Patent ID: 8100013

Claim:
A passage detection apparatus of an object that can detect a passage of an object in a specific space, comprising: a vibration generating source comprising a first piezoelectric/electrostrictive element having a drive electrode and a first reference electrode formed on opposing sides of a first dielectric layer; a sensor unit that is arranged at a position corresponding to the vibration generating source across the specific space, and configured to be capable of generating an output according to the vibration, which propagates through a medium in the specific space, from the vibration generating source the sensor unit comprising: a vibration plate made of a plate-shaped dielectric layer and constitutes an outer wall enclosing the specific space; a first detection electrode formed on the vibration plate; a support plate arranged parallel to the vibration plate with a predetermined gap; and a second detection electrode formed on an inner surface, which faces the vibration plate, of the support plate, and arranged parallel to the first detection electrode; a determination unit that determines the passage of the object in the specific space on the basis of the output from the sensor unit, wherein the determination unit is configured to determine the passage of the object in the specific space on the basis of an electrostatic capacitance between the first detection electrode and the second detection electrode; and a first substrate made of a plate-shaped dielectric layer for supporting the first piezoelectric/electrostrictive element, wherein the specific space is formed by a space between an inner surface of the first substrate and an inner surface of the vibration plate; wherein the first substrate has a plate-shaped thin part and a plate-shaped thick part that is formed at both sides of the thin part and is thicker than the thin part, wherein the first substrate is formed such that an outer surface of the thin part and an outer surface of the thick part are continuous on a same plane, wherein the first piezoelectric/electrostrictive element is attached to the thin part of the first substrate, and wherein the specific space includes a space enclosed by an inner surface of the thin part at the first substrate and a side face of the thick part at the first substrate.