Patent ID: 7681451

Claim:
A passage detection apparatus for an object capable of detecting a passage of an object in a specific space, the passage detection apparatus comprising: a transmitting device provided with a vibration generating source; a receiving device that is arranged at the position corresponding to the transmitting device across the specific space and can generate an output according to a vibration, which is transmitted from the transmitting device to propagate through a medium in the specific space, wherein the receiving device comprising a reference electrode set to a predetermined potential and a signal output electrode whose potential varies on the bases of the vibration and of whether the object passes or not; and a shielding member that is formed with a through-hole formed between the transmitting device and the receiving device so as to face a route through which the object passes, and that is arranged so as to be interposed between the transmitting device and the receiving device, wherein the shielding member is set to have the same potential as that of the reference electrode.