A filter design technique for improving the directional selectivity of the first scale of the dual-tree complex wavelet transform

  • Authors:
  • Bart Goossens;Aleksandra Pižurica;Wilfried Philips

  • Affiliations:
  • Ghent University, TELIN, IPI, BBT, Ghent, Belgium;Ghent University, TELIN, IPI, BBT, Ghent, Belgium;Ghent University, TELIN, IPI, BBT, Ghent, Belgium

  • Venue:
  • ICIP'09 Proceedings of the 16th IEEE international conference on Image processing
  • Year:
  • 2009

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Abstract

The Dual-Tree complex wavelet transform (DT-CWT) uses approximate Hilbert transform pairs of wavelet, which requires that the filters of each tree of the dual-tree structure should be delayed approximately one half sample from each other. However, the filters of the first (finest) scale of the transform do not obey this condition, resulting in a poor directional selectivity for the first scale. In this paper, we describe a design technique for first-scale infinite impulse response (IIR) wavelet filters, that solves this problem. Results demonstrate that a much better directional selectivity is obtained, which indicates a performance improvement for many applications that use the DT-CWT where the preservation of high-frequency information is important.