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.

Laser vibrometry and impedance characterization of piezoelectric microcantilevers

Abstract: This paper gives a precise insight into the frequency response of self-actuating cantilevers, extended to high-order modes An original approach is presented, based on a mixed experimental scheme regarding both impedance and laser Doppler interferometry measurements, performed with an impedance analyser and a vibrometer, respectively, and supported by some computational analysis as well The experimental results obtained by the two different techniques agree reasonably well, as for the location of the resonances in the spectrum is concerned However, certain particular modes, torsionally shaped and detected by the vibrometer, show no impedance change due to symmetry reasons A computational model has been successfully employed and utilized to shed some light on this phenomenon The model demonstrates that the induced reaction charge redistribution cancels out only for those particular torsional modes featuring an anti-symmetrical nature; as a consequence, no impedance change is to be expected in the resonances This explanation perfectly fits the impedance measurements carried out, including the missing torsional modesCorrections were made to this article on 10 April 2007 The greyscale figures were replaced with colour versions

Zeeman laser interferometer errors for high-precision measurements.

Abstract: We present a theoretical analysis of the errors of a Zeeman laser interferometer due to the nonorthogonally elliptic polarizations of laser modes. The polarizations make the measured Doppler frequency-shift signal become a modulated and nonharmonic signal and make the phase shift unstable and nonrepeatable when the signal is measured by a phasemeter. If the orthogonality error between two major axes of the laser polarizations is 6 degrees , the relative errors of the phasemeter output will exceed 200% when the measured phase shift is changed from -16.2 degrees to +3.5 degrees . We also introduce a way to eliminate the errors.

Reducing back-reflections in laser processing systems

Abstract: Systems and methods reduce or prevent back-reflections in a laser processing system. A laser processing system includes a laser source to generate an incident laser beam, a laser beam output to direct the incident laser beam toward a work surface, and a lens to receive the incident laser beam along a first axis of propagation that is substantially perpendicular to the work surface. The lens includes a primary axis that is substantially parallel to, and offset from, the first axis of propagation. The lens is configured to focus the incident laser beam onto the work surface along a second axis of propagation that forms a non-perpendicular angle with the work surface such that at least a substantial portion of a reflected laser beam from the work surface does not return to the laser beam output.

Frequency analysis of turbulent compressible flows by laser vibrometry

Abstract: The objective of this work was the application of laser vibrometry as a tool for non-intrusive measurement of frequency spectra in turbulent flows. A laser vibrometer system together with a signal analyser was used to obtain frequency spectra of density fluctuations across a turbulent free jet. Since laser vibrometry is based on interferometric techniques, the derived signals are path integrals along the measurement beam. Frequency spectra recorded in the rotational symmetric flow were then treated using Abel inversion in order to derive information on local density fluctuations. Results for two different flow conditions were compared to spectral data from a constant temperature anemometer and a pitot-mounted pressure sensor.

Experimental Investigation of Damage Detection in Composite Material Structures Using a Laser Vibrometer and Piezoelectric Actuators

Abstract: An experimental investigation to detect embedded delamination and other forms of damage in heterogeneous structures using smart materials and a laser vibrometer is presented. Typically, piezoelectric actuators and sensors have been used for characterizing the presence of damage in composite structures. However, the interpretation of vibration responses in identifying damage using such a procedure is strongly dependent upon the numbers and types of sensors and actuators used. The use of Vibration Deflection Shapes (VDSs), which are the actual vibration patterns of a structure undergoing steady-state vibration, is an alternative approach that is investigated in this paper. Experiments are conducted on composite structures with piezoelectric actuator patches and embedded delaminations, using the VDS method and a Scanning Laser Doppler Vibrometer. The laser vibrometer provides a dense pattern of measurements of the structural response, which effectively increases sensor density compared to the widely spaced p...