A Quantitative Acoustic Microscope with Multiple Detection Modes

Abstract

An acoustic microscope that permits operation with both toneburst and impulse excitation of the lens has been developed. Either mode may be switched-selected and combined with mechanical scanning in any direction. In impulse-excited mode, the specular and Rayleigh signals from the sample are resolved in time, and analysis is performed to obtain surface wave propagation parameters. The power of the simultaneous application of these techniques is illustrated by measurements on specimens of intact and fractured glass and duraluminium. Reflection and transmission coefficients for a crack are measured, and conclusions are drawn about V(z) processing. These results are significant because the images of cracks produced by the conventional toneburst SAM tend to be complex. Previous work has, therefore, centered on crack detection, rather than characterization. Lastly, diffraction from the tips of cracks has been observed in the microscope. © 1989 IEEE