Setting Of Transmitted-Light Phase Contrast - Zeiss Axioskop 2 plus Operating Manual

Axioskop 2 plus
Axioskop 2 mot plus
3.3.3

Setting of transmitted-light phase contrast

(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 see phase differences (differences in refractive index and thickness) between
the different 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 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 different cell components, however, by-pass this optical channel and are influenced by the
in-phase refractive index and the thickness differences in 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.
(2) Configurations of the manual Axioskop 2 plus and the Axioskop 2 mot plus
− Phase contrast objectives with phase rings Ph 1, Ph 2 or Ph 3 for different average numeric apertures
which can also be used in brightfield without any restriction.
− Universal condenser with turret disk containing centering phase stops Ph 1, Ph 2 and Ph 3 for different
average numeric apertures.
− The inserted phase stop on the universal condenser must match the appropriate label on the objective,
e.g. Ph 1.
☞
In the Axioskop 2 mot plus, the allocation of the phase stop in the condenser turret to the
relevant phase contrast objective in the nosepiece is stored after pressing the Set key. This
ensures the combination of phase contrast objective and phase stop always being set correctly.
B 40-075 e 02/01
OPERATION
Illumination and contrasting techniques Carl Zeiss
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