PATENT DOCUMENT

Publication Number: US-11860394-B1
Application Number: US-202016935021-A
Country: US
Kind Code: B1

Title: Electronic devices with reduced stray light and ambient light reflections

Abstract:
An electronic device may have a display overlapped by an image transport layer such as a coherent fiber bundle or layer of Anderson localization material. The image transport layer may have an input surface that receives an image from the display and a corresponding output surface to which the image is transported. The input surface and output surface may have different shapes. During fabrication of the image transport layer, molding techniques, grinding and polishing techniques, and other processes may be used to deform the image transport layer and the shape of the output surface. To help reduce ambient light reflections and stray light, light-absorbing structures may be incorporated into the image transport layer and other structures overlapping the display.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a display configured to produce an image; and 
 an image transport layer that overlaps the display, wherein the image transport layer is configured to receive the image at an input surface and to transport the received image to an output surface, wherein the image transport layer includes first areas of a first refractive index and second areas of a second refractive index that is lower than the first refractive index, wherein the image transport layer comprises light-absorbing filaments in the second areas, wherein the image transport layer comprises Anderson localization material, wherein the first areas correspond to first filaments of the first refractive index, wherein the second areas correspond to second filaments of the second refractive index, and wherein the light-absorbing filaments are embedded within the second filaments. 
 
     
     
       2. The electronic device defined in  claim 1  wherein the light-absorbing filaments have a third refractive index that is no greater than the second refractive index. 
     
     
       3. An electronic device, comprising:
 a display configured to produce an image; and 
 an image transport layer that overlaps the display, wherein the image transport layer is configured to receive the image at an input surface and to transport the received image to an output surface, wherein the image transport layer includes first areas of a first refractive index and second areas of a second refractive index that is lower than the first refractive index, wherein the image transport layer comprises light-absorbing filaments in the second areas, wherein the image transport layer comprises a coherent fiber bundle having fiber cores, fiber cladding, and binder, and wherein the first areas correspond to the fiber cores and wherein the second areas correspond to the fiber cladding. 
 
     
     
       4. The electronic device defined in  claim 3  wherein the light-absorbing filaments have a third refractive index that is no greater than the second refractive index. 
     
     
       5. An electronic device, comprising:
 a display configured to produce an image; and 
 an image transport layer that overlaps the display, wherein the image transport layer is configured to receive the image at an input surface and to transport the received image to an output surface, wherein the image transport layer includes first areas of a first refractive index and second areas of a second refractive index that is lower than the first refractive index, wherein the image transport layer comprises light-absorbing filaments in the second areas, wherein the image transport layer comprises a coherent fiber bundle having fiber cores, fiber cladding, and binder, and wherein the first areas correspond to the fiber cores and wherein the second areas correspond to the binder. 
 
     
     
       6. The electronic device defined in  claim 5  wherein the light-absorbing filaments have a third refractive index that is no greater than the second refractive index.

Description:
This application claims the benefit of provisional patent application No. 62/905,542, filed Sep. 25, 2019, which is hereby incorporated by reference herein in its entirety. 
    
    
     FIELD 
     This relates generally to electronic devices, and, more particularly, to electronic devices with displays. 
     BACKGROUND 
     Electronic devices may have displays. Displays have arrays of pixels for displaying images for a user. The shape and other characteristics of many displays can pose challenges during integration into an electronic device, particularly in situations where space is limited. 
     SUMMARY 
     An electronic device may have a display that displays an image. The image may be viewed through a display cover layer that overlaps the display. 
     The display cover layer may include an image transport layer such as a coherent fiber bundle or layer of Anderson localization material. The image transport layer may have an input surface that receives an image from the display and a corresponding output surface to which the image is transported. The display cover layer may also include a protective layer such as a layer of glass or other material. The protective layer may protect underlying structures such as polymer fibers or other structures in the image transport layer. 
     Peripheral portions of the display cover layer may have an elevated risk of reflecting ambient light. To help reduce stray light and ambient light reflections, light-absorbing material may be incorporated into the display cover layer. The light-absorbing material may be uniform across the display cover layer or may be concentrated in peripheral portions of the display cover layer (as examples). 
     The light-absorbing material may include dye and/or pigment. In an illustrative arrangement, filaments of light-absorbing material may be embedded within fiber cores, cladding, and/or binder and/or may be embedded within low-refractive-index areas of Anderson localization material. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a side view of an illustrative electronic device with an image transport layer in accordance with an embodiment. 
         FIG.  2    is a cross-sectional view of a portion of an illustrative image transport layer formed using a coherent fiber bundle in accordance with an embodiment. 
         FIG.  3    is a cross-sectional view of a portion of an illustrative image transport layer formed using Anderson localization material in accordance with an embodiment. 
         FIG.  4    is a perspective view of a portion of an image transport layer surface with compound curvature in accordance with an embodiment. 
         FIG.  5    is a top view of an illustrative electronic device in accordance with an embodiment. 
         FIGS.  6 ,  7 ,  8 , and  9    are cross-sectional side views of portions of illustrative display cover layers in accordance with embodiments. 
         FIG.  10    is a graph showing how one or more display cover layer attributes such as light absorption can be adjusted as a function of lateral distance from the center of a display cover layer toward the periphery of the display cover layer in accordance with an embodiment. 
         FIG.  11    is a perspective view of a fiber with illustrative light absorption structures in accordance with an embodiment. 
         FIG.  12    is a cross-sectional view of illustrative fibers in an image transport layer having a light absorption structure located within binder in accordance with an embodiment. 
         FIG.  13    is a cross-sectional view of illustrative Anderson localization material in accordance with an embodiment. 
         FIG.  14    is a cross-sectional side view of an area of lowered refractive index that has been provided with a light absorption structure to absorb light in Anderson localization material such as the Anderson localization material of  FIG.  13    in accordance with an embodiment. 
         FIG.  15    is a cross-sectional view of illustrative Anderson localization material with filaments of different refractive index in accordance with an embodiment. 
         FIG.  16    is a cross-sectional side view of a filament of lowered refractive index that has been provided with a light absorption structure to absorb light in Anderson localization material such as the Anderson localization material of  FIG.  15    in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An electronic device may have a display. The display may have an array of pixels for creating an image. The image may pass through a display cover layer that overlaps the array of pixels. To minimize display borders or to otherwise create a desired appearance for the display, the display cover layer may include an image transport layer. The image transport layer may have an input surface that receives an image from the array of pixels and a corresponding output surface to which the image is transported from the input surface. A user viewing the image transport layer will view the image from the array of pixels as being located on the output surface. 
     In configurations in which the input and output surfaces have different shapes, the image transport layer may be used to warp the image produced by the array of pixels. For example, the shape of the image can transformed and the effective size of the image can be changed as the image passes through the image transport layer. In some configurations, edge portions of the image are stretched outwardly to help minimize display borders. 
     Image transport layers can be formed from coherent fiber bundles (sometimes referred to as fiber optic plates) and/or Anderson localization material. Glass and/or polymer may be used in forming image transport layer structures. To help protect the output surface of an image transport layer, an optional transparent protective layer may be included on the outer surface of the display cover layer. This transparent protective layer may be, for example, a glass plate, or a protective layer formed from other transparent material such as clear polymer or sapphire or other crystalline materials. In some arrangements, image transport layers and/or protective layers can be formed over components other than displays. 
     The process of forming an image transport layer into a desired shape may affect the optical properties of the image transport layer. For example, peripheral edge portions of an image transport layer that are stretched outwardly during molding and other shaping operations may tend to reflect (scatter) light more than an unstretched central portion of an image transport layer. This can lead to an undesirable bright band around the periphery of a display as ambient light reflects off of the puerperal portion of the image transport layer. To reduce ambient light scattering and enhance the ability of a user to view image content on peripheral portions of the display, light-absorbing structures may be incorporated into the display cover layer. These structures may help absorb light and thereby suppress ambient light reflections. Light emitted from the display that scatters and forms stray light may also be absorbed by the light-absorbing structures. 
     A cross-sectional side view of a portion of an illustrative electronic device with a display cover layer that includes an image transport layer is shown in  FIG.  1   . In the example of  FIG.  1   , device  10  is a portable device such as a cellular telephone, wristwatch, or tablet computer. In general, any type of electronic device may have an image transport layer such as a desktop computer, a voice-control speaker, a television or other non-portable display, a head-mounted device, an embedded system such as a system built into a vehicle or home, an electronic device accessory, and/or other electronic equipment. 
     Device  10  includes a housing such as housing  12 . Housing  12  may be formed from polymer, metal, glass, crystalline material such as sapphire, ceramic, fabric, fibers, fiber composite material, natural materials such as wood and cotton, other materials, and/or combinations of such materials. Housing  12  may be configured to form housing walls. The housing walls may enclose one or more interior regions such as interior region  24  and may separate interior region  24  from exterior region  22 . In some configurations, an opening may be formed in housing  12  for a data port, a power port, to accommodate audio components, or to accommodate other devices. Clear housing regions may be used to form optical component windows. Dielectric housing structures may be used to form radio-transparent areas for antennas and wireless power components. 
     Electrical components  18  may be mounted in interior region  24 . Electrical components  18  may include integrated circuits, discrete components, light-emitting components, sensors, and/or other circuits and may, if desired, be interconnected using signal paths in one or more printed circuits such as printed circuit  20 . If desired, one or more portions of the housing walls may be transparent (e.g., so that light associated with an image on a display or other light-emitting or light-detecting component can pass between interior region  24  and exterior region  22 ). 
     Electrical components  18  may include control circuitry. The control circuitry may include storage and processing circuitry for supporting the operation of device  10 . The storage and processing circuitry may include storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other 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 the control circuitry may be used to control the operation of device  10 . For example, the processing circuitry may use sensors and other input-output circuitry to gather input and to provide output and/or to transmit signals to external equipment. The processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio chips, application specific integrated circuits, etc. The control circuitry may include wired and/or wireless communications circuitry (e.g., antennas and associated radio-frequency transceiver circuitry such as cellular telephone communications circuitry, wireless local area network communications circuitry, etc.). The communications circuitry of the control circuitry may allow device  10  to communicate with other electronic devices. For example, the control circuitry (e.g., communications circuitry in the control circuitry) may be used to allow wired and/or wireless control commands and other communications to be conveyed between devices such as cellular telephones, tablet computers, laptop computers, desktop computers, head-mounted devices, handheld controllers, wristwatch devices, other wearable devices, keyboards, computer mice, remote controls, speakers, accessory displays, accessory cameras, and/or other electronic devices. Wireless communications circuitry may, for example, wirelessly transmit control signals and other information to external equipment in response to receiving user input or other input from sensors or other devices in components  18 . 
     Input-output circuitry in components  18  of device  10  may be used to allow data to be supplied to device  10  and to allow data to be provided from device  10  to external devices. The input-output circuitry may include input devices that gather user input and other input and may include output devices that supply visual output, audible output, or other output. 
     Output may be provided using light-emitting diodes (e.g., crystalline semiconductor light-emitting diodes for status indicators and/or displays, organic light-emitting diodes in displays and other components), lasers, and other light-emitting devices, audio output devices (e.g., tone generators and/or speakers), haptic output devices (e.g., vibrators, electromagnetic actuators, piezoelectric actuators, and/or other equipment that supplies a user with haptic output), and other output devices. 
     The input-output circuitry of device  10  (e.g., the input-output circuitry of components  18 ) may include sensors. Sensors for device  10  may include force sensors (e.g., strain gauges, capacitive force sensors, resistive force sensors, etc.), audio sensors such as microphones, touch and/or proximity sensors such as capacitive sensors (e.g., a two-dimensional capacitive touch sensor integrated into a display, a two-dimensional capacitive touch sensor and/or a two-dimensional force sensor overlapping a display, and/or a touch sensor or force sensor that forms a button, trackpad, or other input device not associated with a display), and other sensors. Touch sensors for a display or for other touch components may be based on an array of capacitive touch sensor electrodes, acoustic touch sensor structures, resistive touch components, force-based touch sensor structures, a light-based touch sensor, or other suitable touch sensor arrangements. If desired, a display may have a force sensor for gathering force input (e.g., a two-dimensional force sensor may be used in gathering force input on a display). 
     If desired, the sensors may include optical sensors such as optical sensors that emit and detect light, optical touch sensors, optical proximity sensors, and/or other touch sensors and/or proximity sensors, monochromatic and color ambient light sensors, image sensors, fingerprint sensors, ultrasonic sensors, temperature sensors, sensors for measuring three-dimensional non-contact gestures (“air gestures”), pressure sensors, sensors for detecting position, orientation, and/or motion (e.g., accelerometers, magnetic sensors such as compass sensors, gyroscopes, and/or inertial measurement units that contain some or all of these sensors), health sensors, radio-frequency sensors (e.g., sensors that gather position information, three-dimensional radio-frequency images, and/or other information using radar principals or other radio-frequency sensing), depth sensors (e.g., structured light sensors and/or depth sensors based on stereo imaging devices), optical sensors such as self-mixing sensors and light detection and ranging (lidar) sensors that gather time-of-flight measurements, humidity sensors, moisture sensors, gaze tracking sensors, three-dimensional sensors (e.g., time-of-flight image sensors, pairs of two-dimensional image sensors that gather three-dimensional images using binocular vision, three-dimensional structured light sensors that emit an array of infrared light beams or other structured light using arrays of lasers or other light emitters and associated optical components and that capture images of the spots created as the beams illuminate target objects, and/or other three-dimensional image sensors), facial recognition sensors based on three-dimensional image sensors, and/or other sensors. 
     In some configurations, components  18  may include mechanical devices for gathering input (e.g., buttons, joysticks, scrolling wheels, key pads with movable keys, keyboards with movable keys, and other devices for gathering user input). During operation, device  10  may use sensors and/or other input-output devices in components  18  to gather user input (e.g., buttons may be used to gather button press input, touch and/or force sensors overlapping displays can be used for gathering user touch screen input and/or force input, touch pads and/or force sensors may be used in gathering touch and/or force input, microphones may be used for gathering audio input, etc.). The control circuitry of device  10  can then take action based on this gathered information (e.g., by transmitting the information over a wired or wireless path to external equipment, by supplying a user with output using a haptic output device, visual output device, an audio component, or other input-output device in housing  12 , etc.). 
     If desired, electronic device  10  may include a battery or other energy storage device, connector ports for supporting wired communications with ancillary equipment and for receiving wired power, and other circuitry. In some configurations, device  10  may serve as an accessory and/or may include a wired and/or wireless accessory (e.g., a keyboard, computer mouse, remote control, trackpad, etc.). 
     Device  10  may include one or more displays such as display  14 . The displays may, for example, include an organic light-emitting diode display, a liquid crystal display, a display having an array of pixels formed from respective light-emitting diodes (e.g., a pixel array having pixels with crystalline light-emitting diodes formed from respective light-emitting diode dies such as micro-light-emitting diode dies), and/or other displays. The displays may include rigid display structures and/or may be flexible displays. For example, a light-emitting diode display may have a polymer substrate that is sufficiently flexible to be bent. Display  14  may have a rectangular pixel array or a pixel array of another shape for displaying images for a user and may therefore sometimes be referred to as a pixel array. Display  14  may also sometimes be referred to as a display panel, display layer, or pixel layer. Each pixel array in device  10  may be mounted under a transparent housing structure (sometimes referred to as a transparent display cover layer). 
     In the example of  FIG.  1   , display (pixel array)  14  is mounted under display cover layer  32 . Display cover layer  32  (which may be considered to form a portion of the housing of device  10 ), covers front face F of device  10 . Configurations in which opposing rear face R of device  10  and/or sidewall portions of device  10  have transparent structures covering displays and other optical components may also be used. 
     As shown in  FIG.  1   , display cover layer  32  may include image transport layer  16  and protective layer  30 . Protective layer  30  may be formed from a layer of glass, clear polymer, crystalline material such as sapphire or other crystalline material, and/or other transparent material. The presence of layer  30  may help protect the outer surface of layer  16  from scratches. If desired, layer  30  may be omitted (e.g., in configurations in which a thin-film protective coating is present on the outer surface of layer  16 , in configurations in which layer  16  is formed from hard material such as glass, and/or in other configurations in which layer  16  is resistant to scratching). A layer of adhesive and/or other structures may be formed between protective layer  30  and image transport layer  16  and/or may be included elsewhere in the stack of layers on display  14 . 
     During operation, the pixels of display  14  produce image light that passes through image transport layer  16 . In configurations in which image transport layer  16  is formed from a coherent fiber bundle, image transport layer  16  has optical fibers  16 F. The fibers or other optical structures of image transport layer structures such as image transport layer  16  transport light (e.g., image light and/or other light) from one surface (e.g., an input surface of layer  16  that faces display  14 ) to another (e.g., an output surface of layer  16  that faces viewer  28 , who is viewing device  10  in direction  26 ). As the image presented to the input surface of layer  16  is transported to the output surface of layer  16 , the integrity of the image light is preserved. This allows an image produced by an array of pixels to be transferred from an input surface of a first shape at a first location to an output surface with a different shape (e.g., a shape with a footprint that differs from that of the input surface, a shape with a curved cross-sectional profile, a shape with a region of compound curvature, and/or a shape with other desired features). 
     Image transport layer  16  may therefore move the location of an image and may optionally change the shape of the surface on which the image is presented. In effect, viewer  28  will view the image from display  14  as if the image were generated on the output surface of image transport layer  16 . In arrangements in which the image from display  14  is warped (geometrically distorted) by image transport layer  16 , digital pre-distortion techniques or other compensation techniques may be used to ensure that the final image viewed on the output surface of image transport layer  16  has a desired appearance. For example, the image on display  14  may be prewarped so that this prewarped image is warped by an equal and opposite amount upon passing through layer  16 . In this way, the prewarped image is effectively unwarped by passage through layer  16  will not appear distorted on the output surface. 
     In configurations of the type shown in  FIG.  1   , device  10  may have four peripheral edges and a rectangular footprint when viewed in direction  26  or may have other suitable shapes. To help minimize the size of inactive display borders as a user is viewing front face F of device  10  as shown in  FIG.  1   , the shapes of fibers  16 F along the periphery of layer  16  may be deformed outwardly as shown in  FIG.  1   . These fibers  16 F each have an outwardly bent segment that bends away from surface normal n of the center of layer  30  (e.g., away from an axis parallel to the Z axis of  FIG.  1   ) and each have an inwardly bent segment that bends back towards surface normal n to help direct output light towards viewer  28 . 
     The deformed shapes of fibers  16 F (and/or the corresponding deformations made to optical filaments in Anderson localization material in layer  16 ) may help distribute image light laterally outwards in the X-Y plane so that the effective size of display  14  is enlarged and the image produced by display  14  covers some or all of the sidewalls of housing  12  or other peripheral portions of device  10  when the image on front face F is being viewed by viewer  28 . For example, the bent shapes of fibers  16 F of  FIG.  1    may help shift portion of the displayed image laterally outward in the X-Y plane along the edges and corners of device  10  to block the edges of device  10  from view. In some arrangements, the portions of fibers  16 F at the outermost surface of layer  16  are oriented parallel or nearly parallel with viewing direction  26  and the Z axis of  FIG.  1   , which helps ensure that some or all of the light that has passed through layer  16  will travel in the Z direction and be viewable by viewer  28 . 
       FIG.  2    is a cross-sectional view of a portion of image transport layer  16  in an illustrative configuration in which image transport layer  16  is formed from a coherent fiber bundle. Fibers  16 F for layer  16  may have any suitable configuration. As shown in the example of  FIG.  2   , fibers  16 F may each have a core such as core  16 F- 1 . Cores  16 F- 1  and the other structures of image transport layer (e.g., cladding structures, binder, etc.)  16  may be formed from materials such as polymer, glass, crystalline material such as sapphire, and/or other materials. Some or all of these materials may be transparent. Arrangements in which some of the materials absorb light and/or have non-neutral colors or other light filtering properties may also be used. 
     Fiber cores  16 F- 1  may be formed from transparent material of a first refractive index and may be surrounded by cladding of a second, lower refractive index to promote light guiding in accordance with the principal of total internal reflection. In some arrangements, a single coating layer on cores  16 F- 1  may be used to form the cladding. In other arrangements, two or more coating layers on cores  16 F- 1  may be used to form the cladding. Clad fibers may be held together using binder  16 FB, which serves to fill the interstitial spaces between the clad fibers. In some configurations, stray light absorbing material may be incorporated into layer  16  (e.g., into some of the cores, cladding, and/or binder). The stray light absorbing material may be, for example, polymer, glass, or other material into which light-absorbing material such as dye and/or pigment has been incorporated. 
     In an illustrative configuration, layer  16  may have inner coating layers  16 F- 2  that are formed directly on the outer surfaces of cores  16 F- 1  and outer coating layers  16 F- 3  that are formed directly on the outer surfaces of layers  16 F- 2 . Additional coating layers (e.g., three or more coating layers) or fewer coating layers (e.g., a single coating layer) may be formed on fiber cores  16 F- 1 , if desired. Stray light-absorbing material may be used in layers  16 F- 2  and/or  16 F- 3  or other coating layer(s) on cores  16 F- 1 . In an illustrative arrangement, layers  16 F- 2  and  16 F- 3 , which may sometimes be referred to as forming first and second cladding portions (or first and second claddings) of the claddings for fiber cores  16 F- 1 , may respectively be formed from transparent material and stray light-absorbing material. Other arrangements may be used, if desired (e.g., arrangements in which stray light absorbing material is incorporated into some or all of binder  16 FB, arrangements in which cores  16 F- 1  are coated with inner and outer transparent claddings and an interposed intermediate stray-light-absorbing cladding, arrangements in which cores  16 F- 1  are covered with a single stray-light-absorbing cladding, arrangements in which some or all of fibers  16 F are provided with longitudinally extending filaments  16 F- 4  of stray light absorbing material located, for example, on or in any of the cladding layers, etc.). 
     In configuration in which fibers  16 F have claddings formed from two or more separate cladding layers, the cladding layers may have the same index of refraction or the outermost layers may have lower refractive index values (as examples). Binder  16 FB may have a refractive index equal to the refractive index of the cladding material or lower than the refractive index of the cladding material to promote total internal reflection (as examples). For example, each fiber core  16 F- 1  may have a first index of refraction and the cladding material surrounding that core may have a second index of refraction that is lower than the first index of refraction by an index difference of at least 0.05, at least 0.1, at least 0.15, at least 10%, at least 20%, less than 50%, less than 30%, or other suitable amount. The binder refractive index may be the same as that of some or all of the cladding material or may be lower than the lowest refractive index of the cladding by an index difference of at least 0.05, at least 0.1, at least 0.15, at least 10%, at least 20%, less than 50%, less than 30%, or other suitable amount. 
     The diameters of cores  16 F- 1  may be, for example, at least 5 microns, at least 7 microns, at least 8 microns, at least 9 microns, less than 40 microns, less than 17 microns, less than 14 microns, less than 11 microns, or other suitable diameter. Fibers 16F (including cores and claddings) may have diameters of at least 6 microns, at least 7 microns, at least 8 microns, at least 9 microns, less than 50 microns, less than 17 microns, less than 14 microns, less than 11 microns, or other suitable diameter. 
     Fibers  16 F may generally extend parallel to each other in image transport layer  16  (e.g., the fibers may run next to each other along the direction of light propagation through the fiber bundle). This allows image light or other light that is presented at the input surface to layer  16  to be conveyed to the output surface of layer  16 . 
     If desired, image transport layer  16  may be formed from Anderson localization material in addition to or instead of fibers  16 F. Anderson localization material is characterized by transversely random refractive index features (higher index regions and lower index regions) of about two wavelengths in lateral size that are configured to exhibit two-dimensional transverse Anderson localization of light (e.g., the light output from the display of device  10 ). These refractive index variations are longitudinally invariant (e.g., along the direction of light propagation, perpendicular to the surface normal of a layer of Anderson localization material). 
       FIG.  3    is a cross-sectional view of a portion of an image transport layer formed from Anderson localization material. In the example of  FIG.  3   , image transport layer  16  includes a random (pseudorandom) set of elongated optical structures of different refractive index values. These structures may, for example, be optical filaments that run into and out of the page of  FIG.  3    and that have different refractive index values such as first filaments  16 H with higher refractive index values and second filaments  16 L with lower refractive index values. The refractive indices of filaments  16 L and  16 H may differ by any suitable amount (e.g., by at least 0.05, at least 0.1, at least 0.2, at least 0.3, by less than 0.8, etc.). The filaments may be distributed laterally (in dimensions X and Y) with a random pattern and may have any suitable cross-sectional shape (circular, rectangular, etc.). Anderson localization material preforms can be formed by drawing and assembling individual filaments of different refractive index values into bundles and/or can be formed by extruding lengths of material that include laterally interspersed areas of different respective refractive index values. Preforms can then be formed into layer  16  using one or more fusing and drawing operations. Other fabrication techniques may be used, if desired. To absorb stray light within an image transport layer formed from Anderson localization material, the Anderson localization material may include light absorbing material (e.g., light-absorbing filaments interspersed with transparent filaments or other light-absorbing structures). 
     Image transport layers can be used to transport an image from a first surface (e.g., the surface of a pixel array) to a second surface (e.g., a surface in device  10  with compound curvature or other curved and/or planar surface shape) while preserving the integrity of the image. A perspective view of an illustrative corner portion of image transport layer  16  is shown in  FIG.  4   . In the example of  FIG.  4   , device  10  has edge portions  40  and  42  with surfaces that curve about axes  44  and  46 , respectively. These portions of layer  16  may extend parallel to the straight sides of device  10  (as an example) and are characterized by curved surfaces that can be flattened into a plane without distortion (sometimes referred to as developable surfaces). At the corner of image transport layer  16  of  FIG.  4   , image transport layer  16  has curved surface portions CP with compound curvature (e.g., a surface that can only be flattened into a plane with distortion, sometimes referred to as a surface with Gaussian curvature). In a rectangular layout with curved corners, image transport layer  16  may have four corners with compound curvature. Image transport layers of other shapes (e.g., circular outlines, etc.) may also have surfaces with compound curvature (e.g., dome-shaped surfaces). When overlapped by protective layer  30 , the overlapping portions of protective layer  30  may have corresponding surfaces with compound curvature. When selecting the size and shape of the output surface of layer  16  and therefore the size and shape of the image presented on the output surface, the use of an image transport layer material with compound curvature can provide design flexibility. 
     In some arrangements, device  10  may include support structures such as wearable support structures. This allows device  10  to be worn on a body part of a user (e.g., the user&#39;s wrist, arm, head, leg, or other portion of the user&#39;s body). As an example, device  10  may include a wearable band, such as band  50  of  FIG.  5   . Band  50 , which may sometimes be referred to as a wristband, wrist strap, or wristwatch band, may be formed from polymer, metal, fabric, leather or other natural materials, and/or other material, may have links, may stretch, may be attached to housing  12  in a fixed arrangement, may be detachably coupled to housing  12 , may have a single segment or multiple segments joined by a clasp, and/or may have other features that facilitate the wearing of device  10  on a user&#39;s wrist. 
     Image transport layers may be formed by molding or otherwise processing blocks of image transport layer material (e.g., blocks of coherent fiber bundle material or Anderson localization material). These processing operations may include, for example, molding a block of image transport layer material in a heated mold to help create a lateral indentation in a block of image transport layer material (e.g., to create a peripheral undercut region with outwardly bent and stretched fibers as shown on the left side of layer  16  of the example of  FIG.  1   ). The molding operation may help define optical paths through the image transport layer material that can hide inactive border structures (as an example). Additional processing (sawing, grinding, polishing, etc.) may be used to form a final desired shape for the transport layer (e.g., a shape having a peripheral portion with a downwardly curved cross-sectional profile of the type shown in  FIG.  1    other suitable shape). 
     When image transport layer material is processed by molding (e.g., thermal stretching and expansion) and by grinding and other operations, the image transport layer material may exhibit enhanced light scattering. Increases in light scattering may occur due to small optical defects that arise during processing (e.g., stress-induced defects) and from the deformed nature of the bent optical paths in portions of the processed image transport layer. In arrangements of the type shown in  FIG.  1   , light scattering tends to be localized in the processed peripheral portions of image transport layer  16  (e.g., portions of layer  16  where fibers  16 F are most bent and/or the output surface of layer  16  is curved). When exposed to ambient light during normal use, enhanced light scattering at the periphery of layer  16  creates a risk that the peripheral portion of the image on display  14  will be obscured by enhanced ambient light reflection (enhanced ambient light scattering from the image transport layer). 
     To reduce ambient light reflection and stray display light (image light that has scattered due to defects, etc.), the structures overlapping display  14  (e.g., portions of display cover layer  32 ) may be configured absorb light. For example, some of layer  32  may include light-absorbing structures that suppress outward light scattering resulting from ambient light illumination.  FIGS.  6 ,  7 ,  8 , and  9    are cross-sectional side views of portions of display cover layer  32  in illustrative configurations in which layer  32  includes structures to help suppress ambient light reflection. 
     In the illustrative arrangement of  FIG.  6   , display cover layer  32  includes image transport layer  16  and protective layer  30 . A layer of adhesive such as optically clear adhesive  60  may be formed between protective layer  30  and image transport layer  16  to couple layers  30  and  16  together. To help suppress reflection of incoming ambient light, layer  30  may be provided with light-scattering material. Layer  30  may, for example, include light-absorbing material such as a dark dye, dark pigment, and/or other opaque colorant (light-absorbing colorant) that reduces the light transmission of layer  30  to a value of less than 95%, less than 90%, less than 85%, less than 80%, less than 70%, at least 50%, or other suitable amount (e.g., the light absorption of layer  30  may be 5-50%, 10-40%, 5-30%, or other suitable amount). 
     Incoming ambient light such as illustrative ambient light ray  52  passes through layer  30  a first time (e.g., in a downward direction when entering layer  30  from exterior region  22 ) and, after reflecting from light-scattering structures in layer  16 , passes through layer  30  a second time (e.g., in an upward direction), before being viewed by viewer  28  ( FIG.  1   ). Image light from display  14 , however, passes through layer  30  only once (when traveling outwardly to exterior  22  from display  14 ). As a result, the light absorbing structures of layer  30  (and/or other light absorbing structures incorporated into layer  32 ) tend to absorb reflected ambient light more strongly than emitted display light. The incorporation of light-absorbing material into layer  30  therefore absorbs more reflected ambient light than image light and helps prevent the image light from being obscured by undesired ambient light reflections. 
     As shown in  FIG.  7   , a light absorbing layer such as light-absorbing layer  62  may be interposed between protective layer  30  and image transport layer  16 . Adhesive layer  64  may couple protective layer  30  to layer  62  and adhesive layer  66  may couple image transport layer  16  to layer  62 . Layer  62  may be a polymer film or a structure formed from other materials (e.g., glass, etc.). With an illustrative configuration, layer  62  includes light-absorbing material such as dark dye, dark pigment, and/or other opaque colorant that reduces the light transmission of layer  62  to a value of less than 95%, less than 90%, less than 85%, less than 80%, less than 70%, at least 50%, or other suitable amount (e.g., the light absorption of layer  30  may be 5-50%, 10-40%, 5-30%, or other suitable amount). 
     Another illustrative configuration for reducing ambient light reflections is shown in  FIG.  8   . In the example of  FIG.  8   , layer  68  between protective layer  30  and image transport layer  16  has light absorbing material. Layer  68  may be a polymer layer (e.g., a layer of cured liquid adhesive or other adhesive) that attaches layer  30  to layer  16 . Layer  68  may include light-absorbing material such as dark dye, dark pigment, and/or other opaque colorant that reduces the light transmission of layer  60  to a value of less than 95%, less than 90%, less than 85%, less than 80%, less than 70%, at least 50%, or other suitable amount (e.g., the light absorption of layer  30  may be 5-50%, 10-40%, 5-30%, or other suitable amount). 
       FIG.  9    shows how light-absorbing structures  70  may be incorporated into layer  16  to help reduce ambient light reflections. In the example of  FIG.  9   , protective layer  30  has been attached to the output surface of image transport layer  16  using adhesive layer  72 . Light-absorbing material  70  (e.g., polymer, glass, or other material containing dark dye, dark pigment, and/or other opaque colorant) may be incorporated into layer  16  to help absorb ambient light. Material  70  may be incorporated into fiber cores, into fiber cladding, and/or into fiber binder in a coherent fiber bundle or may be incorporated into Anderson localization material. As described in connection with  FIG.  2   , light-absorbing material may be incorporated into fiber cladding (e.g., cladding  16 F- 2  or other cladding) to help absorb scattered light while allowing cores  16 F- 1  to transmit image light and/or may be provided as light-absorbing filaments  16 F- 4  (as examples). In general, light-absorbing material in layer  16  may be incorporated into any one or more of the structures of layer  16  and may, as an example, reduce the light transmission of layer  16  to a value of less than 95%, less than 90%, less than 85%, less than 80%, less than 70%, at least 50%, or other suitable amount (e.g., the light absorption of layer  16  may be 5-50%, 10-40%, 5-30%, or other suitable amount). Light-absorbing material(s) in layer  16  may be characterized by light absorption per unit length that is at least 2 times, at least 5 times, at least 10 times, or at least 50 times larger than the clear light-transmitting structures that form layer  16 . 
     If desired, layer  32  may incorporate combinations of the structures of  FIGS.  6 ,  7 ,  8   , and/or  9 . For example, layer  32  may include protective cover layer light-absorbing material as described in connection with  FIG.  6   , may include one or more polymer films with light-absorbing material as described in connection with layer  62  of  FIG.  7   , may include one or more light-absorbing adhesive layers (e.g., layers  60 ,  64 ,  66 ,  68 , and/or  72  may include light-absorbing dye, pigment, and/or other opaque colorant as described in connection with layer  68  of  FIG.  8   ), and/or layer  16  may include light-absorbing material as described in connection with  FIG.  9   . Other light-absorbing structures may be included in layer  32  if desired. 
     The risk of ambient light reflection may be greater in peripheral edge portions of layer  32  than in the center of layer  32 . For example, layer  32  may have an undeformed central portion that is relatively free of ambient light scattering. To ensure that excessive amounts of emitted display light are not absorbed by layer  32  in portions of layer  32  with relatively small risks of ambient light reflection, different areas of layer  32  may be provide with different amounts of light-absorbing structures. 
     The amount of ambient light absorption ABS that is provided in layer  32  in an illustrative configuration for layer  16  is plotted in  FIG.  10    as a function of lateral distance across layer  32  (and therefore as a function of lateral distance across layer  16 , display  14 , and device  10 ). As shown by curve  76  in the graph of  FIG.  10   , layer  32  may, for example, be provided with one or more of the light-absorbing structures of  FIGS.  6 ,  7 ,  8   , and/or  9  in an arrangement that leads to a laterally varying amount of ambient light reflection suppression. Curve  76  shows how layer  32  may exhibit increasing amounts of ambient light reflection suppression at increasing lateral distances across layer  32  (e.g., at increasing lateral distances from the center of layer  32  towards the peripheral edge of layer  32 ). As a result, the peripheral portion of layer  32 , which include more light-absorbing structures, will tend to suppress ambient light reflection more than the central portion of layer  32 . If desired, the peripheral portion of layer  32  may suppress ambient light reflection less than the center of layer  32  or, as shown by curve  76 , light absorption and ambient light reflection suppression may be uniform across layer  32  (as examples). 
       FIG.  11    is a perspective view of an illustrative fiber in image transport layer  16 . As shown in  FIG.  11   , light absorbing structures such as longitudinally extending light-absorbing filaments  16 F- 4  (e.g., filaments of polymer or glass that include dye, pigment, and/or other opaque colorant such as black or gray filaments) may be used to absorb light. One or more such light-absorbing filaments may be embedded within cladding  16 FC of fiber  16 F, may be adjacent to cladding  16 FC or, as illustrated by light-absorbing filament  16 F- 5 , may be incorporated within fiber core  16 F- 1 .  FIG.  12    shows how one or more light-absorbing filaments (e.g., illustrative light-absorbing filament  16 F- 6 ) may be formed within binder  16 FB. The intensity of guided light is higher in fiber core  16 F- 1  and is lower in binder  16 FB, so embedding light-absorbing material such as filament  16 F- 6  within binder  16 FB helps preferentially absorb stray light (e.g., so that absorption of display image light being guided between the input and output surfaces of layer  16  may be maintained at acceptable levels). The diameter of the cores of fibers  16 F may have any suitable value (e.g., 5-15 microns, 10 microns, etc.). The cladding of fibers  16 F may be 1 micron in thickness, at least 0.5 microns, less than 2 microns, or other suitable cladding thickness). The diameter of filaments  16 F- 4  and/or  16 F- 5 , and/or  16 F- 6  may be 0.1 microns to 0.5 microns, at least 0.05 microns, less than 1 micron, or other suitable value). The refractive index of filament  16 F- 5  may be matched to or lower than the refractive index of surrounding core material, the refractive index of filaments  16 F- 4  may be matched to or lower than the refractive index of surrounding cladding material (and/or binder), and the refractive index of filaments  16 F- 6  may be matched to (or lower than) the refractive index of binder  16 FB (as examples). 
     If desired, image transport layer  16  may be formed from Anderson localization material. In an illustrative configuration, the Anderson localization material for layer  16  may have a cross-sectional structure of the type shown in  FIG.  13   . As shown in  FIG.  13   , layer  16  may, as an example, have areas of with a first refractive index (H) interspersed randomly with areas with a second refractive index (L) that is lower than the first refractive index. These areas may be associated, respectively, with filaments of the first and second refractive index values. The difference in refractive index between the first and second areas may be at least 0.02, at least 0.5, at least 0.1, at least 0.2, at least 0.3, at least 0.4, or other suitable value. The filaments may have lateral dimensions of about two wavelengths in size or other suitable size. In the arrangement of  FIG.  13   , the H and L filaments have been formed using an extrusion process (followed by one or more drawing operations to thin the filaments and one or more fusing operations to build up the lateral size of layer  16 ). The cross-sectional shape of the filaments of the Anderson localization material may be rectangular (e.g., square) or may have other suitable shapes. 
     During the process of guiding light between the input and output surface of layer  16 , the guided light tends to be concentrated within the filaments of higher refractive index (e.g., the H filaments of  FIG.  13   ). To help preferentially absorb stray light, the light-absorbing structures added to layer  16  may, if desired, be formed as elongated filaments embedded within the lower-refractive index regions of a layer of Anderson localization material. As shown in  FIG.  14   , for example, light-absorbing filament LA (sometimes referred to as a subfilament) or may be formed within an L filament (filament of the second refractive index) in the Anderson localization material of layer  16  and may be completely surrounded by material of the second refractive index. Some or all of the L filaments in layer  16  of  FIG.  13    may include light-absorbing filaments such as filament LA of  FIG.  14   . For example, in areas in which it is desired to have a higher amount of light absorption, there may be a larger density of filaments LA. The refractive index of filament LA may be matched to or lower than the refractive index of surrounding filament L. 
     In the example of  FIG.  15   , layer  16  has been formed from Anderson localization material with interspersed filaments (e.g., filaments of circular cross-sectional shape or other suitable shapes). Layer  16  of  FIG.  15    may, as an example, be formed by joining a bundle of filaments (followed by one or more optional drawing operations to reduce the lateral dimensions of the filaments and one or more optional fusing operations to build up the lateral size of the image transport layer). The H filaments may have a first refractive index and the L filaments may have a second refractive index that is less than the first refractive index. In layer  16 , the L and H filaments may have diameters of about two wavelengths or other suitable diameters. As shown in  FIG.  16   , some or all of the L filaments may include light-absorbing filaments (sometimes referred to as subfilaments) such as subfilament  80 . Filaments  80  may be embedded within and completely surrounded by low-index material (e.g., material of the second refractive index). The refractive index of each filament  80  may be matched to (the same as) or lower than the refractive index of surrounding filament L. 
     Light-absorbing filaments in Anderson localization material such as filaments LA of  FIG.  14    and filament  80  of  FIG.  16    that are surrounded by the material of the second refractive index may occupy 5-50%, 5-25%, less than 25%, or other suitable fraction of the total area within of the surrounding filament boundary (as an example). For example, if filament L of  FIG.  16    has a total filament area of A (e.g., without filament  80  being present), then filament  80  may have an area of 5-50% of A, less than 40% of A, less than 30% of A, or less than 25% of A. The diameter of filaments LA and  80  may be, as an example, 0.1 microns to 0.5 microns, at least 0.05 microns, less than 1 micron, less than 2 microns, or other suitable size. 
     The incorporation of light-absorbing filaments into the filaments of lower refractive index in Anderson localization material may help absorb stray light and, as described in connection with  FIG.  9    may help reduce ambient light reflections. 
     Device  10  may be operated in a system that uses personally identifiable information. It is well understood that the use of personally identifiable information should follow privacy policies and practices that are generally recognized as meeting or exceeding industry or governmental requirements for maintaining the privacy of users. In particular, personally identifiable information data should be managed and handled so as to minimize risks of unintentional or unauthorized access or use, and the nature of authorized use should be clearly indicated to users. 
     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: 20200721
Publication Date: 20240102
Grant Date: 20240102
Priority Date: 20190925
Inventors: QIAO, YI
GUILLOU, Jean-Pierre S.
BROWN, MICHAEL J.
KELLEY, PAUL C.
KAKUDA, TYLER R.
WANG, YING-CHIH
KARBASI, SALMAN
Assignee: APPLE INC
CPC Classifications: [{"code": "G02B6/0008", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B1/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/003", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/4202", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/0008", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B1/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/003", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/4202", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B1/14", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B5/003", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/08", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 89434352