ZEISS
OPERATION
Axio Imager 2
Illumination and contrast methods
194
430000-7544-001
01/2016
4.12.12
Setting reflected-light polarization – Detection of bireflection and reflection
pleochroism
(1)
Application
Reflected light polarization presents a further contrasting option for polished sections of ore minerals,
coals, ceramic products, certain metals and metal alloys, as these specimens often exhibit varied reflection
behavior in linearly polarized light depending on the orientation of the crystals and specimen features.
The illumination light is linearly polarized by the polarizer and directed through the objective onto the
specimen surface, where it is reflected. Here, the light rays experience structure-dependent path
differences or polarization-optical rotations which, on passing the analyzer, appear as different gray-scale
values. A compensator with lambda plate permits conversion from gray to color contrast.
Important!
Nevertheless, no 6x20 compensator should be used for this purpose!
With very low magnification objectives, a rotatable
λ
/4 plate in front of the objective (Antiflex cap)
permits reflections to be eliminated even with "dark" specimen surfaces which otherwise would be
unavoidable.
(2)
Instrument equipment
−
Stand with connected and aligned HAL 100 halogen illuminator.
−
Epiplan-Neofluar Pol, EC Epiplan-Neofluar Pol, Epiplan Pol objectives.
−
Reflector module DIC P&C or DIC Rot I P&C in reflector turret;
or reflector module Pol P&C plus analyzer slider;
or analyzer slider plus polarizer slider.
(3) Setting reflected-light polarization
•
Set the microscope for reflected-light brightfield as described in Section 4.12.7.
•
If you use the objective position with DIC slider slot, remove the DIC slider if installed.
•
On the reflector turret (Fig. 212/
3
), swing the reflector module DIC P&C (Fig. 212/
4
) into the light
path. You may also swing in reflector module Pol P&C and insert the analyzer slider in the
corresponding slot. When using the combination of analyzer slider (Fig. 212/
1
) and polarizer slider
2
), you may also push these into the corresponding slots. If you use the fixed versions of
these sliders, the polarizer is oriented EAST-WEST and the analyzer NORTH-SOUTH.
•
Put the specimen onto the stage, set the desired magnification, focus and observe the specimen in the
polarization contrast now available while rotating the stage.
If the specimen features exhibit variations in brightness and color when the stage is rotated, the specimen
is said to have bireflection.
If the specimen only has weak bireflection, it is advisable to use the analyzer with rotatable lambda plate.
Pleochroism can be recognized from color variations occurring in the specimen when the stage is rotated
(with the reflected-light polarizer in the light path but not the analyzer).
