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OPERATION
Axioscope 5/7/Vario
Illumination and contrast methods in transmitted light …
ZEISS
03/2018
430035-7344-001
101
•
Now insert the analyzer back into the beam path and remove the adjustment sample. The forward
direction of the polarizer and analyzer is now parallel to the cross hair in the reticle (polarizer east-west,
analyzer north-south).
•
Turn the Pol rotary stage with the sample, e.g. a synthetic fiber, so that the sample reaches maximal
darkness. The fiber is now parallel to one of the two lines in the cross hair orientation. If the deflection
is significant (5° and more) you will need to recalibrate your microscope for polarization.
NOTE
Do not change the eyepiece distance on the binocular tube any further to avoid shifting the
angular position of the reticle to the fiber.
•
Now turn the stage by approx. 45° until the longitudinal axis of the fiber is pointing in northeast-
southwest direction (
Fig. 4-11). The sample now shows the strongest brightness (diagonal position).
The sample can have any color in this position.
•
Slide in the
λ
compensator.
Like the sample, the
λ
compensator is a birefringent object, but it has a defined path difference of
550 nm and a maximum oscillation direction n
γ
pointing strongly to NE-SW.
When the compensator
λ
is put in, the sample changes its color depending on its orientation (NE-SW or
NW-SE).
The changes in color are based on optical interference. It is necessary to compare the interference colors
(path differences) in both diagonal positions (NE-SW and NW-SE).
The path difference results from the interference of the polarization of the sample and the polarization of
the
λ
compensator.
The largest path difference occurs when the polarization direction of the sample or the absolute or
relative largest index of refraction (n
γ
or n
γ
') is parallel to the largest polarization direction of the
λ
compensator. The sample appears then e.g. in blue-green (Fig. 4-10/
2
).
The smallest path difference occurs when the direction of polarization of the sample with the absolute or
relative smallest index of refraction (n
α
or n
α
') is perpendicular to the polarization direction of the
compensator
λ
. The sample then appears e.g. yellow (Fig. 4-10/
3
).