Transmitted light darklield with the
LK
condenser
For
darkfield investigation
s,
condenser
top D 0.80 -
0.95
IS
used when the objec
ti
ve has an aperture
of
less than
0.75
and
condenser
top D
1.19
-
1.44
when the objective's aperture is lar-
ger than
0.75
.
For apertures greater than l.ID, insert a
funnel
stop
into the oil
immersion
objective or use an objective with buill-in iris
diaphragm. Separate bottom parts are also available for
the
darkfield
con
denser
tops, which are pushed into the
condenser
mount
instead
of
the brigblfield or phase contrast condensers.
Focusing tbe darklield image (D
1.19
-1.44 and D 0.80 - 0.95)
Put a s
pecim
en
on the stage. Turn the
condenser
stop screw to
the right as far as the stop. Inse
rt
th
e
condenser
and raise
to
the
condenser stop .
If
using the D
1.19
condenser top, first app
ly
a drop
of
imm
e
r-
sion
oil to the surface
of
the
condenser
(taking care to avoid air
bubbles) and then raise until the drop
of
oil touc
he
s the under-
neath
of
the specimen slid
e.
This can be seen
by
a brief lighting
up
of
the slide.
Bring the specimen inlo focus. (Use Ihe
10
/0.
25
or
16/0.40
objective). Close the field diaphragm. Raise
or
lower the con-
denser
by
adjusting the condenser slop screw (
1.10)
to
the
left
and using the condenser drive
(1.8)
until the edges
of
the
diaph-
ragm
are
as
s
harp
as
possible
when
the
specimen
is
obs
erve
d.
Move the image
of
the
di
a
phr
agm into the centre
of
the
field
of
view with
the
tw
o centring screws
(1.11).
Open
Ihe field diaphragm until
it
just disappears from the field
of
view.
Phase contrast or darkfield illumination with condenser
00.
56
Condenser
no.
56
can be
fi
tted
wi
th
annular stop slides
DF
I
PHACO for
ph
ase contrasl
or
dark field
ill
umination:
-
Centre
the condenser with a brightfie
ld
spe
cimen
- Screw in phase contrast objectives
- Open the aperture diaphragm
- Push the slide with the appropriate an nular stop (chart on
page
16)
into the condenser (Fig.
16).
The
DF
155-56
annular
st
op slide
is
also av
ai
lable for conden-
ser no. 56, with which simple darkfield i
ll
umination can be
obtained using Objectives from
lOx
to 40x.
Fig
.
16
In
sertion
of
th
e sli
de
with annular stop
in
to condenser no.
56
15
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