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

Abstract

In this paper, 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. Firstly, a stereoscopic imaging calibration model is established for using binocular telecentric cameras to conduct in-situ measurement during a cooling crystallization process. Secondly, an enhanced algorithm is presented to improve matching crystal images from binocular image pairs, based on in-situ image preprocessing and segmentation. Thirdly, 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 three-dimensional (3D) coordinate space, by using the established stereoscopic calibration model. Experimental validation on the proposed stereoscopic imaging calibration model and 3D reconstruction of key corners is carried out via in-situ measurement of a microscale checkerboard plate inserted into a cooling crystallizer. In-situ measurements of crystal length and width distributions during the cooling crystallization process of β-form L-glutamic acid are conducted to verify the effectiveness and advantage of the proposed measurement method.