Ultrasonic sensor having vibrator mounted on substrate

Abstract

An ultrasonic sensor composed of a substrate and a piezoelectric vibrator mounted on the substrate is advantageously used as a sensor for detecting a distance to an object located in front of an automotive vehicle. Ultrasonic waves transmitted from the sensor are reflected by the object, and the reflected waves are received by the sensor. Based on the reflected waves, the distance from the vehicle to the object is calculated. To reduce rigidity and thereby to lower a resonant frequency of the substrate to a desirable level, grooves are formed in the substrate. A thickness of the substrate is not reduced to maintain its mechanical strength against an impact force. A resonant frequency which is desirable to realize a sufficiently high directivity and sensitivity is obtained in this manner without enlarging a size of the ultrasonic sensor.

Dependencies are inferred from the claim text.