Patent ID: 7574915

Claim:
A method of inspecting a structure, the method comprising: coupling an ultrasonic transducer with a first structure portion free of defects and determining impedance-plane calibration coordinates corresponding to quadrature-phase separated components of a sinusoidal signal; lifting the ultrasonic transducer from the first structure portion and determining impedance-plane lift-off coordinates corresponding to quadrature-phase separated components of a sinusoidal signal; coupling the ultrasonic transducer with a structure portion to be inspected and determining impedance-plane inspection coordinates corresponding to quadrature-phase separated components of a sinusoidal signal; rotating the calibration coordinates, lift-off coordinates, and inspection coordinates at least until both the calibration coordinates and lift-off coordinates lie upon and are spaced along a first axis such that a first one of the rotated calibration coordinates and a first one of the rotated lift-off coordinates have different values and a second one of the rotated calibration coordinates and a second one of the rotated lift-off coordinates have a common value; and activating an indicator if the rotated inspection coordinates are at least disposed in a predefined relationship to the first axis.