Aperture Diaphragm; Use Of Oil Immersion Objective - Optika B-510 Serie Manual De Instrucciones

10.11 Aperture diaphragm

• The Numerical Aperture (N.A.) value of the aperture
diaphragm affects the image contrast. Increasing or reducing
this value one can vary resolution, contrast and depth of
focus of the image.
• With low contrast specimens set the numerical aperture value
(printed on the condenser ring) to about 70%-80% of the
①
objective's N.A. (Fig. 64) If necessary, remove on eyepiece
and, looking into empty sleeve, adjust the condenser's ring in
order to obtain an image like the one in fig. 65.
Example: with objective PLAN 40x/0,65 set the scale to 0.65
x 0.8 = 0,52

10.12 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. 66)
• 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.
APERTURE
DIAPHRAGM
FIELD OF VIEW
Page 42
①
F ig. 64 F ig. 64
70-80%
30-20%
F ig. 65 F ig. 65
F ig. 66 F ig. 66