ABSTRACT
The contrast between the major components in colloidal delivery systems is often relatively poor because they have fairly similar refractive indices, which often makes it difficult to reliably distinguish them from each other using conventional bright-field optical microscopy. This problem can often be overcome using more specialized optical microscopy methods that are designed to enhance contrast, improve image quality, and distinguish specific components (Murphy 2012). The contrast between different components can often be enhanced by modifying the design of the optics within a light microscope, for example, using phase contrast or differential interference contrast microscopy (Murphy 2012). These techniques
improve the contrast by using specially designed lenses that convert small differences in refractive index in the sample into appreciable differences in light intensity in the final image. Structures of optically anisotropic components, such as fat crystals, liquid crystals, or native starch granules, can be studied using polarization light microscopy (Aguilera et al. 1999). In this case, the anisotropic components appear as white objects against a black background and can therefore be clearly distinguished.
