F4 異方性および暗視野超音波映像法のための調節可能な超音波ナイフエッジ(超音波非破壊評価) F4 Adjustable Acoustic Knife Edge for Anisotropic and Dark Field Acoustic Imaging

A new effective method for the acoustic anisotropy and dark-field study in reflection focusing ultrasonic imaging and measuring systems is proposed. Part of the spherical acoustic wave falling to and coming from the object is stopped by the ultrasonically opaque acoustic knife edge placed at the aperture plane of focusing acoustic lens or spherical transducer, providing acoustic system with sensitivity both to the acoustic wave propagation direction (object anisotropy) and to the wave scattered by the acoustic nonuniformities of the object (dark-field imaging). Results of Surface Acoustic Wave (SAW) anisotropy measurements in X-cut LiNbO_3 crystal and dark-field imaging of inner structure of Carbon Fiber Reinforced Plastic (FRP) are given. This method can be easily applied to any commercially available focusing imaging or measuring system and enables one to achieve optimum conditions needed for the studied object.