| 摘要 |
An ultrasonic transducer providing a plurality of different focal lengths within a unitary structure and comprising a piezoelectric element 10 having a curved surface having varying or different radii of curvature with respective sections 10a, l0b, 10c, 10d of the surface providing respective different focal lengths 01,02,03,04. Each section of the curved surface can include electrodes 22 in the form of a Fresnel zone pattern to provide focussing in the orthogonal dimension. |
