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.

Fibre Bragg Gratings for the Monitoring of Wooden Structures

Abstract: The aim of this work was to develop and validate an experimental methodology suitable for analysing on-site the behaviour of fibre-reinforced wooden structures. The proposed measurement method is based on the application of fibre Bragg grating (FBG) strain sensors. An analysis of adhesive behaviour was performed preliminarily, which provided indications for choosing the type of adhesive and for the fibre bonding length in accordance with the volume of measurement. The first series of tests was carried out on wood samples to verify the coupling between the measuring sensor and the wood support when the latter is subject to mechanical stresses. The second investigation was done on site to test the behaviour of a historical wood floor before and after reinforcement by means of a series of tests performed using optical fibres with the Bragg grating. The optical fibre system measurements were compared to those obtained using a laser vibrometer, a measurement system of proven stability and precision. The comparison makes it possible to confirm the validity of the results and the reliability of the system for the monitoring of historic wooden structures.

Measurement of translational and angular vibration using a scanning laser Doppler vibrometer

Abstract: An experimental procedure for measuring angular rotation vibration as well as translation, using a continuously-scanning Laser Doppler Vibrometer, is described. Sinusoidal scanning enables one angular vibration component to be measured but, by circular scanning, two principal angular vibrations and their direction can be derived directly from the frequency response sidebands. Examples of sine excitation measurements on a rigid cube are given. Processes of narrow-band random excitation and modal analysis are illustrated with reference to measurements on a freely-suspended beam. The laser beam was scanned by using x-y axis deflection mirrors; if this facility was not available, circular scanning could probably be achieved by using a rotating tilted mirror. Sideband frequency response references were obtained by using multiplied excitation force and mirror-drive signals.

Optical fiber amplifier network having a coherently combined output and high-power laser amplifier containing same

Abstract: An optical fiber amplifier which receives a primary laser beam and generates a coherent amplified laser beam, includes an optical isolator which transmits the primary laser, a 3-dB coupler which receives the primary laser beam, which generates first and second laser beams, which receives first and second amplified laser beams, and which combines the amplified laser beams to thereby produce the coherent amplified laser beam, a phase controller operatively connected in parallel with the 3-dB coupler which controls the phase of each of the amplified laser beams, and first and second fiber amplifiers operatively connected to the 3-dB coupler, the fiber amplifiers receiving first and second laser beams and generating the amplified laser beams, respectively. A high power coherent laser amplifier utilizing several optical fiber amplifier networks connected to one another in parallel is also described.

Method for driving a laser scanner

Abstract: What is disclosed is a method for driving a laser scanner, comprising a beam deflection system for a laser beam emitted by a laser light source, wherein a minimum distance to be observed is determined in dependence on the laser power of the laser light source. During the measurement the detected object distance is compared with this minimum distance, and the laser light source is deactivated and/or the laser power is reduced if the detected object distance is less than the minimum distance. There is moreover disclosed a laser scanner for implementing this method.

Integrated semiconductor diode laser and photodiode structure

Abstract: An integrated semiconductor structure with optically coupled laser diode (11) and photodiode 12A, both devices having etched, vertical facets (16A, 21). The photodiode has a spatially non-uniform sensitivity profile with respect to the incident light beam (18A) emitted by the laser. This is due to the varying distance from the laser facet and/or to variations in the angle of incidence and results in photocurrents produced by the photodiode that depend on the intensity distribution of the light beam. The spatially non-uniform sensitivity profile allows the measurement of the far-field intensity distribution of the laser and thus on-wafer screening of lasers with respect to their mode stability.