Patent ID: 8159216

Claim:
An eddy current imaging method for the detection and characterization of defects concealed in a complex structure, comprising the steps of: positioning ( 72 ) means ( 10 ) for measurement of a surface magnetic field in the vicinity of a substantially planar inspection surface region ( 12 ) of a target material ( 4 ); generating ( 74 , 82 ) a global uniform exciting magnetic field in the target material ( 4 ) over a whole of the inspection surface region ( 12 ); and measuring ( 76 , 84 ) a resultant magnetic field produced by the target material ( 4 ) at the inspection surface region ( 12 ) in the form of a raw image, the raw image ( 192 , 194 , 196 , 198 ) consisting of a plurality of binary data vectors having a dimension equal to or greater than 2, each vector being associated with a quantity of the resultant magnetic field, sensed in the vicinity of a plurality of points in the inspection surface region ( 12 ); wherein the generating step ( 74 , 82 ) comprises generating a set ( 60 ) of at least two exciting magnetic field waveforms ( 62 , 64 ) uniformly in the target material ( 4 ), each distinct waveform ( 62 , 64 ) determined by a narrow frequency spectrum and an angle of orientation in the target material ( 4 ), the frequency spectrum of each waveform being selected as a function of a desired observation depth in the target material ( 4 ), wherein the measuring step ( 76 , 86 ) comprises measuring a set of configurations of the resultant magnetic field in the form of a set ( 160 ) of raw images ( 192 , 194 , 196 , 198 ), each of the raw images ( 192 , 194 , 196 , 198 ) associated with a quantity and with a waveform ( 62 , 64 ) of the exciting magnetic field, and further comprising a step ( 90 ) of processing the set ( 160 ) of raw images by combining them, to detect a defect and determine the position and the nature thereof.