Modulation contrast system

The common contrast modes include polarized light, phase contrast, differential interference contrast, and Hoffman modulation contrast [5]. Depending on the nature of the polymer, such as refraction index, sample thickness, and optical anisotropies in the materials, different modes of transmission optical microscopy can be employed by mounting special accessories in a classic optical microscope to overcome different problems. For example, a polarizer and analyzer can be mounted before and after the sample to construct a polarized light microscope, commonly used for semicrystalline polymers a phase plate and phase ring can be added to construct a phase contrast optical microscopy, which is common for studying a noncrystafline multiphase polymer system. 

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