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.

Electrostatic Transducers for Micro Energy Harvesting Based on SOI Technology

Abstract: This paper describes the modeling, fabrication, and characterization of SOI-based micro- electro-mechanical transducers used for energy harvesting. The electrostatic transducers convert vibrations of a seismic mass by means of variable capacitors realized using comb structures. The seismic mass with comb electrodes is suspended by four 1-mm-long straight beam springs. Transducers with springs of different widths with theoretical resonance frequencies ranging from 96 to 1160 Hz were realized. The frequency behavior of the resonators is investigated using an in-plane vibrometer with nm resolution. Linear and non-linear responses are measured for weak and hard driving excitations, respectively. The effect of the capacitance variation on the harvested power is investigated as well as the application of different resistive loads to the devices.

Pulsed-laser vibrometer using photoelectromotive-force sensors

Abstract: We demonstrate experimentally significant improvement in the sensitivity of photoelectromotive-force (photo-EMF) laser vibrometers using pulsed-light sources. The vibrating surface is discretely sampled by individual laser pulses and recorded by the photo-EMF sensor via the generation of photocurrent pulses whose magnitudes are proportional to the instantaneous surface displacements. With a sufficiently high sampling rate, reconstruction of the vibration wave form can be achieved by conducting envelope (or peak) detection of the resultant series of photocurrent pulses. Significantly higher peak optical power levels of the probe laser pulses, which can be orders of magnitude greater than those of continuous-wave interrogation lasers with the same average power, lead to proportional enhancement in the photo-EMF response and remarkable improvement in detection sensitivity when the photodetection process is initially amplifier noise current limited.

A rapidly scanning laser Doppler anemometer

Abstract: A rapidly scanning directionally sensitive fringe-type laser Doppler anemometer (SLDA) which scans the measurement volume perpendicular to the optical axis of the transmitting optics is described. Scan frequencies up to 60 Hz over scan distances of 40 cm have been used, although scan frequencies up to 150 Hz are possible. The maximum scanning velocity of the measurement volume that can be used is directly proportional to the shift frequency of the Bragg cell since each signal-producing particle must cross a minimum number of fringes to produce a valid signal. Signal-averaging bias is lower with a scanning LDA than with pointwise measurements. Results obtained for a separating turbulent boundary layer show that very good mean and RMS velocity profiles can be obtained in less than 1 min of data acquisition.

Increasing the frequency stability of single‐frequency lasers

Abstract: We have developed an improved technique to increase the stability of single‐frequency lasers by employing a scanning Fabry–Perot interferometer and a stabilized helium neon laser. Our instrument surpasses earlier devices in several key areas. The laser frequency can now be stabilized while scanned across its inherent single‐frequency tuning range. The frequency stability is long term with an increased frequency correction rate of nearly 500 Hz. The laser frequency can be scanned repeatedly with a repetition accuracy equal to the frequency stability. Also, the electronics permit the laser frequency to be swept externally while synchronized with other instruments. Our stabilizer reduced the frequency drift of a commercial ring dye laser to ±1 MHz relative to the reference laser.