ZEISS
3 Product and Functional Description | 3.4 Microscopy and Contrast Methods
3.4.6.5 Transmitted Light Polarization for Coniscopic Observation
The determination of the optical character of transparent and weakly absorbent crystals is used to
diagnose crystals. This method is also termed conoscopy. Its main application is classical mineral
microscopy. However, it also facilitates the identification and characterization of synthetic crystals,
industrial minerals and plastics (e.g. films).
For the classification (and thus identification) of crystalline matter, the examination of the interfer-
ence image in the objective pupil delivers more valuable information than that obtained by view-
ing the sample itself. The interference image becomes visible in the eyepiece if an additional opti-
cal system (fixed or focusing Bertrand lens or, in the basic version, the auxiliary microscope or
diopter) is used.
In contrast to orthoscopy, this technique is called conoscopy, because here the sample is ideally il-
luminated through a wide-open cone. In practical microscopic work, this means that the con-
denser front lens (0.9) must be in the light path, the aperture diaphragm fully open, and the ob-
jective, too, should be a high-aperture type.
3.4.7 Reflected Light Brightfield Microscopy Using the KÖHLER Method
Reflected light brightfield microscopy is the easiest and most commonly used RL-microscopy
method. It is used to examine optically opaque samples or samples as e.g. cut, polished, etched
metal or ores.
In order to obtain an image as close as possible to the object, not only the so-called direct beam
bundles but also the indirect ones, i.e. the beam bundles diffracted and scattered at the prepara-
tion details, are of essential importance. According to ABBE, the larger the indirect beam compo-
nents are, the more true to the object the microscopic image is.
The cone of light emerging from the reflected light light source is reflected on a color-neutral
beam splitter before it passes through the objective which is focused on the sample surface (so-
called condenser function). The objective collects the light reflected on the sample and creates,
with the tube lens, the microscopic intermediate image. This image can then be examined visually
or documented using a camera.
3.4.8 Reflected Light Darkfield Microscopy Using the KÖHLER Method
The reflected light darkfield method is applied when samples are examined, which do not have ar-
eas with different reflectivity (ideal brightfield samples), but which show deflections (as scratches,
cracks, dust particles etc.) on the plane surface. All such light-scattering details appear bright in
the darkfield, while the reflective plane areas remain dark.
3.4.9 Reflected Light DIC and C-DIC Microscopy
The reflected light DIC and the reflected light C-DIC methods (DIC = Differential Interference Con-
trast; C-DIC = Circular polarized light–differential interference contrast) are used for the high-con-
trast imaging of small height differences on the surface of opaque samples.
C–DIC is a polarization–optical differential interference contrast method where, unlike conven-
tional DIC according to Nomarski, the DIC prism is arranged in circular, not linear, polarized light.
Consequently, the interference contrast generated is invariant in relation to the oscillation orienta-
tion of the DIC prism, and so the latter can be rotated directionally in accordance with the charac-
teristics of the object. This means that the stage does not need to be rotated while the relation-
ship with the object is preserved. For the user, this means more information and an increase in
sample throughput.
Instruction Manual ZEISS Axioscope 5, Axioscope 5/7 MAT | en-US | Rev. 13 | 430035-7344-001
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