Scanning near-field optical microscopy approximation

The resolution of a conventional microcope is limited by the classical phenomena of interference and diffraction. The limit is approximately X/2, X being the wavelength. This limit can be overcome by using a sub-wavelength light source and by placing the sample very close to this source (i.e. in the near field). The relevant domain is near-field optics (as opposed to far-field conventional optics), which has been applied to microscopy, spectroscopy and optical sensors. In particular, nearfield scanning optical microscopy (N SOM) has proved to be a powerful tool in physical, chemical and life sciences (Dunn, 1999). 

Optical characterization methods suffer restricted spatial resolution due to the Abbe limit at approximately X/2. Near-field scanning optical microscopy (NSOM or SNOM) developed in order to overcome this limit, using the kind of sophisticated feedback mechanisms developed for AFM and STM to scan an optical fibre, drawn to an aperture with a diameter... 

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