Zone sensing apparatus

摘要

The disclosed apparatus determines optically whether an object is located within a first range of distances from the apparatus or a second range of distances from the apparatus. A radiation projecting arrangement projects a beam towards the object and a receiving arrangement disposed a predetermined distance transverse to the object direction receives the radiation reflected from the object. A pair of radiation sensors in the receiving arrangement each produce an electrical output corresponding to the received radiation. A circuit responds to the outputs of the sensors to determine whether the object is located within a first range or a second range. The circuit arrangement connects the radiation sensors so as to subtract their outputs, and one of the sensors is provided with a more extensive radiation receiving area than the other. This extends one of the range of distances.