Patent ID: 8164982

Claim:
An ultrasonic sensor for detecting an object, comprising: a plurality of sensing devices arranged in an array, each of which includes a piezoelectric element and an acoustic matching member having a first surface exposed to space where the object exists and a second surface joined to the piezoelectric element; and a circuit device electrically coupled to the piezoelectric element, wherein one of the plurality of sensing devices is configured as a transmitting device that transmits ultrasonic wave upon reception of a transmission signal outputted from the circuit device, and at least another one the plurality of sensing devices is configured as a receiving device that receives the ultrasonic wave reflected from the object and outputs a received signal corresponding to the received ultrasonic wave to the circuit device, the circuit device includes a drive signal generator that outputs a drive signal to the receiving device based on the transmission signal, and the drive signal causes the piezoelectric element of the receiving device to vibrate such that a vibration signal propagated from the transmitting device to the receiving device is cancelled.