Dark-field illumination, a procedure in which a black circular shield is used to block the majority of the vertically directed rays of light (e.g., the field is dark), and a circumferential, suitably angled, mirrored surface is used to direct the peripheral rays horizontally against the object, thereby reflecting the light vertically through the objective lens and along the optical axis; thus, the object is well illuminated in a contrasting dark background.
Synonym: dark-ground illumination.
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... that the frogs are infected by the spores when their skin comes into contact with the infected water. The fungus is also thought to invade the ... transmitted light microscope. Some utilizing "circular oblique illumination or COL as we call it. All images are at 7 megapixel, except ...
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