Laser diffraction is a classic means to determine the size distribution of a grouping of multiple particles. Although there are many approaches to backing out the particle size distribution from the diffraction pattern taken on a CCD camera, I have been unable to find software that reads in the diffraction image, processes it, and provides the particle size distribution. Perhaps I am looking in the wrong places, but does anyone know of Windows software that can do this operation and is not tied to a specific commercial instrument?
Stephen Sampayan
What systems (in terms of a rough PSD) and what 'picture' over what angular range do you have on the CCD? The angular capture range will define whether you can get meaningful information from such a deconvolution. Very roughly the angular information in degrees is related to the particle size by 35/d. Thus the scattering pattern for a 10 micron particle is captured over 3.5 degrees (all almost all forward scattering) and a 1 micron particle over 35 degrees. Higher sizes can be a real pain. To capture the scattering from a 3500 micron particle needs angular resolution of 0.01 degrees. Normally a PSD is obtained from the angular intensity pattern rather than an image although the image is typically symmetrical. It is an ill-conditioned problem from to go from light scattering data to PSD result with all that implies.
Thomas Wriedt's site ScattPort contains a number of programs claiming to be able to do this reverse process. Be aware, of course, that the optical properties are required for a Mie evaluation and that Fraunhofer is an approximation assuming total opacity of the particle. You also may want to look at Philip Lieven's excellent MiePlot.
Also remember that polydispersity is the bane of all particle size analyses and techniques.
Can you make an image available to see what you are working with?
I am sorry for the delay in responding. We are actually in the process of designing the experiment still so we have complete liberty to specify the detector optics for the gated camera. The only limitation will be spherical aberration if we get "too greedy" with the field of view. The size particles we will be looking at is approximately 0.1 to 1.0 micron diameter. We are looking at Prof Donnelly's MIE codes at Harvey Mudd in the USA, but it is not a commercially supported product. Also, his detector rotated about a fixed point and a CCD array is of course flat, so we will do a translation of the data prior to processing.
Stephen Sampayan
Thanks for the clarification.
At these sizes (0.1 - 1 um) then you're in the region of strong oscillatory behavior tending to isotropic (Rayleigh) scattering at the lower size you mention. Here non-intuitive phenomena can occur such as the scattering intensity falling with increasing size. This is only modeled with Mie theory and thus you'll need the optical properties of your particles. The Fraunhofer approximation just won't cut the mustard here - both size (x) and quantity (Q3) will be in error. At these sizes there are no free, discrete, independent particles of much less than 0.5 microns in a powder so I'd be interested in what (weak) scattering you'll be trying to see. Aerosols, atomized material?
Bohren and Huffman's book does give a Mie program in the back but this is size to scattering prediction - not the reverse. These webinars (registration required) may be of interest:
Know the Basics of Dispersing Nanosize Materials
https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W190528DispNanoMat
The life of Gustav Mie and the development of the Lorenz-Mie solution to Maxwell's equations
https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W140225Gustav-mie-maxwell.html
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