CN117642576A

CN117642576A - Waveguide illuminator with slab waveguide portion

Info

Publication number: CN117642576A
Application number: CN202280049752.XA
Authority: CN
Inventors: 亚历山大·科舍列夫; 雅克·戈利耶; 彭枫琳; 耿莹; 朱塞佩·卡拉菲奥雷
Original assignee: Meta Platforms Technologies LLC
Current assignee: Meta Platforms Technologies LLC
Priority date: 2021-07-15
Filing date: 2022-07-15
Publication date: 2024-03-01

Abstract

A waveguide illuminator includes adjacent linear waveguide regions and planar waveguide regions. The input light beam is guided in the linear waveguides, split into a plurality of sub-beams to propagate in the respective linear waveguides to the slab waveguide region and form an output light beam in the slab waveguide region. An array of outcouplers is disposed in the slab waveguide region. The array of couplers couples out portions of the output beam to form an array of coupled-out beam portions for illuminating the display panel. The position of the array of the outcouplers is matched with the position of each pixel of the display panel, thereby improving the light utilization efficiency of the display panel.

Description

Waveguide illuminator with slab waveguide portion

Technical Field

The present disclosure relates to luminaires, visual display devices, and related components and modules.

Background

The visual display provides information including still images, video, data, etc. to one or more viewers. Visual displays find application in a variety of fields including entertainment, education, engineering, science, professional training, advertising, to name a few. Some visual displays (e.g., televisions) Display images to multiple users, while some visual Display systems (e.g., near-Eye displays (NED)) are intended for use by a single user.

An artificial reality system typically includes a NED (e.g., a headset) or a pair of glasses configured to present content to a user. The near-eye display may display the Virtual object or combine an image of the real object with the Virtual object as in a Virtual Reality (VR) application, an augmented Reality (Augmented Reality, AR) application, or a Mixed Reality (MR) application. For example, in an AR system, a user may view an Image (e.g., a Computer-Generated Image (CGI)) of a virtual object superimposed with the surrounding environment through a perspective "combiner" component. The combiner of the wearable display is typically transparent to external light, but includes some light routing optics to direct the display light into the field of view of the user.

Because Head-mounted displays (HMDs) or NED displays are typically worn on the Head of a user, large, heavy, unbalanced and/or heavy display devices with heavy batteries would be cumbersome and uncomfortable for the user to wear. Thus, a head mounted display device may benefit from a compact and efficient construction that includes efficient light sources and illuminators that provide illumination of the display panel, as well as high throughput visual lenses and other optical elements in the image forming chain.

Disclosure of Invention

According to a first aspect of the present disclosure, there is provided a waveguide illuminator comprising: adjacent linear waveguide regions and slab waveguide regions; a first input waveguide in the linear waveguide region for guiding a first input light beam; a first beam splitter coupled to the first input waveguide for splitting the first input beam into a plurality of sub-beams; a plurality of first linear waveguides located in the linear waveguide region, coupled to the first beam splitter, for receiving the plurality of sub-beams split from the first input light beam and guiding the plurality of sub-beams to a boundary between the linear waveguide region and the slab waveguide region to form a first output light beam propagating in the slab waveguide region; a first array of couplers spaced apart from each other in the slab waveguide region, the first array of couplers for coupling out portions of the first output beam to form a first array of coupled-out beam portions.

In some embodiments, each of the plurality of first linear waveguides may include a tapered portion located at a boundary between the linear waveguide region and the slab waveguide region for expanding the plurality of beamlets before coupling the plurality of beamlets to the slab waveguide region.

In some embodiments, the first beam splitter may include a 1 x 2 beam splitter and a slab interference cavity, wherein the 1 x 2 beam splitter is coupled to the plurality of first linear waveguides via the slab interference cavity, wherein ends of the linear waveguides of the plurality of first linear waveguides are disposed in a region of the slab interference cavity where local interference is greatest.

In some embodiments, the first array of couplers may comprise a plurality of grating couplers for coupling out portions of the first output beam to form a first array of coupled-out beam portions.

In some embodiments, the first input light beam may include light of a first color channel, light of a second color channel, and light of a third color channel, the waveguide illuminator further including a volume bragg grating (Volume Bragg Grating, VBG) located in an optical path of the first array of coupled-out beam portions, wherein the VBG is configured to redirect light of at least two of the first color channel, the second color channel, and the third color channel in the first coupled-out beam portion such that light of the first color channel, light of the second color channel, and light of the third color channel downstream of the VBG propagate at substantially the same chief ray angle.

In some embodiments, the plurality of grating couplers may be chirped to focus the coupled beam portions; the waveguide illuminator may comprise a microlens array coupled to the plurality of grating couplers to focus the coupled beam portions; the waveguide illuminator may further comprise a color selective redirector array downstream of the grating coupler, configured such that light of the first color channel, light of the second color channel, and light of the third color channel downstream of the array of color selective redirectors propagate at substantially the same chief ray angle.

In some embodiments, the color selection redirector array may comprise an array of microprisms.

In some embodiments, the color selection redirector array may comprise a chirped grating array.

In some embodiments, the first input beam may carry light of a first color channel, the waveguide illuminator further comprising: a second input waveguide in the linear waveguide region for guiding a second input light beam of a second color channel; a second beam splitter located in the linear waveguide region, coupled to the second input waveguide, for splitting the second input beam into a plurality of sub-beams; a plurality of second linear waveguides located in the linear waveguide region, coupled to the second beam splitter, for receiving the plurality of sub-beams split from the second input light beam and guiding the plurality of sub-beams to a boundary between the linear waveguide region and the slab waveguide region to form a second output light beam propagating in the slab waveguide region; and a second array of couplers spaced apart from each other in the slab waveguide region, the second array of couplers for coupling out portions of the second output beam to form a second array of coupled-out beam portions.

In some embodiments, the slab waveguide region includes first and second slab waveguide layers for guiding first and second output beams in the first and second slab waveguide layers, respectively; a plurality of first linear waveguides and a plurality of second linear waveguides are coupled to the first planar waveguide layer and the second planar waveguide layer, respectively; and the first array of outcouplers and the second array of outcouplers are disposed in the first and second planar waveguide layers, respectively, and are configured to couple out portions of the first output beam and portions of the second output beam, respectively, at substantially the same chief ray angle.

In some embodiments, the slab waveguide region supports a first lateral propagation mode and a second lateral propagation mode; the plurality of first linear waveguides and the plurality of second linear waveguides are configured to couple a respective plurality of beamlets into a first transverse mode and a second transverse mode, respectively; and the first array of couplers and the second array of couplers are configured to couple out portions of the first output beam and portions of the second output beam, respectively, at substantially the same chief ray angle.

In some embodiments, the slab waveguide region includes a slab waveguide layer for propagating the first output beam in the slab waveguide layer; and the first array of couplers includes an array of prisms evanescently coupled to the slab waveguide layer, the array of prisms for coupling out portions of the first output beam from the waveguide illuminator to form a first array of coupled-out beam portions.

According to another aspect of the present disclosure, there is provided a display device including a waveguide illuminator and a display panel, the waveguide illuminator including: adjacent linear waveguide regions and slab waveguide regions; an input waveguide in the linear waveguide region for guiding an input light beam; a first beam splitter coupled to the input waveguide for splitting the input beam into a plurality of sub-beams; a plurality of linear waveguides located in the linear waveguide region, coupled to the beam splitter, for receiving a plurality of sub-beams split from the input light beam and guiding the plurality of sub-beams to a boundary between the linear waveguide region and the slab waveguide region to form an output light beam propagating in the slab waveguide region; and an array of couplers spaced apart from each other in the slab waveguide region for coupling out portions of the output beam to form an array of coupled-out beam portions; the display panel includes an array of display pixels arranged and configured to receive the array of coupled beam portions.

In some embodiments, the pitch of the display pixels may be substantially equal to the pitch of the array of outcouplers.

In some embodiments, the display device may further include a light source for providing an input light beam to the input waveguide.

In some embodiments, the light source may be a polarized light source, wherein the array of the input and output light beams and the coupled-out beam portions are polarized; wherein the array of display pixels may comprise an array of adjustable polarization rotators for adjusting the polarization of individual beam portions of the array of coupled-out beam portions.

In some embodiments, the light source may comprise a monochromatic light source, wherein the input light beam has a wavelength of the first color channel.

According to another aspect of the present disclosure, there is provided a method for illuminating a display panel, the method including: directing a first input light beam in a first input linear waveguide of a waveguide illuminator; splitting a first input beam into a plurality of sub-beams; directing a plurality of sub-beams of a first input light beam in a plurality of first linear waveguides of a waveguide illuminator to a slab waveguide region of the waveguide illuminator; propagating a plurality of sub-beams of a first input light beam in a slab waveguide region to form a first output light beam propagating in the slab waveguide region; and coupling out portions of the first output beam to form a first array of coupled-out beam portions.

In some embodiments, the method may further include expanding the plurality of beamlets in waveguide tapers of the first plurality of linear waveguides prior to coupling the plurality of beamlets to the slab waveguide region.

In some embodiments, the method may further comprise: directing a second input light beam in a second input linear waveguide of the waveguide illuminator; splitting the second input beam into a plurality of sub-beams; directing a plurality of sub-beams of a second input light beam in a plurality of second linear waveguides of the waveguide illuminator into a slab waveguide region of the waveguide illuminator; propagating a plurality of sub-beams of the second input light beam in the slab waveguide region to form a second output light beam propagating in the slab waveguide region; and coupling out portions of the second output beam to form a second array of coupled-out beam portions.

It should be understood that any feature described herein as being suitable for incorporation into one or more aspects, or embodiments, of the present disclosure is intended to be generic in any and all aspects and embodiments of the present disclosure. Other aspects of the disclosure will be appreciated by those skilled in the art from the description, claims and drawings of the disclosure. The foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the claims.

Drawings

Exemplary embodiments will now be described in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic plan view of a waveguide illuminator of the present disclosure;

FIG. 2 is a plan view of a slab waveguide region of the waveguide illuminator of FIG. 1, showing light scattering caused by defects in the slab waveguide region;

FIG. 3 is a schematic plan view of an array of adiabatic tapers of the waveguide illuminator of claim 1;

FIG. 4 is a plan view of a beam splitter embodiment of the waveguide illuminator of FIG. 1;

FIG. 5 is a side cross-sectional view of a grating coupler in the slab region of the waveguide illuminator of FIG. 1;

FIG. 6 is a side cross-sectional view of an embodiment of a waveguide illuminator comprising a volume Bragg grating (Volume Bragg Grating, VBG) for compensating for dispersion of light exiting the grating coupler of FIG. 5;

FIG. 7 is a side cross-sectional view of an embodiment of a waveguide illuminator comprising a lens-prism combination for compensating for dispersion of light exiting the grating coupler of FIG. 5;

FIG. 8 is a side cross-sectional view of an evanescent prism (evanescent prismatic) coupler usable in the waveguide illuminator of claim 1;

FIG. 9 is a side cross-sectional view of an embodiment of the waveguide illuminator with multilayer slab waveguide region of claim 1;

FIG. 10 is a side cross-sectional view of the waveguide illuminator of FIG. 1 with a few-mode (few-mode) slab waveguide region;

FIG. 11 is a schematic diagram of a near-eye display using the waveguide illuminator of FIG. 1;

FIG. 12 is a flowchart of a method for illuminating a display panel according to the present disclosure;

FIG. 13 is a view of an Augmented Reality (AR) display of the present disclosure having a form factor of a pair of glasses; and

fig. 14 is a three-dimensional view of a Head Mounted Display (HMD) of the present disclosure.

Detailed Description

While the present teachings are described in connection with various embodiments and examples, the present teachings are not intended to be limited to these embodiments. On the contrary, the present teachings encompass various alternatives and equivalents, as will be appreciated by those of skill in the art. All statements herein reciting principles, aspects, and embodiments of the disclosure, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Furthermore, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure.

As used herein, the terms "first" and "second," etc. are not intended to imply a sequential order, but rather are intended to distinguish one element from another element unless otherwise explicitly stated. Similarly, the sequential order of the method steps does not imply a sequential order of their execution unless explicitly stated.

In a visual display comprising an array of pixels coupled to an illuminator, the light utilization efficiency depends on the ratio of the geometric area occupied by each pixel to the total area of the display panel. For micro-displays commonly used in near-eye displays and/or head-mounted displays, this ratio may be less than 50%. The color filters on the display panel, which on average transmit no more than 30% of the incident light, further prevent efficient backlight utilization. In addition, for polarization-based display panels (e.g., liquid Crystal (LC) display panels), there may be a 50% loss of polarization. All of these factors greatly reduce the light utilization and overall electro-optic conversion efficiency (wall plug efficiency) of the display, which is undesirable.

In accordance with the present disclosure, light utilization and electro-optic conversion efficiency of a backlit display may be improved by providing a waveguide illuminator comprising an array of couplers aligned with pixels of a display panel. In displays where the illuminator emits primary light, e.g., red, green, and blue, the color of the illumination light may be matched to the color filter or the color filter may be omitted entirely. For polarization-based displays, the polarization of the emitted light may be matched to a predefined input polarization state. By matching the spatial distribution, transmission wavelength and transmission polarization characteristics of the pixels of the display panel, the useful portion of the display light that is not absorbed or reflected by the display panel on its way to the viewer's eye can be significantly improved, thus significantly improving the electro-optic conversion efficiency of the display.

The combination of single-mode or few-mode waveguides with laser illumination allows for efficient control of light characteristics such as color and directivity. When light propagates in a single spatial mode, the output may be diffraction limited and highly directional. The single mode propagation also allows light to be coupled out at specific points on the waveguide and allows incorporation of focusing pixels that can focus light into pixels of the display panel while avoiding scattering in the inter-pixel region. Narrow spectrum laser illumination enables large color gamut display. In addition, the single mode waveguide can maintain polarization, thereby obtaining highly polarized output from the backlight unit without requiring a polarizer.

According to the present disclosure, a waveguide illuminator is provided that includes adjacent linear waveguide regions and planar waveguide regions. The first input waveguide is disposed in the linear waveguide region for guiding a first input light beam. The first beam splitter is coupled to the first input waveguide for splitting the first input beam into a plurality of sub-beams. A plurality of first linear waveguides located in the linear waveguide region are coupled to the first beam splitter for receiving a plurality of sub-beams split from the first input light beam and directing the plurality of sub-beams to a boundary between the linear waveguide region and the slab waveguide region to form a first output light beam propagating in the slab waveguide region. The first array of outcouplers is disposed in the slab waveguide region. The couplers are spaced apart from each other and configured to couple out portions of the first output beam to form a first array of coupled-out beam portions.

In some embodiments, each linear waveguide of the first plurality of linear waveguides includes a taper located at a boundary between the linear waveguide region and the slab waveguide region for expanding the plurality of beamlets before coupling the plurality of beamlets to the slab waveguide region. The first beam splitter may include a 1 x 2 beam splitter and a slab interference cavity. The 1 x 2 beam splitter is coupled to the plurality of first linear waveguides via a slab interference cavity. The ends of the linear waveguides of the first plurality of linear waveguides are disposed in a region of the slab interference cavity where local interference is greatest.

In embodiments where the first input beam comprises light of the first color channel, light of the second color channel, and light of the third color channel, the waveguide illuminator may further comprise a Volume Bragg Grating (VBG) located in the optical path of the first array of coupled-out beam portions. The VBG may be configured to redirect light of at least two of the first color channel, the second color channel and the third color channel in the first coupled-out beam portion such that light of the first color channel, light of the second color channel and light of the third color channel downstream of the VBG propagate at substantially the same chief ray angle.

The first array of couplers may comprise a plurality of grating couplers for coupling out a plurality of portions of the first output beam to form a first array of coupled-out beam portions. The grating coupler may be chirped to focus the coupled beam portions; alternatively or additionally, the waveguide illuminator may comprise a microlens array coupled to the plurality of grating couplers to focus the coupled beam portions. The waveguide illuminator may further comprise a color-selective redirector array downstream of the plurality of grating couplers, configured such that light of the first color channel, light of the second color channel, and light of the third color channel downstream of the color-selective redirector array propagate at substantially the same chief ray angle. The color selective redirector array may include, for example, a microprism array and/or a chirped grating array.

In an embodiment of the multi-color illuminator, the first input beam may carry light of a first color channel and the second input beam may carry light of a second color channel. The waveguide illuminator may further comprise a second input waveguide in the linear waveguide region for guiding a second input light beam. The second beam splitter may be disposed in the linear waveguide region. The second beam splitter may be coupled to the second input waveguide for splitting the second input beam into a plurality of sub-beams. A plurality of second linear waveguides may be disposed in the linear waveguide region. The plurality of second linear waveguides may be coupled to a second beam splitter for receiving a plurality of sub-beams split from the second input light beam and directing the plurality of sub-beams to a boundary between the linear waveguide region and the slab waveguide region to form a second output light beam propagating in the slab waveguide region. A second array of couplers spaced apart from each other in the slab waveguide region may be provided to couple out portions of the second output beam to form a second array of coupled out beam portions.

In some embodiments, the slab waveguide region includes first and second slab waveguide layers for guiding first and second output beams in the first and second slab waveguide layers, respectively. The plurality of first linear waveguides and the plurality of second linear waveguides are coupled to the first planar waveguide layer and the second planar waveguide layer, respectively. The first array of outcouplers and the second array of outcouplers are disposed in the first and second planar waveguide layers, respectively, and are configured to couple out portions of the first output beam and portions of the second output beam, respectively, at substantially the same chief ray angle.

In some embodiments, the slab waveguide region supports a first lateral propagation mode and a second lateral propagation mode. The plurality of first linear waveguides and the plurality of second linear waveguides are configured to couple a respective plurality of beamlets into a first transverse mode and a second transverse mode, respectively. The first array of outcouplers and the second array of outcouplers are configured to couple out portions of the first output beam and portions of the second output beam, respectively, at substantially the same chief ray angle.

In some embodiments, the slab waveguide region includes a slab waveguide layer for propagating the first output beam in the slab waveguide layer. The first array of outcouplers comprises an array of prisms evanescently coupled to the planar waveguide layer, the array of prisms being adapted to couple out a portion of the first output beam from the waveguide illuminator, thereby forming a first array of coupled-out beam portions.

According to the present disclosure, there is provided a display device comprising a waveguide illuminator as described herein and a display panel comprising an array of display pixels arranged and configured to receive an array of coupled beam portions. The pitch of the display pixels may be substantially equal to the pitch of the array of outcouplers.

The display device may further comprise a light source for providing an input light beam to the input waveguide. The light source may be a polarized light source such that the input and output light beams and the array of coupled-out beam portions are polarized; the display pixel array may comprise an array of adjustable polarization rotators for adjusting the polarization of individual beam portions of the array of coupled-out beam portions. The light source may be a monochromatic light source and the input light beam may have a wavelength of the first color channel.

According to the present disclosure, there is also provided a method for illuminating a display panel. The method comprises the following steps: directing a first input light beam in a first input linear waveguide of a waveguide illuminator; splitting a first input beam into a plurality of sub-beams; directing a plurality of sub-beams of a first input light beam in a plurality of first linear waveguides of a waveguide illuminator to a slab waveguide region of the waveguide illuminator; propagating a plurality of sub-beams of a first input light beam in a slab waveguide region to form a first output light beam propagating in the slab waveguide region; and coupling out portions of the first output beam to form a first array of coupled-out beam portions.

The method may further include expanding the plurality of beamlets in a waveguide taper of the first plurality of linear waveguides prior to coupling the plurality of beamlets to the slab waveguide region. The method may further comprise: directing a second input light beam in a second input linear waveguide of the waveguide illuminator; splitting the second input beam into a plurality of sub-beams; directing a plurality of sub-beams of a second input light beam in a plurality of second linear waveguides of the waveguide illuminator into a slab waveguide region of the waveguide illuminator; propagating a plurality of sub-beams of the second input light beam in the slab waveguide region to form a second output light beam propagating in the slab waveguide region; and coupling out portions of the second output beam to form a second array of coupled-out beam portions.

Referring now to fig. 1, waveguide illuminator 100 includes a linear waveguide region 101 and a slab waveguide region 102 disposed adjacent to each other and sharing a common boundary 104. The linear waveguide region 101 includes a plurality of linear waveguide structures, and the slab waveguide region includes a plurality of slab waveguide structures. In this context, the term "linear waveguide" or "linear waveguide structure" refers to a waveguide that limits light propagation in two dimensions, just like a light guide beam (light wire). The linear waveguide may be straight, curved, etc. In other words, the term "linear" does not refer to a straight waveguide section. One example of a linear waveguide is a ridge waveguide. The term "slab waveguide" or "slab waveguide structure" refers to a waveguide that limits light propagation in one dimension, typically the vertical dimension, i.e., in the thickness of the waveguide chip. Light can freely propagate in the plane of the waveguide chip. In both cases, the waveguide may be a single mode waveguide or a few mode waveguide, e.g., less than 12 transverse propagation modes.

The input waveguide 106 is disposed in the linear waveguide region 101 of the waveguide illuminator 100. The input waveguide 106 guides a light beam 108 shown with arrows. The light beam 108 may be emitted, for example, by a light source 110. A beam splitter 112 is coupled to the input waveguide 106 for splitting the input beam 108 into a plurality of sub-beams 114 shown by arrows. A plurality of linear waveguides 116 are disposed in the linear waveguide region 101. These linear waveguides 116 are coupled to the beam splitter 112 for guiding the plurality of sub-beams 114 split from the input light beam 108 to the boundary 104 between the linear waveguide region 101 and the slab waveguide region 102 to form an output light beam 118 propagating in the slab waveguide region 102. The output beam 118 is shown with a large arrow with a dotted dashed border. The direction of propagation of the output beam 118 depends on the phase relationship between the beamlets 114. For sub-beams 114 that are in phase, in the normal case, the output beam 118 propagates perpendicular to the boundary 104, i.e., horizontally from left to right in fig. 1. The output beam 118 may be slightly expanded in the plane of the slab region 102 due to diffraction.

An array of a plurality of couplers 120 is disposed in the slab waveguide region 102. These couplers 120 (e.g., grating couplers or evanescent couplers) are spaced apart from one another in the slab waveguide region 102. In operation, the coupler 120 couples out portions 122 of the first output beam to form a first array of coupled-out beam portions 122. The arrangement of the outcoupling 120 may be associated with the arrangement of the pixels of the illuminated display panel to ensure that the portion 122 propagates mainly through the pixels of the display panel without being blocked or scattered in the inter-pixel area of the display panel, which increases the amount of light transmitted through the display panel, i.e. increases the light utilization.

An advantage of a slab waveguide illuminator is that it has an increased tolerance to manufacturing imperfections that may cause scattering and related interference effects compared to an illuminator having a linear waveguide array (grating coupler along the linear waveguide). Illustratively, referring to FIG. 2, the output beam 118 propagates in the slab waveguide region 102 encountering a particle defect 200. As indicated by arrow 202, a portion of the output beam 118 may scatter and if not diffraction effects fill in shadows left by the particle defects 200 in the propagation direction in the plane of the slab waveguide region 102, speckle may be generated in the output beam pattern. Thus, light propagating in slab waveguide region 102 is less susceptible to scattering by manufacturing imperfections than light carried by a linear illumination waveguide array equipped with grating couplers along its length.

Referring to fig. 3 and with further reference to fig. 1, each linear waveguide 116 of waveguide illuminator 100 may include a taper 300, e.g., an adiabatic taper, located at boundary 104 between linear waveguide region 101 and slab waveguide region 102. The purpose of the taper 300 is to expand the respective beamlets 114 prior to coupling the beamlets 114 to the slab waveguide region 102. The beamlets 114 expanded by the taper 300 fill the slab waveguide region 102 more uniformly, resulting in better directivity and uniformity of the output beam 118 propagating in the slab region 102 shown in fig. 1.

The function of the beam splitter 112 of fig. 1 is to split the input beam 108 into a plurality of sub-beams 114. Many configurations of the beam splitter 112 are possible, such as a binary tree of 1 x 2 beam splitters or evanescent 2 x 2 couplers, a multimode interference (Multimode Interference, MMI) beam splitter, etc. Referring to the non-limiting example of FIG. 4, beam splitter component 400 includes a 1×2 waveguide beam splitter 402 coupled to a plurality of linear waveguides 116 via a slab interference cavity 404 that is part of a slab waveguide having an outer perimeter 405. In operation, the 1 x 2 beam splitter 402 splits the input beam 108 into two portions 411, 412 of substantially equal optical power. The portions 411, 412 propagate in linear waveguides 421, 422 to the slab interference cavity 404. The portions 411, 412 expand in the slab interference cavity 404, undergoing optical interference at the opposite side 408 of the slab interference cavity 404. The end 117 of the linear waveguide 116 is disposed in the region of maximum local interference of the side 408 of the slab interference cavity 404. The region of minimal local interference is disposed between the ends 117 of the plurality of linear waveguides 116 such that optical power of the input optical beam 108 is not lost between the ends 117 of the plurality of linear waveguides 116.

Referring back to fig. 1, slab waveguide region 102 is provided with a plurality of spaced apart couplers 120 for coupling out portions 122 of output beam 118. The coupler 120 may be based on a diffraction grating that diffracts portions 122 of the output beam 118 from the slab region 102. The diffraction angle of the portion 122 is wavelength dependent and therefore will typically be different for different color channels of light. This can be problematic in applications where waveguide illuminator 100 is used as a light source for back-side or front-side illumination of a color display. By way of illustration, referring to fig. 5, waveguide illuminator 500 is an embodiment of waveguide illuminator 100 of fig. 1. Waveguide illuminator 500 includes a plurality of grating couplers 520 spaced apart from one another and coupled to slab core 530 of slab waveguide region 502 for coupling out a plurality of portions 522 of output beam 518. In waveguide illuminator 500, output beam 518 includes three color channels of light: red light beam 522R, green light beam 522G, and blue light beam 522B. The red, green and blue light beams 518R, 518G, 518B are coupled out at different chief ray (central ray) angles. The chief ray of red beam 522R is shown by the dotted dashed arrow, the chief ray of green beam 522G is shown by the solid arrow, and the chief ray of blue beam 522B is shown by the dashed arrow. As can be seen in fig. 5, the coupled-out light portions 522 are angularly dispersed by wavelength. However, in applications where it is desired that the portion of light that is coupled out is not wavelength dispersive, all colors of light need to be coupled out at the same chief ray angle so that sub-beams of different colors of light co-propagate in the same direction.

Referring to fig. 6, waveguide illuminator 600 is an embodiment of waveguide illuminator 500 of fig. 5, waveguide illuminator 600 comprising similar elements and operating with a multi-wavelength light source that emits light of a first color channel, light of a second color channel, and light of a third color channel (e.g., red light beam 522R, green light beam 522G, and blue light beam 522B). To compensate for wavelength dispersion, waveguide illuminator 600 includes a Volume Bragg Grating (VBG) 632 in the optical path of an array of coupled-out beam portions 522 including red light beam 522R, green light beam 522G, and blue light beam 522B. The VBG may be configured to redirect light in a wavelength selective manner. Accordingly, the VBG 632 may be configured to redirect light of at least two of the first, second, and third color channels in the coupled-out beam portion 522 such that light of the first, second, and third color channels downstream of the VBG propagate at substantially the same chief ray angle. For example, VBG 632 may be configured to not redirect green light 522G when redirecting red light 522R and blue light 522B such that output red light beam 622R, output green light beam 622G, and output blue light beam 622B of output light 622 have substantially parallel chief rays, as shown in fig. 6.

In some embodiments of the waveguide illuminator, the coupled-out beam portion is refocused to provide a desired beam divergence characteristic. For example, referring to fig. 7, waveguide illuminator 700 is an embodiment of waveguide illuminator 500 of fig. 5, waveguide illuminator 700 comprising similar elements and operating with a multi-wavelength light source (not shown) that emits light of a first color channel, light of a second color channel, and light of a third color channel (specifically, red light beam 522R, green light beam 522G, and blue light beam 522B). Waveguide illuminator 700 further includes an array of microlenses 731 coupled to grating coupler 520. In fig. 7, two such micro-lenses 731 and two such grating couplers 520 are shown, wherein individual grating lines are represented by black squares. Microlens 731 can be configured to focus the coupled-out beam portions 522R, 522G, and 522B. An array of microprisms 732 is disposed downstream of grating coupler 520, the array of microprisms being configured such that red light beam 722R, green light beam 722G, and blue light beam 722B downstream of the array of microprisms 732 propagate at substantially the same chief ray angle. In fig. 7, the light of the red light 722R is shown by dotted dashed arrows, the light of the green light 722G is shown by solid arrows, and the light of the blue light 722B is shown by dashed arrows. For each color channel of light, three such rays are shown, including a principal ray 707 and two edge rays 709. Microprisms 732 (two shown in fig. 7) act as directors that perform the function of parallelizing the chief rays 707 of all color channels, similar to VBG 632 of fig. 6. Other types of color or wavelength selective redirectors may be used, such as a grating-based color selective redirector. A chirped grating array that combines the focusing function of microlenses 731 and the beam redirecting function of microprisms 732 may also be used. Furthermore, the grating coupler may be chirped to focus the coupled-out beam portions.

Turning to fig. 8, waveguide illuminator 800 is an embodiment of waveguide illuminator 100 of fig. 1, waveguide illuminator 800 comprising similar elements and operating with a multi-wavelength light source (not shown) that emits light of a first color channel, light of a second color channel, and light of a third color channel (specifically, red light beam 822R component, green light beam 822G component, and blue light beam 822B component combined into output beam 818). The waveguide illuminator 800 of fig. 8 includes an array of prisms 832 evanescently coupled to the slab waveguide layer 830 of the slab waveguide portion 802. Prism 832 performs the function of coupler 120 of waveguide illuminator 100 in fig. 1. The prism 832 of the waveguide illuminator 800 of fig. 8 evanescently couples out a portion of the red light beam 822R component, a portion of the green light beam 822G component, and a portion of the blue light beam 822B component of the output light beam 818 by first coupling out into the prism 832 at an acute angle, and then reflecting downward (e.g., by total internal reflection or TIR) from the top surface of the prism 832 in fig. 8 to form an array of coupled-out beam portions of different color channels. Since the direction of evanescent outcoupling is much less sensitive to the wavelength of the outcoupled light than in the case of a grating outcoupler, a portion of the red light beam 822R component, a portion of the green light beam 822G component and a portion of the blue light beam 822B component leave the waveguide illuminator 800 substantially parallel to each other.

In some embodiments, the waveguide illuminator may comprise the plurality of structures of fig. 1, one for each color channel. Light of different color channels carried by different input beams may be coupled into separate input linear waveguides. For example, for a second color channel, a second input waveguide may be provided in the linear waveguide region 101 for guiding a second input beam of light carrying the second color channel. The second beam splitter may be disposed in the linear waveguide region 101. The second beam splitter may be coupled to the second input waveguide for splitting the second input beam into a plurality of sub-beams; a plurality of second linear waveguides may be disposed in the linear waveguide region 101. The second linear waveguides may be coupled to a second beam splitter for receiving a plurality of sub-beams split from the second input light beam and directing the sub-beams to a boundary between the linear waveguide region and the slab waveguide region to form a second output light beam propagating in the slab waveguide region. In a similar manner, the second array of couplers may be spaced apart from one another in the slab waveguide region 102 to couple out portions of the second output beam to form a second array of coupled-out beam portions.

A non-limiting illustrative example of such a multi-channel waveguide illuminator 900 is presented in fig. 9. The slab waveguide region 902 of the multi-channel waveguide illuminator 900 includes one slab waveguide layer for each color channel, in this example, three single-mode slab waveguide layers 930R, 930G, and 930B for propagating the red 918R, green 918G, and blue 918B output beams, respectively. The single mode slab waveguide layers 930R, 930G, and 930B are coupled with an array of corresponding linear waveguides (not shown for simplicity). At least two planar waveguide layers for two color channels may be provided in a bi-color system.

Still referring to fig. 9, an array of red couplers (e.g., grating-based couplers) 920R, an array of green couplers (e.g., grating-based couplers) 920G, and an array of blue couplers (e.g., grating-based couplers) 920B are disposed in the first and second slab regions, respectively, and are configured to couple out a portion 922R of the red output beam 918R, a portion 922G of the green output beam 918G, and a portion 922B of the blue output beam 918B, respectively. Since light of different color channels propagates in different slab waveguide layers 930R, 930G, and 930B and is coupled out by different couplers 920R, 920G, and 920B, these different couplers may be configured to couple out beam portions 922R, 922G, and 922B at substantially the same chief ray 907 angle, and optionally at the same cone angle between two edge rays 909.

Turning to fig. 10, slab waveguide region 1002 of waveguide illuminator 1000 includes a few-mode slab waveguide layer 1030 that can guide several lateral propagation modes, in this example, zero (0) ^th ) Transverse mode, first (1 ^st ) Transverse mode and second (2 ^nd ) Transverse mode. A plurality of linear waveguides (not shown for simplicity) are configured to couple respective pluralities of sub-beams of different color channels into different lateral propagation modes of the few-mode slab waveguide layer 1030 to propagate as red, green, and blue output beams 1018R, 1018G, 1018B. In particular, red output beam 1018R may be in a zeroth lateral propagation modePropagating green output beam 1018G may propagate in a first lateral propagation mode and blue output beam 1018B may propagate in a second lateral propagation mode. The corresponding couplers 1020R, 1020G, and 1020B are configured to couple the portion 1022R of the red output beam 1018R from the zeroth lateral propagation mode, the portion 1022G of the green output beam 1018G from the first lateral propagation mode, and the portion 1022B of the blue output beam 1018B from the second lateral propagation mode, respectively. To this end, as shown in fig. 10, the couplers 1020R, 1020G, and 1020B may be disposed at different depth levels in the few-mode core layer 1030. Since the light of the different color channels propagates in different lateral propagation modes and is coupled out by different outcouplers 1020R, 1020G, and 1020B, these different outcouplers may be configured to couple out beam portions 1022R, 1022G, and 1022B at substantially the same chief ray 1007 angle, and optionally at the same cone angle between edge rays 1009.

Referring now to fig. 11, a display device 1100 includes a waveguide illuminator 100 coupled to a display panel 1102. A light source 1101 (e.g., a monochromatic light source at the wavelength of the color channel) may be optically coupled to the illuminator 100 for providing a light beam 108 to the illuminator 100. The display panel 1102 includes an array of display pixels 1120 that are arranged and configured to receive an array of coupled beam portions 122 from the illuminator 100. To ensure efficient use of beam portion 122, the position and spacing of display pixels 1120 may be matched to the position and spacing of the array of outcouplers 120 in both the X-direction and the Y-direction.

The display panel 1102 may include a Liquid Crystal (LC) layer 1104 in which display pixels 1120 are configured to controllably switch or adjust the polarization states of the respective beam portions 122, such as to rotate the linear polarization states. In this embodiment, the light source 1101 may be a polarized light source that emits linearly polarized light. A linear polarizer 1128 may be provided to convert the polarization distribution of beam portion 122 imparted by display pixel 1120 to an optical power density distribution representing the image to be displayed. The image is in the linear domain, where the pixel coordinates of the displayed image correspond to the XY coordinates of display pixel 1120.

A visual lens (ocular lenses) 1130 may be used to convert the image in the linear domain to an image in the angular domain at the eyebox 1126 for direct viewing by the eye 1180. Here, the term "image in the angular domain" refers to an image in which the pixel coordinates of the displayed image correspond to the ray angle of the beam portion 122. In embodiments with an adjustable polarization rotator, light source 1101 may emit polarized light and waveguide illuminator 100 may maintain this polarization state. It is also noted that any of the waveguide illuminators disclosed herein may be used in place of waveguide illuminator 100 of display device 1100. Waveguide illuminator 100 can be fabricated to be transparent to external light 1114.

Referring to fig. 12 and with further reference to fig. 1, a method 1200 for illuminating a display panel includes directing (1202) a first input light beam, such as light beam 108 (fig. 1), in a first input linear waveguide (e.g., input linear waveguide 106) of a waveguide illuminator (e.g., waveguide illuminator 100 of fig. 1). The first input beam is split (fig. 12; 1204) into a plurality of beamlets 114. The plurality of beamlets 114 in the plurality of linear waveguides 116 of the waveguide illuminator 100 are directed 1206 to the slab waveguide region 102 of the waveguide illuminator 100. The plurality of beamlets 114 are propagated 1208 in the slab waveguide region 102 to form a first output beam, such as output beam 118, propagating in the slab waveguide region 102. Portions of the first output beam are coupled out (1210) to form a first array of coupled-out beam portions (i.e., beam portions 122 in fig. 1). The plurality of beamlets 114 may be expanded (1207) in a taper (e.g., taper 300 in fig. 3) of the plurality of linear waveguides 116 prior to coupling the plurality of beamlets to the slab waveguide region 102.

In embodiments where the illumination light includes multiple color channels, the method 1200 may be performed for each color channel. For example, the method 1200 may further include: directing (1212) a second input light beam of a second color channel in a second input linear waveguide of the waveguide illuminator; splitting (1214) the second input beam into a plurality of beamlets; directing (1216) a plurality of sub-beams of a second input light beam in a plurality of second linear waveguides of the waveguide illuminator to a slab waveguide region of the waveguide illuminator; propagating (1218) a plurality of sub-beams of the second input light beam in the slab waveguide region to form a second output light beam propagating in the slab waveguide region; and coupling out (1220) portions of the second output beam to form a second array of coupled-out beam portions. A linear waveguide structure may be disposed in the linear waveguide region 101 of the waveguide illuminator 100. Method 1200 may be performed with any waveguide illuminator contemplated herein.

Turning to fig. 13, a Virtual Reality (VR) near-eye display 1300 includes a frame 1301 supporting for each eye: a light source 1302; a waveguide illuminator 1306 operably coupled to the light source 1302 and comprising any of the waveguide illuminators disclosed herein; a display panel 1318 comprising an array of display pixels, wherein the position of the out-coupling grating in the waveguide illuminator 1306 matches the position of the polarization modifying pixels of the display panel 1318; and a visual lens 1332 for converting an image in the linear domain generated by the display panel 1318 into an image in the angular domain for direct viewing at the eyebox 1326. A plurality of eyebox illuminators 1362 (shown as black dots) may be placed on the side of illuminator 1306 facing eyebox 1326. An eye tracking camera 1342 may be provided for each eye-ward region 1326.

The purpose of the eye tracking camera 1342 is to determine the position and/or orientation of the user's two eyes. The eyebox illuminator 1362 illuminates the eye at the respective eyebox 1336, allowing the eye tracking camera 1342 to obtain an image of the eye, and provide reference reflection, i.e., glints. The glints may be used as reference points in the captured eye images to facilitate the determination of the eye gaze direction by determining the position of the pupil image relative to the glint image. To avoid distracting the light of the eyebox illuminator 1362 from the user, the eyebox illuminator 1362 may be caused to emit light that is not visible to the user. For example, infrared light may be used to illuminate the eyebox 1336.

Referring now to fig. 14, hmd 1400 is an example of an AR/VR wearable display system that encloses a user's face to more immerse the user in an AR/VR environment. HMD 1400 may generate a fully virtual 3D image. HMD 1400 may include a front body 1402 and a belt 1404 that may be secured around a user's head. The front body 1402 is configured for placement in front of the user's eyes in a reliable and comfortable manner. A display system 1480 may be provided in the front body 1402 for presenting AR/VR images to a user. The display system 1480 may include any of the display devices and illuminators disclosed herein. The side 1406 of the front body 1402 may be opaque or transparent.

In some embodiments, the front body 1402 includes a locator 1408, an inertial measurement unit (Inertial Measurement Unit, IMU) 1410 for tracking acceleration of the HMD 1400, and a position sensor 1412 for tracking a position of the HMD 1400. The IMU1410 is an electronic device that generates data indicative of a position of the HMD 1400 based on received measurement signals from one or more position sensors 1412 that generate one or more measurement signals in response to motion of the HMD 1400. Examples of the position sensor 1412 include: one or more accelerometers, one or more gyroscopes, one or more magnetometers, another suitable type of sensor that detects motion, a type of sensor for error correction of the IMU1410, or some combination thereof. The position sensor 1412 may be located external to the IMU1410, internal to the IMU1410, or some combination thereof.

The locator 1408 is tracked by an external imaging device of the virtual reality system so that the virtual reality system can track the position and orientation of the entire HMD 1400. The information generated by the IMU1410 and the position sensor 1412 may be compared to the position and orientation acquired by the tracking locator 1408 to improve the tracking accuracy of the position and orientation of the HMD 1400. As the user moves and rotates in 3D space, the exact position and orientation is important for presenting the user with the proper virtual scene.

The HMD 1400 may also include a depth camera assembly (Depth Camera Assembly, DCA) 1411 that collects data describing depth information of some or all surrounding local areas of the HMD 1400. The depth information may be compared to information from IMU 1410 to more accurately determine the position and orientation of HMD 1400 in 3D space.

The HMD 1400 may also include an eye-tracking system 1414 for determining the orientation and position of a user's eyes in real-time. The obtained position and orientation of the eyes also allows the HMD 1400 to determine the gaze direction of the user and adjust the image generated by the display system 1480 accordingly. The determined gaze direction and convergence angle may be used to adjust the display system 1480 to reduce convergence adjustment conflicts. As disclosed herein, direction and convergence may also be used for exit pupil steering of a display. Further, the determined vergence angle and gaze angle may be used to interact with a user, highlight an object, bring an object to the foreground, create additional objects or pointers, and so forth. An audio system may also be provided, including, for example, a set of small speakers built into the front body 1402.

Embodiments of the present disclosure may include or be implemented in conjunction with an artificial reality system. The artificial reality system adjusts sensory information (e.g., visual information, audio, touch (somatosensory) information, acceleration, balance, etc.) about the outside, acquired through sensing, in some way before being presented to the user. As non-limiting examples, artificial Reality may include Virtual Reality (VR), augmented Reality (AR), mixed Reality (MR), mixed Reality (Hybrid Reality), or some combination and/or derivative thereof. The artificial reality content may include entirely generated content or generated content combined with collected (e.g., real world) content. The artificial reality content may include video, audio, somatic feedback or haptic feedback, or some combination thereof. Any of these content may be presented in a single channel or in multiple channels (e.g., in stereoscopic video that produces a three-dimensional effect to the viewer).

Further, in some embodiments, the artificial reality may also be associated with an application, product, accessory, service, or some combination thereof, for creating content in the artificial reality and/or otherwise for use in the artificial reality (e.g., performing an activity in the artificial reality), for example. The artificial reality system providing artificial reality content may be implemented on a variety of platforms including a wearable display (e.g., an HMD connected to a host computer system), a stand-alone HMD, a near-eye display with a form factor of glasses, a mobile device or computing system, or any other hardware platform capable of providing artificial reality content to one or more viewers.

The scope of the present disclosure is not limited to the specific embodiments described herein. Indeed, various other embodiments and modifications to the embodiments in addition to those described herein will be apparent to those of ordinary skill in the art from the foregoing description and accompanying drawings. Accordingly, such other embodiments and modifications are intended to fall within the scope of this disclosure. Furthermore, although the present disclosure has been described herein in the context of a particular implementation in a particular environment for a particular purpose, those of ordinary skill in the art will recognize that the usefulness of the present disclosure is not limited thereto and that the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Accordingly, the claims set forth below should be construed in view of the full breadth of the present disclosure as described herein.

Claims

1. A waveguide illuminator, the waveguide illuminator comprising:

adjacent linear waveguide regions and slab waveguide regions;

a first input waveguide in the linear waveguide region for guiding a first input light beam;

a first beam splitter coupled to the first input waveguide for splitting the first input beam into a plurality of sub-beams;

a plurality of first linear waveguides located in the linear waveguide region, coupled to the first beam splitter, for receiving the plurality of beamlets split from the first input light beam and directing the plurality of beamlets to boundaries between the linear waveguide region and the slab waveguide region to form a first output light beam propagating in the slab waveguide region; and

a first array of couplers, each coupler being spaced apart from one another in the slab waveguide region, the first array of couplers being for coupling out portions of the first output beam to form a first array of coupled-out beam portions.

2. The waveguide illuminator of claim 1, wherein each linear waveguide of the first plurality of linear waveguides comprises a taper located at a boundary between the linear waveguide region and the slab waveguide region for expanding the plurality of beamlets prior to coupling into the slab waveguide region.

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

4. A waveguide illuminator according to claim 1, 2 or 3, wherein the first array of outcouplers comprises a plurality of grating outcouplers for coupling out portions of the first output beam to form a first array of coupled-out beam portions.

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

6. The waveguide illuminator of claim 4 or 5, wherein at least one of the following is present:

the plurality of grating couplers are chirped to focus the coupled beam portions; or (b)

The waveguide illuminator includes a microlens array coupled to the plurality of grating couplers to focus the coupled beam portions;

the waveguide illuminator further comprises a color-selective redirector array downstream of the plurality of grating couplers, configured such that light of a first color channel, light of a second color channel, and light of a third color channel downstream of the color-selective redirector array propagate at substantially the same chief ray angle; preferably, the method comprises the steps of,

wherein the color selection redirector array comprises: a microprism array; or a chirped grating array.

7. The waveguide illuminator of any one of the preceding claims, wherein the first input beam carries light of a first color channel, the waveguide illuminator further comprising:

a second input waveguide in the linear waveguide region for guiding a second input light beam of a second color channel;

A second beam splitter located in the linear waveguide region, coupled to the second input waveguide, for splitting the second input beam into a plurality of sub-beams;

a plurality of second linear waveguides located in the linear waveguide region, coupled to the second beam splitter, for receiving the plurality of beamlets split from the second input beam and directing the plurality of beamlets to boundaries between the linear waveguide region and the slab waveguide region to form a second output beam propagating in the slab waveguide region; and

and a second array of couplers, each coupler being spaced apart from the other in the slab waveguide region, the second array of couplers being for coupling out portions of the second output beam to form a second array of coupled-out beam portions.

8. The waveguide illuminator of claim 7, wherein:

the slab waveguide region includes a first slab waveguide layer and a second slab waveguide layer for guiding the first output beam and the second output beam in the first slab waveguide layer and the second slab waveguide layer, respectively;

The plurality of first linear waveguides and the plurality of second linear waveguides are coupled to the first planar waveguide layer and the second planar waveguide layer, respectively; and is also provided with

The first array of outcouplers and the second array of outcouplers are disposed in the first and second planar waveguide layers, respectively, and are configured to couple out portions of the first output beam and portions of the second output beam, respectively, at substantially the same chief ray angle.

9. The waveguide illuminator of claim 7 or 8, wherein:

the slab waveguide region supports a first transverse propagation mode and a second transverse propagation mode;

the plurality of first linear waveguides and the plurality of second linear waveguides are configured to couple a respective plurality of beamlets into a first transverse mode and a second transverse mode, respectively; and is also provided with

The first array of outcouplers and the second array of outcouplers are configured to couple out portions of the first output beam and portions of the second output beam, respectively, at substantially the same chief ray angle.

10. The waveguide illuminator of any of the preceding claims, wherein:

The slab waveguide region includes a slab waveguide layer for propagating the first output beam in the slab waveguide layer; and is also provided with

The first array of couplers includes an array of prisms evanescently coupled to the slab waveguide layer, the array of prisms for coupling out portions of the first output beam from the waveguide illuminator to form a first array of coupled-out beam portions.

11. A display device, the display device comprising:

a waveguide illuminator, the waveguide illuminator comprising:

adjacent linear waveguide regions and slab waveguide regions;

an input waveguide in the linear waveguide region for guiding an input light beam;

a first beam splitter coupled to the input waveguide for splitting the input beam into a plurality of sub-beams;

a plurality of linear waveguides located in the linear waveguide region, coupled to the first beam splitter, for receiving the plurality of beamlets split from the input light beam and directing the plurality of beamlets to boundaries between the linear waveguide region and the slab waveguide region to form an output light beam propagating in the slab waveguide region; and

An array of couplers, each coupler being spaced apart from one another in the slab waveguide region, the array of couplers being for coupling out portions of the output beam to form an array of coupled-out beam portions; and

a display panel comprising an array of display pixels arranged and configured to receive an array of coupled beam portions.

12. The display device of claim 11, wherein a pitch of each display pixel is substantially equal to a pitch of the array of outcouplers.

13. The display device of claim 11 or 12, further comprising a light source for providing the input light beam to the input waveguide; preferably:

i. wherein the light source is a polarized light source, wherein the array of the input and output light beams and the coupled-out beam portions are polarized;

wherein the array of display pixels comprises an array of adjustable polarization rotators for adjusting the polarization of individual beam portions of the array of coupled beam portions; and/or

Wherein the light source comprises a monochromatic light source, wherein the input light beam has a wavelength of a first color channel.

14. A method for illuminating a display panel, the method comprising:

directing a first input light beam in a first input linear waveguide of a waveguide illuminator;

splitting the first input beam into a plurality of sub-beams;

directing the plurality of beamlets of the first input light beam in a plurality of first linear waveguides of the waveguide illuminator to a slab waveguide region of the waveguide illuminator;

propagating the plurality of beamlets of the first input beam in the slab waveguide region to form a first output beam propagating in the slab waveguide region; and

portions of the first output beam are coupled out to form a first array of coupled-out beam portions.

15. The method of claim 14, the method further comprising:

i. expanding the plurality of beamlets in waveguide tapers of the plurality of first linear waveguides prior to coupling the plurality of beamlets to the slab waveguide region; and/or

Directing a second input light beam in a second input linear waveguide of the waveguide illuminator;

splitting the second input beam into a plurality of sub-beams;

directing the plurality of beamlets of the second input light beam in a plurality of second linear waveguides of the waveguide illuminator to a slab waveguide region of the waveguide illuminator;

Propagating the plurality of beamlets of the second input beam in the slab waveguide region to form a second output beam propagating in the slab waveguide region; and

portions of the second output beam are coupled out to form a second array of coupled-out beam portions.