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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Patent•
29 Jan 1999
TL;DR: In this article, a laser beam irradiating device with which an object is irradiated with the laser beam is provided with a laser oscillator, homogenizers 7 and 11 which make the intensity distribution of laser beam outputted from the oscillator uniform.
Abstract: PROBLEM TO BE SOLVED: To provide a laser beam irradiating device which is constituted to set the intensity of laser beam irradiating an object to be treated with high accuracy SOLUTION: A laser beam irradiating device with which an object 19 to be treated is irradiated with the laser beam, by controlling the intensity of the laser beam is provided with a laser oscillator 1, homogenizers 7 and 11 which make the intensity distribution of the laser beam outputted from the oscillator 1 uniform, a condenser lens 15 which converges the laser beam shaped through a slit 16 that shapes the laser beam, the intensity of which is made uniform by means of the homogenizers 7 and 11 into the form of a prescribed beam by removing the part of the laser beam and projects the converged shaped laser beam upon the object 19, a detector 23 which detects the intensity of the laser beam passed through the slit 16 and made incident to the detector 23, and a controller 25 which controls the intensity of the laser beam, based on the detecting signal of the detector 23 COPYRIGHT: (C)1999,JPO
22 citations
TL;DR: In this paper, a two-color laser scheme was proposed to enable accurate phase measurement even in the presence of a large Doppler offset between the incoming and outgoing signals, where the beat note between the two lasers provided a built-in frequency reference, while the delay line produced by the travel time of the tracking signal provided a stable self-comparison that measured drift in the frequency reference so that it may be corrected for.
22 citations
TL;DR: A terahertz sensor that measures vibrations behind optically opaque barriers (cardboard, plastic, wool, cotton) is described and demonstrated using interferometric techniques, submicrometer displacements can be resolved as mentioned in this paper.
Abstract: A terahertz sensor that measures vibrations behind optically opaque barriers (cardboard, plastic, wool, cotton) is described and demonstrated Using interferometric techniques, submicrometer displacements can be resolved Measured spectral response agrees with commercial vibrometer
22 citations
TL;DR: In this article, closed-loop control of vortex-induced non-resonant vibration of a flexible square cylinder is experimentally investigated in a wind tunnel at Reynolds numbers, Re, of 2800 and 8000.
Abstract: Closed-loop control of vortex-induced non-resonant vibration of a flexible square cylinder is experimentally investigated in this paper. Piezo-ceramic actuators were embedded inside the cylinder to cause an oscillation of the cylinder surface, which subsequently altered the fluid?structure interaction. Experiments were conducted in a wind tunnel at Reynolds numbers, Re, of 2800 and 8000. Two typical control schemes, i.e.?Y_control and u+Y_control, were deployed using feedback signals from structural vibration Y and combined Y and fluctuating flow velocity u, respectively. The control effects on the structural vibration and flow were assessed using a laser vibrometer, an optical fiber Bragg grating sensor, hot wires and particle image velocimetry. Experimental results show that both vortex shedding from the cylinder and the vortex-induced non-resonant vibration were effectively suppressed. The best control effects were observed with u+Y_control in use; the root mean square values of Y, the structural strain rate ?y along the lift direction and u, i.e.?Yrms, ?y,rms and urms, and the circulation ? dropped at Re = 8000 by 58%, 52%, 53% and 88%, respectively, compared with the unperturbed case. It was found that the control effectively modified the nature of the fluid?structure interaction by changing the in-phase fluid?structure synchronization at all dominant frequencies into anti-phase interaction, accounting for the suppression in both vortex shedding and structural vibration.
22 citations
TL;DR: In this paper, an experimental study has been made to early detect the presence of misalignment in shafting systems, by measuring the temperature of the shaft couplings using a thermal imaging camera.
22 citations