Abstract: The image of a body which is located in a measuring zone is projected by a mirror into a camera having an optoelectric transducer, for instance a row of photodiodes. The stripe pattern is thrown onto the upper side of the body by a light beam which is inclined with respect to the projecting direction, said stripe pattern being imaged together with said body. The shape of the body in the vertical projection is detected by the camera and an associated electronic system, and the elevation of the body is deduced from the position of the stripe pattern thereon. Three dimensions, i.e. the actual size of the body, are thus determined. A sorting device can be controlled according to the detected size.