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. (C) 2002 Optical Society of America.