| 摘要 |
<p>The present invention is an optical retarder comprising a liquid crystal variable retardance cell having substrates (2) on either side thereof, each substrate having a transparent electrode (3) on its inner face, a nematic phase liquid crystal material (9) between the substrates (2), means for applying a drive voltage to the transparent electrode (3), means for sensing the capacitance of the liquid crystal cell and means for determining the retardance of the cell corresponding to the sense capacitance thereof. A tunable hybrid element comprising such an optical retarder in combination with a fixed retardance element (1) is also disclosed. Also disclosed is a tunable Lyot filter based on multiple hybrid retardance elements.</p> |
