BSA Flow Software Installation and User's Guide - CSI

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Φ V1-V2
Φ U1-U2
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Validation The validation routine consists basically of comparing the droplet
routine diameter measured by the planar PDA with the droplet diameter measured
by the conventional PDA. A programmable discrepancy is allowed to
account for the finite accuracy of the phase measurement in the signal
processor and for a certain degree of non-sphericity of the droplets. The size
measurement is finally performed using the phase difference measured with
the conventional PDA due to the higher resolution. The planar PDA is used
to resolve the 2π ambiguity and for validation. As both PDA configurations
are affected in a different sense by the trajectory effect and the slit effect,
this validation procedure provides an effective means to identify and reject
erroneous measurements.
7.2.3 Light scattering from small particles
General considerations on scattering
Light scattering Most of the material presented in this appendix is based on geometric optics
theories (ray tracing). The approach using geometric optics (GO) is valid for
particles of diameter much larger than the wavelength of light and at a
distance much greater than the diameter of the particle. For smaller
particles, it is necessary to apply the Lorenz-Mie Theory (LMT) for light
scattering and if the Gaussian intensity distribution of the laser beams is also
to be taken into account, the Generalized Lorenz-Mie Theory (GLMT) can
be used. Such is the case when the trajectory effect, which arises from the
Gaussian beam profile, is to be analysed.
Basic relations for light hitting an interface
Figure 7-29: Typical DualPDA phase-diameter relationship.
A ray of light hitting an interface between two regions of different refractive
index, n 1 and n 2 (Figure 7-31), is examined.
7-34 BSA Flow Software: Reference guide
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Figure 7-30: The different slopes of the diameter-phase relation in the DualPDA,
used to resolve the 2π ambiguity.