PATENT DOCUMENT

Publication Number: US-12019238-B2
Application Number: US-201716089006-A
Country: US
Kind Code: B2

Title: Optical systems for displays

Abstract:
An electronic device may include a display system for presenting images close to a user&#39;s eyes. The display system may include a display unit that directs light and an optical system that redirects the light from the display unit towards a user&#39;s eyes. The optical system may include an input coupler and an output coupler formed on a waveguide. The input coupler may redirect light from the display unit so that it propagates in the waveguide towards the output coupler. The output coupler may redirect the light from the input coupler so that it exits the waveguide towards the user&#39;s eyes. A light-redirecting element may be used to redirect edge light that would otherwise be outside of the user&#39;s field of view towards the user&#39;s eyes.

Claims:
What is claimed is: 
     
       1. A display system, comprising:
 a head-mounted support structure; 
 a display unit in the head-mounted support structure; 
 an optical system that receives light from the display unit and that redirects the light out of the optical system, wherein the optical system includes an input coupler, an output coupler, and a first waveguide that propagates the light along a first direction, wherein the input coupler couples the light into the first waveguide and the output coupler couples the light out of the first waveguide, and wherein the input coupler and the output coupler are located on the same side of the first waveguide; and 
 a light-redirecting element interposed between the display unit and the optical system, wherein the light-redirecting element includes a second waveguide that propagates the light along a second direction and includes an additional input coupler and an additional output coupler on the second waveguide, wherein the additional input coupler receives the light from the display unit and redirects the light towards the additional output coupler, wherein the additional output coupler receives the light from the additional input coupler and redirects the light towards the input coupler, and wherein the first direction is perpendicular to the second direction. 
 
     
     
       2. The display system defined in  claim 1  wherein the input coupler and the output coupler each include a holographic optical element. 
     
     
       3. The display system defined in  claim 1  wherein the input coupler receives the light from the light-redirecting element and redirects the light towards the output coupler. 
     
     
       4. The display system defined in  claim 3  wherein the output coupler receives the light from the input coupler and redirects the light out of the optical system. 
     
     
       5. The display system defined in  claim 1  wherein the additional input coupler and the additional output coupler each include a holographic optical element. 
     
     
       6. A display system, comprising:
 a head-mounted support structure; 
 a display unit in the head-mounted support structure; 
 an optical system that receives light from the display unit and that redirects the light out of the optical system, wherein the optical system includes a first input coupler, a first output coupler, and a waveguide, and wherein the first input coupler and the first output coupler are located on the same side of the waveguide; and 
 a light-redirecting element interposed between the input coupler and the output coupler, wherein the light-redirecting element includes a second input coupler and a second output coupler on the waveguide, and wherein the second input coupler receives the light from the first input coupler and the first output coupler receives the light from the second output coupler. 
 
     
     
       7. The display system defined in  claim 6  wherein the first and second input couplers and the first and second output couplers each comprise a holographic optical element. 
     
     
       8. The display system defined in  claim 6  wherein the waveguide propagates light from the first input coupler to the second input coupler along a first direction and wherein the waveguide propagates light from the second input coupler to the second output coupler along a second direction. 
     
     
       9. The display system defined in  claim 8  wherein the first direction is perpendicular to the second direction. 
     
     
       10. The display system defined in  claim 6  wherein the first input coupler has smaller dimensions than the first output coupler. 
     
     
       11. A display system, comprising:
 a head-mounted support structure; 
 a display unit in the head-mounted support structure; and 
 an optical system that receives light from the display unit and that redirects the light out of the optical system, wherein the optical system includes an input coupler, an output coupler, and a waveguide that propagates light from the input coupler to the output coupler, wherein the output coupler includes first and second non-parallel interference patterns, and wherein the input coupler and the output coupler are located on the same side of the waveguide. 
 
     
     
       12. The display system defined in  claim 11  wherein a thickness of the input and output couplers is greater than a thickness of the waveguide. 
     
     
       13. The display system defined in  claim 11  wherein the input and output couplers each comprise holographic optical elements. 
     
     
       14. The display system defined in  claim 13  wherein the holographic optical elements are color multiplexed. 
     
     
       15. The display system defined in  claim 11  wherein the first and second non-parallel interference patterns each have a modulated diffraction efficiency. 
     
     
       16. The display system defined in  claim 11  wherein the second interference pattern is located in an upper portion of the output coupler and a lower portion of the output coupler.

Description:
This application claims priority to U.S. provisional patent application No. 62/352,754, filed on Jun. 21, 2016, which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     This relates generally to optical systems and, more particularly, to optical systems for near-eye displays. 
     Electronic devices may include near-eye displays that present images close to a user&#39;s eyes. For example, devices such as virtual reality and augmented reality headsets may include near-eye displays with optical elements that allow users to view the displays. 
     It can be challenging to design devices such as these. If care is not taken, some of the field of view produced by a near-eye display may not be viewable from a single eye position. 
     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 include a display unit that directs light and an optical system that redirects the light from the display unit towards a user&#39;s eyes. The optical system may include an input coupler and an output coupler formed on a waveguide. The input coupler may redirect light from the display unit so that it propagates in the waveguide towards the output coupler. The output coupler may redirect the light from the input coupler so that it exits the waveguide towards the user&#39;s eyes. The input and output couplers may be formed from holographic optical elements such as thin holograms, volume holograms, or surface relief gratings. 
     A light-redirecting element may be used to redirect or redistribute light that would otherwise be outside of the user&#39;s field of view towards the user&#39;s eyes. The light-redirecting element may be interposed between the display unit and the input coupler, may be interposed between the input coupler and the output coupler, or may be integrated with the output coupler. 
     In arrangements where the light-redirecting element is interposed between the display unit and the input coupler, the light-redirecting element may include a secondary input coupler and a secondary output coupler on a second waveguide. 
     In arrangements where the light-redirecting element is interposed between the input coupler and the output coupler, the light-redirecting element may include a secondary input coupler and a secondary output coupler on the same waveguide as the primary input and output couplers. In other arrangements, the light-redirecting element may be formed from one holographic element (e.g., serving as both an input and output coupler) between the input coupler and the output coupler. 
     In arrangements where the light-redirecting element is integrated (e.g., multiplexed) with the output coupler, the light-redirecting element may include one or more interference patterns that are non-parallel with the interference patterns of the output coupler. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a diagram of an illustrative electronic device having a near-eye display system in accordance with an embodiment. 
         FIG.  2 A  is a top view of an illustrative near-eye display system having an optical system including an input coupler and an output coupler at least partially embedded in a waveguide substrate in accordance with an embodiment. 
         FIG.  2 B  is a top view of an illustrative near-eye display system having an optical system including an input coupler and an output coupler formed on a waveguide substrate in accordance with an embodiment. 
         FIG.  3    is a front view of an illustrative near-eye display system showing how optical interference patterns may be encoded in an input coupler and an output coupler in accordance with an embodiment. 
         FIG.  4    is a side view of an illustrative near-eye display system showing how light from a display may be emitted towards an optical system in accordance with an embodiment. 
         FIG.  5    is a side view of the near-eye display system of  FIG.  4    showing how the optical system may redirect light from the display towards a user&#39;s eye in accordance with an embodiment. 
         FIG.  6    is a side view of an illustrative near-eye display system that includes a light-redirecting element between a display and an input coupler in accordance with an embodiment. 
         FIG.  7    is a side view of the near-eye display system of  FIG.  6    showing how light that would otherwise be outside of the user&#39;s field of view has been redirected towards the user&#39;s field of view in accordance with an embodiment. 
         FIG.  8    is a front view of an illustrative near-eye display system that includes a light-redirecting element between an input coupler and an output coupler in accordance with an embodiment. 
         FIG.  9    is a front view of an illustrative near-eye display system that includes a light-redirecting element that spans a space between an input coupler and an output coupler in accordance with an embodiment. 
         FIG.  10    is a front view of an illustrative near-eye display system that includes a light-redirecting element integrated or multiplexed with an output coupler in accordance with an embodiment. 
         FIG.  11    is a front view of an illustrative output coupler having an integrated light-redirecting element at the center of the output coupler in accordance with an embodiment. 
         FIG.  12    is a front view of an illustrative output coupler having an integrated or multiplexed light-redirecting element that increases in size along a dimension of the output coupler in accordance with an embodiment. 
         FIG.  13    is a front view of an illustrative output coupler having an integrated light-redirecting element located throughout the output coupler in accordance with an embodiment. 
     
    
    
     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 display  20  mounted to support structure  12 . Support structure  12  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 display  20  on the head or near the eye of a user. Near-eye display  20  may include one or more display modules such as display  20 A and one or more optical systems such as optical system  20 B. Display module  20 A may be mounted in a support structure such as support structure  12 . Display module  20 A may emit light that is redirected towards a user&#39;s eye  16  using an associated optical system  20 B. If desired, system  10  may include two near-eye displays  20  (e.g., one for each of the user&#39;s eyes), each having a respective display module  20 A and optical system  20 B. 
     Display  20 A may be a liquid crystal display, an organic light-emitting diode display, or display of other types. Optical system  20 B may form a lens that allows a viewer (e.g., viewer&#39;s eye  16 ) to view images on display  20 . There may be two optical systems  20 B (e.g., for forming left and right lenses) associated with respective left and right eyes  16 . A single display  20  may produce images for one or both eyes  16 , or a pair of displays  20  may be used to display images for eyes  16 . As an example, displays  20  may include a left display module  20 A aligned with a left optical system  20 B and a viewer&#39;s left eye and may include a right display module  20 A aligned with a right optical system  20 B and a viewer&#39;s right eye. In configurations with multiple displays, the focal length and positions of the lenses formed by components  20 B may be selected so that any gap present between the displays will not be visible to a user (i.e., so that the images of the left and right displays overlap or merge seamlessly). 
     In configurations in which system  10  is a pair of virtual reality glasses, near-eye display  20  may obscure the user&#39;s view of the user&#39;s surrounding environment. In configurations in which system  10  is a pair of augmented reality glasses, display  20  may be transparent and/or display  20  may be provided with optical mixers such as half-silvered mirrors to allow viewer  16  to simultaneously view images on display  20  and external objects such as object  18  in the surrounding environment. 
     System  10  may include control circuitry  26 . Control circuitry  26  may include processing circuitry such as microprocessors, digital signal processors, microcontrollers, baseband processors, image processors, application-specific integrated circuits with processing circuitry, and/or other processing circuitry and may include random-access memory, read-only memory, flash storage, hard disk storage, and/or other storage (e.g., a non-transitory storage media for storing computer instructions for software that runs on control circuitry  26 ). 
     System  10  may include input-output circuitry such as touch sensors, buttons, microphones to gather voice input and other input, sensors, and other devices that gather input (e.g., user input from viewer  16 ) and may include light-emitting diodes, one or more displays  20 , speakers, and other devices for providing output (e.g., output for viewer  16 ). 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(s)  20  with image content). If desired, sensors such as an accelerometer, compass, an ambient light sensor or other light detector, a proximity sensor, a scanning laser system, an images sensor, and/or other sensors may be used in gathering input during operation of display  20 . During operation, control circuitry  26  may supply image content to display  20 . 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  26  (e.g., text, other computer-generated content, etc.). The content that is supplied to display  20  by control circuitry  26  may be viewed by viewer  16 . 
       FIG.  2    is a top view of an illustrative near-eye display  20  that may be used in system  10  of  FIG.  1   . As shown in  FIG.  2   , near-eye display  20  may include one or more display modules such as display module  20 A and an optical system such as optical system  20 B. Optical system  20 B may include optical elements such as waveguide  28 , input coupler  30 , and output coupler  32 . Display module  20 A may include a display unit  36  and a collimating lens  34 . If desired, display module  20 A may be mounted within support structure  12  of  FIG.  1    while optical system  20 B may be mounted between portions of support structure  12  (e.g., to form a lens that aligns with a user&#39;s eyes  16 ). Other mounting arrangements may be used, if desired. 
     Display unit  36  may be a display unit based on a liquid crystal display, organic light-emitting diode display, cathode ray tube, plasma display, projector display (e.g., a projector based on an array of micromirrors), liquid crystal on silicon display, or other suitable type of display. Display  36  may generate light  38  associated with three-dimensional content to be displayed to viewer  16 . Light  38  may be collimated using a lens such as collimating lens  34 . Optical system  20 B may be used to present light  38  output from display unit  36  to viewer  16 . 
     Optical system  20 B may include one or more couplers such as input coupler  30  and output coupler  32 . In the example of  FIG.  2 A , input coupler  30  and output coupler  32  are at least partially embedded in a waveguide structure such as waveguide  28  (e.g., a polymer, glass, or other transparent substrate capable of guiding light via total internal reflection). In the example of  FIG.  2 B , input coupler  30  and output coupler  32  are formed on an outer surface of waveguide  28 . 
     Input coupler  30  may be configured to couple light  38  from display unit  36  into waveguide  28 , whereas output coupler  32  may be configured to couple light  38  from within waveguide  28  to the exterior of waveguide  28  towards the user&#39;s eyes  16 . For example, display  36  may emit light  38  in direction Z towards optical system  20 B. When light  38  strikes input coupler  30 , input coupler  30  may redirect light  38  so that it propagates within waveguide  28  via total internal reflection towards output coupler  32  (e.g., in direction X). When light  38  strikes output coupler  32 , output coupler  32  may redirect light  38  out of waveguide  28  towards the viewer&#39;s eyes  16  (e.g., back along the Z-axis). 
     Input coupler  30  and output coupler  32  may be based on reflective and refractive optics or may be based on holographic (e.g., diffractive) optics. In arrangements where couplers  30  and  32  are formed from reflective and refractive optics, couplers  30  and  32  may include one or more reflectors (e.g., an array of micromirrors or other reflectors). In arrangements where couplers  30  and  32  are based on holographic optics, couplers  30  and  32  may include volume holographic media such as photopolymers, gelatin such as dichromated gelatin, silver halides, holographic polymer dispersed liquid crystal, or other suitable volume holographic media. 
     A holographic recording may be stored as an optical interference pattern (e.g., alternating regions of different indices of refraction) within the photosensitive optical material. The optical interference pattern may create a holographic grating that, when illuminated with a given light source, diffracts light to create a three-dimensional reconstruction of the holographic recording. The diffractive 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. 
     If desired, couplers  30  and  32  may have relatively large thicknesses compared to the thickness of waveguide  28 . For example, thickness T 1  of couplers  30  and  32  may be between 500 microns and 1000 microns, between 200 microns and 800 microns, greater than 1000 microns, or other suitable thickness, whereas the thickness T 2  of waveguide  28  may be between 100 microns and 500 microns, between 200 microns and 300 microns, between 1 mm and 2 mm, less than 3 mm, greater than 3 mm, or other suitable thickness. In arrangements where couplers  30  and  32  are formed on the surface of waveguide  28  as shown in  FIG.  2 B  (e.g., as opposed to being embedded in waveguide  28  as shown in  FIG.  2 A ), thickness T 1  of couplers  30  and  32  may be greater than thickness T 2  of waveguide  28 , if desired. This is, however, merely illustrative. If desired, couplers  30  and  32  may be relatively thin (e.g., 50 microns) and waveguide  28  may be relatively thick (e.g., 500 microns). 
     Using thick films for couplers  30  and  32  may help increase uniformity in the output image and may provide more material in which to record different optical functions. With thicker couplers, for example, more material is available for recording different interference patterns (e.g., a first interference pattern with a first optical function may be recorded at one depth within the coupler, a second interference pattern with a second optical function may be recorded at another depth within the coupler, etc.). One optical function recorded in coupler  30 , for example, may redirect light having a given input angle to a first output angle (e.g., 45°), whereas another optical function recorded in coupler  30  may redirect light having a given input angle to a second output angle (e.g., 60°). 
     Couplers  30  and  32  may, if desired, be multiplex holograms (e.g., three-color holograms such as red-green-blue holograms) for forming color three-dimensional images. The diffraction efficiency in each coupler  30  and  32  may be modulated (e.g., may vary across the width of couplers  30  and  32 ) so that light exits each coupler in a smooth, uniform manner. For example, the diffraction efficiency may be higher for areas that are further from the light source (e.g., the diffraction efficiency in a region of coupler  30  or  32  that is closer to display unit  36  may be 10%, while the diffraction efficiency in a region of coupler  30  or  32  that is further from display unit  36  may be 70%, as an example). 
       FIG.  3    is a front view of an illustrative optical system  20 B that may be used in near-eye display system  20 . In the example of  FIG.  3   , input coupler  30  is somewhat smaller than output coupler  32 . Input coupler  30  may, for example, have a width W 1  of about 16 mm and a length L 1  of about 32 mm, whereas output coupler  32  may have a width W 2  of about 37 mm and a length of about 26 mm. The distance D between the center of input coupler  30  and the center of output coupler  32  may be about 45 mm or other suitable distance. These dimensions are merely illustrative, however. Other dimensions may be used, if desired (e.g., input coupler  30  may be the same size as or bigger than output coupler  32 ). 
     As shown in  FIG.  3   , input coupler  30  has one or more optical interference patterns  40  and output coupler  32  has one or more optical interference patterns  42 . Each optical interference pattern may redirect incident light  38  according to an associated optical function. In the example of  FIG.  3   , interference patterns  40  and  42  are formed from vertical strips (e.g., strips parallel to the Y-axis of  FIG.  3   ) of alternating indices of refraction. This forms a diffraction grating that redirects incoming light at a desired angle. 
       FIGS.  4  and  5    are side views of an illustrative near-eye display  20  showing how an optical system  20 B of the type shown in  FIG.  3    may redirect light towards a user&#39;s eyes  16 .  FIG.  4    shows how light is input into optical system  20 B, and  FIG.  5    shows how light may exit optical system  20 B. As shown in  FIG.  4   , display unit  36  may emit light  38  towards optical system  20 B. Collimating lens  34  may collimate light  38  to focus light  38  onto optical system  20 B. Light  38  traveling from collimator  34  to system  20 B can be represented by a vector having an X-component (parallel to the X-axis), a Y-component (parallel to the Y-axis) and a Z-component (parallel to the Z-axis). 
     Interference patterns  40  in input coupler  30  may redirect incoming light  38  so that it propagates along the X-axis in waveguide  28  towards output coupler  32 . Interference patterns  42  in output coupler  32  may redirect incoming light  38  so that it stops propagating in the X-direction and instead exits waveguide  28  in direction Z (as shown in  FIG.  5   ). 
     If care is not taken, some of light  38  may be outside of the field of view of viewer&#39;s eye  16 . For example, some light rays such as edge light ray  38 ′ may not reach user&#39;s eye  16 . This is because vertical-strip interference patterns  40  and  42  of  FIG.  3    alter the X-component of incident light  38  (e.g., so that light  38  propagates in direction X towards output coupler  32 ) but do not alter the Y-component of incident light  38 . Thus, light rays  38  that exit output coupler  32  from top portion  50 T and bottom portion  50 B of output coupler  32  may pass over or under the user&#39;s field of view. 
     To minimize the amount of light  38  that is outside of the user&#39;s field of view, near-eye display system  20  may include a light-redirecting element that redirects edge light (e.g., light  38 ′ of  FIG.  4   ) to a different location so that it is within the field of view of the user.  FIGS.  6  and  7    illustrate an example in which a light-redirecting element  48  is located in front of input coupler  30  (e.g., between display  36  and input coupler  30 );  FIGS.  8  and  9    illustrate examples in which light-redirecting element  48  is located between input coupler  30  and output coupler  32 ; and  FIGS.  10 - 13    illustrate examples in which light-redirecting element  48  is integrated with output coupler  32 . If desired, embodiments that employ a combination of features shown in  FIGS.  1 - 13    may be used. For example, light-redirecting elements may be located in more than one location (e.g., a first light-redirecting element may be located between input coupler  30  and output coupler  32  and a second light-redirecting element may be integrated with output coupler  32 ). 
     Light-redirecting element  48  may, if desired, include multiplex holograms (e.g., three-color holograms such as red-green-blue holograms) for forming color three-dimensional images. The diffraction efficiency in light-redirecting element  48  may be modulated (e.g., may vary across the width of light-redirecting element  48  so that light exits light-redirecting element  48  in a smooth, uniform manner. For example, the diffraction efficiency may be higher for areas that are further from the light source (e.g., the diffraction efficiency in a region of light-redirecting element  48  that is closer to display unit  36  may be 10%, while the diffraction efficiency in a region of coupler light-redirecting element  48  that is further from display unit  36  may be 70%, as an example). 
     As shown in  FIG.  6   , light-redirecting element  48  may include an input coupler  52  and output coupler  54  formed on a waveguide such as waveguide  46 . Light-redirecting element  48  may be attached to optical system  20 B or may be mounted to other structures in display  20 . Light-redirecting element  48  may operate similarly to optical system  20 B. For example, couplers  52  and  54  may be holographic optical elements with encoded interference patterns that redirect incident light according to a given optical function. However, rather than propagating light in the X-direction, as in optical system  20 B, light-redirecting element  48  may be used to propagate light along the Y-direction (e.g., from input coupler  52  to output coupler  54 ). 
     For example, input coupler  52  may have one or more interference patterns that redirects edge light  38 ′ from display module  20 A so that it propagates in waveguide  46  in direction Y via total internal reflection towards output coupler  54 . Output coupler  54  may redirect light  38 ′ so that it exits element  48  towards optical system  20 B. Rather than striking top portion  56 T of input coupler  30  (as indicated by dashed line  44 ), light  38 ′ is emitted towards bottom portion  56 B of input coupler  30 . Thus, when light  38 ′ exits output coupler  32 , as shown in  FIG.  7   , it will exit from bottom portion  50 B of output coupler  32  towards user&#39;s eye  16  (as opposed to exiting from top portion  50 T of output coupler  32  as indicated by arrow  44 ). 
     The example of  FIG.  6    in which input coupler  52  and output coupler  54  are embedded in waveguide  46  is merely illustrative. If desired, couplers  52  and  54  may be attached to an outer surface of waveguide  46  (e.g., both on the front surface of waveguide  46  facing display unit  36 , both on the rear surface of waveguide  46  facing waveguide  28 , or one on the front surface of waveguide  46  and the other on the rear surface of waveguide  46 ). 
     In the example of  FIG.  8   , light-redirecting element  48  may be interposed between input coupler  30  and output coupler  32 . Rather than being mounted on a separate waveguide, as in the example of  FIG.  6   , input coupler  52  and output coupler  54  of light-redirecting element  48  are formed on or in waveguide  28  between input coupler  30  and output coupler  32 . 
     Input coupler  30  may redirect edge light  38 ′ so that it propagates in the X-direction towards input coupler  52 . Input coupler  52  may have one or more interference patterns that redirects edge light  38 ′ from input coupler  30  so that it propagates in waveguide  28  in direction Y via total internal reflection towards output coupler  54 . Output coupler  54  may have one or more interference patterns that redirects light  38 ′ so that it propagates in the X-direction towards output coupler  32 . Output coupler  32  may redirect the light from output coupler  54  so that it exits waveguide  28  towards the user&#39;s eyes  16  (as opposed to exiting from top portion  50 T of output coupler  32  as indicated by arrow  44 ). 
       FIG.  9    shows another example in which light-redirecting element  48  is interposed between input coupler  30  and output coupler  32 . In this example, light-redirecting element  48  is formed from a film having a length L 3  that is larger than the length L 2  of output coupler  32 . Light-redirecting element  48  has interference patterns  62  which are non-parallel to the Y-axis. Interference patterns  62  may be configured to redirect the Y-component of light  38 ′ so that light  38 ′ is directed towards the user&#39;s eyes  16 . For example, as illustrated in  FIG.  9   , interference pattern  62  in top portion  48 T of light-redirecting element  48  may redirect the Y-component of edge light  38 ′ that strikes top portion  48 T downward in the Y-direction towards interference pattern  62  in bottom portion  48 B of light-redirecting element  48 , which may in turn redirect the Y-component of edge light  38 ′ upward towards output coupler  32 . Similarly, interference pattern  62  in bottom portion  48 B of light-redirecting element  48  may redirect the Y-component of edge light  38 ′ that strikes bottom portion  48 B upward in the Y-direction towards interference pattern  62  in top portion  48 T of light-redirecting element  48 , which may in turn redirect the Y-component of edge light  38 ′ downward towards output coupler  32 . Output coupler  32  may redirect the light from light-redirecting element  48  so that it exits waveguide  28  towards the user&#39;s eyes  16 . 
     In the example of  FIG.  10   , one or more light-redirecting elements  48  may be integrated into output coupler  32 . Light-redirecting elements  48  of  FIG.  10    may include optical interference patterns that are encoded in coupler  32 . Thus, coupler  32  includes not only vertical strips of interference patterns  42  parallel to the Y-axis, but also interference patterns  58  which are non-parallel to the Y-axis. Interference patterns  58  may be configured to redirect the Y-component of light  38 ′ so that light  38 ′ is directed towards the user&#39;s eyes  16 . For example, interference pattern  58  in top portion  50 T of output coupler  32  may redirect the Y-component of edge light  38 ′ that strikes top portion  50 T downward in the Y-direction towards eye level  60 , whereas interference pattern  58  in bottom portion  50 B of output coupler  32  may redirect the Y-component of edge light  38 ′ that strikes bottom portion  50 B upward in the Y-direction towards eye level  60 . 
     The example of  FIG.  10    in which interference patterns  58  are only located in top portion  50 T and bottom portion  50 B of output coupler  50  is merely illustrative. If desired, interference patterns  58  may be encoded at center portion  50 C of output coupler  32 , as shown in the example of  FIG.  11   . In the example of  FIG.  12   , interference patterns  58  are encoded at center portion  50 C of output coupler  32  and increase in size along the X-direction (e.g., from size P 1  to size P 2 ). This may help ensure that light is diffracted from output coupler  32  in a smooth, uniform manner. In the example of  FIG.  13   , interference patterns  58  are encoded throughout output coupler  32 . These examples are merely illustrative, however. If desired, interference patterns  58  may be encoded in output coupler  32  in other suitable locations, sizes, patterns, etc. Arrangements in which light-redirecting element  48  is integrated with input coupler  30  (e.g., by encoding interference patterns that are non-parallel with the Y-axis) may also be used. 
     In accordance with an embodiment, a display system is provided that includes a display unit, an optical system that receives light from the display unit and that redirects the light out of the optical system, the optical system includes an input coupler, an output coupler, and a first waveguide that propagates light along a first direction, and a light-redirecting element interposed between the display unit and the optical system, the light-redirecting element includes a second waveguide that propagates light along a second direction. 
     In accordance with another embodiment, the input coupler and the output coupler each include a holographic optical element. 
     In accordance with another embodiment, the input coupler receives the light from the light-redirecting element and redirects the light towards the output coupler. 
     In accordance with another embodiment, the output coupler receives the light from the input coupler and redirects the light out of the optical system. 
     In accordance with another embodiment, light-redirecting element includes an additional input coupler and an additional output coupler on the second waveguide. 
     In accordance with another embodiment, the additional input coupler and the additional output coupler each include a holographic optical element. 
     In accordance with another embodiment, the additional input coupler receives the light from the display unit and redirects the light towards the additional output coupler. 
     In accordance with another embodiment, the additional output coupler receives the light from the additional input coupler and redirects the light towards the input coupler. 
     In accordance with another embodiment, the first direction is perpendicular to the second direction. 
     In accordance with an embodiment, a display system is provided that includes a display unit, an optical system that receives light from the display unit and that redirects the light out of the optical system, where the optical system includes a first input coupler, a first output coupler, and a waveguide and a light-redirecting element interposed between the input coupler and the output coupler, where the light-redirecting element includes a second input coupler and a second output coupler on the waveguide, and the second input coupler receives the light from the first input coupler and the first output coupler receives the light from the second output coupler. 
     In accordance with another embodiment, the first and second input couplers and the first and second output couplers each include a holographic optical element. 
     In accordance with another embodiment, the waveguide propagates light from the first input coupler to the second input coupler along a first direction and the waveguide propagates light from the second input coupler to the second output coupler along a second direction. 
     In accordance with another embodiment, the first direction is perpendicular to the second direction. 
     In accordance with another embodiment, the first input coupler has smaller dimensions than the first output coupler. 
     In accordance with an embodiment, a display system is provided that includes a display unit, and an optical system that receives light from the display unit and that redirects the light out of the optical system, where the optical system includes an input coupler, an output coupler, and a waveguide that propagates light from the input coupler to the output coupler, and the output coupler includes first and second non-parallel interference patterns. 
     In accordance with another embodiment, a thickness of the input and output couplers is greater than a thickness of the waveguide. 
     In accordance with another embodiment, the input and output couplers each includes holographic optical elements. 
     In accordance with another embodiment, the holographic optical elements are color multiplexed. 
     In accordance with another embodiment, the first and second interference patterns each have a modulated diffraction efficiency. 
     In accordance with another embodiment, the second interference pattern is located in an upper portion of the output coupler and a lower portion of the output coupler. 
     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: 20170606
Publication Date: 20240625
Grant Date: 20240625
Priority Date: 20160621
Inventors: MYHRE, GRAHAM B.
HANSOTTE, Eric J.
PENG, GUOLIN
CHOI, Hyungryul
OH, SE BAEK
GELSINGER-AUSTIN, Paul
Assignee: APPLE INC
CPC Classifications: [{"code": "G02B2027/0174", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B2027/0178", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B2027/0123", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0035", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/017", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/0023", "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": "G02B2027/0123", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0035", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/0023", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B2027/0178", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B2027/0123", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B2027/0178", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B2027/0123", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B27/0172", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B27/0172", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B27/017", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B2027/0178", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B2027/0174", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B2027/0123", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0035", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/0023", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/0172", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 59071116