It is necessary to use the information contained in the near field to get sub-wavelength details in optical imaging which are not revealed through the far-field image. We have designed and built various setups able to perform, near-field measurements in the UV, visible and IR, both in transmission, reflection and dark field with a resolution of 10 nm, independent of the wavelength but related to the tip size. Images revealing local dielectric contrasts, small particle effects, as well as local field enhancements in random structures, are shown.