illumination
(il-oo‵-mĭ-nā'shŏn 
)
[L. illuminare, to light up]
The lighting up of a part for examination or of an object under a microscope.
axial i.Light transmitted along the axis of a microscope. SYN: central illumination.
dark-field i.The illumination of an object under a microscope in which the central or axial light rays are stopped and the object is illuminated by light rays coming from the sides, which causes the object to appear light against a dark background. This technique is used to observe extremely small objects such as spirochetes or colloid particles.
direct i.The illumination of an object under a microscope by directing light rays upon its upper surface.
fiber i.The transmission of light to an object through fiber-optic cables.
focal i.Concentration of light on an object by a mirror or a system of lenses.
oblique i.Illumination of an object from one side.
through i.Passage of light through the walls of an organ or cavity for medical examination.
SEE: transillumination.
transmitted light i.Illumination in which the light is directed through the object. Light may come directly from a light source or be reflected by a mirror.