Novel Polarization Interference Filters for Wide Spectral Tuning of an Optical Null
Published in SPIE Proceedings Volume 5289, Liquid Crystal Materials, Devices, and Applications X and Projection Displays X; (2004) https://doi.org/10.1117/12.532868
Novel tunable polarization interference filters (PIF) employing active liquid crystal devices are presented, and the principles of operation are described. Filter designs are presented based on a requirement for tunable nulls in the visible and near infrared spectral regions of high optical density, for protection from intense electromagnetic radiation outside of the spectral range of interest which can saturate an imaging or sensor system. Two types of PIFs are presented with their modeled results and device performances. Analog filters in a generalized Lyot-Ohmann geometry are presented which are capable of tuning an optical null through 260 nm, by employing a single active device per filter stage. Binary filters are also presented which can switch between two complimentary and non-overlapping spectral states. Both types of filter can operate in a "normally on" state with a broadband "white light" throughput.