Use Of Oil Immersion Objective; Aperture Diaphragm - Optika Italy B-150V Serie Manual De Instrucciones

9.5

Use of oil immersion objective

B-159R-PLV only
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. 12)
• 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).
• 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
could crystallize
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.
9.6

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
focus of the image. Move the diaphragm lever
toward left or right to decrease or increase the N.A. value.
• 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. 14.
oil, if not immediately
creating a glass-like
cleaned,
layer.
(Fig. 13)
①
APERTURE
DIAPHRAGM
Page 13
①
70-80%
FIELD OF VIEW
F F ig. 12 ig. 12
F ig. 13 F ig. 13
30-20%
F ig. 14 F ig. 14