Patent ID: 7707887
Filing Date: 2010-05-04
Classification: G01N

Abstract:
1. A passage detection apparatus of an object that can detect a passage of an object in a specific space, comprising: a vibration generating source; 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; a determination unit that determines the passage of the object in the specific space on the basis of the output from the sensor unit; a first substrate comprised of a plate-shaped dielectric layer, which supports the first piezoelectric/electrostrictive element; and a second substrate comprised of a plate-shaped dielectric layer, which supports the second piezoelectric/electrostrictive element, wherein the vibration generating source is comprised of a first piezoelectric/electrostrictive element that has a drive electrode and a first reference electrode formed at both sides of a first dielectric layer, the sensor unit is comprised of a second piezoelectric/electrostrictive element that has a signal output electrode and a second reference electrode formed at both sides of a second dielectric layer, the specific space is formed by a space between the first substrate and the second substrate, and the first substrate and the second substrate are arranged in such a manner that the distance L between the inner surface of the first substrate and the inner surface of the second substrate satisfies the equation of wherein the wavelength of the vibration propagating through the medium is λ, and n and m are natural numbers; wherein the vibration generating source and the sensor unit are arranged in such a manner that the first reference electrode and the second reference electrode are arranged at the side close to the specific space; wherein the first piezoelectric/electrostrictive element is supported on an inner surface, which is the surface at the side of the specific space, of the first substrate, and the second piezoelectric/electrostrictive element is supported on an inner surface, which is the surface at the side of the specific space, of the second substrate; and wherein the first substrate further comprises 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, the vibration generating source is attached to the thin part of the first substrate, and 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.