The polarized light microscope is designed to observe specimens that are visible primarily due to their optically anisotropic character. Polarizing microscopes must be equipped with both a polarizer, positioned in the light path somewhere before the specimen, and an analyzer (a second polarizer), placed in the optical pathway between the objective rear aperture and the observation tubes or camera port. Image contrast arises from the interaction of plane-polarized light with a birefringent (or doubly-refracting) specimen to produce two individual wave components that are each polarized in mutually perpendicular planes. The velocities of these components are different and vary with the propagation direction through the specimen. After exiting the specimen, the light components become out of phase, but are recombined with constructive and destructive interference when they pass through the analyzer.
Rediscovering polarized light microscopy. American Laboratory 35: 55-61 (2003). Written by a research microscopist at the McCrone Research Institute, this nice review article covers the basic aspects of polarized light microscopy. Included are discussions of birefringence, indicatrix models, quantitative aspects, and classes of materials that can be used with polarized light microscopy.
Polarization microscopy. Current Protocols in Cell Biology Unit 4.9: 4.91-4.9.22 (2002). Professor Inoué, a recognized pioneer in polarized light microscopy, provides an introduction to the topic, the optics involved, and practical considerations for observing submicroscopic structures. Specific examples of microtubules in the mitotic spindle, chromatin in maturing spermatids, and the skeletal spicules in larvae are included.
A new view on polarization microscopy. Nature 381: 811-812 (1996). Dr. Oldenbourg discusses improvements to the traditional polarized light microscope, which have enhanced the direct analysis of the molecular architecture in living cells. Examined are electro-optical devices, polarization algorithms, and digital image processing of images captured using birefringent specimens.
Quantitative polarized light microscopy. Journal of Microscopy 209: 13-22 (2003). The authors describe a confocal microscope modification that analyzes the polarization stte of light emerging from a specimen to permit quantitative polarized light microscopy. The system uses a rotating analyzer that enables images to be obtained where the image contrast corresponds to both specimen retardance and orientation.
A simplified, low-cost method for polarized light microscopy. American Journal of Tropical Medicine and Hygiene 81: 782-783 (2009). An excellent description of how a conventional transmitted light microscope can be easily and cheaply converted for imaging using polarized light. The authors include examples of malaria parasites in thick blood films to demonstrate the capabilities of the modified instrument.
The importance of polarized light microscopy in the analytical setting. Microscopy and Microanalysis 14: 1032-1033 (2008). A short review of how polarized light microscopy can provide information on a wide range of specimens. The author includes examples of plane-polarized images, dispersion staining of fibers, and stereoscopic images of wood, chemicals, and plant material.
Quantitative image analysis of birefringent biological material. Journal of Microscopy 187: 62-67 (1997). Interference color contrast in polarized light microscopy is adapted for quantitative image analysis based on a linear relationship between color intensity and birefringence. Included are examples of collagen ribbons in the dogfish egg case.
Visualization of mitotic HeLa cells by advanced polarized light microscopy. Micron 39: 635-638 (2008). A nice example of using a conventional polarized light microscope to observe molecular order non-destructively in living cells without staining. The authors perform time-lapse imaging of dividing HeLa cells to visualize the mitotic spindles and kinetochore microtubules.
Polarized light microscopy of spindles. Methods in Cell Biology 61: 175-208 (1998). The author describes the basic aspects of microscope configuration, such as contrast, noise, extinction factors, and retardation plates. This discussion is followed by examples of spindle birefringence in bundled and parallel microtubules, as well as individual spindle components.
Enhanced polarizing microscopy as a new tool in aneuploidy research in oocytes. Mutation Research 651: 131-140 (2008). A comprehensive treatment of the use of polarized light microscopy in clinical diagnosis. The authors study human oocytes and provide a detailed discussion of the techniques and implications of this research. Included is an outstanding bibliography with numerous pertinent references.