Detailed study of the Fourier transform of the time-interval photon statistics distribution applied to laser Doppler velocimetry

Abstract

In this paper a technique consisting of measuring the Fourier transform ${Q}_{F}$ of the time-interval photon statistics distribution is studied when applied to laser Doppler velocimetry. It is supposed that a device that changes the Gaussian intensity profile of the laser beam into a uniform intensity profile is used. A theoretical model for a fluid with a constant velocity is obtained and verified by two ways: experimentally and by a computer-simulation method. Then the experimental conditions for which the signal can be approached to a Lorentzian curve and the error involved in the determination of the fluid velocity are studied from the theoretical model. It is concluded that the measurement of ${Q}_{F}$ is a useful technique for very low intensities.