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5
Focusing and Centering the Condenser
Adjust the condenser position so that the light passing through the condenser forms an image at the correct position
(center of the optical path) on the surface of the specimen.
(1)
Follow Steps 1 through 9 in Chapter 1 "1.2 Bright-field
Microscopy Procedure" to focus on the specimen using the
10x objective.
(2)
Turn the field diaphragm dial counterclockwise fully to
minimize the field diaphragm.
(3)
You can see the diaphragm image in the field of view as you
look into the eyepiece. Use the condenser focus knob to
adjust so that the field diaphragm image can be outlined
clearly.
(4)
Adjust the condenser centering screws until the field
diaphragm image is at the center of the eyepiece field of
view.
(5)
Set the 40x objective into the optical path. Bring the 40x
objective into the optical path. As you see the field diaphragm
image, if the outline of the image is out of focus, use the
condenser focus knob to adjust the focus as much as
possible.
(6)
Turn the field diaphragm dial to adjust so that the field
diaphragm image size is almost the same as the field of view.
(7)
If the center of the field diaphragm image is not centered,
turn the condenser centering screws to move the field
diaphragm image to the center of the field of view. This is
easiest if you adjust the field diaphragm aperture so that it is
slightly smaller than the eyepiece field of view.
Correct focusing of the field diaphragm image
If the outline of the field diaphragm image is reddish or
Chap. 2
bluish, you have turned the condenser focus knob too
much. When the outline is colorless, focusing is correct.
Field diaphragm image view with the 40x
objective
The field diaphragm image that has been focused with the
40x objective can not be seen so clearly as the one focused
with the 10x objective.
Chapter 2
Individual Operations
Field diaphragm
image
Eyepiece field ring
Focusing and centering the condenser
46
0.9
0.8
0.5
0.4
0.3
0.2
0.1
(2)
Minimize the field
diaphragm.
0.9
0.8
0.7
0.2
0.6
0.4
0.3
(4)
Field diaphragm image
centered at the field of view
0.9
0.8
0.5
0.4
0.3
0.2
0.1
(7)
Field
diaphragm
image
centered at
the field of
(6)
view
Open the field
diaphragm up to the
size of the field of view.
(3)
Focus the
field
diaphragm
image at 10x.
0.1
(5)
Focus the
field
diaphragm
accurately at
40x.
Field diaphragm
image
Eyepiece field ring
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