37
NIB610/NIB620
3
3.4.7. Aperture diaphragm (condenser diaphragm)
The aperture diaphragm (condenser diaphragm) adjusts the numerical aperture
of the illumination system. The correct setting of the aperture diaphragm is impor-
tant for the resolution, brightness, contrast and depth of field of the microscope
image.
A
1
I
2
Open (O) Closed (C)
Illustration 023 A/B: NIB610/NIB620 - Adjusting the aperture diaphragm.
CT
B
6
70-80%
100%
5
4
3
Aperture diaphragm lever to the right:
The aperture diaphragm is closed
reducing resolution and brightness, and
increasing contrast and depth of field.
Aperture diaphragm lever to the left:
The aperture diaphragm is open, which
increases resolution and brightness and
reduces contrast and depth of field.
The resolution, brightness,
contrast and depth of field properties
are interrelated and cannot be set
independently.
Based on the specimen, adjust the
aperture diaphragm accordingly.
Adjust the aperture diaphragm
every time you switch the objective.
The aperture diaphragm must nev-
er be used to adjust the light intensi-
ty, only to regulate the contrast.
Adjusting the aperture diaphragm
while observing the actual diaphragm
image through the eyepiece sleeve.
Place the 10x objective into the optical path
and focus the sample to be examined.
It is recommended to use the
10x objective for exact aperture
diaphragm adjustment.
Remove one of the eyepieces (3).
Insert the centering telescope (CT) (4) in the
eyepiece sleeve.
Rotate the eyepiece of the CT to adjust the
focus.
This reveals the objective pupil plane (5) and
the image of the aperture diaphragm (6).
In addition, a black phase ring of
the 10x phase objective is visible. This
does not interfere with the setting.
Move the aperture diaphragm lever (Fig.A/1)
so that the size of the aperture diaphragm
image is 70-80% of the size of the objective
pupil plane. This setting gives a reasonable
contrast and a favourable image.
After adjustment, remove the CT and reinsert
the eyepiece.
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