| Popis: |
Since the introduction of the mechanically scanned acoustic microscope by Lemons and Quate,1 a world-wide effort has taken place to make this device2 one of the most widely used tools for materials characterization and development. With the exception of work by Tsai,2,3 and the pulse compression acoustic microscopy by Ni-koonahad, Yue, and Ash2 most studies have utilized acoustic pulses containing many wavelengths, resulting in narrow bandwidth systems. Calculations for material properties therefore require amplitude and phase measurements at different heights of the acoustic transducer above the sample. Algorithms for the use of these V(z) data have become highly sophisticated as reported in the work of Weglein, Kushibiki, Chubachi, Bertoni, Kino, Laing, Kuri-Yakub, Ash, Wickramasinghe, and others.2 This work continues to develop methods for time and frequency domain observations of broadband acoustic pulses. These observations permit material properties to be determined with the acoustic transducer at a constant height above the sample. The necessary data can be acquired during uninterrupted mechanical scanning by digitizing the reflected waveforms from the sample. One of the advantages of this approach is that scanned broadband systems are, and historically have been, widely used for industrial quality control. |
