It is now wvell established in principle that superresolving optical systems can be made. Such systems, when viewing objects of finite extent, can resolve detail finer than the normal diffraction limit. This has obvious attractions for microscopy, but we may wonder whether the ultimate diffraction limit for a lens of large numerical aperture, the limit which counts in microscopy, can be beaten. Can detail smaller than one half the wavelength of light really be made visible? It can be, but only in specialized and probably limited applications.
CHARLES W. MCCUTCHEN, "Superresolution in Microscopy and the Abbe Resolution Limit," J. Opt. Soc. Am. 57, 1190-1190 (1967)