OPERATION
Carl Zeiss
Illumination and contrast methods
Axio Imager
156
430000-7344-001
M70-2-0020 e 06/2009
4.9.5
Setting transmitted-light polarization for orthoscopic observation
Magnified viewing, e.g. of a thin section, in polarized light is called orthoscopy (Greek: orthos = straight;
skopein = seeing), because illumination is by "straight" light rays, which – with the aperture diaphragm
largely closed – are parallel to the microscope axis.
4.9.5.1
Detecting birefringence
(1) Use
The technique of transmitted-light polarization is used for specimens that change the state of polarization
of light. These specimens, such as crystals, minerals or polymers, are called birefringent. When these
birefringent substances are viewed between crossed polarizers (polarizer
⊥
Analyzer), they appear
brightened, while their surroundings remains dark.
Birefringent substances are identified by the fact that they show four bright and four dark positions while
being rotated through 360° between crossed polarizers. Dependent on birefringence, thickness as well as
orientation of the specimen, interference colors ranging from gray (mostly with biological specimens) to
white, yellow, red and blue appear in this process. These interference colors can be of the first or any
higher order.
(2) Microscope
configuration
−
Phototube Pol
−
Achromatic-aplanatic universal condenser Pol
−
Strain-free objectives
−
Rotary stage Pol (4-122/
2
)
−
Polarizer D (rotatable or fixed) (4-122/
3
)
oder
polarizer integrated in the turret disk of the
condenser
−
1
) or analyzer module D
4
) in reflector turret (only on
microscopes equipped with a reflector turret)
(3) Setting
the
microscope
•
Set the microscope as for transmitted-light
bright field according to KÖHLER (see Section
4.9.1 (3)).
•
Center rotary stage Pol (4-122/
2
) and objectives
(if not done yet – see Section 3.34.3).
•
Swivel polarizer (4-122/
3
) into the light path
and, if it is rotatable, turn it to 0°.
Fig. 4-122 Components for transmitted-light
polarization
