Diffractive light modulator
First Claim
1. An apparatus for modulating light comprising:
- first and second plates;
at least one birefringent layer disposed between said plates having first and second alignment regions, said birefringent layer corresponding to said first alignment region having a first optic axis selectably disposed in one of a first orientation and a second orientation, said birefringent layer corresponding to said second alignment region having a second optic axis selectably disposed in one of a third orientation and a fourth orientation, said first and third orientations having a relative difference of 90°
, and said first orientation having a same angle relative to a line perpendicular to said plates as said third orientation relative to said line, light having passed through said birefringent layer at locations with said first orientation having a phase difference of an odd-integral number of half-waves from and same polarization as light having passed through locations with said third orientation independent of a polarization state of light incident on said apparatus; and
means for controlling whether said first optic axis and said second optic axis are disposed to have said relative difference of 90°
, said first alignment region having a total area equal to a total area of said second alignment region, said phase difference between said first and third orientations causing complete diffraction of said light incident on said apparatus.
3 Assignments
0 Petitions
Accused Products
Abstract
An arrangement (apparatus and method) for selectively modulating incident unpolarized light passing through a birefringent material, such as ferroelectric crystal. The apparatus includes a plate having one or more birefringent layers corresponding to first and second alignment regions. The birefringent layer corresponding to the first alignment region has a first optic axis selectably set in a first orientation and a second orientation. The birefringent layer corresponding to the second alignment region has a second optic axis selectably set in a third orientation and a fourth orientation. A switching means controls the optical axis states of the birefringent material by applying switching voltages to the areas of the birefringent layer. Light having passed through the birefringent layer at locations having the first orientation has a different phase from, and same polarization as, light having passed through locations with the third orientation, independent of a polarization state of the incident light. As a result, the birefringent material has a uniform state at locations where the corresponding optic axes between the first and second alignment regions are parallel, and a diffracting state produced by an interaction between the light having passed through areas having the first orientation and the light having passed through areas having the second orientation. The arrangement is effective for reflective modulators, multilayer modulators or polarization-preserving modulators, and has applications for intensity modulation, blurring modulation and beam steering.
72 Citations
30 Claims
-
1. An apparatus for modulating light comprising:
-
first and second plates; at least one birefringent layer disposed between said plates having first and second alignment regions, said birefringent layer corresponding to said first alignment region having a first optic axis selectably disposed in one of a first orientation and a second orientation, said birefringent layer corresponding to said second alignment region having a second optic axis selectably disposed in one of a third orientation and a fourth orientation, said first and third orientations having a relative difference of 90°
, and said first orientation having a same angle relative to a line perpendicular to said plates as said third orientation relative to said line, light having passed through said birefringent layer at locations with said first orientation having a phase difference of an odd-integral number of half-waves from and same polarization as light having passed through locations with said third orientation independent of a polarization state of light incident on said apparatus; andmeans for controlling whether said first optic axis and said second optic axis are disposed to have said relative difference of 90°
, said first alignment region having a total area equal to a total area of said second alignment region, said phase difference between said first and third orientations causing complete diffraction of said light incident on said apparatus. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
-
-
16. An intensity modulator comprising:
-
means for collecting incident light having a predetermined optical spread; a modulator for modulating the collected light, the modulator comprising; first and second plates, at least one birefringent layer disposed between said plates having an optic axis selectably disposed in one of a first orientation and a second orientation, said first and second orientations of said optic axis having a same angle to a perpendicular of said plates, light having passed through said birefringent layer at locations with said first orientation having a different phase from and same polarization as light having passed through locations with said second orientation independent of a polarization state of said incident light, and means for controlling whether said optic axis is in said first or second orientation, diffraction being produced by an interaction between light having passed through areas having said first orientation and light having passed through areas having said second orientation; and means for selectively passing and stopping said light having passed through said modulator in response to said diffraction; wherein said means for selectively passing and stopping comprises a beam stop disposed to stop the collected light passing through the modulator when said diffraction is not produced and to pass light passing through the modulator when said diffraction is produced.
-
-
17. An intensity modulator comprising:
-
means for collecting incident light having a predetermined optical spread; a modulator for modulating the collected light, the modulator comprising; first and second plates, at least one birefringent layer disposed between said plates having an optic axis selectably disposed in one of a first orientation and a second orientation, said first and second orientations of said optic axis having a same angle to a perpendicular of said plates, light having passed through said birefringent layer at locations with said first orientation having a different phase from and same polarization as light having passed through locations with said second orientation independent of a polarization state of said incident light, and means for controlling whether said optic axis is in said first or second orientation, diffraction being produced by an interaction between light having passed through areas having said first orientation and light having passed through areas having said second orientation; and means for selectively passing and stopping said light having passed through said modulator in response to said diffraction; wherein; said first and second orientations have a relative difference of 90°
, said phase difference between said light having passed through said locations with said first orientation and said light having passed through said locations with said second orientation being an odd-integral number of half-waves; andsaid birefringent layer has at least two regions, one of said two regions corresponding to a first region type and another of said two regions corresponding to a second region type, said regions corresponding to said first region type having a total area equal to a total area of regions corresponding to said second region type, said phase difference between said first and second orientations causing complete diffraction of said light incident on said modulator.
-
-
18. An intensity modulator comprising:
-
means for collecting incident light having a predetermined optical spread; a modulator for modulating the collected light, the modulator comprising; first and second plates, at least one birefringent layer disposed between said plates having first and second alignment regions, said birefringent layer corresponding to said first alignment region having a first optic axis selectably disposed in one of a first orientation and a second orientation, said birefringent layer corresponding to said second alignment region having a second optic axis selectably disposed in one of a third orientation and a fourth orientation, said first orientation having a same angle relative to a line perpendicular to said plates as said third orientation relative to said line, light having passed through said birefringent layer at locations with said first orientation having a different phase from and same polarization as light having passed through locations with said third orientation independent of a polarization state of said collected light, and means for controlling whether said first and second optic axes are in said first and third orientations, respectively, diffraction being produced by an interaction between light having passed through areas having said first orientation and light having passed through areas having said third orientation; and means for selectively passing and stopping said light having passed through said modulator in response to said diffraction. - View Dependent Claims (19, 20)
-
-
21. A blurring modulator comprising:
-
means for collecting incident light; a modulator for modulating the collected incident light, the modulator comprising; first and second plates; at least one birefringent layer disposed between said plates having first and second alignment regions, said birefringent layer corresponding to said first alignment region having a first optic axis selectably disposed in one of a first orientation and a second orientation, said birefringent layer corresponding to said second alignment region having a second optic axis selectably disposed in one of a third orientation and a fourth orientation, said first orientation having a same angle relative to a line perpendicular to said plates as said third orientation relative to said line, light having passed through said birefringent layer at locations with said first orientation having a different phase from and same polarization as light having passed through locations with said third orientation independent of a polarization state of light incident on said blurring modulator; and means for controlling whether said first and second optic axes are in said first and third orientation, respectively, diffraction being produced by an interaction between light having passed through areas having said first orientation and light having passed through areas having said third orientation; and means for detecting the collected light passing through the modulator, said detector detecting a distorted image when said diffraction is produced. - View Dependent Claims (22, 23)
-
-
24. A method for modulating light comprising the steps of:
-
passing a light through first and second plates each having first and second alignment regions and at least one birefringent layer disposed between said plates, said birefringent layer corresponding to said first alignment region having a first optic axis selectably disposed in one of a first orientation and a second orientation, said birefringent layer corresponding to said second alignment region having a second optic axis selectably disposed in one of a third orientation and a fourth orientation, said first orientation having a relative difference of 90° and
having a same angle relative to a line perpendicular to said plates as said third orientation relative to said line, light having passed through said birefringent layer at locations with said first orientation having a phase difference of an odd-integral number of half-waves from and same polarization as light having passed through locations with said third orientation independent of a polarization state of said incident light;selectively aligning said optic axes of said first and second alignment regions to said second and fourth orientations respectively to generate a uniform state; and selectively aligning said optic axes of said first and second alignment regions to have said relative difference of ninety degrees to retard said light having passed through said first alignment regions by substantially an odd integral number of half-waves relative to said light having passed through said second alignment regions, thereby generating said completely diffracting state. - View Dependent Claims (25, 26)
-
-
27. A beam steering device for diffracting incident light, comprising:
-
first and second plates; at least one birefringent layer disposed between said plates having first and second alignment regions, said birefringent layer corresponding to said first alignment region having a first optic axis selectably disposed in one of a first orientation and a second orientation, said birefringent layer corresponding to said second alignment region having a second optic axis selectably disposed in one of a third orientation and a fourth orientation, said first orientation having a same angle relative to a line perpendicular to said plates as said third orientation relative to said line, light having passed through said birefringent layer at locations with said first orientation having a different phase from and same polarization as light having passed through locations with said third orientation independent of a polarization state of light incident on said apparatus; and means for controlling whether said first and second optic axes are in said first and third orientations, respectively, said controlling means defining a diffraction grating comprising a plurality of strips each having a spatial period, said plurality of strips alternately having said first and second alignment regions, said spatial period being controllable by said controlling means, said incident light being diffracted at an angle in accordance with said spatial period. - View Dependent Claims (28, 29, 30)
-
Specification