PATENT DOCUMENT

Publication Number: US-10930710-B2
Application Number: US-201715802256-A
Country: US
Kind Code: B2

Title: Display with nanostructure angle-of-view adjustment structures

Abstract:
A display may have an array of pixels. Each pixel may have a light-emitting diode such as an organic light-emitting diode or may be formed from other pixel structures such as liquid crystal display pixel structures. The pixels may emit light such as red, green, and blue light. An angle-of-view adjustment layer may overlap the array of pixels. During operation, light from the pixels passes through the angle-of-view adjustment layer to a user. The viewing angle for the user is enhanced as the angular spread of the emitted light from the pixels is enhanced by the angle-of-view adjustment layer. The angle-of-view adjustment layer may be formed from holographic structures recorded by applying laser beams to a photosensitive layer or may be formed from a metasurface that is created by patterning nanostructures on the display using printing, photolithography, or other patterning techniques.

Claims:
What is claimed is: 
     
       1. A display, comprising:
 an array of pixels configured to emit light to display images, wherein the pixels include red pixels, green pixels, and blue pixels; and 
 an angle-of-view adjustment layer having a transparent substrate and a layer of nanostructures forming a metasurface on the substrate, wherein the nanostructures have a dimension that is smaller than a wavelength of light, wherein the angle-of-view adjustment layer overlaps the array of pixels, wherein the nanostructures comprise nanostructures configured to redirect light of a given color that overlap the red pixels, the green pixels, and the blue pixels, and wherein the nanostructures are configured to enhance an angle-of-view associated with the images. 
 
     
     
       2. The display defined in  claim 1  wherein the pixels comprise liquid crystal display pixels. 
     
     
       3. The display defined in  claim 1  wherein the pixels comprise light-emitting diodes. 
     
     
       4. The display defined in  claim 3  wherein the pixels each include a resonant cavity organic light-emitting diode. 
     
     
       5. The display defined in  claim 1  wherein the nanostructures comprise red light nanostructures configured to redirect red light, green light nanostructures configured to redirect green light, and blue light nanostructures configured to redirect blue light. 
     
     
       6. The display defined in  claim 5  wherein the pixels include red pixels, green pixels, and blue pixels and wherein the red light nanostructures overlap the red pixels and do not overlap the blue pixels and green pixels. 
     
     
       7. The display defined in  claim 6  wherein the green light nanostructures overlap the green pixels, do not overlap the red pixels, and do not overlap the blue pixels. 
     
     
       8. The display defined in  claim 5  wherein the red light nanostructures overlap the red pixels, overlap the blue pixels, and overlap the green pixels. 
     
     
       9. The display defined in  claim 8  wherein the green light nanostructures overlap the red pixels, overlap the blue pixels, and overlap the green pixels. 
     
     
       10. The display defined in  claim 5  wherein the blue light nanostructures overlap the red pixels, overlap the blue pixels, and overlap the green pixels. 
     
     
       11. The display defined in  claim 10  wherein the layer of nanostructures comprises metal oxide nanostructures. 
     
     
       12. The display defined in  claim 11  wherein the metal oxide nanostructures comprise titanium oxide nanostructures. 
     
     
       13. The display defined in  claim 10  wherein the layer of nanostructures comprises a cured metal oxide slurry. 
     
     
       14. The display defined in  claim 10  wherein the layer of nanostructures comprises a photolithographically patterned metal oxide layer. 
     
     
       15. A display, comprising:
 an array of pixels configured to emit light to display images; and 
 an overlapping angle-of-view adjustment layer having a layer of nanostructures forming a metasurface, wherein the nanostructures have a dimension that is smaller than a wavelength of light, wherein the nanostructures are configured to enhance an angle-of-view associated with the images, wherein at least three nanostructures overlap a pixel of the array of pixels, and wherein the nanostructures include red light nanostructures configured to redirect red light, green light nanostructures configured to redirect green light, and blue light nanostructures configured to redirect blue light. 
 
     
     
       16. The display defined in  claim 15  wherein the pixels include red pixels, green pixels, and blue pixels and wherein the red light nanostructures overlap the red pixels and do not overlap the blue pixels and green pixels. 
     
     
       17. The display defined in  claim 16  wherein the layer of nanostructures comprises metal oxide columns having lateral dimensions of less than 0.5 microns. 
     
     
       18. A display, comprising:
 an array of pixels configured to emit light to display images, wherein the pixels include red pixels, green pixels, and blue pixels; and 
 an angle-of-view adjustment layer having a layer of nanostructures forming a metasurface, wherein the nanostructures have a dimension that is smaller than a wavelength of light, wherein the nanostructures comprise metal oxide, wherein the nanostructures are configured to enhance an angle-of-view associated with the images and wherein the nanostructures include red light nanostructures configured to redirect red light, green light nanostructures configured to redirect green light, and blue light nanostructures configured to redirect blue light, and wherein the red light nanostructures overlap the red pixels, overlap the blue pixels, and overlap the green pixels. 
 
     
     
       19. The display defined in  claim 18  wherein the green light nanostructures overlap the red pixels, overlap the blue pixels, and overlap the green pixels and wherein the blue light nanostructures overlap the red pixels, overlap the blue pixels, and overlap the green pixels.

Description:
This application claims the benefit of provisional patent application No. 62/501,582, filed on May 4, 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 often include displays. Displays have arrays of pixels for presenting images to a user. If care is not taken, however, a display for an electronic device may not have desired properties. For example, color gamut may be low, images may not be visible over a sufficiently wide angle of view, cost may be too high, or display components may be difficult to manufacture. 
     SUMMARY 
     A display may have an array of pixels. Each pixel may have a light-emitting diode such as an organic light-emitting diode or may be formed from other pixel structures such as liquid crystal display pixel structures. 
     The pixels in the pixel array may emit light such as red, green, and blue light. An angle-of-view adjustment layer may overlap the array of pixels. During operation, light from the pixels passes through the angle-of-view adjustment layer to a user. The viewing angle of the user is enhanced as image light from the pixel array passes through the angle-of-view adjustment layer. This is accomplished by increasing the angular spread of the emitted light from the pixels as the emitted light from the pixels passes through the angle-of-view adjustment layer. 
     The angle-of-view adjustment layer may be formed from holographic structures. The holographic structures may be created using photosensitive materials. For example, an angle-of-view adjustment layer may be formed from holographic structures recorded by applying laser beams to a photosensitive layer or a stack of photosensitive layers. 
     If desired, an angle-of-view adjustment layer may be formed from a metasurface that is created by patterning nanostructures on the display. The nanostructures can be formed using printing, photolithography, or other patterning techniques. Metal oxides such as titanium oxide and other materials may be used in forming the nanostructures. 
     Further features will be more apparent from the accompanying drawings and the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an illustrative electronic device having a display in accordance with an embodiment. 
         FIG. 2  is side view of an illustrative display in accordance with an embodiment. 
         FIG. 3  is a cross-sectional side view of a portion of an illustrative organic light-emitting diode display in accordance with an embodiment. 
         FIG. 4  is a cross-sectional side view of a display such as a liquid crystal display in accordance with an embodiment. 
         FIG. 5  is a side view of a holographic layer in accordance with an embodiment. 
         FIGS. 6 and 7  are graphs showing how a holographic layer may be used in adjusting the angle of view of emitted light from a pixel array in a display in accordance with an embodiment. 
         FIGS. 8 and 9  are cross-sectional side views of illustrative displays in accordance with embodiments. 
         FIG. 10  is a cross-sectional side view of a display with suppressed ambient light reflections in accordance with an embodiment. 
         FIG. 11  is a cross-sectional side view of an illustrative display with a holographic layer being used to redirect light associated with a light-based component in accordance with an embodiment. 
         FIG. 12  is a cross-sectional side view of an illustrative metasurface formed from a layer of nanostructures such as nanopillars of transparent material in accordance with an embodiment. 
         FIG. 13  is a top view of an illustrative metasurface in accordance with an embodiment, 
         FIG. 14  is a side view of an illustrative display with a metasurface having areas with different light redirecting properties such as color-dependent light redirecting properties aligned with respective pixels in accordance with an embodiment. 
         FIG. 15  is a side view of an illustrative display with interleaved nanopillars for different wavelengths so that a uniform metasurface can overlap a pixel array without need to align the particular portions of the metasurface with particular pixels in accordance with an embodiment. 
         FIG. 16  is a cross-sectional side view of an illustrative display in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An illustrative electronic device of the type that may be provided with a display is shown in  FIG. 1 . As shown in  FIG. 1 , electronic device  10  may have control circuitry  16 . Control circuitry  16  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 control circuitry  16  may be used to control the operation of device  10 . 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. 
     Input-output circuitry in device  10  such as input-output devices  12  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. Input-output devices  12  may include buttons, joysticks, scrolling wheels, touch pads, key pads, keyboards, microphones, speakers, tone generators, vibrators, cameras, sensors, light-emitting diodes and other status indicators, data ports, and other electrical components. A user can control the operation of device  10  by supplying commands through input-output devices  12  and may receive status information and other output from device  10  using the output resources of input-output devices  12 . Input-output devices  12  may also be used in gathering information about the environment surrounding device  10 . For example, sensors in devices  12  may make ambient light measurements, may make optical proximity measurements to determine whether an external object is in proximity to device  10 , may make optical fingerprint measurements, may gather images (e.g., for facial recognition, iris scanning, or other biometric authentication), and/or may make other sensor measurements. 
     Input-output devices  12  may include one or more displays such as display  14 . Display  14  may be a touch screen display that includes a touch sensor for gathering touch input from a user or display  14  may be insensitive to touch. A touch sensor for display  14  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. 
     Control circuitry  16  may be used to run software on device  10  such as operating system code and applications. During operation of device  10 , the software running on control circuitry  16  may display images on display  14  using an array of pixels in display  14 . 
     Device  10  may be a tablet computer, laptop computer, a desktop computer, a display, a cellular telephone, a media player, a wristwatch device or other wearable electronic equipment, or other suitable electronic device. 
     Display  14  may be an organic light-emitting diode display, may be a display based on an array of crystalline light-emitting diode dies (sometimes referred to as micro-LEDs), may be a liquid crystal display, or may be a display based on other types of display technology. 
     Display  14  may have a rectangular shape (i.e., display  14  may have a rectangular footprint and a rectangular peripheral edge that runs around the rectangular footprint) or may have other suitable shapes. Display  14  may be planar or may have a curved profile. 
     A side view of display  14  is shown in  FIG. 2 . As shown in  FIG. 2 , display  14  may have a pixel array such as pixel array  20 . Pixel array  20  may include rows and columns of pixels  22 . Pixel array  20  may emit image light for viewing by viewer  26  in direction  28 . Rays of emitted image light such as illustrative ray  30  of  FIG. 2  may be characterized by an angle θ with respect to surface normal n of display  14 . The range of angles over which light rays  30  are emitted by pixels  22  affects the angle of view (A) of display  14 . If the angle of view is too narrow, off-angle viewing performance will not be satisfactory. 
     Due to the construction of pixels  22 , light from pixels  22  may initially have a narrow angular spread. To help spread emitted light over a desired range of angles and thereby achieve a desired angle-of-view A for display  14 , display  14  may include angle-of-view adjustment layer  24 . Layer  24  may be formed from a hologram, a metasurface formed from patterned nanostructures, or other suitable light-spreading layer. 
     Display  14  may be formed from organic light-emitting diodes, packaged light-emitting diodes, micro-light-emitting diodes, liquid crystal display structures, microdisplays, or other suitable display structures.  FIG. 3  is a cross-sectional side view of an illustrative pixel  22  in a light-emitting diode display such as an organic light-emitting diode display. As shown in  FIG. 3 , pixel  22  may be formed on a substrate such as substrate  34  (e.g., glass, ceramic, plastic, etc.). Thin-film circuitry such as thin-film transistor circuitry  36  may be formed on substrate  34 . Circuitry  36  may include transistors such as thin-film transistor  38  for forming pixel circuits for pixels such a pixel  22 . Each pixel circuit may be provided with a respective data value and may supply a respective light-emitting diode such as light-emitting diode  47  with a corresponding drive current (e.g., transistor  38  may be coupled to diode  47  to provide current to diode  47 ). This causes organic light-emitting diode  47  to emit light of an intensity that is proportional to the drive current. 
     Diode  47  may have electrodes such as anode  44  and cathode  48 . Organic layers  46  (e.g., hole and electron transport and injection layers, a layer of organic emissive material, etc.) may be interposed between electrodes  44  and  48 . Electrode  44  may be formed from metal (e.g., a layer of Ag, Al, or other suitable metals), a metal layer formed from alloys of suitable metals, conductive metal oxides (such as indium tin oxide), or combinations of these materials. Electrode  48  may be formed from a semitransparent metal layer (e.g., Al, Mg, or other suitable metal), or suitable metal oxides, or combinations of these materials. With this type of arrangement, organic light-emitting diode  47  may be a resonant cavity organic light-emitting diode. The resonant cavity may be strong, moderate, or weak, depending on the desired spectral and angular output of the device. 
     Resonant cavity organic light-emitting diodes may exhibit relatively narrow linewidths (e.g., spectral widths of 10-30 nm full-width-half-maximum or other suitable bandwidths) and relatively high efficiencies. Resonant cavity organic light-emitting diodes may also exhibit relatively directional light output characteristics. For this reason, the native light output from diode  47  may have an angular spread that is narrower than desired for display  14 . Angle-of-view adjustment layer  24  ( FIG. 2 ) may be used to widen the angular range of the light output from pixels such as the resonant organic light-emitting diode pixel of  FIG. 3 , thereby providing display  14  with a desired angle of view while retaining desirable characteristics for diodes  47  such as the ability to produce pure colors and high efficiency. If desired, light-emitting diodes for display  14  may be micro-LEDs formed from individual crystalline semiconductor dies. The arrangement of  FIG. 3  in which diode  47  is an organic light-emitting diode is merely illustrative. 
       FIG. 4  shows how display  14  may be a liquid crystal display. As shown in  FIG. 4 , backlight unit  50  may produce backlight illumination  52 . Backlight illumination  52  may, as an example, be collimated light with a relatively low angular spread. Liquid crystal display  14  may have a pixel array such as pixel array  20 . Pixel array  20  may include pixels  22 LC each of which is controlled by a corresponding pixel circuit (e.g., a thin-film transistor pixel circuit on a thin-film transistor layer having thin-film transistor circuitry on a transparent substrate). The pixel circuit applies an adjustable electric field to a pixel-sized portion of a liquid crystal layer. An array of color filters  22 CF and polarizer structures upper and lower polarizers) may be incorporated into liquid crystal display  14 . 
     In configurations in which backlight unit  50  produces backlight illumination  52  with a narrow angle of view, display switching speed and other display operating characteristics can be optimized. This may, however, result in emitted light that has a relatively narrow angular spread. To ensure that the angle-of-view of display  14  is satisfactory, angle-of-view adjustment layer  24  may overlap pixel array  20 . 
     With one illustrative configuration, angle-of-view adjustment layer  24  may be formed from a holographic layer. The holographic layer may, for example, be a volume hologram (e.g., Bragg gratings) formed by exposing photosensitive material to interfering reference and signal beams of laser light. The photosensitive material may be a photorefractive film that exhibits a change in refractive index in proportional to the intensity of the laser light to which it is exposed. The film may be exposed and then processed (e.g., by application of heat and/or chemicals) to fix the index-of-refraction changes produced by the laser light. 
     An illustrative photosensitive layer that is being exposed to a reference beam R and a signal beam S to create angle-of-view adjustment layer  24  is shown in  FIG. 5 . As shown in  FIG. 5 , reference beam R may be directed at layer  24  with a first orientation and signal beam S may be directed at layer  24  with a second orientation that is different than the first orientation. As an example, reference beam R may be a plane wave beam that is directed at layer  24  parallel to surface normal n of layer  24  (e.g., in alignment with a future “playback” beam of light emitted by a pixel  22 ). Signal beam S may be a plane wave beam or a beam with an angular spread (e.g., the beam may be a non-plane-wave beam having an angular spread associated with a desired angle-of-view) and may be oriented at an angle θ with respect to surface normal n. Due to fluctuations in light intensity from interfering R and S beams, patterns of index-of-refraction increases (e.g., holographic structures  54  such as Bragg gratings) are produced in the material of layer  24 . 
     If desired, holographic recording parameters may be varied during the formation of layer  24 , so that desired light spreading structures are created in layer  24 . Parameters that may be varied include the angular spread of the recording light beams (e.g., whether the reference and/or signal beams are collimated plane waves or are diverging), the wavelength of light of the recording beams, and the angle of orientation of the recording light beams. As an example, the holographic structures of layer  24  may be recorded using a plane wave for reference beam R and a plane wave for signal beam S while stepping the angular orientation θ of signal beam S through each of multiple different angular orientations corresponding to the desired orientations of diffracted light rays to be produced when light from pixel  22  is played back through layer  24 . Any suitable number of different angular orientations θ may be used for signal beam S (e.g., 1-100, 3-20, at least 5, at least 10, fewer than 200, etc.). 
     As another example, reference beam R may be a plane wave and signal beam S may have an angular spread equal to the desired angular spread for light passing through layer  22  during operation (e.g., 20-30°, at least 15°, less than 35°, etc.). 
     The wavelength of the reference and signal beams may match the wavelengths of anticipated light from pixels  22 . If, for example, the emitted light from pixels  22  includes red, green, and blue light from respective red, green, and blue pixels, then the wavelengths of the reference and signal beams may respectively be stepped through red, green, and blue wavelengths to form respective red holographic structures, green holographic structures, and blue holographic structures (in separate layers that overlap or in a common layer). The red holographic structures may be configured to redirect red light emitted from red pixels (e.g., red resonant cavity organic light-emitting diodes or other red pixels) without redirecting the emitted green light and without redirecting the emitted blue light and cover the red pixels, green pixels, and blue pixels. The green holographic structures may be configured to redirect green light emitted from green pixels without redirecting the emitted red light and without redirecting the emitted red light and cover the red pixels, green pixels, and blue pixels. The blue holographic structures may be configured to redirect blue light emitted from blue pixels without redirecting the emitted green light and without redirecting the emitted green light and cover the red pixels, green pixels, and blue pixels. 
     To accommodate the finite linewidths of pixels  22 , the recording laser beams may be stepped through multiple wavelengths within the linewidth of each pixel color. For example, the signal and reference beams may be adjusted to performing holographic recording at 1-100 different wavelengths, 3-20 wavelengths, at least 5 wavelengths, or fewer than 50 wavelengths, each of which corresponds to a wavelength within the linewidth of a given pixel color. As an example, 3-20 different red wavelengths may be used during holographic recording, each of which lies within the 10-30 nm linewidth of a light-emitting diode pixel in array  20 . Green and blue holographic structures may likewise be recorded using respectively multiple green wavelengths and multiple blue wavelengths. 
     In general, any suitable combination of angular orientation θ, angular spread, and wavelength may be used during recording of the holographic structures in layer  24 . By varying parameters such as these, the diffraction characteristic (light redirecting characteristic) of layer  24  can be configured to increase the angular spread of emitted light from pixels  22  to a desired value. 
     Consider, as an example, the scenarios of  FIGS. 6 and 7 . In this example, a given pixel  22  is emitting light (e.g., red light, green light, or blue light) with an intensity-versus-angle profile such as profile  58  of  FIG. 6 . After passing through layer  24 , this light may have an intensity-versus-angle profile such as profile  62  of  FIG. 7 . As shown in  FIGS. 6 and 7 , the width (e.g., the full-width-half-maximum width) of curve  58  (width  60 ) is smaller than the width of curve  62  (width  64 ), indicating that layer  24  has increased the angular spread of emitted light (e.g., to a desired angular spread associated with a viewing angle A of desired size such as 40-80°, at least 50°, less than 90°, or other suitable viewing angle). Moreover, as shown in  FIG. 7 , the widening of the angular distribution of the light intensity of the emitted light after passing through layer  24  takes place mostly or entirely at lower angles (e.g., on-axis light angles of between −AB and +AB). Far-off-axis light is not affected by layer  24  (e.g., light rays with angles greater in magnitude than angle AB are not disturbed and pass unaffected through layer  24 ). As a result, overly concentrated on-axis light (e.g., light within the FWHM angles associated with intensity profile LED_OUT of  FIG. 6 ) is spread outwardly to help create a satisfactory broadened angular distribution of image light without unnecessarily decreasing light intensities for rays of light that are already at wide angles (e.g., angles greater than angle AB). The spreading out and weakening of far-off-axis light is prevented. Satisfactory wide-angle visibility for images on display  14  is therefore maintained even when angle-of-view-adjustment layer  24  is incorporated into display  14 . The value of angle AB may be, for example, in the range of 40-65°, 30-85°, or other suitable value. 
     With one illustrative arrangement, the holographic recording process of  FIG. 5  may be performed globally on layer  24 , so that each area of the photosensitive film is recorded evenly and so that the holographic structures spread uniformly across all of display  14  and cover all pixels  22  in pixel array  20  without creating any individual holographic elements (e.g., without creating an array of individual pixel-sized holographic elements). With this type of arrangement, there is no need to laterally align layer  24  to the pixels  22  of array  20 . Layer  24  need only overlap pixel array  20  in display  14 . With another illustrative arrangement, holographic structures (e.g., red holographic structures for red pixels, green holographic structures for green pixels, and blue holographic structures for blue pixels) may be formed in pixel-sized regions on layer  24  and layer  24  may be aligned at the pixel level with pixels  22  (e.g., so that red holographic structures are aligned with red pixels, etc.). 
       FIG. 8  is a cross-sectional side view of display  14  showing how layer  24  may be placed on top of a polarizer layer such as circular polarizer  66 , so that polarizer  66  is interposed between layer  24  and pixel array  20 . Circular polarizer  66  may be used, for example, to help suppress ambient light reflections from structures in pixel array  22 .  FIG. 9  is a cross-sectional side view of display  14  in an illustrative configuration in which polarizer  66  (e.g., a circular polarizer) has been placed on top of layer  24 , so that layer  24  is interposed between polarizer  66  and pixel array  20 . The hologram for layer  24  may be configured in accordance with the location of layer  24  in display  14 . 
     In the illustrative configuration for display  14  that is shown in  FIG. 10 , pixel array  20  is formed from an array of pixels  22  in layer  68  (e.g., a layer containing a substrate, thin-film transistor circuitry, light-emitting diode structures, etc.). Pixels  22  may contain light-emitting diodes  70  (e.g., organic light-emitting diodes or microLEDs). Layer  72  may be formed from a. clear polymer or other material that is transparent to visible light. Ambient light rays such as ray  74  may pass through layer  24  and layer  72  and be absorbed in locations such as location  78  (e.g., in opaque materials in the upper portions of layer  68 ). Ambient light rays such as ray  76  may be guided within layer  72  and thereby prevented from reflected towards viewer  26 . 
     If desired, holographic structures may be used in directing light into and out of light-based components. Consider, as an example, the cross-sectional side view of display  14  of  FIG. 11 . In this example, device  10  has a display with an array of pixels  22  such as pixel array  20 . Pixel array  20  is formed in layer  68  (e.g., a substrate layer, thin-film transistor circuitry, etc.). Holographic structures  54 A and  54 B are formed in portions of layer  24 . Layer  24  may also include holographic structures that serve as angle-of-view adjustment structures to help enhance the angular spread of light emitted from pixels  22 . 
     Light-based component  80  may be overlapped by holographic structures such as structure  54 A. Component  80  may include components such as light-emitting diodes, lasers, and other light sources and may include light detectors (e.g., photodiodes, etc.). 
     Consider, as an example, a scenario in which component  80  of  FIG. 11  includes both a light-emitting device and a light detecting device that allows component  80  to serve as a light-based proximity detector (e.g., a proximity detector in a cellular telephone that determines when an ear speaker in the telephone is adjacent to a user&#39;s ear). Holographic structure  54 A may overlap the light-emitting device in component  80 , which is emitting light  84  outwardly through layer  68 . Holographic structure  54 A may serve as an input coupler that couples this light  84  from component  80  into layer  24 . Layer  24  may then serve as a thin-film waveguide that guides light  84  to holographic structure  54 B. Structure  54 B may serve as an output coupler that couples the emitted light  84  out of layer  24  towards external object  82 . Object  82  (e.g., the body of a user or other external object) may reflect the emitted light back towards structure  54 B, which may serve as an input coupler that couples light into the waveguide formed from layer  24 . After being guided to structure  54 A, which serves as an output coupler, the reflected light is directed towards the light detector in component  80 . The emitted and reflected light in this scenario may be, for example, infrared light. If desired, this type of arrangement may be used for any suitable light-based component (e.g., an ambient light sensor, status indicator light, image sensor, etc.). The use of holographic structures and waveguide techniques to redirect and guide light for component  80  may facilitate the incorporation of component  80  within the housing of device  10 . 
     If desired, angle-of-view adjustment structure  24  may be implemented using nanostructures that are imprinted or photolithographically formed on a substrate. These nanostructures may, for example, have feature sizes less than a wavelength of light and may form a metasurface that serves as an angle-of-view adjustment layer for display  14 . 
     Consider, as an example, the arrangement of  FIG. 12 . As shown in  FIG. 12 , layer  24  has a substrate such as substrate  90 . Substrate  90  may be formed from a clear layer of material (e.g., glass, polymer, ceramic, etc.). A layer of nanostructures  92  may be formed on substrate  90  by nanoprinting (e.g., using a titanium dioxide sol-gel slurry followed by a thermal cure) or photolithography (as examples) and may form a metasurface that allows layer  24  to serve as an angle-of-view adjustment layer. In the example of  FIG. 12 , nanostructures  92  are columns of high refractive index material such as a metal oxide (e.g., titanium oxide, zinc oxide, tin oxide, silicon dioxide, etc.) or other transparent non-conductive materials, etc. The column-to-column spacing of structures  92  (pitch PT) may be 0.1-5 microns, at least 0.2 microns, at least 0.5 microns, less than 50 microns, less than 25 microns, or other suitable distance. The lateral dimensions of structures  92  (width and depth in dimensions X and Y, respectively) may be less than visible light wavelengths (e.g., less than 0.5 microns, less than 0.4 microns, less than 0.3 microns, more than 0.1 microns, etc.) or may have other suitable sizes and may be significantly smaller than the lateral dimension of each pixel  22 . Pixels  22  may be rectangular, may be chevron shaped, or may have other suitable shapes and may have lateral dimensions of 5-300 microns, at least 10 microns, less than 70 microns, 50-250 microns, or other suitable size. The height of structures  92  in  FIG. 12  may be, for example, 0.2-1.2 microns, at least 0.3 microns, less than 1 micron, 0.6 microns, or other suitable size. As light from each pixel  22  passes through the nanosurface formed by structures  92 , this light is selectively retarded in phase due to the presence of each of nanostructures  92 . Nanostructures  92  may have a pattern such as the illustrative top view pattern of structures  92  of  FIG. 13  or other suitable pattern that allows structures  92  to enhance the angular spread of light emitted by pixels  22  and thereby serve as an angle-of-view adjustment layer for display  14 . 
     The space between nanostructures  92  may be empty (e.g., filled with air) and/or may be tilled with other transparent materials. For example, the space between nanostructures  92  may be filled with a transparent material with a low refractive index (such as a silicone polymer, a fluoropolymer, an acrylate polymer, etc.) which can serve as a means of mechanical protection for the nanostructures. The polymer layer can extend higher than nanostructures  92  to afford more protection. The polymer layer can be deposited through solution means, or evaporated. The polymer layer should have a refractive index lower than the nanostructures. 
       FIG. 14  is a side view of display  14  in an illustrative configuration in which nanostructures  92  have been patterned to form a set of red nanostructures (red light nanostructures)  92 R configured to spread (redirect) red light from red pixel  22 R, a set of green nanostructures (green light nanostructures)  92 G configured to spread (redirect) green light from green pixel  22 G, and blue nanostructures (blue light nanostructures)  92 B that are configured to spread (redirect) blue light from blue pixel  22 B. The configuration used for nanostructures  92 R (e.g., the sizes and layout pattern of each nanostructure in red nanostructures  92 R) may be different than the corresponding sizes and pattern of the green nanostructures  92 G. In turn, the green and blue nanostructures  92 G and  92 B may have different nanostructure sizes and layouts. This allows nanostructures  92 R,  92 G, and  92 B to each be tailored to spread light appropriately for a pixel of a different respective color (e.g., so that the resulting angular spread for red, green, and blue light is identical). This may help to minimize color shifts in images displayed on display  14  as a function of viewing angle. 
     Arrangements of the type shown in  FIG. 14  involve fabricating nanostructures  92  in alignment with pixels  22  either by forming nanostructures  92  directly on pixel array  20  as shown in  FIG. 14  or by aligning nanostructures  92  that have been formed on a separate substrate such as substrate  90  of  FIG. 12  with pixels  22  in pixel array  20 . If desired, alignment requirements may be relaxed by forming layer  24  from alignment-insensitive nanostructures. 
     As an example, layer  20  may be formed from multiple sets of interspersed nanostructures, where each set of nanostructures is configured to handle light at a different wavelength. These sets of interspersed nanostructures may be spread across all of substrate  90  uniformly and therefore need not be aligned with particular pixels  22  in array  20 . 
     Consider, as an example, layer  24  of  FIG. 15 . As shown in  FIG. 15 , the nanostructures on substrate  90  of layer  24  may include three sets of nanostructures nanostructures  92 R for adjusting the angle of view of red light from red pixels as well as nanostructures  92 G and nanostructures  92 B for green and blue pixel light, respectively). In this type of arrangement, red nanostructures  92 R are configured (by adjusting the distances between each of the red nanostructures  92 R and the size and shapes of these nanostructures) to interact with emitted red light from red pixels  22 R and to not interact significantly with green or blue light. At the same time, the placement, shapes, and sizes of the green nanostructures  92 G are selected so that the set of green nanostructures  92 G will interact with green light, but not red and blue light. The set of blue nanostructures  92 B that is interspersed with the red and green nanostructures is configured to interact with blue light, but not red and green light. Nanostructures  92 R,  92 G, and  92 B are not patterned in an array pattern to match the pixels of array  20  but rather are distributed uniformly across the surface of substrate  90  and layer  24  so that nanostructures  92 R overlap red, green, and blue pixels, nanostructures  92 G overlap red, green, and blue pixels, and nanostructures  92 B overlap red, green, and blue pixels. So long as layer  24  overlaps array  20 , layer  24  will satisfactorily widen the angle of view of the light emitted from pixel array  20  without the need to align particular portions of layer  24  to particular pixels of array  20 . 
     A metasurface angle-of-view adjustment layer such as layer  24  of  FIG. 16  may be incorporated into a display with a polarizer. As shown in  FIG. 16 , for example, display  14  may include circular polarizer  114  formed from linear polarizer  112  and quarter wave plate  110 . Polarizer  24  may be placed above or below layer  24  to help suppress ambient light reflections. In the example of  FIG. 16 , circular polarizer  114  has been interposed between angle-of-view adjustment layer  24  and pixel array  20 . Light from pixels  22  such as light-emitting diode pixels is initially unpolarized, but will be linearly polarized after passing through linear polarizer  112 . To accommodate the linear polarization of the light that reaches layer  24 , nanostructures  92  in layer  24  can be configured for optimal operation with linearly polarized light having a polarization axis aligned with the pass axis of linear polarizer  112 . 
     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: 20171102
Publication Date: 20210223
Grant Date: 20210223
Priority Date: 20170504
Inventors: DRZAIC, PAUL S.
Assignee: APPLE INC
CPC Classifications: [{"code": "H10K50/852", "inventive": false, "first": false, "tree": "[]"}, {"code": "G03H1/0005", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F2202/36", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133504", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133504", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/134309", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/32", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/134345", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F2202/36", "inventive": false, "first": false, "tree": "[]"}, {"code": "G03H2001/0212", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133562", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B5/32", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B1/002", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133562", "inventive": false, "first": false, "tree": "[]"}, {"code": "G03H2001/0088", "inventive": false, "first": false, "tree": "[]"}, {"code": "G03H2001/0216", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133507", "inventive": false, "first": false, "tree": "[]"}, {"code": "G03H1/0244", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L27/3246", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L51/5262", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F2001/133562", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F2001/134345", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F2001/133507", "inventive": false, "first": false, "tree": "[]"}, {"code": "G03H2001/0212", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L27/3234", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L27/3211", "inventive": true, "first": true, "tree": "[]"}, {"code": "F21Y2113/13", "inventive": false, "first": false, "tree": "[]"}, {"code": "G03H2001/0088", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F2202/36", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L51/5284", "inventive": false, "first": false, "tree": "[]"}, {"code": "G03H1/0005", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L51/5265", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133504", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/134309", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/32", "inventive": true, "first": false, "tree": "[]"}, {"code": "G03H2001/0216", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L51/5275", "inventive": true, "first": false, "tree": "[]"}, {"code": "G03H1/0244", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L2227/32", "inventive": false, "first": false, "tree": "[]"}, {"code": "H10K59/10", "inventive": false, "first": false, "tree": "[]"}, {"code": "G03H1/0244", "inventive": true, "first": true, "tree": "[]"}, {"code": "H10K50/85", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K59/35", "inventive": true, "first": true, "tree": "[]"}, {"code": "H10K50/865", "inventive": false, "first": false, "tree": "[]"}, {"code": "H10K59/65", "inventive": false, "first": false, "tree": "[]"}, {"code": "H10K59/35", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K59/122", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K59/65", "inventive": false, "first": false, "tree": "[]"}, {"code": "H10K59/876", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K59/879", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K59/8792", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 64014957