3032
4-4 Illumination Unit
4-4-2 Using the Aperture Diaphragm
（
（
（
（
Figure 25
）
）
）
）
●
When using bright field observation, the aperture diaphragm is used to control the numerical
aperture of the illumination system not the brightness. Only when the numerical apertures of the
objective and the illumination system are equal can higher image resolution, contrast, and
increased depth of field be obtained.
●
Generally, when observing the chromatic specimens, the N.A. of the condenser aperture diaphragm
is adjusted to 70-80% of the numerical aperture marked on the objective.
To adjust the aperture diaphragm, remove the eyepiece then looked into the viewing tube. Your field of
view will appear as Figure 25. The proportion may be changed by turning the aperture adjustment
lever: (
①
is the image of the aperture diaphragm &
②
is the edge of the objective).
4-4-1
Using Color Filters
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（
（
（
Figure 24
）
）
）
）
Select the appropriate color filter according to the
type of illumination being used. Insert the filter
into the filter holder.
The filter holder can hold multiple filters up to a
total thickness of 11mm or less.
Color
Filter
Usage in Microscopy
IF550
Green Filter
use for phase contrast microscopy
LBD
Blue Filter
use for bright field observation and
microphotography
12
Figure 24
Figure 25
1
2
70-80%
30-20%
