On-line measurement of the real size and shape of crystals in stirred tank crystalliser using non-invasive stereo vision imaging

Non-invasive stereo vision imaging technique was applied to monitoring a cooling crystallisation process in a stirred tank for real-time characterisation of the size and shape of needle-like l-glutamic acid (L-GA) β polymorphic crystals grown from solution. The instrument consists of two cameras arranged in an optimum angle that take 2D images simultaneously and are synchronised with the lighting system. Each 2D image pair is processed and analysed and then used to reconstruct the 3D shape of the crystal. The needle shaped L-GA β form crystal length thus obtained is found to be in good agreement with the result obtained from off-line analysis of crystal samples, and is about three times larger than that estimated using 2D imaging technique. The result demonstrates the advantage of 3D imaging over 2D in measurement of crystal real size and shape.