Time-Resolved Acoustic Microscopy of Polymer Coatings

Abstract

As an alternative to the standard gated CW (toneburst) mode for the scanning acoustic microscope, the lens may be excited by short impulses instead of gated bursts of CW [e.g. Yamanaka 1983]. The short temporal extent of the impulse excitation allows separate echo pulses from the top and bottom of a thin specimen on a slide, or from separate interfaces in a layered specimen, to be identified in the received signal (see Fig. 1). The scanning acoustic microscope at Oxford University (here called the OXSAM) has been used in this time-resolving mode to measure the elastic properties of soft and hard biological tissues on a microscopic scale [Daft and Briggs 1988a, 1988b, Daft et al. 1988] and to characterise surface acoustic waves and surface-breaking cracks in other hard materials [Weaver et al. 1988].