8. Ultrasonic Imaging and Microscope
A reconstruction of the ultrasonic scattered fields in the zone near the scatter constitutes an image of the scatterer or flaw. In a real case the reconstruction zone may contain more than one distinct scatterer and accordingly the entire group form the image. At a remote location the scattered fields form a complicated diffraction pattern which will yield the image if operated on by a suitable set of mathematical operations. The measurement of the remote fields is of major interest as it affects the image quality. Unlike phased array systems, the transducer spacing, hence measurement sampling density, is determined by the spatial frequencies of the diffraction pattern and sampling theory. This paper will describe the implementation of a 64 x 64 2D array and the results obtained in imaging the phase and magnitude of source and scattered fields.
Lakin, Ken M., "Acoustic Imaging by Wavefront Reconstruction" (1981). Proceedings of the DARPA/AFWAL Review of Progress in Quantitative NDE, October 1979–January 1981. 30.