PROCESS FOR THE OPTICAL SORTING OF BULK MATERIAL

The invention relates to a process for the optical sorting of bulk material in a colour-sorting machine while it is conveyed over a transport belt and moves past an observation head with a light source and a product signal receiver arranged in the vicinity of the light source, whereby the reflected light of the image points of the examination material is broken down into several spectral ranges by various colour filters of detection elements lying next to one another of a line of the receiver and the examination material is sorted on the basis of the colour values (measured value of the intensity in the colour in question). According to the invention, it is provided in order to improve the detection rate that, in the case of examination material mixed with reject parts, in each case the colour values of the product are studied in several selected sub-ranges, while, in every sub-range, a classifier ascertains connected areas of image points with colour values falling into the pertinent sub-range and carries out a classification according to preset criteria from the geometry and the size of these detection areas.