Switchable achromatic compound retarder
First Claim
1. An achromatic compound retarder, comprising:
- a first passive retarder unit having a predetermined retardance at a design wavelength and having a predetermined optic axis orientation;
a second passive retarder unit having the predetermined retardance at the design wavelength and having substantially the same predetermined optic axis orientation as the first passive retarder unit; and
a central retarder unit positioned between the first and second passive retarder units, the central retarder unit having a retardance of approximately π
at the design wavelength and an optic axis orientation switchable between at least a first orientation state and a second orientation state,wherein the compound retardance is substantially achromatic when the optic axis of the central retarder unit is in the first orientation state.
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Accused Products
Abstract
This invention provides achromatic liquid crystal compound retarders, achromatic polarization switches, and achromatic shutters using the liquid crystal compound retarders. It further provides achromatic variable retardance smectic liquid crystal retarders. The compound retarder of this invention comprises a central liquid crystal retarder unit and two external passive retarders positioned in series with and on either side of the liquid crystal retarder unit. The liquid crystal retarder unit comprises either (1) a rotatable smectic liquid crystal half-wave retarder or (2) first and second liquid crystal variable retarders having retardance switchable between zero and half-wave. The external passive retarders are equal in retardance and orientation to each other. Design equations determine the retardance of the external elements and their orientation relative to the central retarder to obtain a particular achromatic retardance for the compound structure.
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Citations
26 Claims
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1. An achromatic compound retarder, comprising:
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a first passive retarder unit having a predetermined retardance at a design wavelength and having a predetermined optic axis orientation; a second passive retarder unit having the predetermined retardance at the design wavelength and having substantially the same predetermined optic axis orientation as the first passive retarder unit; and a central retarder unit positioned between the first and second passive retarder units, the central retarder unit having a retardance of approximately π
at the design wavelength and an optic axis orientation switchable between at least a first orientation state and a second orientation state,wherein the compound retardance is substantially achromatic when the optic axis of the central retarder unit is in the first orientation state. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. An achromatic compound retarder, comprising:
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a passive retarder unit having a predetermined retardance at a design wavelength and having a predetermined optic axis orientation; a reflector; and a central retarder unit positioned between the passive retarder unit and the reflector, the central retarder unit having a retardance of approximately π
/2 at the design wavelength and an optic axis orientation switchable between at least a first orientation state and a second orientation state,wherein the compound retardance is substantially achromatic when the optic axis of the central retarder unit is in the first orientation state. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. A method of imparting an achromatic retardance on a light beam, comprising:
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passing the light beam through a first passive retarder unit having a predetermined retardance at a design wavelength and having a predetermined optic axis orientation; passing the light beam through a central retarder unit at least once, the central retarder unit having an optic axis orientation switchable between at least a first orientation state and a second orientation state; and passing the light beam through one of the first passive retarder unit and a second passive retarder unit having the predetermined retardance at the design wavelength and having substantially the same predetermined optic axis orientation as the first passive retarder unit, wherein the retardance of the central retarder unit at the design wavelength is π
divided by the number of passes the light beam makes through the central retarder unit, and the retardance imparted on the light beam is substantially achromatic when the central retarder unit is in the first orientation state. - View Dependent Claims (25)
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26. An achromatic compound retarder, comprising:
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means for passing a light beam through a first passive retarder unit having a predetermined retardance at a design wavelength and having a predetermined optic axis orientation; means for passing the light beam through a central retarder unit at least once, the central retarder unit having an optic axis orientation switchable between at least a first orientation state and a second orientation state; and means for passing the light beam through one of the first passive retarder unit and a second passive retarder unit having the predetermined retardance at the design wavelength and having substantially the same predetermined optic axis orientation as the first passive retarder unit, wherein the retardance of the central retarder unit at the design wavelength is π
divided by the number of passes the light beam makes through the central retarder unit, and the retardance imparted on the light-beam is substantially achromatic when the central retarder unit is in the first orientation state.
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Specification