Super-resolution Aperture Scanning Microscope

Abstract

THE classical theory of the resolving power of optical instruments implies a limit to the observation of details in an object if these are significantly smaller than one wavelength, λ₀, of the illuminating radiation. This Abée barrier is not entirely impenetrable. Lukosz^1,2 has shown how an improvement by a factor of two can be made by the use of complementary spatial filters. Attempts to proceed further in this direction are soon frustrated, however, because the spatial frequencies one is seeking to transfer are such that the waves become evanescent in the direction in which one would like them to propagate. Nassenstein has developed an ingenious scheme³ in which evanescent waves are used to illuminate the object, and a magnified image is obtained using a holographic technique. The resolution capability is determined by the wavelength of the evanescent wave. This is less than λ₀, but it is not easy to devise systems where it would be very much smaller.