| 摘要 |
PROBLEM TO BE SOLVED: To provide a piezoelectric ultrasonic sensor element of which the sensitivity is increased in comparison with the conventional technology and which is hardly influenced by external noise. SOLUTION: The piezoelectric ultrasonic sensor element consists of a piezoelectric sensor which is constituted by holding a ferroelectric body 17 between at least two paris of electrodes, has predetermined resonance frequency, and detects ultrasonic waves. The piezoelectric ultrasonic sensor element is constituted by providing a common electrode 16 provided on one side of the ferroelectric body 17, an internal electrode 18 provided on the other side of the ferroelectric substance and approximately at a center part of the ferroelectric body 17, and an external electrode 19 provided on the other side of the ferrorelectric body 17 and outside of the internal electrode 18. Output voltage is detected between the internal electrode 18 and the external electrode 19 when the ultrasonic waves are detected here. In addition, the external electrode 19 is provided at a position where the sign of output voltage in the internal electrode 18 to the common electrode 16 and the sign of output voltage in the external electrode 19 to the common electrode 16 are different from each other when the ultrasonic waves are detected. COPYRIGHT: (C)2005,JPO&NCIPI
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