Circular Scanning Using Four Transducers

Four transducers were used to scan an aluminum cylinder which had three holes drilled in it to simulate defects. Using the transducers as transmitter-receiver pairs, four rf waveforms were collected at each scan position. A matching algorithm was used to search for the echoes arising from the same defect. The accuracy obtained from imaging the defects was better than one wavelength. Prefiltering was necessary to eliminate some of the artefacts in the image.