Dark Field Microscopy

Dark field microscopy is a method which also creates contrast between the object and the surrounding field. As the name implies, the background is dark and the object is bright. A annular stop is also used for dark field, but the stop is now outside the field of view. Only light coming from the outside of the beam passes through the object and it cannot be seen directly. Only when light from the stop is deflected and deviated by the object can it be seen. This method also produces a great deal of glare and therefore the specimen often appears as a bright silhouette rather than as a bright object of which much detail can be determined. The following diagram shows the setup of the dark field light path.

(Redrawn from Gray)*

Please remember that when using dark field optics, that any dirt or dust or other garbage on your slide or specimen will shine just as brightly as your object of interest. Make sure your slide is immaculately clean.

*Diagram redrawn from Gray , P. 1964. Handbook of Basic Microtechnique McGraw-Hill: New York. 

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