73
7. Start-up
edges of the image should have the same dis-
tance to the outer edge of the fi eld of view on
all sides. If not, recenter the image with the
centering screws. Adjust the height of the con-
denser until the edges are sharp. Now open
the fi eld diaphragm until the image fi lls the
entire fi eld of view and the black edges have
disappeared completely (91.d).
• The last step is the adaptation of the contrast
settings. To improve the contrast, close the ap-
erture diaphragm – if you close it too far, how-
ever, the resolution of the image details will
deteriorate.
To see the aperture diaphragm, remove an
eyepiece tube and look directly into the tube.
Your eye should be around 10 to 20 cm from
the tube. Change the size of the aperture dia-
phragm until its image is clearly visible in the
pupil of the objective.
• Set the aperture diaphragm to cover 2/3 to 4/5
of the pupil diameter. You will now have the
optimal balance between resolution and con-
trast.
7.6.2 Incident Light - Fluorescence
Leica DMI3000 B:
• Select an objective with moderate magnifi ca-
tion (10x–20x) and adjust the image.
• Close the fi eld diaphragm with the turning knob
until the edge of the diaphragm (round or an-
gled) appears on the specimen level.
• If the limits of the fi eld diaphragm are not in the
center of the fi eld of view, move the position
of the fi eld diaphragm to the center with the
two centering screws on the right side of the
stand using a 3 mm Allen key. When center-
ing, observe the position of the fi eld diaphragm
through the eyepieces or on the monitor.
• Open the light fi eld diaphragm until it just dis-
appears from the fi eld of view.
a
b
cd
Fig. 91 Köhler Illumination
a Field diaphragm not focused, not centered
b Field diaphragm focused, but not centered
c Field diaphragm focused and centered
Diameter is too small, however
d Illumination fi eld diameter = visible fi eld diameter
(Köhler illumination)
Fig. 90 Condenser centering
1 Centering openings
2 Height adjuster
3 Prism and phase ring centering
2 1
3
21
3
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