PURPOSE: To obtain a probe which makes the effective sound field constant independently of frequency, by making a transmittable or receivable ultrasonic frequency in the side of the aperture end lower than that in the side of the center of the aperture face.
CONSTITUTION: A piezoelectric element 2 consists of a disc-shaped element, which is provided in the center, and a torus-shaped element which is provided around this disc-shaped element in a shape like a concentric ring, and the whole of a transducer is formed so as to have a concave in the center for the purpose of forming a focus. A disc-shaped electrode 6 and a ring-shaped electrode 7 are formed on the back of the disc-shaped piezoelectric element in the center, and an earth electrode 5 is formed on all of the surface of this element. Ring-shaped electrodes 8W13 arranged on concentric circles are formed on the back of the ring-shaped piezoelectric element, and the earth electrode 5 is formed on all of the surface of this element. A back absorbing layer 4 is provided on the back of the whole of the transducer. The thickness of the piezoelectric element or a matching layer 3 is adjusted for every element to make the shape of the long- distance transmission sound field constant throughout a desired frequency band.
MIWA HIROHIDE
HAYASHI OSAMU
SHIMURA NOBUSHIRO
FUJITSU LTD