Controlling the ultimate openings residues for a robust delineation of fragmented rocks
Résumé
These last years image analysis has started to be thoroughly used for size distribution quality control in mineral industry. Compared to sifting, it has the advantage of reducing the interference with production, of measuring automatically and on-line, and finally of improving the representativeness. Nevertheless, measurement is confronted to various problems, among which the correct extraction of fragments projected areas (2D), more particularly related to problems of over-segmentation and fusion. Indeed, images taken under natural conditions of lighting and positioning of fragments are very complex and noisy to be properly processed. Usual filtering methods, based on linear and non-linear filters, are not appropriate for this kind of analysis. In this paper, a new filtering method is presented. It is based on a new topographic interpretation of image structures (relative grey levels), and uses residual morphological transformations (ultimate opening residues and its associated function). A control of the ultimate opening construction is carried out with the help of a geometrical criterion applied on fragments shapes. Thus, it is possible to calculate a new and dramatically filtered associated function, giving access to relevant markers for the fragments. Thanks to the evaluation of the method on images affected by various types of noise (fine particles, strong texturation, etc), its robustness and efficiency can be proved. Lastly, the faithful delineation of fragments, carried out thanks to relevant marking, leads to the extraction of correct 2D information, totally usable for size attribution (1D) and volume reconstruction (3D).
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