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Maintenance / Further information
G-30-1607-en
OPMI® VARIO on S8, S81 & S88 Suspension Systems
Issue 5.0
Printed on 30. 01. 2009
Magnifications / Fields of view
If the magnification factor
γ
of the zoom system is known, you can calcu-
late the total magnification of the surgical microscope. The following
equation is used to determine the total magnification:
Where:
f
tube
is the focal length of the binocular tube
f
obj
is the focal length of the main objective lens (does not correspond to
working distance!)
γ
is the magnification factor of the zoom system
M
eye
is the magnification of the eyepiece
Example:
f
tube
= 170 mm, f
obj
= 300 mm,
γ
= 1.6 and M
eye
= 12.5 x.
The resulting total magnification is:
If the total magnification of the surgical microscope M
T
is known, you can
use the formula
to calculate the field of view diameter FoV
D
of the surgical microscope.
The field of view diameter is the diameter of the circular surgical field
which can be seen through the eyepieces.
FoVN in the above formula stands for the field of view number of the eye-
piece.
By entering the value MT = 11.3 in the formula, we obtain the following
field of view diameter for 12.5x eyepieces with a field of view number
FoVN of 18 mm:
M
T
f
tube
f
obj
-----------
γ
M
eye
⋅
⋅
=
M
T
170 mm
300mm
---------------------
1.6
12.5 = 11.3
⋅
⋅
=
FoV
D
FoVN
M
eye
⋅
M
T
------------------------------------
=
FoV
D
=
= 19.9 mm
18 mm . 12.5
11.3
