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Adjustable Acoustic Knife Edge for Anisotropic and Dark-Field Acoustic Imaging

Research output: Contribution to journalJournal article

Published

Journal publication date01/1994
JournalJapanese Journal of Applied Physics
Journal number1A
Volume33
Number of pages5
Pages329-333
Original languageEnglish

Abstract

A new effective method for acoustic anisotropy and dark-held imaging in reflection ultrasonic focusing devices is proposed. Part of the spherical acoustic wave propagating to and coming from the object is stopped by an ultrasonically opaque acoustic knife edge (AKE) set at the aperture plane of the focusing lens or transducer. This AKE provides the focusing device with directional sensitivity and the capacity for dark-field imaging. Sensitivity of the AKE system to the elastic anisotropy of the leaky surface acoustic wave (LSAW) velocity was demonstrated using an X-cut LiNbO3 crystal. Dark-field imaging of cracks in Si3N4 ceramics and the structure of carbon fiber-reinforced plastic (FRP) was performed. This method can be easily applied to commercially available focusing systems and allows optimization of the setup for the microscopic study of various objects.