Reducing Ringing Artifact Caused by Inaccurate Depth Estimate for Space-variant Image Debluring

Restoring defocused image is a challenging problem partly because the blur level of the image is space-variant for scenes with non-uniform depth. The most noticeable artifact of debluring is the ringing around object boundary. Counterintuitively, we find that inaccurate depth estimate at object edges is the major cause of the ringing artifact. We mathematically analyze the relationship between the ringing artifact and the inaccurate depth estimate and propose a debluring algorithm that selectively smoothes the imperfect depth map. Experimental results show the visual quality of the recovered images is greatly improved.