Polarized light microscopy fundamentals

The choice of a particular technique is limited by factors such as availability, feasibility, and the nature of the information sought. Pharmaceutical scientists are more focused on the usefulness of a particular ME system for a drug delivery application and the influence of the microstructure on that, rather than on the fundamental understanding of aspects such as microstructure and phase behavior. Polarized light microscopy is a readily available technique that could be used at the early formulation development stage to differentiate between isotropic and anisotropic systems. Transmission electron microscopy (TEM) is another available technique that has been shown to provide microstructural as well as size-related information on droplet and bicontinuous ME systems. 

Then, microscopic examinations follow optical research microscopes allow to determine the number, thickness, and color sequence of layers in paint fragments, and to recognize the textures as well as fundamental features of pigment and extender mixtures. Bright field and dark field illuminations, polarized light microscopy (incident and transmitted), particularly the differential interference contrast (DIC) procedure, and fluorescence microscopy are necessary for paint examinations (see Figure 3(A)-3(E)). 

Figure 1.34 Formation of plane polarized light by a polarizing filter. (Reproduced with permission from D.B. Murphy, Fundamentals of Light Microscopy and Electronic Imaging, Wiley-Liss. 2001 John Wiley Sons Inc.)...

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