9
Fig. 3
3
Centering the Aperture Iris Diaphragm (AS)
(Fig. 3)
1. Slide the mirror selector lever @ to “BF”.
2. Engage the 10X objective by rotating the revolving nosepiece and bring
the specimen in approximate focus.
3. Remove the eyepiece, look into the eyepiece sleeve and pull the AS knob
² so that the aperture is about 70%.
4. If the center of the iris diaphragm is deviated, center it by rotating the two
AS centering screws ³ using the Allen screwdriver.
Using the Aperture Iris Diaphragm
{In
reflected light brightfield observation,
optimum observation is gener-
ally possible by setting the aperture to between 70% and 80% of the
aperture number of the objective.
{In
reflected right darkfield observation,
the aperture must be fully opened
by pushing in the AS knob ².
}With some specimens, an image with high contrast and little flare may
sometimes obtained when the aperture is slightly closed. It is therefore
recommended to also try a slightly closed aperture.
70%
@
|
30%
Aperture iris diaphragm image
³
²
