Diffractive light modulator

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
• first means for controlling whether said optic axis is in said first or second orientation at a first area of said birefringent layer, 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
• an aperture having a radius r and being disposed so as to pass the collected light passing through the modulator when said diffraction is not produced.

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 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
• first means for controlling whether said optic axis is in said first or second orientation at a first area of said birefringent layer, 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 detecting the collected light passing through the modulator, said detector detecting a distorted image when said diffraction is produced.

A method for modulating light comprising the steps of:

• passing a light through a plate, said plate comprising a plurality of first and second regions, each having equal areas, said plate selectively having a uniform state and a completely diffracting state, said first and second regions each having a birefringent layer having an optic axis selectably disposed in one of a first and second orientation, said first orientation and second orientation both having a same angle to a perpendicular to said plane;
• selectively aligning said optic axes of said first and second regions to said first orientation to generate said uniform state;
• and
• selectively aligning said optic axes of said first and second regions to said first and second orientations, respectively, said first and second orientations having a relative difference of ninety degrees to retard said light having passed through said first regions by substantially an odd integral number of half-waves relative to said light having passed through said second regions, thereby generating said completely diffracting state.

An apparatus for modulating incident light comprising:

• first and second plates;
• a first birefringent layer disposed between said plates and having a first 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;
• a second birefringent layer disposed between said first birefringent layer and said second plate and having a different alignment direction relative to said first birefringent layer and a second optic axis selectably disposed in one of a third orientation and a fourth orientation;
• first means for controlling whether said first optic axis is in said first or second orientation at a first area of said first birefringent layer;
• and
• second means for controlling whether said second optic axis is in said third or fourth orientation at a second area of said second birefringent layer;
• said first and second birefringent layers being arranged to provide a first and second strips, said first strip comprising said first area of said first birefringent layer and a corresponding area of said second birefringent layer, said second strip comprising another area of said first birefringent layer and a corresponding another area of said second birefringent layer, said second area of said second birefringent layer being part of either said first strip or said second strip, light having passed through said first strips having a different phase from and same polarization as light having passed through said second strips when said first and second strips have different states, thereby producing diffraction, said states of said first and second strips being determined by said first, second, third and fourth orientations.

An apparatus for modulating incident light comprising:

• first and second plates, said second plate having a reflective surface facing said first plate;
• a passive waveplate disposed between said first plate and said reflective surface of said second plate, said waveplate having a thickness retarding light having passed once through said passive waveplate by substantially an odd integral number of quarter-waves with respect to a center of an operating wavelength of said light, said passive waveplate having a predetermined optical orientation;
• a birefringent layer disposed between said first plate and said passive plate and 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, said optical orientation of said passive waveplate bisecting said first and second orientations of said optic axis, said birefringent layer having a thickness retarding light having passed once through said birefringent layer by substantially an odd integral number of half-waves with respect to a center of an operating wavelength of said light, 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 orientations independent of a polarization state of said incident light;
• and
• first means for controlling whether said optic axis is in said first or second orientation at a first area of said birefringent layer;
• wherein light having passed once through said birefringent layer is reflected back from said reflective surface and passes through said birefringent layer a second time;
• wherein diffraction is produced by an interaction between light having passed through areas having said first orientation and light having passed through areas having said second orientation.

A beam steering device for diffracting incident light, 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 within said birefringent layer, 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 or second orientation, said spatial period being controllable by said controlling means, said incident light being diffracted at an angle in accordance with said spatial period.