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III. Operation of Each Part
For the Bright-field Microscopy and the Orthoscopic Microscopy
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.
The numerical aperture for the condenser can be read with the scale on it. You can adjust the
numerical aperture with the scale. To perform the bright-field microscopy or the orthoscopic
microscopy, 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 40x/0.65 means that the magnification is 40x and the numerical
aperture is 0.65.
0.65 x 0.7 to 0.8 = 0.455 to 0.52
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.)
For the conoscopic microscopy
For the conoscopic microscopy, the condenser aperture diaphragm functions as a field diaphragm
on the conoscopic image surface. Stop down the diaphragm until it circumscribes the circumference
of the view field of the conoscopic image (pupil of the objective).
40
X/0.65
P
40x
/0.17 WD 0.65
40
X/ 0.65
P
/0.17 WD 0.65
Numerical aperture
EPI/DIA
OFF
0.6
0.8
0.2
0.4
JAP
AN
Achr
0.90
CLICK
ON
0
Condenser
aperture
diaphragm ring
