PATENT DOCUMENT

Publication Number: US-11442271-B2
Application Number: US-201816609066-A
Country: US
Kind Code: B2

Title: Display illumination systems

Abstract:
An electronic device may have a reflective display with a pixel array that generates images. The reflective display may be illuminated by an illumination system. Light from the illumination system may be reflected by the pixel array as image light. The image light may be provided to a viewer using a waveguide with diffractive input and output couplers. The illumination system may have a waveguide. The illumination system may also have a light source such as one or more light-emitting diodes. Light from the light source may be coupled into the waveguide of the illumination system by a diffractive coupler such as volume hologram that serves as an input coupler. Light from the light source may be routed to the display to illuminate the display using the waveguide in the illumination system and a diffractive coupler such as a volume hologram that serves as an output coupler.

Claims:
What is claimed is: 
     
       1. A device with an illumination system, comprising:
 a pixel array; 
 a light source; 
 a waveguide; 
 a diffractive input coupler that couples light from the light source into the waveguide; and 
 a diffractive output coupler that couples light from the waveguide out of the waveguide and onto the pixel array to illuminate the pixel array and reflect image light from the pixel array, wherein the pixel array is tilted with respect to the diffractive output coupler. 
 
     
     
       2. The device defined in  claim 1  further comprising:
 an optical system having an input portion and an output portion, wherein the optical system is configured to receive the image light from the pixel array with the input portion. 
 
     
     
       3. The device defined in  claim 2  wherein the optical system includes an optical system waveguide that forms at least part of the input portion and at least part of the output portion and that receives the image light using the input portion. 
     
     
       4. The device defined in  claim 3  wherein the output portion includes a diffractive optical system output coupler that is configured to couple the image light out of the optical system waveguide. 
     
     
       5. The device defined in  claim 4  wherein the diffractive output coupler is recorded at an offset angle and is configured to direct light out of the waveguide at a non-zero angle with respect to a surface normal of the waveguide. 
     
     
       6. The device defined in  claim 4  wherein the diffractive output coupler comprises a polarization- sensitive volume hologram. 
     
     
       7. The device defined in  claim 6  wherein the diffractive input coupler comprises a polarization-sensitive volume hologram. 
     
     
       8. The device defined in  claim 7  wherein the diffractive output coupler is a transmission hologram and wherein the diffractive input coupler is a transmission hologram. 
     
     
       9. The device defined in  claim 1  wherein the diffractive output coupler is configured to direct light out of the waveguide at a non-zero angle with respect to a surface normal of the waveguide. 
     
     
       10. The device defined in  claim 1  further comprising a waveplate between the diffractive output coupler and the pixel array, wherein the diffractive output coupler comprises a polarization-sensitive transmission hologram. 
     
     
       11. The device defined in  claim 1  wherein the pixel array comprises a liquid-crystal-on-silicon display. 
     
     
       12. The device defined in  claim 1  wherein the pixel array comprises a microelectromechanical systems display. 
     
     
       13. The device defined in  claim 1  wherein the light source comprises a light source selected from the group consisting of: a light-emitting diode and a laser. 
     
     
       14. The device defined in  claim 13  further comprising:
 a lens interposed between the light source and the waveguide; and 
 a wearable housing that supports the pixel array, the light source, and the waveguide. 
 
     
     
       15. A device with an illumination system, comprising:
 a light source; 
 a waveguide; 
 a first diffractive coupler configured to couple light from the light source into the waveguide; 
 a second diffractive coupler configured to couple light out of the waveguide; and 
 a pixel array configured to reflect the light coupled out of the waveguide as image light that passes through the second diffractive coupler and through the waveguide at a non-zero angle with respect to a surface normal of the waveguide. 
 
     
     
       16. The device defined in  claim 15  further comprising:
 an optical system with an additional waveguide that carries the image light. 
 
     
     
       17. The device defined in  claim 16  wherein the optical system further comprises:
 a third diffractive coupler configured to couple the image light out of the additional waveguide. 
 
     
     
       18. A device with an illumination system, comprising:
 first and second displays; 
 at least first and second light-emitting diodes; 
 first and second waveguides; 
 a first diffractive coupler that couples light from the first light-emitting diode into the first waveguide; 
 a second diffractive coupler that couples the light from the first light-emitting diode out of the first waveguide, wherein the first display reflects the light coupled out of the first waveguide as first image light that passes through the second diffractive coupler at a non-zero angle with respect to a surface normal of the second diffractive coupler and through at least part of the first waveguide; 
 a third diffractive coupler that couples light from the second light-emitting diode into the second waveguide; and 
 a fourth diffractive coupler that couples the light from the second light-emitting diode out of the second waveguide, wherein the second display reflects the light coupled out of the second waveguide as second image light that passes through the fourth diffractive coupler and at least part of the second waveguide. 
 
     
     
       19. A device with an illumination system, comprising:
 a pixel array; 
 a light source; 
 a waveguide; 
 a diffractive input coupler that couples light from the light source into the waveguide; and 
 a diffractive output coupler that couples light from the waveguide out of the waveguide and onto the pixel array to illuminate the pixel array and reflect image light from the pixel array, wherein the diffractive output coupler is configured to direct light out of the waveguide at a non-zero angle with respect to a surface normal of the waveguide.

Description:
This application claims priority to provisional patent application No. 62/519,597, filed on Jun. 14, 2017, 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 reflective display with a pixel array that generates images. The reflective display may be illuminated by an illumination system. During operation, light from the illumination system may be reflected by the pixel array as image light. The image light may be provided to a viewer using an optical system having a waveguide and holographic input and output couplers. 
     The illumination system may have a waveguide. The illumination system may also have a light source such as one or more light-emitting diodes or lasers. Light from the light source may be coupled into the waveguide of the illumination system by a diffractive coupler such as a volume hologram that serves as an input coupler. Light from the light source may be routed to the display using the waveguide in the illumination system and a diffractive coupler such as a volume hologram that serves as an output coupler. Light that has been coupled out of the waveguide in the illumination system by the output coupler reflects from the pixel array as image light and may be provided to the viewer with the optical system. 
    
    
     
       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 in accordance with an embodiment. 
         FIG. 3  is a side view of an illustrative optical system and associated display system for a head-mounted device in accordance with an embodiment. 
         FIG. 4  is a side view of an illustrative display illumination system in accordance with an embodiment. 
         FIG. 5  is a cross-sectional side view of an illustrative display illumination system with a bent waveguide in accordance with an embodiment. 
         FIG. 6  is a side view of a portion of an illustrative display illumination system having a lens to help couple light from a light source into a waveguide in the system in accordance with an embodiment. 
         FIG. 7  is a side view of a portion of an illustrative display illumination system showing how a display may be tilted relative to a waveguide and coupler in the system in accordance with an embodiment. 
         FIG. 8  is a side view of a portion of an illustrative display illumination system with an output coupler formed from a volume hologram written at an offset angle in accordance with an embodiment. 
         FIG. 9  is a side view of an illustrative display illumination system with a wave plate and polarization-sensitive holographic couplers in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Head-mounted devices and other devices may be used for virtual reality and augmented reality systems. These devices may include portable consumer electronics (e.g., portable electronic devices such as cellular telephones, tablet computers, glasses, other wearable equipment), head-up displays in cockpits, vehicles, etc., display-based equipment (projectors, televisions, 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 in a display system to the eyes of a viewer. A waveguide such as a thin planar waveguide formed from a sheet 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. This type of waveguide may also be used to carry light in an illumination system that is configured to provide illumination to a display system. The display system may include reflective displays such as liquid-crystal-on-silicon displays, microelectromechanical systems (MEMs) displays, or other displays. 
     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 head-mounted device may form structures such as Bragg gratings that couple light into the waveguides and that couple light out of the waveguides. 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 layers of polymers 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 adjustable gratings formed from microelectromechanical systems (MEMs) components, 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  50 . Control circuitry  50  may include storage and processing circuitry for controlling the operation of head-mounted display  10 . Circuitry  50  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  50  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  50  and run on processing circuitry in circuitry  50  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  52 . Input-output circuitry  52  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  52  may also be used to gather information on the environment in which head-mounted device  10  is operating. Output components in circuitry  52  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  52  may include one or more displays such as display(s)  26 . Display(s)  26  may be used to display images for a user of head-mounted device  10 . Display(s)  26  have pixel array(s) 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)  26 . 
     Optical components  54  may be used in forming the optical system that presents images to the user. Components  54  may include static components such as waveguides, static optical couplers, and fixed lenses. Components  54  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, microelectromechanical systems (MEMS) tunable 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), 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  54  may be used in proving light to display  26  to illuminate display  26  and in may be used in providing images from display  26  to a user for viewing. In some configurations, one or more of components  54  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  52  may include components such as input-output devices  60  for gathering data and user input and for supplying a user with output. Devices  60  may include sensors  70 , audio components  72 , and other components for gathering input from a user or the environment surrounding device  10  and for providing output to a user. Devices  60  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  52  may face a user&#39;s eyes and may track a user&#39;s gaze. Sensors  70  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  70 , for example, control circuitry  50  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  70 . 
     If desired, sensors  70  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  72  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  60  may include haptic output devices (e.g., vibrating components), light-emitting diodes and other light sources, and other output components. Circuitry  52  may include wired and wireless communications circuitry  74  that allows head-mounted display  10  (e.g., control circuitry  50 ) 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  16  of  FIG. 2 . Support structure  16 , 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  84  may be supported within support structure  16  and may be used to provide images from displays  26  to a user (see, e.g., the eyes of user  90  of  FIG. 2 ). With one illustrative configuration, displays  26  may be located in outer (edge) portions  88  of optical system  84  and may have one or more pixel arrays that produce images. Light associated with the images may be coupled into waveguides in outer portions  88  using input coupler systems. The waveguides may traverse intermediate regions  82 . In central portion(s)  86  of system  84  (at the opposing ends of the waveguides from the input coupler systems and displays  26 ), output coupler systems formed from one or more output couplers may couple the light out of the waveguides. This light may pass through optional lenses  80  in direction  92  for viewing by user  90 . Portion(s)  86  of optical system  84  may be transparent, so that user  90  may view external objects such as object  30  through this region of system  84  while system  84  overlays computer-generated content (image content generated by control circuitry  50 ) with objects such as object  30 . 
       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  26  for producing image light  106 . Image light  106  may be generated by illuminating a reflective display containing an array of pixels. The images presented on the array of pixels may be conveyed through lens  100  to input coupler  102 , which couples image light  106  into waveguide  98  (e.g., a planar waveguide). The image light coupled into waveguide  98  is confined within waveguide  98  in accordance with the principal of total internal reflection and travels towards output coupler  104  as indicated by light  108 . Output coupler  104  couples light  108  (image light) out of waveguide  98  and towards viewer  90  (an eye of a user), as output light (output image light)  110 . Lens  80  may help focus image light for viewer  90 . Input coupler  102  and output coupler  104  may be, for example, structures such as Bragg gratings that couple light into waveguides and that couple light out of the waveguides. Couplers  102  and  104  may be formed from volume holograms or other holographic coupling elements (e.g., thin layers of polymers and/or other optical coupler structures in which holographic patterns are recorded using lasers). Couplers  102  and  104  may have infinite focal lengths (e.g., couplers  102  and  104  may be plane-to-plane couplers) or may have associated finite focal lengths. For example, optical coupler  104  can be powered (e.g., coupler  104  can be configured to form a lens of a desired finite focal length) in which case lens  80  may be omitted or the focal length of lens  80  may be adjusted. 
     Display  26  may have a reflective pixel array (reflective display) such as pixel array  124  of  FIG. 4 . Pixel array  124  may be, for example, a liquid-crystal-on-silicon display, a microelectromechanical systems (MEMs) display, or other display (e.g., a reflective display) that is illuminated by a light source to create image light  106 . During operation, pixels P in pixel array (display)  124  may be adjusted based on image data received from control circuitry  50  to generate images. 
     The size of the illumination system for pixel array  124  can be reduced using waveguide structures and compact optical couplers. In the example of  FIG. 4 , illumination for pixel array  124  is produced by light source  112 . Light source  112  may be formed from one or more light-emitting diodes (e.g., red, green, and blue light-emitting diodes, white light-emitting diodes and/or light-emitting diodes of other colors), lasers of one or more colors, or other suitable light sources. Operation of device  10  using a single wavelength of light may sometimes be described herein as an example. In general, display  124  of device  10  may be illuminated using light-emitting diodes of multiple colors and the optical components of device  10  (e.g., holographic couplers, etc.) may be stacked or otherwise multiplexed (e.g., by writing holograms with multiple different laser beams each of a different wavelength, etc.) to accommodate operation at multiple wavelengths. 
     During operation, light source  112  may produce light  114 . Light  114  may be coupled into waveguide  116  by input coupler  118 . Waveguide  116  (and waveguide  98  of  FIG. 3 ) may be formed from a thin transparent film of polymer, glass, or other suitable clear material. Light  114  that has been coupled into waveguide  116  by input coupler  118  may be confined to waveguide  116  in accordance with the principal of total internal reflection. After this light (light  120  of  FIG. 4 ) travels through waveguide  116  to output coupler  126 , output coupler  126  can couple light  120  out of waveguide  116  towards display pixel array  124  as display illumination  122  (e.g., in a direction that is parallel to surface normal n of waveguide  116 ). After illuminating pixels P, this light is reflected towards input coupler  102  on waveguide  98  ( FIG. 3 ) as image light  106 . 
     Input coupler  118  and output coupler  126  may be, for example, structures such as Bragg gratings and may be formed from volume holograms or other holographic coupling elements (e.g., thin layers of polymers and/or other optical coupler structures in which holographic patterns are recorded using lasers). Couplers  118  and  126  may have infinite focal lengths (e.g., couplers  118  and  126  may be plane-to-plane couplers) or may have associated finite focal lengths. If desired, one or more of couplers  102 ,  104 ,  118 , and  126  may be formed from prisms, lenses, or other non-holographic optical elements. The use of holographic coupler structures in forming some or all of couplers  102 ,  104 ,  118 , and  126  may help reduce size and weight for device  10  and may facilitate the incorporation of optical components  54  within housing  16 . 
     As shown in  FIG. 5 , illumination system waveguide  116  (and, if desired, waveguide  98  of  FIG. 3 ) may be bent to accommodate curves and other features in housing  16  of device  10 . The amount of bending may be limited to preserve the ability of the waveguides to confine light. 
       FIG. 6  is a side view of a portion of an illumination system showing how a lens (with one or more lens elements) such as lens  128  may optionally be interposed between light source  112  waveguide  116  (and therefore interposed between light source  112  and input coupler  118 ). Lens and waveguide  116  and input coupler  118 . 
     Due to reciprocity (symmetry in the diffraction of light passing through holograms), it can be challenging to ensure that light  106  passes through output coupler  126  without being coupled back into waveguide  116  in the direction from which light  120  originated. Various techniques may be used to avoid undesired backwards light coupling in the display illumination system of device  10 . 
     With the illustrative configuration of  FIG. 7 , pixel array  124  (e.g., surface normal n′ of pixel array  124 ) is tilted at a non-zero angle with respect to surface normal n of output coupler  126 . Light  120  strikes output coupler  126  with a range of angles about an angle θB with respect to surface normal n (e.g., a Bragg angle associated with a grating in output coupler  126 ) that is associated with efficiently coupling of light towards display  124  as illumination  122 . Because pixel array  124  is tilted (e.g., because the surface normal n′ of the plane in which pixel array  124  lies is not parallel to surface normal n), image light  106  (e.g., light  122  that has reflected off of pixel array  124 ) will make an angle with surface normal n that is different than angle θB (e.g., an angle at which coupler  126  is not as efficient as redirecting light as when the light matches angle θB). As a result, image light  106  can pass through output coupler  126  with low diffraction (e.g., minimal coupling back into waveguide  116 ), 
     If desired, undesired coupling of image light  106  into waveguide  116  can be reduced by forming the grating of coupler  126  (e.g., writing the volume hologram for coupler  126 ) with a laser that is oriented at an appropriate offset angle. As shown in  FIG. 8 , this produces a hologram that directs light  122  out of waveguide  116  at a non-zero angle to surface normal n and may be used to reduce undesired coupling of image light  106  into waveguide  116  instead of or in addition to tilting pixel array  124 . When coupler  126  is formed from a volume hologram written with appropriately angled laser light, light  120  is coupled out of waveguide  116  at a non-zero angle with respect to surface normal n and will reflect off of pixel array  124  as image light  106  at a corresponding non-zero angle, as shown in  FIG. 8 . As light  106  travels through coupler  126 , the angle that light  106  makes with respect to the grating in coupler  126  will be different than the expected angle θB for efficient coupling, so light  106  will not be coupled into waveguide  116 . 
     As shown in the illustrative configuration of  FIG. 9 , polarization selectively may be used to help reduce back-coupling of light  106  into waveguide  116 . Light  114  is coupled into waveguide  116  as light  120  using input coupler  118 . Input coupler  118  may be a reflection hologram or, if desired, may be a polarization sensitive hologram such as a polarization-sensitive transmission hologram (see, e.g., transmission hologram input coupler  118 ′). After traveling through waveguide  116 , light  120  reaches output coupler  126 . Output coupler  126  may be a reflection hologram or, if desired, may be a polarization sensitive hologram such as a polarization-sensitive transmission hologram (see, e.g., transmission hologram output coupler  126 ′). 
     A wave plate such as wave plate  128  (e.g., a quarter wave plate) may be interposed between output coupler  126  and pixel array  124 . Light  122  may be polarized. Polarized light  122  passes through wave plate  128  and is reflected off of pixel array  124 . After passing through wave plate  128  again in the reverse direction, reflected image light  106  passes through waveguide  116  and output coupler  126  without being coupled back into waveguide  116 . 
     The use of polarized light and polarization-sensitive optical components in the system of  FIG. 8  helps minimize coupling of image light  106  into waveguide  116 . With one illustrative configuration, the input coupler may be polarization sensitive and may, as an example, couple only light  114  that is p polarized into waveguide  116 . Light source  112  may produce light  114  that is unpolarized or that is predominantly p-polarized (in this example). 
     The p polarization of the portion of light  114  that has been coupled into in waveguide  116  (the p polarization of light  120 ) may be maintained as light  120  travels along the length of waveguide  116 . The output coupler may be configured to exhibit a first efficient diffraction angle (Bragg-matching condition angle θBp) for p-polarized light and to exhibit a different second efficient diffraction angle (Bragg-matching condition angle θBs) for s-polarized light. P-polarized light  120  may be characterized by an angle of incidence on the output coupler of angle θBp (a range of light ray angles centered on angle θBp) and may therefore be efficiently directed out of waveguide  116  as light  122  by the output coupler (which is configured to couple out light that reaches the output coupler with angle θBp. After passing through waveplate  128 , reflecting off of pixel array  124 , and passing again through waveplate  128 , the polarization of light  122  will rotate by 90° (in this example). As a result, light  106  will be s polarized and will not be diffracted efficiently by the output coupler. Light  106  will therefore pass through the output coupler as shown in  FIG. 9 . If desired, the input and output couplers may have other types of polarization sensitivities. For example, the input and output couplers may be configured to couple right-hand circularly polarized light (or left-hand circularly polarized light) into and out of waveguide  116 . 
     In accordance with an embodiment, a device with an illumination system is provided that includes a pixel array, a light source, a waveguide, a diffractive input coupler that couples light from the light source into the waveguide, and a diffractive output coupler that couples light from the waveguide out of the waveguide and onto the pixel array to illuminate the pixel array and reflect image light from the pixel array. 
     In accordance with another embodiment, the device includes an optical system having an input portion and an output portion, the optical system is configured to receive the image light from the pixel array with the input portion. 
     In accordance with another embodiment, the optical system includes an optical system waveguide that forms at least part of the input portion and at least part of the output portion and that receives the image light using the input portion. 
     In accordance with another embodiment, the output portion includes a diffractive optical system output coupler that is configured to couple the image light out of the optical system waveguide. 
     In accordance with another embodiment, the pixel array is tilted with respect to the diffractive output coupler. 
     In accordance with another embodiment, the diffractive output coupler is recorded at an offset angle and is configured to direct light out of the waveguide at a non-zero angle with respect to a surface normal of the waveguide. 
     In accordance with another embodiment, the diffractive output coupler includes a polarization-sensitive volume hologram. 
     In accordance with another embodiment, the diffractive input coupler includes a polarization-sensitive volume hologram. 
     In accordance with another embodiment, the diffractive output coupler is a transmission hologram and the diffractive input coupler is a transmission hologram. 
     In accordance with another embodiment, the pixel array is tilted with respect to the diffractive output coupler. 
     In accordance with another embodiment, the diffractive output coupler is configured to direct light out of the waveguide at a non-zero angle with respect to a surface normal of the waveguide. 
     In accordance with another embodiment, the device includes a waveplate between the diffractive output coupler and the pixel array, the diffractive output coupler includes a polarization-sensitive transmission hologram. 
     In accordance with another embodiment, the pixel array includes a liquid-crystal-on-silicon display. 
     In accordance with another embodiment, the pixel array includes a microelectromechanical systems display. 
     In accordance with another embodiment, the light source includes a light source selected from the group consisting of a light-emitting diode and a laser. 
     In accordance with another embodiment, the device includes a lens interposed between the light source and the waveguide, and a wearable housing that supports the pixel array, the light source, and the waveguide. 
     In accordance with an embodiment, a device with an illumination system is provided that includes a pixel array, a light source, a waveguide, a first diffractive coupler configured to couple light from the light source into the waveguide, and a second diffractive coupler configured to couple light out of the waveguide, a pixel array configured to reflect the light coupled out of the waveguide as image light that passes through the second diffractive coupler and the waveguide. 
     In accordance with another embodiment, the device includes an optical system with an additional waveguide that carries the image light. 
     In accordance with another embodiment, the optical system includes a third diffractive coupler configured to couple the image light out of the additional waveguide. 
     In accordance with an embodiment, a device with an illumination system is provided that includes first and second display, at least first and second light-emitting diodes that produce first and second light, first and second waveguide, a first diffractive coupler that couples the light from the first light-emitting diode into the first waveguide, a second diffractive coupler that couples the light from the first light-emitting diode out of the first waveguide, the first display reflects the light coupled out of the first waveguide as first image light that passes through the second diffractive coupler and at least part of the first waveguide, a third diffractive coupler that couples the light from the second light-emitting diode into the second waveguide, and a fourth diffractive coupler that couples the light from the second light-emitting diode out of the second waveguide, the second display reflects the light coupled out of the second waveguide as second image light that passes through the fourth diffractive coupler and at least part of the second waveguide. 
     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: 20180605
Publication Date: 20220913
Grant Date: 20220913
Priority Date: 20170614
Inventors: CHOI, Hyungryul
Hansotte, Eric J
PENG, GUOLIN
GELSINGER-AUSTIN, PAUL J.
OH, SE BAEK
Assignee: APPLE INC
CPC Classifications: [{"code": "G02B2027/0174", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B27/0172", "inventive": true, "first": true, "tree": "[]"}, {"code": "G03H1/0248", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/0026", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/32", "inventive": true, "first": false, "tree": "[]"}, {"code": "G03H2222/31", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/005", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/0101", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B27/0103", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/0172", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B2027/0174", "inventive": false, "first": false, "tree": "[]"}, {"code": "G03H1/0248", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/005", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/32", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/0026", "inventive": true, "first": false, "tree": "[]"}, {"code": "G03H2222/31", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 62751567