Laser Doppler Velocimeters Research Articles

Analytical evaluation of techniques for use of a laser Doppler velocimeter to measure flow and turbulence*

Results of autocorrelation functions and power spectral densities of laser Doppler velocimeters in the reference-beam-heterodyning and the cross-beam-mixing mode are derived to handle turbulence measurements, Doppler ambiguity, spatial coherence, and effects of particle concentration and detection aperture. A useful definition of signal-to-noise ratio is given for both correlation and spectral analyses. The signal-to-noise calculation provides a direct comparison of the figures of merit between various arrangements of a laser Doppler velocimeter with methods for signal processing to measure optically the flow properties of a fluid under given experimental conditions.

Analysis of optical compensating schemes of laser Doppler velocimeters

Basic forms of the optical systems of laser Doppler velocimeters with supression of the additive noise component in the output signal are investigated by the Jones matrix method. The expressions for the resulting Doppler signal, taking into account the parameters and orientation of phase elements and the receiving polarization analyser, have been obtained and analysed. Experimental results are given.

Coherent detection in laser Doppler velocimeters

The possibility of heterodyning between electromagnetic waves scattered by particles separated in space is explained from a classical point of view and from a quantum mechanical point of view. The last description being carried out using only the Heisenberg uncertainty principle and a rather coarse, but intelligible particle picture of electromagnetic waves.

An analysis of simulators and tracking systems for laser Doppler velocimeters

Analogue and digital techniques are proposed for the simulation of signals arising in laser Doppler velocimeters. Their merits are evaluated.

Reply to Comments on: Analysis of Atmospheric Laser Doppler Velocimeters

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text W. M. Farmer and D. B. Brayton, "Reply to Comments on: Analysis of Atmospheric Laser Doppler Velocimeters," Appl. Opt. 11, 2978-2979 (1972) Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

A unified analysis on laser Doppler velocimeters

Using the theory of optical mixing spectroscopy a unified analysis on various optical arrangements of laser Doppler velocimeter, such as local-oscillator heterodyne differential heterodyne and symmetric heterodyne are given. Their theory of operation, signal-to-noise ratio, spectrum broadening and relative merit are discussed. It is found that the differential heterodyne arrangement is superior to all other arrangements, such as laminar flow or rotating disc, in the measurement of uniform velocity, whilst for turbulent flow measurements the relative merit depends on the particle size, particle concentration, dimension of scattering region, etc.

Errata to: Analysis of Atmospheric Laser Doppler Velocimeters

Errata to: Analysis of Atmospheric Laser Doppler Velocimeters

Noise Analysis for Laser Doppler Velocimeter Systems

Laser Doppler velocimeters provide a noncontact method for the measurement of velocities. These measurements are, in general, corrupted by noise arising in the transmission and reception of the optical carrier. An analysis is presented for the effect of noise on the output of the velocimeter system under conditions of high scattering center concentrations and Steady flows. Principally, the so-called Gaussian beam optical setup is considered where the intensity distribution of the intersecting laser beams at the observation volume (fringe pattern) is Gaussian. Output noise spectral densities, noise power, and signal-signal-to-noise ratios are derived in terms of the input signal (Doppler carrier)-tonoise ratios and bandwidths of the processing systems. Also, threshold levels for input signal-to-noise ratios are determined and the photodetector performance analyzed. Finally, analogies are drawn where the current analysis is applicable to other areas of communication.