Three-dimensional particle size and shape characterisation using structural light

Abstract

Great advance has been witnessed in image-based particle size and shape characterisation methods for reproducing traditional sieve-based size and caliper-based shape measurements. However, discrepancies still existed due to the limitations of image-based methods, which include the difficulty of obtaining the third dimensions from two-dimensional images, the errors caused by the internal textures of particles, and the particle shadows due to non-uniform illumination. This paper presents a simple, effective and inexpensive structural light technique for eliminating these limitations. This technique can determine three principal dimensions of many sand to gravel particles simultaneously and is less affected by particle internal textures and shadows. Eight hundred randomly selected soil particles with a range of sizes, colours, shapes and angularities were investigated using the structural light system to obtain their size and shape distributions. A remarkable agreement was found between the structural light results when compared with sieving analysis and manual measurement of shapes using calipers.