Chapter 3 Detailed Explanation
56
3.5 Adjustment of Aperture Diaphragm
The size of the condenser aperture diaphragm should be
adjusted according to the objective in the optical path.
A guideline for the adjustment position is shown by the
“adjustment position mark of aperture diaphragm” on the
condenser. Turn the aperture diaphragm lever to “the same
figure as the magnification of the objective” in the optical
path.
Each time you change the objective magnifications, align
the aperture diaphragm lever to the same figure as the
magnifying power of the objective.
Adjustment position mark of aperture diaphragm
Objective Color of the mark
4x Red
10x Yellow
20x Light green
40x Light blue
60x Dark blue
100x White/Black
Adjustment position mark of aperture diaphragm
Aperture diaphragm
• The aperture size is increased or decreased by turning
the condenser aperture diaphragm lever.
If the aperture diaphragm is closed, the brightness and
resolution are decreased but the contrast and range of
focus are increased. If the aperture diaphragm is
opened, the brightness and resolution are increased
but the contrast and range of focus are decreased.
Since the image resolution will be degraded when the
aperture diaphragm is closed too much, do not close
the aperture diaphragm too much except when
observing a specimen with extremely low contrast, such
as a near-transparent specimen.
• The aperture diaphragm controls the numerical
aperture of the illumination. Do not use it to control
brightness. Use the brightness control knob to control
the brightness.
BE2 PLAN → Objective type
40x/0.65 → Magnification 40 times/Numerical
aperture 0.65
∞/0.17 → Mechanical tube length ∞/Coverglass
thickness 0.17 mm
WD 0.6 → Working distance (Distance between
the front of the objective and the
specimen) 0.6 mm
OFN20 → Objective field number 20
Specifications of objective
100x 60x 40x 20x 10x 4x
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