Variable density optical filter

Claim 2

A thermo optic cell assembly, comprising: thermo optic cell means of the type containing a layer of liquid crystal material; interior and exterior cell walls, said layer of liquid crystal material located between said interior and exterior walls; first and second transparent electrode means located on opposite sides of said layer of liquid crystal material and generally parallel to and inside of said interior and exterior cell walls; means located in proximity to said thermo optic cell for providing heat to said layer of liquid crystal material in said thermo optic cell so that said layer of liquid crystal material is brought into an isotropic state and simultaneously maintained there; means for simultaneously and rapidly removing heat from said layer of liquid crystal material so that said layer undergoes a simultaneous and rapid cooling; and means connected to said transparent electrodes for simultaneously applying a uniform variable electric field of a sufficient magnitude and duration across said layer of liquid crystal material immediately after removal of said heat and while said layer of liquid crystal is simultaneously and rapidly cooling from said isotropic state to form a uniform variable background of scattering centers in said layer of liquid crystal material; wherein said assembly produces a uniform variable background of scattering centers which can vary in degree of uniform background darkness from a completely dark background of scattering centers to a clear background of scattering centers, including all degrees therebetween, based on said magnitude and duration of said simultaneously applied electric field during said simultaneous and rapid cooling of said layer of liquid crystal material from said isotropic state.

Claim 3

The assembly as in claim 1 wherein said liquid crystal material is heated by electrical means.

Claim 4

The assembly as in claim 1 wherein said liquid crystal material is heated by optical means.

Claim 5

The assembly as in claim 1 wherein said uniform variable electrical field is applied at a magnitude ranging from approximately 1-5 volts/micrometer and for a duration ranging from 50 to 5000 milliseconds.

Claim 6

A thermo optic cell assembly of the type including a layer of liquid crystal material bounded between transparent conductive electrodes, comprising: means located in close proximity to said thermo optic cell for providing heat to said layer of liquid crystal material so that said layer is heated to the isotropic state; and means for removing said heat rapidly and simultaneously so that said layer cools rapidly and simultaneously; means coupled to said transparent conductive electrodes for applying a variable, simultaneous, uniform electric field across an entire surface area of said layer of liquid crystal material while said layer of liquid crystal material rapidly and simultaneously cools from said isotropic state, said variable electric field being of a sufficiently variable magnitude and duration to produce a background of uniform scattering centers ranging from a completely clear background to a completely dark background and all levels therebetween.

Claim 7

A thermo optic cell assembly of the type including a layer of liquid crystal material bounded between transparent conductive electrodes, comprising: means located in close proximity to said thermo optic cell for providing heat to said layer of liquid crystal material so that said layer is heated to the isotropic state; and means for removing said heat rapidly and simultaneously so that said layer cools rapidly and simultaneously; means coupled to said transparent conductive electrodes for applying a variable, simultaneous, uniform electric field across an entire surface area of said layer of liquid crystal material while said layer of liquid crystal material rapidly and simultaneously cools from said isotropic state, said variable electric field being of a sufficiently variable magnitude and duration to produce a background of uniform scattering centers ranging from a completely clear background to a completely dark background and all levels therebetween.

Claim 8

The assembly as in claim 5 wherein said liquid crystal material is heated by applying electrical heating energy to one of said transparent conductive electrodes.

Claim 9

The assembly as in claim 5 wherein means are provided for applying optical energy to said liquid crystal material to heat the material.

Claim 12

The method of claim 8 wherein said step simultaneously applying a uniform variable electric field further comprises the steps of: applying said electric field for a duration ranging from 50 to 5000 milliseconds and at a magnitude ranging from 0.1 to 50 volts/millimeter.

Claim 13

The method as in claim 8 wherein the liquid crystal material is heated by electric heating.

Claim 14

The method as in claim 8 wherein the liquid crystal material is heated by optical means.

Claim 15

The method as in claim 8 when the electric field is applied simultaneously with the heating step, whereby the amount of electric field that is needed to modulate scattering is reduced thereby causing less stress to the cell and prolonging the life of the cell.

Claim 16

A thermo optic cell assembly, comprising: thermo optic cell means of the type containing a layer of liquid crystal material; interior and exterior cell walls, said layer of liquid crystal material located between said interior and exterior walls; first and second transparent electrode means located on opposite sides of said layer of liquid crystal material and generally parallel to and inside of said interior and exterior cell walls; means located in proximity to said thermo optic cell for providing heat to said layer of liquid crystal material in said thermo optic cell so that said layer of liquid crystal material is brought into an isotropic state and simultaneously maintained there; means for simultaneously and rapidly removing heat from said layer of liquid crystal material so that said layer undergoes a simultaneous and rapid cooling; and means connected to said transparent electrodes for simultaneously applying an electric field of a sufficient magnitude and duration across said layer of liquid crystal material immediately after removal of said heat and while said layer of liquid crystal is simultaneously and rapidly cooling from said isotropic state to form a uniform variable background of scattering centers in said layer of liquid crystal material; wherein said assembly produces a uniform variable background of scattering centers which can vary in degree of uniform background darkness from a completely dark background of scattering centers to a clear background of scattering centers, including all degrees therebetween, based on said magnitude and duration of said simultaneously applied electric field during said simultaneous and rapid cooling of said layer of liquid crystal material from said isotropic state; said electric field ranging from approximately 1 to 5 volts/micrometer and being applied for a period of time ranging from approximately 50 to 5000 milliseconds.

Claim 17

A thermo optic cell assembly, comprising: thermo optic cell means of the type containing a layer of liquid crystal material; interior and exterior cell walls, said layer of liquid crystal material located between said interior and exterior walls; first and second transparent electrode means located on opposite sides of said layer of liquid crystal material and generally parallel to and inside of said interior and exterior cell walls; means located in proximity to said thermo optic cell for providing heat to said layer of liquid crystal material in said thermo optic cell so that said layer of liquid crystal material is brought into an isotropic state and simultaneously maintained there; means for simultaneously and rapidly removing heat from said layer of liquid crystal material so that said layer undergoes a simultaneous and rapid cooling; and means connected to said transparent electrodes for simultaneously applying an electric field of a sufficient magnitude and duration across said layer of liquid crystal material immediately after removal of said heat and while said layer of liquid crystal is simultaneously and rapidly cooling from said isotropic state to form a uniform variable background of scattering centers in said layer of liquid crystal material; wherein said assembly produces a uniform variable background of scattering centers which can vary in degree of uniform background darkness from a completely dark background of scattering centers to a clear background of scattering centers, including all degrees therebetween, based on said magnitude and duration of said simultaneously applied electric field during said simultaneous and rapid cooling of said layer of liquid crystal material from said isotropic state; said electric field ranging from approximately 1 to 5 volts/micrometer and being applied for a period of time ranging from approximately 50 to 5000 milliseconds.