Development of a stereo imaging system for three-dimensional shape measurement of crystals

Despite the availability of various Process Analytical Technologies (PAT) for measuring other particle properties, their inherit limitations for the measurement of crystal shape have been restricted. This has impacted, in turn, on the development and implementation of optimisation, monitoring and control of crystal shape and size distributions within particle formulation and processing systems In recent years, imaging systems have shown to be a very promising PAT technique for the measurement of crystal growth, but still essentially limited as a technique only to provide two-dimensional information. The idea of using two synchronized cameras to obtain 3D crystal shape was mentioned previously (Chem Eng Sci 63(5) 1171-1184, 2008) but no quantitative results were reported. In this paper, a methodology which can directly image the full three-dimensional shape of crystals has been developed. It is based on the mathematical principle that if the two-dimensional images of an object are obtained from two different angles, the full three-dimensional crystal shape can be reconstructed. A proof of concept study has been carried out to demonstrate the potentials in using the system for the three-dimensional measurement of crystals.