Application of real-time 3-D SAFT in the tandem mode

This paper presents a description of what tandem SAFT is as contrasted with pulse-echo SAFT. The implementation of tandem SAFT is far more complicated than pulse-echo SAFT and puts greater demands on computer processing speed and/or virtual computer memory capacity. Tandem SAFT has been implemented by using look-up tables for determining path lengths so that no computations are needed during processing. Furthermore, the tandem SAFT has been developed for operation on a special-purpose parallel processor so that speeds of 10 A-scans/s can be achieved. A series of studies have been made of system performance showing resolution performance, effects of saturation on imaging, defect orientation effects, sizing criteria, and difficulties encountered on thin specimens when using tandem SAFT. (orig.)