Two-dimensional inverse born approximation in ultrasonic flaw characterization

Abstract

A method is developed to characterize flaws of arbitrary shape by using ultrasound pulse echoes at multiple coplanar incident directions. The three-dimensional image reconstruction problem is reduced to a series of two-dimensional image reconstructions, thereby avoiding the difficulties associated with three-dimensional image reconstructions, such as taking and processing a large amount of data, and the complications associated with three-dimensional image reconstructions, such as three-dimensional interpolation, long computing time, etc. The reconstructed two-dimensional images represent the two-dimensional projections or shadows of the three-dimensional flaw characteristic function. Each projection image is reconstructed independently using well-developed computerized tomography reconstruction techniques. If the shape of the flaw is not too irregular, or if the fine details of the shape are not of interest, only a few of these projection images suffice to characterize the flaw. The magnitude scaling problem and the alignment problem of the echoes at different incident directions can be handled easily in the algorithm. Simulation studies yielded encouraging results.