10.11 Use of oil immersion objective
1. Focus the specimen with a low power objective.
2. Lower the stage (remembering to lock the coarse upper limit
lever).
3. Put a drop of oil (provided) on the area of the specimen to be
observed. (Fig. 27)
•
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
aperture diaphragm and observe the objective exit pupil.
(The pupil must be round and bright).
•
To remove the 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.
4. Insert immersion objective.
5. Return the stage to the upper focusing point and obtain an
optimal focus using the fine focus knob.
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 if
not impossible due to the presence of an additional
thickness on the objective.
Page 17
F ig. 27
F
ig. 27