Back-Projection Algorithms for a Computer-Controlled Scanning Laser Acoustic Microscope
In this paper we evaluate the capability of a scanning laser acoustic microscope (SLAM) to produce images of buried flaws or artifacts in objects which support both shear and compressional waves. First we describe a method of imaging near-surface flaws or artifacts by surface wave insonification, and give some experimental results. We then show that a conventional SLAM does not acquire sufficient data for the back-projection imaging in solids. However appropriate spatial filtering of the acquired data can produce acceptable quasi-back-projected images of deeply buried flaws. This is shown analytically and demonstrated with some images obtained with a computer-controlled SLAM developed in our laboratory.
KeywordsCompressional Wave Surface Wave Lithium Niobate Cover Plate Bulk Wave
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