Bragg-Diffraction Imaging: A Potential Technique for Medical Diagnosis and Material Inspection, Part II
In terms of image degradation, one of the most serious problems encountered in low-frequency Bragg-diffraction imaging is caused by multiple acoustic reflections within the Bragg cell. The effect of these reflections can be reduced by frequency sweeping or by using properly-located acoustic absorbers. This paper discusses experiments in this regard and describes several different types of absorbers for a 3.58 MHz system.
Another source of substantial difficulty at the low frequencies is spherical aberration in the cylindrical converging lens used to form the laser beam. The design of such a lens and its effect on the system resolution are discussed.
KeywordsSpherical Aberration Test Grid Polyethylene Membrane Lucite Plate Acoustical Holography
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- 1.John Landry, Hormozdyar Keyani, and Glen Wade, “Bragg-Diffraction Imaging: A Potential Technique for Medical Diagnosis and Material Inspection,” Acoustical Holography, Vol. IV, ED. Glen Wade, Plenum Press, 1972.Google Scholar
- 2.Soo-Chang Pei, “Elimination of Bragg Image Speckle by Frequency Modulation,” August 1972, unpublished.Google Scholar