Abstract: In the preferred embodiment of the present invention, a television camera is oriented with respect to a conveyor belt such that the direction of the scanning lines of the television camera are perpendicular to the direction of motion of the conveyor belt. Material containing foreign bodies is introduced on the conveyor belt and passes under the television camera and a light source. The television camera detects the reflected and/or radiant light and produces a video signal in accordance therewith. The image component of the video signal for each of the scanning lines is divided into signal portions. Like signal portions of respective scanning lines are successively integrated in an integration circuit to provide a non-zero signal when a foreign body is detected by the television camera. The output of the integration circuit is applied to a threshold switch, which produces a logical one when the value of the output of the integration circuit is equal to or exceeds an adjustable reference value.