Adjusting The Aperture Diaphragm - Nikon eclipse e100 Instructions Manual

The aperture size is increased or decreased by rotating the condenser aperture diaphragm lever.
If the aperture diaphragm is closed, the brightness and resolution are decreased but the contrast
and range of focus are increased. If the aperture diaphragm is opened, the brightness and
resolution are increased but the contrast and range of focus are decreased.
Generally, a good image of sufficient contrast can be achieved with the aperture diaphragm closed
to approximately 70% - 80% of the objective's numerical aperture. Since the image resolution will
be degraded when the aperture diaphragm is closed too much, do not close the aperture
diaphragm to less than 60% of the objective's numerical aperture except when observing a
specimen with low contrast, such as a near-transparent specimen.
The aperture diaphragm controls the numerical aperture of the illumination. Do not use it to control
brightness. Use the brightness control dial to control the brightness.
• The objective's numerical aperture is indicated on the side of the objective.
40x / 0.65 = magnifying power 40x, numerical aperture 0.65
• To observe the diaphragm image, remove the eyepiece and look down the open tube.
(The eyepiece is fastened to the eyepiece tube. Loosen the screw before removing the
eyepiece.)
• The figures on the condenser show the approximate positions of the aperture
diaphragm lever corresponding to each objective magnification. (When the aperture
diaphragm lever is moved to that position, the size of the aperture diaphragm will be
70% - 80% of the objective's numerical aperture.) Each time you switch the objective,
align the aperture diaphragm lever to the same figure as the magnifying power of the
objective to get a good image with sufficient contrast.
70 80%
100%
The appropriate size of the aperture diaphragm
20

Adjusting the Aperture Diaphragm

Aperture diaphragm lever
Objective pupil
Aperture diaphragm image
Magnifying power: 40x
Numerical aperture: 0.65
Corresponding objective magnification