Polarized light microscopes make bifrefringent crystalline structures visible without staining. Birefrigent structures when illuminated under the microscope give off color effects which can help identify the specimen. Polarized light microscopes are used in fields including minerology, asbestos, plant research, gout research, urine crystals, etc.
A true polarized light microscope requires that all of the optics be strain free and components must be inserted into the light path. A polarizing light microscope will have a polarizer, analyzer. A polarized light microscope for geology applications will have a circular rotating stage, bertand lens, and other plates such as 1/4 wave or quartz wedge.
Polarizer - A polarizer is used to restrict the vibration of light waves to a single direction allowing only certain waves to pass through it. This is found below the condenser.
Analyzer - This is a second polarizer located above the objectives of the microscope.
The polarizer will always be rotatable, the analyzer may be fixed in one position or rotatable as well. If the analyzer remains fixed and you roatate the polarizer so that the polarizer and anlyaer are in a 90 degree position to each other you will achieve what is called extinction. This must be done with the specimen removed from the light path. Once you achieve extinction you can place your specimen on the stage. As you move or rotate your specimen containing birefringent structures you will see the structures illuminate.
Basic polarization can be added to almost any microscope by simply adding a polarizer and analyzer to the microscope. A rotating stage is not necessary for all applications.