Chapter 3 Operation of Each Part
5 LWD Condenser
24
4
Place an objective of 40x or 80x into the optical
path. Rotate the parfocal correction knob on the
sliding nosepiece to focus on the specimen.
5
Turn the condenser focus knob to form the field diaphragm image on the specimen surface.
6
Turn the condenser centering screws so that the field diaphragm image is positioned in the
center of the view field. This is easiest if you set the field diaphragm aperture to slightly
smaller than the eyepiece view field.
5.2
Adjusting the Condenser Aperture Diaphragm
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 lever on the LWD condenser 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.
Example: when the numerical aperture of an objective is
0.80,
0.8 x 0.7 to 0.8 = 0.56 to 0.64
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.
40
X/0.80W
DIC M
Fluor
/0 WD 2.0
Fluor
40x / 0.80 W
/0 WD 2.0
DIC M
"40x/ 0.80" means that the
magnification is x40 and the
numerical aperture is 0.80.
Condenser aperture
diaphragm lever
Field diaphragm image
Eyepiece viewfield
Field diaphragm image
Eyepiece viewfield
Parfocal
correction
knobs
Near side
objective
Far side
objective
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