OPERATION
Axiolab 5
Illumination and contrast methods in transmitted light
ZEISS
05/2019
430037-7444-001
99
•
The polarization direction can be changed using the setting wheel (Fig. 4-11/
4
) of the analyzer.
ATTENTION
The movements of rotary knobs
A
and
BL
and the respective setting wheels are coupled with
each other. Only
one
control element should therefore be operated at a time and the
movement of the other should not be inhibited or blocked. Otherwise, mechanical damage
may occur.
NOTE
If the rotary knob
BL
is set to the
On
position, rotary knob
A
is automatically moved into the
On
position if it is not there already.
If, on the other hand, rotary knob
A
is set to the
Off
position, rotary knob
BL
is automatically
moved into the
Off
position if it is not there already.
•
Place a selected crystal in the center of the crossline reticle.
•
Swivel in the N-Achroplan 50x/0.8 Pol objective or EC Plan-Neofluar 40x/0.9 Pol objective and focus
using the focusing drive.
•
If necessary, close the luminous-field aperture to avoid superimposition of axial figures of neighboring
crystals on the axial figure to be examined. The smallest crystal value that can be faded out is 170 µm.
•
Switch on Bertrand lens
BL
1
) (
On
position). The axial figure will appear in the field of view.
•
Bring the axial figure into focus using the setting wheel (Fig. 4-11/
5
).
(4) Evaluation
Crystalline anisotropic specimens can be separated into optical uni- and biaxial specimens, in each case
with an "optically positive" or "negative" character.
Uniaxial
crystals display a
black cross
when the optical axis is parallel to the direction of view.
Depending on the level of birefringence and specimen thickness
, concentrically arranged colored
interference rings
(so-called isochromes) may appear (see also Fig. 4-12, second row).
The lines of this black cross remain closed when the stage is rotated. Depending on the section it may lie
within or outside the displayed objective pupil.
With
optically biaxial
crystals, the cross resolves into two
dark hyperbola branches
(the so-called
isogyres)
depending on stage rotation
, which are surrounded by colored interference patterns
depending on the amount of birefringence and specimen thickness (suggestive of the figure "8").
