Abstract: A system (10) for automatically inspecting a stream of matter (12) for varying composition, comprising an emitting device (16) serving to emit a detection medium, which comprises electromagnetic radiation of a substantially constant intensity, to an irradiated zone (I) of the stream at which the medium penetrates a surface of the matter (12), the irradiated zone (I) extending continuously across substantially the width of the stream, the medium penetrating the surface being varied by the matter (12), a receiving device (32) for receiving the varied medium emanating from the matter (12) at a detection zone (D) substantially separate from the irradiated zone (I), and a detecting device (34) serving to generate detection data in dependence upon the varied medium, the arrangement being such that, in use of the system (10), at least the majority of the varied medium received at the receiving device (32) can be transflected medium.