Particle sizing by spectral analysis on transmission fluctuations

Transmission fluctuation spectrometry (TFS) is a method for particle analysis based on the statistical fluctuations of the transmission signal when the particle system is illuminated by a beam with finite beam diameter. The expectancy of the transmission square (ETS) is obtained as a spectrum when the signal is subjected to a procedure of variable spatial and/or temporal averaging. Both the particle size distribution (PSD) and particle concentration can be retrieved.In this paper, we develop a new method of the spectral analysis on the transmission fluctuations. An analytical expression of the spectrum of the fluctuating transmission through a monolayer is derived and the transmission fluctuation spectrum of a 3-dimensional system is formulated based on the layer model with an assumption of low particle concentration. Theoretical results are proved by simulations and measurements.