Patent attributes
An ultrasonic sensor includes: a first vibrator for transmitting an ultrasonic wave; multiple second vibrators for outputting a reception signal of a reflection wave; a casing having a bottom for accommodating the vibrators, an outer surface of the bottom providing a vibrating surface; and multiple tubes for guiding the ultrasonic wave. Each tube has a first opening coupled with an outside of a mobile body. An area of the first opening is smaller than an area of the vibrating surface. A distance between two adjacent first openings is smaller than a distance between two adjacent vibrating surfaces. The length of the tubes is determined to equalize a phase difference of the reflection waves at the first openings is equal to that at the vibrating surfaces.
