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12
Adjustment for the Episcopic Illumination
(Field Diaphragm and Aperture Diaphragm)
Field diaphragm
The field diaphragm restricts the illumination light to the
area on the specimen to be observed. The field diaphragm
open/close lever changes the opening of the field
diaphragm. Adjust the opening of the diaphragm until it
circumscribes the field of view.
If a broader area than necessary is illuminated, stray light
may enter the optical system, creating flaring, and
reducing the contrast of the optical image.
In case of photomicrography, the setting of the field
diaphragm becomes very important. Generally, the field
diaphragm should be set to an area slightly larger than the
area to be exposed on film, that is, the photographed area.
The adjustment of the field diaphragm opening should be
performed after centering the diaphragm.
Centering procedure for the field diaphragm
1
Follow the procedure described in Pages 15 and 16 for the bright-field microscopy under the
episcopic illumination, and focus on the specimen with the 10x objective.
2
Lower the field diaphragm open/close lever and reduce the opening of the field diaphragm.
3
Insert a hexagonal wrench into the field diaphragm centering holes on both sides of the LV-
UEPI2A and turn the internal adjustment screws to bring the field diaphragm image to the
center of the field of view.
4
Adjust the field diaphragm image with the field diaphragm open/close lever and centering
screws so that it inscribes the field of view.
5
To observe the specimen, raise the field diaphragm open/close lever so that the field
diaphragm image circumscribes the field of view.
Image of the
field diaphragm
Field of view of the eyepiece
Image of the field diaphragm
Field of view of the eyepiece
