LDA Implementation

The fringes are oriented normal to the x-axis, so the intensity of light reflected from a particle moving through the measuring volume will vary with a frequency proportional to the x-component, Ux, of the particle velocity  

If the two laser beams do not intersect at the beam waists but elsewhere in the beams, the wavefronts will be curved rather than plane, and as a result the fringe spacing will not be constant but depend on the position within the intersection volume. As a consequence, the measured Doppler frequency will also depend on the particle position, and as such it will no longer be directly proportional to the particle velocity, hence resulting in a velocity bias. 

2 Measuring Volume. Measurements take place in the intersection between the two incident laser beams, and the measuring volume is defined as the volume within which the modulation depth is higher than e times the peak core value. Due to the Gaussian intensity distribution in the beams, the measuring 

As important are the fringe separation and number of fringes in the measurement volume. These are given by  

Forward scattering LDA is not completely obsolete, however, since in some cases its improved signal-to-noise ratio makes it the only way to obtain measurements at all. Experiments requiring forward scatter might include  

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