INSTRUMENT DESCRIPTION
Axioskop 2
plus
Carl Zeiss
Objectives
Axioskop 2
mot plus
1-12
B 40-075 e 10/03
1.5 Objectives
The objectives are the optical centerpiece of the
microscope. The following is an example of how
objectives can be labelled:
Achroplan 10x/0.25
∞
0.17
where
10x : objective magnification, with a defined
color ring on the objective being allocated
to each magnification step (Zeiss color
code)
0.25 : numerical aperture
∞
: infinite image distance; these objectives
can only be used with ICS microscopes
from Carl Zeiss
0.17 : can only be used with cover slip thickness D
= 0.17 mm
or
−
: can be used with cover slip thickness D = 0
or 0.17 mm
Other labels:
Oil
: oil immersion objective
Ph 2 : phase contrast objective with a green color ring and phase stop Ph 2
Color ring code for objective magnification
Color ring on
objective
black
brown
red
orange
yellow
green
light
blue
dark
blue
white
Magnification
factor
1.25x
2.5x
4x; 5x
6.3x
10x
16x;20x;
25x;32x
40x; 50x
63x
100x;
150x
The objective magnification multiplied with the eyepiece magnification (minimum 10x) results in the
visual overall magnification: e.g. 10 x 10 = 100x.
When working with the microscopes, the total magnification should not drop below or exceed the range
of useful magnification. The range of useful magnification was defined by Ernst ABBE as 500 to 1000
times the numerical aperture of the used objective. No further details are resolved above that limit. The
range of useful magnification for an objective with a numerical aperture of 0.25 is between 125 and
250x accordingly.
The exact observance of the cover slip thickness of 0.17 mm is all the more necessary the higher the
numeric aperture of the objective. Therefore, certain objectives can be set for different cover slip
thickness (due to correction mount). For this, a specimen area is searched, and the position of the
correction ring where optimum focus and image contrast are obtained is determined (refocusing is
always required).
Fig. 1-3
Objective
