PATENT DOCUMENT

Publication Number: US-11762197-B2
Application Number: US-202016935083-A
Country: US
Kind Code: B2

Title: Display systems with geometrical phase lenses

Abstract:
An electronic device such as a head-mounted device may have a display that produces a display image. The head-mounted device may have an optical system that merges real-world images from real-world objects with display images. The optical system provides the real-world images and display images to an eye box for viewing by a user. The optical system may use time interleaving techniques and/or polarization effects to merge real-world and display images. Switchable devices such as polarization switches and tunable lenses may be controlled in synchronization with frames of display images. Geometrical phase lenses may be used that exhibit different lens powers to different polarizations of light.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a display configured to provide a display image; 
 a waveguide having an output coupler through which a real-world image from a real-world object is viewable from an eye box, wherein the waveguide is configured to receive the display image from the display and wherein the output coupler is configured to couple the display image out of the waveguide towards the eye box; and 
 first and second geometrical phase lenses that are each configured to exhibit different lens powers under different circular light polarizations, wherein the first geometrical phase lens is between the output coupler and the eye box and wherein the output coupler is between the second geometrical phase lens and the first geometrical phase lens. 
 
     
     
       2. The electronic device defined in  claim 1  further comprising first and second polarization switches and a linear polarizer, wherein the output coupler and the linear polarizer are between the first and second polarization switches and wherein the linear polarizer is between the output coupler and the first polarization switch. 
     
     
       3. The electronic device defined in  claim 2  wherein the first and second polarization switches are configured to operate in:
 a first state in which the display image passes through the first geometrical phase lens with a first circular polarization; and 
 a second state in which the display image passes through the first geometrical phase lens with a second circular polarization that is different than the first circular polarization. 
 
     
     
       4. The electronic device defined in  claim 3  wherein the first geometrical phase lens is configured to exhibit a positive lens power for the display image passing through the first geometrical phase lens with the first circular polarization. 
     
     
       5. The electronic device defined in  claim 4  wherein the first geometrical phase lens is configured to exhibit a negative lens power for the display image passing through the first geometrical phase lens with the second circular polarization. 
     
     
       6. The electronic device defined in  claim 5  wherein the first geometrical phase lens is configured to:
 pass the real-world image to the eye box with a positive lens power when the first geometrical phase lens receives the real-world image with the first circular polarization; and 
 pass the real-world image to the eye box with a negative lens power when the first geometrical phase lens receives the real-world image with the second circular polarization. 
 
     
     
       7. The electronic device defined in  claim 6  wherein the second geometrical phase lens is configured to:
 exhibit a negative lens power to the real-world image that is passing through the first geometrical phase lens with the positive lens power; and 
 exhibit a positive lens power to the real-world image that is passing through the first geometrical phase lens with the negative lens power. 
 
     
     
       8. The electronic device defined in  claim 7  further comprising:
 a first quarter wave plate between the first polarization switch and the first geometrical phase lens; and 
 a second quarter wave plate between the second geometrical phase lens and the second polarization switch. 
 
     
     
       9. The electronic device defined in  claim 8  wherein the first polarization switch comprises a first electrically adjustable liquid crystal polarization rotator and wherein the second polarization switch comprises a second electrically adjustable liquid crystal polarization rotator. 
     
     
       10. The electronic device defined in  claim 1  further comprising a polarization switch and a linear polarizer, wherein the polarization switch is between the first geometrical phase lens and the linear polarizer and wherein the linear polarizer is between the polarization switch and the eye box. 
     
     
       11. The electronic device defined in  claim 10  further comprising a quarter wave plate between the first geometrical phase lens and the polarization switch. 
     
     
       12. The electronic device defined in  claim 11  wherein the polarization switch is configured to operate in:
 a first state while the display image passes through the first geometrical phase lens with a first circular polarization; and 
 a second state while the display image passes through the first geometrical phase lens with a second circular polarization that is different than the first circular polarization. 
 
     
     
       13. The electronic device defined in  claim 12  wherein the first geometrical phase lens is configured to exhibit a negative lens power for the display image passing through the first geometrical phase lens with the first circular polarization and is configured to exhibit a positive lens power for the display image passing through the first geometrical phase lens with the second circular polarization. 
     
     
       14. The electronic device defined in  claim 13  wherein the first geometrical phase lens is configured to:
 pass the real-world image to the eye box with a negative lens power when the first geometrical phase lens receives the real-world image with the first circular polarization; and 
 pass the real-world image to the eye box with a positive lens power when the first geometrical phase lens receives the real-world image with the second circular polarization. 
 
     
     
       15. The electronic device defined in  claim 14  wherein the second geometrical phase lens is configured to:
 exhibit a positive lens power to the real-world image that is passing through the first geometrical phase lens with the negative lens power; and 
 exhibit a negative lens power to the real-world image that is passing through the first geometrical phase lens with the positive lens power. 
 
     
     
       16. The electronic device defined in  claim 1  further comprising first and second polarization switches and first and second linear polarizers, wherein the first linear polarizer is between the first polarization switch and the eye box, wherein the first polarization switch is between the first linear polarizer and the first geometrical phase lens, wherein the second polarization switch is between the second linear polarizer and the second geometrical phase lens, and wherein the first and second polarization switches operate synchronously in:
 a first state while the display image passes through the first geometrical phase lens with a first circular polarization; and 
 a second state while the display image passes through the first geometrical phase lens with a second circular polarization that is different than the first circular polarization. 
 
     
     
       17. An electronic device, comprising:
 a display configured to operate alternately in first and second states, wherein the display is configured to provide a display image when operated in the second state and to provide no display image when operated in the first state; 
 a waveguide having an output coupler through which a real-world image from a real-world object is viewable from an eye box, wherein the waveguide is configured to receive the display image from the display and wherein the output coupler is configured to couple the display image out of the waveguide towards the eye box; and 
 first and second geometrical phase lenses that are each configured to exhibit different lens powers under different circular light polarizations, wherein the first and second geometrical phase lenses are between the output coupler and the eye box. 
 
     
     
       18. The electronic device defined in  claim 17  further comprising a polarization switch between the first and second geometrical phase lenses wherein the polarization switch is configured to be turned on during the second state. 
     
     
       19. The electronic device defined in  claim 18  further comprising a linear polarizer between the output coupler and the first geometrical phase lens and a quarter wave plate between the linear polarizer and the first geometrical phase lens. 
     
     
       20. A head-mounted device, comprising:
 a display configured to operate alternately in first and second states, wherein the display is configured to provide a display image of a first polarization state when operated in the first state and to provide a display image of a second polarization state that is different than the first polarization state when operated in the second state; 
 a waveguide having an output coupler through which a real-world image from a real-world object is viewable from an eye box, wherein the waveguide is configured to receive the display images of the first and second polarization states from the display and wherein the output coupler is configured to couple the display images of the first and second polarization states out of the waveguide towards the eye box; and 
 a geometrical phase lens interposed between the output coupler and the eye box, wherein the geometrical phase lens exhibits a positive lens power as the display image of the first polarization state passes through the geometrical phase lens and exhibits a negative lens power as the display image of the second polarization state passes through the geometrical phase lens. 
 
     
     
       21. The head-mounted device defined in  claim 20  further comprising a lens with a fixed negative lens power between the geometrical phase lens and the eye box.

Description:
This application claims the benefit of provisional patent application No. 62/886,172, filed Aug. 13, 2019, which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     This relates generally to electronic devices and, more particularly, to electronic devices with optical systems for merging display content and real-world content. 
     Electronic devices sometimes include displays. For example, wearable electronic devices such as head-mounted devices may include displays for displaying computer-generated content that is overlaid on real-world content. An optical system is used to merge real-world content and display content. 
     Challenges can arise in providing satisfactory optical systems for merging real-world and display content. If care is not taken, issues may arise with optical quality and other performance characteristics. 
     SUMMARY 
     An electronic device such as a head-mounted device may have a display that produces a display image. The head-mounted device may have an optical system through which a user with eyes in eye boxes may view real-world objects. During operation, the optical system may be used to merge real-world images from real-world objects with display images. 
     A display may produce images in frames. Different objects may be displayed in alternating image frames. The optical system may be adjusted in synchronization with the alternating image frames to display the different objects at different focal planes. 
     In some configurations, the optical system may have an intensity switch formed from a pair of linear polarizers and an interposed polarization switch. The polarization switch may be operated in a first state in which linearly polarized light of a given polarization is not rotated by the polarization switch and a second state in which the linearly polarized light of the given polarization is rotated by 90°. 
     Additional components may be incorporated in the optical system such as front and rear bias lenses with complementary lens powers, a polarization switch for helping to merge real-world images and display images in a time interleaved fashion, and geometrical phase lenses that present different lens powers to images with different polarizations. Tunable lenses may be used to place display images at different respective focal plane distances from the eye boxes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram of an illustrative electronic device such as a head-mounted display device in accordance with an embodiment. 
         FIG.  2    is a top view of an illustrative head-mounted device in accordance with an embodiment. 
         FIGS.  3 A and  3 B  are cross-sectional views of illustrative optical systems with time interleaving and tunable lenses in accordance with embodiments. 
         FIGS.  4 A,  4 B,  5 A,  5 B, and  6 - 9    are cross-sectional side views of illustrative optical systems with geometrical phase lenses in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices may include displays and other components for presenting content to users. The electronic devices may be wearable electronic devices. A wearable electronic device such as a head-mounted device may have head-mounted support structures that allow the head-mounted device to be worn on a user&#39;s head. 
     A head-mounted device may contain a display for displaying visual content to a user. The head-mounted device may also include an optical system that helps a user view real-world objects while viewing display content. The optical system may include optical components that merge real-world image light with image light associated with images that are displayed by the display. When both real-world image light and display image light are visible to a user, the head-mounted device may place computer-generated objects within the physical environment surrounding a user. 
     Real-world content may be merged with display content using time-division multiplexing, polarization multiplexing, and/or other arrangements for combining light from real-world objects with light from displays. 
     A schematic diagram of an illustrative system that may include head-mounted device with an optical system for merging real-world content with display content is shown in  FIG.  1   . As shown in  FIG.  1   , system  8  may include one or more electronic devices such as electronic device  10 . The electronic devices of system  8  may include computers, cellular telephones, head-mounted devices, wristwatch devices, and other electronic devices. Configurations in which electronic device  10  is a head-mounted device are sometimes described herein as an example. 
     As shown in  FIG.  1   , electronic devices such as electronic device  10  may have control circuitry  12 . Control circuitry  12  may include storage and processing circuitry for controlling the operation of device  10 . Circuitry  12  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  12  may be based on one or more mnicroprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio chips, graphics processing units, application specific integrated circuits, and other integrated circuits. Software code may be stored on storage in circuitry  12  and run on processing circuitry in circuitry  12  to implement control operations for device  10  (e.g., data gathering operations, operations involving the adjustment of the components of device  10  using control signals, etc.). Control circuitry  12  may include wired and wireless communications circuitry. For example, control circuitry  12  may include radio-frequency transceiver circuitry such as cellular telephone transceiver circuitry, wireless local area network (WiFi®) transceiver circuitry, millimeter wave transceiver circuitry, and/or other wireless communications circuitry. 
     During operation, the communications circuitry of the devices in system  8  (e.g., the communications circuitry of control circuitry  12  of device  10 ) may be used to support communication between the electronic devices. For example, one electronic device may transmit video and/or audio data to another electronic device in system  8 . Electronic devices in system  8  may use wired and/or wireless communications circuitry to communicate through one or more communications networks (e.g., the internet, local area networks, etc.). The communications circuitry may be used to allow data to be received by device  10  from external equipment (e.g., a tethered computer, a portable device such as a handheld device or laptop computer, online computing equipment such as a remote server or other remote computing equipment, or other electrical equipment) and/or to provide data to external equipment. 
     Device  10  may include input-output devices  22 . Input-output devices  22  may be used to allow a user to provide device  10  with user input. Input-output devices  22  may also be used to gather information on the environment in which device  10  is operating. Output components in devices  22  may allow device  10  to provide a user with output and may be used to communicate with external electrical equipment. 
     As shown in  FIG.  1   , input-output devices  22  may include one or more displays such as display(s)  14 . In some configurations, display  14  of device  10  includes left and right display devices (e.g., left and right components such as left and right scanning mirror display devices, liquid-crystal-on-silicon display devices, digital mirror devices, or other reflective display devices, left and right display panels based on light-emitting diode pixel arrays (e.g., organic light-emitting display panels or display devices based on pixel arrays formed from crystalline semiconductor light-emitting diode dies), liquid crystal display panels, and/or or other left and right display devices in alignment with the user&#39;s left and right eyes, respectively. In other configurations, display  14  includes a single display panel that extends across both eyes or uses other arrangements in which content is provided with a single pixel array. 
     Display  14  is used to display visual content for a user of device  10 . The content that is presented on display  14  may include virtual objects and other content that is provided to display  14  by control circuitry  12  and may sometimes be referred to as computer-generated content, display content, display images, display light, etc. Computer-generated content may be displayed in the absence of real-world content or may be combined with real-world content. In some configurations, a real-world image may be captured by a camera (e.g., a forward-facing camera) so that computer-generated content may be electronically overlaid on portions of the real-world image (e.g., when device  10  is a pair of virtual reality goggles with an opaque display). In other configurations, an optical system (e.g., an optical coupling system) may be used to allow computer-generated content to be optically overlaid on top of a real-world image. As an example, device  10  may have a see-through display system that provides a computer-generated image to a user through a beam splitter, prism, holographic coupler, or other optical coupler while allowing the user to view real-world objects through the optical coupler. 
     Input-output circuitry  22  may include sensors  16 . Sensors  16  may include, for example, three-dimensional sensors (e.g., three-dimensional image sensors such as structured light sensors that emit beams of light and that use two-dimensional digital image sensors to gather image data for three-dimensional images from light spots that are produced when a target is illuminated by the beams of light, binocular three-dimensional image sensors that gather three-dimensional images using two or more cameras in a binocular imaging arrangement, three-dimensional lidar (light detection and ranging) sensors, three-dimensional radio-frequency sensors, or other sensors that gather three-dimensional image data), cameras (e.g., infrared and/or visible digital image sensors), gaze tracking sensors (e.g., a gaze tracking system based on an image sensor and, if desired, a light source that emits one or more beams of light that are tracked using the image sensor after reflecting from a user&#39;s eyes), touch sensors, buttons, capacitive proximity sensors, light-based (optical) proximity sensors, other proximity sensors, force sensors, sensors such as contact sensors based on switches, gas sensors, pressure sensors, moisture sensors, magnetic sensors, audio sensors (microphones), ambient light sensors, microphones for gathering voice commands and other audio input, sensors that are configured to gather information on motion, position, and/or orientation (e.g., accelerometers, gyroscopes, compasses, and/or inertial measurement units that include all of these sensors or a subset of one or two of these sensors), radio-frequency sensors that determine the location of other devices (and therefore the relative position of such devices relative to device  10 ), and/or other sensors. 
     User input and other information may be gathered using sensors and other input devices in input-output devices  22 . If desired, input-output devices  22  may include other devices  24  such as haptic output devices (e.g., vibrating components), light-emitting diodes and other light sources, speakers such as ear speakers for producing audio output, and other electrical components. Devices  24  may include one or more adjustable optical components such as liquid crystal devices or other electrically adjustable optical components. These components may form polarization switches. Polarization switches, which may sometimes be referred to as electrically tunable wave plates or electrically controllable polarization rotators, may be adjusted to rotate linearly polarized light by different amounts (e.g., 0° or 90° depending on the state of the switch). If desired, a polarization switch may be used with a pair of polarizers to form an electrically adjustable shutter (sometimes referred to as a light modulator or intensity switch). If desired, devices  24  may include tunable lenses. Tunable lenses may be formed from liquid crystal devices and other electrically adjustable devices. Tunable lenses may be adjusted to produce different lens powers (e.g., desired positive and/or negative lens powers) and/or to adjust the lateral location of the lens center (e.g., to accommodate different user gaze directions). For example, tunable lenses can be adjusted to move the position of the centers of the lenses based on information gathered in real time from a gaze detection system. 
     If desired, device  10  may include circuits for receiving wireless power, circuits for transmitting power wirelessly to other devices, batteries and other energy storage devices (e.g., capacitors), joysticks, buttons, and/or other components. 
     Electronic device  10  may have housing structures (e.g., housing walls, straps, etc.), as shown by illustrative support structures  26  of  FIG.  1   . In configurations in which electronic device  10  is a head-mounted device (e.g., a pair of glasses, goggles, a helmet, a hat, etc.), support structures  26  may include head-mounted support structures (e.g., a helmet housing, head straps, temples in a pair of eyeglasses, goggle housing structures, and/or other head-mounted structures). The head-mounted support structures may be configured to be worn on a head of a user during operation of device  10  and may support display(s)  14 , sensors  16 , other components  24 , other input-output devices  22 , and control circuitry  12 . 
       FIG.  2    is a top view of electronic device  10  in an illustrative configuration in which electronic device  10  is a head-mounted device. As shown in  FIG.  2   , electronic device  10  may include support structures  26  that are used in housing the components of device  10  and mounting device  10  onto a user&#39;s head. These support structures may include, for example, structures that form housing walls and other structures for a main unit (e.g., support structures  26 - 2 ) and additional structures such as straps, temples, or other supplemental support structures (e.g., support structures  26 - 1 ) that help to hold the main unit and the components in the main unit on a user&#39;s face so that the user&#39;s eyes are located within eye boxes  60 . 
     Display  14  may include left and right display portions (e.g., sometimes referred to as left and right displays, left and right display devices, left and right display components, or left and right pixel arrays). An optical system for device  10  may be formed from couplers  84  (sometimes referred to as input couplers), waveguides  86 , and an optical system formed from one or more optical components such as components  100  and  102 . Components  100  may be interposed between the front (outwardly facing) side of device  10  and waveguides  86  (e.g., between real-world object  90  and waveguides  86 ). Components  102  may be interposed between waveguides  86  and the rear (inwardly facing) side of device  10  (e.g., between waveguides  86  and eye boxes  60 . Components  100  and  102  may include fixed and/or adjustable components that help place computer-generated content at a desired focal plane and that help merge this content with real-world image light that is passing through components  10  and  102  and waveguide  86  to eye boxes  60 . A user with eyes located in eye boxes  60  may view real-world objects through the optical system formed from components  100 , waveguide  86 , and components  102  and other components of device  10  while viewing overlaid computer-generated content from display  14 . 
     As shown in  FIG.  2   , the left portion of display  14  may be used to create an image for a left-hand eye box  60  (e.g., a location where a left-hand image is viewed by a user&#39;s left eye). The right portion of display  14  may be used to create an image for a right-hand eye box  60  (e.g., a location where a right-hand image is viewed by a user&#39;s right eye). In the configuration of  FIG.  2   , the left and right portions of display  14  may be formed by respective left and right display devices (e.g., digital mirror devices, liquid-crystal-on-silicon devices, scanning microelectromechanical systems mirror devices, other reflective display devices, or other displays). 
     Optical couplers  84  (e.g., prisms, holograms, etc.) may be used to couple respective left and right images from the left and right display portions into respective left and right waveguides  86 . The images may be guided within waveguides  86  in accordance with the principal of total internal reflection. In this way, the left and right images may be transported from the left and right sides of device  10  towards locations in the center of device  10  that are aligned with left and right eye boxes  60 . Waveguides  86  may be provided with respective left and right output couplers  88  such as holograms formed on or in the material of waveguides  86 . The left and right output couplers  88  may respectively couple the left and right images from the left and right waveguides  86  towards the left and right eye boxes  60  for viewing by the user. This allows a user to view a computer-generated image (display image) such as computer-generated object  92  overlaid over real-world objects such as real-world object  90 . 
     By adjusting lenses and other optical components in components  100  and/or  102 , the distance from device  10  at which display image  92  is in focus for the user viewing from eye boxes  60  can be adjusted. These adjustments may be made without affecting the focus of real-world objects such as real-world object  90 . In this way, real-world objects such as real-world object  90  may be observed by the user as if device  10  were not present (e.g., without any intervening optical components) while computer-generated content such as virtual object  92  may be placed within the scene being viewed by the user at one or more desired distances from the user. 
     Time-interleaving and polarization control techniques may be used in merging real-world content and display content in the optical system for device  10 . 
     Consider, as an example, the time-division multiplexing arrangement of  FIG.  3 A .  FIG.  3 A  is a diagram of an illustrative optical system (optical system  122 ) that may be used for both the left-hand and right-hand portion of device  10 . As shown in  FIG.  3 A , system  122  includes outer optical components such as optical components  100  and inner optical components such as optical components  102 . Electrically adjustable devices in components  100  and/or  102  are controlled by control circuitry  12 . Waveguide  86  and, in particular, the portion of waveguide  86  with output coupler  88 , is interposed between components  100  and  102 . Real-world image light  104  passes through system  122  and is viewable by a user&#39;s eye at eye box  60 . Computer-generated image light (display light)  124  is guided to output coupler  88  through waveguide  86  to output coupler  88 . Output coupler  88  couples light  124  out of waveguide  86 , so that light  124  passes through components  102  to eye box  60 . 
     System  122  has bias lenses  106  and  120 . The powers of bias lenses  106  and  120  may be complementary. For example, bias lens  106  may have a positive lens power such as 1.5 diopter and bias lens  120  may have a negative lens power such as a −1.5 diopter. With this type of arrangement, the positive power of lens  106  is cancelled by the corresponding negative power of lens  120 , so that the net effect is as if there were no lens present between the real-world objects and eye box  60  (e.g., real-world image  104  experiences a zero lens power from lenses  106  and  120  when traveling to eye box  60 ). At the same time, the negative power of lens  120  is present in components  102 . 
     Components  100  include electronic shutter  105 . Electronic shutter  105 , which may sometimes be referred to as an intensity switch or electrically adjustable light modulator, may include linear polarizer  108 , polarization switch  110 , and linear polarizer  112 . Linear polarizer  108  may have a pass axis aligned with the Y axis, so that light  104  is linearly polarized along the Y axis after passing through polarizer  108 . Polarization switch  110 , which may sometimes be referred to as an electrically adjustable wave plate, electrically adjustable retarder, or electrically adjustable polarization controller, may be formed from an electrically adjustable optical component such as a twisted nematic liquid crystal layer (as an example). Alternating-current drive signals may be used to control the operation of polarization switch  110  to avoid undesirable charge accumulation effects that might otherwise arise from using a control signal of a fixed polarity. 
     In a first state (sometimes referred to as an OFF state, where a 0V peak-to-peak drive signal is applied), polarization switch  110  rotates the polarization of incoming linearly polarized light from polarizer  108  by 90° so that light  104  is polarized along the X axis after exiting polarization switch  110 . Linear polarizer  112  has a pass axis aligned with the X axis and therefore passes light  104  in the first state. In a second state (sometimes referred to as an ON state, where a 20V peak-to-peak drive signal or other suitable drive signal is applied), polarization switch  110  does not rotate the polarization of incoming linearly polarized light. In this state, light  104  is blocked by polarizer  112 . As this demonstrates, the adjustability of polarization switch  110  allows polarizer  108 , polarization switch  110 , and polarizer  112  to serve as an electrically adjustable shutter that can either block or pass real-world light  104  to eye box  60 . 
     Optical components  102  may include linear polarizer  114 . Linear polarizer  114  may have a pass axis aligned with the X axis and may serve to block light polarized along the Y axis as described in connection with polarizer  112 . The inclusion of polarizer  112  may help reduce display light that leaks out of output coupler  88  in the +Z direction. If desired, polarizer  112  may be omitted. In configurations in which polarizer  112  is omitted, polarizer  114 , polarizer  108 , and polarization switch  110  form the electronic shutter. 
     Optical components  102  may include a tunable lens such as a liquid crystal lens. The position of the lens center of the tunable lens and/or the lens power of the lens may be adjusted by control circuitry  12 . For example, the position of the lens center of the adjustable lens may be controlled in real time based on information from a gaze tracking system that is monitoring the direction of gaze of the user (e.g., by monitoring the user&#39;s eye in eye box  60 ). This allows the center of the lens to be aligned along the user&#39;s direction of gaze. 
     In the example of  FIG.  3 A , components  102  include liquid crystal lens  118 . Lens  118  is electrically adjustable. During operation, control circuitry  12  can adjust the power of liquid crystal lens  118  to place virtual objects in desired focal planes. Liquid crystal lens  118  may, as an example, exhibit a positive lens power that is tunable between first and second positive lens power values, may exhibit a negative lens power that is tunable between first and second negative lens power values, or may have a lens power that is adjustable between a positive value (e.g., +1 diopter) and a negative value (e.g., −1 diopter). The net power of the lens system between output coupler  88  and eye box  60  is given by the combined lens powers of inner (rear) bias lens  120  and liquid crystal lens  118 . In some configurations, inclusion of a negative rear bias lens may help provide a desired overall negative lens power to the user (e.g., a lens power ranging from −0.5 diopter which may be used to place virtual objects at a focal plane distance of 2 m from eye box  60  to −2.5 diopter which may be used to place virtual objects at a focal plane distance of 40 cm from eye box  60 ) while allowing lens  118  to exhibit both positive and negative lens powers, thereby helping to avoid tuning challenges that may sometimes be present when creating only negative liquid crystal lens powers. Lens  118  may be configured to exhibit a desired lens power (e.g., 1 diopter and/or other suitable lens powers) for light polarized along the Y axis while exhibiting no lens power (0 diopter) for light polarized along the X axis. Lens  118  may have any suitable number of layers of liquid crystal cells (e.g., one layer, two or more layers, three or more layers, etc.). If desired, a multiple-layer configuration may be used for lens  118  to allow lens  118  to provide an electrically adjustable lens center position, to allow the optical performance of lens  118  to be enhanced, etc. 
     Time division multiplexing may be used by optical system  122  to merge real-world light  104  and display light  124  at eye box  60  for viewing by a user. 
     During first time periods, which may sometimes be referred to as “world view off” periods, polarization switch  110  of intensity switch  105  is adjusted to block real-world light  104 . Display light  124  from output coupler  88  is linearly polarized along the X axis by polarizer  114 . Optical system  122  may have a polarization switch such as polarization switch  116 . Polarization switch  116  may be turned OFF whenever polarization switch  110  is ON and intensity switch  105  is blocking real-world image light  104 . Because polarization switch  116  is OFF, polarization switch  116  rotates the polarization of display light  124  so that display light  124  is aligned along the Y axis. Liquid crystal lens  118  is adjusted by control circuitry  12  to produce a desired lens power for light polarized along the Y axis. Bias lens  120  provides additional desired lens power. Light  124  therefore reaches eye box  60  with a desired lens power interposed between optical coupler  88  and eye box  60 . By adjusting this lens power (e.g., when control circuitry  12  adjusts lens  118 ) while producing synchronized image frames with display  14  while intensity switch  105  is opaque and blocking real-world light, virtual objects associated with respective frames of display image light  124  may be placed in one or more desired focal planes. 
     During second time periods, which may sometimes be referred to as “world view on” periods, polarization switch  110  of intensity switch  105  is adjusted to pass real-world light  104  while display  14  is optionally turned off (and light  124  is not produced). Polarization switch  116  is placed in a state that allows light to pass through lens  118 . During the second time periods, the user views real-world objects through system  122 . Liquid crystal lens  118  is only sensitive to light polarized along the Y axis and is insensitive to light polarized along the X axis. Light  104  is polarized along the X axis when passing through polarizer  114  and polarization switch  116  may be turned ON, so light  104  maintains its polarization state along the X-axis when passing through lens  118  and is therefore not affected by lens  118 . The combined optical powers of front bias lens  106  and rear bias lens  120  cancel (in this example), so that no net lens power is present between eye box  60  and the real world (i.e., real-world light  104  reaches eye box  60  unaffected by optical system  122 ). As shown in  FIG.  3 B , while real-world light  104  passes through system  122  in the second time periods (world view on periods), display  14  can be either turned on or off. Display  14  may, for example, be turned on or off depending on the depth of the virtual content to be displayed for the user in eye box  60 . For example, display  14  can be turned on if the virtual content that is to be placed at the focal plane corresponding to lens  118  has zero optical power. 
     During operation, control circuitry  12  may operate the polarization switches and other adjustable components of device  10  synchronization (e.g. alternating between world view on and world view off periods). The relative duty cycle between the world view on and off states may be 50% (50% on and 50% off) or may have any other suitable value (e.g., 60%-70% on, less than 80% on, more than 30% on, etc.). The world view may also be on with 100% duty cycle when there is no need to adjust the depth of the virtual content. In other words, in the configuration of  FIGS.  3 A and  3 B  (and, if desired, other configurations such as the configurations of  FIGS.  6  and  9   ), the depth feature can be disabled when it is desired to increase the brightness of the world view. 
     If desired, other polarization-dependent lenses may be used for lens  118 . For example, a geometrical phase lens or a fixed birefringent lens may be used in place of tunable lens  118 . A fixed polarization-dependent lens provides two different lens power choices to system  122 , depending on the polarization state of the light passing through the lens. Eye tracking and lens center adjustments are not be used in this configuration, because the lens center positions of the fixed lens are fixed. 
     If desired, optical system  122  may use pairs of complementary geometrical phase lenses. Geometrical phase lenses may be implemented using liquid crystal lens structures configured to exhibit a positive lens power for one circular polarization such as right-hand circular polarization (RCP) and a negative lens power for an opposite circular polarization such as left-hand circular polarization (LCP). Because both positive and negative lens powers are exhibited when presented with unpolarized light (containing equal portions of RCP and LCP light), polarization control is used to avoid undesired double images. 
       FIG.  4 A  shows an optical system based on geometrical phase lenses GPL 1  and GPL 2 . Front and rear bias lenses  106  and  120  are omitted from  FIG.  4 A  and the subsequent FIGS. to avoid over-complicating the drawings. 
     As shown in  FIG.  4 A  optical system  122  may have quarter wave plate QWP 2  between geometrical phase lens GPL 2  and polarization switch P 2  (an electrically adjustable polarization rotator). Linear polarizer LPOL is interposed between waveguide  86  (output coupler  88 ) and polarization switch P 1 . Quarter wave plate QWP 1  is located between polarization switch P 1  and lens GPL 1 . In this configuration, polarization switches P 1  and P 3  operate as polarization rotators for linear polarization. In other configurations, quarter wave plate QWP 2  and polarization switch P 2  can be combined to form a different type of polarization switch which works for circular polarization. Similarly, quarter wave plate QWP 1  and polarization switch P 1  can be combined to form a polarization switch that works for circularly polarized light. In other words, quarter wave plates QWP 1  and QWP 2  can be omitted. 
     When polarization switch P 2  and polarization switch P 1  are OFF, RCP real-world light  104  is converted to LCP light by lens GPL 2 . Quarter wave plate QWP 2  converts this LCP light to light that is linearly polarized along the Y axis. Polarization switch P 2  is off and therefore rotates this light so that it is polarized along the X axis. Linear polarizer linear POL blocks this light. In this way, RCP real-world light is prevented from reaching the user. 
     When polarization switch P 2  and polarization switch P 1  are OFF, LCP real-world light  104  is converted to RCP light by lens GPL 2 , which exhibits a negative lens power. This light is converted to linearly polarized light that is polarized along the X axis by quarter wave plate QWP 2 . Polarization switch P 2  is OFF and therefore rotates the polarization of this light so that it is linearly polarized along the Y axis. After passing through waveguide  86  (output coupler  88 ) and linear polarizer LPOL, this light reaches polarization switch P 1 . Polarization switch P 1  is OFF and therefore rotates the polarization of light  104  so that the light exiting polarization switch P 1  is polarized along the X axis. Quarter wave plate QWP 1  converts this linearly polarized light to RCP light. As the RCP light passes through lens GP 1 , lens GP 1  exhibits a positive lens power equal and opposite to that of lens GPL 2 , so real-world light  104  is not affected by any lens power (e.g., the lens power of lenses GPL 2  and GPL 1  when combined is 0 diopter, so that real-world light  104  can be viewed by the user as if system  122  were not present). 
     When polarization switches P 1  and P 2  are ON, LCP light  104  is blocked. RCP light passes through lens GPL 2 , which exhibits a positive lens power. Polarization switches P 1  and P 2  are ON and therefore do not change the polarization state of the light passing through them. After passing through the components between lens GPL 2  and GPL 1 , light  104  becomes left-hand circularly polarized. As shown in  FIG.  4 A , when LCP light  104  reaches lens GPL 1 , lens GPL 1  exhibits a negative lens power equal and opposite to the positive lens power of lens GPL 2 . As when polarization switches P 1  and P 2  were both OFF, real-world light  104  is unaffected by the presence of lenses GPL 1  and GPL 2  when polarization switches P 1  and P 2  are ON, because the lens powers of lenses GPL 1  and GPL 2  cancel each other. 
     Display light  124 , in contrast, is affected by the switching of polarization switches P 1  and P 2 . When these switches are OFF, light  124  is RCP at the input to lens GPL 1 , which exhibits a positive lens power. When polarization switches P 1  and P 2  are ON, however, light  124  is LCP at the input to lens GPL 1 , so that lens GPL 1  exhibits a negative lens power. 
     During operation, the states of polarization switches P 1  and P 2  are adjusted in tandem (e.g., by alternating between ON and OFF in synchronization with each other with a desired duty cycle). Real-world light  104  is unaffected by the changes in state of polarization switches P 1  and P 2 , which allows the user to view the real world through system  122  as if system  122  were not present. Display light  124  experiences alternating lens powers due to its changing polarization state. When converted to RCP light, lens GPL 1  applies a positive lens power to display light  124 , whereas when converted to LCP light, lens GPL 1  applies a negative lens power to display light  124 . The system of  FIG.  4 A  therefore allows virtual objects (e.g., display image frames from display  14  that are appropriately synchronized with the switching of polarization switches 1 and 2) to be placed at two different focal planes. Systems such as the system of  FIG.  4 A  and the other systems described herein may, if desired, use component stacking arrangements to implement additional levels of focal plane positioning. The arrangements where optical system  122  exhibits first and second states with first and second respective focal plane positions for virtual objects in display images are described herein as an example. 
     In the illustrative configuration of  FIG.  4 B , intensity switch  105  has a pair of linear polarizers LPOL and a switchable polarizer P 2 . A linear polarizer LPOL, polarization switch P 1  (for selecting a desired lens power for geometric phase lens GPL), and quarter wave plate QWP are located between geometric phase lens GPL and waveguide  86 . With this configuration, the power of the bias lens can be configured such that display  14  may exhibit slight negative power when the positive power of geometric phase lens GPL is selected. In an example, geometric phase lens GPL has a power of +/−1D, negative bias lens  120  has a power of −1.5D, and positive bias lens  106  has a power of 0.5D. When the positive power is selected for geometric phase lens GPL, display power will be +1D−1.5D=−0.5D and the power applied to real-world light (sometimes referred to as world power) will be +0.5D+1D−1.5D=0D. When negative power is selected, display power will be −1D−1.5D=−2.5D. 
     In the illustrative configuration of  FIG.  5 A , optical system  122  has only a single polarization switch (switch P) and the location of linear polarizer LPOL has been changed so that linear polarizer LPOL is between polarization switch P and eye box  60 . There is also only a single quarter wave plate (QWP) in system  122  of  FIG.  5 A . As shown in  FIG.  5 A , real-world light  104  passes through system  122  with 0 lens power regardless of whether polarization switch P is ON or OFF, because the positive power of geometrical phase lens GPL 2  cancels the equal and opposite negative lens power of geometrical phase lens GPL 1 , whereas display light  124  passes through a negative lens (GPL 1 ) when polarization switch P is OFF and passes through a positive lens (GPL 1 ) when the polarization switch is ON. 
     In the illustrative configuration of  FIG.  5 B , a clean-up polarization switch formed from linear polarizer LPOL′, polarization switch P′, and quarter wave plate QWP′ has been added to optical system  122  of  FIG.  5 A  to help block undesired ghost image light and thereby improve the contrast ratio between the main image and ghost image. Polarization switch P′ may be operated in synchronization with polarization switch P. 
     In the illustrative configuration of  FIG.  6   , system  122  has a polarization switches PSA and PSB. Switch PSA may be used with a pair of linear polarizers LPOLX and LPOLY to implement an intensity switch. Switch PSB may be configured so that when switch PSB is ON, RCP light passes through switch PSB unaffected and may be configured so that when switch PSB is OFF, incoming RCP light is converted to LCP light. 
     During operation in “world view on” mode, display  14  is turned off and switch PSA (and the electronic switch formed from polarizers LPOLX and LPOLY and polarization switch PSA) may be adjusted to pass light  104  through waveguide  86  and coupler  88 . LCP light is presented to lens GPL 1 , which exhibits a negative lens power and RCP light is presented to lens GPL 2 , which exhibits a cancelling positive lens power. 
     During operation in “world view off” mode, display  14  is turned on and switch PSA is adjusted to block real-world light  104 . Frames of image light (e.g., alternating first and second frames corresponding to alternating first and second virtual objects) are synchronized with the state of polarization switch PSB. When the first frames are presented, switch PSB is turned ON and light  124  experiences a negative lens power when passing through lens GPL 1  and a cancelling positive lens power when passing through lens GPL 2 . When the second frames are presented, switch PSB is turned OFF and light  124  experiences a negative lens power when passing through lens GPL 1  and another negative lens power when passing through lens GPL 2 . In this way, the first frames of display light experience 0 lens power and the second frames of display light experience a negative lens power (equal to the summation of the negative lens powers of lenses GPL 1  and GPL 2 ). As with the other systems shown in the FIGS., bias lenses such as a front positive fixed bias lens and a complementary rear negative fixed bias lens may be included in system  122 . 
     Another illustrative arrangement for optical system  122  is shown in  FIG.  7   . When polarization switch P is ON, real-world light  104  experiences 0 lens power and RCP display light  124  experiences 0 lens power. LCP display light is blocked. When polarization switch P is OFF, real-world light is blocked by linear polarizer LPOL and display light  124  experiences a negative lens power. Display  14  can be turned on and off depending on desired content depth. 
     In the illustrative configuration of  FIG.  8   , display  14  supplies waveguide  86  alternately with RCP display light  124  or LCP display light  124  and waveguide  86  preserves the polarization state of the light from display  14 . Components such as the quarter wave plate QWP, linear polarizer LPOL, and polarization switch P of  FIG.  7    may be omitted. Different virtual object locations are achieved by displaying content for different depths with different polarizations (RCP for one depth and LCP for another depth). 
       FIG.  9    shows another illustrative configuration for optical system  122 . In the example of  FIG.  9   , geometrical phase lens (GPL′) has been configured to pass 0 th  order light (light striking lens GPL′ at an angle parallel to the surface normal of lens GPL′) with an intensity comparable to that of the RCP and LCP output light from lens GPL′. Accordingly, when lens GPL′ of  FIG.  9    is presented with unpolarized light (e.g., light having equal parts of LCP and RCP light), there will be three outputs: 1) LCP light (experiencing a negative lens power), 2) RCP light (experiencing a positive lens power), and 3) 0 th  order light (experiencing no lens power). Optical system  122  of  FIG.  9    is configured to block LCP light exiting lens GPL′. When display  14  is off, polarization switch P 2  (which forms an electronic shutter with linear polarizers LPOL- 1  and LPOL- 2 ) is configured to allow real-world light to pass to polarization switch P 1 . Polarization switch P 1  is OFF, which allows the real-world light to be passed to lens GPL′ as RCP light. As real-world light  104  passes through lens GPL′, lens GPL′ exhibits a 0 lens power. 
     When display  14  is on, polarization switch P 2  is adjusted so that real-world light  104  is blocked. The state of polarization switch P 1  is alternated in synchronization with the image frames produced by display  14 , so that virtual objects can be presented in different focal planes. When switch P 1  is ON, light  124  experiences a negative lens power when passing through lens GPL′ and when switch P 1  is OFF, light  124  experiences a 0 lens power when passing through lens GPL′. 
     System  8  may gather and use personally identifiable information. It is well understood that the use of personally identifiable information should follow privacy policies and practices that are generally recognized as meeting or exceeding industry or governmental requirements for maintaining the privacy of users. In particular, personally identifiable information data should be managed and handled so as to minimize risks of unintentional or unauthorized access or use, and the nature of authorized use should be clearly indicated to users. 
     Physical Environment 
     A physical environment refers to a physical world that people can sense and/or interact with without aid of electronic systems. Physical environments, such as a physical park, include physical articles, such as physical trees, physical buildings, and physical people. People can directly sense and/or interact with the physical environment, such as through sight, touch, hearing, taste, and smell. 
     Computer-Generated Reality 
     In contrast, a computer-generated reality (CGR) environment refers to a wholly or partially simulated environment that people sense and/or interact with via an electronic system. In CGR, a subset of a person&#39;s physical motions, or representations thereof, are tracked, and, in response, one or more characteristics of one or more virtual objects simulated in the CGR environment are adjusted in a manner that comports with at least one law of physics. For example, a CGR system may detect a person&#39;s head turning and, in response, adjust graphical content and an acoustic field presented to the person in a manner similar to how such views and sounds would change in a physical environment. In some situations (e.g., for accessibility reasons), adjustments to characteristic(s) of virtual object(s) in a CGR environment may be made in response to representations of physical motions (e.g., vocal commands). 
     A person may sense and/or interact with a CGR object using any one of their senses, including sight, sound, touch, taste, and smell. For example, a person may sense and/or interact with audio objects that create 3D or spatial audio environment that provides the perception of point audio sources in 3D space. In another example, audio objects may enable audio transparency, which selectively incorporates ambient sounds from the physical environment with or without computer-generated audio. In some CGR environments, a person may sense and/or interact only with audio objects. 
     Examples of CGR include virtual reality and mixed reality. 
     Virtual Reality 
     A virtual reality (VR) environment refers to a simulated environment that is designed to be based entirely on computer-generated sensory inputs for one or more senses. A VR environment comprises a plurality of virtual objects with which a person may sense and/or interact. For example, computer-generated imagery of trees, buildings, and avatars representing people are examples of virtual objects. A person may sense and/or interact with virtual objects in the VR environment through a simulation of the person&#39;s presence within the computer-generated environment, and/or through a simulation of a subset of the person&#39;s physical movements within the computer-generated environment. 
     Mixed Reality 
     In contrast to a VR environment, which is designed to be based entirely on computer-generated sensory inputs, a mixed reality (MR) environment refers to a simulated environment that is designed to incorporate sensory inputs from the physical environment, or a representation thereof, in addition to including computer-generated sensory inputs (e.g., virtual objects). On a virtuality continuum, a mixed reality environment is anywhere between, but not including, a wholly physical environment at one end and virtual reality environment at the other end. 
     In some MR environments, computer-generated sensory inputs may respond to changes in sensory inputs from the physical environment. Also, some electronic systems for presenting an MR environment may track location and/or orientation with respect to the physical environment to enable virtual objects to interact with real objects (that is, physical articles from the physical environment or representations thereof). For example, a system may account for movements so that a virtual tree appears stationery with respect to the physical ground. 
     Examples of mixed realities include augmented reality and augmented virtuality. 
     Augmented Reality 
     An augmented reality (AR) environment refers to a simulated environment in which one or more virtual objects are superimposed over a physical environment, or a representation thereof. For example, an electronic system for presenting an AR environment may have a transparent or translucent display through which a person may directly view the physical environment. The system may be configured to present virtual objects on the transparent or translucent display, so that a person, using the system, perceives the virtual objects superimposed over the physical environment. Alternatively, a system may have an opaque display and one or more imaging sensors that capture images or video of the physical environment, which are representations of the physical environment. The system composites the images or video with virtual objects, and presents the composition on the opaque display. A person, using the system, indirectly views the physical environment by way of the images or video of the physical environment, and perceives the virtual objects superimposed over the physical environment. As used herein, a video of the physical environment shown on an opaque display is called “pass-through video,” meaning a system uses one or more image sensor(s) to capture images of the physical environment, and uses those images in presenting the AR environment on the opaque display. Further alternatively, a system may have a projection system that projects virtual objects into the physical environment, for example, as a hologram or on a physical surface, so that a person, using the system, perceives the virtual objects superimposed over the physical environment. 
     An augmented reality environment also refers to a simulated environment in which a representation of a physical environment is transformed by computer-generated sensory information. For example, in providing pass-through video, a system may transform one or more sensor images to impose a select perspective (e.g., viewpoint) different than the perspective captured by the imaging sensors. As another example, a representation of a physical environment may be transformed by graphically modifying (e.g., enlarging) portions thereof, such that the modified portion may be representative but not photorealistic versions of the originally captured images. As a further example, a representation of a physical environment may be transformed by graphically eliminating or obfuscating portions thereof. 
     Augmented Virtuality 
     An augmented virtuality (AV) environment refers to a simulated environment in which a virtual or computer generated environment incorporates one or more sensory inputs from the physical environment. The sensory inputs may be representations of one or more characteristics of the physical environment. For example, an AV park may have virtual trees and virtual buildings, but people with faces photorealistically reproduced from images taken of physical people. As another example, a virtual object may adopt a shape or color of a physical article imaged by one or more imaging sensors. As a further example, a virtual object may adopt shadows consistent with the position of the sun in the physical environment. 
     Hardware 
     There are many different types of electronic systems that enable a person to sense and/or interact with various CGR environments. Examples include head mounted systems, projection-based systems, heads-up displays (HUDs), vehicle windshields having integrated display capability, windows having integrated display capability, displays formed as lenses designed to be placed on a person&#39;s eyes (e.g., similar to contact lenses), headphones/earphones, speaker arrays, input systems (e.g., wearable or handheld controllers with or without haptic feedback), smartphones, tablets, and desktop/laptop computers. A head mounted system may have one or more speaker(s) and an integrated opaque display. Alternatively, a head mounted system may be configured to accept an external opaque display (e.g., a smartphone). The head mounted system may incorporate one or more imaging sensors to capture images or video of the physical environment, and/or one or more microphones to capture audio of the physical environment. Rather than an opaque display, a head mounted system may have a transparent or translucent display. The transparent or translucent display may have a medium through which light representative of images is directed to a person&#39;s eyes. The display may utilize digital light projection, OLEDs, LEDs, μLEDs, liquid crystal on silicon, laser scanning light source, or any combination of these technologies. The medium may be an optical waveguide, a hologram medium, an optical combiner, an optical reflector, or any combination thereof. In one embodiment, the transparent or translucent display may be configured to become opaque selectively. Projection-based systems may employ retinal projection technology that projects graphical images onto a person&#39;s retina. Projection systems also may be configured to project virtual objects into the physical environment, for example, as a hologram or on a physical surface. 
     The foregoing is merely illustrative and various modifications can be made to the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20200721
Publication Date: 20230919
Grant Date: 20230919
Priority Date: 20190813
Inventors: YAN, Jin
LI, XIAOKAI
YANG, YOUNG CHEOL
Assignee: APPLE INC
CPC Classifications: [{"code": "G02F1/0136", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B27/0172", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B27/0172", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/283", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B3/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/137", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/29", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/291", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/294", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B26/06", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B3/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/0136", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/005", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/137", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/286", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/0172", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B3/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/005", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/286", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/0136", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/137", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 74568187