UNIVERSITY | Polarization microscopes

A petrographic microscope is used to identify rocks and minerals in thin sections. It's an standard optical microscope that is equipped with a circular 360° rotating stage, strain free objectives, a polariser to generate polarised light and a second polariser - called the "analyzer" to the light path between objective and eyepiece

Petrographic microscopes can also be equipped with so-called "Bertrand lens", which focuses and enlarges the interference figure that is imaged at the back focal plane of the objective. Usualy petrographic microscopes have specially-cut oriented filters like a quartz wedge, quarter-wave mica plate and half-wave mica plate into the optical train between the polarizers to identify positive and negative birefringence, as well the mineral order

Most crystalline materials and minerals change the polarizing light directions, allowing some of the altered light to pass through the analyzer to the eyepiecses. Using one polarizer makes it possible to view the slide in so-called "plane polarized" light. Using the two polarisers, allows analysis in so-called "cross polarized" light mode