Superresolution in far-field imaging

We demonstrate the feasibility of achieving superresolved images by using Fourier-plane phase masks and image multiplication, which together create effective point-spread functions that are not positive definite and therefore cannot be created by any single Fourier plane mask in a linear system. Three different configurations were investigated, all of which gave a spatial resolution exceeding that corresponding to the full open aperture of the optical system. One price that must be paid for the superresolution is inefficient use of the light source.