We have examined the local optical fields within a few wavelengths off the surface (middle-field region, $\mathrm{kr}<\mathrm{}1\mathrm{}–50)$ by scanning an optical probe in collection mode in the overlap region of the incident and scattered optical waves. We have applied an analytical dipole model and have used optical space and time coherence to describe the recorded image of submicron-sized particles on a substrate. We find that the relative intensity of the lateral and vertical standing waves gives information about the local polarizability of the particle and the support surface as well as information about the polarization of the incident beam, its wavelength, the distance of the image plane, and the tilt of the image plane with respect to the surface.

• Received 4 July 2002

DOI:https://doi.org/10.1103/PhysRevB.66.233404