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8.7 Use of oil immersion objective
• OS-B / OS-C Series
1.
Focus the specimen with a low power objective.
2.
Lower the stage.
3.
Put a drop of oil (provided) on the area of the specimen to be
observed. (Fig. 20)
• Make sure that there are no oil bubbles. Air bubbles in
the oil damage the image quality
.
•
To check for bubbles: remove an eyepiece, fully open the ap
-
erture diaphragm and observe the objective exit pupil. (The
pupil must be circular and bright).
4.
Insert immersion objective.
5.
Return the stage to the upper focusing point and obtain an
optimal focus using the fine focus knob.
•
To remove the air bubbles, gently move the nosepiece to the
right and left to move the immersion objective a few times
and allow the air bubbles to move away.
6.
After use, gently remove the oil with a soft paper towel or a
lightly moistened optic paper with a mixture of ethyl ether
(70%) and absolute ethyl alcohol (30%).
• The immersion oil, if not immediately cleaned, could
crystallize creating a glass-like layer.
• In this situation the observation of the specimen would
be difficult (even not impossible) due to the presence of
an additional thickness on the objective.
F
Fig. 20
ig. 20
F
Fig. 21
ig. 21
8.8 Condenser centering (OS-B Series only)
1.
Focus the specimen with 4x objective.
2.
Fully close the aperture diaphragm by rotating the ring
①
.
(Fig. 21)
3.
If the condenser is not perfectly centered, move the screws
②
until the diaphragm image is in the center of the field of
view.
4.
Fully open the diaphragm.
8.9 Aperture diaphragm
•
The Numerical Aperture (N.A.) value of the aperture dia
-
phragm affects the image contrast. Increasing or reducing
this value one can vary resolution, contrast and depth of fo
-
cus of the image. Rotate the diaphragm ring toward left or
right until a good contrast is achieved.
•
With low contrast specimens set the numerical aperture to
about 70%-80% of the objective’s N.A. If necessary, remove
on eyepiece and, looking into empty sleeve, adjust the con
-
denser’s diaphragm in order to obtain an image like the one
in Fig. 22.
①
②
②
F
Fig. 22
ig. 22
APERTURE
DIAPHRAGM
FIELD OF VIEW
30-20%
70-80%