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Home Training Tools Ltd. 2005
Page 5 of 8
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100x Objective
suggested opening sizes for each power
level:
Objective Diaphragm
Opening
4x
From fully closed to 1/8 open
10x
1/8 to 1/4 open
40x
1/4 to 1/2 open
Note: One method for finding the most suitable
iris diaphragm opening is to remove the
eyepiece, put your eye up to the eyepiece tube,
and look at the bright circle of the aperture.
Close the iris diaphragm until you see its
outline in the aperture. Adjust it so that its
silhouette takes up 10-15% of the edge of the
aperture. Replace the eyepiece. The contrast
and resolution should be nicely balanced on
your specimen. If necessary, make further
minor adjustments to the diaphragm while
looking at the specimen.
Setting the Field Diaphragm
Even though your slide specimen is now in
focus on the lowest power, you are not seeing
the best image your microscope can give you.
The following steps describe how to adjust your
field diaphragm to set up the light path that will
give you the sharpest image contrast. Once it is
set, you should be able to control your contrast
and resolution using just the iris diaphragm. Set
your field diaphragm again only when you feel
the contrast isn’t as sharp as it should be.
1.
Focus a slide at the lowest power (40x).
2.
Open the field diaphragm all the way by
turning it clockwise.
3.
Open the iris diaphragm all the way by
rotating it clockwise.
4.
Start to close the field diaphragm by turning
it counter-clockwise. At the same time, use
the condenser knob to move the condenser
up and down until the dark edge of the field
diaphragm appears focused sharply.
5.
Once the silhouette of the field diaphragm is
sharply defined, center it using the
condenser centering knobs (closing the field
diaphragm further will help you center it).
6.
Open the field diaphragm until its edge
disappears beyond the outside of the field.
7.
Now that your field diaphragm is set, you
can turn up the light using the illumination
intensity control.
Changing Magnification
1.
Use the stage controls to scan the slide
(right to left and front to back) at low power
to get an overview of the specimen. Then
center the part of the specimen you want to
view at higher power.
2.
Rotate the nosepiece to the 10x for 100x
magnification (make sure it “clicks” into
place). Refocus using the fine focus knob
and view your specimen carefully. Adjust the
iris diaphragm again until the image is most
clear. Repeat with the 40x objective for 400x
magnification.
Using the 100x Oil Immersion Objective
When using the 100x oil
immersion objective, it is
important to reduce light
diffraction to enhance the image
quality. This is done by using
immersion oil according to the
following steps:
1.
Lower the stage using
the coarse focus knob.
2.
Raise the Abbe condenser to the upright
position by turning the condenser knob.
Open the iris diaphragm by rotating it
clockwise.
3.
Place one drop of high quality immersion oil
(our item MI-IMMOIL) on top of the
coverslip. (In some cases, it may be
beneficial to place a drop of oil between the
condenser and the slide also, but this is
usually not necessary for a good image.)
4.
Move the 100x objective lens until it clicks
into position, and then slowly move the
stage up until the lens makes contact with
the oil.
5.
Continue focusing with the coarse knob until
the color or blurred outline of the specimen
appears. Finish focusing with the fine focus
knob. Adjust the condenser and diaphragm
until you see the specimen in clear, sharp
contrast.
6.
When you are done, clean all the oil off the
lenses and slides using lens paper and lens
cleaning solution (instructions are on page 2
of this manual).
