Measurement of Froth-Layer Depth With Binocular Camera Based on Intensity Correction and Its Application to Pulp-Grade Monitoring

In froth flotation, the froth-layer depth is an important indicator for performance monitoring and working-condition recognition. The primary depth-measurement method in a complex industrial process is based on a binocular camera. Much related research has been proposed to obtain accurate object depth. However, since the bubbles in the froth image are convex objects, the top of each bubble has a white spot which makes the texture of each bubble very faint, rendering the existing depth-measurement method inadequate in froth flotation. Therefore, in this article, we propose a method for measuring the froth-layer depth using an intensity correction. First, we use morphological reconstruction (MR) to extract the white spots. Next, we calculate the coefficient map for depth adjustment based on the light reflection characteristics of bubbles and white spots. After that, we implement depth optimization with intensity correction using the semiglobal block matching (SGBM) method to obtain the froth-layer depth. Finally, based on the froth-layer depth, we design a model for pulp-grade monitoring and conduct comparative experiments in froth flotation. The results show that compared with a monocular froth image, the root mean squared error (RMSE) of the proposed method is reduced by 50% and
$R^{2}$
is increased by 44.38%. Compared with the depth map obtained by the SGBM method, the RMSE of the proposed method is reduced by 9.4% and
$R^{2}$
is increased by 13.35%.