In Situ Measurement of 2-D Crystal Size Distribution During Cooling Crystallization Process via a Binocular Telecentric Imaging System

In this article, a novel in situ measurement method with stereoscopic image analysis is proposed for monitoring crystal length and width distributions during a cooling crystallization process based on a binocular telecentric imaging system. First, a stereoscopic imaging calibration model is established for using binocular telecentric cameras to conduct in situ measurement during a cooling crystallization process. Second, an enhanced algorithm is presented to improve matching crystal images from binocular image pairs based on in situ image preprocessing and segmentation. Third, four key corners related to crystal length and width are determined by using the boundary features of matched crystal image projections. Finally, the length and width of each crystal are computed based on the reconstructed key corners in a 3-D coordinate space by using the established stereoscopic calibration model. Experimental validation on the proposed stereoscopic imaging calibration model and 3-D reconstruction of key corners is carried out via in situ measurement of a microscale checker-board plate inserted into a cooling crystallizer. In situ measurements of crystal length and width distributions during the cooling crystallization process of beta-form L-glutamic acid (LGA) are conducted to verify the effectiveness and advantage of the proposed measurement method.

Automated summary

In this article, a novel in situ measurement method with stereoscopic image analysis is proposed to monitor crystal length and width distributions during a cooling crystallization process. The method includes establishing a stereoscopic imaging calibration model, improving crystal image matching using an enhanced algorithm, determining key corners related to crystal dimensions, and computing crystal length and width based on reconstructed key corners in a 3-D coordinate space. Experimental validation on a microscale checker-board plate and betta-form L-glutamic acid (LGA) crystals is conducted to verify the effectiveness and advantage of the proposed measurement method.