Liquid crystal tunable birefringent filters

We discuss the design of tunable birefringent filters utilizing liquid crystals. The performance of several assembled filters is presented. We have incorporated nematic liquid crystals in Lyot and Solc filter designs to allow continuous spectral tunability. Liquid crystals can be manufactured as electrically variable retarders in the visible and near infrared spectral regions, and can provide filter tuning times as short as 20 msec. The performance characteristics and design enhancements of assembled tunable filters for diverse applications are discussed. These include: solar imaging in the near infrared with a narrow band (0.13 nm) filter; imaging florescence microscopy in the visible with a fast tuning filter; and airborne remote sensing over the 400-2500 nm spectral range with wide field of view filters. Design considerations for improving speed, field of view, transmission and contrast of liquid crystal tunable filters are discussed.