A transducer main body has, on a front end side thereof, an oscillating plane having a bent shape in a side view and corresponding to a larger-diameter curved surface formed at a bend of a laminated part. Over the oscillating plane of the transducer main body, a plurality of piezoelectric oscillators is distributed in a matrix in a bent direction and a width direction. In each oscillator group, a controlling unit switches the piezoelectric oscillators to transmission and reception piezoelectric oscillators by turns in the width direction according to a preset transmission/reception pattern and processes a received signal from the reception piezoelectric oscillator according to an aperture synthesis method.
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