Apparatus and Method for Dynamically Controlling Light Transmission

Abstract

An apparatus for controlling light transmission from an optical input to an optical output can function as a tunable iris or eclipse, or as a privacy window. The iris/eclipse can use a liquid crystal matrix with a dispersion of dichroic particles that absorb light in one orientation and transmit light in another, such that controlling the liquid crystal with an electric field allows control of the dichroic particles. Alternatively, a layer may be used with a light absorbing liquid or powder material that moves with a charged material in response to a variable electric field applied to the layer. Privacy windows use a plurality of liquid crystal microlenses that can be controlled with an electric field to allow an image of an optical input to be obtainable at an optical output when in a first state, or to render the image irretrievable when in a second state.

1 . An apparatus for controlling the cross-sectional area of a transmitting region through which light may pass from an optical input to an optical output, the apparatus comprising:
 a liquid crystal orienting matrix layer located between the optical input and the optical output;   a plurality of dichroic particles that are dispersed in the liquid crystal matrix and that are each reoriented with reorientation of proximate molecules of the liquid crystal matrix, the dichroic particles having a first orientation in which they cause no significant obstruction of light between the optical input and the optical output and a second orientation in which they create significant obstruction of light between the optical input and the optical output; and   an electric field generator that provides an electric field across the liquid crystal layer, a spatial profile of the electric field being dynamically variable such that the electric field has a spatially non-uniform field strength that causes a reorientation of liquid crystal molecules predominantly within a predetermined cross-sectional area of the liquid crystal layer.   
     
     
         2 . An apparatus according to  claim 1  wherein the electric field generator comprises a spatially uniform electrode and a spatially non-uniform electrode. 
     
     
         3 . An apparatus according to  claim 2  wherein the electric field generator comprises a frequency dependent material by which an effective shape of the non-uniform electrode may be modified by changing the frequency of an electrical signal applied to the electrodes. 
     
     
         4 . An apparatus according to  claim 1  further comprising an optically transparent supporting substrate to which the liquid crystal layer and the electric field generator are secured. 
     
     
         5 . An apparatus according to  claim 1  wherein said predetermined cross-sectional area is one of a variable iris and a variable eclipse. 
     
     
         6 . (canceled) 
     
     
         7 . An apparatus according to  claim 1  wherein the liquid crystal orienting matrix and the plurality of dichroic particles form a first controllable cell for which the dichroic particles may be controlled to provide variable obstruction of a first portion of the light passing from the optical input to the optical output, said first light portion having a first polarization, and wherein the apparatus further comprises a second controllable cell that includes a liquid crystal orienting matrix and a plurality of dichroic particles that may be controlled to provide variable obstruction of a second portion of said light, said second light portion having a second polarization perpendicular to the first polarization. 
     
     
         8 . An apparatus according to  claim 1  wherein said obstruction of light by the dichroic particles is limited to a predetermined wavelength range outside of which the dichroic particles allow a relatively higher degree of light transmission. 
     
     
         9 . An apparatus according to  claim 8  wherein the plurality of dichroic particles is a plurality of a first type of dichroic particles that have a first predetermined wavelength range of light obstruction and wherein the apparatus further comprises a plurality of a second type of dichroic particles that have a second predetermined wavelength range of light obstruction different than that of the first type. 
     
     
         10 . An apparatus according to  claim 9  wherein the dichroic particles of the first type and the dichroic particles of the second type are dispersed in the same liquid crystal orienting matrix according to a predetermined ratio. 
     
     
         11 . An apparatus according to  claim 1  wherein the dichroic particles comprise carbon nanotubes. 
     
     
         12 .- 25 . (canceled) 
     
     
         26 . A method of controlling the cross-sectional area of a transmitting region through which light may pass from an optical input to an optical output, the method comprising:
 providing a liquid crystal orienting matrix layer located between the optical input and the optical output, the liquid crystal having dispersed within it a plurality of dichroic particles that are each reoriented with reorientation of proximate molecules of the liquid crystal matrix, the dichroic particles having a first orientation in which they cause no significant obstruction of light between the optical input and the optical output and a second orientation in which they create significant obstruction of light between the optical input and the optical output; and   reorienting molecules of the liquid crystal layer with an electric field having a spatial profile that is dynamically variable such that the electric field has a spatially dependent field strength that causes a reorientation of liquid crystal molecules only within a predetermined cross-sectional area of the liquid crystal layer.   
     
     
         27 . A method according to  claim 26  wherein the electric field is generated with an electric field generator that comprises a spatially uniform electrode and a spatially non-uniform electrode. 
     
     
         28 . A method according to  claim 27  wherein the electric field generator comprises a frequency dependent material by which an effective shape of the non-uniform electrode may be modified by changing the frequency of an electrical signal applied to the electrodes. 
     
     
         29 . A method according to  claim 26  wherein the liquid crystal layer and the electric field generator are secured to a transparent supporting substrate. 
     
     
         30 . A method according to  claim 26  wherein said predetermined cross-sectional area is one of a variable iris and a variable eclipse. 
     
     
         31 . (canceled) 
     
     
         32 . A method according to  claim 26  wherein the liquid crystal orienting matrix and the plurality of dichroic particles form a first controllable cell for which the dichroic particles may be controlled to provide variable obstruction of a first portion of the light passing from the optical input to the optical output, said first light portion having a first polarization, and wherein the method further comprises providing a second controllable cell that includes a liquid crystal orienting matrix and a plurality of dichroic particles that may be controlled to provide variable obstruction of a second portion of said light, said second light portion having a second polarization perpendicular to the first polarization. 
     
     
         33 . A method according to  claim 26  wherein said obstruction of light by the dichroic particles is limited to a predetermined wavelength range outside of which the dichroic particles allow a relatively higher degree of light transmission. 
     
     
         34 . A method according to  claim 33  wherein the plurality of dichroic particles is a plurality of a first type of dichroic particles that have a first predetermined wavelength range of light obstruction and wherein the method further comprises a plurality of a second type of dichroic particles that have a second predetermined wavelength range of light obstruction different than that of the first type. 
     
     
         35 . A method according to  claim 34  wherein the dichroic particles of the first type and the dichroic particles of the second type are dispersed in the same liquid crystal orienting matrix according to a predetermined ratio. 
     
     
         36 . A method according to  claim 26  wherein the dichroic particles comprise carbon nanotubes. 
     
     
         37 .- 50 . (canceled)