is used; an accuracy of better than 1 m s−1 is demonstrated.
38 citations
TL;DR: In this article, a portable laser vibrometer is described which allows the engineer to simply point a laser beam at a target surface in order to obtain a measure of its vibrational velocity level in amplitude and phase.
38 citations
TL;DR: In this article, a rapid imaging technique is proposed for imaging damage in metallic plates using a zero-lag cross-correlation imaging condition in the frequency domain, which is a fully non-contact, single-sensor approach.
Abstract: In this work, a rapid imaging technique is proposed for imaging damage in metallic plates using a zero-lag cross-correlation imaging condition in the frequency domain. A fully non-contact, single-s...
38 citations
TL;DR: In this article, a structural health monitoring (SHM) strategy is proposed in order to detect disbonds in a composite lap-joint, which is composed of a carbon fiber reinforced polymer (CFRP) bonded to a titanium plate.
Abstract: In this study, a structural health monitoring (SHM) strategy is proposed in order to detect disbonds in a composite lap-joint. The structure under study is composed of a carbon fiber reinforced polymer (CFRP) bonded to a titanium plate and artificial disbonds are simulated by inserting Teflon tapes of various dimensions within the joint. In situ inspection is ensured by piezoceramics bonded to the structure to generate and measure guided waves. Theoretical propagation and through-thickness stress distribution are first studied in order to determine damage sensitivity with respect to the mode and frequency of the generated guided wave. The optimal configuration of the system in terms of piezoceramic size, shape and inter-unit spacing is then validated using finite element modeling (FEM) in 3D. Experimental assessment of propagation characteristics is conducted using laser Doppler vibrometer (LDV) in order to justify theoretical and numerical assumptions and pitch–catch measurements are then performed to validate the efficient detection of the damage and accurate estimation of its size.
38 citations
TL;DR: In this article, a CO2 sensor using single-walled carbon nanotubes (CNT) and a microelectromechanical system (MEMS) resonator is demonstrated.
Abstract: A CO2 sensor using single-walled carbon nanotubes (CNT) and a microelectromechanical system (MEMS) resonator is demonstrated. The MEMS transducer comprises a membrane driven into transverse vibrations by means of Lorentz forces. A downshift in the resonant frequency of the device is measured by a laser vibrometer when changes in the stress state of the CNT film∕membrane structure are caused by adsorption of CO2 onto the nanotubes. The sensor has shown excellent sensitivity, linearity, and recovery over a broad range of concentrations (0–15vol%). In comparison to resistive, dielectric, and gravimetric CNT transducers, this sensor displayed remarkable intrinsic selectivity in the presence of interferences.
38 citations