Abstract: A piezoelectric vibration transducer is disclosed which includes a polymeric piezoelectric film as the active element. The film is a selectively or fully polarized, uniaxially oriented material selected from the group of polyvinylidene fluoride, blended material such as polyvinylidene fluoride and PZT powder, polyvinyl fluoride, polyacrylonitrile, copolymers or vinylidene fluoride such as vinylidene fluoride and tetrafluoroethylene or trifluoroethylene. The film is bonded to electrode strips formed by printed circuit methods and then overcoated with a front electrode layer. The sandwich formed by the electrode layers and intermediate polymeric piezoelectric film can be reversed so that the front electrode layer is discontinuous while the back electrode layer is continuous, or both electrode layers can be formed to be discontinuous. Special configurations for the discontinuous pattern of electrode layers can be employed such as that specified by Fresnel's theory.

Abstract: An ultrasonic transducer element includes a polymer piezoelectric film having a plurality of sections. The sections are defined by wave planes of ultrasonic waves having substantially .lambda./2 phase difference emanated from an imaginary focal point or line located in front of the piezoelectric film. .lambda. is the wave length of the ultrasonic waves within an acoustic transmission medium located between the piezoelectric film and the imaginary focal point or line. The sections are arranged so that ultrasonic waves emanated from adjacent sections have substantially no phase difference at the imaginary focal point or line. Front and rear electrodes are deposited on opposite surfaces of the piezoelectric film.

Abstract: Electro-acoustic transducer element having its resonant frequency in a lower frequency range advantageously usable for diagnostic purposes comprises a polymeric piezoelectric film such as polyvinylidene fluoride film being coupled with an additional layer having a thickness specified in relation to the wavelength of sound waves within the additional layer at the free resonant frequency of the polymeric piezoelectric film, the additional layer having an acoustic impedance related to the acoustic impedance of the polymeric piezoelectric film.

Abstract: Ultrasonic transducer advantageously usable for diagnostic purpose includes a piezoelectric element such as a PVDF film backed with a reflective layer of a reduced thickness specified in relation to the wavelength of sound waves within the reflective layer at one-half of the free resonant frequency of the piezoelectric element. Remarkable reduction in thickness assures high transfer efficiency, broad available frequency-band and easy application of fine treatments such as etching.