OPERATION
Axiolab 5
Illumination and contrast methods in reflected light
ZEISS
05/2019
430037-7444-001
115
4.3.3
Configuring reflected light polarization – Proof of bireflectance and reflexion
pleochroism
(1) Application
Reflected light polarization is a further contrasting method for cut surfaces of mineral ore, coal, ceramic
products, certain metals and alloys. Depending on the orientation of the crystals and specimen details,
the cut surfaces often react differently when reflected in linear polarized light
The illumination light is linearly polarized by the polarizer before passing through the objective onto the
specimen surface, where it is reflected. Here the beam parts experience path differences depending on
the structure and polarization of optical rotations which, when passing through the analyzer, are
displayed in different shades of gray. The gray can be converted into a color contrast with the aid of a
compensator equipped with a lambda plate.
With objectives of very low magnification, a rotatable lambda/4 plate arranged in front of the objective
(Antiflex cap) permits the reflections to be eliminated even with "dark" specimen surfaces, which
otherwise would be unavoidable.
(2) Instrumentation
Observations in the reflected light darkfield can be made only on Axiolab 5 microscopes for reflected
light.
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Pol rotary stage
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Epiplan-Neofluar Pol, EC Epiplan-Neofluar Pol, Epiplan Pol objectives
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C DIC/DIC/TIC ACR P&C or DIC/Pol ACR P&C or DIC Red I ACR P&C reflector module
or Pol ACR P&C reflector module in reflector turret
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Analyzer slider D, fixed or lambda compensator, 6x20mm or Lambda/4, 6x20mm
(3) Configuring reflected light polarization
•
Adjust the microscope as described in section 4.3.1 for the reflected light brightfield.
•
Swivel the P&C (for DIC or Pol) reflector module on the reflector turret into the beam path and insert
the analyzer slider (or lambda compensator or lambda/4 compensator) into the 6x20mm slot.
•
Insert a specimen, adjust the desired magnification level, focus and observe the specimen in the
polarization contrast now present while turning the Pol rotary stage.
A specimen is bireflective when the details display differences in brightness and color which change when
the stage is rotated.
For samples with low bireflectance it is advisable to use the rotatable analyzer equipped with a lambda
plate.
Pleochroism can be detected when the color of the specimen changes when the stage is rotated
(reflected light polarizer turned on, analyzer turned off).
