Chiral smectic liquid crystal polarization interference filters
First Claim
1. A tunable optical filter comprising one or more stages optically coupled in sequence wherein a stage comprises an entrance polarizer which defines the polarization of light entering the stage and an exit polarizer which is oriented at a fixed angle with respect to the entrance polarizer, wherein at least one stage of said filter comprises a fixed birefringent element optically coupled with a chiral smectic liquid crystal cell between said polarizers, said chiral smectic liquid crystal cell having two or more optic axis orientations, and electric field production means electromagnetically coupled with said chiral smectic liquid crystal cell for rotating the optic axis of said cell among said optic axis orientations to tune the spectral filtering of said light entering the stage.
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Abstract
Discretely and continuously tunable single and multiple-stage polarization interference filters employing chiral smectic liquid crystal cells as electronically rotatable retarders are provided. Discretely tunable filters of this invention include those which employ bistable surface-stabilized ferroelectric liquid crystal cells. Continuously tunable filters of this invention include those that employ chiral smectic A ferroelectric liquid crystal cells. Single stage filters include fixed birefringent elements in combination with chiral smectic liquid crystal cells and multiple stage filters can include only chiral smectic liquid crystal cells or can include chiral smectic liquid crystal cells in combination with fixed birefringent elements. Blocking filters useful for color generation and color displays are also provided. The FLC filters provided can be temporally multiplexed.
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Citations
33 Claims
- 1. A tunable optical filter comprising one or more stages optically coupled in sequence wherein a stage comprises an entrance polarizer which defines the polarization of light entering the stage and an exit polarizer which is oriented at a fixed angle with respect to the entrance polarizer, wherein at least one stage of said filter comprises a fixed birefringent element optically coupled with a chiral smectic liquid crystal cell between said polarizers, said chiral smectic liquid crystal cell having two or more optic axis orientations, and electric field production means electromagnetically coupled with said chiral smectic liquid crystal cell for rotating the optic axis of said cell among said optic axis orientations to tune the spectral filtering of said light entering the stage.
- 20. A tunable optical filter comprising one or more optically coupled stages along a light propagation axis wherein a stage comprises an entrance polarizer and an exit polarizer which are oriented at a fixed angle with respect to each other, wherein the entrance polarizer of a stage defines the polarization of light entering that stage wherein one or more stages of said filter comprise N chiral smectic liquid crystal cells positioned between said polarizers and optically coupled with said polarizers said chiral smectic liquid crystal cell having two or more optical axis orientations and means for applying an electric field to said chiral smectic liquid crystal cell whereby said optic axis of said cell is rotated among said optical axis orientations wherein, when the filter has one stage, N is three or more, and when the filter has more than one stage, N is one or more.
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23. A continuously tunable optical filter having one or more optically coupled stages wherein a stage comprises:
- an entrance polarizer which defines the polarization of light entering the stage and an exit polarizer which is oriented at a fixed angle with respect to the polarization of light entering the stage, a birefringent element which can be active or fixed, an achromatic quarter-waveplate and an analog chiral smectic liquid crystal cell all of which are optically coupled between said polarizers wherein said achromatic quarter-waveplate is optically coupled between said birefringent element and said analog chiral smectic liquid crystal cell and means for applying a variable electric field to said analog chiral smectic liquid crystal cell such that the optic axis of said cell be rotated with the magnitude of said rotation being dependent on the sign and magnitude of said applied field and α
MAX of said analog chiral smectic cell. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
- an entrance polarizer which defines the polarization of light entering the stage and an exit polarizer which is oriented at a fixed angle with respect to the polarization of light entering the stage, a birefringent element which can be active or fixed, an achromatic quarter-waveplate and an analog chiral smectic liquid crystal cell all of which are optically coupled between said polarizers wherein said achromatic quarter-waveplate is optically coupled between said birefringent element and said analog chiral smectic liquid crystal cell and means for applying a variable electric field to said analog chiral smectic liquid crystal cell such that the optic axis of said cell be rotated with the magnitude of said rotation being dependent on the sign and magnitude of said applied field and α
Specification