Chapter 3 Individual Operations
117
Individual
Operations
15
Dark-field Microscopy
While the dark-field microscopy procedures provided in Chapter 2 uses a motorized universal condenser, dark-field
microscopy can also be conducted using a dark-field condenser (dry or oil).
Note the following when using these condensers for dark-field microscopy.
Using a dark-field condenser (dry or oil)
Focus and center a dark-field condenser as described below.
(1) Prepare a temporary specimen for adjustment.
A uniformly distributed pathologic section is ideal. (If
unavailable, draw a 3 mm-wide line on a glass slide with a
wax pencil or a permanent marker to make a uniform
surface.)
(2) In the microscopy preparation phase, place the temporary
specimen onto the stage, and focus on it with the 10x
objective.
(3) Move the ND filter out of the optical path. (Switch to “OUT”.)
(4) Turn the condenser focus knob until the condenser reaches
the top.
Preparing a temporary specimen
Oil immersion of a condenser
When using a dark-field condenser (oil), apply immersion
oil between the slide glass and the condenser lens. (See
“14 Oil/Water Immersion”.)
(5) Turn the condenser focus knob slowly to lower the condenser lens until a dark shadow appears near the center of the
field of view.
(6) Using the condenser centering screws, move the dark shadow to the center of the field of view.
(7) Raise the condenser and adjust for uniform brightness within the field of view.
Turn the condenser focus knob in the direction for lifting the condenser until the unevenness in the brightness of the
field of view starts to become unnoticeable. Make fine adjustments to achieve greatest uniformity.
Using a thick sample
For most cases, condenser focus knob adjustment is not required in the dark-field microscopy procedures after 7
above. However, you may need to make fine adjustments when increasing the objective's magnification while
observing a thick sample.
Objectives
When using a dark-field condenser (oil), objectives that have a greater numerical aperture than the condenser must be
used together with a “diaphragmed” objective.
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