Dark field microscopy enhances the visibility of transparent living organisms, making it ideal for identifying spirochaetes in exudate. This technique modifies light rays so that only oblique rays illuminate the observed objects while the background remains light-free. The method utilizes various diaphragms and phase plates to control the light, differing from traditional bright field microscopy.

3. Transparent living organisms can be more
easily seen with dark field microscope This
method is particularly useful when one is
attempting to identify spirochaetes in exudate

4. To achieve the dark effect
it is necessary to alter the light rays
that approach the objective
in such away only oblique rays strike the objects
being viewed

5. The obliquity of the must be extreme
that if no object are in the field
the background is completely
light free objects in the field
become brightly illuminated however
by the rays that are reflected up
through the lens system of microscope

6. Darkfield production
star diaphragm
dark field condenser

7. Phase contrast microscope
first developed by Frederick Zernike
referred as Frederic microscope instrument. To
study living transparent cell

8. Various configurations o
f diaphragms and materials that can be used to retard or advance the direct light ray
it differs from bright field
different type of diaphragm
phase plate
the diaphragm consists of annular top
allow only hollow cone of light to pass
rays through the condenser
to the object on the slide
the phase plate is a special
optical disk located
at rear focal plate of objective
it has a phase ring on it
that advance or retard the direct light ray
¼ wave length