Aperture Diaphragm; Use Of The Polarizer (Optional) - Optika B-190TB Serie Manual De Instrucciones

8.8

Aperture diaphragm

• The Numerical Aperture (N.A.) value of the ap-
erture diaphragm affects the image contrast. In-
creasing or reducing this value one can vary res-
olution, contrast and depth of focus of the image.
Move the diaphragm ring ① (Fig. 20) on the value
corresponding to the objective in use. In this case
the optimal setting of the condenser 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, look-
ing into empty sleeve, adjust the condenser's dia-
phragm in order to obtain an image like the one
in Fig. 21.
8.9

Use of the polarizer (optional)

1. Remove the specimen from the stage.
2. Looking inside the eyepieces, rotate the polarizer
until the darkest position is achieved.
3. Once the dark is achieved ("extinction" or
"Crossed Nicol" position) it is possible to begin
the observation.
①
APERTURE
DIAPHRAGM
FIELD OF VIEW
Page 13
F ig. 20 F ig. 20
70-80%
30-20%
F ig. 21 F ig. 21