PATENT DOCUMENT

Publication Number: US-11852816-B1
Application Number: US-202117373210-A
Country: US
Kind Code: B1

Title: Optical systems with resolution-enhancing spectral shifting

Abstract:
The display may include a display module and a waveguide. The module may produce first light of first wavelengths during first time periods and may produce second light of second wavelengths during second time periods interleaved with the first time periods. Diffractive gratings or a dichroic wedge may redirect the first light into the waveguide at a first angle and may redirect the second light into the waveguide at a second angle separated from the first angle by a separation angle. The separation angle may be equal to half the angle subtended by the projection of a pixel in the module. The first and second time periods may alternate faster than the response of the human eye. This may configure the first and second image light to collectively provide images at an eye box with an increased effective resolution without increasing the space or power consumed by the display module.

Claims:
What is claimed is: 
     
       1. A display system configured to provide images to an eye box, the display system comprising:
 a display module configured to generate a beam of image light at a first wavelength during first time periods and at a second wavelength that is different from the first wavelength during second time periods that alternate with the first time periods; 
 a waveguide; 
 a wavelength-separating input coupling structure configured to:
 redirect into the waveguide, as first image light, light of the first wavelength from the beam of image light, wherein the first image light is redirected into the waveguide at a first angle, and 
 redirect into the waveguide, as second image light, light of the second wavelength from the beam of image light, wherein the second image light is redirected into the waveguide at a second angle that is separated from the first angle by a non-zero separation angle and wherein the waveguide is configured to propagate the first and second image light via total internal reflection; and 
 
 an output coupler configured to couple the first and second image light out of the waveguide and towards the eye box. 
 
     
     
       2. The display system of  claim 1 , wherein the second wavelength is within 20 nm of the first wavelength. 
     
     
       3. The display system of  claim 1 , wherein the display module comprises:
 a first light source configured to produce the beam of image light at the first wavelength, wherein the first light source is on during the first time periods and off during the second time periods; and 
 a second light source configured to produce the beam of image light at the second wavelength, wherein the second light source is on during the second time periods and off during the first time periods. 
 
     
     
       4. The display system of  claim 3 , wherein the display module further comprises:
 a reflective display panel, wherein the first light source is configured to provide illumination light of the first wavelength to the reflective display panel during the first time periods and wherein the second light source is configured to provide illumination light of the second wavelength to the reflective display panel during the second time periods. 
 
     
     
       5. The display system of  claim 4 , wherein the reflective display panel comprises a display panel selected from the group consisting of: a liquid crystal on silicon (LCOS) display panel and a digital-micromirror device (DMD) display panel. 
     
     
       6. The display system of  claim 4 , wherein the reflective display panel comprises a plurality of pixels and wherein the separation angle is equal to one-half an angle subtended by a projection of one pixel in the plurality of pixels. 
     
     
       7. The display system of  claim 1 , wherein the wavelength-separating input coupling structure comprises diffractive grating structures configured to diffract, onto the first angle, the light of the first wavelength from the beam of image light, and wherein the diffractive grating structures are configured to diffract, onto the second angle, the light of the second wavelength from the beam of image light. 
     
     
       8. The display system of  claim 7 , wherein the diffractive grating structures comprise transmissive diffraction grating structures. 
     
     
       9. The display system of  claim 8 , wherein the transmissive diffraction grating structures are embedded within the waveguide. 
     
     
       10. The display system of  claim 8 , wherein the waveguide has a first lateral surface facing the display module and a second lateral surface opposite the first lateral surface and wherein the transmissive diffraction grating structures are layered on the first lateral surface of the waveguide. 
     
     
       11. The display system of  claim 10 , further comprising:
 a reflective input coupling prism mounted to the second lateral surface of the waveguide, wherein the reflective input coupling prism is configured to reflect the first and second image light into the waveguide. 
 
     
     
       12. The display system of  claim 8 , wherein the transmissive diffraction grating structures comprise a structure selected from the group consisting of: a surface relief grating, a set of volume holograms, and a set of thin-film holograms. 
     
     
       13. The display system of  claim 7 , wherein the diffractive grating structures comprise reflective diffraction grating structures. 
     
     
       14. The display system of  claim 13 , wherein the waveguide has a first lateral surface facing the display module and a second lateral surface opposite the first lateral surface, the display system further comprising:
 a reflective input coupling prism mounted to the second lateral surface of the waveguide, wherein the reflective input coupling prism has a surface oriented at a non- parallel angle with respect to the second lateral surface and wherein the reflective diffraction grating structures are layered on the surface of the prism. 
 
     
     
       15. The display system of  claim 14 , wherein the reflective diffraction grating structures comprise a structure selected from the group consisting of: a surface relief grating, a set of volume holograms, and a set of thin-film holograms. 
     
     
       16. The display system of  claim 1 , wherein the waveguide has a first lateral surface facing the display module and a second lateral surface opposite the first lateral surface, the display system further comprising:
 a reflective input coupling prism mounted to the second lateral surface of the waveguide, wherein the reflective input coupling prism has a surface oriented at a non- parallel angle with respect to the second lateral surface; and 
 a dichroic wedge having a first surface mounted to the surface of the prism and having a second surface opposite the first surface, wherein the second surface is oriented at a non-parallel angle with respect to the first surface, wherein the first surface is configured to transmit the first image light, wherein the first surface is configured to reflect the second image light into the waveguide, and wherein the second surface is configured to reflect the first image light into the waveguide. 
 
     
     
       17. A display system configured to display images at an eye box, the display system comprising:
 first light sources configured to generate illumination light of a first set of wavelengths during first time periods; 
 second light sources configured to generate illumination light of a second set of wavelengths that is offset from the first set of wavelengths during second time periods, wherein the second time periods are interleaved with the first time periods; 
 a reflective display panel configured to produce first image light by reflecting the first illumination light and configured to produce second image light by reflecting the second illumination light; 
 a waveguide having a lateral surface; 
 at least one transmissive diffraction grating layered on the lateral surface of the waveguide, wherein the at least one transmissive diffraction grating is configured to:
 receive the first image light at an incident angle during the first time periods; 
 receive the second image light at the incident angle during the second time periods; 
 diffract the first image light into the waveguide at a first output angle, and 
 diffract the second image light into the waveguide at a second output angle that is separated from the first output angle by a non-zero separation angle, wherein the waveguide is configured to propagate the first and second image light via total internal reflection; and 
 
 an output coupler configured to couple the first and second image light out of the waveguide and towards the eye box. 
 
     
     
       18. The display system of  claim 17 , wherein the waveguide has an additional lateral surface opposite the lateral surface and wherein the display system further comprises:
 a reflective input coupling prism mounted to the additional lateral surface, wherein the reflective input coupling prism has a reflective surface that is configured to receive the first and second image light diffracted by the at least one transmissive diffraction grating and that is configured to reflect the first and second image light into the waveguide. 
 
     
     
       19. The display system of  claim 17 , wherein the at least one transmissive diffraction grating comprises a structure selected from the group consisting of: a surface relief grating, a set of volume holograms, and a set of thin-film holograms. 
     
     
       20. The display system of  claim 17 , wherein the second set of wavelengths is offset from the first set of wavelengths by less than or equal to 20 nm. 
     
     
       21. A display system configured to display images at an eye box, the display system comprising:
 first light sources configured to generate illumination light of a first set of wavelengths during first time periods; 
 second light sources configured to generate illumination light of a second set of wavelengths that is offset from the first set of wavelengths during second time periods, wherein the second time periods are interleaved with the first time periods; 
 a reflective display panel configured to produce first image light by reflecting the first illumination light and configured to produce second image light by reflecting the second illumination light; 
 a waveguide having a lateral surface; 
 a prism mounted to the lateral surface of the waveguide, wherein the prism has a reflective surface oriented at a non-parallel angle with respect to the lateral surface of the waveguide; and 
 a wedge having a first surface mounted to the reflective surface of the prism and having a second surface opposite the first surface, wherein the second surface is oriented at a non-parallel angle with respect to the first surface, wherein at least one coating is interposed between the reflective surface and the first surface, wherein the at least one coating is configured to transmit the first image light, wherein the second surface is configured to reflect the first image light into the waveguide at a first angle, and wherein the at least one coating is configured to reflect the second image light into the waveguide at a second angle that is separated from the first angle by a non-zero separation distance. 
 
     
     
       22. The display system of  claim 21 , wherein the waveguide is configured to propagate the first and second image light via total internal reflection and wherein the display system further comprises:
 an output coupler configured to couple the first and second image light out of the waveguide and towards the eye box. 
 
     
     
       23. The display system of  claim 21 , wherein the second set of wavelengths is offset from the first set of wavelengths by less than or equal to 20 nm.

Description:
This application claims the benefit of U.S. Provisional Patent Application No. 63/051,330, filed Jul. 13, 2020, which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     This relates generally to optical systems and, more particularly, to optical systems for displays. 
     Electronic devices may include displays that present images to a user&#39;s eyes. For example, devices such as virtual reality and augmented reality headsets may include displays with optical elements that allow users to view the displays. In general, there is a demand for displays to provide images with as high an image resolution as possible. 
     However, it can be challenging to design devices such as these. If care is not taken, the components used in displaying content may be unsightly and bulky, can consume excessive power, and may not exhibit desired levels of optical performance. 
     SUMMARY 
     An electronic device such as a head-mounted device may have one or more near-eye displays that produce images for a user. The head-mounted device may be a pair of virtual reality glasses or may be an augmented reality headset that allows a viewer to view both computer-generated images and real-world objects in the viewer&#39;s surrounding environment. 
     The near-eye display may provide images to an eye box. The display may include a display module and a waveguide. The display module may include first light sources that produce first illumination light of a first set of wavelengths. The display module may include second light sources that produce second illumination light of a second set of wavelengths that is offset from the first set of wavelengths (e.g., by 20 nm or less). The display module may include a reflective display panel that reflects the first illumination light to produce first image light and that reflects the second illumination light to produce second image light. The first light sources may be turned on during first time periods and the second light sources may be turned on during second time periods that are interleaved with the first time periods. 
     The display may include wavelength-separating input coupling structures. The first and second image light may be aligned and may be provided to a common locus at the wavelength-separating input coupling structures (e.g., at the same incident angle and location during the first and second time periods). The wavelength-separating input coupling structures may redirect the first image light into the waveguide at a first angle. The wavelength-separating input coupling structures may redirect the second image light into the waveguide at a second angle that is separated from the first angle by a non-zero separation angle. The wavelength-separating input coupling structures may include one or more transmissive diffraction gratings, one or more reflective diffraction gratings, or a dichroic wedge. 
     The waveguide may propagate the first and second image light via total internal reflection. An output coupler may couple the first and second image light out of the waveguide and towards the eye box. The reflective display panel may include pixels. The separation angle between the first and second image light may be equal to one-half of the angle subtended by the projection of one of the pixels. The first and second time periods may alternate faster than the response time of the human eye. This may configure the first and second image light to collectively provide images with an increased effective resolution at the eye box, without increasing the space or power consumed by the display module. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a diagram of an illustrative system having a display in accordance with some embodiments. 
         FIG.  2    is a top view of an illustrative optical system having a waveguide with wavelength-separating input coupling structures for maximizing image resolution at an eye box in accordance with some embodiments. 
         FIG.  3    is a front view of pixels of image light that illustrates how an illustrative optical system having wavelength-separating input coupling structures may increase the effective resolution of the image light in accordance with some embodiments. 
         FIG.  4    is a top view of an illustrative optical system having a reflective input coupling prism and having wavelength-separating input coupling structures formed from transmissive diffraction grating structures in accordance with some embodiments. 
         FIG.  5    is a top view of an illustrative optical system having wavelength-separating input coupling structures formed from transmissive diffraction grating structures that couple light into a waveguide without an input coupling prism in accordance with some embodiments. 
         FIG.  6    is a top view of an illustrative optical system having a reflective input coupling prism and having wavelength-separating input coupling structures formed from reflective diffraction grating structures on the prism in accordance with some embodiments. 
         FIG.  7    is an illustrative field angle sensitivity plot for diffraction grating structures of the types shown in  FIGS.  4 - 6    in accordance with some embodiments. 
         FIG.  8    is a top view of an illustrative optical system having a reflective input coupling prism and having wavelength-separating input coupling structures formed from a dichroic wedge on the prism in accordance with some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     An illustrative system having a device with one or more near-eye display systems is shown in  FIG.  1   . System  10  may be a head-mounted device having one or more displays such as near-eye displays  14  mounted within support structure (housing)  20 . Support structure  20  may have the shape of a pair of eyeglasses (e.g., supporting frames), may form a housing having a helmet shape, or may have other configurations to help in mounting and securing the components of near-eye displays  14  on the head or near the eye of a user. Near-eye displays  14  may include one or more display modules such as display modules  14 A and one or more optical systems such as optical systems  14 B. Display modules  14 A may be mounted in a support structure such as support structure  20 . Each display module  14 A may emit light  22  (sometimes referred to herein as image light  22 ) that is redirected towards a user&#39;s eyes at eye box  24  using an associated one of optical systems  14 B. 
     The operation of system  10  may be controlled using control circuitry  16 . Control circuitry  16  may include storage and processing circuitry for controlling the operation of system  10 . Circuitry  16  may include storage such as hard disk drive storage, nonvolatile memory (e.g., electrically-programmable-read-only memory configured to form a solid state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in control circuitry  16  may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio chips, graphics processing units, application specific integrated circuits, and other integrated circuits. Software code (instructions) may be stored on storage in circuitry  16  and run on processing circuitry in circuitry  16  to implement operations for system  10  (e.g., data gathering operations, operations involving the adjustment of components using control signals, image rendering operations to produce image content to be displayed for a user, etc.). 
     System  10  may include input-output circuitry such as input-output devices  12 . Input-output devices  12  may be used to allow data to be received by system  10  from external equipment (e.g., a tethered computer, a portable device such as a handheld device or laptop computer, or other electrical equipment) and to allow a user to provide head-mounted device  10  with user input. Input-output devices  12  may also be used to gather information on the environment in which system  10  (e.g., head-mounted device  10 ) is operating. Output components in devices  12  may allow system  10  to provide a user with output and may be used to communicate with external electrical equipment. Input-output devices  12  may include sensors and other components  18  (e.g., image sensors for gathering images of real-world object that are digitally merged with virtual objects on a display in system  10 , accelerometers, depth sensors, light sensors, haptic output devices, speakers, batteries, wireless communications circuits for communicating between system  10  and external electronic equipment, etc.). In one suitable arrangement that is sometimes described herein as an example, components  18  may include gaze tracking sensors that gather gaze image data from a user&#39;s eye at eye box  24  to track the direction of the user&#39;s gaze in real time. 
     Display modules  14 A (sometimes referred to herein as display engines  14 A, light engines  14 A, or projectors  14 A) may include reflective displays (e.g., displays having arrays of light sources that produce illumination light that reflect off of a reflective display panel to produce image light such as liquid crystal on silicon (LCOS) displays, digital-micromirror device (DMD) displays, or other spatial light modulators), emissive displays (e.g., micro-light-emitting diode (uLED) displays, organic light-emitting diode (OLED) displays, laser-based displays, etc.), or displays of other types. Light sources in display modules  14 A may include uLEDs, OLEDs, LEDs, lasers, combinations of these, or any other desired light-emitting components. 
     Optical systems  14 B may form lenses that allow a viewer (see, e.g., a viewer&#39;s eyes at eye box  24 ) to view images on display(s)  14 . There may be two optical systems  14 B (e.g., for forming left and right lenses) associated with respective left and right eyes of the user. A single display  14  may produce images for both eyes or a pair of displays  14  may be used to display images. In configurations with multiple displays (e.g., left and right eye displays), the focal length and positions of the lenses formed by components in optical system  14 B may be selected so that any gap present between the displays will not be visible to a user (e.g., so that the images of the left and right displays overlap or merge seamlessly). 
     If desired, optical system  14 B may contain components (e.g., an optical combiner, etc.) to allow real-world image light from real-world images or objects  25  to be combined optically with virtual (computer-generated) images such as virtual images in image light  22 . In this type of system, which is sometimes referred to as an augmented reality system, a user of system  10  may view both real-world content and computer-generated content that is overlaid on top of the real-world content. Camera-based augmented reality systems may also be used in device  10  (e.g., in an arrangement in which a camera captures real-world images of object  25  and this content is digitally merged with virtual content at optical system  14 B). 
     System  10  may, if desired, include wireless circuitry and/or other circuitry to support communications with a computer or other external equipment (e.g., a computer that supplies display  14  with image content). During operation, control circuitry  16  may supply image content to display  14 . The content may be remotely received (e.g., from a computer or other content source coupled to system  10 ) and/or may be generated by control circuitry  16  (e.g., text, other computer-generated content, etc.). The content that is supplied to display  14  by control circuitry  16  may be viewed by a viewer at eye box  24 . 
       FIG.  2    is a top view of an illustrative display  14  that may be used in system  10  of  FIG.  1   . As shown in  FIG.  2   , near-eye display  14  may include one or more display modules such as display module(s)  14 A and an optical system such as optical system  14 B. Optical system  14 B may include optical elements such as one or more waveguides  26 . Waveguide  26  may include one or more stacked substrates (e.g., stacked planar and/or curved layers sometimes referred to herein as waveguide substrates) of optically transparent material such as plastic, polymer, glass, etc. 
     If desired, waveguide  26  may also include one or more layers of holographic recording media (sometimes referred to herein as holographic media, grating media, or diffraction grating media) on which one or more diffractive gratings are recorded (e.g., holographic phase gratings, sometimes referred to herein as holograms). A holographic recording may be stored as an optical interference pattern (e.g., alternating regions of different indices of refraction) within a photosensitive optical material such as the holographic media. The optical interference pattern may create a holographic phase grating that, when illuminated with a given light source, diffracts light to create a three-dimensional reconstruction of the holographic recording. The holographic phase grating may be a non-switchable diffractive grating that is encoded with a permanent interference pattern or may be a switchable diffractive grating in which the diffracted light can be modulated by controlling an electric field applied to the holographic recording medium. Multiple holographic phase gratings (holograms) may be recorded within (e.g., superimposed within) the same volume of holographic medium if desired. The holographic phase gratings may be, for example, volume holograms or thin-film holograms in the grating medium. The grating media may include photopolymers, gelatin such as dichromated gelatin, silver halides, holographic polymer dispersed liquid crystal, or other suitable holographic media. 
     Diffractive gratings on waveguide  26  may include holographic phase gratings such as volume holograms or thin-film holograms, meta-gratings, or any other desired diffractive grating structures. The diffractive gratings on waveguide  26  may also include surface relief gratings formed on one or more surfaces of the substrates in waveguides  26 , gratings formed from patterns of metal structures, etc. The diffractive gratings may, for example, include multiple multiplexed gratings (e.g., holograms) that at least partially overlap within the same volume of grating medium (e.g., for diffracting different colors of light and/or light from a range of different input angles at one or more corresponding output angles). 
     Optical system  14 B may include collimating optics such as collimating lens  33 . Collimating lens  33  may include one or more lens elements that help direct image light  22  towards waveguide  26 . Collimating lens  33  may be omitted if desired. If desired, display module(s)  14 A may be mounted within support structure  20  of  FIG.  1    while optical system  14 B may be mounted between portions of support structure  20  (e.g., to form a lens that aligns with eye box  24 ). Other mounting arrangements may be used, if desired. 
     As shown in  FIG.  2   , display module(s)  14 A may generate image light  22  associated with image content to be displayed to eye box  24 . Image light  22  may be collimated using a lens such as collimating lens  33 . Optical system  14 B may be used to present the image light output from display module(s)  14 A to eye box  24 . 
     Optical system  14 B may include one or more optical couplers such as input coupler  28 , cross-coupler  32 , and output coupler  30 . In the example of  FIG.  2   , input coupler  28 , cross-coupler  32 , and output coupler  30  are formed at or on waveguide  26 . Input coupler  28 , cross-coupler  32 , and/or output coupler  30  may be completely embedded within the substrate layers of waveguide  26 , may be partially embedded within the substrate layers of waveguide  26 , may be mounted to waveguide  26  (e.g., mounted to an exterior surface of waveguide  26 ), etc. 
     The example of  FIG.  2    is merely illustrative. One or more of these couplers (e.g., cross-coupler  32 ) may be omitted. Optical system  14 B may include multiple waveguides that are laterally and/or vertically stacked with respect to each other. Each waveguide may include one, two, all, or none of couplers  28 ,  32 , and  30 . Waveguide  26  may be at least partially curved or bent if desired. 
     Waveguide  26  may guide the image light down its length via total internal reflection. Input coupler  28  may be configured to couple the image light  22  from display module(s)  14 A into waveguide  26 , whereas output coupler  30  may be configured to couple the image light from within waveguide  26  to the exterior of waveguide  26  and towards eye box  24 . Input coupler  28  may include an input coupling prism in one suitable arrangement. As an example, display module(s)  14 A may emit image light  22  in the +Y direction towards optical system  14 B. When image light  22  strikes input coupler  28 , input coupler  28  may redirect the image light so that the light propagates within waveguide  26  via total internal reflection towards output coupler  30  (e.g., in the +X direction). When the image light strikes output coupler  30 , output coupler  30  may redirect the image light out of waveguide  26  towards eye box  24  (e.g., in the −Y direction). In scenarios where cross-coupler  32  is formed at waveguide  26 , cross-coupler  32  may redirect the image light in one or more directions as it propagates down the length of waveguide  26 , for example. 
     Input coupler  28 , cross-coupler  32 , and/or output coupler  30  may be based on reflective and refractive optics or may be based on holographic (e.g., diffractive) optics. In arrangements where couplers  28 ,  30 , and  32  are formed from reflective and refractive optics, couplers  28 ,  30 , and  32  may include one or more reflectors (e.g., an array of micromirrors, partial mirrors, louvered mirrors, or other reflectors). In arrangements where couplers  28 ,  30 , and  32  are based on holographic optics, couplers  28 ,  30 , and  32  may include diffractive gratings (e.g., volume holograms, surface relief gratings, etc.). 
     In one suitable arrangement that is sometimes described herein as an example, output coupler  30  is formed from diffractive gratings or micromirrors embedded within waveguide  26  (e.g., volume holograms recorded on a grating medium stacked between transparent polymer waveguide substrates, an array of micromirrors embedded in a polymer layer interposed between transparent polymer waveguide substrates, etc.). If desired, input coupler  28  may include a prism mounted to an exterior surface of waveguide  26  (e.g., an exterior surface defined by a waveguide substrate that contacts the grating medium or the polymer layer used to form output coupler  30 ). 
     It may be desirable to display high resolution images at eye box  24 . In general, increasing the size and power consumption of display module  14 A may allow images to be displayed at eye box  24  with higher resolutions. However, it may be desirable for display module  14 A to be as compact and to consume as little power as possible. In order to increase the effective resolution of the images provided to eye box  24  without significantly increasing the size or power consumption of display module  14 A, display module  14 A may include first and second sets of light sources  34 A and  34 B and input coupler  28  may include wavelength-separating input coupling structures  36 . 
     The first set of light sources  34 A (sometimes referred to herein as first light sources  34 A) may be used to produce image light  22  at a first set of wavelengths λ (e.g., within a first set of color bands such as red, green, and blue color bands). The second set of light sources  34 B (sometimes referred to herein as second light sources  34 B) may be used to produce image light  22  at a second set of wavelengths λ-Δλ that are separated in wavelength from the first set of wavelengths λ produced by light sources  34 A by a wavelength offset Δλ. For example, second light sources  34 B may be used to produce image light  22  within a second set of color bands such as a red color band that is shifted by wavelength offset Δλ relative to the red color band produced by first light sources  34 A, a green color band that is shifted by wavelength offset Δλrelative to the green color band produced by first light sources  34 A, and a blue color band that is shifted by wavelength offset Δλ relative to the blue color band produced by first light sources  34 A. The same wavelength offset Δλ may be used for each color band or different offsets may be used for different color bands if desired. As examples, wavelength offset Δλ may be approximately 10 nm, 5 nm, 1 nm, 20 nm, 25 nm, 30 nm, 1-10 nm, 5-20 nm, 10-30 nm, 1-30 nm, 5-15 nm, less than 50 nm, greater than 1 nm, greater than 10 nm, or any other desired value. Light sources  34 A and  34 B may include uLEDs, OLEDs, LEDs, lasers, combinations of these, or any other desired light-emitting components. 
     Control circuitry  16  ( FIG.  1   ) may control display module  14 A to rapidly alternate between using first light sources  34 A and second light sources  34 B to produce image light  22  over time. Display module  14 A may alternate between first light sources  34 A and  34 B at a rate faster than the response rate of the human eye, for example. When first light sources  34 A are on/active (e.g., while second light sources  34 B are off/inactive), image light  22  is produced by first light sources  34 A and is provided to input coupler  28  at the first set of wavelengths λ. When second light sources  34 B are on/active (e.g., while first light sources  34 A are off/inactive), image light  22  is produced by second light sources  34 B and is provided to input coupler  28  at the second set of wavelengths λ-Δλ. 
     Wavelength-separating input coupling structures  36  (sometimes referred to herein as wavelength-splitting input coupling structures  36 ) may be formed on a lateral surface of waveguide  26 , may be formed on a surface of an input coupling prism in input coupler  28 , or may be embedded within waveguide  26 . Wavelength-separating input coupling structures  36  may serve to separate incident image light  22  by color (wavelength) prior to the image light propagating down the length of waveguide  26  via total internal reflection. For example, wavelength-separating input coupling structures  36  may receive image light  22  at the same incident angle regardless of whether the image light  22  is provided at the first set of wavelengths λ or at the second set of wavelengths λ-Δλ. Wavelength-separating input coupling structures  36  may redirect the image light  22  at the first set of wavelengths λ in a first direction (e.g., onto a first output angle or range of output angles), as image light  22 ′. Image light  22 ′, which is at the first set of wavelengths λ, may propagate down the length of waveguide  26  via total internal reflection. Cross coupler  32  may optionally redirect image light  22 ′. Output coupler  30  may couple image light  22 ′ out of waveguide  26  and towards eye box  24 . Similarly, wavelength-separating input coupling structures  36  may redirect the image light  22  at the second set of wavelengths λ-Δλ in a second direction (e.g., onto a second output angle or range of output angles), as image light  22 ″. Image light  22 ″, which is at the second set of wavelengths λ-Δλ, may propagate down the length of waveguide  26  via total internal reflection. Cross coupler  32  may optionally redirect image light  22 ″. Output coupler  30  may couple image light  22 ″ out of waveguide  26  and towards eye box  24 . 
     Wavelength-separating input coupling structures  36  may output image light  22 ′ and image light  22 ″ prior to the image light being coupled into waveguide  26  or wavelength-separating input coupling structures  36  may also serve to couple image light  22 ′ and image light  22 ″ into waveguide  26 . Wavelength-separating input coupling structures  36  may output image light  22 ″ at an angular offset (sometimes referred to herein as a separation angle) with respect to the image light  22 ′ output by wavelength-separating input coupling structures  36 . Image light  22 ′ may also be angularly offset from image light  22 ″ (e.g., by the separation angle) at eye box  24 . Image light  22 ′ and image light  22 ″ may both be used to convey the same frames of image data (e.g., frames from a stream of video data). The separation angle may, for example, be one-half the angle subtended by the projection of one pixel of display module  14 A (e.g., by one pixel of the frames of image data). Wavelength offset Δλ may be sufficiently small so as to allow image light  22 ′ and image light  22 ″ to appear to the user to be the same or approximately the same color (e.g., less than 50 nm, less than 30 nm, less than 20 nm, less than 10 nm, etc.). By rapidly toggling between production of image light  22  by first light sources  34 A (e.g., at the first set of wavelengths λ) and production of image light  22  by second light sources  34 B (e.g., at the second set of wavelengths λ-Δλ), the combination of image light  22 ″ and image light  22 ′ at eye box  24  may cause the image frames to appear at eye box  24  with an effective resolution that is greater than (e.g., twice) the resolution the image frames would have in scenarios where second light sources  34 B and wavelength-separating input coupling structures  36  are omitted. In other words, display  14  of  FIG.  2    may produce images at eye box  24  that have an increased effective resolution without significantly increasing the size or power consumption within display  14 . 
       FIG.  3    is a front view showing how light sources  34 A and  34 B and wavelength-separating input coupling structures  36  may provide images with an increased effective resolution at eye box  24  (e.g., as taken in the direction of arrow  25  of  FIG.  2   ). In the example of  FIG.  3   , four pixels of image light of a single color (wavelength) are shown for the sake of clarity. In general, the image light and the display module may include any desired number of pixels of any desired number of colors/wavelengths. 
     As shown in  FIG.  3   , image light  22  may include pixels P 1 , P 2 , P 3 , and P 4  of image data provided at a given wavelength from the first set of wavelengths λ (e.g., by first light sources  34 A of  FIG.  2   ). Wavelength-separating input coupling structures  36  may redirect image light  22  at the given wavelength from the first set of wavelengths λ, in a first direction (output angle), as image light  22 ′. In addition, image light  22  may include pixels P 1 ′, P 2 ′, P 3 ′, and P 4 ′ of image data provided at a given wavelength from the second set of wavelengths λ-Δλ (e.g., by second light sources  34 B of  FIG.  2   ). Wavelength-separating input coupling structures  36  may redirect image light  22  at the given wavelength from the second set of wavelengths λ-Δλ in a second direction (output angle), as image light  22 ″. The second direction may be angularly offset from the first direction such that, at eye box  24 , pixels P 1 , P 2 , P 3 , and P 4  are respectively displaced from pixels P 1 ′, P 2 ′, P 3 ′, and P 4 ′ by (angular) displacement (offset)  44 . Displacement  44  may, for example, be a two-dimensional displacement that includes offset  42  parallel to the Z-axis and/or offset  40  parallel to the X-axis. 
     Pixels P 1 , P 2 , P 3 , and P 4  may exhibit a first pixel pitch and pixels P 1 ′, P 2 ′, P 3 ′, and P 4 ′ may exhibit the first pixel pitch. However, the combination of pixels P 1 , P 2 , P 3 , and P 4  with pixels P 1 ′, P 2 ′, P 3 ′, and P 4 ′ may exhibit a second pixel pitch that is less than (e.g., half) the first pixel pitch. By rapidly toggling between providing image light  22 ′ and image light  22 ″ to eye box  24  (e.g., by rapidly toggling between first light sources  34 A and second light sources  34 B), the image light may effectively include each of pixels P 1 , P 2 , P 3 , P 4 , P 1 ′, P 2 ′, P 3 ′, and P 4 ′ (e.g., as perceived by a user at the eye box) and thus the second pixel pitch, rather than only pixels P 1 , P 2 , P 3 , and P 4  and the first pixel pitch (e.g., in scenarios where wavelength-separating input coupling structures  36  are omitted). For example, first light sources  34 A may be active to produce image light  22 ′ during first time periods and second light sources  34 B may be active to produce image light  22 ″ during second time periods that are interleaved, interspersed, or alternating with the first time periods. This may serve to maximize the effective resolution of images in the image light without significantly increasing the size or power consumption of the display. 
     Wavelength-separating input coupling structures  36  may include any desired optical structures that redirect different wavelengths of light incident at the same incident angle onto different respective output angles (e.g., output angles that are angularly separated by less than the angle subtended by the projection of one display module pixel). For example, wavelength-separating input coupling structures  36  may include diffractive grating structures. The diffractive grating structures may include transmissive diffraction gratings (e.g., transmission holograms) or reflective diffraction gratings (e.g., reflection holograms).  FIG.  4    is a diagram showing how wavelength-separating input coupling structures  36  may include transmissive diffraction gratings. 
     As shown in  FIG.  4   , input coupler  28  may include a prism (e.g., a reflective input coupling prism) such as prism  58 . Prism  58  may have a bottom surface  64  mounted to exterior (lateral) surface  60  of waveguide  26  (e.g., using an optically clear adhesive not shown in  FIG.  4    for the sake of clarity). Waveguide  26  may have an exterior (lateral) surface  62  that faces display module  14 A. 
     In the example of  FIG.  4   , display module  14 A is a reflective display module in which the light sources of the display module reflect illumination light off of a reflective spatial light modulator, such as reflective display panel  56 , to produce image light  22 . This is merely illustrative and, in general, display module  14 A may be an emissive display module, a transmissive display module, or any other desired light projector that includes first light sources  34 A and second light sources  34 B. 
     Display module  14 A may include first light sources  34 A and second light sources  34 B. First light sources  34 A may be interspersed (interleaved) among second light sources  34 B or may be grouped separately from second light sources  34 B. First light sources  34 A may emit illumination light  50  at the first set of wavelengths λ. The first set of wavelengths λ may include a first wavelength range λ1 (e.g., a range of red wavelengths or any other desired wavelength range or a single wavelength within that range), a second wavelength range λ3 (e.g., a range of green wavelengths or any other desired wavelength range or a single wavelength within that range), and a third wavelength range λ3 (e.g., a range of blue wavelengths or any other desired wavelength range or a single wavelength within that range). Second light sources  34 B may emit illumination light  50  at the second set of wavelengths λ-Δλ. The second set of wavelengths λ-Δλmay include a fourth wavelength range λ1-Δλ (e.g., a range of red wavelengths or any other desired wavelength range or a single wavelength within that range), a fifth wavelength range λ2-Δλ (e.g., a range of green wavelengths or any other desired wavelength range or a single wavelength within that range), and a sixth wavelength range λ3-Δλ (e.g., a range of blue wavelengths or any other desired wavelength range or a single wavelength within that range). The fourth through sixth wavelength ranges may be offset from the first through third wavelength ranges, respectively, by the same wavelength offset Δλ or by different respective wavelength offsets. 
     Display module  14 A may include prism  54 . Optical structures  52  may redirect illumination light  50  from first light sources  34 A and second light sources  34 B towards prism  54 . Optical structures  52  may include mirrors, partial mirrors, beam splitters, prisms, lenses, polarizers, or any other desired optical components. Display module  14 A may include a reflective spatial light modulator such as reflective display panel  56 . Display panel  56  may include a DMD panel, an LCOS panel, or any other desired reflective display panel. Prism  54  may direct illumination light  50  to display panel  56  (e.g., different pixels P* on display panel  56 ). Control circuitry  16  ( FIG.  1   ) may control display panel  56  to selectively reflect illumination light  50  at each pixel location to produce image light  22  (e.g., image light having an image as modulated onto the illumination light by display panel  56 ). Prism  54  may direct image light  22  to collimating optics  33 . 
     When first light sources  34 A are active, illumination light  50  and thus image light  22  includes light of wavelengths ranges λ1, λ2, and λ3. When second light sources  34 B are active, illumination light  50  and thus image light  22  includes light of wavelengths ranges λ1-Δλ, λ2,Δλ, and λ3-Δλ. Control circuitry  16  ( FIG.  1   ) may rapidly alternate between activating first light sources  34 A and second light sources  34 B (e.g., to produce image light  22 ′ and  22 ″ of  FIG.  3    having a maximal effective resolution at the eye box). 
     As shown in  FIG.  4   , wavelength-separating input coupling structures  36  may be layered onto surface  62  of waveguide  26 . Wavelength-separating input coupling structures  36  may include transmissive diffraction grating structures such as at least one transmissive diffraction grating  72 . The transmissive diffraction gratings  72  in structures  36  may include surface relief gratings, thin film holograms (e.g., thin film transmission holograms), volume holograms (e.g., transmission volume holograms), meta-gratings, or other transmissive diffraction gratings that diffract image light  22  incident in the +Y direction onto an output angle 0 that is less than 90 degrees with respect to the +Y direction (axis  68 ). Transmissive diffraction gratings  72  may each be formed in the same layer of grating medium, each transmissive diffraction grating may be formed in a respective layer of grating medium layered onto surface  62  of waveguide  26 , or structures  36  may include multiple layers of grating medium that each include one or more transmissive diffraction gratings. 
     Transmissive diffraction gratings  72  may diffract image light  22  incident parallel to the Y-axis at wavelength ranges λ1, λ2, and λ3 onto output angle θ1 with respect to the Y-axis, as a beam of image light  22 ′ (e.g., transmissive diffraction gratings  72  may include transmissive diffraction gratings that are Bragg-matched to image light  22  incident parallel to the Y-axis at wavelength ranges λ1, λ2, and λ3 such that the transmissive diffraction gratings diffract this image light onto output angle θ1 as image light  22 ′). In addition, transmissive diffraction gratings  72  may diffract image light  22  incident parallel to the Y-axis at wavelength ranges λ1-Δλ, λ2-Δλ, and λ3-Δλ onto output angle θ2, as a beam of image light  22 ″ (e.g., transmissive diffraction gratings  72  may include transmissive diffraction gratings that are Bragg-matched to image light  22  incident parallel to the Y-axis at wavelength ranges λ1-Δλ, λ2-Δλ, and λ3-Δλsuch that the transmissive diffraction gratings diffract this image light onto output angle θ2 as image light  22 ″). 
     Output angle θ2 is different from (e.g., less than) output angle θ1. Image light  22 ′ may pass through waveguide  26 , surface  60 , surface  64 , and prism  58  to surface  66  of prism  58 . Surface  66  (sometimes referred to herein as reflective surface  66 ) may be oriented non-parallel with respect to surface  60  of waveguide  26 . Reflective surface  66  may reflect image light  22 ′ at a first reflection angle back into waveguide  26 . The first reflection angle may be an angle such that, upon passing back into waveguide  26 , image light  22 ′ continues to propagate down waveguide  26  via total internal reflection. Similarly, image light  22 ″ may pass through waveguide  26 , surface  60 , surface  64 , and prism  58  to reflective surface  66 . Reflective surface  66  may reflect image light  22 ″ at a second reflection angle back into waveguide  26 . The second reflection angle may be an angle such that upon passing back into waveguide  26 , image light  22 ″ continues to propagate down waveguide  26  via total internal reflection, An optional reflective coating such as a metallic or dielectric coating may be layered over reflective surface  66  if desired. 
     Image light  22 ′ may be angularly separated from image light  22 ″ by separation angle θ1-θ2. Separation angle θ1-θ2 may be selected so that pixels P 1 -P 4  of image light  22 ′ are separated from pixels P 1 ′-P 4 ′ of image light  22 ″ by displacement  44  at eye box  24  ( FIG.  3   ). In. order to support this angular separation, the grating pitch of transmissive diffraction gratings  72  may, for example, be selected to produce output angles θ1 and θ2 that satisfy the equation θ1-θ2 =φ/2, where φ is the angle subtended by the projection of one pixel P* of display panel  56 . When first light sources  34 A are active, transmissive diffraction gratings  72  provide image light  22 ′ at output angle θ1 for the eye box. When second light sources  34 B are active, transmissive diffraction gratings  72  provide image light  22 ″ at output angle θ2 for the eye box. By alternating between providing image light  22 ′ and  22 ″ to the eye box. (e.g., at a rate faster than the response speed of the human eye, at greater than 24 Hz, at greater than 30 Hz, at greater than 60 Hz, at greater than 120 Hz, at greater than 240 Hz, etc.), image light  22 ′ and  22 ″ may collectively produce images at the eye box that have twice the effective resolution as would be present if only a single set of light sources were used and if structures  36  were omitted. 
     As one example, transmissive diffraction gratings  72  may include a single diffraction grating (e.g., a broadband grating such as a surface relief grating) that produces image light  22 ′and  22 ″. As another example, transmissive diffraction gratings  72  may include a first hologram (e.g., volume hologram) that diffracts image light  22  at wavelength ranges λ1 (as image light  22 ′) and λ1-Δλ (as image light  22 ″), a second hologram (e.g., volume hologram) that diffracts image light  22  at wavelength ranges λ2 (as image light  22 ′) and λ2-Δλ (as image light  22 ″), and a third hologram (e.g., volume hologram) that diffracts image light  22  at wavelength ranges λ3 (as image light  22 ′) and λ3-Δλ (as image light  22 ″). The first, second, and third holograms may be recorded in respective layers of grating medium or two or more of the holograms may share a single layer of grating medium (e.g., two or more of the holograms may be multiplexed or superimposed within the same volume of grating medium). As yet another example, transmissive diffraction gratings  72  may include a first hologram (e.g., volume hologram) that diffracts image light  22  at wavelength range λ1 (as image light  22 ′), a second hologram (e.g., volume hologram) that diffracts image light  22  at wavelength range and λ1- Δλ (as image light  22 ″), a third hologram (e.g., volume hologram) that diffracts image light  22  at wavelength range λ2 (as image light  22 ′), a fourth hologram (e.g., volume hologram) that diffracts image light  22  at wavelength range and λ2-Δλ (as image light  22 ″), a fifth hologram (e.g., volume hologram) that diffracts image light  22  at wavelength range λ3 (as image light  22 ′), and a sixth hologram (e.g., volume hologram) that diffracts image light  22  at wavelength range and λ3-Δλ (as image light  22 ″). Each of these holograms may be recorded in respective layers of grating medium or two or more of the holograms may share a single layer of grating medium (e.g., two or more of the holograms may be multiplexed or superimposed within the same volume of grating medium). If desired, the dispersive properties of the holograms may provide some or all of the angular separation between image light  22 ′ and  22 ″ in some or all of these scenarios. 
     The example of  FIG.  4    is merely illustrative. In general, first and second light sources  34 A may each include two light sources, one light source, or more than three light sources (e.g., for providing image light  22  within any desired number of color bands). Infrared, near-infrared, and/or ultraviolet light sources may be used. If desired, more than two sets of light sources may be used (e.g., three sets, four sets, more than four sets, etc.). In these scenarios, wavelength-separating input coupling structures  36  may divide image light  22  into a number of beams within waveguide  26  equal to the number of sets of light sources. Display module  14 A need not be a reflective display module. Transmissive diffraction gratings  72  of wavelength-separating input coupling structures  36  may be layered between prism  58  and surface  60  of waveguide  26  or may be embedded within waveguide  26  (e.g., at location  70 ). In scenarios where transmissive diffraction gratings  72  are formed at location  70 , the transmissive diffraction gratings may be recorded in one or more layers of grating media layered onto a transparent waveguide substrate or embedded between two layers of transparent waveguide substrate. One or more of the layers of grating media used to form transmissive diffraction gratings  72  may also be used to record holograms in cross-coupler  32  and/or output coupler  30  of  FIG.  2   , if desired. 
     The example of  FIG.  4    in which input coupler  28  includes prism  58  is merely illustrative. In another suitable arrangement, prism  58  may be omitted.  FIG.  5    is a diagram of optical system  14 B in an example where prism  58  is omitted. As shown in  FIG.  5   , transmissive diffraction gratings  72  may diffract image light  22  to produce a beam of image light  22 ′ and a beam of image light  22 ″ that are separated by separation angle θ1-θ2. The output angles of image light  22 ″ and image light  22 ′ from transmissive diffraction gratings  72  may be such that image light  22 ″ and image light  22 ′ propagate down the length of waveguide  26  via total internal reflection (e.g., wavelength-separating input coupling structures  36  may couple the image light into waveguide  26  as an input coupler). The example of  FIG.  5    is merely illustrative. If desired, transmissive diffraction gratings  72  of  FIG.  5    may be embedded within waveguide  26  (e.g., at location  70 ). 
     The examples of  FIGS.  4  and  5    in which wavelength-separating input coupling structures  36  include transmissive diffraction gratings is merely illustrative. In another suitable arrangement, wavelength-separating input coupling structures  36  may include reflective diffraction gratings.  FIG.  6    is a diagram showing how wavelength-separating input coupling structures  36  may include reflective diffraction gratings. 
     As shown in  FIG.  6   , wavelength-separating input coupling structures  36  may include reflective diffraction gratings  74  layered onto reflective surface  66  of prism  58 . Reflective diffraction gratings  74  may perform similar operations on incident image light  22  as described above in connection with transmissive diffraction gratings  72  of  FIGS.  4  and  5   , but where the output angles of the image light diffracted by wavelength-separating input coupling structures  36  are greater than 90 degrees with respect to the +Y direction (axis  68 ). Thus, as shown in  FIG.  6   , reflective diffraction gratings  74  may separate image light  22  into a beam of image light  22 ′ and a beam of image light  22 ″ that is separated from the beam of image light  22 ′ by separation angle θ1θ2. Image light  22 ′ and  22 ″ may then propagate down the length of waveguide  26  via total internal reflection. Reflective diffraction gratings  74  may include one, three, six, or any other desired number of reflective diffraction gratings (e.g., surface relief gratings, volume holograms, etc.) within a single layer of grating medium or distributed across two or more layers of grating medium layered over reflective surface  66  (e.g., similar to as described above in connection with transmissive diffraction gratings  72 ). In another suitable arrangement, prism  58  may be omitted. and reflective diffraction gratings  74  may be layered directly onto surface  60  of waveguide  26 . 
       FIG.  7    is an illustrative field angle sensitivity plot for diffraction gratings in wavelength-separating input coupling structures  36  (e.g., transmissive diffraction gratings  72  of  FIGS.  4  and  5    or reflective diffraction gratings  74  of  FIG.  6   ). The horizontal axis of  FIG.  7    plots input field angle for the light in degrees. The vertical axis of  FIG.  7    plots the separation angle θ1-θ2 produced by the diffraction gratings in arcmin. As shown by curve  76 , separation angle θ1-θ2 may reach a minimum between approximately −5 and 5 degrees. Curve  76  shows an example where wavelength offset Δλ is 10 nm and the grating pitch of the diffraction gratings is 35 microns. This is merely illustrative. In general, any desired wavelength offset and/or any desired grating pitch may be used. Curve  76  may have other shapes. 
     The examples of  FIGS.  4 - 6    in which wavelength-separating input coupling structures  36  include diffraction gratings is merely illustrative. In another suitable arrangement, wavelength-separating input coupling structures  36  may include a dichroic filter.  FIG.  8    is a diagram showing how wavelength-separating input coupling structures  36  may include a dichroic filter such as dichroic wedge  84 . 
     As shown in  FIG.  8   , dichroic wedge  84  may have a first surface  80  mounted to reflective surface  66  of prism  58 . Dichroic wedge  84  may have a second surface  82  opposite first surface  80 . Second surface  82  may be oriented at a non-parallel angle with respect to first surface  80 . First surface  80  may be provided with a coating or a set of coatings (e.g., at least one coating layered onto surface  80  or reflective surface  66  or otherwise interposed between surface  80  and reflective surface  66 ). The coating(s) may be configured to transmit light in wavelength ranges λ1, λ2 and λ3 as a beam of image light  22 ′. At the same time, the coating(s) may be configured to reflect light in wavelength ranges λ1-Δλ, λ2-Δλ, and λ3-Δλ as a beam of image light  22 ″. Image light  22 ′ may reflect off of surface  82  and back into waveguide  26 . Surfaces  82  and  80  may be oriented such that the image light  22 ′ reflected off of surface  82  is separated from the image light  22 ″ reflected off of surface  80  by separation angle θ1-θ2, If desired, an optional reflective coating may be provided on surface  82 . 
     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: 20210712
Publication Date: 20231226
Grant Date: 20231226
Priority Date: 20200713
Inventors: DELAPP, SCOTT M.
PENG, GUOLIN
CHOI, Hyungryul
BHAKTA, Vikrant
Assignee: APPLE INC
CPC Classifications: [{"code": "G02B27/0172", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B6/0016", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/0026", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/0031", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/34", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B2027/0147", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B2027/0174", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B2027/0178", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B27/0172", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B6/34", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/0026", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B2027/0147", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0016", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B2027/0178", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B2027/0174", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0031", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/0172", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B2027/0178", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B2027/0174", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B2027/0147", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0011", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 89383979