Medical Term:
dark-field illumination
Definition: a procedure in which a black circular shield is used to block most of the vertically directed rays of light (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 optic axis; thus, the object is well illuminated in a contrasting dark background.
Synonym(s): dark-ground illumination
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Examples: glitazone, GI cocktail, etc.
