OPERATION
Carl Zeiss
Lighting and contrasting method in transmitted light
Axio Lab.A1
90 430037-7144-001
04/2013
4.1.6.1
Demonstrating birefringence with the Axio Lab for conoscopy
(1) Application
The transmitted light polarization method is used for specimens which change the state of polarization of
light. These specimens, such as crystals, minerals or polymers, are referred to as birefringent. When these
birefringent substances are viewed between crossed polarizers (polarizer
A
analyzer), they appear bright
while their surroundings remain dark.
Birefringent substances are identified in that they show four bright and four dark positions when rotated
through 360° between crossed polarizers. Depending on birefringence, thickness and 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) Instrumentation
On the Axio Lab.A1 microscope for transmitted light conoscopy:
Tension-free objectives
Rotary stage Pol
Polarizer D (rotatable or fixed)
Compensator lambda or lambda/4
The depolarizer is already incorporated in the Axio Lb.A1 stand for conoscopy.
A depolarizer (quartz depolarizer) should be installed in all microscopes used for examining
mineral/geological specimens.
A depolarizer suppresses undesirable polarization effects which may occur after the analyzer (e.g. on
prism surfaces in the tube), or shifts these to higher orders.