Optika Italy B-380 Serie Manuel D'instructions page 21

10.7.2 Centering with field diaphragm
1. Put the specimen on the stage, insert 10X objective and fo-
cus the specimen.
2. Rotate the field diaphragm ring
phragm. (Fig. 17)
3. Rotate the height adjustment knob
the diaphragm.
4. Rotate the centering screws
age into the center of the field of view.
5. Gradually open the diaphragm. The condenser is centered
when the diaphragm's image is symmetrical to the edges of
the field of view.
6. In the normal use, open the diaphragm until it circumscribes
the field of view.
10.8 Effects of the field diaphragm
Field diaphragm adjusts the illuminated area to obtain a high
contrast image.
Set the diaphragm according to the objective in use until it cir-
cumscribes the field of view, in order to eliminate unnecessary
light to eyepieces. (Fig. 18)
10.9 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.
• Move the diaphragm ring
sponding to the objective in use. In this case the optimal set-
ting of the condenser is achieved. It is possible, however,
move the ring to lower or higher values to adapt the observa-
tion to personal preferences.
• 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. 20.
to fully close the dia-
①
to focus the edges of
②
to bring the diaphragm's im-
③
(Fig. 19) on the value corre-
①
②
①
APERTURE
DIAPHRAGM
FIELD OF VIEW
Page 21
③
F ig. 19 F
70-80%
30-20%
①
F ig. 17 F ig. 17
F ig. 18 F ig. 18
ig. 19
F ig. 20 F ig. 20