Patent ID: 7613073

Claim:
An ultrasonic sensor comprising: a plurality of vibrating parts, each of which vibrates when a corresponding ultrasonic wave, which is reflected by a detection object, is transmitted thereto, and thereby receives the corresponding ultrasonic wave; a plurality of receiving elements, each of which includes corresponding one of the plurality of vibrating parts and detects the detection object based on the corresponding ultrasonic wave; and a waveguide, which holds the plurality of receiving elements and is formed such that the corresponding ultrasonic wave is transmitted through the waveguide to each of the plurality of receiving elements, wherein the waveguide includes: a first opening that faces the detection object, wherein the corresponding ultrasonic wave reflected by the detection object enters through the first opening into the waveguide; a second opening that is not viewable from the first opening, wherein the plurality of receiving elements is held by the second opening of the waveguide such that each of the plurality of vibrating parts is arranged to face a direction in which the each of the plurality of vibrating parts receives the corresponding ultrasonic wave; and a reflecting surface for reflecting the corresponding ultrasonic wave, which enters through the first opening of the waveguide, in a direction to the each of the plurality of vibrating parts, wherein an absorbing member is formed on an inner wall surface of the waveguide except the reflecting surface, the absorbing member comprising a material having a higher absorption coefficient of the corresponding ultrasonic wave than the reflecting surface.