Acoustic microscopy is an invaluable tool in non-destructive evaluation because of its ability to provide high-resolution images of microscopic structure in small objects. When such a microscope operates in the transmission mode, the micrograph produced is simply a shadowgraph of all the struc-tures encountered by the acoustic wave passing through the object. Because of diffraction and over-lapping, the resultant images are difficult to comprehend, especially in the case of objects of sub-stantial thickness with complex structures. To over-come these problems, we have developed a scanning tomographic acoustic microscope (STAM) which is capable of producing unambiguous high-resolution tomograms. We have described in previously-published work how a scanning laser acoustic micro-scope can be employed to realize STAM. We use an algorithm based on "back-and-forth propagation" to reconstruct tomograms of the various layers to be imaged. When these layers are physically close to one another, we see ambiguities in the reconstructions. In this paper we describe a modified algorithm which removes these ambiguities. With the new algorithm, we can resolve layers that are only two wavelengths apart.