OPERATION
Axiolab 5
Illumination and contrast methods in transmitted light
ZEISS
05/2019
430037-7444-001
93
(4) Conclusions
The gray-white color appearing first in the bright
position in the above example (Fig. 4-8/
1
)
corresponds to a path difference of 150 nm
according to the Michel-Lévy color chart (Fig. 4-9).
When the lambda compensator is brought into the
beam path, the non-birefringent "surroundings"
of the synthetic fiber appear dark red, which
corresponds to the path difference of the
compensator of 550 nm (1st order interference
color for the path difference of 550 nm
corresponds to 1
λ
).
If the polarization direction (n
γ
or n
γ
'
) of the
birefringent sample to be examined is parallel to
the principal polarization direction (n
γ
) of the
lambda compensator, i.e. in the NE-SW direction,
the path difference of the sample (e.g. gray-white:
150 nm) and the path difference of the lambda
compensator (red: 550 nm) add up. This results in
a color change of the sample from grayish white to
greenish-blue (resulting path difference = 700 nm).
If the polarization direction of the birefringent sample to be examined is perpendicular to the principal
polarization direction of the lambda compensator, i.e. in the NW-SE direction, the path difference of the
sample (e.g. gray-white: 150 nm) is subtracted from the path difference of the compensator (red:
550 nm). In this case, the interference color of the sample visibly changes from gray-white to orange
(resulting path difference = 400 nm).
NOTE
The Michel-Lévy color tables are available in the literature catalog no. 42-312.
Fig. 4-9
Schematic diagram of the color
charts developed by Michel-Lévy