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10. Trouble Shooting
Problem
Bright Field
The specimen can not be brought into focus.
Dark Field
No definite DF contrast is possible.
The image is unevenly or not uniformly illumi-
nated.
Undesirable stray light
Phase contrast
No phase contrast is possible.
Cause/Remedy
Use the correct immersion medium.
Lay the specimen with the cover glass to-
wards the top.
Make sure that the cover glass thickness is
correct and that is conform to the indication
on the objective.
Check the condenser centering.
Be sure that a DF objective is being used.
The objective aperture setting is too high
(maximum 0.75). If necessary, reduce the ob-
jective aperture using the iris diaphragm on
the objective.
Check the condenser centering.
The magnification is too weak. Use a higher
magnification.
Clean the specimen and neighboring lenses
(→
p. 65).
The specimen is too thick.
The refraction index of embedding material
and object is identical.
The cover glass is not placed evenly.
Therefore, check the centering of the light
rings (→
p. 39).