DIC also allows the microscope to achieve excellent resolution. With DIC, it is possible to make fuller use of the numerical aperture of the system and to provide optical staining (color). There are numerous advantages in DIC microscopy as compared to phase contrast microscopy. Because of the prism design and placements, the background will be homogeneous for whatever color has been selected. This allows for varying optical path differences by moving the prism, providing the user a mechanism to alter the brightness and color of the background and specimen. The upper prism may also be arranged so it can be moved horizontally. In some microscopes, the upper modified Wollaston prism is combined in a single fitting with the analyzer incorporated above it. This shadow effect bestows a pseudo three-dimensional appearance to the specimen. The design results in one side of a detail appearing bright (or possibly in color) while the other side appears darker (or another color). The light then proceeds toward the eyepiece where it can be observed as differences in intensity and color. This is accomplished by placing a second polarizer (analyzer) above the upper Wollaston beam-combining prism. In order for the beams to interfere, the vibrations of the beams of different path length must be brought into the same plane and axis. As a result of having traversed the specimen, the paths of the parallel beams are not of the same length (optical path difference) for differing areas of the specimen. This removes the shear and the original path difference between the beam pairs. When the parallel beams enter the objective, they are focused above the rear focal plane where they enter a second modified Wollaston prism that combines the two beams at a defined distance outside of the prism itself. These variations cause alterations in the wave path of both beams passing through areas of any specimen details lying close together. The split beams enter and pass through the specimen where their wave paths are altered in accordance with the specimen's varying thickness, slopes, and refractive indices.
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