Split-element liquid crystal tunable optical filter
First Claim
1. A liquid crystal split-element optical filter comprising one or more stages optically coupled in series wherein at least one stage comprises:
- a first polarizer;
a second polarizer oriented parallel or perpendicular to said first polarizer;
a center retarder unit positioned between said first and second polarizers, and comprising one or more retarders and having a composite retardance oriented parallel or perpendicular to said first polarizer;
a first split-element retarder unit, positioned between said first polarizer and said center retarder unit, and comprising a first split-element retarder, oriented at ±
π
/4 with respect to said first polarizer; and
a second split-element retarder unit, positioned between said center retarder unit and said second polarizer, and comprising a second split-element retarder of equal retardance to said first split-element retarder and oriented at ±
π
/4 with respect to said first polarizer;
wherein at least one of said retarder units comprises a first liquid crystal retarder, said first liquid crystal retarder having a fixed retardance and having an optic axis rotatable between a first orientation and a second orientation.
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Accused Products
Abstract
This invention provides split-element liquid crystal polarization interference filters in wide-field, bandpass, cut-on, cut-off and notch filter embodiments. The split-element filters of this invention comprise a polarization interference stage defined by a pair of polarizers. Disposed within the stage are a center retarder, and first and a second split-element retarder, the split-element retarders having equal retardances and positioned in series with and on either side of the center retarder. The retarders can be liquid crystal variable retarders or can be fixed retarders used in combination with liquid crystal retarders. Double split-element filters in passive and tunable embodiments are provided comprising, within a polarization interference stage, a center retarder, an inside pair of split-element retarders and an outside pair of split-element retarders.
140 Citations
51 Claims
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1. A liquid crystal split-element optical filter comprising one or more stages optically coupled in series wherein at least one stage comprises:
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a first polarizer; a second polarizer oriented parallel or perpendicular to said first polarizer; a center retarder unit positioned between said first and second polarizers, and comprising one or more retarders and having a composite retardance oriented parallel or perpendicular to said first polarizer; a first split-element retarder unit, positioned between said first polarizer and said center retarder unit, and comprising a first split-element retarder, oriented at ±
π
/4 with respect to said first polarizer; anda second split-element retarder unit, positioned between said center retarder unit and said second polarizer, and comprising a second split-element retarder of equal retardance to said first split-element retarder and oriented at ±
π
/4 with respect to said first polarizer;wherein at least one of said retarder units comprises a first liquid crystal retarder, said first liquid crystal retarder having a fixed retardance and having an optic axis rotatable between a first orientation and a second orientation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38)
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39. A double split-element optical filter comprising one or more stages optically coupled in series wherein at least one stage comprises:
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a first polarizer; a second polarizer, oriented parallel or perpendicular to said first polarizer; a center retarder oriented at ±
π
/4 to said first polarizer, and positioned between said first and second polarizers;a first inner-split-element retarder, oriented parallel or perpendicular to said first polarizer, and positioned between said first polarizer and said center retarder; a second inner-split-element retarder, of equal retardance to said first inner-split-element retarder, oriented parallel or perpendicular to said first polarizer, and positioned between said center retarder and said second polarizer; a first outer-split-element retarder, oriented at ±
π
/4 with respect to said first polarizer, and positioned between said first polarizer and said first inner-split-element retarder; anda second outer-split-element retarder, of equal retardance to said first outer-split-element retarder, oriented at ±
π
/4 with respect to said first polarizer and positioned between said second inner-split-element retarder and said second polarizer. - View Dependent Claims (40, 41, 42, 43, 44, 45, 46, 47, 48, 49)
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50. A reflection-mode split-element filter comprising:
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a polarizer; a reflector; a center retarder unit positioned between said polarizer and said reflector, and comprising one or more retarders and having a composite retardance oriented parallel or perpendicular to said polarizer; and a split-element retarder unit, positioned between said polarizer and said center retarder unit, and comprising a split-element retarder, oriented at ±
π
/4 with respect to said polarizer;wherein at least one of said retarder units comprises a liquid crystal retarder, said liquid crystal retarder having a fixed retardance and having an optic axis rotatable between a first and a second orientation.
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51. A liquid crystal split-element optical filter comprising one or more stages optically coupled in series wherein at least one stage comprises:
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a first polarizer; a second polarizer oriented parallel or perpendicular to said first polarizer; a center retarder unit positioned between said first and second polarizers, and comprising one or more retarders and having a composite retardance oriented parallel or perpendicular to said first polarizer; a first split-element retarder unit, positioned between said first polarizer and said center retarder unit, and comprising a first split-element retarder, oriented at ±
π
/4 with respect to said first polarizer;a second split-element retarder unit, positioned between said center retarder unit and said second polarizer, and comprising a second split-element retarder of equal retardance to said first split-element retarder and oriented at ±
π
/4 with respect to said first polarizer; anda liquid crystal means, positioned between said second split-element retarder unit and said second polarizer, for adding a half-wave of retardance and thereby reversing the locations of transmission maxima and minima; wherein at least one of said retarder units comprises a first liquid crystal retarder, said first liquid crystal retarder having a fixed retardance and having an optic axis rotatable between a first orientation and a second orientation.
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Specification