38
4. Fit the Allen screwdrivers provided with the microscope frame into the
two field iris diaphragm centering screws ³ and adjust them so that the
field iris image of the diaphragm is centered on the field of view.
5. To check centering, enlarge the diaphragm by pushing in the field iris
diaphragm knob ² until the diaphragm image touches the perimeter of
the field of view. If the image is not centered precisely, center it again.
6. Further enlarge the iris diaphragm until its image just circumscribes the
field of view.
Fig. 21
Effects of Field Iris Diaphragm
{Reflected light brightfield, DIC and simplified polarized light obser-
vations:
To obtain good image contrast, adjust the diameter of the illuminating
beam in accordance with the objective in use.
Using the field iris diaphragm knob ² on the reflected illuminator, adjust
the diaphragm so that the field of view is circumscribed by the field iris
diaphragm in order to exclude stray light.
{Reflected light darkfield observation:
Always keep the field iris diaphragm knob ² pushed in to leave the
diaphragm open.
2 Centering the Aperture Iris Diaphragm
(Fig. 21)
1. Engage the mirror unit (BF) in the light path by turning the turret, then
open the shutter @.
2. Rotate the revolving nosepiece to engage the 10X objective, then place
a highly flat specimen such as a mirror on the stage, and bring the
image into approximate focus.
3 Remove the eyepiece. While looking into the eyepiece sleeves, pull out
the aperture iris diaphragm knob ² so that the aperture iris image can
be seen in the field.
4. Fit the Allen screwdrivers provided with the microscope frame into the
two aperture iris diaphragm centering screws ³ and adjust them so that
the aperture iris image of the diaphragm is centered on the field of view.
Effects of Aperture Iris Diaphragm
{Reflected light brightfield observation:
In general, favorable observation is possible by setting the aperture iris of
the illumination system to 70% to 80% of the N.A. of the objective.
#The effects of aperture iris diaphragm cannot be obtained with 150X
and 250X objectives.
{Reflected light darkfield observation:
Always keep the aperture iris diaphragm knob ² pushed in to leave the
diaphragm open.
}With certain specimens, smaller aperture may sometimes offer images
with better contrast and smaller flare. Please also try such a setting.
@
²
³
70-80%
30-20%
Field iris image
Eyepiece’s field of view
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