Dark Field Microscopy
Dark field microscopy may be defined as a system set up so that the minimum effective numerical aperture (N.A.) of the condenser exceeds the maximum effective N.A. of the objective. In this technique , the specimen is seen as bright object against a dark background.
The illumination in this case resembles to that used in phase contrast microscopy, because the annular stop or dark field stop is necessary. This device is generally placed below the condenser which eliminates all light from the central portion to produce a hollow cone of light incident upon the specimen. In contrast to the phase - contrast microscopy, objective in this case works within the area of dark cone.
