Development of a New Velocity Measurement Technique: The Laser Bessel Velocimetry (original) (raw)
The present thesis describes the design, construction and testing of a new velocity measurement optical technique system. The technique has similarities with the laser Doppler velocimetry (LDV) in that it uses scattered light detection, in order to measure one component of the velocity vector of moving flows or solid surfaces. It uses the fringes of a Bessel beam produced by an axicon to generate the measurement volume. This technique, which we call Laser Bessel velocimetry (LBV), is noninvasive and permits continuous velocity measurements of moving particles. The experimental measurement set-up including the laser source, the optical devices, a moving stage with known velocities, a photodetector to capture scattered light and signal processing and data acquisition components, was developed and used to provide a proof of concept of this new technique. The set-up was also tested with a commercial LDV system. Two types of refractive linear axicons have been used to generate a Bessel t...
Related papers
Laser Doppler velocity measurement system
2010
Laser Doppler Velocimetry technique (LDV) isa measuring technique which has been developed since early 1980s. LDV has many advantages such as non-invasive measurement of one or all three components of velocity vector, measured dimensional vector of velocity, high accuracy, high resolution, wide measurement range ... Commercial Equipment based on LDV principle was applied to measure flow in industrial applications, in biomedical applications, etc. ... However, most of them are the specialized equipment which have high cost. In terms of technical training and education, LDV experiment is one of the basic experiments of application in high-tech optical measuring techniques, showing the skills of application of the principle of optical measurement applications in practical conditions. A model LDV system was designed and complete development within the lab for training purposes.
Measuring velocity with Bessel beam fringes
Optical Engineering, 2015
We analyze theoretically, numerically, and experimentally the spectral response of scattered light intensity from moving particles crossing the fringes of a Bessel beam. This response could be the basis of a simple technique to measure velocity. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.
Imaging laser Doppler velocimetry
Experiments in Fluids, 2011
Imaging Laser Doppler Velocimetry (ILDV) is a flow measurement technique which facilitates the measurement of the velocity in an imaging plane. It is an evolution of Heterodyne Doppler Global Velocimetry and may be regarded as the planar extension of the classical dual beam LDV by crossing light sheets instead of focused laser beams in the flow. Seeding particles within the flow are illuminated from two different directions. The light scattered from the moving particles exhibits a frequency shift due to the Doppler effect. The frequency shift depends on the direction of the illumination and the velocity of the particle. The superposition of the two different frequency shifted signals creates interference on the detector and leads to an amplitude modulated signal wherein the modulation frequency depends on the velocity of the particle. This signal is detected using a smart pixel imaging array with a resolution of 144 x 90 pixels. The detector performs a quadrature detection on each pixel with a maximum demodulation frequency of 250kHz. To demonstrate the feasibility of the technique two experiments are presented: The first experiment compares the measured velocity distribution of a free jet using ILDV with a reference measurement using PIV. The second experiment shows an advanced setup using two smart pixel detector arrays to measure the velocity distribution on a rotating disk, demonstrating the further potential of the technique for high velocity flow measurements.
Laser Doppler Velocimetry with a Compact Disc Pickup
Applied Optics, 1998
A laser Doppler velocimeter employing a compact disc pickup for both fringe projection and signal detection is described. The spectrum of the recorded signal gives the information about the speed of the object. The device takes advantage of the Talbot effect to project the grating contained in the pickup onto a moving target, so that no imaging system is required. The peculiar imaging technique allows for the exploitation of several optical configurations and permits the manipulation of the intensity profile of the projected grating. The instrument was used to measure the velocity of dust particles on a solid substrate in the 1-m͞s range but could also find an application to the study of liquid flow.
Solid state and fibre optic laser doppler velocimeters
Optics and Lasers in Engineering, 1984
Laser Doppler velocimetry (LDV) has become established as an important technique for the measurement of velocities of macroscopic objects and fluids: the dynamic range is large (-10p6-lo5 ms-') and
Two optical methods for simultaneous measurement of particle size, velocity, and refractive index
Applied Optics, 1991
Two optical methods that were developed for recognizing the composition of moving spherical particles as well as measuring their sizes and velocities are described here. Both methods are meant for characterizing single particles with a high spatial and temporal resolution. One method is an extension of the phase-Doppler technique, whereas the other is a newly developed method that utilizes cylindrical waves of laser light to illuminate the particles. The principles of both methods are described, and some experimental data are presented to demonstrate the feasibility of the theoretical concepts.
Speed measurement of a rotating diffuser by means of the Doppler shift of the scattered light
An experiment designed to detect the Doppler shift frequency of light scattered by a moving diffuser when the speed of the scatters has a component in the line of sight direction is described. The device proposed is similar to a Michelson interferometer, in which the mirrors have been replaced by two diffuse surfaces, one of them moving with constant angular speed, while the other remaining at rest. The coherent superposition of the light dispersed in both surfaces results in a dynamic speckle pattern, whose intensity fluctuation contains the beat frequency between the component frequencies. The intensity fluctuations are recorded by means of a photodetector which signal is digitized with a sound interface of a PC multimedia system. The spectral distribution of the signals shows peaks centered in the corresponding beating frequency of the light dispersed by the moving diffuser. These frequencies are correlated with the tangential speed of the diffuser at several distances from the axis of rotation.
Loading Preview
Sorry, preview is currently unavailable. You can download the paper by clicking the button above.