Olympus VANOX Manuel d'instruction - Page 20
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D.
Operation of
the Auxiliary Lens System
-
1
The auxiliary lens system helps in achieving perfect
Koehfer illumination
at
all magnifications by manip-
0 -
#
ulation of the auxiliary lens system
@
, the frosted
glass
@ ,
and the swing-out auxiliary lens
@
,
@
_
-
-z+-mflv
eL-
"
+
respectively, Lens man ipu lat~on is achieved by means
6
of levers or knobs as shown in the photograph.
/ @
(Fig.
13) The
correct lens positions for various
objective powers
are
summarized in the following:
F i g .
13
Condenser
Frosted
Glass
Lever
Objective
Auxiliary
( I nser-
Position
Lens
tion
in70
Magnif i-
Achromatic/-
Low
of Swing-
'
cation
System
or remov-
out
Aplanatic
power
I
N.A.
1.4
al from
Auxiliary
I
Light
Lens
I
Path)
-
-
-
-
-
-
I) I
4X
1
ox
VERTICAL
40X
1 OOX
*
The objectives
1.3X
and 2X and the low power condenser
are
optional
accessories
.
Principle of Kaehler
Illumination
Koehler illumination may
be
described as follows: "If an image
of
a
light source i s conjugate
with the rear
focal plane of an objective
and
the
field
iris diaphragm
of the light source
is conjugate with the field
ef view of the objective/eyepiece combination, maximum light
intensity of the light source
is obtained
and
the
field of
view is
free from
'illurninatiorl
irregularities', irrespective of the shape of
the
light source,"
As shown in the drawing
below,
the filament
of the light
source (6 V, 5A) forms, through the collector, an image
a t
the
aperture iris diaphragm. This image, located
a t
about the same place as the front focal point
of the condenser, is projected by the objective to the rear focal point of the objective,
that is, in the exit pupil
of
the objective. Since this image is then projected Into the observer's
pupil, it i s completely invisible to the observer, hence, illumination
f r e
from 'irregularities'
is obtained.
The field iris diaphragm, as will
be
noted from the
drawing, freely controls, by its opening and closing,
/
~Aapa.pt.m
i
the diameter of the cone of light entering
the
Obletllvsrsarhlpdnt
condenser from the light source.
spaam
P ~ W
ad thmd~mLgeof~lp19um
Correct
Koehler illumination with the VANOX can
~ ~ m d s y ~ m a ~ a ~ m -
be ob t'ai ned by appropriate posi tinning of
rhe
auxiliary lens system and adjustment of aperture
hx"mh6-
- i - -
FlsP
I ~ d ' s p h r n
and field iris diaphragms.