Nikon S-kt - Page 14

(6)
Oil
lmmersion
When
using the 100X
objective,
the appli-
cation
of immersion
oil in the minute
space
(0.1-0.16mm)
between
the objec-
tive and
the
cover
glass
is necessary
to
attain
the
specified
numerical
aperture.
For critical
work immersion
oil
should
be
placed
between
the top
lens of the
condenser
and
the slide
as
well as be-
tween the
objective
and
the cover
glass.
Oil
immersion
observation
is
performed
as
follows:
First, using
a 10X
or 40X
objective
(dry
system),
focus the speci-
men and center
it in the
viewfield. Set
the
preset
lever by
turning clockwise.
Lower
the
microscope
stage
and
revolve
the
nosepiece
revolver to
the
'100X
objective.
After
applying
a
drop
of immersion
oil
onto
the cover
glass,
raise the stage
to the
preset
limit.
Then
focus
by
looking
through
the eyepiece
and
raising the stage
carefully
by
manipulating
the
fine
focus
knob. The
oil immersion
100X
objective
is designed
to attain
its
critical
focus by
about
1/3
forward
rotation
of the
fine
focus
knob, that is, by bringing
the stage
about
0.08mm
closer
to the
objective
from the
parfocal position.
Air
bubbles
in
the
immersion
oil,
which may sometimes
spoil
the
microscope
image
and are
visible
when
looking
into the
microscope
tube
without
the
eyepiece,
can be
removed
by
repeating
slight
movements
of the nose-
piece
or by adding
a certain
quantity
of
immersion
oil or bv
means of a
needle.
Unremoved
hardened
oil may often
impair the image.
Therefore,
immediately
after
finishing the work,
remove
the
remaining oil
from the lens
using a soft
cotton
cloth
moistened
with xylol. Never
use
alcohol
or immerse the
front
of the
objective
in xylol.
Be careful
not to
use immersion
oil that
has
been
aged and
thickened.
The refractive
index of the
immersion
oil
should
be 1.515.
(7)
Exchanging Stages
Lower the stage
by
means of the
coarse
focus
knob
and
unlock
the
stage
lock
screw.
The stage
can
then be
removed.
l
15