| 摘要 |
PROBLEM TO BE SOLVED: To provide an ultrasonic transmitter which is improved in transmission efficiency. SOLUTION: The ultrasonic transmitter has a structure composed of a plurality of piezoelectric vibrators 1 arranged in a one-dimensional manner and an acoustic concave lens 3 stacked up on the vibrators 1, and the thinnest part of the acoustic concave lens is shorter than the wavelength of signals driving the piezoelectric vibrators and having the maximum frequency inside the acoustic concave lens. An acoustic layer 4 has an acoustic impedance intermediate between an acoustic impedance possessed by the acoustic concave lens and an average acoustic impedance possessed by a work as an object of testing, and is half or below as thick as the wavelength of the signals having the maximum frequency. The layer is laminated on the transmission surface of the acoustic concave lens 3. Electrodes 2-1 and 2-2 for driving the piezoelectric vibrators 1 are provided on both the sides of the piezoelectric vibrators 1. Lamb waves can be restrained from occurring in the acoustic concave lens and the piezoelectric vibrators. COPYRIGHT: (C)2005,JPO&NCIPI
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