| 摘要 |
PURPOSE:To obtain high sensitivity over a wide band, by multiplex construction alternately inverting orientation polarization of a plurality of curved type conversion elements laminated. CONSTITUTION:The orientation polarization of a plurality of curved type conversion elements 1a...1n is alternately inverted and they are laminated so that each coversion element can be excited independent oscillation mode. The front and back electrodes of each piezoelectric film are connected parallelly for in-phase excitation acoustically and the electric terminals 6, 6' for input and output are provided. The distances 7a...7n-1 of each conversion element are taken sufficiently shorter than the wave length, and thus, the acoustic waves independently radiated from each conversion element are superimposed at the sound reception point sufficiently apart from the transducer. Accordingly, the increase in the output sound pressure proportional to the number of conversion elements to the same input voltage can be obtained. Further, to obtain sufficient effect of superposition, the total thickness 8 laminating each conversion element is suppressed 1/10 or less to the wave length of sound pressure objective. With this counstruction, high sensitivity can be obtained over a wide band from the audible zone to low ultrasonic waves. |
