Dark Field

imageDark field microscopy creates contrast between the object and the surrounding field of view. As the name implies, the background is dark and the object is bright.

An annular stop is used to create a cone of oblique illumination, thus with no specimen present all the light from the condenser misses the objective entirely, giving a dark background. However, if a specimen containing reflective structures is placed into the path of this illumination, light that hits such a structure will be reflected at all angles. Some of this light will now reach the objective and so will appear bright.

This method produces a great deal of glare, therefore the specimen often appears as a bright silhouette rather than a bright object, of which little detail can be determined. Dark field microscopy is ideal for reflectively labelled specimens and also works well for delineating plant cell walls on unlabelled tissue sections and can be performed across a whole range of magnifications.