| 摘要 |
PURPOSE:To decrease the lowering it the sensitivity and to widen the dynamic range by using a material such as rubber mixed with microbaloon and metallic powder or insulation powder for a back load member of a piezoelectric vibrator. CONSTITUTION:The back load agent 2 is provided to the lower face of plural piezoelectric vibrators 1 via an electrode by flowing or bonding. Since layer or poly layer of acoustic matching layers 3, 4 are provided to the upper face of the vibrators 1 via the electrode and a packing member 5 is provided to the gap of the vibrators 1. An acoustic lens 6 is provided on the acoustic matching layer 4. In applying an electric signal to the electrode of the vibrators 1, an ultrasonic wave 7 is irradiated from the lens 6. The loading agent 2 is formed by a rubber member such as silicon rubber as major component mixed with metallic powder or insulation powder such as tungsten and plastic micro baloon through mixing or curing. Thus, the acoustic impedance of the load agent 2 is low and the sound wave attanuation coefficient is high, then the attanuation of the ultrasonic wave toward the irradiating direction 7 is less.
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