Figure 13From: Application of the topological derivative to post-processing infrared time-harmonic thermograms for defect detectionTopological derivative on \(\varGamma _{\mathrm{front}}\) combining several frequencies and lamp locations. Left: topological derivative corresponding to six linearly spaced frequencies between 0.2 and 2 Hz and a 2-by-2 grid of lamps. Right: counterpart when a 3-by-3 grid of lamps is used. The appearance of spurious minima is highly reduced in both cases due to the multifrequency character, and increasing the number of lamps highly improves the reconstructionsBack to article page