PATENT DOCUMENT

Publication Number: US-11803056-B2
Application Number: US-201916546157-A
Country: US
Kind Code: B2

Title: Waveguided display systems

Abstract:
An electronic device may have a display that emits image light, a waveguide, and an input coupler that couples the image light into the waveguide. Beam splitter structures may be embedded within the waveguide. The beam splitter structures may partially reflect the image light multiple times and may serve to generate replicated beams of light that are coupled out of the waveguide by an output coupler. The beam splitter structures may replicate the beams across two dimensions to provide an eye box with uniform-intensity light from the display across its area. The beam splitter structures may include stacked partially reflective beam splitter layers, sandwiched transparent substrate layers having different indices of refraction, a thick volume hologram interposed between substrate layers, or combinations of these or other structures. The reflectivity of the beam splitter structures may vary discretely or continuously across the lateral area of the waveguide.

Claims:
What is claimed is: 
     
       1. An electronic device comprising:
 a display configured to emit light; 
 a waveguide having a first surface and a second surface opposite and parallel to the first surface and having no air gap between the first surface and the second surface; 
 an optical coupler configured to couple the light emitted by the display into the waveguide; 
 a first beam splitter embedded in the waveguide and extending parallel to the first surface; and 
 a second beam splitter embedded in the waveguide and extending parallel to the second surface, wherein the second beam splitter at least partially overlaps the first beam splitter, the first beam splitter is configured to transmit a first portion of the light at a wavelength to the second beam splitter and is configured to reflect a second portion of the light at the wavelength, and the second beam splitter is configured to partially reflect the first portion of the light transmitted by the first beam splitter. 
 
     
     
       2. The electronic device defined in  claim 1 , wherein the waveguide comprises first and second transparent substrates, the first beam splitter is disposed on the first transparent substrate, the second beam splitter is disposed on the second transparent substrate, the second transparent substrate is mounted to the first transparent substrate, and the second transparent substrate is interposed between the first and second beam splitters. 
     
     
       3. The electronic device defined in  claim 2 , wherein the waveguide further comprises a third transparent substrate mounted to the second transparent substrate, wherein the second beam splitter is interposed between the second and third transparent substrates. 
     
     
       4. The electronic device defined in  claim 2 , further comprising:
 a third beam splitter embedded in the waveguide, wherein the third beam splitter is disposed on the first transparent substrate and is laterally displaced from the first beam splitter. 
 
     
     
       5. The electronic device defined in  claim 1 , wherein the second beam splitter completely overlaps the first beam splitter. 
     
     
       6. The electronic device defined in  claim 1 , further comprising:
 a third beam splitter embedded in the waveguide, wherein the third beam splitter at least partially overlaps the second beam splitter. 
 
     
     
       7. The electronic device defined in  claim 6 , wherein the third beam splitter completely overlaps the second beam splitter. 
     
     
       8. The electronic device defined in  claim 6 , wherein the third beam splitter completely overlaps the first and second beam splitters. 
     
     
       9. The electronic device defined in  claim 1 , wherein the first and second beam splitters each comprise a metallic coating. 
     
     
       10. The electronic device defined in  claim 1 , wherein the first and second beam splitters each comprise a dielectric coating. 
     
     
       11. The electronic device defined in  claim 1 , wherein the first and second beam splitters each comprise a surface hologram. 
     
     
       12. The electronic device defined in  claim 1 , wherein the first beam splitter has opposing first and second ends, a first reflection coefficient at the first end, and a second reflection coefficient at the second end that is different than the first reflection coefficient. 
     
     
       13. The electronic device defined in  claim 12 , wherein the first reflection coefficient is greater than the second reflection coefficient. 
     
     
       14. The electronic device defined in  claim 13 , wherein the first beam splitter comprises a first region having the first reflection coefficient, a second region having the second reflection coefficient, and a third region having a third reflection coefficient that is less than the first reflection coefficient and greater than the second reflection coefficient, the third region being interposed between the first and second regions. 
     
     
       15. The electronic device defined in  claim 13 , wherein the first beam splitter has a continuously variable reflection coefficient that varies from the first reflection coefficient at the first end to the second reflection coefficient at the second end. 
     
     
       16. The electronic device of  claim 1 , further comprising an additional optical coupler configured to couple the light out of the display after reflection of the light by the second beam splitter. 
     
     
       17. The electronic device of  claim 16 , wherein the additional optical coupler comprises a diffraction grating and wherein the diffraction grating comprises a volume hologram.

Description:
This application claims the benefit of provisional patent application No. 62/731,309, filed Sep. 14, 2018, which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     This relates generally to electronic devices and, more particularly, to electronic devices with displays. 
     Electronic devices with displays may be used to display content for a user. If care is not taken, the components used in displaying content for a user in an electronic device may be unsightly and bulky and may not exhibit desired levels of optical performance. 
     SUMMARY 
     An electronic device may have a display that emits image light, a waveguide, and an input coupler that couples the image light into the waveguide. Beam splitter structures may be embedded within the waveguide. The beam splitter structures may reflect the image light multiple times and may serve to generate replicated beams of light (e.g., expanded output light) that are coupled out of the waveguide by an output coupler. The beam splitter structures may replicate the beams across two dimensions (e.g., across the lateral area of the waveguide). In this way, an eye box may be provided with uniform-intensity light from the display across its area and for a wide field of view. 
     The beam splitter structures may include stacked beam splitter layers. For example, first and second partially reflective beam splitter layers may be embedded in the waveguide. The second beam splitter layer may partially or completely overlap the first beam splitter layer. Additional beam splitter layers may be stacked over the first and second beam splitter layers or laterally displaced with respect to the first and/or second beam splitter layers. 
     In another suitable arrangement, the beam splitter structures may be formed from first, second, and third transparent substrate layers of the waveguide. In this scenario, each transparent substrate layer may have a respective index of refraction so that interfaces between the substrate layers generate reflected light that is coupled out of the waveguide. 
     In yet another suitable arrangement, the beam splitter structures may include a thick volume hologram interposed between two transparent substrate layers. In this scenario, the thick volume hologram layer may partially reflect the image light at multiple depths relative to one of the substrate layers as the image light traverses the thickness of the thick volume hologram layer. Combinations of these arrangements may be used to form the beam splitter structures. If desired, the reflectivity of the beam splitter structures may vary discretely or continuously across the lateral area of the waveguide. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram of an illustrative head-mounted device in accordance with an embodiment. 
         FIG.  2    is a diagram of an illustrative head-mounted device for a single eye in accordance with an embodiment. 
         FIG.  3    is a top view of an illustrative optical system and associated display system for a head-mounted device in accordance with an embodiment. 
         FIG.  4    is a top view of an illustrative optical system having a waveguide without beam splitter structures in accordance with an embodiment. 
         FIG.  5    is a top view of an illustrative optical system having beam splitter structures embedded within a waveguide for filling an eye box with light in accordance with an embodiment. 
         FIG.  6    is a top view of illustrative beam splitter structures having a single beam splitter layer embedded within a waveguide in accordance with an embodiment. 
         FIG.  7    is a top view of illustrative beam splitter structures having multiple stacked beam splitter layers embedded within a waveguide in accordance with an embodiment. 
         FIG.  8    is a top view of illustrative beam splitter structures having multiple stacked and laterally-offset beam splitter layers embedded within a waveguide in accordance with an embodiment. 
         FIG.  9    is a top view of illustrative beam splitter structures having multiple partially-overlapping beam splitter layers embedded within a waveguide in accordance with an embodiment. 
         FIG.  10    is a top view of illustrative beam splitter structures having multiple layers with different indices of refraction in accordance with an embodiment. 
         FIG.  11    is a top view of illustrative beam splitter structures having a thick volume hologram embedded within a waveguide in accordance with an embodiment. 
         FIG.  12    is a top view of illustrative beam splitter structures having a single beam splitter layer with regions having different reflection and transmission coefficients in accordance with an embodiment. 
         FIG.  13    is a top view of illustrative beam splitter structures having a single beam splitter layer with continuously varying transmission and reflection coefficients along their length in accordance with an embodiment. 
         FIG.  14    is a perspective view of a waveguide of the type shown in  FIG.  4    in accordance with an embodiment. 
         FIG.  15    is a perspective view showing how a waveguide of the types shown in  FIGS.  5 - 14    may fill an eye box with light across two dimensions in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices such as head-mounted devices and other devices may be used for augmented reality and virtual reality systems. These devices may include portable consumer electronics (e.g., portable electronic devices such as tablet computers, cellular telephones, glasses, other wearable equipment, etc.), head-up displays in cockpits, vehicles, etc., and display-based equipment (televisions, projectors, etc.). Devices such as these may include displays and other optical components. Device configurations in which virtual reality and/or augmented reality content is provided to a user with a head-mounted display device are described herein as an example. This is, however, merely illustrative. Any suitable equipment may be used in providing a user with virtual reality and/or augmented reality content. 
     A head-mounted device such as a pair of augmented reality glasses that is worn on the head of a user may be used to provide a user with computer-generated content that is overlaid on top of real-world content. The real-world content may be viewed directly by a user through a transparent portion of an optical system. The optical system may be used to route images from one or more pixel arrays or a scanning device in a display system to the eyes of a viewer. A waveguide such as a thin planar waveguide formed from one or more sheets of transparent material such as glass or plastic or other light guide may be included in the optical system to convey image light from the pixel arrays to the viewer. 
     The illumination system may include a light source that supplies illumination for the display. The illuminated display produces image light. An input optical coupler may be used to couple light from the light source into a waveguide in the illumination system. An output optical coupler may be used to couple display illumination out of the waveguide. Input and output couplers may also be used to couple image light from the display into a waveguide in the optical system and to couple the image light out of the waveguide for viewing by the viewer. 
     The input and output couplers for the head-mounted device may form structures such as Bragg gratings, prisms, angled transparent structures, and/or lenses that couple light into the waveguide and that couple light out of the waveguide. Input and output optical couplers may be formed from diffractive couplers such as volume holograms, other holographic coupling elements, or other diffractive coupling structures. The input and output couplers may, for example, be formed from thin or thick layers of photopolymers and/or other optical coupler structures in which holographic patterns are recorded using lasers. In some configurations, optical couplers may be formed from dynamically adjustable devices such as liquid crystal components (e.g., tunable liquid crystal gratings, polymer dispersed liquid crystal devices), or other adjustable optical couplers. 
     A schematic diagram of an illustrative head-mounted device is shown in  FIG.  1   . As shown in  FIG.  1   , head-mounted device  10  may have control circuitry  12 . Control circuitry  12  may include storage and processing circuitry for controlling the operation of head-mounted display  10 . Circuitry  12  may include storage such as hard disk drive storage, nonvolatile memory (e.g., electrically-programmable-read-only memory configured to form a solid state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in control circuitry  12  may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio chips, graphics processing units, application specific integrated circuits, and other integrated circuits. Software code may be stored on storage in circuitry  12  and run on processing circuitry in circuitry  12  to implement operations for head-mounted display  10  (e.g., data gathering operations, operations involving the adjustment of components using control signals, image rendering operations to produce image content to be displayed for a user, etc.). 
     Head-mounted device  10  may include input-output circuitry  14 . Input-output circuitry  14  may be used to allow data to be received by head-mounted display  10  from external equipment (e.g., a tethered computer, a portable device such as a handheld device or laptop computer, or other electrical equipment) and to allow a user to provide head-mounted device  10  with user input. Input-output circuitry  14  may also be used to gather information on the environment in which head-mounted device  10  is operating. Output components in circuitry  14  may allow head-mounted device  10  to provide a user with output and may be used to communicate with external electrical equipment. 
     As shown in  FIG.  1   , input-output circuitry  14  may include one or more displays such as display(s)  18 . Display(s)  18  may be used to display images for a user of head-mounted device  10 . Display(s)  18  have pixel array(s) or laser scanning patterns to generate images that are presented to a user through an optical system. The optical system may, if desired, have a transparent portion through which the user (viewer) can observe real-world objects while computer-generated content is overlaid on top of the real-world objects by producing computer-generated images on the display(s)  18 . 
     Optical components  16  may be used in forming the optical system that presents images to the user. Components  16  may include static components such as waveguides, beam splitter structures embedded in waveguides, static optical couplers, and fixed lenses. Components  16  may also include adjustable optical components such as an adjustable polarizer, tunable lenses (e.g., liquid crystal tunable lenses, tunable lenses based on electrooptic materials, tunable liquid lenses, or other tunable lenses), a dynamically adjustable coupler (e.g., an adjustable MEMs grating or other coupler), an adjustable liquid crystal holographic coupler such as an adjustable liquid crystal Bragg grating coupler, adjustable holographic couplers (e.g., electro-optical devices such as tunable Bragg grating couplers, polymer dispersed liquid crystal devices, etc.), couplers, lenses, and other optical devices formed from electro-optical materials (e.g., lithium niobate or other materials exhibiting the electro-optic effect), or other static and/or tunable optical components. Components  16  may be used in proving light to display(s)  18  to illuminate display(s)  18  and in may be used in providing images from display(s)  18  to a user for viewing. In some configurations, one or more of components  16  may be stacked, so that light passes through multiple components in series. In other configurations, components may be spread out laterally (e.g., multiple displays may be arranged on a waveguide or set of waveguides using a tiled set of laterally adjacent couplers). Configurations may also be used in which both tiling and stacking are present. 
     Input-output circuitry  14  may include components such as input-output devices  22  for gathering data and user input and for supplying a user with output. Devices  22  may include sensors  26 , audio components  24 , and other components for gathering input from a user or the environment surrounding device  10  and for providing output to a user. Devices  22  may, for example, include keyboards, buttons, joysticks, touch sensors for trackpads and other touch sensitive input devices, cameras, light-emitting diodes, and/or other input-output components. 
     Cameras or other devices in input-output circuitry  14  may face a user&#39;s eyes and may track a user&#39;s gaze. Sensors  26  may include position and motion sensors (e.g., compasses, gyroscopes, accelerometers, and/or other devices for monitoring the location, orientation, and movement of head-mounted display  10 , satellite navigation system circuitry such as Global Positioning System circuitry for monitoring user location, etc.). Using sensors  26 , for example, control circuitry  12  can monitor the current direction in which a user&#39;s head is oriented relative to the surrounding environment. Movements of the user&#39;s head (e.g., motion to the left and/or right to track on-screen objects and/or to view additional real-world objects) may also be monitored using sensors  26 . 
     If desired, sensors  26  may include ambient light sensors that measure ambient light intensity and/or ambient light color, force sensors, temperature sensors, touch sensors, capacitive proximity sensors, light-based proximity sensors, other proximity sensors, strain gauges, gas sensors, pressure sensors, moisture sensors, magnetic sensors, etc. Audio components  24  may include microphones for gathering voice commands and other audio input and speakers for providing audio output (e.g., ear buds, bone conduction speakers, or other speakers for providing sound to the left and right ears of a user). If desired, input-output devices  22  may include haptic output devices (e.g., vibrating components), light-emitting diodes and other light sources, and other output components. Circuitry  14  may include wired and wireless communications circuitry  20  that allows head-mounted display  10  (e.g., control circuitry  12 ) to communicate with external equipment (e.g., remote controls, joysticks and other input controllers, portable electronic devices, computers, displays, etc.) and that allows signals to be conveyed between components (circuitry) at different locations in head-mounted display  10 . 
     The components of head-mounted display  10  may be supported by a head-mountable support structure such as illustrative support structure  28  of  FIG.  2   . Support structure  28 , which may sometimes be referred to as a housing, may be configured to form a frame of a pair of glasses (e.g., left and right temples and other frame members), may be configured to form a helmet, may be configured to form a pair of goggles, or may have other head-mountable configurations. 
     Optical system  33  may be supported within support structure  28  and may be used to provide images from display(s)  18  to a user (see, e.g., the eyes of user  42  of  FIG.  2   ). With one illustrative configuration, display(s)  18  may be located in outer (edge) portions  38  of optical system  33  and may have one or more pixel arrays that produce images. Light associated with the images may be coupled into waveguides in outer portions  38  using input coupler systems. The light within the waveguide may traverse intermediate regions  32 . In central portion(s)  34  of system  33  (at the opposing ends of the waveguides from the input coupler systems and display(s)  18 ), output coupler systems formed from one or more output couplers may couple the light out of the waveguide. This light may pass through optional lenses  30  in direction  40  for viewing by user  42 . Portion(s)  34  of optical system  33  may be transparent, so that user  42  may view external objects such as object  36  through this region of system  33  while system  33  overlays computer-generated content (image content generated by control circuitry  12  of  FIG.  1   ) with objects such as object  36 . 
       FIG.  3    is a diagram of illustrative components that may be used in forming device  10 . The diagram of  FIG.  3    includes components for one of the user&#39;s eyes. Device  10  may contain two sets of such components to present images to both of a user&#39;s eyes. 
     As shown in  FIG.  3   , device  10  may include a display such as display(s)  18  for producing image light  44 . Image light  44  may be generated by illuminating a reflective display containing an array of pixels, using a scanning device, or using any other desired display components. The images presented on the array of pixels may be conveyed through lens  46  to input coupler  50 , which couples image light  44  into waveguide  48  (e.g., a planar waveguide). The image light coupled into waveguide  48  is confined within waveguide  48  in accordance with the principle of total internal reflection and travels towards output coupler  52  as indicated by light  54 . 
     Output coupler  52  couples light  54  (image light) out of waveguide  48  and towards viewer  42  (an eye of a user), as output light (output image light)  60 . Optional lens  30  may help focus image light for viewer  42 . Input coupler  50  and output coupler  52  may be, for example, structures such as Bragg gratings that couple light into waveguides and that couple light out of the waveguides. Couplers  50  and  52  may be formed from volume holograms or other holographic coupling elements (e.g., thin or thick layers of photopolymers and/or other optical coupler structures in which holographic patterns are recorded using lasers), prisms, angled transparent structures, lenses, or any other desired light coupling elements. Couplers  50  and  52  may have infinite focal lengths (e.g., couplers  50  and  52  may be plane-to-plane couplers) or may have associated finite focal lengths. For example, optical coupler  52  can be powered (e.g., coupler  52  can be configured to form a lens of a desired finite focal length) in which case lens  30  may be omitted or the focal length of lens  30  may be adjusted. 
       FIG.  4    is a diagram showing how light  54  may propagate through waveguide  48  to output coupler  52 . Lenses  46  and  30  and display(s)  18  of  FIG.  3    are not shown in  FIG.  4    for the sake of clarity. As shown in  FIG.  4   , image light  44  may be coupled into waveguide  48  using input coupler  50 . Corresponding light  54  may reflect between surfaces  62  and  64  of waveguide  48  under the principle of total internal reflection (e.g., as light  54  propagates from end  56  to opposing end  58  of waveguide  48 ). Output light  60  may be coupled out of waveguide  48  at one or more locations overlapping output coupler  52  (e.g., at locations overlapping output coupler  52  where light  54  hits surface  64  of waveguide  48 ). 
     In the example of  FIG.  4   , output coupler  52  outputs light  60 - 1  towards eye box  70 . Eye box  70  may be a location at which user  42  ( FIG.  3   ) places their eye for viewing light from display  18 . Eye box  70  has a finite area (width)  72 . In practice, the light that propagates through waveguide  48  has a finite, non-zero beam width. For example, image light  44  may have a corresponding beam area (width)  44 . Similarly, output light  60 - 1  has a beam area (width)  68 - 1 . Beam area  68 - 1  extends over two-dimensions, may sometimes be referred to herein as pupil  68 - 1 , and may correspond to a peak of light intensity that is greater than a threshold intensity. 
     The example of  FIG.  4    is merely illustrative. In general, any desired input and output coupler structures may be used. Couplers  50  and  52  may be formed on surface  62  and/or surface  64  of waveguide  48 . If desired, couplers  50  and/or  52  may be embedded within waveguide  48 . 
     If care is not taken, beam width  68 - 1  may be too small to fill all of eye box  70  with light of uniform intensity (brightness). This may lead to images being displayed with non-uniform brightness across eye box  70 . As the user moves or rotates their eye within eye box  70 , the image will thus appear undesirably dark for some portions of the image. It may therefore be desirable to be able to provide waveguide  48  with structures that allow waveguide  48  to fill eye box  72  with light (e.g., so that a uniform intensity of light is provided across area  72  of eye box  70  for as large an eye box as possible). It may also be desirable to be able to provide eye box  70  with uniform light intensity for a wide field of view  67  of incoming light  44 . 
       FIG.  5    is a diagram showing how waveguide  48  may be provided with structures that allow waveguide  48  to fill a relatively large eye box  70  with uniform light intensity over a wide field of view  67 . Lenses  46  and  30  and display(s)  18  of  FIG.  3    are not shown in  FIG.  5    for the sake of clarity. 
     As shown in  FIG.  5   , beam splitter structures such as beam splitter structures  74  may be embedded within waveguide  48 . Beam splitter structures may be configured to pass (transmit) a first portion of light  54  within waveguide  48  while also reflecting a second portion of light  54 . As shown in  FIG.  5   , light  54  may propagate down the length of waveguide  48  and may pass through beam splitter structures  74 . A portion of this light may be reflected by beam splitter structures  74 , as shown by reflected light  76 . Output coupler  52  may couple reflected light  76  out of waveguide  48  as a beam of output light  60 - 2 . Output light  60 - 2  may have beam area (width)  68 - 2 . Together with output light  60 - 1 , output light  60 - 2  may help to fill eye box  70  with light of uniform intensity across area  72  of eye box  70 . For example, area  68 - 2  of output light  60 - 2  and area  68 - 1  of output light  60 - 1  may cumulatively extend across area  72 . In this way, waveguide  48  may be configured to expand the area within eye box  70  that is filled with image light relative to scenarios where beam splitter structures  74  are omitted. 
     Beam splitter structures  74  may be provided with a selected reflectivity (reflection coefficient R) so that a desired percentage of image light  54  is reflected each time light  54  passes through beam splitter structures  74 . Beam splitter structures  74  may reflect light  54  any desired number of times. Beam splitter structures  74  may, for example, have a length such that multiple reflections of light  54  off of surface  64  of waveguide  48  are reflected towards output coupler  52  as reflected light  76 . A portion of reflected light  76  may also reflect off of surface  64  back towards beam splitter structures  74  and this portion may also be transmitted to surface  62  and/or reflected towards output coupler  52 . Each light reflection off of beam splitter structures  74  and surface  62  that hits output coupler  52  may produce a corresponding beam of output light  60  having a corresponding beam width  68 . Collectively, each of these reflections and beams of output light may help to fill area  72  of eye box  70  with light of uniform intensity. In this way, eye box  70  may be filled with light from a wide field of view  67  and the user may move or rotate their eye within eye box  70  without any undesirable loss in image brightness. 
     The example of  FIG.  5    is merely illustrative. Beam splitter structures  74  may be embedded within waveguide  48 , may be formed as additional layers on surface  62  of waveguide  48  (e.g., external to waveguide  48  so long as total internal reflection is maintained), and/or may be formed as additional layers on surface  64  of waveguide  48  (e.g., external to waveguide  48  so long as total internal reflection is maintained). Any number of reflections from beam splitter structures  74  and surface  62  of waveguide  48  may be coupled out of waveguide  48  as output light  60 . 
     Beam splitter structures  74  may include any desired beam splitter structures.  FIGS.  6 - 13    show examples of different illustrative beam splitter structures for waveguide  48 . In the examples of  FIGS.  6 - 13   , output coupler  52  of  FIG.  5    has been omitted for the sake of clarity. If desired, beam splitter structures  74  may be formed from one or more beam splitter layers embedded within waveguide  48 .  FIG.  6    is a diagram showing how beam splitter structures  74  may include a single beam splitter layer embedded within waveguide  48 . 
     As shown in  FIG.  6   , beam splitter structures  74  may include a single beam splitter layer such as beam splitter layer  84 - 1 . Beam splitter layer  84 - 1  may extend across the entire length of waveguide  48  (e.g., from end  56  to end  58  of  FIG.  5   ) or may be laterally localized within a particular region of waveguide  48 . 
     Waveguide  48  may include one or more stacked transparent layers  80 . Transparent layers  80  may be formed from glass, transparent plastic, sapphire, or any other desired transparent substrate structures. As an example, waveguide  48  may include a first transparent layer  80 - 1  and a second transparent layer  80 - 2 . Beam splitter layer  84 - 1  may be embedded between transparent layers  80 - 1  and  80 - 2  (e.g., beam splitter layer  84 - 1  may be formed on a top surface of layer  80 - 1  and layer  80 - 2  may be laminated, adhered, or attached to layer  80 - 1  over beam splitter layer  84 - 1 ). 
     Beam splitter layer  84 - 1  may reflect a first portion of light  54  towards surface  64 , as shown by reflected light  76 . Beam splitter layer  74  may transmit a second portion of light  54  towards surface  62  of waveguide  48 . The second portion of light  54  may reflect off of surface  62  towards surface  64  and may be coupled out of waveguide  48  as output light  60 - 1  (e.g., a beam of light having beam area  68 - 1 ). Reflected light  76  may be coupled out of waveguide  48  as output light  60 - 2  (e.g., a beam of light having beam area  68 - 1 ). If desired, reflected light  76  may reflect off of surface  64  back towards beam splitter layer  84 - 1  and beam splitter layer  84 - 1  may reflect this light back towards surface  64  for generating additional beam(s) of output light. Beam splitter layer  84 - 1  may have any suitable length for reflecting light out of waveguide  48  any desired number of times. 
     Beam splitter layer  84 - 1  may have a selected reflectivity (e.g., reflection coefficient R and corresponding transmission coefficient T equal to 1−R) such that any desired amount of light  54  is reflected towards surface  64 . Beam splitter layer  84 - 1  may be formed from a dielectric coating, a metallic coating, a thin/surface hologram or diffraction grating, or any other desired structures that reflect and transmit incident light. The properties of beam splitter layer  84 - 1  may be selected to provide beam splitter layer  84 - 1  with any desired reflection and transmission coefficients. If desired, beam splitter structures  74  may include additional stacked and/or laterally offset beam splitter layers to increase the number of beams of output light  60  (e.g., to more uniformly fill eye box  70  of  FIG.  4    relative to scenarios where only a single beam splitter layer is used). 
       FIG.  7    is a diagram showing how beam splitter structures  74  may include multiple stacked beam splitter layers such as an additional beam splitter layers  84 - 2  stacked over beam splitter layer  84 - 1 . As shown in  FIG.  7   , waveguide  48  may include a third transparent layer  80 - 3  over transparent layer  80 - 2 . Beam splitter layer  84 - 2  may completely or at least partially overlap beam splitter layer  84 - 1 . 
     A first portion of light  54  may be reflected off of beam splitter layer  84 - 1  as reflected light  76 - 1 . A second portion of light  54  may be transmitted through beam splitter layer  84 - 1 . A first portion of this light may be reflected off of beam splitter layer  84 - 2  as reflected light  76 - 2 . A second portion of this light may be transmitted through beam splitter layer  84 - 2 , reflected off of surface  62 , and coupled out of waveguide  48  as output light  60 - 1 . Reflected light  76 - 1  may be coupled out of waveguide  48  as output light  60 - 2 . Reflected light  76 - 2  may be coupled out of waveguide  68  as output light  60 - 3  (e.g., a beam of light having beam area  68 - 3 ). 
     Beam splitter layer  84 - 2  may have a selected reflectivity (e.g., reflection coefficient R and corresponding transmission coefficient T) such that any desired amount of light  54  is reflected towards surface  64  and transmitted to surface  62 . Beam splitter layer  84 - 2  may be formed from a dielectric coating, a metallic coating, a thin/surface hologram or diffraction grating, or any other desired structures that reflect and transmit incident light. In this way, multiple beams of output light  60  may be provided to more uniformly fill eye box  70  of  FIG.  4    with image light. Using stacked beam splitter layers in this way may increase the number of reflections and corresponding output beams relative to scenarios where only a single beam splitter layer is used, for example. 
     The example of  FIG.  7    is merely illustrative. In general, waveguide  48  may include any desired number of beam splitter layers  84  and transparent layers  80 . Each beam splitter layer  84  may completely or partially overlap the other beam splitter layers in beam splitter structures  74 . Beam splitter structures  74  may include multiple laterally offset beam splitter layers if desired. 
       FIG.  8    is a diagram showing how beam splitter structures  74  may include multiple stacked and laterally-displaced beam splitter layers. As shown in  FIG.  8   , waveguide  48  may include a fourth transparent layer  80 - 4  over transparent layer  80 - 3 . Beam splitter structures  74  may include three or more stacked beam splitter layers such as beam-splitter layers  84 - 1 ,  84 - 2 , and  84 - 3 . Some of the beam splitter layers such as beam splitter layer  84 - 4  may be laterally displaced (offset) with respect to other beam splitter layers such as beam splitter layer  84 - 1 . 
     As shown in  FIG.  8   , beam splitter layer  84 - 4  may be laterally separated from beam splitter layer  84 - 1  on substrate  80 - 1 . Beam splitter layers  84 - 1  and  84 - 4  may be replaced by one continuous beam splitter layer in another suitable arrangement. One or more beam splitter layers such as beam splitter layer  84 - 5  may be stacked over beam splitter layer  84 - 4  (e.g., beam splitter structures  74  may include any desired number of stacked or individual beam splitter layers formed at one or more different locations along the one or more lateral planes within waveguide  48 ). 
     The example of  FIG.  8    is merely illustrative of different beam splitter layers  84  that may be included in beam splitter structures  74 . One or more of beam splitter layers  84 - 3 ,  84 - 2 ,  84 - 1 ,  84 - 5 , and  84 - 4  may be omitted. Multiple transparent layers  80  may be interposed between adjacent stacked beam splitter layers if desired (e.g., multiple transparent layers  80  may be interposed between beam splitter layers  84 - 1  and  84 - 2 ). In the example of  FIGS.  7  and  8   , each beam splitter layer completely overlaps another beam splitter layer in beam splitter structures  74 . If desired, the beam splitter layers may only partially overlap other beam splitter layers in structures  74 . 
       FIG.  9    is a diagram showing how beam splitter structures  74  may include partially overlapping beam splitter layers. As shown in  FIG.  9   , beam splitter layer  84 - 1  partially overlaps beam splitter layer  84 - 2  which partially overlaps beam splitter layer  84 - 3 . This example is merely illustrative. Beam splitter layers  84 - 1 ,  84 - 2 , and/or  84 - 3  of  FIG.  9    may be omitted if desired. One, two, ore more than two layers  80  may be interposed between beam splitter layers  84 - 1  and  84 - 2 , between beam splitter layers  84 - 2  and  84 - 3 , etc. Additional beam splitter layers may be stacked with and completely or partially overlap one or more of these beam splitter layers (e.g., using combinations of the arrangements of  FIGS.  6 - 9   ). Beam splitter structures  74  may include any desired number of beam splitter arrangements that are at least partially overlapping or non-overlapping. In general, by placing one or more beam splitter layers at one or more desired locations across the lateral surface area of one or more transparent layers  80  in waveguide  48 , a suitable number of output beams  60  may be produced at surface  64  of waveguide  48  to uniformly fill eye box  70  with image light (e.g., the beam widths  68  of each output beam may collectively extend across area  72  of eye box  70 ). 
     The example of  FIGS.  6 - 9    in which beam splitter structures  74  include one or more thin beam splitter layers (e.g., dielectric or metal coatings) is merely illustrative. If desired, beam splitter structures  74  may be formed from layers  80  of waveguide  48  having different indices of refraction (e.g., without dielectric or metal coatings). One or more of beam splitter layers  84  of  FIGS.  6 - 9    may be embedded within a single dielectric layer  80  in waveguide  48  if desired. In this scenario, at least some dielectric material from that single dielectric layer may be interposed between stacked beam splitter layers  84  (e.g., at least some dielectric material from the single dielectric layer may be interposed between beam splitter layers  84 - 1  and  84 - 2  of  FIG.  7   ). Beam splitter layers  84  may include dielectric coatings or hologram reflectors that are configured to partially reflect only light incident at large angles or at specific wavelengths while preserving transmittance for light incident from outside (e.g., to allow for the satisfactory overlay of external world light with image light generated by the display), if desired. In examples where beam splitter layers  84  include metallic coatings, low loss metals can be used (e.g., silver, aluminum, metal layers having reduced area) to reduce optical absorption (e.g., to help hide the metallic coatings from being perceivable to a user). 
       FIG.  10    is a diagram showing how beam splitter structures  74  may be formed from different layers  80  of waveguide  48  having different indices of refraction. As shown in  FIG.  10   , waveguide  48  may have a transparent layer  80 N interposed (sandwiched) between transparent layers  80 - 1  and  80 - 2 . Transparent layer  80 N may have a different index of refraction from the index of refraction of layers  80 - 1  and  80 - 2 . 
     In the example of  FIG.  10   , layer  80 N has an index of refraction N 0 , layer  80 - 1  has an index of refraction N 1 , and layer  80 - 2  has an index of refraction N 2 . As long as these indices of refraction are not equal, light  54  will reflect at the interface between layers  80 - 2  and  80 N and at the interface between layers  80 N and  80 - 1 . The first of these reflections is shown in  FIG.  10    by arrows  83 . Each reflection  83  may be reflected towards surface  64  of waveguide  48  (e.g., by the interface between layers  80 - 1  and  80 -N, the interface between layers  80 N and  80 - 2 , and/or surface  62 ) to produce at least one output beam  60 . Collectively, output beams  60  may exhibit a collective beam area  82  that fills eye box  70  (e.g., beam area  82  may fill area  72  of eye box  70 ). While light  54  is shown as propagating in a straight line in  FIG.  10    for the sake of clarity, the light passing through layer  80 N is refracted at an angle based on the indices of refraction of waveguide  48 . 
     Layer  80 N may be formed from any desired transparent material having index of refraction N 0  (e.g., a non-hologram material). The example of  FIG.  10    is merely illustrative and, if desired, multiple layers such as layer  80 N may be stacked within waveguide  48  and sandwiched between different-index layers  80  (e.g., an additional layer  80 N or other layer having a different index of refraction may be stacked over layer  80 - 2  and/or under layer  80 - 1 , etc.). If desired, layer  80 N may be formed from thick volume hologram having a bulk index of refraction equal to No. In scenarios where beam splitter structures  74  include a thick volume hologram interposed between layers  80 - 1  and  80 - 2 , the thick volume hologram may reflect light at multiple locations across its thickness. 
       FIG.  11    is a diagram showing how beam splitter structures  74  may be formed from a thick volume hologram interposed between layers  80 - 1  and  80 - 2 . As shown in  FIG.  11   , a thick volume hologram layer  88  may be interposed between  80 - 1  and  80 - 2 . Thick volume hologram layer  88  may have thickness  90  that is greater than the thickness of beam splitter layers  84  of  FIGS.  6 - 9   . If desired, thickness  90  may be greater than the thicknesses of layers  80 - 1  or  80 - 2 . 
     A portion of light  54  may reflect (leak) towards surface  64  of waveguide  48  at multiple points along the path of light  54  through layer  88  (e.g., along thickness  90 ), as shown by arrows  89 . Each reflected portion  89  of light  54  may generate a corresponding output beam  60 , where the output beams  60  have a collective beam area  82  (e.g., such that a continuous beam of light is coupled out of waveguide  48  having beam area  82 ). Beam area  82  may fill eye box  70  with image light of uniform intensity. 
     Beam splitter structures  74  (e.g., beam splitter layers  84  of  FIGS.  6 - 9   , layer  80 N of  FIG.  10   , and/or layer  88  of  FIG.  11   ) may have uniform (constant) reflection and transmission coefficients across their lengths (e.g., parallel to the X-axis of  FIGS.  6 - 11   ). If desired, beam splitter structures  74  (e.g., beam splitter layers  84  of  FIGS.  6 - 9   , layer  80 N of  FIG.  10   , and/or layer  88  of  FIG.  11   ) may exhibit non-uniform (varying) reflection and transmission coefficients across their lengths. This variation in reflection and transmission coefficient may be discrete or continuous. 
       FIG.  12    is a diagram showing how the transmission and reflection coefficients of beam splitter structures  74  may vary discretely across their lengths. As shown in  FIG.  12   , beam splitter structures  74  may include a first portion (region)  94  having a first reflection coefficient R 1  and a first transmission coefficient T 1  and a second portion (region)  96  having a second reflection coefficient R 2  and a second transmission coefficient T 2 . In the example of  FIG.  12   , regions  94  and  96  are shown as being regions of a single beam splitter layer (e.g., beam splitter layer  84 - 1  of  FIG.  6   ) between substrate layers  80 - 2  and  80 - 1 . This is merely illustrative and, if desired, regions  94  and  96  may include multiple beam splitter layers  84  (e.g., as shown in  FIGS.  8  and  9   ), a substrate layer in waveguide  48  (e.g., layer  80 N of  FIG.  10   ), and/or a thick volume hologram (e.g., layer  88  of  FIG.  11   ). 
     Transmission coefficient T 2  may be different than transmission coefficient T 1  and reflection coefficient R 2  may be different than reflection coefficient RE For example, transmission coefficient T 2  may be greater than transmission coefficient T 1  and reflection coefficient R 2  may be less than reflection coefficient R 1  (e.g., R 1  may be 90% whereas R 2  is 10%, R 1  may be between 85% and 95% whereas R 2  is between 5% and 15%, R 1  may be between 50% and 99% whereas R 2  is between 50% and 1%, etc.). 
     As shown in  FIG.  12   , a first portion  95  of image light  54  may be reflected off of region  94  (e.g., proportional to reflection coefficient R 1 ) and a second portion  98  of image light  54  may be transmitted by region  94  (e.g., proportional to transmission coefficient T 1 ). A first portion  97  of light  95  may be reflected off of region  96  (e.g., proportional to reflection coefficient R 2 ) and a second portion  100  of light  95  may be transmitted by region  96  (e.g., proportional to transmission coefficient T 2 ). Light  98  may be coupled out of waveguide  48  as output light  60 - 1  (e.g., having beam area  104 - 1 ) and light  100  may be coupled out of waveguide  48  as output light  60 - 2  (e.g., having beam area  104 - 2 ). Additional reflections off of regions  94  and  96  or other regions in beam splitter structures  74  may produce additional beams of output light. Beam areas  104  may collectively fill area  72  of eye box  70 . 
     In scenarios where the transmission coefficient is too high at the location where light  54  first hits beam splitter structures  74 , there may be excessive output light (beam) density at the left side of beam splitter structures  74  and insufficient output light density at the right side of beam splitter structures  74 . This can reduce the uniformity of the light intensity across eye box  70 . By varying the transmission and reflection coefficients in this way, beam splitter structures  74  may provide more uniform beam replication across their lengths. 
     Regions  94  and  96  may be provided with different reflection and transmission coefficients by adjusting the dielectric or metal coating used to form beam splitter structures  84  of  FIGS.  6 - 9    (e.g., so that the coating reflects or passes more or less light), adjusting the indices of refraction of  FIG.  10   , and/or by providing different thick volume hologram structures of  FIG.  11    in each of the regions. The example of  FIG.  12    is merely illustrative. If desired, beam splitter structures  74  may include any desired number of discrete regions having different reflection and transmission coefficients such as regions  94  and  96  (e.g., three regions, four regions, more than four regions, etc.). The regions may have decreasing reflection coefficients as light  54  propagates down waveguide  48 , for example. 
     If desired, beam splitter structures  74  may have continuously varying reflection and transmission coefficients.  FIG.  13    is a diagram showing how the transmission and reflection coefficients of beam splitter structures  74  may vary continuously across their lengths. As shown in  FIG.  13   , beam splitter structures  74  may have a relatively high reflection coefficient RH (e.g., 90%, between 85% and 95%, between 50% and 99%, etc.) and a relatively low transmission coefficient T 1  at the left end. Beam splitter structures  74  may have a relatively low reflection coefficient RL and a relatively high transmission coefficient TH (e.g., 90%, between 85% and 95%, between 50% and 99%, etc.) at the right end. The transmission and reflection coefficients of beam splitter structures  74  may vary continuously from RH and TL to RL and TH along the X-axis of  FIG.  13   . This may help to provide uniform beam replication density across the length of beam splitter structures  74 , for example. 
     In the example of  FIG.  13   , beam splitter structures  74  are shown as including a single beam splitter layer (e.g., beam splitter layer  84 - 1  of  FIG.  6   ) between substrate layers  80 - 2  and  80 - 1 . This is merely illustrative and, if desired, beam splitter structures  74  of  FIG.  13    may include multiple beam splitter layers  84  (e.g., as shown in  FIGS.  6 - 9   ), a substrate layer in waveguide  48  (e.g., layer  80 N of  FIG.  10   ), and/or a thick volume hologram (e.g., layer  88  of  FIG.  11   ). In another suitable arrangement, holograms with varying efficiency across the lateral area of the beam splitter structures may be used to produce beam splitter structures with varying reflectivity. Different reflection coefficients may be established by using different masking operations to deposit more dielectric or metallic coating material at different locations across the lateral area of the beam splitter structures, by using different holograms at different locations across the lateral area of the beam splitter structures, by using more stacked holograms at some locations across the lateral area of the beam splitter structures than others, by varying the relative indices of refraction between the layers of waveguide  48  across the lateral area of the beam splitter structures, etc. 
     In general, any desired combination of the arrangements of  FIGS.  6 - 13    may be used to form beam splitter structures  74  (e.g., using one or more beam splitter layers  84 , one or more sandwiched substrate layers  80 N, and/or one or more thick volume holograms  88  having constant reflection coefficients or discretely/continuously varying reflection coefficients). Each of these structures may be stacked, partially overlapping, completely overlapping, or non-overlapping with one or more (e.g., all) of the other structures in beam splitter structures  74 . 
     In the example of  FIGS.  6 - 13   , beam splitter structures  74  are illustrated as expanding the light used to fill eye box  70  along a single dimension (e.g., parallel to the X-axis). This is merely illustrative. In general, if desired, beam splitter structures  74  may expand the light in two dimensions (e.g., parallel to the X-axis and the Y-axis). 
       FIG.  14    is a perspective view of a waveguide  48  in the absence of beam splitter structures  74 . As shown in  FIG.  14   , image light  66  having beam area  44  is coupled into waveguide  48  and corresponding light  54  propagates down the length of waveguide  48 . The light is coupled out of waveguide  48  as output light  60 - 1  having beam area  68 - 1 . Output light  60 - 1  is provided to eye box  70  ( FIG.  4   ). Beam area  68 - 1  may be insufficient to cover all of area  72  of eye box  70 . 
       FIG.  15    is a perspective view of waveguide  48  having beam splitter structures  74 . As shown in  FIG.  15   , image light  66  may be coupled into waveguide  48  and corresponding light  54  may propagate down the length of waveguide  48  (e.g., parallel to the X-axis of  FIG.  15   ). When light  54  hits beam splitter structures  74 , beam splitter structures  74  may generate reflections in a first direction (e.g., a horizontal direction parallel to the X-axis), as shown by arrows  112 , and in a second direction (e.g., a vertical direction parallel to the Y-axis), as shown by arrows  114 . The reflections in the second direction may continue to occur as the light propagates in the first direction (e.g., so that light is reflected along the two-dimensional lateral surface of the beam splitter structures). These reflections may produce output beams  60  (e.g., output beams  60 - 1 ,  60 - 2 ,  60 - 3 , and  60 - 4  shown in  FIG.  15   ) across the two-dimensional lateral area of beam splitter structures  74 . Each output beam  60  may have a corresponding beam area  68  (e.g., beam areas  68 - 1 ,  68 - 2 ,  68 - 3 , and  68 - 4  shown in  FIG.  15   ). 
     Cumulatively, beam areas  68  may provide uniform light intensity across collective area  116  in two dimensions (e.g., within the X-Y plane). This may allow the output light to fill the two-dimensional area  72  of eye box  70  with uniform intensity. In this way, beam splitter structures  74  may serve to expand the image light output from waveguide  48  in two dimensions (relative to the arrangement of  FIG.  14   ) to fill a relatively large eye box with light of uniform intensity. This may, for example, allow the user to rotate or move their eyes when looking into the eye box without perceiving drops in image light intensity, even for a relatively large field of view. 
     A physical environment refers to a physical world that people can sense and/or interact with without aid of electronic systems. Physical environments, such as a physical park, include physical articles, such as physical trees, physical buildings, and physical people. People can directly sense and/or interact with the physical environment, such as through sight, touch, hearing, taste, and smell. 
     In contrast, a computer-generated reality (CGR) environment refers to a wholly or partially simulated environment that people sense and/or interact with via an electronic system (e.g., an electronic system including the display systems described herein). In CGR, a subset of a person&#39;s physical motions, or representations thereof, are tracked, and, in response, one or more characteristics of one or more virtual objects simulated in the CGR environment are adjusted in a manner that comports with at least one law of physics. For example, a CGR system may detect a person&#39;s head turning and, in response, adjust graphical content and an acoustic field presented to the person in a manner similar to how such views and sounds would change in a physical environment. In some situations (e.g., for accessibility reasons), adjustments to characteristic(s) of virtual object(s) in a CGR environment may be made in response to representations of physical motions (e.g., vocal commands). 
     A person may sense and/or interact with a CGR object using any one of their senses, including sight, sound, touch, taste, and smell. For example, a person may sense and/or interact with audio objects that create 3D or spatial audio environment that provides the perception of point audio sources in 3D space. In another example, audio objects may enable audio transparency, which selectively incorporates ambient sounds from the physical environment with or without computer-generated audio. In some CGR environments, a person may sense and/or interact only with audio objects. Examples of CGR include virtual reality and mixed reality. 
     A virtual reality (VR) environment refers to a simulated environment that is designed to be based entirely on computer-generated sensory inputs for one or more senses. A VR environment comprises a plurality of virtual objects with which a person may sense and/or interact. For example, computer-generated imagery of trees, buildings, and avatars representing people are examples of virtual objects. A person may sense and/or interact with virtual objects in the VR environment through a simulation of the person&#39;s presence within the computer-generated environment, and/or through a simulation of a subset of the person&#39;s physical movements within the computer-generated environment. 
     In contrast to a VR environment, which is designed to be based entirely on computer-generated sensory inputs, a mixed reality (MR) environment refers to a simulated environment that is designed to incorporate sensory inputs from the physical environment, or a representation thereof, in addition to including computer-generated sensory inputs (e.g., virtual objects). On a virtuality continuum, a mixed reality environment is anywhere between, but not including, a wholly physical environment at one end and virtual reality environment at the other end. 
     In some MR environments, computer-generated sensory inputs may respond to changes in sensory inputs from the physical environment. Also, some electronic systems for presenting an MR environment may track location and/or orientation with respect to the physical environment to enable virtual objects to interact with real objects (that is, physical articles from the physical environment or representations thereof). For example, a system may account for movements so that a virtual tree appears stationery with respect to the physical ground. Examples of mixed realities include augmented reality and augmented virtuality. 
     An augmented reality (AR) environment refers to a simulated environment in which one or more virtual objects are superimposed over a physical environment, or a representation thereof. For example, an electronic system for presenting an AR environment may have a transparent or translucent display through which a person may directly view the physical environment. The system may be configured to present virtual objects on the transparent or translucent display, so that a person, using the system, perceives the virtual objects superimposed over the physical environment. Alternatively, a system may have an opaque display and one or more imaging sensors that capture images or video of the physical environment, which are representations of the physical environment. The system composites the images or video with virtual objects, and presents the composition on the opaque display. A person, using the system, indirectly views the physical environment by way of the images or video of the physical environment, and perceives the virtual objects superimposed over the physical environment. As used herein, a video of the physical environment shown on an opaque display is called “pass-through video,” meaning a system uses one or more image sensor(s) to capture images of the physical environment, and uses those images in presenting the AR environment on the opaque display. Further alternatively, a system may have a projection system that projects virtual objects into the physical environment, for example, as a hologram or on a physical surface, so that a person, using the system, perceives the virtual objects superimposed over the physical environment. 
     An augmented reality environment also refers to a simulated environment in which a representation of a physical environment is transformed by computer-generated sensory information. For example, in providing pass-through video, a system may transform one or more sensor images to impose a select perspective (e.g., viewpoint) different than the perspective captured by the imaging sensors. As another example, a representation of a physical environment may be transformed by graphically modifying (e.g., enlarging) portions thereof, such that the modified portion may be representative but not photorealistic versions of the originally captured images. As a further example, a representation of a physical environment may be transformed by graphically eliminating or obfuscating portions thereof. 
     An augmented virtuality (AV) environment refers to a simulated environment in which a virtual or computer generated environment incorporates one or more sensory inputs from the physical environment. The sensory inputs may be representations of one or more characteristics of the physical environment. For example, an AV park may have virtual trees and virtual buildings, but people with faces photorealistically reproduced from images taken of physical people. As another example, a virtual object may adopt a shape or color of a physical article imaged by one or more imaging sensors. As a further example, a virtual object may adopt shadows consistent with the position of the sun in the physical environment. 
     There are many different types of electronic systems that enable a person to sense and/or interact with various CGR environments. Examples include head mounted systems, projection-based systems, heads-up displays (HUDs), vehicle windshields having integrated display capability, windows having integrated display capability, displays formed as lenses designed to be placed on a person&#39;s eyes (e.g., similar to contact lenses), headphones/earphones, speaker arrays, input systems (e.g., wearable or handheld controllers with or without haptic feedback), smartphones, tablets, and desktop/laptop computers. A head mounted system may have one or more speaker(s) and an integrated opaque display. Alternatively, a head mounted system may be configured to accept an external opaque display (e.g., a smartphone). The head mounted system may incorporate one or more imaging sensors to capture images or video of the physical environment, and/or one or more microphones to capture audio of the physical environment. Rather than an opaque display, a head mounted system may have a transparent or translucent display. The transparent or translucent display may have a medium through which light representative of images is directed to a person&#39;s eyes. The display may utilize digital light projection, OLEDs, LEDs, uLEDs, liquid crystal on silicon, laser scanning light source, or any combination of these technologies. The medium may be an optical waveguide, a hologram medium, an optical combiner, an optical reflector, or any combination thereof. In one embodiment, the transparent or translucent display may be configured to become opaque selectively. Projection-based systems may employ retinal projection technology that projects graphical images onto a person&#39;s retina. Projection systems also may be configured to project virtual objects into the physical environment, for example, as a hologram or on a physical surface. The display systems described herein may be used for these types of systems and for any other desired display arrangements. 
     As described above, one aspect of the present technology is the gathering and use of data available from various sources to improve the delivery of images to users, perform gaze tracking operations, and/or to perform other display-related operations. The present disclosure contemplates that in some instances, this gathered data may include personal information data that uniquely identifies or can be used to contact or locate a specific person. Such personal information data can include demographic data, location-based data, telephone numbers, email addresses, twitter ID&#39;s, home addresses, data or records relating to a user&#39;s health or level of fitness (e.g., vital signs measurements, medication information, exercise information), date of birth, or any other identifying or personal information. 
     The present disclosure recognizes that the use of such personal information data, in the present technology, can be used to the benefit of users. For example, the personal information data can be used to track a user&#39;s gaze to update displayed images and/or to perform other desired display operations. Accordingly, use of such personal information data enables users to view updated display images. Further, other uses for personal information data that benefit the user are also contemplated by the present disclosure. For instance, health and fitness data may be used to provide insights into a user&#39;s general wellness, or may be used as positive feedback to individuals using technology to pursue wellness goals. 
     The present disclosure contemplates that the entities responsible for the collection, analysis, disclosure, transfer, storage, or other use of such personal information data will comply with well-established privacy policies and/or privacy practices. In particular, such entities should implement and consistently use privacy policies and practices that are generally recognized as meeting or exceeding industry or governmental requirements for maintaining personal information data private and secure. Such policies should be easily accessible by users, and should be updated as the collection and/or use of data changes. Personal information from users should be collected for legitimate and reasonable uses of the entity and not shared or sold outside of those legitimate uses. Further, such collection/sharing should occur after receiving the informed consent of the users. Additionally, such entities should consider taking any needed steps for safeguarding and securing access to such personal information data and ensuring that others with access to the personal information data adhere to their privacy policies and procedures. Further, such entities can subject themselves to evaluation by third parties to certify their adherence to widely accepted privacy policies and practices. In addition, policies and practices should be adapted for the particular types of personal information data being collected and/or accessed and adapted to applicable laws and standards, including jurisdiction-specific considerations. For instance, in the US, collection of or access to certain health data may be governed by federal and/or state laws, such as the Health Insurance Portability and Accountability Act (HIPAA); whereas health data in other countries may be subject to other regulations and policies and should be handled accordingly. Hence different privacy practices should be maintained for different personal data types in each country. 
     Despite the foregoing, the present disclosure also contemplates embodiments in which users selectively block the use of, or access to, personal information data. That is, the present disclosure contemplates that hardware and/or software elements can be provided to prevent or block access to such personal information data. For example, in the case of gaze tracking, the present technology can be configured to allow users to select to “opt in” or “opt out” of participation in the collection of personal information data during registration for services or anytime thereafter. In another example, users can select not to perform gaze tracking or other operations that gather personal information data. In yet another example, users can select to limit the length of time gaze tracking is performed. In addition to providing “opt in” and “opt out” options, the present disclosure contemplates providing notifications relating to the access or use of personal information. For instance, a user may be notified upon downloading an app that their personal information data will be accessed and then reminded again just before personal information data is accessed by the app. 
     Moreover, it is the intent of the present disclosure that personal information data should be managed and handled in a way to minimize risks of unintentional or unauthorized access or use. Risk can be minimized by limiting the collection of data and deleting data once it is no longer needed. In addition, and when applicable, including in certain health related applications, data de-identification can be used to protect a user&#39;s privacy. De-identification may be facilitated, when appropriate, by removing specific identifiers (e.g., date of birth, etc.), controlling the amount or specificity of data stored (e.g., collecting location data a city level rather than at an address level), controlling how data is stored (e.g., aggregating data across users), and/or other methods. 
     Therefore, although the present disclosure broadly covers use of personal information data to implement one or more various disclosed embodiments, the present disclosure also contemplates that the various embodiments can also be implemented without the need for accessing such personal information data. That is, the various embodiments of the present technology are not rendered inoperable due to the lack of all or a portion of such personal information data. For example, display images based on non-personal information data or a bare minimum amount of personal information, such as the content being requested by the device associated with a user, other non-personal information available to the display system, or publicly available information. 
     The foregoing is merely illustrative and various modifications can be made to the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20190820
Publication Date: 20231031
Grant Date: 20231031
Priority Date: 20180914
Inventors: PENG, GUOLIN
HANSOTTE, Eric J.
AIETA, Francesco
MYHRE, GRAHAM B.
CHOI, Hyungryul
ZHU, Nan
GELSINGER-AUSTIN, PAUL J.
OH, SE BAEK
DELAPP, SCOTT M.
STEELE, BRADLEY C.
Assignee: APPLE INC
CPC Classifications: [{"code": "G02B27/0172", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B27/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B2027/0174", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B27/0101", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B27/0172", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B27/0172", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B27/0172", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B2027/0174", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B27/1086", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/142", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/34", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B27/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B2027/0174", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 69773975