An Ultrasonic Imaging System for Three-Dimensional High-Resolution Defect Imaging
Quantitative ultrasonic imaging requires algorithmic data processing to yield the object function of a penetrable scatterer or the singular function of a perfectly scattering geometry, respectively. If either broadband pulse-echo or pitch-catch data are available on a closed measurement surface surrounding the scatterer completely, it can be shown that diffraction tomographic data processing in the widest sense is a solution of the linearized inverse scattering problem, i.e., if either the Born or Kirchhoff approximation can be tolerated in the NDE application under concern[1,2]. A particular representative of diffraction tomography called FT-SAFT for Fourier Transform Synthetic Aperture Focusing Technique has been implemented on an array processor for 3D defect imaging utilizing complementary Golay sequences as transmitted signals to improve the signal-to-noise ratio and therefore, via deconvolution, the axial resolution. Data acquisition, storage, processing and sophisticated graphics display is controlled by an IBM-PC. In  the system as well as its theoretical background is described in detail, hence, only a brief and qualitative account is given here.
KeywordsInverse Scattering Array Processor Diffraction Tomography Singular Function Equivalent Source
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