Nonlinear processing of a shift-invariant discrete wavelet transform (DWT) for noise reduction
Markus Lang, Haitao Guo, Jan Erik Odegard, C.S. Burrus, Raymond O. Wells · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1995
A novel approach for noise reduction is presented. Similar to Donoho, we employ thresholding in some wavelet transform domain but use a nondecimated and consequently redundant wavelet transform instead of the usual orthogonal one. Another difference is the shift invariance as opposed to the traditional orthogonal wavelet transform. We show that this new approach can be interpreted as a repeated application of Donoho's original method. The main feature is, however, a dramatically improved noise reduction compared to Donoho's approach, both in terms of the l2 error and visually, for a large class of signals. This is shown by theoretical and experimental results, including synthetic aperture radar (SAR) images.