<f)
~
o
r=
z
8
w
i"
"'
z
u;
:::l
Aperture iri s
diaphragm
image
Objective
pu
pil
Fi
g.
41
Fig. 42
70
-
8O'Yo
-!,
- "
.A
..
scale
Aperture
Iris Diaphragm
(FigS.
41.(2)
I
• The aperture iris diaphragm determines the numerical aperture
of
the
illumination system. Matching the numerical aperture
of
the illumination
system
with
that
of
the objective provides
better
image resolution and
contrast, and
also increases the
depth
of
focus .
• Since the contrast
of
microscopic specimens
is
ordinarily low, setting
the condenser aperture iris diaphragm to
70-80%
of
the N.
A.
of
the
objective
in
use is usually recommended.
When
necessary, adjust this
ratio
by
removing the eyepiece and peeking into the eyepiece sleeve
to
see the image shown in Fig. 41.
Using
the
Numerical
Aperture
Scale
Set the condenser
numer
i
ca
l aperture
CD
to about 80% of the
NA
value @ indicated on the objective.
(Fig
.
42)
Example: W ith the Plan
40X
(NA 0.65), set the scale to 0.65 x 0.8
'"
0.5.
Compatibility
of
Objec
tiv
es
and Condensers
Condenser
Objective
Achromat
Achromatl
SWlng-out Ultra-low
magnification
U-AC
aplanat achromat
magnification
U-AAC
U-SC
U-ULC
l .
25X
/'
V
-------
2X
Usable
by
rroW1g
Usable
frort eI!m9lt 0I.f. d
4X
Usab
le to
FN22
th
e light path·'
..........
.
.......
.
.........
.
lO
-
60X
Fr
ont
element
/'
Usable Usable
..
i
.~
..
~~~
.
~
.
~
..
~~
.
~
...
100X
NA
not fu
lly
adequate "'
* 1
When
using the U-
SC
swing-out achromat condenser together
with
the
2X
or
4X
ob
jective, fu
ll
y open the condenser aperture and use the field iris diaphragm
in
the
base as aperture diaphragm.
*2 Although slightly Inadequate
NA
results In a
some
wh
at darker field
of
View
wit
h a
l00X
ob
j
ect
i
ve
. the
comb
ination IS usable .
• To obtain
better
illumination, use
of
the U-ULC is recommended in photomicrography
when
using the
2X
or
4X
objective.
19
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