Exploiting the properties of polarized light to identify and characterize the structure and properties of materials
Polarized light is created by passing light through a polarizing filter. This transmits light in one direction only. There are two polarizing filters in a polarizing microscope - above and below the sample (the polarizer and analyzer). The way in which materials interact with polarized light can provide information about their structure and composition.
Around 90% of all solid substances have optical properties that vary with the orientation of incident light (anisotropic materials). When these anisotropic materials are rotated, the observer may see brightness and / or color changes ('pleochroism') under polarized light that depend on the orientation of the material in the light path. These changes can be used to characterize and identify various materials. Isotropic materials, which include unstressed glasses and cubic crystals, demonstrate the same optical properties in all directions.
Polarizing microscopy can be used with reflected and transmitted light. Reflected light is useful for the study of opaque materials such as mineral oxides and sulphides, metals and silicon wafers and requires stress-free objectives that have not been corrected for viewing through a coverslip.
Polarized light microscopy is perhaps best known for its geological applications - primarily for the study of minerals in rock thin sections but it can also be used to study many other materials including both natural and industrial minerals (refined, extracted or manufactured), composites such as cements, ceramics, mineral fibres and polymers, and crystalline or highly ordered biological molecules such as DNA, starch, wood and urea. The technique can be used both qualitatively and quantitatively in materials science, geology, chemistry, biology, metallurgy and medicine.
Nikon has several polarizing microscopes including the Eclipse LV100 POL (quantitative polarizing light microscopes for research applications), Eclipse Ci POL and Eclipse E200 POL (for education and routine laboratory use).
The Eclipse LV100 POL is the most advanced and versatile polarizing microscope system and is ideal for a range of quantitative and qualitative applications in materials science.
Polarized Light Microscopy|
Introduction to Polarized Light Microscopy