Operation
Axiostar
plus
Transmitted-light darkfield
Carl Zeiss
B 40-815 e 12/01
3-11
Setting darkfield contrast with immersion
oil darkfield condensers
•
If necessary, swivel open the wide-angle
unit, colored disk carrier, polarizer or
λ
plate.
•
Move condenser carrier down until it makes
contact.
•
Place immersion oil darkfield condenser in
darkfield condenser carrier (see section 2).
•
Place darkfield condenser carrier in
condenser carrier and center approximately
so that when the condenser carrier moves
the condenser moves into the gap of the
mechanical stage without making contact.
•
Move condenser up until it makes contact.
•
Place a drop of immersion oil (without
bubbles, if possible) on the center of the
condenser.
•
Place specimen. The immersion oil will
disperse due to the capillary effect between
the top of the condenser and the bottom of
the specimen holder.
•
Slightly move the mechanical stage back
and forth to dissipate any air bubbles in the
immersion oil.
•
Set lamp brightness to maximum and open
luminous field diaphragm completely.
•
Swivel in objective with a small
magnification (e.g. 10x) and focus the
specimen with the focusing drive. Then step
by step swivel in the next largest dry
objectives and focus the specimens with the
focusing drive.
•
Center the luminous field diaphragm on the
condenser carrier with the adjustment
screws and focus with the condenser drive.
•
Place one drop of immersion oil on the
specimen location, swivel in immersion oil
objective and focus specimen.
•
Close luminous field diaphragm by turning
luminous field diaphragm ring
counterclockwise until it makes contact.
•
Lower the condenser until the edge of the
luminous field diaphragm is displayed
clearly.
•
Recenter the luminous field diaphragm with
the adjustment screws on the condenser
carrier.
The luminous field diaphragm appears only as a
circle segment on the edge of the viewing field
due to the high magnification of the immersion
oil objective. As a result, focusing and centering
of the luminous field diaphragm must be
repeated. If necessary, the luminous field
objective should be opened slightly if the light
intensity is too small.
The luminous field diaphragm is centered when
the edge of the luminous field diaphragm is
centered or equidistant from the viewing field
edge.
•
For a sharply focused specimen, open the
sharply set luminous field diaphragm until
just above the viewing field edge.
•
You can improve the contrast of the
microscope image by slightly adjusting the
focus level of the condenser with the
condenser drive.
•
The last criteria is an equally dark
background of the eyepiece image.
•
For immersion oil objectives with an iris
diaphragm, the contrast can be further
optimized by turning the adjustment of the
iris diaphragm.
Additional information:
Darkfield specimens require a considerably
higher level of cleanliness than specimens for
other methods; fingerprints, dirt and dust in
particular brighten the background.
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