Dynamic Image Analysis extended to Fine and Coarse Particles
Joachim List, Ulrich Köhler, Wolfgang Witt · 2011
During the last decade Dynamic Image Analysis has become a widely-used method for particle size and shape analysis. Since its introduction this technique has been extended into various fields of application. A unique combination of a pulsed light source, telecentric imaging and a high-speed mega-pixel camera allows for the simultaneous characterisation of particle size and shape at unrivalled particle numbers. Sophisticated evaluation software in combination with a modern database storing the image data creates results of high statistical relevance. Particles are characterised within cycle times down to below a few seconds per measurement using a family of instruments combining representative sampling as well as dry or wet dispersion. Wet dispersing systems, telecentric illumination and imaging create high contrast images of even highly transparent gel particles in water. Recently a lens module has been developed to lower the minimum particle size for wet dispersion down to 1 µm. Although there are physical restrictions concerning the depth-of-field, high-quality results are obtained by precise particle positioning. Even fine materials like silicon carbide F1200 can now be analysed. Another lens module has been developed to cover the coarse regime requiring even optical demagnification. Mainly dry dispersers are used then to characterise fibres or other significantly elongated particles as well as materials with wide particle size distributions like soil without any loss of statistical relevance.