In-situ Measurement of Crystal Length and Width Based on Binocular Vision with Oriented Object Detection

For real-time monitoring of the growth quality of crystals during a crystallization process, this paper proposes an in-situ measurement method of crystal length and width based on the oriented object detection by a binocular vision system. The oriented object detection is used to divide the overlapped crystals into individual crystals for measurement, respectively, so as to improve the measurement accuracy on crystal size distribution (CSD). By establishing an imaging model of the binocular telecentric cameras, the coordinates of four key contour points representing the crystal length and width in three-dimensional (3D) space are precisely calculated, such that the length and width of each crystal could be reconstructed for measurement, avoiding the projection error from two-dimensional (2D) plane measurement. Experimental verification on measuring the cooling crystallization process of -form L-glutamic acid (LGA) is shown to demonstrate the effectiveness and advantage of the proposed method.