17
Aperture Iris Diaphragm
(Figs. 31 & 32)
Aperture iris
diaphragm image
·
The aperture iris diaphragm determines the numerical aperture of the
illumination system. It has an effect of adjusting image resolution and
contrast. Stopping down the aperture iris diaphragm increases the depth
of focus.
·
Since the contrast of microscope specimens is ordinarily low, setting the
condenser aperture iris diaphragm to between 70 and 80% of the N.A. ²
of the objective in use is usually recommended.
Adjust the ratio by removing the eyepiece and looking into the eyepiece
sleeve while adjusting the aperture iris diaphragm ring @ until the image
shown in Fig. 31 is seen.
}Using the numerical aperture scale:
You can use the condenser numerical aperture scale by adjusting the
aperture iris diaphragm ring @. (Fig. 32)
Fig. 31
Fig. 32
2
Compatibility of Objectives and Condensers
Objective
Magnification
Condenser
Abbe
U-AC2
Achromat/aplanat
U-AAC
Swing-out
U-SC3
Ultralow magnification
U-ULC-2
1.25X
Applicable to FN 22
2X
Applicable by moving
top lens out of the light
path.* (FN 26.5)
4X
Applicable to FN 22
10-60X
Applicable
(FN 26.5)
Applicable
(FN 26.5)
Engage top lens in
light path (FN 26.5)
100X
**
Applicable
(FN 26.5)
*
When using the U-SC3 swing-out condenser together with a 1.25X to 4X objective, fully open the condenser aperture iris
diaphragm and use the field iris diaphragm in the base as aperture diaphragm. With the 1.25X to 2X objectives, the
surroundings of the field of view may be dark but observation is still possible.
**
When using the U-AC2 Abbe condenser, the field iris diaphragm image cannot be viewed with a 100X objective.
}To obtain better illumination in photomicrography using a 1.25X to 4X objective, use of the U-ULC-2 is recommended.
N.A. scale
@
²
Objective pupil
70-80%
30-20%
