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 article, the authors report line width measurements of a quantum cascade distributed feedback laser by a heterodyne experiment and show that at currents slightly above threshold and a laser output power higher than 1 mW, the full width at half maximum of the beat signal was narrower than 0.5 MHz.
27 citations
Patent•
25 May 2004TL;DR: A laser annealing system and apparatus as discussed by the authors includes a laser light source, which emits a laser beam through an a-Si layer on a substrate, an optical unit which forms an optical path along which the laser beam is transmitted through a subject to be annealed, and a first reflecting component, which reflects the laser beacon that has been transmitted through the subject, to irradiate the subject.
Abstract: A laser annealing system and apparatus, which includes a laser light source, which emits a laser beam through an a-Si layer on a substrate, an optical unit which forms an optical path along which the laser beam is transmitted through a subject to be annealed, and a first reflecting component, which reflects the laser beam that has been transmitted through the subject so that a direction of the laser beam is reversed along the optical path along which the laser beam is transmitted through the subject, to irradiate the subject. Since an operation in which energy is absorbed is repeated plural times when the laser beam is transmitted through the a-Si layer, input energy of the laser beam can be utilized without waste.
27 citations
01 Jun 1983-Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology
TL;DR: In this article, the authors used laser-Doppler vibrometry (LDV) to measure the velocity of different points on the ant's body during stridulation to determine what sorts of body vibration are produced by the impact of the scraper on the file, both in air and with mass-loading of the cuticle underwater.
Abstract: 1.
The leaf cutting antAtta sexdens stridulates using a file-and-scraper device (Markl 1968). The temporal and spectral characteristics of the cuticular vibration and airborne sound are fairly typical of the stridulatory sounds of insects that lack specialized radiating structures (Masters 1980). We used laser-Doppler vibrometry (LDV) to measure the velocity of different points on the ant's body during stridulation to determine what sorts of body vibration are produced by the impact of the scraper on the file, both in air and with mass-loading of the cuticle underwater, and how the vibration relates to this radiated sound.
2.
The gaster, on which the file is located, appears to be the principal sound-radiating part of the ant. From theoretical considerations, we would expect four types of gaster vibration to be excited by the scraper impact: (I) dipole swinging of the entire gaster, (II) quadrupole distortion of the gaster shape due to volume flow of the gaster contents, (III) monopole pulsation of the gaster and (IV) bending waves travelling in the gaster shell. Each type of vibration has associated modal resonances whose frequencies are predicted in a semi-quantitative fashion from a simple mechanical model of the gaster.
3.
Vibrometer measurement shows that each tooth strike typically excites low frequency (∼1 kHz) and high frequency (∼10 kHz) damped vibrations that can be detected at most points on the gaster. Broadband spectral energy can be detected up to about 30 to 40 kHz (in rare cases to ∼60 kHz). The low frequency resonance appears to be due to type I rather than type II vibration, and the high frequency resonance due to type III rather than type IV vibration.
4.
Underwater, both low and high frequency resonances were still present, but their frequencies were reduced by about 15% and 35% respectively. We expect the decrease to be even greater when the ant is buried underground.
5.
The rate at which the scraper strikes the teeth of the file is close to the ∼1 kHz modal frequency of the gaster, but in contrast to our expectation does not exactly match this frequency (Fig. 2). The reason for this discrepancy is not clear.
6.
Below about 30 kHz there is fairly good correspondence between the energy spectra of the airborne sound recorded with a microphone and the gaster vibration recorded by LDV. Above this frequency the sound usually shows a complicated power spectrum that we can relate to the vibration of the body only in a qualitative fashion.
27 citations
01 Mar 1999
TL;DR: In this article, the authors extended continuous-scanning laser Doppler vibrometer (LDV) test techniques for impact testing to be applicable to impact testing, where the modal constants can be processed to give, depending on the type of scan, mode shapes, or angular vibration, or translational components of vibration at a point.
Abstract: Previous-described continuous-scanning laser Doppler vibrometer (LDV) test techniques involved, generally, sinusoidal testing of structures. They are here extended to be applicable to impact testing. In an impact test a scanning LDV's response has peaks in the frequency domain, spaced at multiples of the scan frequency, on both sides of each natural frequency, to which standard modal analysis can be applied. The resulting modal constants can be processed to give, depending on the type of scan, mode shapes, or angular vibration, or (three) translational components of vibration at a point. The methods appears to be comparable with normal impact testing in speed and effectiveness - and have considerable advantages in modal testing.
27 citations