OPERATION
Axio Observer
Illumination and contrast techniques
ZEISS
12/2016
431004-7244-001
149
5.12.2.3
Setting up transmitted light phase
contrast
•
Swivel the phase contrast objective, e.g. Ph 1,
into the optical path.
•
On the condenser turret select the phase stop
with the same designation as the phase
contrast objective (e.g. Ph 1).
•
To check the centering and the congruence of
the bright phase stop (in the condenser) with
the dark phase plate (in the objective), remove
one eyepiece from the tube and replace it with
the centering telescope. Using the centering
telescope's correction facility, focus on the
phase stop and the phase plate in the exit pupil
of the objective.
If the phototube is used, the Bertrand lens can also
be inserted in order to observe the exit pupil of the
objective. Where the Bertrand lens is used, the
Optovar turret selector wheel must be set to factor
1x.
•
If the congruence is not perfect (Fig. 151/
A
),
the bright stop must be centered using two 1.5
mm Allen keys (Fig. 150/
1
) until it is completely
congruent with the dark phase plate
(Fig. 151/
B
).
•
Finally, remove the centering telescope from the
tube and replace it with an eyepiece / remove
the Bertrand lens from the optical path.
It is not usually necessary to center the phase
stops, as they are factory centered.
To enhance image contrast, a wide-band
interference filter, green 32 x 4, can be inserted in
the filter changer. Perfect phase contrast is only achieved if the bright phase stop (in the condenser) and
the dark phase plate (in the objective) are precisely congruent in the illumination beam path (Fig. 151/
B
).
All phase contrast objectives used require adjustment of the phase plates. When examining
liquid objects in small vessels, the optical path must be aligned to the center of the vessel, as
liquids at the edge of a vessel act as a lens and adversely affect the microscope image.
Fig. 150
Centering the phase stop on the
condenser
Fig. 151
Centering the phase stop (bright
ring in condenser) to the phase ring
(dark ring in objective)
Summary of Contents for Axio Observer Series
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