Direct estimation of sieve size distributions from 2-D image analysis of sand particles

Optical image analysis offers several advantages over sieve size distributions in terms of productivity, exactness and automation. In this paper, the authors demonstrate how perfect correlation with sieve size distributions can be achieved for particles in the range between 50 µm and 2 mm when controlling the position and running velocity of particles in front of the video camera and when adopting adequate size measurement algorithms. Results are shown for sands provided by the European Bureau for Certified Reference together with statistical data for sieve size distributions from five reference labs. Image analysis results without any prior calibration fit perfectly within the dispersion of the five sieve size distributions. The unique underlying hypothesis for perfect correlation is a uniform density as well as a reasonably similar flatness index throughout the size range.