Directional backlight with a modulation layer

1. A directional backlight, comprising:

a directional backplane comprising a slab of transparent material configured to guide a plurality of input planar lightbeams, the directional backplane having a plurality of directional pixels configured to scatter a portion of the guided input planar lightbeams out of a surface of the transparent material slab into a plurality of directional lightbeams corresponding to directions of different views of a three-dimensional (3D) image, each directional lightbeam having a direction and angular spread controlled by characteristics of a directional pixel in the plurality of directional pixels; and

a modulation layer having a plurality of modulators configured to modulate the plurality of directional lightbeams,

wherein a directional pixel of the plurality of directional pixels comprises a patterned grating one or both of in and on the surface of the transparent material slab.

2. The directional backlight of claim 1 , further comprising a spacer layer positioned above the directional backplane.

3. The directional backlight of claim 2 , wherein the modulation layer is positioned above the spacer layer.

4. The directional backlight of claim 1 , wherein the transparent material slab of the directional backplane is substantially planar, the plurality of input planar lightbeams being configured to propagate within a plane of the substantially planar transparent material slab.

5. The directional backlight of claim 1 , wherein the patterned grating comprises a plurality of substantially parallel grooves.

6. The directional backlight of claim 1 , wherein the characteristics of a directional pixel comprise a grating length, a grating width, a grating orientation, a grating pitch, and a grating duty cycle of the patterned grating.

7. The directional backlight of claim 6 , wherein the grating pitch and the grating orientation of the patterned grating control the direction of a directional lightbeam scattered by the directional pixel.

8. The directional backlight of claim 6 , wherein the grating length and the grating width of the patterned grating control the angular spread of a directional lightbeam scattered by a directional pixel.

9. The directional backlight of claim 1 , wherein a single modulator from the plurality of modulators modulates a directional lightbeam from a single directional pixel.

10. The directional backlight of claim 1 , wherein a single modulator from the plurality of modulators modulates directional lightbeams from a set of directional pixels.

11. The directional backlight of claim 1 , wherein the directional backplane comprises a polygonal slab of transparent material.

12. The directional backlight of claim 1 , wherein the directional backplane comprises a circular slab of transparent material.

13. The directional backlight of claim 1 , wherein the plurality of directional pixels comprises a plurality of polygonal directional pixels.

14. The directional backlight of claim 1 , wherein the plurality of directional pixels comprises a plurality of circular directional pixels.

15. The directional backlight of claim 1 , wherein the modulation layer comprises an LCD-based modulation layer and the plurality of modulators comprises a plurality of LCD cells.

16. A method for generating a 3D image with a directional backlight having a modulation layer, comprising:

specifying a plurality of characteristics for a plurality of directional pixels, each directional pixel comprising a patterned grating;

fabricating a directional backplane comprising a slab of transparent material with the plurality of directional pixels arranged thereon, the transparent material slab being configured to guide a lightbeam;

adding a modulation layer having a plurality of modulators above the directional backplane;

illuminating the directional backplane with a plurality of input planar lightbeams, the input planar lightbeams being guided within the transparent material slab and being scattered out of the transparent material slab by the plurality of directional pixels into a plurality of directional lightbeams; and

modulating the plurality of directional lightbeams with the plurality of modulators to generate multiple views of a 3D image.

17. The method of claim 16 , wherein each directional lightbeam is controlled by the characteristics of a directional pixel.

18. The method of claim 16 , wherein the characteristics of a directional pixel comprise a grating length, a grating width, a grating orientation, a grating pitch, and a grating duty cycle of the patterned grating.

19. The method of claim 16 , wherein a single modulator from the plurality of modulators modulates a directional lightbeam from a single directional pixel.

20. The method of claim 16 , wherein a single modulator from the plurality of modulators modulates directional lightbeams from a set of directional pixels.

21. The method of claim 16 , wherein the modulation layer comprises an LCD-based modulation layer and the plurality of modulators comprises a plurality of LCD cells.

22. A three-dimensional (3D) image-forming directional backlight, comprising:

a directional backplane comprising a material layer configured to guide light as a planar lightbeam within the material layer, the directional backplane having a plurality of directional pixels configured to scatter out a portion of a plurality of input planar lightbeams guided within the material layer into a plurality of directional lightbeams directed away from a surface of the directional backplane as a light field, each directional pixel comprising a patterned grating, each directional lightbeam having a direction and an angular spread controlled by characteristics of a directional pixel in the plurality of directional pixels; and

a modulation layer having a plurality of modulators configured to modulate the plurality of directional lightbeams, the modulation layer being adjacent to the surface of the directional backplane,

wherein a set of modulated directional lightbeams from a corresponding set of the directional pixels represents a view of a plurality of different views that form a 3D image.

23. The 3D image-forming directional backlight of claim 22 , wherein each modulator of the modulation layer is configured to modulate a single lightbeam from a single directional pixel.

24. The 3D image-forming directional backlight of claim 22 , wherein a grating pitch and a grating orientation of the patterned grating of a directional pixel control a direction of a directional lightbeam scattered by the directional pixel.