Adjusting The Aperture Diaphragm (For The Episcopic Illumination) - Nikon ECLIPSE MA200 Instructions Manual

3.12

Adjusting the Aperture Diaphragm (for the episcopic illumination)

Aperture
diaphragm
Aperture
diaphragm dial
Figure 3.12-1 Aperture diaphragm adjustment
■
Centering procedure for the aperture diaphragm
Image of aperture diaphragm
Objective pupil
Figure 3.12-2 Centering the aperture diaphragm
Chapter 3 Operation Details
Objective pupil
Aperture diaphragm
centering holes
The aperture diaphragm controls the numerical
aperture of the illumination system, and is closely
related to the resolution of the optical image, the
brightness, the contrast and the depth of focus.
When the size of the aperture diaphragm is stopped
down, the resolution and the brightness are reduced
while the contrast and the depth of focus are
increased. However, when the size of the aperture
diaphragm is increased, the resolution and the
brightness are increased while the contrast and the
depth of focus are reduced.
The resolution, the brightness, the contrast and the
depth of focus are related to one another and cannot
be changed independently. Set the conditions to fit
the requirements of the sample and the intended
application.
The aperture diaphragm is adjusted by operating the
aperture diaphragm dial (A.S.) on the front of the
microscope. Adjust the aperture diaphragm properly
according to the procedure below. Normally, the
aperture diaphragm should be adjusted to about 70 to
80% of the numerical aperture of the objective.
When the reflectance of the sample is low, the
diaphragm image may not be seen. In this case,
change to a sample of a near-polished surface.
1 Follow the procedure described in "2.1 Bright-field
Microscopy under the Episcopic Illumination," and
focus on the sample with the 10X objective.
2 Remove one eyepiece to look into the eyepiece
tube to check that the aperture diaphragm image
is seen in the objective pupil in the eyepiece tube.
3 Stop down the aperture diaphragm by turning the
aperture diaphragm dial.
4 Insert hexagonal screwdrivers into the aperture
diaphragm centering holes and turn the internal
adjustment screws to bring the aperture
diaphragm image to the pupil center of the
objective.
5 Operate the aperture diaphragm dial and the
centering screws so that the aperture diaphragm
image inscribes the objective pupil.
6 When starting observation, adjust the aperture
diaphragm dial so that the aperture diaphragm
image becomes 70 to 80% of the numerical
aperture of the objective. (Perform this adjustment
for each objective.)
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