Transmitted light microscopy
is the general term used for any type of microscopy where
the light is transmitted from a source on the opposite
side of the specimen from the objective. Usually the light
is passed through a condensehrough the specimen, the image
of the specimen goes through the objective lens and tor
to focus it on the specimen to get very high illumination.
Ater the light passes t the oculars where the enlarged
image is viewed.
Transmitted light microscopic
techniques were the first ones developed as the microscope
was being developed.
The microscopic techniques
requiring a transmitted light path include brightfield,
darkfield, Zernicke phase (or just phase) and differential
interference contrast (or Nomarski) optics. Other not
as commonly used transmitted light techniques include
Hoffman modulation, Varel optics, and polarization optics.
In order to get a usable
image in the microscope, the specimen must be properly
illuminated. The light path of the microscope must be
properly set up for each optical method and the components
used for image generation. The condenser was invented
to concentrate the light on the specimen in order to obtain
a bright enough image to be useful. Different ways of
setting up the light path were worked out. But the best
setup for proper specimen illumination and image generation
is known as Köhler illumination after the man who
invented it. It is used for most of the optical setups
here for a discussion of how to set up a microscope
for Köhler illumination.