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Chiral smectic liquid crystal optical modulators having variable retardation

  • US 5,381,253 A
  • Filed: 11/14/1991
  • Issued: 01/10/1995
  • Est. Priority Date: 11/14/1991
  • Status: Expired due to Fees
First Claim
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1. A variable retarder for elliptically polarized light comprising:

  • a first half-wave plate comprising a first planar-aligned chiral smectic liquid crystal cell, said cell having a rotatable optic axis;

    means for applying an electric field across said liquid crystal cell to rotate said optic axis; and

    first and second quarter-wave plates positioned in series with and on either side of said half-wave plate, the optic axes of said quarter-wave plates oriented parallel or perpendicular to each other;

    wherein the combination of said half-wave plate with said quarter-wave plates produces a retardance which is varied by rotation of said rotatable optic axis; and

    wherein the polarization of said incoming light may be oriented at any angle with respect to the optic axis of said first quarter-wave plate, except for linearly polarized light oriented at ±

    45°

    .

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