Abstract: An eddy current imaging system includes an eddy current sensing coil positioned proximate a workpiece for scanning the workpiece to produce a signal indicative of the integrity of the workpiece for regions in an x,y array of data. Such a signal may be a complex impedance signal representative of the amplitude and/or the phase of the signal. Two data processing techniques are disclosed for enhancing the display of a flay in the workpiece. The first includes the step of calculating a spatial derivative of the amplitude and/or phase indicative signal from the coil and providing an image of the spatial derivative to produce a C scan of the spatial derivative. The second includes the steps of determining the regions of maximum ascent and/or descent of the signal for regions in the scan and calculating an impedance plane trajectory from the data array of path points for displaying a reconstructed optimum signal independent of path pattern.

Abstract: A method of nondestructively identifying regions "R" of high density in a substrate (10) of a bonded matrix of carbon fibers by resistively heating the substrate and taking an infrared image of the heated substrate. Terminals 12, 14, 16 and 18 are connected to a power supply 26 by wires 22 and cable 24 of which they are a part, to effect the heating.