Imaging with the Photon Scanning-Tunneling Microscope

The use of traditional optics in microscopy has a well-known resolution barrier first presented by Lord Rayleigh. This is the "Rayleigh diffraction limit." In the usual textbook example, the overlapping diffraction rings from two small objects are set so that the central maximum of one pattern falls on the first minimum of the second, The barrier limits the resolution of conventional microscopes to a significant fraction of the wavelength of light.In the past decade two methods were discovered for surpassing the Rayleigh diffraction barrier. The first was actually an independent rediscovery by D. Pohl er al. of a concept originally proposed by Synge (in a 1928 paper reviewed by Albert Einstein),