I am trying to understand exactly why we can beat the diffraction limit when using near-field scanning optical microscopy (NSOM). For those who aren't familiar with NSOM, check out this article: http://www.optics.rochester.edu/workgroups/novotny/papers/history4.pdf.
I can't find any resources that explicitly explain why working in the near-field allows us to circumnavigate the diffraction limit, and I like to have things explained step-by-step. I understand that, in the near-field, we are at a working distance of much less than the wavelength of the light source (and the aperture is also much smaller than the wavelength of the light). Thus, the path length difference of different rays at the object will not be long enough to introduce construction/destructive interference - the basis for diffraction. I know that evanescent waves also contribute to greater resolution, but I don't fully understand how or why. I was hoping someone could explain this to me.