2. Principle

The theoretical determination of the image of an object in near-field optical microscopy is a problem of diffraction of electromagnetic waves by a system consisting of the object and the probe.

Many different configurations have been tested in near-field optical microscopy. They all use the same operating principle: evanescent waves are transformed into homogeneous waves.

In this section, we present a theo-ric approach. We'll confine ourselves to using a scalar theory in which the vector and polarization properties of light are ignored. But this formalism is sufficient to describe the general principles of near-field optical microscopy.