Leica DM5500 B Manuel D'utilisation page 83

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 it suits the indication on the
objective.
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. 85).
The specimen is too thick.
The cover glass is not placed evenly.
Check the centering of the light rings (→ p. 52).
11. Trouble Shooting
83