Figure 3

Removal of ring artifacts from an electrolytic capacitor image. (a) Uncorrected, original image. (b-f) Corrected images by applying the modified wavelet method without normalization (L _max = 3, k ₀ = 5.85 and T _HN = 0.33), WF (L = 3, wname='db43' and σ = 7.5), RCHT (W = 125 and T = 0.0023), RCP and MWPN (L _max = 2, k ₀ = 5.85 and T _HN = 0.33, N = 4) methods, respectively. Without using the normalization technique, the modified wavelet method alone is not appropriate to delete the weak rings (such a ring is shown in (b) as marked by an arrow). Wavelet-Fourier method blurs the image in different regions as marked by boxes. (g-i) Zoomed view of the ROIs (b), (e) and (f), respectively. The effectiveness of the normalization technique in removing the weak rings is evident in (f). (j-l) Effect of the pre-correction using [17]. Corrected ROIs are shown in (j-l) by the WF (L = 3, wname='db43' and σ = 7.5), RCHT (W = 125 and T = 0.0023) and RCP methods (applied on the pre-corrected image), respectively. It is illustrated that as the varying intensity rings are pre-corrected, therefore, the remaining mis-calibration rings are suppressed by these three methods. But blurring is observed at the ring location marked by dashed boxes due to the longer filter lengths in these three methods. Same window settings 'C/W = 0.5880/0.1686' are used for all sub-figures.