Setting Of Transmitted-Light Phase Contrast - Zeiss Axiovert 200 Operating Manual

Axiovert 200
3.3.2

Setting of transmitted-light phase contrast

3.3.2.1 General principle
The phase contrast technique is ideal for examinations of thin, unstained specimens, e.g. culture cells.
The human eye is unable to recognize phase differences (differences in refractive index and thickness)
between the various cell components.
The phase contrast technique uses the optical modulators "phase stop and phase ring" and the
interference procedures during the formation of the intermediate image to change the small phase
differences in intensity and color differences which are visible to the human eye.
The high-intensity, direct light components are attenuated using the annular channel optically defined as
"phase stop and phase ring", and a constant phase shift is applied. The indirect light components
diffracted at various cell components, however, by-pass this optical channel and are influenced by the in-
phase refractive index and the thickness differences of the specimen.
In the intermediate image plane, the differently influenced partial beams interfere and are enhanced or
attenuated – depending on the phase position. This interference results in image contents displaying
intensity and color differences which can be recognized by the human eye.
3.3.2.2 Configuration of the Axiovert 200 (manual) and Axiovert 200 M
Phase contrast objectives with phase rings Ph 0, Ph 1, Ph 2 or Ph 3 for different average numeric
apertures which can also be used in brightfield without any restriction.
Condenser with turret containing centering phase stops Ph 0, Ph 1, Ph 2 and Ph 3 for various medium
numeric apertures.
The activated phase stop on the condenser must match with the relevant description on the objective,
e.g. Ph 1.
B 40-080 e 03/01
OPERATION
Illumination and contrasting techniques Carl Zeiss
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