Advertisement
Substage Condenser:
Abbe type substage condenser (NA 1.25) focusable with rack and pinion mechanism
is provided. The top lens of the condenser is sealed to prevent damage from contact
with oil. The condenser is replaceable with phase turret condenser. The functions
of the condenser are to bring the light rays to a focus in the plane of the specimen
and to furnish a suitable cone of light to the objective. The diameter of the cone of
light is controlled by the iris diaphragm which provides a variable opening to fill the
back lens of the objective thereby utilizing the full resolving power of the objective.
When the objective 100xR is used, by using the
condenser focusing knob, always move the con-
denser to its highest position. The numerical
aperture 1.25 of the condenser corresponds with
the numerical aperture of the objective 100x.
To induce the full numerical aperture 1.25, it is
designed to be immersed with oil between the
top lens of condenser and the slide, without air
spacing correctly.
Care must be taken to wipe off the oil thoroughly from the condenser lens and the
slide immediately after each use. When the oil immersion objective is used, the con-
denser should always be raised to the highest position.
Iris Diaphragm:
The diaphragm is an important factor in obtaining good images. It is not intended to
control the brightness of the illumination. A large aperture transmits too much light
and creates an image with poor contrast. Smaller apertures increase contrast. To set
the proper aperture, make the aperture of the diaphragm largest and reduce until the
fine details of the specimen are imaged sharply.
Reducing the aperture increases contrast and depth of focus but it also reduces reso-
lution and introduces diffraction. The aperture must be selected for each objective:
i.e. the aperture for the 10x objective (NA 0.25) will not be the same as for the 40x
(NA 0.65), since the angle of light required is determined by the numerical aperture
of the objective. Proper adjustment of the diaphragm aperture is easily determined.
After placing an objective into the optical path and focusing, remove the eyepiece
and look through the optical tube. Observe the diaphragm through the objective,
then move the iris lever to coincide with the edge of the objective aperture.
- 7 -
Advertisement
