OPERATION
ZEISS
Illumination and contrast methods in transmitted light
Axiolab 5
100
430037-7444-001
05/2019
Inserting a lambda compensator
(473704-0000-000) or lambda/4 (473714-0000-000) or a 0-4 lambda
wedge compensator (000000-1140-663) in the compensator slot with the initial state of the axial figure
being as illustrated in Fig. 4-12 results in the following changes in color (shown schematically as blue and
yellow areas) to the axial figure, thus allowing differentiation in "optically positive" and "optically
negative".
Optically uniaxial
Optically biaxial
Positive
Negative
Positive
Negative
Lambda plate
(white
→
blue
→
yellow)
+ = Blue
– = Yellow
Quartz wedge
(Direction of motion
at insertion)
Direction of
movement
Lambda/4 plate
(position of black
spots)
Fig. 4-12
Determining optical character
In the case of less favourable sections in which the cross-hair center is optically uniaxial or the isogyres are
optically biaxial specimens outside the objective pupil, an assessment is possible as follows:
•
If the black isogyres are
straight
and they run parallel to the pupil (in relation to the cross-hairs), the
specimen is
optically uniaxial
.
•
If the black isogyres are
curved lines
which wander on a circular path through the pupil, the
specimen is
optically biaxial
.
NOTE
Axial figures can often be better displayed with circular polarization. In particular, the axis
angle of optically biaxial specimens (quasi the distance between the isogyres) can be
determined more clearly. The optical character can also be determined. The lambda
compensator (6x20mm), arranged in the compensator slot, is used for this purpose.
NOTE
Two storage compartments for 6x20mm slides are located on the back side of the conoscopy
stand.