4
7.
Adjusting the aperture diaphragm and condenser
The aperture diaphragm decides the numerical aperture (N.A.) of the illumination system. If the N.A.
of the illumination system matches with the NA of the objective, it can obtain better resolution and
contrast and increase the depth of field.
a.
You can adjust the condenser adjustment knob by turning it towards you. Raise the condener
towards the slide on the stage to fill the field of view with more light or turn the knob away
from you to lower the condenser and fill less of the field of view with light. Since natural light
to your specimen is usually low, it is a good idea to adjust the condenser aperture diaphragm
to be 70-80% of the NA of the objective. Adjust the aperture adjustment lever to allow the
correct amount of light through. A good rule of thumb is when using the 4x objective move
the lever all the way to the right (open), and when using the 100x objective move the lever all
the way to the left (closed). For the objectives in between adjust the lever betwen these
settings.
8.
Using the oil immersion objective
a.
First, use the 4x objective to focus the specimen.
b.
Place a drop of oil on the specimen.
c.
Rotate the nosepiece counterclockwise and rotate the oil objective (100x) into the light path.
Then use the fine focusing knob to focus the specimen.
**Make sure there are no air bubbles in the oil. Air bubbles will distort the image. If you do
experience an air bubble, you can gently swing the oil objective a few times to remove the
bubble.
d.
After use, wipe the lens with a tissue moistened with lens cleaner. Make sure all excess oil is
removed from the objective after use.
Left over oil can damage the objective if not properly
removed.
9.
Use of colored filters
Swing out the colored filter holder at the bottom of the condenser
(1) in a clockwise direction. Place the filter (2) into the hole and
then replace the holder.
10.
Replacing
the
Fuse
Turn the main switch to OFF before replacing the fuse. Pull out
the power cord. Pull the fuse base until the fuse can be
removed from the fuse base. Install new fuse and push it into the
fuse
base
firmly.
