Patent ID: 8540640

Claim:
An ultrasonic probe comprising: a Capacitive Micromachined Ultrasonic Transducer (cMUT) chip having a plurality of vibration elements whose electromechanical coupling coefficient or a sensitivity changes depending on a bias voltage, and configured to transmit/receive an ultrasonic wave; an acoustic lens provided on an ultrasonic wave radiation side of said cMUT chip; a backing layer provided on a back side of said cMUT chip, to absorb a propagation of said ultrasonic wave; an electric wiring portion provided from a peripheral portion of said cMUT chip and on a side surface of said backing layer and having a signal pattern connected with an electrode of said cMUT chip arranged thereon; and a housing for containing said cMUT chip, acoustic lens, said backing layer and said electric wiring portion, wherein: a ground layer at ground potential is bonded on the ultrasonic wave radiation side of said cMUT chip; said cMUT chip has a substrate; each of said vibration elements of said cMUT chip has a film body provided on the ultrasonic radiation side of said substrate of said cMUT chip, a lower electrode provided in said film body, and an upper electrode provided on the ultrasonic radiation side of said lower electrode; said substrate of cMUT chip is connected with a ground; AC high frequency voltage transmitting/receiving ultrasonic wave is applied on said upper electrode using ground potential as reference potential; and DC bias voltage for changing electromechanical coupling coefficient or sensitivity of said vibration element is applied on said lower electrode using ground potential as reference potential.