See Also: condenser, dark field(medicine)
dark-field condenser(medicine)
paraboloid dark field condenser(medicine)
cardioid dark field condenser(medicine)
dark field illumination(medicine)
dark field objective(medicine)
dark field slides(medicine)
dark-field microscope(medicine)
dark field microscopy(medicine)
dark field imaging(medicine)

condenser, dark field (medicine)


condenser, dark field
<microscopy> A condenser forming a hollow cone of light with its apex (or focal point) in the plane of the specimen. When used with an objective having a numerical aperture lower than the minimum numerical aperture of the hollow cone, only light deviated by the specimen enters the objective. Objects are seen as bright images against a dark background.

The ordinary bright field condenser of low power, used with a central stop, makes a good dark field condenser. They all form a dark field while illuminating the specimen with a hollow cone of light. The lower limiting aperture of the condenser must be greater than the numerical aperture of the objective with which it is to be used. Thus, no direct light enters the objective, the specimen is seen by reflected or scattered light on a dark background.

See: condensers

See: special dark field condensers: paraboloid, cardioid and Cassegrainian.