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2. Change the distance between the eyepieces by pushing them together or pulling apart until a cir-
cular image of the obeserved object is visible.
17 Diopter adjustment
1. Turn the diopter adjustment ring to position '0'.
2. With the left eye, look through the left eyepiece and turn the focusing wheel until a sharp image of
the observed object is visible.
3. With the right eye, look through the right eyepiece and turn the diopter adjustment ring until a
sharp image of the observed object is visible too.
The diopter adjustment can also be done in the opposite way on the left eyepiece.
18 Using the iris diaphragm
NOTICE
The iris diaphragm is used to increase the depth of focus.
With an open aperture more light is getting through but the depth of focus is less. With partially closed
aperture the depth of focus is higher but it is neccessary to increase the brightness of the illumination
then.
It is recommended not to close the iris diaphragm too much when working with higher magnifications.
Otherwise the image resolution will decrease.
Move the lever for the iris diaphragm to right or left to change the aperture setting.
19 Using the Köhler illumination
Proceed as follows to adjust the Köhler illumination for an optimal illumination of the field of view:
1. Focus on the object with the 10x objective.
2. Close the condensor and the light field aperture. For microscopes with additional lens, fold it out.
3. Move the condensor up and down until the edge of the light field aperture is in focus.
4. If neccessary, use the adjustment screws to move the condensor until the light field aperture is
centered in the field of view.
5. Open the light field aperture as far as it is not visible in the field of view anymore.
20 Oil immersion
The oil immersion can be done with a suitable 100x objective only. For the purpose proceed as fol-
lows:
1. Focus on the object with the 40x objective.
2. Turn the 40x objective sideways.
3. Drop a drop of immersion oil onto the cover glass of the preparation.
4. Retract the 100x objective so that it is immersed in the oil.
5. Refocus the image.
6. Clean the 100x objective after each use.
