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OPERATION
Carl Zeiss
Illumination and contrast methods
Axio Imager
158
430000-7344-001
M70-2-0020 e 06/2009
(3) Setting
the
microscope
The microscope has been prepared as described in Section 4.9.5.1 (3).
•
Rotate the rotary stage Pol with the specimen, e.g. a synthetic fiber, until the specimen appears as
dark as possible. In this position, the fiber extends parallel to one of the two directions of the
crosslines reticle.
•
Next, turn on the rotary stage Pol by 45°, until the longitudinal axis of the fiber is oriented NORTH-
EAST (NE) – SOUTH-WEST (SW) (Fig. 4-123). In this position, the specimen shows the maximum
brightness (diagonal position) and may appear in any color.
•
Push in the full-wave compensator
λ
.
Like the specimen, the compensator
λ
is a birefringent object, though one with a defined path difference
of 550 nm and the principal vibration direction n
γ
definitely oriented in NE-SW direction
By moving compensator
λ
into the light path, the specimen changes its color. The kind of color change
depends on the orientation of the specimen (NE-SW or NW-SE).
The changes in color are based on optical interference. The interference colors (path differences) in both
diagonal positions (NE-SW and NW-SE) of the specimen must be compared in this connection.
The path difference results from the superposition (interference) of the vibration direction of the
specimen with the vibration direction of the compensator
λ
.
The greater path difference occurs, if the vibration direction of the specimen with the absolutely or
relatively highest refractive index (n
γ
or n
γ
') is parallel to the principal vibration direction of
compensator
λ
. The specimen will then appear, for instance, greenish-blue (4-123/
2
)
.
The smallest path difference occurs, if the vibration direction of the specimen with the absolutely or
relatively lowest refractive index (n
α
or n
α
') is perpendicular to the vibration direction of the
compensator
λ
. The specimen will then appear, for instance, in yellow (4-123/
3
)
.