Abstract: A method of detecting defects using eddy currents is disclosed. The method comprises: exciting eddy currents in a test material using an eddy current probe driven by a drive signal; detecting induced eddy currents in the test material; converting the detected signal into integer values using an analog to digital converter; and adding or subtracting the generated integer values to or from each of two accumulators, or taking no action, so that one accumulator produces a value proportional to one component of the detected signal and the other produces a value proportional to another component of the detected signal and using these values to detect the presence of a defect.

Abstract: A method of operating an ultrasound imaging system having an array of transducer elements. The method comprises transmitting a plurality of ultrasound signals, each transmission using a different sub-aperture of the array, receiving a plurality of reflected ultrasound signals by a receive array corresponding to each sub-aperture transmission, calculating a coherency factor corresponding to the proportion of coherent energy in the received signals from each sub-aperture transmission and weighting the received output by the calculated coherency factor, and synthesizing all weighted outputs under all different sub-aperture transmissions.

Abstract: Variations in the lift-off separation between a probe and the surface of a structure to be tested often mask the detection of defects in the structure. A method and apparatus for automatically classifying and compensating for variations in the lift-off is described. A reference signal at a known lift-off may be weighted by a corresponding calculated ratio parameter and subtracted from a test signal to compensate for lift-off. A number of reference signals are preferably obtained and the largest magnitude gradient for each reference signal is preferably determined. The largest magnitude gradient for subsequent test signals is also obtained and the corresponding reference signal with the closest largest magnitude gradient to the test signal is identified and the corresponding reference signal is selected in the related compensation procedure. Such a method has been found to restore the signal such that lift-off is removed and defects are easily identified.