A comprehensive shape analysis pipeline for stereoscopic measurements of particulate populations in suspension

A state-of-the-art, compact optomechanical setup coupled with an image analysis routine to measure multi-dimensional particle size and shape distributions (nD PSSDs) for crystallization processes is presented. A novel image processing pipeline to process the raw images from the cameras is presented. The pipeline consists of a stereoscopic camera calibration model, adaptive background subtraction, particle contour matching, and 3D reconstruction of the segmented crystals. The reconstructed crystals are subjected to a supervised shape classification strategy, which categorizes each detected crystal into spheres, needles, quasi-equant particles, platelets and non-convex particles. Additionally, a high-speed image capture mode, capable of monitoring processes with fast kinetics, is presented. The device discussed in this work is subjected to an experimental campaign, to validate size measurements, characterize steady state, and confirm repeatability of measurements to affirm and assess the non-invasive nature of the setup on the measurement. An experiment aimed at evaluating the enhancement in the proposed image analysis pipeline performance, more specifically the automatic shape classification, is further conducted. Finally, a dissolution process is monitored using a stereoscopic imaging setup for the first time, and the size and shape evolution of the population in a growth and dissolution phase is monitored for about 18h.