Liquid crystal
If electrically tunable birefringent elements are inserted (liquid crystal or electrooptic), then we obtain an "Electrically Tunable Lyot Filter". Liquid crystal tunable filters allow analogue tuning of the transmitted wavelength by carefully adjusting the voltage over the liquid crystal cells. Often these filters are based on the original Lyot design, but many other designs exist in order to achieve either narrow or broad band transmission, polarization selectivity, etc.