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Transmitted light darklield with the LK condenser
For darkfield
investigations,
condenser
top
D
0.80 -
0.95
IS
used
when
the objecti
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
condenser
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
specimen o
n the stage.
Turn
the
condenser
stop
screw
to
the
right as far as the stop.
Insert
the
condenser and
raise
to
the
condenser
stop
.
If using
the
D 1.19
condenser
top,
first
app
ly
a drop
of imme
r
sion
oil
to the
surface
of
th
e
condenser (taking care to avoid air
bubbles) and
then
raise
until the
drop
of
oil
touches
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
co ndense
r drive
(1.8)
until
the edges
of
the diaph
ragm are as
sharp
as
possible when
the specimen
is
observed.
Move the image of the
di
aphragm
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
with annula
r
stop
slid
es
DFI
PHA CO
for
phase
contrasl
or
dark field
ill umination:
-
Centre the conden
ser
with a
brightfi eld
specimen
-
Screw in phase contrast
objectives
-
Open
the
aperture diaphragm
- Push
the
slide
with the
appropri
ate
an
nular
stop (chart on
page
16) into th
e
condenser
(Fig.
16).
The
DF
155-56
annular
st
op
slide
is also
avai
la
ble
for
co nden
ser
no.
56,
with
which
sim ple
darkfield
ill
umination can
be
obtained using Objectives from lOx
to
40x.
Fig.
16 In sertio
n
of
th
e
slide with annula
r
stop
in
to
condenser
no. 56
15
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