Elimination of Spurious Detail in Acoustic Images
Many methods of acoustic imaging employ monophonic (single frequency) and strongly directional (spatially coherent) insonification of the object to be examined. Depending on the nature of the object, such methods frequently suffer from the presence of highly objectionable spurious image detail. Typically this detail consists of complex patterns of high contrast which are unrelated to the actual physical structure of the object in the plane under observation. The spurious patterns are due partly to near field-detail in the sound emanating from the transducer and partly to interference effects caused by out-of-focus structures in the object (Talbot images)1, 2 as well as multiple reflections from interfaces.
KeywordsModulation Transfer Function Frequency Sweep Multiple Reflection Acoustic Image Heuristic Reasoning
Unable to display preview. Download preview PDF.
- 1.A. W. Lohmann and D. E. Selva “A Talbot Interferometer with Circular Gratings”, Optics Communications Vol. 4, No. 5, January 1972.Google Scholar
- 2.F. Talbot, Phil. Mag. 9 (1836) 401.Google Scholar
- 3.J. W. Goodman “Introduction to Fourier Optics” McGraw-Hill, New York, N. Y. 1968, Ch. 6.Google Scholar
- 4.R. L. Whitman, M. Ahmed and A. Korpel “A Progress Report on the Laser Scanned Acoustic Camera” in Acoustic Holography, Vol. 4, ed. G. Wade, pp. 11–33, Springer Science+Business Media New York, N. Y. , 1973.Google Scholar