Using optical defocus to denoise

Effective reduction of noise is generally difficult because of the possible tight coupling of noise with high-frequency image structure. The problem is worse under low-light conditions. In this paper, we propose slightly optically defocusing the image in order to loosen this noise-image structure coupling. This allows us to more effectively reduce noise and subsequently restore the small defocus. We analytically show how this is possible, and demonstrate our technique on a number of examples that include low-light images.