Multiple-stage liquid crystal tuned filter

A voltage controlled multiple-stage tunable filter with broad continuous tuning range was studied in theory and experiment. Four liquid crystal retarders, two quartz plates with certain integral ratio phase retardations and five polarization films were assembled into a traditional Lyot filter. The tunable function was achieved by using the electro-birefringence effect of liquid crystal. The result of numerical simulation showed that the spectral resolution was ∼10 nm around bands of 500–700 nm; side forms rejection ratio and FWHM changed in contrast to considering and not considering the birefringence dispersion effect of liquid crystal and quartz; the shape of filtered light displayed by spectral photometer would be affected by spectrum bands of light source in spectral photometer. A four-stage tunable filter was made and tested, experiment results agreed with the numerical simulation results very well, the research results could be applied as reference for the study of broad spectrum tunable filters.