Achieving sub-Rayleigh resolution via thresholding.

Diffraction from a finite-diameter entrance pupil imposes the Rayleigh bound on the spatial resolution achievable by a conventional imaging system. We demonstrate resolution beyond this limit through unstructured scanning of a focused laser beam across an object together with dynamic application of a threshold N less than the maximum count level Nmax. Experimental results show sub-Rayleigh resolution enhancement by a factor of [ln(Nmax/N)]1/2.