| 摘要 |
<p>The present invention provides optical polarization interference filters (20) which employ chiral smectic liquid crystal (CSLC) cells (FLC1, FLC2, FLC3) as electronically rotatable retarders. The filters of the present invention are improved in that they are optimized for increased spectral discrimination, uniqueness of spectral outputs and efficient use of CSLC elements (FLC1, FLC2, FLC3). The filters of the present invention includes improved single and multiple stage filters. Improved discretely tunable and continuously tunable filters are provided. With respect to filters having one or more stages that contain a series of birefringent elements which are either fixed birefringent elements or active CSLC cells (FLC1, FLC2, FLC3), this invention provides designs which optimize the number of pure spectral outputs which are unique. This optimization relates to the relative order of elements in a stage, the pattern of switching of the active CSLC cells (FLC1, FLC2, FLC3), and the retardations of the CSCL cells (FLC1, FLC2, FLC3) in a stage. In a specific embodiment, this invention provides an improved tunable filter that substantially retains the transmissions of a Lyot-type multiple stage filter without requiring the thicknesses of the active CSLC cells to increase geometrically. Continuously tunable filters (60, 90) of this invention include those having a stage which has an analog variable retarder which is the combination of an achromatic quarter-waveplate (65) and one or more analog CSLC cells in series.</p> |
