A Fourth Order Diffusion Filter for Speckle Noise Removal

Standard second order speckle reducing diffusion filters produce staircase artefacts (step edges) in the filtered image. In this paper we present an anisotropic fourth order diffusion filter with diffusion coeficients as functions of speckle statistics.This filter steers the diffusion unevenly in the directions of gradient and level set, and hence preserves the edges while removing the noise. The experiments show that the proposed filter outperforms the existing second order speckle reducing filters in terms of staircase artefacts without destructing the edges.