Waveguide illuminator having slab waveguide portion

Patent metadata

Field	Value
Publication number	US-11567255-B1
Application number	US-202117481227-A
Country	US
Kind code	B1
Filing date	Sep 21, 2021
Priority date	Jul 15, 2021
Publication date	Jan 31, 2023
Grant date	Jan 31, 2023

Abstract

A waveguide illuminator includes adjacent linear and slab waveguide areas. An input light beam is guided in a linear waveguide, is split into a plurality of sub-beams to propagate in individual linear waveguides to a slab waveguide area and form an output light beam in the slab waveguide area. An array of out-couplers is disposed in the slab waveguide area. The array of out-couplers out-couples portions of the output light beam forms an array of out-coupled beam portions for illuminating a display panel. Locations of the array of out-couplers are coordinated with locations of individual pixels of the display panel, thereby improving efficiency of light utilization by the display panel.

First claim

What is claimed is:

1. A waveguide illuminator comprising:
adjacent linear waveguide and slab waveguide areas;
a first input waveguide in the linear waveguide area, for guiding a first input light beam;
a first splitter coupled to the first input waveguide for splitting the first input light beam into a plurality of sub-beams;
a first plurality of linear waveguides in the linear waveguide area, coupled to the first splitter for receiving and guiding the plurality of sub-beams split from the first input light beam to a boundary between the linear waveguide and slab waveguide areas for forming a first output light beam propagating in the slab waveguide area; and
a first array of out-couplers spaced apart from one another in the slab waveguide area for out-coupling portions of the first output light beam to form a first array of out-coupled beam portions.

2. The waveguide illuminator of claim 1 , wherein each linear waveguide of the first plurality of linear waveguides includes a taper at the boundary between the linear waveguide and slab waveguide areas for expanding the sub-beams before coupling the sub-beams to the slab waveguide area.

3. The waveguide illuminator of claim 1 , wherein the first splitter comprises a 1×2 splitter and a slab interference cavity, wherein the 1×2 splitter is coupled to the first plurality of linear waveguides via the slab interference cavity, wherein ends of the linear waveguides of the first plurality of linear waveguides are disposed in areas of local interference maxima of the slab interference cavity.

4. The waveguide illuminator of claim 1 , wherein the first array of out-couplers comprises grating out-couplers for out-coupling the portions of the first output light beam to form the first array of out-coupled beam portions.

5. The waveguide illuminator of claim 4 , wherein the first input light beam comprises light of first, second, and third color channels, the waveguide illuminator further comprising a volume Bragg grating (VBG) in an optical path of the first array of out-coupled beam portions, wherein the VBG is configured to redirect light of at least two of the first, second, and third color channels in the first array of out-coupled beam portions, such that the light of the first, second, and third color channels downstream of the VBG propagates substantially at a same chief ray angle.

6. The waveguide illuminator of claim 4 , wherein at least one of:
the grating out-couplers are chirped to focus the out-coupled beam portions; or
the waveguide illuminator comprises an array of microlenses coupled to the grating out-couplers to focus the out-coupled beam portions;
the waveguide illuminator further comprising an array of color-selective redirectors downstream of the grating out-couplers configured such that light of first, second, and third color channels downstream of the array of color-selective redirectors propagates substantially at a same chief ray angle.

7. The waveguide illuminator of claim 6 , wherein the array of color-selective redirectors comprises an array of microprisms.

8. The waveguide illuminator of claim 6 , wherein the array of color-selective redirectors comprises an array of chirped gratings.

9. The waveguide illuminator of claim 1 , wherein the first input light beam carries light of a first color channel, the waveguide illuminator further comprising:
a second input waveguide in the linear waveguide area, for guiding a second input light beam of a second color channel;
a second splitter in the linear waveguide area, coupled to the second input waveguide for splitting the second input light beam into a plurality of sub-beams;
a second plurality of linear waveguides in the linear waveguide area, coupled to the second splitter for receiving and guiding the plurality of sub-beams split from the second input light beam to a boundary between the linear waveguide and slab waveguide areas for forming a second output light beam propagating in the slab waveguide area; and
a second array of out-couplers spaced apart from one another in the slab waveguide area for out-coupling portions of the second output light beam to form a second array of out-coupled beam portions.

10. The waveguide illuminator of claim 9 , wherein:
the slab waveguide area comprises first and second slab waveguide layers for guiding therein the first and second output light beams, respectively;
the first and second pluralities of linear waveguides are coupled to the first and second slab waveguide layers respectively; and
the first and second arrays of out-couplers are disposed in the first and second slab waveguide layers respectively and configured to out-couple the portions of the first and second output light beams respectively at a substantially same chief ray angle.

11. The waveguide illuminator of claim 9 , wherein:
the slab waveguide area supports first and second transversal modes of propagation;
the first and second pluralities of linear waveguides are configured to couple the respective pluralities of sub-beams into the first and second transversal modes respectively; and
the first and second arrays of out-couplers are configured to out-couple the portions of the first and second output light beams respectively at a substantially same chief ray angle.

12. The waveguide illuminator of claim 1 , wherein:
the slab waveguide area comprises a slab waveguide layer for propagating the first output light beam therein; and
the first array of out-couplers comprises an array of prisms evanescently coupled to the slab waveguide layer for out-coupling the portions of the first output light beam out of the waveguide illuminator to form the first array of out-coupled beam portions.

13. A display device comprising:
a waveguide illuminator comprising:
adjacent linear waveguide and slab waveguide areas;
an input waveguide in the linear waveguide area, for guiding an input light beam;
a splitter coupled to the input waveguide for splitting the input light beam into a plurality of sub-beams;
a plurality of linear waveguides in the linear waveguide area, coupled to the splitter for receiving and guiding the plurality of sub-beams split from the input light beam to a boundary between the linear waveguide and slab waveguide areas for forming an output light beam propagating in the slab waveguide area; and
an array of out-couplers spaced apart from one another in the slab waveguide area for out-coupling portions of the output light beam to form an array of out-coupled beam portions; and

a display panel comprising an array of display pixels disposed and configured to receive the array of the out-coupled beam portions.

14. The display device of claim 13 , wherein a pitch of the display pixels is substantially equal to a pitch of the array of out-couplers.

15. The display device of claim 13 , further comprising a light source for providing the input light beam to the input waveguide.

16. The display device of claim 15 , wherein the light source is a polarized light source, wherein the input and output light beams and the array of out-coupled beam portions are polarized;
wherein the array of display pixels comprises an array of tunable polarization rotators for tuning polarization of individual beam portions of the array of out-coupled beam portions.

17. The display device of claim 15 , wherein the light source comprises a monochromatic light source, wherein the input light beam has a wavelength of a first color channel.

18. A method for illuminating a display panel, the method comprising:
guiding a first input light bea

Assignees

• Facebook Tech Llc
• Meta Platforms Tech Llc

Inventors

• Koshelev Alexander
• Calafiore Giuseppe
• Gollier Jacques

Classifications

• G02B6/005

  provided by one optical element, or plurality thereof, placed on the light output side of the light guide · CPC title

• G02B6/0036 Primary

  2-D arrangement of prisms, protrusions, indentations or roughened surfaces · CPC title

• G02B6/124 Primary

  Geodesic lenses or integrated gratings · CPC title

• G02B6/0061

  to provide homogeneous light output intensity · CPC title

• G02B6/0055

  Reflecting element, sheet or layer · CPC title