| 摘要 |
PROBLEM TO BE SOLVED: To provide an improved ultrasonic search unit improved in resolving power by forming a beam with a fine width thereof and a longer focusing range to restrict the drop in the sensitivity at a far distance. SOLUTION: In the ultrasonic search unit in which at least an effective/virtual annular sound source part is formed in front thereof or at the back thereof, the sound source part is provided with a plane-shaped or curved surface-shaped piezoelectric element. Moreover, a plurality of lens faces each with a radius of curvature R is arranged on the surface of a lens making up the side of the emitting end of ultrasonic waves radiated from the piezoelectric element. The relationship of 2<R/r<4 is established between the radius of curvature R and the distance (r) to the center, at which the curved surface of the lens face is formed, from the center axis of the lens. COPYRIGHT: (C)2004,JPO
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