Patent ID: 7389206

Claim:
A method for inspecting an object, the method comprising: applying a pulsed excitation signal to the object; detecting a transient response signal to the pulsed excitation signal; selecting a segment of the transient response signal obtained over a time interval Δt; convolving the transient response signal obtained over the time interval Δt with a plurality of orthogonal functions to generate a plurality of orthogonal components corresponding to a fundamental frequency f=1/Δt, wherein the convolving step is performed at a first frequency f1=1/Δt; using the plurality of orthogonal components corresponding to the fundamental frequency f=1/Δt to detect a presence or an absence of a defect in the object; and selecting a plurality of segments of the transient response signal obtained over respective time intervals {Δt2, . . . Δtn}, wherein the convolving step is repeated for the plurality of segments to generate a plurality of sets of orthogonal components corresponding to respective ones of a plurality of frequencies f={1/Δt2, . . . , 1/Δtn}, and wherein each of the sets of orthogonal components corresponds to a respective depth Δz in the object.