3. Measurement setup
No. 99MBA091A
3-5
3.5 Adjusting the Aperture for Reflected Illumination
The aperture diaphragm for vertical reflected illumination is used to adjust the Numerical
Aperture (N.A) of vertical reflected illumination system. It controls the resolution, contrast,
and depth of focus of the optical system.
Confirm that the exit pupil of objective as above can be seen by removing the eyepiece
and looking into the optical tube with an appropriate light intensity. Push and pull a knob of
aperture diaphragm to adjust the numerical aperture.
NOTE
Do not set the aperture diaphragm less than 60% of the exit pupil radius except
for special types of workpieces. This will reduce the resolution.
Aperture setting for obtaining a
good contrast and image clarity
for ordinary applications:
70 to 80％ of radius
Aperture diaphragm
Exit pupil of objective
Iris
Reflected illumination
aperture diaphragm knob
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