Improved ultrasonic B-scans using deconvolution and morphological filters

Resolution of ultrasonic B-scans for NDE is limited by the bandwidth of the transducer and the presence of noise. An improvement in signal-to-noise ratio (SNR) can be obtained, to some extent, by performing ensemble averaging of numerous measurements. This method is impractical and can not eliminate interfering echoes resulting from stationary scatterers. Contrary to averaging, morphological filters, a class of nonlinear filters, are capable of eliminating impulse noise, moderately reducing grain echoes and improving the overall image quality while selectively preserving certain image features. The authors have applied deconvolution and morphological filters in tandem (i.e., deconvolution before or after morphological operations) in order to improve resolution and SNR. In particular, the performance of these algorithms and the design of the deconvolution kernel and structuring element as well as morphological filters are evaluated using experimental results