It would be very good to be able to report that acoustical holography, in the few short years since its inception, had reached the point of being a practical and useful technique for the three-dimensional visualization of opaque structures, particularly for the visualization of biological tissue structures for diagnostic purposes. Unfortunately, this is not the case. There remain two primary limitations on the development of such a practical holographic visualization technique. The fundamental limitation remains that of the inability to detect an acoustical energy distribution in a two-dimensional field with sufficient sensitivity for diagnostic use, and a secondary limitation is imposed upon the image presentation procedure because of the image anomalies associated with the great difference in wavelength between the investigating acoustic energy and the reconstructing electromagnetic energy in the visible spectrum. There is, however, reason to be optimistic about the future development and application of holographic imaging using acoustical energy. The reasons for optimism include the very considerable amount of research interest and endeavor on the part of numerous research groups and secondly, the very broad spectrum of acoustical frequencies under investigation for different applications. These frequencies range from subaudible frequencies for geologic application to gigahertz frequencies in limited volumes in solids.
KeywordsHologram Recording Holographic Imaging Data Acquisition Rate Distortion Factor Wavelength Ratio
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