Novel approach in scanning acoustic microscopy-the resonance mode

A novel Virtual Cavity Scanning Acoustic Microscope (VSAM), in which a resonating Fabry-Perot acoustic cavity is formed by a PZT plate mirror and an acoustic lens, has been studied and demonstrated. Investigation of the enhancement of nonlinear interactions created by small spheres in an air gap bubble shape in the acoustic resonance cavity are discussed. This novel approach offers greater image accuracy, higher resolution capabilities and better selectivity than a conventional SAM due to the significant increase in the dynamic range of the acoustic signals. Typical applications of VSAM are for surface and subsurface Non Destructive Evaluations (NDE) imaging, especially for imaging bonds, voids and dis-continous regions like air gaps between any two solids. Dis-continous bonds or voids yield strong reflections, leading to high contrast acoustic images to reveal the mechanical properties of these bonded or disbonded regions.