DARK FIELD MICROSCOPY

Dark field microscopy allows viewer to observe living unstained cell and organisms simply by changing the way in which they illuminate the object.

A hollow cone of light is focused on the specimen in such a way that unreflected and unrefracted rays do not enter the objective.

Only light that has been reflected or refracted by the specimen forms the image

The field surrounding specimen appears

dark while the object brightly illuminated.

The dark field microscope can reveal considerable internal structure in larger eukaryotic microorganism.

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USES OF DARK FIELD MICROSCOPY Unstained, transparent and absorb little or no light. To study insects, fibers, hairs, yeast and protozoa as well

as some minerals and crystals, thin polymers and some ceramics.

In the research studying of live bacterium, as well as mounted cells and tissues e.g. Treponema pallidum, Leptospira, Vibrio cholera, Campylobacter jejuni, Endospore

It is more useful in examining external details, such as outlines, edges, grain boundaries and surface defects than internal structure.

Recently, dark field combined with other illumination techniques, such as fluorescence, which widens its possible employment in certain fields.

BRIGHT FIELD VS.DARK FIELD MICROSCOPY

Advantages

The advantage of darkfield microscopy also becomes its disadvantage: not only the specimen, but dust and other particles scatter the light and are easily observed

For example, not only the cheek cells but the bacteria in saliva are evident.

The dark field microscopes divert illumination and light rays thus, making the details of the specimen appear luminous.

Dark field light microscopes provide good results, especially through the examination of live blood samples.

It can yield high magnifications of living bacteria and low magnifications of the tissues and cells of certain organisms.

Certain bacteria and fungi can be studied with the use of dark field microscopes.

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