Parts Of The Polarized Light Microscope

The polarized light microscope magnifies objects invisible or not easily seen by the naked eye. But unlike its other microscope counterparts, it has an added advantage of using polarized light to glean information about the specimen’s absorption color, refractive indices and optical behavior. It is frequently employed in the study of minerals, especially in the field of geology. Its application also extends to the fields of biology and medicine. The different parts of a polarized microscope include its base and microscope stand which support its whole structure. A light source illuminates the specimen that facilitates viewing. Objectives magnify the specimen and are usually strain-free.

These strain-free objectives prevent the occurence of optical effects which are produced with ordinary objectives. These could produce artifacts and may complicate observations. A nosepiece allows the objectives to freely rotate and be interchanged depending on the magnification desired. The specimen stage of the polarized microscope was designed to rotate. This facilitates orientation with centration of the objectives and the stage. This then allows the microscope optical axis to coincide with the center of the field of view. An adjustment tube facilitates focusing and ensures the best detail of the specimen depending on the observer. The eyepiece where the observer looks into the field of view is fitted with a cross wire graticule. Some polarized microscopes allow the substitution of the cross wire graticule with a photmicrograph graticule. This device enhances focusing of the specimen and can compose images with a set of frames bounding the area of the viewfield. The images obtained can then be photographed and saved digitally or into film. Bertrand lenses makes the examination of the objective rear focal plane easier. It facilitates the accurate adjustment of the illuminating apperture diaphragm and the viewing of interference figures. A slot allows the insertion of compensators or retardation plates between the polarizers. These enhance the optical path differences in the specimen. The slot is usually found in the microscope nosepiece or in an intermediate tube situated between the body and the eyepiece tubes. This arrangement then places the compensator between the specimen and the analyzer. The parts that distinguish the polarizing light microscope from the other types of microscope are the polarizing filters. These are the polarizer and the analizer. The polarizer fixes the permitted vibration of light in the left to right or east to west direction. It is usually found beneath the specimen stage. The polarizer may be rotated a full 360 degrees depending on the image desired and the discretion of the observer. The analyzer on the other hand fixes the vibration of light in the north to south or top to botton direction, at right angles with the direction of light from the polarizer but it may also be rotated in some microscope models. It is positioned above the objectives and may be moved in and out of the light path whenever necessary. The presence of both the polarizer and analyzer in the optical path produces light vibration directions that are perpendicular or at right angles to each other. This is the crossed configuration where no light passes through the system and only a darkfield may be appreciated through the eyepieces. Both the polarizer and analyzer can be adjusted to change the direction of light through the system. The polarizing filters are the essential components of the polarizing light microscope giving the observer the characteristic images.