Fraunhofer diffraction pattern analysis

D < 500 pm, Fraunhofer Diffraction Pattern Analysis (FDPA) can be employed in measuring particle size distributions (4,5). For the particles in the intermediate range, 0.7 pm < D < 10 pm, Mie theory of scattering holds and Turbidity Spectra (TS) can furnish information about particle sizes (6). 

Fraunhofer scattering has become a popular optical sizing tool for particles substantially larger than a micrometre in diameter. In this case each particle behaves similarly to a pinhole aperture, and the low angle scattered light is a superposition of Fraunhofer diffraction patterns. This technique is widely used for the analysis of commercial food-based emulsions and sauces. 

Koo, J. H., Particle Size Analysis Using Inte l Transform Techniques on Fraunhofer Diffraction Pattern, D. Sci. Dissertation, George Washington Uni., Washington D. C., 1987. Shifrin, K. S., Perelman, A. Ya., The Determination of the Spectrum of Particles in Dispersed System from Data on Its Transparency, Opt. Spectrosc. (USSR), 1%3, 15, 285-289. 

Micro-cuboids in three-dimensional turbulent flow have been examined using Fraunhofer diffraction [86]. Both dynamic and static three dimensional particle shape features could be obtained and served as a basis for particle shape analysis by pattern recognition. 

Characteristics of the spray are measured by laser diffraction and analyzed with Fraunhofer diffraction equation, so that the optical properties of the spray are not necessary for the analysis. The device is called HELOS by Sympatec with a measuring range from 0.5 to 175 pm at that lens configuration. The analysis of the diffraction patterns of several drops with different size is mathematically complex and done by the Software of Sympatec, WINDOX . Thus a cumulative volume distribution of the spray, or drop size distribution (DSD), is measured. 

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