Many biological targets of interest are highly translucent, such as cells and tissues, with light transport lengths of many tens of microns up to hundreds of microns. Therefore, in microscopy of surface-supported cells and thin tissue culture, the optical contrast tends to be very low. On the other hand, cells and tissues have spatially nonuniform refractive indices and spatially varying geometries that lead to optical path length differences with phase that wraps around 2π several times. These large phase deviations provide the basis for phase contrast approaches to microscopic imaging. This may be accomplished in many different ways, including interference microscopy, differential interference contrast (DIC), and holography.
KeywordsOptical Coherence Tomography Gaussian Beam Differential Interference Contrast Reference Wave Quarter Wave Plate
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