Certain cellular structures like cellulose walls or starch grains can hardly be made visible without specialized staining techniques. Polarization contrast microscopy is a convenient way to make birefringent crystalline structures like starch grains or cellulose visible without staining. When illuminated with polarized light, birefringent structures can produce specific color effects which can be easily recognized using a polarizing microscope. This makes it easy to identify e.g. starch grains in a given biological specimen. In life sciences, polarization microscopy is frequently employed in plant research. An additional application field for polarizing microscopes is the optical mineralogy. In any case, a specialized strain-free optics is necessary to provide the best possible polarization contrast.
This tutorial will explain the optical elements in the light path and the operating mode of polarization contrast taking the example of an inverted and motorized high-end research optical microscope which can be used for transmitted light contrasting methods and fluorescence microscopy.