PROCESSING THE COHERENT ANOMALIES OF DIGITALIZED SURFACES IN WAVELET DOMAIN

Coherent anomalies can affect the quality of digitized images. In this paper the method, which was developed for their removal in images from old movies, is proposed in the contest of a metrological application in nanotechnology, where accurate thickness measurements of special coatings are obtained after an image processing. The method constructs a piece-wise spline approximation to restore the corrupted data in the low-pass filtered version of the digitized image obtained by a wavelet decomposition. An invisible reconstruction of the damaged area are obtained, since the type of the morphology in suitable domains is preserved. Simple statistical tests are able to automatically recognize the morphology typand to construct the appropriate approximation. The calibration study that have been performed for identify the test thresholds is described in the paper. It uses simulated images with different types of noise and of scratches. The benefit of the method adopted to locally preprocess the metrological image before acquiring the measurements is finally discussed.