Adjusting The Aperture Diaphragm; For The Bright-Field Microscopy And The Orthoscopic Microscopy - Nikon Eclipse 50i POL Instruction Manual

Adjusting the Aperture Diaphragm

3.9
The aperture diaphragm for the diascopic microscopy is adjusted with the condenser aperture
diaphragm knob.
For the diaphragms of the epi illuminator, refer to "3.17 Episcopic microscopy."

For the Bright-field Microscopy and the Orthoscopic Microscopy

3.9.1
The numerical aperture for the condenser can be read with the scale on it. You can adjust the
numerical aperture with the scale. For the bright-field microscopy and the orthoscopic
microscopy, set the index of the aperture diaphragm to the point between 70% and 80% of the
numerical aperture of the objective in normal cases. The numerical aperture of the objective is
labeled on its side.
Numerical aperture
40
0.65 x 0.7 ~ 0.8 = 0.455 ~ 0.52
The aperture diaphragm is important because it is related to the resolution, contrast, depth of
focus and brightness of the optical image. Turning the condenser aperture diaphragm ring
changes the size of the aperture diaphragm.
As the aperture diaphragm is stopped down, resolution and brightness are reduced while
contrast and depth of focus are increased. Conversely, as the aperture diaphragm is opened,
resolution and brightness are increased while contrast and depth of focus are reduced. It is not
possible to adjust one pair of characteristics without affecting the other. Generally, a satisfactory
image with appropriate contrast can be obtained with an aperture setting that is 70% to 80% of
the numerical aperture of the objective. The numerical aperture is indicated on the barrel of each
objective.
An indication of 40×/0.65 means that the magnification is 40× and the numerical
aperture is 0.65.
If the aperture diaphragm is stopped down too far, the resolution is reduced; therefore, except
when viewing a nearly transparent specimen, we do not recommend stopping down the aperture
to less than 60% of the numerical aperture of the objective.
Adjusting the size of the aperture diaphragm according to the condenser scale
Since the condenser scale indicates the numerical aperture, adjust the aperture diaphragm ring
according to the scale. (Normally, the index on the aperture diaphragm ring should be aligned
with the scale line corresponding to 70% to 80% of the numerical aperture of the objective.)
Adjusting the size of the aperture diaphragm using the Bertrand lens
Insert the Bertrand lens into the optical path (by placing in position "B"). Turn the diaphragm
control ring to stop down the aperture diaphragm to its minimum setting. Turn the Bertrand lens
focus ring to focus on the aperture diaphragm image. Turn the diaphragm control ring to adjust
the aperture diaphragm. (This is normally adjusted to 70-80% of the view field.)
Chapter 3 Individual Operations
3.9 Adjusting the Aperture Diaphragm
Objective
X/ 0.65
P
/0.17 WD 0.65
40x
40
X/0.65
P
/0.17 WD 0.65
39
Condenser
aperture
diaphragm
knob