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A phase plate is an optical mechanism that changes the phase of light (e.g., infrared or visible light) passing through. Some make use of liquid crystals to give light a circular polarization. Phase plates have been used in modern-design coronagraphs as steps in the elimination of the light that the coronagraph aims to block. Essentially, light from the source is canceled on portions of the focal plane through splitting the beam, manipulating both the phases and polarization and subsequently recombining: waves of equal amplitude but opposite phase cancel.