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: The laser Doppler spectrometer consists of a laser source, a scattering cell, a photomultiplier, a spectrum analyzer, and electrodes for applying an electric field to measure the scattered light spectrum.
Abstract: The laser Doppler spectrometer consists of a laser source, a scattering cell, a photomultiplier, a spectrum analyzer, and electrodes for applying an electric field. In a suitably applied field, bioparticles or macromolecules in the scattering cell will be forced to move along the electric field lines with a velocity given by the product of the electrophoretic mobility and the field amplitude. This induced motion causes a Doppler shift of the scattered laser light which is detected and measured by the spectrometer. Both the electrophoretic mobility and the diffusion constant can be measured simultaneously by measuring the scattered light spectrum in this way. Several procedures are used to obtain high resolution Doppler spectra. Convective instabilities due to Joule heating are minimized by use of rectangular electrodes with a very narrow gap (200 μ to 1 mm). Gas bubbling is minimized by a platinization of the Pt electrodes and by use of a square wave electric field. Examples of high resolution Doppler spe...
75 citations
01 Jan 1990
TL;DR: In this paper, the beam deflection signal due to an acoustic wave and a thermal wave are both distorted as the excimer laser beam fluence is raised through the ablation threshold.
Abstract: Probe beam deflection is used for identification of the laser fluence threshold for excimer laser photoablation of various materials. The beam deflection signal due to an acoustic wave and a thermal wave are both distorted as the excimer laser beam fluence is raised through the ablation threshold.
75 citations
TL;DR: A laser Doppler velocimeter has been developed that uses two of the colors emitted from an argon-ion laser for the simultaneous measurement of orthogonal velocities.
Abstract: A laser Doppler velocimeter has been developed that uses two of the colors emitted from an argon-ion laser for the simultaneous measurement of orthogonal velocities. Designed for use in a 2.13-m by 3.05-m wind tunnel, it is capable of traversing its focal volume across spatially unstable flows at scan speeds of up to 1.5 m/sec. Its optical layout and principles of operation are discussed, and the data from a typical traversal of a trailing wing-tip vortex are presented.
75 citations
Patent•
04 Oct 2001
TL;DR: In this article, the authors used a digital imaging device such as a detector array that allows independent intensity measurements at each pixel to capture images of laser speckle patterns on any surfaces, such as tissue surfaces.
Abstract: New devices and methods are provided for noninvasive and noncontact real-time measurements of tissue blood velocity. The invention uses a digital imaging device such as a detector array that allows independent intensity measurements at each pixel to capture images of laser speckle patterns on any surfaces, such as tissue surfaces. The laser speckle is generated by illuminating the surface of interest with an expanded beam from a laser source such as a laser diode or a HeNe laser as long as the detector can detect that particular laser radiation. Digitized speckle images are analyzed using new algorithms for tissue optics and blood optics employing multiple scattering analysis and laser Doppler velocimetry analysis. The resultant two-dimensional images can be displayed on a color monitor and superimposed on images of the tissues.
74 citations
TL;DR: In this paper, the classical cantilever Oberst beam is replaced by a double sized free-free beam excited in its center, and the analysis is based on a frequency response function measured between the imposed velocity at the center and an arbitrary point on the beam (measured with a laser vibrometer).
Abstract: The Oberst method is widely used for the measurement of the mechanical properties of viscoelastic or damping materials. The application of this method, as described in the ASTM E756 standard, gives good results as long as the experimental set-up does not interfere with the system under test. The main difficulty is to avoid adding damping and mass to the beam owing to the excitation and response measurement. In this paper, a method is proposed to skirt those problems. The classical cantilever Oberst beam is replaced by a double sized free-free beam excited in its center. The analysis is based on a frequency response function measured between the imposed velocity at the center (measured with an accelerometer) and an arbitrary point on the beam (measured with a laser vibrometer). The composite beam (base beam + material) properties are first extracted from the measurement by an optimization algorithm. Young’s modulus and structural damping coefficient of the material under test can be deduced using classical...
74 citations