We discuss tunable birefringent filters utilizing liquid crystals. We have incorporated nematic liquid crystals, manufactured as electrically variable, true zero-order retarders, in Lyot and Solc filter designs to allow continuous spectral tunability. The performance characteristics and design enhancements of several assembled tunable filters are discussed. These range from narrow band (0.13 nm) filters for solar imaging to wide field of view filters for airborne remote sensing spanning the spectral range 400 - 2500 nm. Design considerations for improving field of view, speed, and transmission of liquid crystal tunable filters are discussed.
|