Setting Transmitted Light Polarization With The Conoscopy Stand; Determining The Optical Character Of Crystals - Ryf Axio Lab.A1 Operating Manual

Axio Lab.A1
4.1.5

Setting transmitted light polarization with the conoscopy stand

4.1.6

Determining the optical character of crystals

For the classification (and thus identification) of crystalline material – instead of the observation of the
specimen itself – the analysis of an interference image in the objective pupil provides the more valuable
information. This image is visible in the eyepiece when an additional lens (so-called Bertrand lens) is
switched on. Alternatively, the auxiliary microscope or a diopter may be used to view the interference
image.
In contrast to orthoscopy, this is referred to as conoscopy, because the illumination is ideally provided by
a wide open cone. In practice this means that the aperture diaphragm is fully open and the objective
should likewise have a high aperture.
(1) Application
The crystal diagnosis is for determining the optical character of transparent and weakly absorbent
crystals. This method is also referred to as conoscopy.
Its main application is the classical mineral microscopy. However, synthetic crystals, industrial minerals
and plastics (e.g. films) can also be identified and characterized.
(2) Instrumentation
Conoscopic viewing is preferably carried out on the Axio Lab.A1 microscope for transmitted light
conoscopy.
Tension-free objectives; recommended:
N-Achroplan 50x/0.8 Pol objective or
EC Plan-Neofluar 40x/0.9 Pol objective
Rotary stage Pol
Polarizer D (rotatable or fixed)
0.9 Pol condenser
(3) Setting the microscope for conoscopy
In the case of uniaxial crystals, the most favorable orientation for conoscopic viewing is obtained with
those specimen features (e.g. of a thin section) that in orthoscopic viewing change the brightness as little
as possible. In this case, the direction of viewing and the optical axis are parallel. The same applies to
biaxial crystals if viewed in or approximately in the direction of one of the two optical axes.
04/2013
OPERATION
Lighting and contrasting method in transmitted light
430037-7144-001
Carl Zeiss
87