Transmitted Light - Leica DMi1 Instructions For Use Manual

8. Operation

8.3 Transmitted light

Bright field illumination
Illumination methods in which the empty areas of
the specimen make up the brightest areas of the
image are called bright field. Bright field obser-
vation requires absorbent specimen structures,
i.e. most specimens will need specimen staining.
Alternatives are optical contrast methods such
as phase contrast.
Adjusting the condenser
For correct height adjustment of the S80/0.30
and S40/0.45 condensers, the stand has marks
(Fig. 25.3). The marks indicate the 40mm to 50 mm
working distance position for S40 condenser and
S80 position for S80 condenser.
For S40 condenser, the condenser can move from
40 mm to 50 mm to achieve different working dis-
tance. And can stop in any where between.
For S80 condenser the also have on mark indi-
cated the fix position for S80.
For 40mm, 50mm and 80 mm position, when it fix
into the right position, a "click" will be heard.
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Adjusting the aperture diaphragm
The aperture diaphragm (Fig. 25.5) determines
the resolution, the focus depth and the contrast
of the microscope image. The best resolution is
obtained when the apertures of the objective and
the condenser are roughly the same.
When the aperture diaphragm is stopped down
to be smaller than the objective aperture, reso-
lution is reduced, but the contrast is enhanced.
A noticeable reduction in the resolution is ob-
served when the aperture diaphragm is stopped
down to less than 0.6x of the objective aperture
and should be avoided where possible.
Fig. 25 Transmitted light illumination unit with condenser
1 Condenser
2 Condenser holder
3 Stop screw for condenser height adjustment
4 Marks
5 Aperture diaphragm
4
5
2
1
3