Nikon ECLIPSE MA200 - Adjusting the Field Diaphragm (for the Episcopic Illumination)

Chapter 3 Operation Details
41
3.11 Adjusting the Field Diaphragm (for the episcopic Illumination)
Figure 3.11-1 Field Diaphragm Adjustment
The field diaphragm is used to limit the irradiation
area of the lamp to the view-field of the microscope.
The field diaphragm dial (F. S.) changes the opening
of the field diaphragm. Normally, stop down the field
diaphragm to a size that circumscribes (or inscribes)
the view-field. An unnecessarily large irradiation area
will result in stray light and flare, thereby reducing the
contrast of the optical image. For photomicroscopy,
the field diaphragm should be stopped down to a size
slightly larger than the area to be captured. Avoid
stopping down the field diaphragm too close to the
frame size to be captured, as it may result in
vignetting.
* The adjustment of the field diaphragm opening
should be performed after centering the
diaphragm.
■ Centering procedure for the field diaphragm
Figure 3.11-2 Centering the field diaphragm
1 Follow the procedure described in “2.1 Bright-field
Microscopy under the Episcopic Illumination,” and
focus on the sample with the 10X objective.
2 Stop down the field diaphragm by turning the field
diaphragm dial.
3 Insert hexagonal screwdrivers into the field
diaphragm centering holes and turn the internal
adjustment screws to bring the field diaphragm
image to the center of the view-field.
4 Adjust the field diaphragm image with the field
diaphragm dial and centering screws so that it
inscribes the view-field.
5 To observe the sample, turn the field diaphragm
dial so that the field diaphragm image
circumscribes the view-field.
Field diaphragm
centering holes
Image of the field
diaphragm
Vie
w
-field of the
eyepiece
Field diaphragm knob
Image of the field diaphragm
Vie
w
-field of the eyepiece