Ringing reduction for radially restored images

This paper demonstrates a ringing reduction method for radially restored images, whose blurred versions are produced by a spherical single lens imaging system (SSLIS) embedded in an experimental camera module. The method is capable of reducing two types of ringing: those near object edges of sharp intensity transitions inside a restored image are reduced by detecting pixel intensity differences that are higher than a threshold intensity level, and replacing the corresponding pixels from a further smoothed version of the captured image; and those around image center and four boundaries of the restored image are suppressed by nearest neighbor interpolation for the upper boundary and arc-shaped boundaries of the polar image converted from the captured image. Visual evaluation shows that both types of ringing artifact in the radially restored image are greatly suppressed by the proposed method compared to the resulting image without the ringing reduction step.