OPERATION
ZEISS
Illumination and contrast methods in transmitted light
Axiolab 5
104
430037-7444-001
05/2019
•
Subsequently reinsert the analyzer slider and remove the Pol adjustment tool sample. The pass
directions of the polarizer and analyzer will now be parallel to the crossline reticle (polarizer EW,
analyzer NS).
NOTE
An adjustment of the crossline reticle is not necessary when working with the intermediate
plate and the binocular photo tube Pol (425520-9100-000).
•
Rotate the rotary stage Pol with the sample, e.g. a synthetic fiber, until the sample appears as dark as
possible. In this position, the fiber extends parallel to one of the two directions of the crossline reticle.
NOTE
Do not change the inter-pupillary distance on the binocular tube, as the angle of the crossline
reticle to the fiber will be changed.
•
Now turn the stage on by 45° so that the longitudinal axis of the fiber is oriented NE-SW (Fig. 4-15).
The sample will display the greatest brightness here (diagonal position). In this position the sample
may have any color.
•
Insert the lambda compensator (473704-0000-000).
Like the sample, the lambda compensator is a birefringent object, albeit with a defined path difference of
550 nm and the principal polarization direction n
γ
definitely oriented in a NE-SW direction.
When the lambda compensator is moved into the beam path, the sample changes its color. The type of
color change depends on the orientation of the sample (NE-SW or NW-SE).
The changes in color are attributable to optical interference. The interference colors (path differences) in
both diagonal positions (NE-SW and NW-SE) of the sample must be compared in this connection.
The path difference results from the superimposition (interference) of the polarization direction of the
sample over the polarization direction of the lambda compensator.
The largest path difference occurs when the polarization direction of the sample with the absolute or
relative highest refractive index (n
γ
or n
γ
’
) is parallel to the principal polarization direction of the lambda
compensator. The sample will then appear greenish-blue, for example (Fig. 4-14/
2
).
The smallest path difference occurs when the polarization direction of the sample with the absolute or
relative lowest refractive index (n
α
or n
α
’
) is perpendicular to the polarization direction of the lambda
compensator. The sample will then appear yellow, for example (Fig. 4-14/
3
).