Spectral correlation filters for flaw detection

A filtering approach is presented that exploits structural differences between the grain and flaw echo through spectral correlation. Analytical and simulation results demonstrate that back-scattered energy from many randomly distributed scatterers within a resolution cell results in no spectral correlation, while back-scattered energy from resolution cells with only a few scatterers exhibits significant spectral correlation. Performance differences between simple spectral correlation filters and conventional spectral filters are discussed for simple and complex (more than one effective scattering center) defects.