Reflector orientation for geometric and hybrid waveguides to reduce grating appreciation

Abstract

A waveguide display system includes a waveguide, an input coupler configured to couple display light into the waveguide, a first pupil expander, and a second pupil expander. The first pupil expander is configured to deflect the display light toward the second pupil expander at a first plurality of positions in a first direction. The second pupil expander is configured to deflect the display light from the first pupil expander toward the eyebox of the waveguide display system at a second plurality of positions in a second direction different from the first direction. At least one of the input coupler, the first pupil expander, or the second pupil expander includes a plurality of transflective mirrors that are inclined within the waveguide such that the plurality of transflective mirrors are not apparent when viewed from an oblique angle.

Description

Background Art

[0001] Artificial reality systems such as head-mounted display (HMD) or heads-up display (HUD) systems typically include a near-eye display (e.g., in the form of a headset or a pair of glasses), which is configured to present content to a user via, for example, an electronic or optical display within approximately 12 mm to 20 mm in front of the user's eyes. As in virtual reality (VR) applications, augmented reality (AR) applications, or mixed reality (MR) applications, the near-eye display can display virtual objects or combine an image of a real object with virtual objects. For example, in an AR system, a user can view an image of a virtual object (e.g., a computer-generated image (CGI)) and an image of the surrounding environment (commonly referred to as optical see-through) through, for example, transparent display glasses or lenses.

[0002] An example of an optical see-through AR system can use a waveguide-based optical display, where light projecting an image can be coupled into the waveguide (e.g., a transparent substrate), propagate within the waveguide, and be coupled out of the waveguide at different positions. In some embodiments, diffractive optical elements (e.g., surface relief gratings or volume Bragg gratings) can be used to couple light projecting an image into or out of the waveguide. Light from the surrounding environment can pass through the see-through region of the waveguide and reach the user's eyes. Summary of the Invention

[0003] The present disclosure generally relates to near-eye display systems. More specifically, the techniques disclosed herein relate to waveguide-based near-eye display systems that include a partially reflective mirror for pupil expansion. Various creative embodiments are described herein, including devices, components, systems, modules, and subsystems, etc.

[0004] According to some embodiments, a waveguide display system may include: a waveguide; an input coupler configured to couple display light into the waveguide; a first pupil expander; and a second pupil expander. The first pupil expander may be configured to deflect display light towards the second pupil expander at a first plurality of positions along a first direction. The second pupil expander may be configured to deflect the display light from the first pupil expander towards an eye box of the waveguide display system at a second plurality of positions along a second direction different from the first direction. At least one of the first pupil expander or the second pupil expander may include a plurality of transflective mirrors that are tilted within the waveguide such that the plurality of transflective mirrors are not apparent when viewed at an oblique angle.

[0005] In some embodiments of the waveguide display system, the first pupil expander may include a transflective mirror tilted within the waveguide at an angle between 40° and 60° with respect to a broadside surface of the waveguide. In some embodiments, the second pupil expander may include a transflective mirror tilted within the waveguide at an angle between 25° and 35° with respect to the broadside surface of the waveguide. In some embodiments, the plurality of transflective mirrors may be characterized by different respective reflection efficiencies. In some embodiments, at least one of the input coupler, the first pupil expander, or the second pupil expander may include a multiplexed volume Bragg grating, wherein the multiplexed volume Bragg grating may include a reflective diffraction grating or a transmissive diffraction grating.

[0006] In some embodiments of the waveguide display system, the input coupler may include a volume Bragg grating, a surface relief grating, a prism, or a reflective surface. Each of the plurality of transflective mirrors may include a plurality of dielectric coatings. In some embodiments, the width of the light beam reflected by each of the plurality of transflective mirrors may be greater than half of the thickness of the waveguide. In some embodiments, each of the plurality of transflective mirrors may be characterized by a full-width half-magnitude (FWHM) reflection angle range greater than 40°. In some embodiments, at least one of the plurality of transflective mirrors is characterized by a reflectivity greater than 50%.

[0007] In some embodiments of a waveguide display system, an input coupler may include a first volume Bragg grating characterized by a first grating vector, a second pupil expander may include a second volume Bragg grating characterized by a second grating vector, and the first grating vector and the second grating vector may have the same component in a plane parallel to the wide-side surface of the waveguide. When viewed in the direction of the surface normal of the waveguide, the first pupil expander and the second pupil expander may at least partially overlap. In some embodiments, the waveguide display system may include a deflector configured to deflect display light from the input coupler towards the first pupil expander. In some embodiments, the deflector may include a first set of one or more mirrors and / or transmissive mirrors having a first orientation, and the first pupil expander may include a second set of one or more mirrors and / or transmissive mirrors having a first orientation. In some embodiments, the input coupler may include a first set of one or more mirrors and / or transmissive mirrors having a first orientation, and the second pupil expander may include a second set of one or more mirrors and / or transmissive mirrors having a first orientation.

[0008] According to certain embodiments, a near-eye display system may include: an image source configured to emit display light of an image; a waveguide that is transmissive to visible light; display optics configured to project the display light onto the waveguide; an input coupler configured to couple the display light into the waveguide; a first pupil expander configured to split the display light at a first plurality of positions along a first direction; and a second pupil expander configured to split the display light from each of the first plurality of positions from the first pupil expander at a second plurality of positions along a second direction different from the first direction. At least one of the first pupil expander or the second pupil expander includes a plurality of transmissive mirrors that are tilted within the waveguide such that the plurality of transmissive mirrors are not apparent when viewed at an oblique angle.

[0009] In some embodiments of a near-eye display system, the first pupil expander may include a transmissive mirror tilted within the waveguide at an angle between 40° and 60° relative to the wide-side surface of the waveguide, and the second pupil expander may include a transmissive mirror tilted within the waveguide at an angle between 25° and 35° relative to the wide-side surface of the waveguide. In some embodiments, the plurality of transmissive mirrors may be characterized by different respective reflection efficiencies, and the width of the light beam reflected by each of the plurality of transmissive mirrors may be greater than half of the thickness of the waveguide.

[0010] According to some embodiments, a near-eye display system may include: a waveguide that is transmissive to display light; an input coupler configured to couple the display light into the waveguide, and the input coupler includes a first set of one or more mirrors and / or transmissive mirrors having a first orientation; a first pupil expander; and a second pupil expander. The first pupil expander may be configured to deflect display light from the input coupler toward the second pupil expander at a first plurality of positions along a first direction, and the first pupil expander includes a second set of one or more mirrors and / or transmissive mirrors having a second orientation. The second pupil expander may be configured to deflect display light from the first pupil expander toward an eyebox of the near-eye display system at a second plurality of positions along a second direction different from the first direction, and the second pupil expander includes a third set of one or more mirrors and / or transmissive mirrors having a first orientation.

[0011] This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used alone to determine the scope of the claimed subject matter. The subject matter should be understood by reference to the appropriate portions of the entire specification of this disclosure, any drawings, or all of the drawings, and each claim. The foregoing and other features and examples will be described in more detail below in the following specification, claims, and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Exemplary embodiments are described in detail below with reference to the following drawings.

[0013] Figure 1 is a simplified block diagram of an example of an artificial reality system environment including a near-eye display according to some embodiments.

[0014] Figure 2 is a perspective view of an example of a near-eye display in the form of a head-mounted display (HMD) device for implementing some of the examples disclosed herein.

[0015] Figure 3 is a perspective view of an example of a near-eye display in the form of a pair of glasses for implementing some of the examples disclosed herein.

[0016] Figure 4 shows an example of an optical see-through augmented reality system including a waveguide display according to some embodiments.

[0017] Figure 5 shows an example of an optical see-through augmented reality system including a waveguide display for exit pupil expansion according to some embodiments.

[0018] Figure 6A shows an example of a waveguide display system including a waveguide and a diffraction grating for exit pupil expansion;

[0019] Figure 6B Shows an example of an eyepiece frame including a two-dimensional replicated exit pupil;

[0020] Figure 7A Includes a curve showing the angular bandwidth of an example of a volume Bragg grating (VBG);

[0021] Figure 7B Includes a curve showing the angular bandwidth of an example of a transmissive-reflective lens;

[0022] Figure 8A Shows an example of a waveguide display including three or four sets of mirrors and / or transmissive-reflective lenses for two-dimensional pupil expansion and dispersion compensation according to certain embodiments;

[0023] Figure 8B Shows an example of an input coupler including a mirror according to certain embodiments;

[0024] Figure 8C Shows another example of an input coupler including one mirror and multiple transmissive-reflective lenses according to certain embodiments;

[0025] Figure 9A and Figure 9B Shows an example of a waveguide display including an array of transmissive-reflective lenses in a waveguide;

[0026] Figure 9C Shows an example of a near-eye display system having a transmissive-reflective lens in a waveguide;

[0027] Figure 10A and Figure 10B Shows an example of a waveguide display including a geometric mirror for pupil expansion according to certain embodiments;

[0028] Figures 11A to 11C Shows the relationship between the optical resolution of an imaging system and the size of the optical aperture (or input beam width);

[0029] Figure 12A Shows an example of a pupil expander in the form of a geometric waveguide including a set of transmissive-reflective lenses in a waveguide;

[0030] Figure 12B Shows another example of a pupil expander in the form of a geometric waveguide including a set of transmissive-reflective lenses in a waveguide according to certain embodiments;

[0031] Figure 13 Shows an example of a waveguide display system according to certain embodiments;

[0032] Figure 14 Shows another example of a waveguide display system according to certain embodiments;

[0033] Figure 15 shows another example of a waveguide display system according to certain embodiments; and

[0034] Figure 16 is a simplified block diagram of an electronic system that is an example of an example near-eye display for implementing some of the various examples disclosed herein.

[0035] These figures depict embodiments of the present disclosure for illustrative purposes only. Those skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods shown can be employed without departing from the principles of the present disclosure or the benefits claimed herein.

[0036] In the figures, similar components and / or features may have the same reference numerals. Further, various components of the same type can be distinguished by following the reference numeral with a dash and a second label that differentiates the multiple similar components. If only the first reference numeral is used in the specification, the specification applies to any one of the multiple similar components having the same first reference numeral, regardless of the second reference numeral. Detailed Description

[0037] The present disclosure generally relates to near-eye display systems. More specifically, the techniques disclosed herein relate to waveguide-based near-eye display systems that include a partially reflective mirror for pupil expansion. Various inventive embodiments are described herein, including devices, components, systems, modules, and subsystems, etc.

[0038] Optical see-through near-eye display systems that use waveguides and diffraction gratings (e.g., volume Bragg gratings (VBGs)) to present a display image from a projector to a user's eye may have a limited field of view (FOV) and spectral coverage due to, for example, the limited angular and spectral bandwidths of the diffraction gratings. Some diffraction gratings (e.g., VBGs) may also have a limited diffraction efficiency. Additionally, multiple gratings for one-dimensional or two-dimensional pupil expansion may perform multiple optical filtering on the display image (e.g., Bragg filtering due to the limited bandwidth of the VBG), which may result in optical artifacts such as truncated optical line patterns that may degrade the quality of the display image.

[0039] In some embodiments, an optical see-through near-eye display system may include a waveguide in which one or more partially reflective mirror arrays are embedded at multiple locations in the waveguide to direct display images from the multiple locations to a user's eye, thereby replicating an exit pupil and expanding the eyebox in one or two dimensions. The partially reflective mirror may also be referred to as a transmissive-reflective mirror, a geometric mirror, or a geometric reflector. A waveguide including a transmissive-reflective mirror in the waveguide may be referred to as a geometric waveguide. The transmissive-reflective mirror may split incident light by partially reflecting the incident light and partially transmitting the incident light, such that a portion of the incident light can continue to propagate within the waveguide to be split by other transmissive-reflective mirrors. Such a near-eye display system may be referred to as a geometric waveguide display system.

[0040] Conventional geometric waveguide displays may use a prism (as an input coupler) and two sets of geometric reflectors to direct and expand display light into the eyebox. The prism may cause chromatic dispersion, which may generally be difficult to fully compensate for by partially reflective mirrors and substrates along the optical path. According to certain embodiments disclosed herein, a geometric waveguide display may include three or four sets of geometric reflectors to achieve complete and full chromatic dispersion compensation, where display light may interact with an input mirror and an output mirror having the same mirror orientation, and may interact with a first set of intermediate mirrors and a second set of intermediate mirrors (or different regions of the same set of intermediate mirrors) that may have the same mirror orientation. The combination of multiple sets of mirrors may result in near-zero chromatic dispersion from the waveguide input to the waveguide output, and an eyebox for visible light (e.g., red, green, and blue light) from all angles. One or more input mirrors may include a single mirror with a reflectivity close to 100%, or may include a set of mirrors that includes one mirror with a reflectivity close to 100% and one or more transmissive-reflective mirrors with a reflectivity less than 100%.

[0041] In some embodiments, a near-eye display system can include a waveguide display that can include both a diffractive grating (e.g., VBG) for two-dimensional pupil expansion and a transmissive-reflective mirror. For example, the VBG or the transmissive-reflective mirror can be used to deflect display light from an input coupler (e.g., a prism, a grating, or a tilted mirror) toward a second direction at multiple positions along a first direction to expand the pupil in one dimension (e.g., the first direction). Such a VBG or transmissive-reflective mirror can be referred to herein as an intermediate grating (or a first output grating). The display light deflected toward the second direction by the intermediate grating at multiple positions can reach an output grating that can include a VBG or a transmissive-reflective mirror and can deflect an incident display beam toward an eyebox of the near-eye display system at multiple positions along a second direction, thereby expanding the pupil in a second dimension (e.g., the second direction). Such a waveguide display system can be referred to herein as a hybrid waveguide display system. The combination of the diffractive grating and the partially reflective mirror can result in a hybrid spectral and angular coverage that can be wider than the angular coverage of a VBG-based waveguide display system. This can improve the FOV and reduce undesired optical artifacts (e.g., ghost images and truncated optical line patterns).

[0042] In a geometric waveguide display system or a hybrid waveguide display system, when the transmissive-reflective mirror is used as an intermediate grating for pupil expansion in a first dimension, the transmissive-reflective mirror can typically be positioned at an angle close to 90° (e.g., approximately perpendicular to) the wide-side surface of the waveguide. Such an orientation of the transmissive-reflective mirror can make the transmissive-reflective mirror obvious to a person in front of the user because there may be a large transmittance contrast between the partially reflective region (the transmissive-reflective mirror) and the regions between the respective partially reflective regions when the person views the near-eye display system at an oblique angle, which may cause the person's eyes to perceive an obvious structure (e.g., stripes). For a waveguide display system, it is generally desirable that the optical gratings and other optical structures within or on the waveguide be as unobtrusive as possible. In addition, such an orientation of the transmissive-reflective mirror may also reduce the optical resolution of the waveguide display system because the size of the beam reflected by the transmissive-reflective mirror may be small, and thus the minimum spot size of the image on the image plane may be large.

[0043] According to some embodiments, the transmissive-reflective lenses used in the intermediate grating of a near-eye display system (e.g., a geometric waveguide display system or a hybrid waveguide display system) can be tilted at a specific angle (e.g., in the range of about 40° to 60°) with respect to the broadside surface of the waveguide. In this way, a person viewing the near-eye display system from different angles can mainly view the partially reflective regions (instead of the high transmittance gaps between the transmissive-reflective lenses), and thus can perceive a low transmittance contrast. In this way, the transmissive-reflective lenses may not be obvious to a person. Additionally, when the transmissive-reflective lenses of the intermediate grating are tilted from the surface normal direction of the broadside surface of the waveguide, the size of the light beam reflected by the transmissive-reflective lenses can be larger, so the effective optical aperture of the display system can be larger, and the optical resolution of the display system can be higher.

[0044] In one example, a waveguide display system can include an input coupler (e.g., a prism, a grating, or a tilted mirror), an intermediate light deflection structure (e.g., an intermediate grating or a first pupil expander including a plurality of VBGs or an array of transmissive-reflective lenses), and an output light deflection structure (e.g., an output grating or a second pupil expander including a plurality of VBGs or an array of transmissive-reflective lenses). The input coupler can couple display light from a projector into the waveguide. In some embodiments, the intermediate grating can include an array of transmissive-reflective lenses arranged in a first direction and tilted at an angle less than about 60° (e.g., about 45° or 50°) with respect to the broadside surface of the waveguide. Each transmissive-reflective lens in the array of transmissive-reflective lenses can deflect a portion of the incident display light to a second direction toward the output grating. The output grating can include an array of transmissive-reflective lenses or a plurality of VBGs, and can direct a portion of the incident display light beam from the intermediate grating to the eye box of the waveguide display system at each of a plurality of positions in the second direction. In some embodiments, the transmissive-reflective lenses can be used in the intermediate grating and can be tilted at an angle between about 40° and about 60° (e.g., about 45° or 50°) with respect to the broadside surface of the waveguide. In some embodiments, the transmissive-reflective lenses can be used in the output grating and can be tilted at an angle between about 25° and about 35° with respect to the broadside surface of the waveguide.

[0045] In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of various examples of the disclosure. It will be evident, however, that the various examples may be practiced without these specific details. For example, devices, systems, structures, components, methods, and other elements may be shown as components in block diagram form in order to avoid obscuring the examples in unnecessary detail. In other instances, well-known devices, processes, systems, structures, and techniques may be shown without unnecessary detail in order to avoid obscuring the examples. The figures and the description are not intended to be restrictive. The terms and phrases used in this disclosure are used as descriptive terms and not of limitation, and there is no intention, in using such terms and phrases, of excluding any equivalents or portions of the features shown and described. The word "example" as used herein means "serving as an example, instance, or illustration." Any embodiment or design described herein as an "example" is not necessarily to be construed as preferred or advantageous over other embodiments or designs.

[0046] Figure 1 FIG. is a simplified block diagram of an example of an artificial reality system environment 100 that includes a near-eye display 120 according to certain embodiments. Figure 1 The artificial reality system environment 100 shown in FIG. may include a near-eye display 120, an optional external imaging device 150, and an optional input / output interface 140, each of which may be coupled to an optional console 110. Although Figure 1 FIG. shows an example of an artificial reality system environment 100 that includes one near-eye display 120, one external imaging device 150, and one input / output interface 140, the artificial reality system environment 100 may include any number of these components, or any of these components may be omitted. For example, there may be multiple near-eye displays 120 that are monitored by one or more external imaging devices 150 that communicate with the console 110. In some configurations, the artificial reality system environment 100 may not include the external imaging device 150, the optional input / output interface 140, and the optional console 110. In alternative configurations, different components or additional components may be included in the artificial reality system environment 100.

[0047] The near-eye display 120 can be a head-mounted display that presents content to a user. Examples of content presented by the near-eye display 120 include one or more of the following: images; videos; audio; or any combination thereof. In some embodiments, the audio can be presented via an external device (e.g., speakers and / or headphones) that receives audio information from the near-eye display 120, the console 110, or both, and presents audio data based on the audio information. The near-eye display 120 can include one or more rigid bodies that can be rigidly or non-rigidly coupled to each other. A rigid coupling between multiple rigid bodies can cause the coupled rigid bodies to act as a single rigid entity. A non-rigid coupling between multiple rigid bodies can allow the rigid bodies to move relative to each other. In various embodiments, the near-eye display 120 can be implemented in any suitable form factor, including a pair of glasses. Some embodiments of the near-eye display 120 are further described below with respect to Figure 2 and Figure 3 . Additionally, in various embodiments, the functions described herein can be used for a head-mounted device that combines images of the external environment of the near-eye display 120 and artificial reality content (e.g., computer-generated images). Thus, the near-eye display 120 can utilize the generated content (e.g., images, videos, sounds, etc.) to enhance the image of the physical real-world environment external to the near-eye display 120 to present augmented reality to the user.

[0048] In various embodiments, the near-eye display 120 can include one or more of display electronics 122, display optics 124, and an eye-tracking unit 130. In some embodiments, the near-eye display 120 can further include one or more locators 126, one or more position sensors 128, and an inertial measurement unit (IMU) 132. The near-eye display 120 can omit any one of the eye-tracking unit 130, the locator 126, the position sensor 128, and the IMU 132, or in various embodiments, the near-eye display includes additional elements. Additionally, in some embodiments, the near-eye display 120 can include elements that combine the functions of the various elements described in conjunction with Figure 1 .

[0049] The display electronic device 122 can display an image to the user or facilitate the display of an image to the user based on data received from, for example, the console 110. In various embodiments, the display electronic device 122 can include one or more display panels, such as a liquid crystal display (LCD), an organic light-emitting diode (OLED) display, an inorganic light-emitting diode (ILED) display, a micro light-emitting diode (μLED) display, an active-matrix OLED (AMOLED) display, a transparent OLED (TOLED) display, or some other display. For example, in one implementation of the near-eye display 120, the display electronic device 122 can include a front TOLED panel, a rear display panel, and optical components (e.g., an attenuator, a polarizer, a diffractive film, or a spectral film) located between the front display panel and the rear display panel. The display electronic device 122 can include a plurality of pixels that emit light of a dominant color (e.g., red, green, blue, white, or yellow). In some implementations, the display electronic device 122 can display a three-dimensional (3D) image through a stereoscopic effect generated by a two-dimensional panel to create a subjective perception of the depth of the image. For example, the display electronic device 122 can include a left display in front of the user's left eye and a right display in front of the user's right eye. The left display and the right display can present horizontally shifted copies of the image relative to each other to create a stereoscopic effect (i.e., the perception of the depth of the image when the user views the image).

[0050] In some embodiments, the display optics 124 may optically display image content (e.g., using optical waveguides and couplers), or magnify the received image light from the display electronics 122, correct optical errors associated with the image light, and present the corrected image light to the user of the near-eye display 120. In various embodiments, for example, the display optics 124 may include one or more optical elements such as substrates, optical waveguides, apertures, Fresnel lenses, convex lenses, concave lenses, filters, input couplers / output couplers, or any other suitable optical element that can affect the image light emitted from the display electronics 122. The display optics 124 may include a combination of different optical elements and a plurality of mechanical connectors for maintaining the relative spacing and orientation of these optical elements in the combination. One or more of the optical elements in the display optics 124 may have an optical coating, such as an anti-reflection coating, a reflective coating, a filtering coating, or a combination of different optical coatings.

[0051] The magnification of the image light by the display optics 124 may allow the display electronics 122 to be physically smaller, lighter, and consume less power compared to a larger display. Additionally, the magnification may increase the field of view of the displayed content. The amount of magnification of the image light by the display optics 124 may be changed by adjusting the optical elements, adding optical elements, or removing optical elements from the display optics 124. In some embodiments, the display optics 124 may project the displayed image onto one or more image planes that may be further away from the user's eyes than the near-eye display 120.

[0052] The display optics 124 may also be designed to correct one or more types of optical errors, such as two-dimensional optical errors, three-dimensional optical errors, or any combination thereof. Two-dimensional errors may include optical aberrations that occur in two dimensions. Example types of two-dimensional errors may include barrel distortion, pincushion distortion, longitudinal chromatic aberration, and lateral chromatic aberration. Three-dimensional errors may include optical errors that occur in three dimensions. Example types of three-dimensional errors may include spherical aberration, coma aberration, field curvature, and astigmatism.

[0053] Multiple locators 126 can be objects at multiple specific positions on the near-eye display 120 that are related to each other and to a reference point on the near-eye display 120. In some embodiments, the console 110 can identify the locators 126 in the multiple images captured by the external imaging device 150 to determine the position, orientation, or both the position and orientation of the artificial reality headset. The locators 126 can be light-emitting diodes (LEDs), corner cube reflectors, reflective markers, a class of light sources that contrast with the environment in which the near-eye display 120 operates, or any combination thereof. In embodiments where the locators 126 are active components (e.g., LEDs or other types of light-emitting devices), the locators 126 can emit light in the visible light band (e.g., from about 380 nm to 750 nm), in the infrared (IR) band (e.g., from about 750 nm to 1 mm), in the ultraviolet band (e.g., from about 12 nm to about 380 nm), or in another part of the electromagnetic spectrum, or in any combination of multiple parts of the electromagnetic spectrum.

[0054] The external imaging device 150 can include one or more cameras, one or more video cameras, any other device capable of capturing images including one or more of the locators 126, or any combination thereof. Additionally, the external imaging device 150 can include one or more filters (e.g., to improve the signal-to-noise ratio). The external imaging device 150 can be configured to detect light emitted or reflected from the locators 126 in the field of view of the external imaging device 150. In embodiments where the locators 126 include passive elements (e.g., retroreflectors), the external imaging device 150 can include a light source that irradiates some or all of the locators 126, which can reflect the light back to the light source in the external imaging device 150. Slow calibration data can be transferred from the external imaging device 150 to the console 110, and the external imaging device 150 can receive one or more calibration parameters from the console 110 to adjust one or more imaging parameters (e.g., focal length, focus, frame rate, sensor temperature, shutter speed, aperture, etc.).

[0055] The position sensor 128 can generate one or more measurement signals in response to the movement of the near-eye display 120. Examples of the position sensor 128 can include accelerometers, gyroscopes, magnetometers, other motion detection or error correction sensors, or any combination thereof. For example, in some embodiments, the position sensor 128 can include multiple accelerometers for measuring translational motion (e.g., forward / backward, up / down, left / right) and multiple gyroscopes for measuring rotational motion (e.g., pitch, yaw, roll). In some embodiments, the various position sensors can be oriented orthogonally to each other.

[0056] The IMU 132 can be an electronic device that generates fast calibration data based on measurement signals received from one or more of the plurality of position sensors 128. The plurality of position sensors 128 can be located outside the IMU 132, inside the IMU 132, or any combination thereof. The IMU 132 can generate fast calibration data based on one or more measurement signals from one or more of the position sensors 128, the fast calibration data indicating an estimated position of the near-eye display 120 relative to an initial position of the near-eye display 120. For example, the IMU 132 can integrate the received measurement signals from the accelerometer over time to estimate a velocity vector, and integrate the velocity vector over time to determine an estimated position of a reference point on the near-eye display 120. Alternatively, the IMU 132 can provide sampled measurement signals to the console 110, which can determine the fast calibration data. While the reference point can generally be defined as a point in space, in various embodiments, the reference point can also be defined as a point within the near-eye display 120 (e.g., the center of the IMU 132).

[0057] The eye tracking unit 130 can include one or more eye tracking systems. Eye tracking can refer to determining the position of the eyes relative to the near-eye display 120, including the orientation and positioning of the eyes. The eye tracking system can include an imaging system for imaging one or more eyes, and can optionally include a light emitter that can generate light directed at the eyes such that the light reflected by the eyes can be collected by the imaging system. For example, the eye tracking unit 130 can include an incoherent light source or a coherent light source (e.g., a laser diode) that emits light within the visible spectrum or the infrared spectrum, and a camera that collects the light reflected by the user's eyes. As another example, the eye tracking unit 130 can collect reflected radio waves emitted by a micro radar unit. The eye tracking unit 130 can use a low-power light emitter that emits light at a frequency and intensity that does not harm the eyes or cause physical discomfort. The eye tracking unit 130 can be configured to increase the contrast in the images of the eyes collected by the eye tracking unit 130 while reducing the total power consumed by the eye tracking unit 130 (e.g., reducing the power consumed by the light emitter and the imaging system included in the eye tracking unit 130). For example, in some implementations, the eye tracking unit 130 can consume less than 120 milliwatts of power.

[0058] The near-eye display 120 can use the orientation of the eyes to, for example, determine the user's inter-pupillary distance (IPD), determine the gaze direction, introduce depth cues (e.g., blurring images outside the user's primary line of sight), gather heuristic information on user interactions in VR media (e.g., the time spent on any particular subject, object, or frame based on the stimuli experienced), some other function partially based on the orientation of at least one of the user's eyes, or any combination thereof. Since the orientation can be determined for both of the user's eyes, the eye tracking unit 130 can be capable of determining where the user is looking. For example, determining the user's gaze direction can include: determining the convergence point based on the determined orientations of the user's left and right eyes. The convergence point can be the point where the two foveal axes of the user's eyes intersect. The user's gaze direction can be the direction of the line passing through the convergence point and the midpoint between the pupils of the user's eyes.

[0059] The input / output interface 140 can be a device that allows the user to send action requests to the console 110. The action request can be a request to perform a particular action. For example, the action request can be to start an application or end an application, or to perform a particular action within an application. The input / output interface 140 can include one or more input devices. Example input devices can include a keyboard, a mouse, a game controller, gloves, buttons, a touch screen, or any other suitable device for receiving an action request and transmitting the received action request to the console 110. The action request received by the input / output interface 140 can be transmitted to the console 110, which can perform an action corresponding to the requested action. In some embodiments, the input / output interface 140 can provide haptic feedback to the user according to instructions received from the console 110. For example, the input / output interface 140 can provide haptic feedback when the action request is received, or when the console 110 has performed the requested action and transmitted instructions to the input / output interface 140. In some embodiments, the external imaging device 150 can be used to track the input / output interface 140, such as tracking the positioning or location of a controller (which can include, for example, an IR light source), or tracking the positioning or location of the user's hand to determine the user's action. In some embodiments, the near-eye display 120 can include one or more imaging devices for tracking the input / output interface 140, such as tracking the positioning or location of a controller, or tracking the positioning or location of the user's hand to determine the user's action.

[0060] The console 110 can provide content to the near-eye display 120 for presentation to the user based on information received from one or more of the external imaging device 150, the near-eye display 120, and the input / output interface 140. InFigure 1 In the example shown, the console 110 may include an application repository 112, a head-mounted device tracking subsystem 114, an artificial reality engine 116, and an eye tracking subsystem 118. Some embodiments of the console 110 may include subsystems different from those described in connection with Figure 1 those subsystems or additional subsystems in addition to those described in connection with Figure 1 those subsystems. The functions described further below may be distributed among the components of the console 110 in a manner different from the manner described herein.

[0061] In some embodiments, the console 110 may include a processor and a non-transitory computer-readable storage medium that stores instructions executable by the processor. The processor may include multiple processing units that execute instructions in parallel. The non-transitory computer-readable storage medium may be any memory, such as a hard disk drive, a removable memory, or a solid state drive (e.g., flash memory, or dynamic random access memory (DRAM)). In various embodiments, the devices and subsystems of the console 110 described in connection with Figure 1 may be encoded as instructions in the non-transitory computer-readable storage medium, which, when executed by the processor, cause the processor to perform the functions described further below.

[0062] The application repository 112 may store one or more applications for execution by the console 110. The application may include a set of instructions that, when executed by the processor, generate content for presentation to the user. The content generated by the application may be responsive to input received from the user via movement of the user's eyes or responsive to input received from the input / output interface 140. Examples of applications may include game applications, conferencing applications, video playback applications, or other suitable applications.

[0063] The head-mounted device tracking subsystem 114 can use slow calibration information from an external imaging device 150 to track the movement of the near-eye display 120. For example, the head-mounted device tracking subsystem 114 can use the observed locators from the slow calibration information and a model of the near-eye display 120 to determine the position of the reference point of the near-eye display 120. The head-mounted device tracking subsystem 114 can also use position information from the fast calibration information to determine the position of the reference point of the near-eye display 120. Additionally, in some embodiments, the head-mounted device tracking subsystem 114 can use multiple portions of the following to predict the future position of the near-eye display 120: fast calibration information; slow calibration information; or any combination thereof. The head-mounted device tracking subsystem 114 can provide the estimated or predicted future position of the near-eye display 120 to the artificial reality engine 116.

[0064] The artificial reality engine 116 can execute applications within the artificial reality system environment 100 and receive the position information of the near-eye display 120, the acceleration information of the near-eye display 120, the velocity information of the near-eye display 120, the predicted future position of the near-eye display 120, or any combination thereof from the head-mounted device tracking subsystem 114. The artificial reality engine 116 can also receive the estimated eye position and orientation information from the eye tracking subsystem 118. Based on the received information, the artificial reality engine 116 can determine the content to be provided to the near-eye display 120 for presentation to the user. For example, if the received information indicates that the user has looked to the left, the artificial reality engine 116 can generate content for the near-eye display 120 that reflects the user's eye movement in the virtual environment. Additionally, the artificial reality engine 116 can execute an action within an application executed on the console 110 in response to an action request received from the input / output interface 140 and provide feedback to the user indicating that the action has been executed. The feedback can be visual feedback or auditory feedback via the near-eye display 120, or tactile feedback via the input / output interface 140.

[0065] The eye tracking subsystem 118 can receive eye tracking data from the eye tracking unit 130 and determine the position of the user's eyes based on the eye tracking data. The position of the eyes can include the orientation, position, or both of the eyes relative to the near-eye display 120 or any element of the near-eye display. Since the axis of rotation of the eyes changes as the eyes move in their sockets, determining the position of the eyes in their sockets can allow the eye tracking subsystem 118 to more accurately determine the orientation of the eyes.

[0066] Figure 2A perspective view of an example of a near-eye display in the form of an HMD device 200 that implements some examples of the various examples disclosed herein. The HMD device 200 can be part of, for example, a VR system, an AR system, an MR system, or any combination thereof. The HMD device 200 can include a body 220 and a headband 230. Figure 2 The bottom side 223, front side 225, and left side 227 of the body 220 are shown in perspective. The headband 230 can have an adjustable or extendable length. There can be sufficient space between the body 220 of the HMD device 200 and the headband 230 to allow a user to wear the HMD device 200 on the user's head. In various embodiments, the HMD device 200 can include additional, fewer, or different components. For example, in some embodiments, the HMD device 200 can include, for example, the following Figure 3 shown eyeglass temples and temple tips instead of the headband 230.

[0067] The HMD device 200 can present media to a user, the media including a virtual view and / or an augmented view of a physically real-world environment with computer-generated elements. Examples of media presented by the HMD device 200 can include images (e.g., two-dimensional (2D) images or three-dimensional (3D) images), videos (e.g., 2D videos or 3D videos), audio, or any combination thereof. The images and videos can be presented to each eye of the user through one or more display components ( Figure 2 not shown) enclosed in the body 220 of the HMD device 200. In various embodiments, the one or more display components can include a single electronic display panel or multiple electronic display panels (e.g., one display panel for each eye of the user). Examples of one or more electronic display panels can include, for example, LCD, OLED displays, ILED displays, μLED displays, AMOLED displays, TOLED displays, some other display, or any combination thereof. The HMD device 200 can include two ocular frame regions.

[0068] In some embodiments, the HMD device 200 may include various sensors (not shown), such as depth sensors, motion sensors, position sensors, and eye-tracking sensors. Some of these sensors may sense using structured light patterns. In some embodiments, the HMD device 200 may include an input / output interface for communicating with a console. In some embodiments, the HMD device 200 may include a virtual reality engine (not shown) that may execute applications within the HMD device 200 and receive depth information, position information, acceleration information, velocity information, predicted future positions, or any combination thereof of the HMD device 200 from various sensors. In some embodiments, the information received by the virtual reality engine may be used to generate signals (e.g., display instructions) to one or more display components. In some embodiments, the HMD device 200 may include locators (not shown, such as locator 126) that are located at fixed positions relative to each other and relative to a reference point on the body 220. Each of these locators may emit light detectable by an external imaging device.

[0069] Figure 3 FIG. is a perspective view of an example of a near-eye display 300 in the form of a pair of glasses for implementing some examples of the various examples disclosed herein. The near-eye display 300 may be Figure 1 a specific implementation of the near-eye display 120 and may be configured to operate as a virtual reality display, an augmented reality display, and / or a mixed reality display. The near-eye display 300 may include a frame 305 and a display 310. The display 310 may be configured to present content to a user. In some embodiments, the display 310 may include display electronics and / or display optics. For example, as described above with respect to Figure 1 the near-eye display 120, the display 310 may include an LCD display panel, an LED display panel, or an optical display panel (e.g., a waveguide display assembly).

[0070] The near-eye display 300 may also include various sensors 350a, 350b, 350c, 350d, and 350e located on or within the frame 305. In some embodiments, the sensors 350a to 350e may include one or more depth sensors, one or more motion sensors, one or more position sensors, one or more inertial sensors, or one or more ambient light sensors. In some embodiments, the sensors 350a to 350e may include one or more image sensors configured to generate image data representing different fields of view in different directions. In some embodiments, the sensors 350a to 350e may be used as input devices for controlling or influencing the display content of the near-eye display 300 and / or providing an interactive VR / AR / MR experience to the user of the near-eye display 300. In some embodiments, the sensors 350a to 350e may also be used for stereoscopic imaging.

[0071] In some embodiments, the near-eye display 300 may also include one or more illuminators 330 for projecting light into the physical environment. The projected light may be associated with different frequency bands (e.g., visible light, infrared light, ultraviolet light, etc.), and the projected light may be used for various purposes. For example, one or more illuminators 330 may project light in a dark environment (or in an environment with low-intensity infrared light, ultraviolet light, etc.) to help the sensors 350a to 350e capture images of different objects in the dark environment. In some embodiments, one or more illuminators 330 may be used to project certain light patterns onto multiple objects within the environment. In some embodiments, one or more illuminators 330 may be used as locators, such as the locator 126 described above with respect to Figure 1 the locator 126.

[0072] In some embodiments, the near-eye display 300 may also include a high-resolution camera 340. The high-resolution camera 340 may capture an image of the physical environment in the field of view. The captured image may be processed, for example, by a virtual reality engine (e.g., Figure 1 the artificial reality engine 116) to add virtual objects to the captured image or modify physical objects in the captured image, and the processed image may be displayed by the display 310 to the user for AR applications or MR applications.

[0073] Figure 4FIG. 0 shows an example of an optical see-through augmented reality system 400 including a waveguide display in accordance with some embodiments. The augmented reality system 400 may include a projector 410 and a combiner 415. The projector 410 may include a light source or image source 412 and projector optics 414. In some embodiments, the light source or image source 412 may include one or more of the above-described micro-LED devices. In some embodiments, the image source 412 may include a plurality of pixels that display virtual objects, such as an LCD display panel or an LED display panel. In some embodiments, the image source 412 may include a light source that generates coherent light or partially coherent light. For example, the image source 412 may include a laser diode, a vertical cavity surface emitting laser, an LED, and / or a micro-LED as described above. In some embodiments, the image source 412 may include a plurality of light sources (e.g., an array of the above-described micro-LEDs), each light source emitting monochromatic image light corresponding to a primary color (e.g., red, green, or blue). In some embodiments, the image source 412 may include three two-dimensional micro-LED arrays, where each two-dimensional micro-LED array may include micro-LEDs configured to emit primary color light (e.g., red, green, or blue). In some embodiments, the image source 412 may include an optical pattern generator, such as a spatial light modulator. The projector optics 414 may include one or more optical components that may condition light from the image source 412, such as expanding, collimating, scanning, or projecting the light from the image source 412 onto the combiner 415. The one or more optical components may include, for example, one or more lenses, one or more liquid lenses, one or more mirrors, one or more apertures, and / or one or more gratings. For example, in some embodiments, the image source 412 may include one or more one-dimensional micro-LED arrays or elongated two-dimensional micro-LED arrays, and the projector optics 414 may include one or more one-dimensional scanners (e.g., micromirrors or prisms) configured to scan the one-dimensional micro-LED arrays or the elongated two-dimensional micro-LED arrays to generate image frames. In some embodiments, the projector optics 414 may include a liquid lens (e.g., a liquid crystal lens) having a plurality of electrodes that allow scanning of the light from the image source 412.

[0074] The combiner 415 may include an input coupler 430 that is configured to couple light from the projector 410 into the substrate 420 of the combiner 415. The combiner 415 may transmit light in a first wavelength range (e.g., visible light from about 400 nm to about 650 nm). The input coupler 430 may include a volume holographic grating, a diffractive optical element (DOE) (e.g., a surface relief grating), an inclined surface of the substrate 420, or a refractive coupler (e.g., a wedge or a prism). For example, the input coupler 430 may include a reflective volume Bragg grating or a transmissive volume Bragg grating. For visible light, the input coupler 430 may have a coupling efficiency greater than 30%, 50%, 75%, 90% or higher. The light coupled into the substrate 420 may propagate within the substrate 420 by, for example, total internal reflection (TIR). The substrate 420 may be in the form of a lens of a pair of glasses. The substrate 420 may have a flat surface or a curved surface and may include one or more types of dielectric materials such as glass, quartz, plastic, polymer, poly(methyl methacrylate) (PMMA), crystal or ceramic. The thickness of the substrate may be in a range, for example, less than about 1 mm to about 12 mm or greater. The substrate 420 may be transmissive to visible light.

[0075] The substrate 420 may include or be coupled to a plurality of output couplers 440, each output coupler being configured to extract at least a portion of the light guided by and propagating within the substrate 420 from the substrate 420 and direct the extracted light 460 towards the eyepiece 495, wherein when the augmented reality system 400 is in use, the eyes 490 of a user of the augmented reality system 400 may be located within the eyepiece. The plurality of output couplers 440 may replicate the exit pupil to increase the size of the eyepiece 495 such that the displayed image is visible over a larger area. Similar to the input coupler 430, the output coupler 440 may include a grating coupler (e.g., a volume holographic grating or a surface relief grating), other diffractive optical elements, a prism, etc. For example, the output coupler 440 may include a reflective volume Bragg grating or a transmissive volume Bragg grating. The output coupler 440 may have different coupling (e.g., diffraction) efficiencies at different locations. The substrate 420 may also allow light 450 from the environment in front of the combiner 415 to pass through with little or no loss. The output coupler 440 may also allow light 450 to pass through with little loss. For example, in some embodiments, the output coupler 440 may have a very low diffraction efficiency for light 450 such that the light 450 may be refracted or otherwise pass through the output coupler 440 with little loss, and thus may have a higher intensity than the extracted light 460. In some embodiments, the output coupler 440 may have a high diffraction efficiency for light 450 and may diffract the light 450 with little loss along certain desired directions (i.e., diffraction angles). Accordingly, a user may be able to view a combined image of the environment in front of the combiner 415 and an image of a virtual object projected by the projector 410.

[0076] In some embodiments, the projector 410, the input coupler 430, and the output coupler 440 may be located on either side of the substrate 420. The input coupler 430 and the output coupler 440 may be reflective gratings (also referred to as reflective gratings) or transmissive gratings (also referred to as transmissive gratings) to couple display light into or out of the substrate 420.

[0077] Figure 5 An example of an optical see-through augmented reality system 500 including a waveguide display for exit pupil expansion is shown in accordance with certain embodiments. The augmented reality system 500 may be similar to the augmented reality system 400 and may include a waveguide display and a projector, the projector including a light source or image source 510 and projector optics 520. The waveguide display may include a substrate 530, an input coupler 540, and a plurality of output couplers 550 as described above with respect to the augmented reality system 500. Although Figure 5 only the propagation of light from a single field of view is shown, Figure 5 the propagation of light from multiple fields of view is shown.

[0078] Figure 5 It is shown that the exit pupil is replicated by a plurality of output couplers 550 to form an aggregated exit pupil or eye box, where different regions in the field of view (e.g., different pixels on the image source 510) can be associated with different respective propagation directions towards the eye box, and light from the same field of view (e.g., the same pixel on the image source 510) can have the same propagation direction for different individual exit pupils. Thus, a single image of the image source 510 can be formed by the user's eye located at any position within the eye box, where light from different individual exit pupils and propagating in the same direction can be from the same pixel on the image source 510 and can be focused to the same position on the retina of the user's eye. In other words, the user's eye can convert the angular information (e.g., corresponding to the Fourier plane) in the eye box or exit pupil into spatial information in the form of an image on the retina. Figure 5 It is shown an image of the image source that is visible to the user's eye even when the user's eye moves to different positions within the eye box.

[0079] Figure 6A An example of a waveguide display system 600 is shown that includes a waveguide (e.g., including one or more substrates) and a diffraction grating for exit pupil expansion. The waveguide display system 600 can include a substrate 610, which can be similar to the substrate 530 and can serve as a waveguide for guiding light by total internal reflection. The substrate 610 can be transmissive to visible light and can include, for example, a glass substrate, a quartz substrate, a plastic substrate, a polymer substrate, a PMM substrate A, a ceramic substrate, a silicon nitride (Si3N4) substrate, or a crystal substrate. The substrate 610 can be a flat substrate or a curved substrate and can include a single layer of material or can include a layer stack. The substrate 610 can include a first wide side surface 612 and a second wide side surface 614.

[0080] In the example shown, waveguide display system 600 may further include an input coupler 620, an intermediate grating 630, and an output grating 640. Input coupler 620, intermediate grating 630, and output grating 640 may be formed on or in substrate 610. Input coupler 620 may include a grating, a refractive coupler (e.g., an optical wedge or prism), or a reflective coupler (e.g., an angled reflective surface). For example, in one embodiment, input coupler 620 may include a prism that can couple display light of different colors and for different fields of view into substrate 610 by refraction. In another example, input coupler 620 may include a grating coupler that can diffract light of different colors into substrate 610 at different angles. For visible light, input coupler 620 may have a coupling efficiency greater than 12%, 20%, 30%, 50%, 75%, 90%, or higher. In some embodiments, waveguide display system 600 may include projection optics (e.g., lenses, Figure 6A not shown), where display light from an image source may be collimated by the projection optics and projected onto input coupler 620, which may then couple the display light into substrate 610 by diffraction, refraction, or reflection. The light coupled into substrate 610 may be reflected by first wide side surface 612 and second wide side surface 614 by total internal reflection such that the display light can propagate within substrate 610.

[0081] Intermediate grating 630 and output grating 640 may be positioned on one or both surfaces (e.g., first wide side surface 612 and second wide side surface 614) of substrate 610 for expanding the incident display beam in two dimensions to fill the eyebox with display light. Intermediate grating 630 may be configured to expand the display light in one direction (e.g., approximately in the x direction). Then, output grating 640 may cause the display light from intermediate grating 630 to expand in different directions (e.g., approximately in the y direction).

[0082] For example, as Figure 6A shown, the display light coupled into substrate 610 and propagating within substrate 610 may reach a first portion 632 of intermediate grating 630 and may be diffracted by first portion 632 of intermediate grating 630 to change the propagation direction to a first direction (e.g., approximately the x direction) toward a second portion 634 of intermediate grating 630. As Figure 6AAs shown, when the display light propagates in the substrate 610 in the first direction, whenever the display light propagating in the substrate 610 reaches the second portion 634 of the intermediate grating 630, a portion of the display light can be diffracted by the region of the second portion 634 of the intermediate grating 630 towards the output grating 640. Then, whenever the display light propagating in the substrate 610 reaches the output grating 640, the output grating 640 can diffract a portion of the display light into the eyebox to expand the display light from the intermediate grating 630 in different directions (e.g., approximately in the y direction). Thus, the intermediate grating 630 and the output grating 640 can replicate the incident display light beam in two dimensions to fill the eyebox with the display light.

[0083] Figure 6B An example of an eyebox including a two-dimensionally replicated exit pupil is shown. Figure 6B It is shown that a single input pupil 605 can be replicated by the intermediate grating 630 and the output grating 640 to form a collective exit pupil 660 including a two-dimensional array of individual exit pupils 662. For example, the exit pupil can be replicated by the intermediate grating 630 in the approximately x direction and by the output grating 640 in the approximately y direction. As described above, the output light from the individual exit pupils 662 and propagating in the same direction can be focused onto the same point on the retina of the user's eye. Thus, the user's eye can use the output light in the two-dimensional array of individual exit pupils 662 to form a single image.

[0084] In some embodiments, the first portion 632 and the second portion 634 of the intermediate grating 630 may be located on the same holographic material layer and may have matching grating vectors (e.g., the same grating vectors in the x-y plane and the same and / or opposite grating vectors in the z direction). Since the diffraction at the first portion 632 and the second portion 634 of the intermediate grating 630 has opposite Bragg conditions (e.g., +1 order diffraction and -1 order diffraction), the first portion 632 and the second portion 634 may compensate for the chromatic dispersion caused by each other to reduce the overall chromatic dispersion. Additionally, the input grating of the input coupler 620 and the output grating 640 may have matching grating vectors (e.g., the same grating vectors in the x-y plane and the same or opposite grating vectors in the z direction), where the input grating may couple display light into the substrate 610, and the output grating 640 may couple display light out of the substrate 610. Since the diffraction at the input coupler 620 and the output grating 640 has opposite diffraction directions and opposite Bragg conditions (e.g., +1 order diffraction and -1 order diffraction), the input coupler 620 and the output grating 640 may compensate for the chromatic dispersion caused by each other to reduce the overall dispersion. In this way, the chromatic dispersion of the first portion 632 and the second portion 634 of the intermediate grating 630 can be canceled out, and the dispersion of the input grating of the input coupler 620 and the output grating 640 can also be canceled out. Thus, the overall chromatic dispersion of the waveguide display system 600 for the display light can be minimized. In this way, a higher resolution of the displayed image can be achieved.

[0085] Each of the input grating in the input coupler 620, the first portion 632 and the second portion 634 of the intermediate grating 630, and the output grating 640 may include multiplexed VBGs configured to diffract display light of different colors and / or from different fields of view. Since each VBG in the plurality of multiplexed VBGs may have a limited wavelength and / or angular bandwidth, different VBGs with different wavelength and / or angular bandwidths may be used to diffract different color components of the display light and / or display light from different fields of view. However, the total refractive index modulation achievable in the holographic material layer may be limited. Thus, a limited number of VBGs may be recorded in the holographic material layer, and the overall diffraction efficiency of the waveguide display system 600 based on VBGs may be low and / or the field of view of the waveguide display system 600 based on VBGs may be small.

[0086] Figure 7A A curve 710 showing an example of the angular bandwidth of a VBG (e.g., a transmissive VBG). Figure 7A The horizontal axis in represents the deviation of the incident angle of visible light from the central (nominal) incident angle (Bragg angle) of the VBG design. Figure 7AThe vertical axis therein represents the corresponding diffraction efficiency. As shown by curve 710, the diffraction efficiency of the VBG may be relatively high only for light incident on the grating from a narrow angular range near the ideal Bragg condition (Bragg angle). Although not shown in Figure 7A , the diffraction efficiency of the VBG may also be relatively high only for incident light within a narrow wavelength range near the ideal Bragg condition.

[0087] Accordingly, an optical see-through near-eye display system that employs a waveguide and a diffraction grating (e.g., a volume Bragg grating (VBG)) to present a display image from a projector to a user's eye may have a limited field of view (FOV) and spectral coverage due to, e.g., the limited angular and spectral bandwidths of the diffraction grating. For example, some diffraction gratings (e.g., VBGs) may have a limited diffraction efficiency due to the limited achievable refractive index modulation of the holographic recording material. Additionally, as described above with respect to Figure 6A , multiple gratings for one-dimensional or two-dimensional pupil expansion may perform multiple optical filtering on the display image (e.g., Bragg filtering due to the limited bandwidth of the VBG), which may result in optical artifacts (e.g., truncated optical line patterns) that may degrade the quality of the display image. Additionally, the diffraction grating may have a large dispersion between lights of different colors and may have different diffraction angles for lights of different colors. Accordingly, different color components in a color image displayed by the near-eye display system may not overlap with each other. As a result, the quality of the display image (e.g., resolution, contrast, and / or color reproduction neutrality) may be degraded. Additionally, due to the dispersion of light and the limited range of the wave vectors of the light that can be guided by the waveguide display, the FOVs of different colors may be reduced or partially cut off.

[0088] In some embodiments, an optical see-through near-eye display system may include a waveguide in which one or more partially reflective mirror arrays are embedded at multiple locations within the waveguide to direct the display image from the multiple locations to the user's eye, thereby replicating the exit pupil and expanding the eyebox in one dimension or two dimensions. The partially reflective mirror may also be referred to as a transmissive-reflective mirror, a geometric mirror, or a geometric reflector. A waveguide that includes a transmissive-reflective mirror therein may be referred to as a geometric waveguide. The transmissive-reflective mirror may split the incident light by partially reflecting and partially transmitting the incident light such that a portion of the incident light may continue to propagate within the waveguide to be split by other transmissive-reflective mirrors. Such a near-eye display system may be referred to as a geometric waveguide display system.

[0089] In some embodiments, a near-eye display system can include a waveguide display that can include both a diffraction grating (e.g., VBG) for two-dimensional pupil expansion and a transmissive-reflective mirror. For example, the VBG or the transmissive-reflective mirror can be used to deflect display light from an input coupler (e.g., a prism, a grating, or a tilted mirror) toward a second direction at multiple positions along a first direction to expand the pupil in one dimension (e.g., the first direction). Such a VBG or transmissive-reflective mirror can be referred to herein as an intermediate grating (or a first output grating). The display light deflected toward the second direction by the intermediate grating at multiple positions can reach an output grating that can include a VBG or a transmissive-reflective mirror and can deflect an incident display light beam toward an eyebox of the near-eye display system at multiple positions along a second direction, thereby expanding the pupil in a second dimension (e.g., the second direction). Such a waveguide display system can be referred to herein as a hybrid waveguide display system. The combination of the diffraction grating and the partially reflective mirror can result in a hybrid spectral and angular coverage that can be wider than the angular coverage of a VBG-based waveguide display system. This can improve the FOV and reduce undesired optical artifacts (e.g., ghost images and truncated optical line patterns).

[0090] Each transmissive-reflective mirror used in a geometric waveguide display system or a hybrid waveguide display system can include, for example, multiple dielectric coatings, one or more metal coatings, or a combination of dielectric coatings and metal coatings. For example, a transmissive-reflective mirror can include multiple dielectric coatings coated on a substrate, where the multiple dielectric coatings can include two or more different transparent dielectric materials having different refractive indices. The number of dielectric coatings and the refractive index and thickness of each dielectric coating can be selected to achieve desired performance, such as a desired reflectance (reflection efficiency) and polarization performance. Multiple substrates on which multiple transmissive-reflective mirrors are formed can be stacked and bonded (e.g., glued) together using, for example, an optically transparent adhesive. The bonded stack can be cut at a specific angle to form one or more geometric waveguides, each including multiple transmissive-reflective mirrors embedded therein. Different transmissive-reflective mirrors among the multiple transmissive-reflective mirrors can have different reflection efficiencies. For example, the reflectance of a first transmissive-reflective mirror that receives coupled-in display light can be lower than the reflectance of a second transmissive-reflective mirror before the second transmissive-reflective mirror, such that the portion of the display light reflected by the first transmissive-reflective mirror can have an intensity similar to the portion of the display light reflected by the second transmissive-reflective mirror.

[0091] Figure 7B Curve 720 showing an example of the angular bandwidth of a transmissive-reflective mirror. Figure 7BThe horizontal axis therein represents the deviation of the incident angle of visible light from the central (nominal) incident angle of the transmissive-reflective lens, and the vertical axis represents the corresponding reflectance. In the example shown by curve 720, for light incident on the grating from a wide angular range near the central (nominal) incident angle, the reflectance of the transmissive-reflective lens can be close to 50% (semi-reflective and semi-transmissive). For example, the full width at half maximum (FWHM) reflection angle range of the transmissive-reflective lens can be greater than 40° or higher. Although not shown in Figure 7B , for incident light in a wide wavelength range, the reflectance of the transmissive-reflective lens can also be high.

[0092] As Figure 7B indicated, a geometric waveguide display system or a hybrid waveguide display system using a transmissive-reflective lens can achieve a large FOV, and can also have minimal dispersion or no dispersion, as well as good image resolution and quality. However, a geometric waveguide display system may be difficult to manufacture and / or costly, and may be difficult to achieve uniform light intensity within the eye box. Imprecision in the process of manufacturing individual transmissive-reflective lenses, stacking and bonding substrates coated with transmissive-reflective lenses, and cutting substrates with transmissive-reflective lenses at a specific angle to form a geometric waveguide may result in defects in the displayed image, such as black lines, brightness non-uniformity, and ghost images, etc. For example, some geometric waveguide display systems may have problems with ghost stray rays and double imaging, which may reduce the display quality. Some geometric waveguide display systems may only achieve one-dimensional pupil expansion.

[0093] A geometric waveguide typically can include a prism (as an input coupler) and two sets of geometric reflectors to guide and expand the display light into the eye box. The prism may cause dispersion, which generally may be difficult to fully compensate for by partial reflective mirrors and substrates along the optical path. According to certain embodiments disclosed herein, a geometric waveguide display can include three or four sets of geometric reflectors to achieve complete and full dispersion compensation, wherein the display light can interact with an input mirror and an output mirror having the same mirror orientation, and can interact with a first set of intermediate mirrors and a second set of intermediate mirrors (or different regions of the same set of intermediate mirrors) that may have the same mirror orientation. The combination of multiple sets of mirrors can produce near-zero dispersion from the waveguide input to the waveguide output, as well as an eye box for visible light from all angles (e.g., red, green, blue). One or more input mirrors can include a single mirror with a reflectance close to 100%, or can include a set of mirrors that includes one mirror with a reflectance close to 100% and one or more transmissive-reflective lenses with a reflectance lower than 100%.

[0094] Figure 8AShows an example of a waveguide display 800 according to some embodiments that includes three or four sets of mirrors and / or transmissive mirrors for two-dimensional pupil expansion and dispersion compensation. The waveguide display 800 may be similar to the waveguide display 600, but may use mirrors or transmissive mirrors (instead of refractive or diffractive optical components) in place of the input coupler 620, the intermediate grating 630, and the output grating 640. In Figure 8A the example shown, the waveguide display 800 may include an input coupler 810, which may include one or more mirrors and / or transmissive mirrors and may be referred to as an input mirror. The input mirror may be used to couple display light into the waveguide 802 such that the display light can propagate within the waveguide 802 by total internal reflection.

[0095] The waveguide display 800 may include an intermediate mirror 820, which may include a set of mirrors and / or transmissive mirrors having the same orientation. One or more mirrors and / or transmissive mirrors of the intermediate mirror 820 may be used to direct the display light from the input coupler 810 toward other mirrors and / or transmissive mirrors of the intermediate mirror 820, which may replicate the pupil in a first dimension (e.g., approximately the x direction) by reflecting portions of the display light at multiple positions along the first dimension, as Figure 8A shown. For example, the first and last mirrors (e.g., in the x direction) in the intermediate mirror 820 may be mirrors with a reflectivity close to 100%, and the mirrors between the first and last mirrors in the intermediate mirror 820 may be transmissive mirrors with a reflectivity less than 100% and partial transmission.

[0096] In some embodiments, the intermediate mirror 820 may include a first intermediate mirror 822 and a second intermediate mirror 824. The first intermediate mirror 822 may include one or more mirrors and / or transmissive mirrors that can direct the display light from the input coupler 810 to the second intermediate mirror 824. For example, the first mirror (e.g., in the x direction) in the first intermediate mirror 822 may be a mirror with a reflectivity close to 100%, and the other mirrors in the first intermediate mirror 822 may be transmissive mirrors with partial transmission. The second intermediate mirror 824 may include multiple mirrors and / or transmissive mirrors and may expand the pupil in a first dimension (e.g., approximately the x direction) by reflecting portions of the display light at multiple positions along the first dimension, as Figure 8A shown. In one example, the last mirror (e.g., in the x direction) in the second intermediate mirror 824 may be a mirror with a reflectivity close to 100%, and the other mirrors in the second intermediate mirror 824 may be transmissive mirrors with partial transmission.

[0097] The waveguide display 800 may further include an output mirror 830, which may include multiple mirrors and / or transmissive mirrors. As described above with respect to Figure 6A andFigure 6B as described and shown in Figure 8A In the output mirror 830 shown in Figure 8A , a plurality of transmissive-reflective mirrors can reflect part of the display light from each of a plurality of positions in the intermediate mirror 820 to the eyewear frame at a plurality of positions along a second dimension (e.g., approximately the y-direction) to replicate the exit pupil in the second dimension. Thus, the intermediate mirror 820 and the output mirror 830 can replicate the pupil in two dimensions to fill the eyewear frame. In one example, the last mirror (e.g., in the y-direction) in the output mirror 830 can be a mirror with a reflectivity close to 100%, and the other mirrors in the output mirror 830 can be partially transmissive transmissive-reflective mirrors.

[0098] As Figure 8A shown in Figure 8A , the input coupler 810 and the output mirror 830 can have the same or similar orientations and can reflect light in opposite ways (e.g., into or out of the waveguide 802), so that the chromatic dispersion caused by each other can be compensated to achieve chromatic-dispersion-free pupil expansion. Similarly, the first part (or the first intermediate mirror 822) of the intermediate mirror 820 and the second part (or the second intermediate mirror 824) of the intermediate mirror 820 can have the same or similar orientations and can reflect light in opposite ways (e.g., from the -y direction to the x direction or from the x direction to the -y direction), so that the chromatic dispersion caused by each other can be compensated to achieve chromatic-dispersion-free pupil expansion.

[0099] Figure 8B shows an example of an input coupler 810 including a mirror 812 according to some embodiments. The mirror 812 can be oriented such that the display light reflected by the mirror 812 can propagate within the waveguide 802 by total internal reflection. The mirror 812 can have a very high reflectivity (e.g., close to 100%) and can have a sufficiently large input aperture to receive the display light and achieve a high resolution of the waveguide display.

[0100] Figure 8C shows another example of an input coupler 810 including one mirror 814 and a plurality of transmissive-reflective mirrors 816. The mirror 814 and the transmissive-reflective mirrors 816 can be oriented such that the display light reflected by each mirror can propagate within the waveguide 802 by total internal reflection. The mirror 814 can be similar to the mirror 812 and can have a very high reflectivity (e.g., close to 100%). The transmissive-reflective mirrors 816 can have a reflectivity less than 100% and can be at least partially transmissive. The input coupler 810 including the mirror 814 and the transmissive-reflective mirrors 816 can have a sufficiently large input aperture to receive the display light and achieve a high resolution of the waveguide display.

[0101] In some geometric waveguide (or hybrid waveguide) display systems, a user or a person in front of the display system may perceive multiple transmissive-reflective lenses as "stripes" on the eyepiece, which may affect the appearance of the display system (e.g., a near-eye display system). For example, in a geometric waveguide display system or a hybrid waveguide display system, when the transmissive-reflective lens is used as an intermediate grating for pupil expansion in a first dimension, the transmissive-reflective lens can typically be positioned at an angle close to 90° with respect to the broadside surface of the waveguide (e.g., approximately perpendicular to the broadside surface). This orientation of the transmissive-reflective lens can make the lens obvious to a person in front of the user because when the person views the near-eye display system at an oblique angle, there may be a large transmittance (or transparency) contrast between the partially reflective region (the transmissive-reflective lens) and the region between the partially reflective regions, which may cause the person's eyes to perceive an obvious structure (e.g., stripes).

[0102] Figure 9A and Figure 9B FIG. shows an example of a waveguide display 900 including an array of transmissive-reflective lenses 912 in a waveguide 910. The array of transmissive-reflective lenses 912 can form a grating structure (e.g., to replace the intermediate grating 630). Each transmissive-reflective lens 912 in the array of transmissive-reflective lenses can be planar and can be parallel to each other. As Figure 9A shown, when viewed from the broadside surface of the waveguide 910 (e.g., the x-y plane), the angle between the transmissive-reflective lens 912 and the vertical direction (e.g., the y direction) can be θ in the x-y plane. As Figure 9B shown, in a cross-sectional view (e.g., the x-z plane), the angle between the transmissive-reflective lens 912 and the broadside surface can be β (e.g., in the x-z plane). Thus, in the (x, y, z) space, the grating vector (or the surface normal direction of each planar transmissive-reflective lens) can be {cosθ·sinβ, sinθ·sinβ, cosβ}. In the example shown, β can be close to 90°, so the grating vector can be approximately {cosθ, sinθ, 0}.

[0103] Figure 9B It is also shown that when the eye 990 of a person in front of the waveguide display 900 views the waveguide display 900 at an oblique angle, the waveguide display 900 can have a minimum reflectivity or high transparency in the field of view represented by the angular range 920, but can have a high reflectivity (e.g., about 50% or higher) or low transparency in the field of view represented by the angular range 930. Thus, the person can see alternating brighter and darker regions instead of a uniform bright or dark region. In addition, this orientation of the transmissive-reflective lens may also reduce the optical resolution of the waveguide display system because the size of the light beam reflected by the transmissive-reflective lens (e.g., measured in the x direction) may be small, so the minimum spot size of the image on the image plane may be large.

[0104] Figure 9C An image of a near-eye display system 902 including a transmissive-reflective mirror 940 in a waveguide (e.g., a lens substrate). The near-eye display system 902 can be in the form of a pair of glasses. The transmissive-reflective mirror 940 can replace the middle grating 630. As Figure 9C shown, the transmissive-reflective mirror 940 can appear as alternating bright and dark regions (stripes) and can be rather prominent. For waveguide display systems, it is generally desirable that the optical gratings or other optical structures in or on the waveguide be as unobtrusive as possible.

[0105] According to some embodiments, the transmissive-reflective mirror used in the middle grating of a near-eye display system (e.g., a geometric waveguide display system or a hybrid waveguide display system) can be tilted at a specific angle (e.g., in the range of about 40° to 60°) with respect to the broadside surface of the waveguide. In this way, a person viewing the near-eye display system from different angles may mainly view the partially reflective regions (rather than the high transmittance gaps between the respective transmissive-reflective mirrors), and thus may perceive a low transmittance (or transparency) contrast. As such, the transmissive-reflective mirror may not be obvious to that person. Additionally, when the transmissive-reflective mirror of the middle grating is tilted from the surface normal direction of the broadside surface of the waveguide, the size of the light beam reflected by the transmissive-reflective mirror can be larger, so the effective optical aperture of the display system can be larger, and the optical resolution of the display system can be higher.

[0106] In one example, a waveguide display system can include an input coupler (e.g., a prism, a grating, or a tilted mirror), a middle light deflection structure (e.g., a middle grating or a first pupil expander including a plurality of VBGs or an array of transmissive-reflective mirrors), and an output light deflection structure (e.g., an output grating or a second pupil expander including a plurality of VBGs or an array of transmissive-reflective mirrors). The input coupler can couple display light from a projector into the waveguide. In some embodiments, the middle grating can include an array of transmissive-reflective mirrors arranged in a first direction and tilted at an angle less than about 60° (e.g., about 45° or 50°) with respect to the broadside surface of the waveguide. Each transmissive-reflective mirror in the array of transmissive-reflective mirrors can deflect a portion of the incident display light to a second direction toward the output grating. The output grating can include an array of transmissive-reflective mirrors or a plurality of VBGs and can direct a portion of the incident display light beam from the middle grating to the eye box of the waveguide display system at each of a plurality of positions along the second direction. In some embodiments, the transmissive-reflective mirror can be used in the middle grating and can be tilted at an angle between about 40° and about 60° (e.g., about 45° or 50°) with respect to the broadside surface of the waveguide. In some embodiments, the transmissive-reflective mirror can be used in the output grating and can be tilted at an angle between about 25° and about 35° with respect to the broadside surface of the waveguide.

[0107] Figure 10A andFigure 10B FIG. 1000 shows an example of a waveguide display including a geometric mirror for pupil expansion according to some embodiments. In the example shown, the waveguide display 1000 may include a waveguide 1002 (e.g., a substrate), and an input coupler 1010, a first pupil expander 1020, and a second pupil expander 1030 formed on or in the waveguide 1002. The waveguide display 1000 may be similar to the waveguide display system 600, but may include at least one pupil expander (e.g., the first pupil expander 1020 or the second pupil expander 1030) including a transmissive-reflective mirror. For example, the first pupil expander 1020 may include an array of transmissive-reflective mirrors 1022 forming a grating structure.

[0108] Display light from a projector may be collimated by projector optics and projected onto the input coupler 1010. The input coupler 1010 may include, for example, a transmissive grating or a reflective grating, a prism or a mirror or another reflective surface, and may couple the display light into the waveguide 1002 by diffraction, refraction, or reflection. The display light coupled into the waveguide 1002 may be reflected by the relatively wide side surfaces of the waveguide 1002 by total internal reflection, such that the display light may propagate within the waveguide 1002 towards the first pupil expander 1020. The display light from the input coupler 1010 may reach a first portion 1024 of the first pupil expander 1020, and may be reflected by the transmissive-reflective mirror 1022 in the first portion 1024 (which may have a very high reflectivity) to change the propagation direction to a first direction (e.g., an approximate x direction) towards a second portion 1026 of the first pupil expander 1020. In the case where the display light propagates within the waveguide 1002 in the first direction by total internal reflection, whenever the display light propagating within the waveguide 1002 reaches the transmissive-reflective mirror 1022, a portion of the display light may be reflected by the transmissive-reflective mirror 1022 of the first pupil expander 1020 towards the second pupil expander 1030, as Figure 10A shown. A portion of the display light may pass through the transmissive-reflective mirror and continue to propagate within the waveguide 1002 until it reaches another transmissive-reflective mirror 1022, which may reflect at least a portion of the incident display light towards the second pupil expander 1030. Thus, the first pupil expander 1020 may replicate the input pupil in the first direction (e.g., an approximate x direction). The second pupil expander 1030 may include a diffraction grating or a transmissive-reflective mirror, and may replicate the input pupil in a similar manner in a second direction (e.g., an approximate y direction) by partially reflecting or diffracting the incident display light towards the eye box multiple times. Thus, the first pupil expander 1020 and the second pupil expander 1030 may replicate the input pupil in two dimensions to fill the eye box, as described above with respect to Figure 6A 、 Figure 6B and Figure 8A described.

[0109] In the example shown, when viewed from the broadside surface of waveguide 1002, each transmissive-reflective lens 1022 in the first pupil expander 1020 can be at an angle θ (e.g., about 45°) with respect to the vertical direction (e.g., the y-direction) in the x-y plane as shown in Figure 10A shown. As shown in Figure 10B shown, in a cross-sectional view (e.g., the x-z plane), the angle between the transmissive-reflective lens 1022 and the broadside surface of waveguide 1002 can be β (e.g., in the x-z plane). Thus, the grating vector (or the surface normal direction of each planar transmissive-reflective lens 1022) can be {cosθ·sinβ, sinθ·sinβ, cosβ}. In the examples shown in Figure 10A and Figure 10B shown, β can be close to about 50°, and thus the grating vector can be {cosθ·sin50°, sinθ·sin50°, cos50°}.

[0110] As shown in Figure 10B shown, when the angle between the transmissive-reflective lens 1022 and the broadside surface of waveguide 1002 is less than about 60° (e.g., between about 40° and 60°), the first pupil expander 1020 can have the same or similar reflectivity (or transparency) in the field of view of the eye 1090 of a person located in front of the waveguide display 1000 and viewing the waveguide display 1000 at an oblique angle, because there may be no gaps between the transmissive-reflective lenses 1022 in the field of view of the eye 1090. Thus, the eye 1090 may not see alternating bright and dark regions, and thus the first pupil expander 1020 can have a more uniform transmittance (or transparency) and may not be noticeable to a person in front of the waveguide display 1000.

[0111] Figures 11A to 11C shows the relationship between the optical resolution of an imaging system and the size of the optical aperture (or the input beam width). Figure 11A shows a simplified imaging system 1100 (e.g., a lens or an eye) having an optical aperture 1110 and an imaging plane 1120, where an optical component (e.g., a lens) can be positioned at the optical aperture 1110. In the example shown, the optical aperture 1110 can be circular with a diameter D, and thus can allow a beam of diameter D (e.g., a collimated beam) to pass through. Figure 11B shows the best focused spot 1122 of the beam focused by the imaging system 1100 (e.g., the lens of the imaging system 1100). Due to the limited size of the optical aperture 1110, the minimum size of the central bright region of the spot 1122 may be limited by the diffraction limit. Figure 11CThe intensity of the light spot 1122 is shown as a function of the viewing angle from the optical aperture 1110. As shown in the figure, at the image plane 1120, the best focused light spot 1122 can have a first minimum at an angle θ (when viewed from the optical aperture 1110), which is approximately given by the following formula:

[0112]

[0113] where λ is the wavelength of the light beam. Therefore, a larger optical aperture or a larger input light beam can produce better resolution (smaller spots). Increasing the size of the optical aperture or the light beam can improve the modulation transfer function (MTF), and thus, in addition to improving the resolution of the image, it can also improve the contrast of the image.

[0114] As described above with respect to, for example Figure 9B When the angle between the transmissive reflector and the broadside surface of the waveguide is large (e.g., close to 90°), the size of the light beam reflected by the transmissive reflector may be small. Therefore, the minimum spot size of the image on the image plane may be large, and thus the optical resolution of the waveguide display system may be low.

[0115] Figure 12A An example of a pupil expander 1200 in the form of a geometric waveguide including a set of transmissive reflectors 1212 within the waveguide 1210 is shown. In the example shown, the angle between the transmissive reflectors 1212 and the broadside surface 1214 of the waveguide 1210 can be large (e.g., ≥60°, e.g., close to 90°), so the diameter D1 of the reflected light beam (measured in the x direction) can be very small. Thus, the MTF of the pupil expander 1200 may be low, and the resolution and / or contrast of the image displayed to the user's eye may not be good.

[0116] Figure 12B Another example of a pupil expander 1202 in the form of a geometric waveguide including a set of transmissive reflectors 1222 within the waveguide 1220 according to certain embodiments is shown. In the example shown, the angle between the transmissive reflectors 1222 and the broadside surface 1224 of the waveguide 1220 can be small (e.g., ≤60°, e.g., between about 40° and about 60°), so the diameter D2 of the reflected light beam (measured in the x direction) can be large, e.g., greater than half of the thickness of the waveguide 1220 or greater than the thickness of the waveguide 1220. Thus, the MTF of the pupil expander 1200 can be higher, and the resolution and / or contrast of the image displayed to the user's eye can be better.

[0117] When the angle between the transmissive-reflective lens 1222 and the wide-side surface 1224 of the waveguide 1220 used as an intermediate grating is too small (e.g., ≤ 40° or less), the transmissive-reflective lens 1222 may not split the incident light guided by the waveguide in a desired manner, thus failing to direct the incident light to the desired direction and failing to cover the desired field of view and the desired eyebox region with a given shape factor.

[0118] As described above, in various embodiments, the transmissive-reflective lens can be used as an intermediate grating (or a first output grating) or an output grating (or a second output grating). When used as an intermediate grating, the transmissive-reflective lens can be tilted at an angle between about 40° and about 60° (e.g., about 45° or 50°) with respect to the wide-side surface of the waveguide. When used as an output grating, the transmissive-reflective lens can be tilted at an angle between about 25° and about 35° with respect to the wide-side surface of the waveguide. In some waveguide display systems, the pupil expander including the transmissive-reflective lens can be arranged differently from the Figure 6A and Figure 9A arrangement shown in

[0119] Figure 13 FIG. 11 shows an example of a waveguide display system 1300 according to certain embodiments, which can be a geometric waveguide display system or a hybrid waveguide display system. The waveguide display system 1300 can include a substrate 1310, which can be similar to the above-described substrate 610 or waveguide 802 or 1002. The substrate 1310 can be transmissive to visible light and can include, for example, a glass substrate, a quartz substrate, a plastic substrate, a polymer substrate, a PMMA substrate, a ceramic substrate, or a crystal substrate. The substrate 1310 can be a flat substrate or a curved substrate. The substrate 1310 can include a first surface 1312 and a second surface 1314. Display light can be coupled into the substrate 1310 by an input coupler 1320 and can be reflected by the first surface 1312 and the second surface 1314 by total internal reflection, such that the display light can propagate within the substrate 1310.

[0120] As described above, the input coupler 1320 can include a diffractive coupler (e.g., a volume holographic grating or a surface relief grating), a refractive coupler (e.g., an optical wedge or a prism), or a reflective coupler (e.g., a reflective surface having an inclined angle with respect to the substrate 1310). For example, in one embodiment, the input coupler 1320 can include a prism that can couple display light of different colors into the substrate 1310 at the same refractive angle. The prism can have a refractive index that matches the refractive index of the substrate 1310 and can include an optical wedge having a specific angle such that the light coupled into the substrate 1310 can be incident on the surface 1312 or 1314 of the substrate 1310 at an incident angle greater than the critical angle of the substrate 1310. Thus, the display light coupled into the substrate 1310 can be guided by the substrate 1310 through total internal reflection. In another example, the input coupler can include a grating coupler that can diffract light of different colors into the substrate 1310 in different directions.

[0121] The waveguide display system 1300 can also include a first grating 1330 and a second grating 1340 within the substrate 1310 and / or on one or both wide side surfaces of the substrate 1310 (e.g., the first surface 1312 and the second surface 1314) for expanding the incident display beam in two dimensions to fill the eyebox with display light. In one example, the first grating 1330 can include one or more transmissive-reflective mirrors arranged substantially along the x direction. Each transmissive-reflective mirror can be configured to partially reflect and partially transmit the display light when the display light propagates in the substrate 1310 (e.g., substantially along the x direction). Thus, the first grating 1330 can split the display beam and replicate the input pupil in the approximately x direction. In another example, the first grating 1330 can include a multiplexed VBG as described above.

[0122] The second grating 1340 can include a plurality of multiplexed VBGs or a set of transmissive-reflective mirrors and can be configured to expand the display light from the first grating 1330 in different directions (e.g., approximately the y direction) by diffracting or reflecting a portion of the display light into the eyebox whenever the display light propagating within the substrate 1310 reaches the transmissive-reflective mirror or the second grating 1340 from a specific direction. Thus, the second grating 1340 can replicate the input pupil in the approximately y direction.

[0123] Figure 14Another example of a waveguide display system 1400 in accordance with certain embodiments is shown. The waveguide display system 1400 may include a waveguide 1405 and an input grating 1410, a first intermediate grating 1420, a second intermediate grating 1430, and an output grating 1440 formed on or in the waveguide 1405. Each of the input grating 1410, the first intermediate grating 1420, the second intermediate grating 1430, and the output grating 1440 may be a transmissive diffraction grating, a reflective diffraction grating, or a set of one or more transmissive-reflective mirrors. Display light from a light source (e.g., one or more micro-LED arrays) may be coupled into the waveguide 1405 by the input grating 1410. The coupled-in display light may be reflected by the surface of the waveguide 1405 by total internal reflection such that the display light may propagate within the waveguide 1405. In some embodiments, the input grating 1410 may include a multiplexed VBG and may couple display light of different colors and from different fields of view into the waveguide 1405 at corresponding diffraction angles. In some embodiments, the input grating 1410 may include one or more mirrors having a high reflectivity and may couple display light of different colors and from different fields of view into the waveguide 1405.

[0124] The first intermediate grating 1420 and the second intermediate grating 1430 may be located in different regions of the same material layer or may be located on different layers. In some embodiments, the first intermediate grating 1420 may be spatially separated from the second intermediate grating 1430. The first intermediate grating 1420 and the second intermediate grating 1430 may each include a plurality of multiplexed VBGs or one or more transmissive-reflective mirrors. The display light coupled into the waveguide 1405 by the input grating 1410 may be directed to the first intermediate grating 1420, which may redirect the display light to the second intermediate grating 1430. The second intermediate grating 1430 may diffract or reflect the display light at multiple locations to direct the display light to the output grating 1440.

[0125] The output grating 1440 may be in the viewing area of the waveguide display system 1400 and may include an exit region 1450 that overlaps the eyebox of the waveguide display system 1400 when viewed in the z-direction (e.g., at a distance of about 15 mm to 20 mm from the output grating 1440 in the +z or -z direction). The output grating 1440 may include a multiplexed VBG or a transmissive-reflective mirror and may diffract or reflect the display light at multiple locations to direct the display light to the eyebox of the waveguide display system 1400. Thus, the output grating 1440 in combination with the first intermediate grating 1420 and the second intermediate grating 1430 may perform biaxial pupil expansion to expand the incident display beam in two dimensions, thereby filling the eyebox with display light.

[0126] In some embodiments, the first intermediate grating 1420 and the second intermediate grating 1430 may include a plurality of VBGs, and each VBG in the first intermediate grating 1420 may match a corresponding VBG in the second intermediate grating 1430 (e.g., having the same grating vector in the x-y plane and having the same and / or opposite grating vectors in the z direction). Since the propagation directions of the display light at the two matching VBGs are opposite, the two matching VBGs may operate under opposite Bragg conditions (e.g., +1st order diffraction vs. -1st order diffraction). For example, as Figure 14 shown, the VBG in the first intermediate grating 1420 may change the propagation direction of the display light from the downward direction to the right direction, while the matching VBG in the second intermediate grating 1430 may change the propagation direction of the display light from the right direction to the downward direction. Thus, the dispersion caused by the second intermediate grating 1430 may be opposite to the dispersion caused by the first intermediate grating 1420, thereby reducing or minimizing the overall dispersion.

[0127] In some embodiments, the input grating 1410 and the output grating may include a plurality of VBGs, and each VBG in the input grating 1410 may match a corresponding VBG in the output grating 1440 (e.g., having the same grating vector in the x-y plane and having the same and / or opposite grating vectors in the z direction). Since the propagation directions of the display light at the two matching VBGs are opposite (e.g., entering and leaving the waveguide 1405), the two matching VBGs may also operate under opposite Bragg conditions (e.g., +1st order diffraction vs. -1st order diffraction). Therefore, the dispersion caused by the input grating 1410 may be opposite to the dispersion caused by the output grating 1440, thereby reducing or minimizing the overall dispersion.

[0128] Figure 15 Another example of a waveguide display system 1500 according to certain embodiments is shown. The waveguide display system 1500 may include a substrate 1510, which may be similar to the substrate 610. The substrate 1510 may include a first surface 1512 and a second surface 1514. Display light from a light source (e.g., an LED) may be coupled into the substrate 1510 by an input coupler 1520 and may be reflected by the first surface 1512 and the second surface 1514 by total internal reflection such that the display light may propagate within the substrate 1510. As described above, the input coupler 1520 may include a diffractive coupler (e.g., a volume holographic grating or a surface relief grating), a refractive coupler (e.g., an optical wedge or a prism), or a reflective coupler (e.g., a reflective surface having an inclined angle with respect to the substrate 1510).

[0129] The waveguide display system 1500 may also include a first grating 1530 and a second grating 1540 formed in the substrate 1510 or on the first surface 1512 and / or the second surface 1514 of the substrate 1510. Each of the first grating 1530 and the second grating 1540 may include a multiplexed VBG or a transmissive-reflective mirror. In Figure 15 the example shown, the first grating 1530 and the second grating 1540 may be located in different regions in the x direction and may overlap in at least a portion of the see-through region of the waveguide display system 1500. The first grating 1530 and the second grating 1540 may be used for biaxial pupil expansion to expand the incident display beam in two dimensions so as to fill the eyebox 1550 with display light (e.g., at a distance of about 15 mm to 20 mm from the second grating 1540 in the +z or -z direction). For example, the first grating 1530 may expand the display beam in the approximate y direction, while the second grating 1540 may expand the display beam in the approximate x direction.

[0130] In addition, the waveguide display system 1500 may include a third grating 1560. The third grating 1560 may include a plurality of VBGs or one or more mirrors. In some embodiments, the third grating 1560 and the first grating 1530 may be arranged at different positions in the y direction. In some embodiments, the third grating 1560 and the first grating 1530 may be in different regions of the same layer. In some embodiments, the third grating 1560 may be spatially separated from the first grating 1530. The third grating 1560 may direct the display light from the input coupler 1520 to the first grating 1530.

[0131] The input coupler 1520 may couple the display light from a light source into the substrate 1510. The display light may propagate approximately in the x direction within the substrate 1510 and may reach the third grating 1560 directly, or may be reflected by the first surface 1512 and / or the second surface 1514 to the third grating 1560. The third grating 1560 may diffract or reflect the display light downward to the first grating 1530. Although the display light diffracted or reflected by the third grating 1560 propagates in one direction (e.g., approximately in the y direction) within the substrate 1510 by total internal reflection, whenever the display light propagating within the substrate 1510 reaches, for example, a transmissive-reflective mirror in the first grating 1530, a portion of the display light may be diffracted or reflected by the first grating 1530 to the second grating 1540. Then, whenever the display light propagating within the substrate 1510 reaches the second grating 1540 (e.g., a transmissive-reflective mirror), the second grating 1540 may expand the display light from the first grating 1530 in a different direction (e.g., approximately in the x direction) by diffracting or reflecting a portion of the display light to the eyebox 1550.

[0132] In some embodiments, the input coupler 1520 and the second grating 1540 may include matched VBGs (e.g., VBGs having the same grating vector in the x-y plane and the same or opposite grating vectors in the z direction) to reduce the overall dispersion caused by the input coupler 1520 and the second grating 1540. In some embodiments, the first grating 1530 and the third grating 1560 may include matched VBGs (e.g., VBGs having the same grating vector in the x-y plane and the same and / or opposite grating vectors in the z direction) to reduce the overall dispersion caused by the gratings 1530 and 1560.

[0133] Although only one input coupler is shown in each of the figures in Figure 6A , Figure 8A , Figure 10A and Figures 13 to 15 , in some embodiments, the geometric waveguide display system or the hybrid waveguide display system disclosed herein may include two or more input couplers, where each input coupler may be configured to couple display light from respective fields of view and / or respective spectral ranges into the waveguide. The waveguide display system may also include corresponding gratings and / or transmissive-reflective mirrors for biaxially expanding the display light coupled into the waveguide through each input coupler.

[0134] Embodiments of the present invention may include an artificial reality system or may be implemented in combination with an artificial reality system. Artificial reality is a form of reality that has been adjusted in some way before being presented to a user, and artificial reality may include, for example, virtual reality (VR), augmented reality (AR), mixed reality (MR), hybrid reality, or some combination and / or derivative thereof. Artificial reality content may include fully generated content or content generated in combination with captured (e.g., real-world) content. Artificial reality content may include video, audio, tactile feedback, or some combination thereof, and any of them may be presented in a single channel or multiple channels (e.g., stereoscopic video that produces a three-dimensional effect for a viewer). Additionally, in some embodiments, artificial reality may also be associated with applications, products, accessories, services, or some combination thereof that are used, for example, to create content in artificial reality and / or otherwise for use in artificial reality (e.g., to perform activities in artificial reality). An artificial reality system that provides artificial reality content may be implemented on various platforms, including a head-mounted display (HMD) connected to a host computer system, a standalone HMD, a mobile device or computing system, or any other hardware platform capable of providing artificial reality content to one or more viewers.

[0135] Figure 16 is a simplified block diagram of an electronic system 1600 of an example near-eye display (e.g., an HMD device) for implementing some of the examples disclosed herein. The electronic system 1600 can be used as the electronic system in an HMD device or other near-eye display as described above. In this example, the electronic system 1600 can include one or more processors 1610 and a memory 1620. The one or more processors 1610 can be configured to execute instructions for performing operations at multiple components, and can be, for example, a general-purpose processor or a microprocessor suitable for implementation within a portable electronic device. The one or more processors 1610 can be communicatively coupled to multiple components within the electronic system 1600. To achieve such communicative coupling, the one or more processors 1610 can communicate with the other illustrated components via a bus 1640. The bus 1640 can be any subsystem suitable for transmitting data within the electronic system 1600. The bus 1640 can include multiple computer buses and additional circuitry for transmitting data.

[0136] The memory 1620 can be coupled to the one or more processors 1610. In some embodiments, the memory 1620 can provide both short-term storage and long-term storage, and can be divided into several units. The memory 1620 can be volatile, such as static random access memory (SRAM) and / or dynamic random access memory (DRAM), and / or the memory can be non-volatile, such as read-only memory (ROM) and flash memory, etc. Additionally, the memory 1620 can include removable storage devices, such as secure digital (SD) cards. The memory 1620 can provide storage for the electronic system 1600 for multiple computer-readable instructions, multiple data structures, multiple program codes, and other data. In some embodiments, the memory 1620 can be distributed across different hardware subsystems. Instruction sets and / or codes can be stored on the memory 1620. These instructions can be in the form of executable code executable by the electronic system 1600, and / or can be in the form of source code and / or installable code, and when these instructions are compiled and / or installed on the electronic system 1600 (e.g., using any one of various commonly available compilers, installers, compression / decompression utilities, etc.), they can be in the form of executable code.

[0137] In some embodiments, the memory 1620 may store multiple applications 1622 to 1624, and the multiple applications may include any number of applications. Examples of applications may include game applications, conferencing applications, video playback applications, or other suitable applications. These application programs may include depth sensing functions or eye tracking functions. The applications 1622 to 1624 may include multiple specific instructions to be executed by one or more processors 1610. In some embodiments, certain applications or certain portions of the applications 1622 to 1624 may be capable of being executed by multiple other hardware subsystems 1680. In certain embodiments, the memory 1620 may additionally include a secure memory, and the secure memory may include multiple additional security controls to prevent copying of secure information or other unauthorized access to the secure information.

[0138] In some embodiments, the memory 1620 may include an operating system 1625 loaded in the memory. The operating system 1625 may be operable to initiate execution of the multiple instructions provided by the applications 1622 to 1624 and / or manage the other hardware subsystems 1680 and interact with the wireless communication subsystem 1630, which may include one or more wireless transceivers. The operating system 1625 may be adapted to perform other operations across multiple components in the electronic system 1600, and these other operations include threading, resource management, data storage control, and other similar functions.

[0139] The wireless communication subsystem 1630 may include, for example, an infrared communication device, a wireless communication device, and / or a chipset (e.g., Devices, IEEE 802.11 devices, Wi-Fi devices, WiMax devices, cellular communication facilities, etc.), and / or similar communication interfaces. The electronic system 1600 may include one or more antennas 1634 for wireless communication, which are part of a wireless communication subsystem 1630 or separate components coupled to any part of the system. Depending on the desired functionality, the wireless communication subsystem 1630 may include multiple individual transceivers for communicating with multiple base transceiver stations and other wireless devices and access points, which may include communication with different data networks and / or network types, such as wireless wide-area network (WWAN), wireless local area network (WLAN), or wireless personal area network (WPAN). The WWAN may be, for example, a WiMax (IEEE 802.16) network. The WLAN may be, for example, an IEEE 802.11x network. The WPAN may be, for example, a Bluetooth network, IEEE 802.15x, or some other type of network. The techniques described herein may also be used for any combination of WWAN, WLAN, and / or WPAN. The wireless communication subsystem 1630 may allow for the exchange of data with networks, other computer systems, and / or any other devices described herein. The wireless communication subsystem 1630 may include means for transmitting or receiving data (e.g., an identifier of an HMD device, location data, a geographical map, a heat map, a photo, or a video) using one or more antennas 1634 and one or more wireless links 1632.

[0140] Multiple embodiments of the electronic system 1600 may also include one or more sensors 1690. The one or more sensors 1690 may include, for example, an image sensor, an accelerometer, a pressure sensor, a temperature sensor, a proximity sensor, a magnetometer, a gyroscope, an inertial sensor (e.g., a subsystem combining an accelerometer and a gyroscope), an ambient light sensor, or any other similar device or subsystem that can be operated to provide sensory output and / or receive sensory input, such as a depth sensor or a position sensor. For example, in some embodiments, the one or more sensors 1690 may include one or more inertial measurement units (IMUs) and / or one or more position sensors. The IMU may generate calibration data indicating an estimated position of the HMD device relative to an initial position of the HMD device based on a plurality of measurement signals received from one or more of the position sensors. The position sensor may generate one or more measurement signals in response to the movement of the HMD device. Examples of the position sensor may include, but are not limited to, one or more accelerometers, one or more gyroscopes, one or more magnetometers, another suitable type of sensor for detecting movement, a type of sensor for error correction of the IMU, or some combination thereof. The position sensor may be located outside the IMU, inside the IMU, or some combination thereof. At least some sensors may use a structured light pattern for sensing.

[0141] The electronic system 1600 may include a display 1660. The display 1660 may be a near-eye display and may graphically present information from the electronic system 1600 to the user, such as images, videos, and various instructions. Such information may be obtained from one or more of the applications 1622 to 1624, the virtual reality engine 1626, one or more other hardware subsystems 1680, combinations thereof, or any other suitable means for parsing graphical content for the user (e.g., via the operating system 1625). The display 1660 may use liquid crystal display (LCD) technology, light emitting diode display (LED) technology (e.g., including OLED, ILED, μLED, AMOLED, TOLED, etc.), light emitting polymer display (LPD) technology, or some other display technology.

[0142] The electronic system 1600 may include a user input / output interface 1670. The user input / output interface 1670 may allow a user to send multiple action requests to the electronic system 1600. The action requests may be requests to perform specific actions. For example, the action requests may be requests to start or end an application or to perform a specific action within an application. The user input / output interface 1670 may include one or more input devices. Multiple example input devices may include a touch screen, a touchpad, one or more microphones, one or more buttons, one or more knobs, one or more switches, a keyboard, a mouse, a game controller, or any other suitable device for receiving action requests and transmitting the received action requests to the electronic system 1600. In some embodiments, the user input / output interface 1670 may provide haptic feedback to the user according to multiple instructions received from the electronic system 1600. For example, haptic feedback may be provided when the action request is received or when the action request has been executed.

[0143] The electronic system 1600 may include a camera 1650, which may be used to take a photo or video of the user, for example, for tracking the position of the user's eyes. The camera 1650 may also be used to take a photo or video of the environment, for example, for VR applications, AR applications, or MR applications. The camera 1650 may include, for example, a complementary metal–oxide–semiconductor (CMOS) image sensor having millions or tens of millions of pixels. In some embodiments, the camera 1650 may include two or more cameras that can be used to acquire 3D images.

[0144] In some embodiments, the electronic system 1600 may include multiple other hardware subsystems 1680. Each of the multiple other hardware subsystems 1680 may be a physical subsystem within the electronic system 1600. Although each of the multiple other hardware subsystems 1680 may be permanently configured as a structure, some of the multiple other hardware subsystems 1680 may be temporarily configured to perform multiple specific functions or be temporarily activated. Examples of the multiple other hardware subsystems 1680 may include, for example, an audio output and / or input interface (e.g., a microphone or a speaker), a near field communication (NFC) device, a rechargeable battery, a battery management system, a wired / wireless battery charging system, etc. In some embodiments, one or more functions of the multiple other hardware subsystems 1680 may be implemented in software.

[0145] In some embodiments, the memory 1620 of the electronic system 1600 may also store a virtual reality engine 1626. The virtual reality engine 1626 may execute applications within the electronic system 1600 and receive position information, acceleration information, velocity information, predicted future positions, or some combination thereof of the HMD device from various sensors. In some embodiments, the information received by the virtual reality engine 1626 may be used to generate signals (e.g., a plurality of display instructions) to the display 1660. For example, if the received information indicates that the user has looked left, the virtual reality engine 1626 may generate content for the HMD device that reflects the user's movement in the virtual environment. Additionally, the virtual reality engine 1626 may execute actions within the application and provide feedback to the user in response to an action request received from the user input / output interface 1670. The feedback provided may be visual feedback, auditory feedback, or haptic feedback. In some implementations, one or more processors 1610 may include one or more GPUs that can execute the virtual reality engine 1626.

[0146] In various implementations, the hardware and subsystems described above may be implemented on a single device or on multiple devices that can communicate with each other using a wired connection or a wireless connection. For example, in some implementations, some components or subsystems, such as a GPU, the virtual reality engine 1626, and applications (e.g., a tracking application), may be implemented on a console separate from the head-mounted display device. In some implementations, a console may be connected to more than one HMD or support more than one HMD.

[0147] In an alternative configuration, different components and / or additional components may be included in the electronic system 1600. Similarly, the functions of one or more of these components may be distributed among these components in a manner different from the above-described manner. For example, in some embodiments, the electronic system 1600 may be modified to include other system environments, such as an AR system environment and / or an MR system environment.

[0148] The methods, systems, and devices discussed above are all examples. Various embodiments may appropriately omit, replace, or add various procedures or components. For example, in an alternative configuration, the described methods may be executed in a different order than described, and / or various stages may be added, omitted, and / or combined. Additionally, the features described with respect to certain embodiments may be combined in various other embodiments. The different aspects and elements of the embodiments may be combined in a similar manner. Furthermore, technology is evolving, so many of the elements are examples that do not limit the scope of the present disclosure to these specific examples.

[0149] Specific details are given in the description to provide a thorough understanding of the embodiments. However, the embodiments may be practiced without these specific details. For example, well-known circuits, processes, systems, structures, and techniques have been shown without unnecessary details in order to avoid obscuring the embodiments. This description merely provides example embodiments and is not intended to limit the scope, applicability, or configuration of the present invention. Rather, the foregoing description of the embodiments will provide those skilled in the art with an enabling description for implementing the various embodiments. Various changes may be made to the functions and arrangements of the elements without departing from the scope of the disclosure.

[0150] In addition, some embodiments have been described as processes depicted as flowcharts or block diagrams. Although each process may describe the plurality of operations as a sequential process, many of the operations in the plurality of operations may be performed in parallel or simultaneously. In addition, the order of these operations may be rearranged. A process may have additional steps not included in the figures. Moreover, the embodiments of the method may be implemented by hardware, software, firmware, middleware, microcode, a hardware description language, or any combination thereof. When implemented in software, firmware, middleware, or microcode, the program code or code segments for performing the associated tasks may be stored in a computer-readable medium such as a storage medium. The processors may execute the associated tasks.

[0151] It will be apparent to those skilled in the art that substantial variations may be made in accordance with various specific requirements. For example, custom or dedicated hardware may also be used, and / or specific elements may be implemented in hardware, software (including portable software, such as applets, etc.), or both. In addition, connections to other computing devices, such as network input / output devices, may be employed.

[0152] Referring to the accompanying drawings, a component that may include a memory may include a non-transitory machine-readable medium. As used herein, the terms "machine-readable medium" and "computer-readable medium" refer to any storage medium that participates in providing data that causes a machine to operate in a particular manner. In the embodiments provided above, various machine-readable media may be involved in providing instructions / code to a processing unit and / or one or more other devices for execution. Additionally or alternatively, the machine-readable medium may be used to store and / or carry such instructions / code. In many implementations, the computer-readable medium is a physical and / or tangible storage medium. Such media may take many forms, including but not limited to non-volatile media, volatile media, and transmission media. Common forms of computer-readable media include, for example, magnetic and / or optical media such as compact disks (CDs) or digital versatile disks (DVDs), punched cards, paper tapes, any other physical medium with hole patterns, random access memory (RAM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), flash erasable programmable read-only memory (FLASH-EPROM), any other memory chip or cartridge, carrier waves as described below, or any other medium from which a computer can read instructions and / or code. A computer program product may include code and / or machine-executable instructions that may represent a process, function, subroutine, program, routine, application, subroutine, module, software package, class, or any combination of instructions, data structures, or program statements.

[0153] Those skilled in the art will recognize that the information and signals used to convey the messages described herein may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referred to throughout the above description may be represented using voltages, currents, electromagnetic waves, magnetic fields or magnetic particles, optical fields or optical particles, or any combination thereof.

[0154] As used herein, the terms "and" and "or" can include a variety of meanings, which are also at least partially anticipated based on the context in which these terms are used. Typically, "or" if used to relate a list, such as A, B, or C, is intended to mean A, B, and C (used in an inclusive sense here), as well as A, B, or C (used in an exclusive sense here). In addition, as used herein, the term "one or more" can be used to describe any feature, structure, or property in the singular, or it can be used to describe some combination of features, structures, or properties. However, it should be noted that this is merely an illustrative example, and the claimed subject matter is not limited to this example. In addition, the term "at least one of" if used to relate a list, such as A, B, or C, can be interpreted to mean: A; B; C; or any combination of A, B, and / or C, such as AB, AC, BC, AA, ABC, AAB, or AABBCCC, etc.

[0155] In addition, although certain embodiments have been described using a specific combination of hardware and software, it should be recognized that other combinations of hardware and software are also possible. Certain embodiments can be implemented using only hardware, or only software, or using a combination thereof. In one example, the software can be implemented using a computer program product that includes computer program code or instructions that can be executed by one or more processors to perform any or all of the steps, operations, or processes described in this disclosure, where the computer program can be stored on a non-transitory computer-readable medium. The various processes described herein can be implemented on the same processor or on any combination of different processors.

[0156] In cases where a device, system, component, or module is described as being configured to perform certain operations or functions, such configuration can be accomplished, for example, by designing an electronic circuit that performs the operation, by programming a programmable electronic circuit (such as a microprocessor) that performs the operation (e.g., by executing computer instructions or code), or by programming a processor or core that is programmed to execute code or instructions stored on a non-transitory storage medium, or any combination thereof. The various processes can communicate using a variety of techniques, including but not limited to traditional techniques for inter-process communication, and different pairs of processes can use different techniques, or the same pair of processes can use different techniques at different times.

[0157] Accordingly, the specification and drawings are to be regarded as illustrative rather than restrictive. However, it will be apparent that various additions, deletions, omissions, and other modifications and alterations can be made without departing from the broader spirit and scope as set forth in the claims. Thus, although numerous specific embodiments have been described, these specific embodiments are not intended to be limiting. Various modifications and equivalents fall within the scope of the appended claims.

Claims

1. A waveguide display system, comprising: A waveguide; An input coupler configured to couple display light into the waveguide; A first pupil expander; And A second pupil expander, Wherein the first pupil expander is configured to deflect the display light towards the second pupil expander at a first plurality of positions along a first direction, Wherein the second pupil expander is configured to deflect the display light from the first pupil expander towards the eye box of the waveguide display system at a second plurality of positions along a second direction different from the first direction, and Wherein at least one of the first pupil expander or the second pupil expander includes a plurality of transmissive - reflective mirrors that are tilted within the waveguide such that the plurality of transmissive - reflective mirrors are not apparent when viewed at an oblique angle.

2. The waveguide display system according to claim 1, wherein, The first pupil expander includes a transmissive - reflective mirror tilted within the waveguide at an angle between 40° and 60° relative to the wide - side surface of the waveguide.

3. The waveguide display system according to any one of the preceding claims, wherein, The second pupil expander includes a transmissive - reflective mirror tilted within the waveguide at an angle between 25° and 35° relative to the wide - side surface of the waveguide.

4. The waveguide display system according to any one of the preceding claims, wherein, The plurality of transmissive - reflective mirrors are characterized by different respective reflection efficiencies.

5. The waveguide display system according to any one of the preceding claims, wherein, At least one of the input coupler, the first pupil expander, or the second pupil expander includes a multiplexed volume Bragg grating, in which case, optionally, the multiplexed volume Bragg grating includes a reflective diffraction grating or a transmissive diffraction grating.

6. The waveguide display system according to any one of the preceding claims, wherein, The input coupler includes a volume Bragg grating, a surface relief grating, a prism, or a reflective surface.

7. The waveguide display system according to any one of the preceding claims, wherein, Each of the plurality of transmissive - reflective mirrors includes a plurality of dielectric coatings.

8. The waveguide display system according to any one of the preceding claims, wherein, The width of the light beam reflected by each of the plurality of transmissive - reflective mirrors is greater than half of the thickness of the waveguide.

9. The waveguide display system according to any one of the preceding claims, wherein, Each of the plurality of transmissive - reflective mirrors is characterized by a full - width at half - maximum (FWHM) reflection angle range greater than 40°.

10. The waveguide display system according to any one of the preceding claims, and any one or more of the following: a) Among them, At least one of the plurality of transmissive - reflective mirrors is characterized by a reflectivity greater than 50%; or b) wherein: The input coupler includes a first volume Bragg grating characterized by a first grating vector; The second pupil expander includes a second volume Bragg grating characterized by a second grating vector; and The first grating vector and the second grating vector have the same component in a plane parallel to the wide - side surface of the waveguide; or c) wherein, when viewed in the direction of the surface normal of the waveguide, the first pupil expander and the second pupil expander at least partially overlap.

11. The waveguide display system according to any one of the preceding claims, further comprising a deflector configured to deflect the display light from the input coupler towards the first pupil expander, in which case, optionally, wherein: The deflector includes a first set of one or more mirrors and / or transmissive - reflective mirrors having a first orientation; and The first pupil expander includes a second set of one or more mirrors and / or beam splitters having the first orientation.

12. The waveguide display system according to any one of the preceding claims, wherein: The input coupler includes a first set of one or more mirrors and / or beam splitters having a first orientation; and The second pupil expander includes a second set of one or more mirrors and / or beam splitters having the first orientation.

13. A near-eye display system, comprising: An image source configured to emit display light of an image; A waveguide that is transmissive to visible light; Display optics configured to project the display light onto the waveguide; An input coupler configured to couple the display light into the waveguide; A first pupil expander configured to split the display light at a first plurality of positions along a first direction; And A second pupil expander configured to split the display light at each of the first plurality of positions from the first pupil expander at a second plurality of positions along a second direction different from the first direction, wherein at least one of the first pupil expander or the second pupil expander includes a plurality of beam splitters that are tilted within the waveguide such that the plurality of beam splitters are not visible when viewed at an oblique angle.

14. The near-eye display system according to claim 13, and any one or more of the following: a) wherein: The first pupil expander includes a beam splitter tilted within the waveguide at an angle between 40° and 60° with respect to the wide-side surface of the waveguide; and The second pupil expander includes a beam splitter tilted within the waveguide at an angle between 25° and 35° with respect to the wide-side surface of the waveguide; or b) wherein, The plurality of beam splitters are characterized by different respective reflection efficiencies; and The width of the light beam reflected by each of the plurality of beam splitters is greater than half of the thickness of the waveguide.

15. A near-eye display system, comprising: A waveguide that is transmissive to display light; An input coupler configured to couple the display light into the waveguide, the input coupler including a first set of one or more mirrors and / or beam splitters having a first orientation; A first pupil expander; And A second pupil expander, wherein the first pupil expander is configured to deflect the display light from the input coupler towards the second pupil expander at a first plurality of positions along a first direction, the first pupil expander including a second set of one or more mirrors and / or beam splitters having a second orientation; and Wherein, the second pupil expander is configured to deflect display light from the first pupil expander towards an eyebox of the near-eye display system at a second plurality of positions along a second direction different from the first direction, and the second pupil expander includes a third set of one or more mirrors and / or transmissive mirrors having the first orientation.

Images