Patent Description:
Diffractive optical elements (DOEs) are optical elements with a periodic structure that are commonly utilized in applications ranging from bio-technology, material processing, sensing, and testing to technical optics and optical metrology. By incorporating DOEs in an optical field of a laser or emissive display, for example, the light's "shape" can be controlled and changed flexibly according to application needs. <CIT> discloses an exit pupil extender which comprises two intermediate optical couplers which serve as exit pupil extending components, each disposed between an input optical element and one of two exit optical elements. All optical elements and couplers are diffractive optical elements having grating lines.

The invention provides an optical display as defined by the appended claims. A waveguide display includes multiple diffractive optical elements (DOEs) that are configured to in-couple incident image light from an imager, provide expanded exit pupil in two directions, and out-couple the image light to a user in a near-eye optical display system. An in-coupling DOE is configured to split the full field of view (FOV) of the image light into left and right portions. The left and right FOV portions are respectively propagated laterally in left and right directions in intermediate DOEs which comprise upper and lower portions. The intermediate DOEs provide for exit pupil expansion in a first (e.g., horizontal) direction while coupling light to an out-coupling DOE. The out-coupling DOE provides for exit pupil expansion in a second (e.g., vertical) direction and out-couples image light out of the waveguide with expanded exit pupil for the full FOV. The intermediate DOE portions are configured to steer image light back towards the center of the waveguide to avoid dark areas or stripes in the part of the out-coupling DOE that is located below the in-coupling DOE.

The waveguide display may further be configured to selectively couple image light downwards in the waveguide without cross-coupling between light components in the waveguide which comprises multiple waveguide plates to support an RGB (red, green, blue) color model. For example, the in-coupling DOE is configured as a two-sided grating having different grating vectors on each surface to in-couple incident image light and steer the in-coupled image light for the first diffraction order downward in the waveguide without downward coupling of zeroth diffraction order light which is evanescent in the waveguide. Since light must go through the first diffractive order, which is evanescent for red light in the green waveguide plate, the red light is not coupled downward. This selective coupling reduces the cross-coupling of red image light into the green waveguide plate within a central portion of the FOV.

In one illustrative embodiment, the grating vectors in the upper right and lower left intermediate DOEs have the same or similar directions to enable image light to be spread towards the center of the waveguide to reduce dark areas or stripes. In another illustrative embodiment, lower portions of the left and right intermediate DOEs may be combined into a single or two-sided grating. The first surface has a grating vector with the same or similar direction as that of the top right intermediate DOE while the second, opposite surface has a grating vector with the same or similar direction as that of the top intermediate DOE. Alternatively, the combined grating may be configured as a single-sided or two-sided crossed (i.e., two-dimensional) grating.

Like reference numerals indicate like elements in the drawings. Elements are not drawn to scale unless otherwise indicated.

<FIG> shows a block diagram of an illustrative near-eye display system <NUM> which incorporates a combination of diffractive optical elements (DOEs) that provide in-coupling of incident light into a waveguide, exit pupil expansion in two directions, and out-coupling of light out of the waveguide. Near-eye display systems are often used, in head mounted display (HMD) devices in industrial, commercial, and consumer applications. Other devices and systems also use near-eye systems, as described below. The near-eye display system <NUM> is an example that is used to provide context and illustrate various features and aspects of the present waveguide display with increased uniformity and reduced cross-coupling between colors.

System <NUM> may include one or more imagers (representatively indicated by reference numeral <NUM>) that work with an optical system <NUM> to deliver images as a virtual display to a user's eye <NUM>. The imager <NUM> includes, RGB (red, green, blue) light emitting diodes (LEDs), LCOS (liquid crystal on silicon) devices, OLED (organic light emitting diode) arrays, MEMS (micro-electro mechanical system) devices, or any other suitable displays or micro-displays operating in transmission, reflection, or emission. The imager <NUM> may also include mirrors and other components that enable a virtual display to be composed and provide one or more input optical beams to the optical system. The optical system <NUM> can typically include magnifying optics <NUM>, pupil forming optics <NUM>, and one or more waveguides <NUM>. The imager <NUM> may include or incorporate an illumination unit and/or light engine (not shown) that may be configured to provide illumination in a range of wavelengths and intensities in some implementations.

In a near-eye display system the imager does not actually shine the images on a surface such as a glass lens to create the visual display for the user. This is not feasible because the human eye cannot focus on something that is that close. Rather than create a visible image on a surface, the near-eye display system <NUM> uses the pupil forming optics <NUM> to form a pupil and the eye <NUM> acts as the last element in the optical chain and converts the light from the pupil into an image on the eye's retina as a virtual display.

The waveguide <NUM> facilitates light transmission between the imager and the eye. One or more waveguides can be utilized in the near-eye display system because they are transparent and because they are generally small and lightweight (which is desirable in applications such as HMD devices where size and weight is generally sought to be minimized for reasons of performance and user comfort). The waveguide <NUM> can enable the imager <NUM> to be located out of the way, for example, on the side of the user's head or near the forehead, leaving only a relatively small, light, and transparent waveguide optical element in front of the eyes. In one implementation, the waveguide <NUM> operates using a principle of total internal reflection, as shown in <FIG>, so that light can be coupled among the various optical elements in the system <NUM>.

<FIG> shows a view of an illustrative exit pupil expander (EPE) <NUM>. EPE <NUM> receives an input optical beam from the imager <NUM> through optics <NUM> (e.g., magnifying and/or collimating optics) as an entrance pupil to produce one or more output optical beams with expanded exit pupil in one or two directions relative to the exit pupil of the imager (in general, the input may include more than one optical beam which may be produced by separate sources). The expanded exit pupil typically facilitates a virtual display to be sufficiently sized to meet the various design requirements such as image resolution, field of view, and the like of a given optical system while enabling the imager and associated components to be relatively light and compact.

The EPE <NUM> is configured, in this illustrative example, to support binocular operation for both the left and right eyes which may support stereoscopic viewing. Components that may be utilized for stereoscopic operation such as scanning mirrors, lenses, filters, beam splitters, MEMS devices, or the like are not shown in <FIG> for sake of clarity in exposition. The EPE <NUM> utilizes two out-coupling gratings, <NUM>L and <NUM>R, that are supported on a waveguide <NUM> and a central in-coupling grating <NUM>. The in-coupling and out-coupling gratings may be configured using multiple DOEs, as described below. While the EPE <NUM> is depicted as having a planar configuration, other shapes may also be utilized including, for example, curved or partially spherical shapes, in which case the gratings disposed thereon are non-co-planar.

As shown in <FIG>, the EPE <NUM> may be configured to provide an expanded exit pupil in two directions (i.e., along each of a first and second coordinate axis). As shown, the exit pupil is expanded in both the vertical and horizontal directions. It may be understood that the terms "left," "right," "direction," "horizontal," and "vertical" are used primarily to establish relative orientations in the illustrative examples shown and described herein for ease of description. These terms may be intuitive for a usage scenario in which the user of the near eye display device is upright and forward facing, but less intuitive for other usage scenarios. The listed terms are not to be construed to limit the scope of the configurations (and usage scenarios therein) of near-eye display features utilized in the present waveguide display. The entrance pupil to the EPE <NUM> at the in-coupling grating <NUM> is generally described in terms of FOV, for example, using horizontal FOV, vertical FOV, or diagonal FOV as shown in <FIG>.

The present waveguide display is arranged with color capabilities using an RGB (red, green, blue) color model. Accordingly, the waveguide display is configured using three layers <NUM>, <NUM>, and <NUM> using a discrete waveguide plate to propagate each of red, green, and blue image light. In alternative arrangements, two layers may be utilized in which red light is propagated in one waveguide plate and mixed blue and green light is propagated in another waveguide plate.

Turning now to various implementation details of the present waveguide display, <FIG> shows an illustrative example of a visor <NUM> that incorporates an internal near-eye display system that is used in a head mounted display (HMD) device <NUM> worn by a user <NUM>. The visor <NUM>, in this example, is sealed to protect the internal near-eye display system. The visor <NUM> typically interfaces with other components of the HMD device (not shown) such as head mounting/retention systems and other subsystems including sensors, power management, controllers, etc., as illustratively described in conjunction with <FIG> and <FIG>. Suitable interface elements (not shown) including snaps, bosses, screws and other fasteners, etc. may also be incorporated into the visor <NUM>.

The visor <NUM> includes see-through front and rear shields, <NUM> and <NUM> respectively, that can be molded using transparent materials to facilitate unobstructed vision to the optical displays and the surrounding real world environment. Treatments may be applied to the front and rear shields such as tinting, mirroring, anti-reflective, anti-fog, and other coatings, and various colors and finishes may also be utilized. The front and rear shields are affixed to a chassis <NUM> shown in the disassembled view in <FIG>.

The sealed visor <NUM> can physically protect sensitive internal components, including a near-eye display system <NUM> (shown in <FIG>) when the HMD device is used in operation and during normal handling for cleaning and the like. The near-eye display system <NUM> includes left and right optical displays <NUM> and <NUM> that respectively provide virtual world images to the user's left and right eyes. The visor <NUM> can also protect the near-eye display system <NUM> from environmental elements and damage should the HMD device be dropped or bumped, impacted, etc..

As shown in <FIG>, the rear shield <NUM> is configured in an ergonomically suitable form to interface with the user's nose, and nose pads and/or other comfort features can be included (e.g., molded-in and/or added-on as discrete components). The sealed visor <NUM> can also incorporate some level of optical diopter curvature (i.e., eye prescription) within the molded shields in some cases.

<FIG> shows an illustrative optical display <NUM> having multiple DOEs that are used with, or incorporated as a part of, a waveguide <NUM> to provide in-coupling, expansion of the exit pupil in two directions, and out-coupling. The optical display <NUM> may be utilized in an exit pupil expander that is included in the near eye display system <NUM> (<FIG>) to provide virtual world images to one of the user's eyes. Each DOE is an optical element comprising a periodic structure that can modulate various properties of light in a periodic pattern such as the direction of optical axis, optical path length, and the like.

The FOV is split into two portions - a left portion and a right portion - at the in-coupling DOE <NUM>. Each of the left and right portions uses an FOV that propagates within the DOEs without leakage. The left and right portions are then optically stitched together at an out-coupling DOE <NUM> to provide an extended FOV for the virtual images that are out-coupled from the display <NUM> to the user's eye. Thus, in one non-limiting illustrative example, the diagonal FOV of each of the left and right portions may be <NUM> degrees and the extended FOV of the optically stitched images is <NUM> degrees.

A left intermediate DOE <NUM> extends from the center of the waveguide <NUM> to its left edge. A right intermediate DOE <NUM> extends from the center to the right edge of the waveguide <NUM>. Each of the left and right intermediate DOEs expands the exit pupil in a first direction along a first coordinate axis. The left and right intermediate DOEs <NUM> and <NUM> couple light between the in-coupling DOE <NUM> and the single out-coupling DOE <NUM> that is centrally located towards the bottom portion of the waveguide <NUM>, as shown. The out-coupling DOE <NUM> expands the exit pupil in a second direction along a second coordinate axis and couples light out of the waveguide to the user's eye.

As shown in <FIG>, the partial FOVs are propagated left and right (as respectively indicated by reference numerals <NUM> and <NUM>) and the full FOV is propagated downward (as indicated by reference numeral <NUM>). The in-coupling DOE <NUM> includes linear grating features on one side which couples incident image light to the left and right, as well as linear grating features on the opposite side which couple light downwards. Alternatively, crossed (i.e., two-dimensional) grating features may be used on one or both surfaces of the in-coupling DOE <NUM> to couple light both sideways and downwards.

While the approach shown in <FIG> works satisfactorily for a single waveguide plate, when two or three waveguide plates are utilized in support of the RGB color model, quite significant cross-coupling between colors can occur which can decrease image quality. In particular, parameters describing display uniformity and MTF (modulation transfer function) are typically sub-optimal. The root cause of the cross-coupling is direct coupling by the in-coupling DOE downwards in which red light cross-couples into the waveguide plate for green light to cause the MTF degradation. Most of the red light, especially around the center of the FOV, has an evanescent diffraction order when coupled sideways, but is propagating when coupled downwards. Accordingly, the present waveguide display is configured to avoid direct coupling of image light downward.

The present waveguide display can utilize grating profiles as shown in <FIG> for the in-coupling DOE. <FIG> shows an edge view of a single-sided in-coupling DOE <NUM> which is split into two portions <NUM> and <NUM> that have slanted grating features that are slanted in opposite directions. This "split-slant" configuration typically provides enhanced coupling efficiency when coupling light towards the lateral edges of the in-coupling DOE, as representatively indicated by arrows <NUM> and <NUM> where the arrow width indicates relative intensity. <FIG> shows split-slant grating features <NUM> and <NUM> on both sides of a two-sided in-coupling DOE <NUM>. Other grating features may be utilized in alternative implementations for in-coupling, including, for example, refraction index-modulated, refraction index-switched, or polarization gratings.

Because the in-coupling DOE is configured to avoid coupling image light directly downwards, the intermediate DOEs are configured to enable light to be spread back towards the center region of the waveguide. Otherwise, as shown in <FIG>, banding and/or dark stripes (indicated by reference numeral <NUM>) can appear in the out-coupling DOE <NUM> below the in-coupling DOE <NUM> where light is absent.

<FIG> shows a waveguide display <NUM> that uses an arrangement of multiple DOEs on a waveguide <NUM>. An in-coupling DOE <NUM>, which can comprise one-sided or two-sided split-slant grating, is configured to couple image light from an imager sideways to the left and right to respective intermediate DOEs. The intermediate DOEs comprise two parts or portions - an upper portion adjacent to the in-coupling DOE and a lower portion that is adjacent to a single out-coupling DOE <NUM>. Thus, as shown, four intermediate DOEs are utilized - a right upper intermediate DOE <NUM>, a right lower intermediate DOE <NUM>, a left upper intermediate DOE <NUM>, and left lower intermediate DOE <NUM>. The intermediate DOEs are configured to provide an expanded exit pupil in a first direction for left and right portions of the FOV of the image light. The out-coupling DOE <NUM> provides exit pupil expansion in a second direction and out-couples image light to the user's eye across the full FOV.

In this illustrative example, a grating vector of the left lower intermediate DOE <NUM> has a direction that is the same, or is almost the same, as the grating vector of the right upper intermediate DOE <NUM>. This alignment of grating vectors enables light to be guided back to the center of the waveguide <NUM>, as shown by the arrows (representatively indicated by reference numeral <NUM>). In an alternative implementation, the left and right lower intermediate DOEs can be combined and be configured as two-sided gratings with grating features on both sides. One surface has a grating vector with the same or similar direction as that of the right upper intermediate DOE <NUM>. The opposite surface has a grating vector with the same or similar direction as that of the left upper intermediate DOE <NUM>. In another alternative implementation, a combined left and right lower intermediate DOE may be configured as a one-sided or two-sided crossed grating.

The waveguide display <NUM> with left and right, upper and lower intermediate DOEs can provide increased display uniformity from reduced cross-coupling (e.g., red light into the green waveguide plate). However, some angles within the FOV is evanescent within the waveguide which can lead to dark regions from some eye positions. While some improvement can be realized by increasing the distance between the in-coupling and out-coupling DOEs, this may be sub-optimal in some implementations due to increased waveguide plate size. For example, as shown in <FIG> when using a single- or dual-sided in-coupling DOE <NUM>, incident image light is not coupled to the left as some FOV angles are evanescent within the waveguide <NUM>.

The lack of leftward coupling may be addressed by using an in-coupling DOE <NUM>, as shown in <FIG>, that includes linear grating features in a parallel configuration on a first surface of a two-sided in-coupling DOE <NUM> and linear grating features in chevron configuration on the second surface on the opposite side. The directions of the grating vectors are different for the first and second surfaces of the in-coupling DOE. The first (e.g., front) surface couples incident image light while the second (e.g., back) surface steers in-coupled light at the first diffraction order downwards, but as zeroth diffraction order waves are evanescent, they are not coupled downwards. Since light must go through the first diffraction order, this configuration enables coupling of the light downwards without the cross-coupling of red light into the green waveguide plate since the red light is evanescent.

The grating features used in the DOEs in the present waveguide display with increased uniformity and reduced cross-coupling between colors may take various suitable forms. For example, <FIG> shows a profile of straight (i.e., non-slanted) grating features <NUM> (referred to as grating bars, grating lines, or simply "gratings"), that are formed in a substrate <NUM>. By comparison, <FIG> shows grating features <NUM> formed in a substrate <NUM> that have an asymmetric profile. That is, the gratings may be slanted (i.e., non-orthogonal) relative to a plane of the waveguide. In implementations where the waveguide is non-planar, then the gratings may be slanted relative to a direction of light propagation in the waveguide. Asymmetric grating profiles can also be implemented using blazed gratings, or echelette gratings, in which grooves are formed to create grating features with asymmetric triangular or sawtooth profiles. In <FIG>, the grating period is represented by d, the grating height by h, bar width by c, and the filling factor by f, where f =c/d. The slanted gratings in <FIG> may be described by slant angles □<NUM> and □<NUM>.

<FIG> show various illustrative two-dimensional (2D) diffraction gratings which may be utilized in some implementations of the in-coupling DOE. The 2D grating may also be utilized to impart polarization sensitivity to a DOE (e.g., an in-coupling DOE and/or an intermediate DOE). The 2D gratings in the <FIG> are intended to be illustrative and not limiting, and it is contemplated that variations from the 2D gratings shown may also be utilized. Gratings may include symmetric and/or asymmetric features including slanted gratings (i.e., gratings having walls that are non-orthogonal according to one or more predetermined angles to a plane of the waveguide) and blazed gratings (i.e., gratings having asymmetric triangular or sawtooth profiles) in some cases. Various suitable surface relief contours, filling factors, grating periods, and grating dimensions can also be utilized according to the needs of a particular implementation.

<FIG> shows a 2D grating <NUM> that includes quadrangular elements that project from a substrate. The quadrangular elements can also be configured to be asymmetric such as being slanted or blazed. Non-quadrangular three-dimensional geometries (both symmetric and asymmetric) may also be utilized for a 2D grating including, for example, cylindrical elements, polygonal elements, elliptical elements, or the like. For example, <FIG> shows a 2D grating <NUM> that includes pyramidal elements, and <FIG> shows a 2D grating <NUM> that includes elements that have a blazed profile in each of the x and z directions. Gratings may also have elements with curved profiles, as shown in the illustrative 2D grating <NUM> in <FIG>.

<FIG> is a flowchart of an illustrative method <NUM>. Unless specifically stated, the methods or steps shown in the flowchart and described in the accompanying text are not constrained to a particular order or sequence. In addition, some of the methods or steps thereof can occur or be performed concurrently and not all the methods or steps have to be performed in a given implementation depending on the requirements of such implementation and some methods or steps may be optionally utilized.

At step <NUM>, image light from an imager is received as an entrance pupil at an in-coupling DOE. At step <NUM>, the FOV of the received image light is split into left and right FOV portions at the in-coupling DOE. The left and right FOV portions of the received image light is steered by the in-coupling DOE to respective left and right intermediate DOEs.

At step <NUM>, the left FOV portion of the in-coupled image light is propagated in the left intermediate DOE so that an exit pupil of the left FOV portion is expanded along the horizontal axis and the light is diffracted downward along the vertical axis to an out-coupling DOE. At this step, a red component of the image light is evanescent and thus is non-propagating along the vertical axis in the left intermediate DOE. At step <NUM>, the right FOV portion of the in-coupled image light is propagated in the right intermediate DOE so that the exit pupil of the right FOV portion is expanded along the horizontal axis and the light is diffracted downward along the vertical axis to the out-coupling DOE.

At step <NUM>, an exit pupil of the left and right FOV portions of the propagating image light is expanded along the vertical axis in the out-coupling DOE. At step <NUM>, image light for the left and right FOV portions is output from the out-coupling DOE. The output image light has expanded pupil relative to the entrance pupil along the horizontal and vertical axes. The out-coupling DOE operates to optically stitch the left and right FOV portions together to provide a full FOV that is extended (i.e., having a larger angular FOV) compared to conventional optical displays.

<FIG> shows one particular illustrative example of a see-through, mixed reality or virtual reality HMD device <NUM>, and <FIG> shows a functional block diagram of the device <NUM>. HMD device <NUM> comprises one or more lenses <NUM> that form a part of a see-through display subsystem <NUM>, so that images may be displayed using lenses <NUM> (e.g. using projection onto lenses <NUM>, one or more waveguide systems, such as a near-eye display system, incorporated into the lenses <NUM>, and/or in any other suitable manner). HMD device <NUM> further comprises one or more outward-facing image sensors <NUM> configured to acquire images of a background scene and/or physical environment being viewed by a user, and may include one or more microphones <NUM> configured to detect sounds, such as voice commands from a user. Outward-facing image sensors <NUM> may include one or more depth sensors and/or one or more two-dimensional image sensors. In alternative arrangements, as noted above, a mixed reality or virtual reality display system, instead of incorporating a see-through display subsystem, may display mixed reality or virtual reality images through a viewfinder mode for an outward-facing image sensor.

The HMD device <NUM> may further include a gaze detection subsystem <NUM> configured for detecting a direction of gaze of each eye of a user or a direction or location of focus, as described above. Gaze detection subsystem <NUM> may be configured to determine gaze directions of each of a user's eyes in any suitable manner. For example, in the illustrative example shown, a gaze detection subsystem <NUM> includes one or more glint sources <NUM>, such as infrared light sources, that are configured to cause a glint of light to reflect from each eyeball of a user, and one or more image sensors <NUM>, such as inward-facing sensors, that are configured to capture an image of each eyeball of the user. Changes in the glints from the user's eyeballs and/or a location of a user's pupil, as determined from image data gathered using the image sensor(s) <NUM>, may be used to determine a direction of gaze.

In addition, a location at which gaze lines projected from the user's eyes intersect the external display may be used to determine an object at which the user is gazing (e.g. a displayed virtual object and/or real background object). Gaze detection subsystem <NUM> may have any suitable number and arrangement of light sources and image sensors. In some implementations, the gaze detection subsystem <NUM> may be omitted.

The HMD device <NUM> may also include additional sensors. HMD device <NUM> may comprise a global positioning system (GPS) subsystem <NUM> to allow a location of the HMD device <NUM> to be determined. This may help to identify real-world objects, such as buildings, etc. that may be located in the user's adjoining physical environment.

The HMD device <NUM> may further include one or more motion sensors <NUM> (e.g., inertial, multi-axis gyroscopic, or acceleration sensors) to detect movement and position/orientation/pose of a user's head when the user is wearing the system as part of a mixed reality or virtual reality HMD device. Motion data may be used, potentially along with eye-tracking glint data and outward-facing image data, for gaze detection, as well as for image stabilization to help correct for blur in images from the outward-facing image sensor(s) <NUM>. The use of motion data may allow changes in gaze location to be tracked even if image data from outward-facing image sensor(s) <NUM> cannot be resolved.

In addition, motion sensors <NUM>, as well as microphone(s) <NUM> and gaze detection subsystem <NUM>, also may be employed as user input devices, such that a user may interact with the HMD device <NUM> via gestures of the eye, neck and/or head, as well as via verbal commands in some cases. It may be understood that sensors illustrated in <FIG> and <FIG> and described in the accompanying text are included for the purpose of example and are not intended to be limiting in any manner, as any other suitable sensors and/or combination of sensors may be utilized to meet the needs of a particular implementation. For example, biometric sensors (e.g., for detecting heart and respiration rates, blood pressure, brain activity, body temperature, etc.) or environmental sensors (e.g., for detecting temperature, humidity, elevation, UV (ultraviolet) light levels, etc.) may be utilized in some implementations.

The HMD device <NUM> can further include a controller <NUM> such as one or more processors having a logic subsystem <NUM> and a data storage subsystem <NUM> in communication with the sensors, gaze detection subsystem <NUM>, display subsystem <NUM>, and/or other components through a communications subsystem <NUM>. The communications subsystem <NUM> can also facilitate the display system being operated in conjunction with remotely located resources, such as processing, storage, power, data, and services. That is, in some implementations, an HMD device can be operated as part of a system that can distribute resources and capabilities among different components and subsystems.

The storage subsystem <NUM> may include instructions stored thereon that are executable by logic subsystem <NUM>, for example, to receive and interpret inputs from the sensors, to identify location and movements of a user, to identify real objects using surface reconstruction and other techniques, and dim/fade the display based on distance to objects so as to enable the objects to be seen by the user, among other tasks.

The HMD device <NUM> is configured with one or more audio transducers <NUM> (e.g., speakers, earphones, etc.) so that audio can be utilized as part of a mixed reality or virtual reality experience. A power management subsystem <NUM> may include one or more batteries <NUM> and/or protection circuit modules (PCMs) and an associated charger interface <NUM> and/or remote power interface for supplying power to components in the HMD device <NUM>.

It may be appreciated that the HMD device <NUM> is described for the purpose of example, and thus is not meant to be limiting. It may be further understood that the display device may include additional and/or alternative sensors, cameras, microphones, input devices, output devices, etc. than those shown without departing from the scope of the present arrangement. Additionally, the physical configuration of an HMD device and its various sensors and subcomponents may take a variety of different forms without departing from the scope of the present arrangement.

As shown in <FIG>, near-eye display systems with waveguide displays having increased uniformity and reduced cross-coupling between colors can be used in a mobile or portable electronic device <NUM>, such as a mobile phone, smartphone, personal digital assistant (PDA), communicator, portable Internet appliance, hand-held computer, digital video or still camera, wearable computer, computer game device, specialized bring-to-the-eye product for viewing, or other portable electronic device. As shown, the portable device <NUM> includes a housing <NUM> to house a communication module <NUM> for receiving and transmitting information from and to an external device, or a remote system or service (not shown).

The portable device <NUM> may also include an image processor <NUM> using one or more processors for handling the received and transmitted information, and a virtual display system <NUM> to support viewing of images. The virtual display system <NUM> can include a micro-display or an imager <NUM> and an optical engine <NUM>. The image processor <NUM> may be operatively connected to the optical engine <NUM> to provide image data, such as video data, to the imager <NUM> to display an image thereon. An EPE <NUM> can be optically linked to an optical engine <NUM>. The EPE may utilize a waveguide display having increased uniformity and reduced cross-coupling between colors as described herein.

Waveguide displays having increased uniformity and reduced cross-coupling between colors may also be utilized in non-portable devices, such as gaming devices, multimedia consoles, personal computers, vending machines, smart appliances, Internet-connected devices, and home appliances, such as an oven, microwave oven and other appliances, and other non-portable devices.

Various exemplary embodiments of the present waveguide display with increased uniformity and reduced cross-coupling between colors are now presented by way of illustration and not as an exhaustive list of all embodiments. An example includes a near-eye display system configured to provide image light from an imager within a field of view (FOV) having first and second axes, to an eye of a user of the near-eye display system, comprising: a substrate of optical material configured as a waveguide for guiding image light in the near-eye display system; an in-coupling diffractive optical element (DOE) disposed on the substrate and configured to couple image light over an entirety of the FOV into the waveguide; a left intermediate DOE disposed on the substrate and optically coupled to the in-coupling DOE to receive image light for a left portion of the FOV, in which the left intermediate DOE is configured to expand the received image light along the first axis; a right intermediate DOE disposed on the substrate and optically coupled to the in-coupling DOE to receive image light for a right portion of the FOV, in which the right intermediate DOE is configured to expand the received image light along the first axis; and an out-coupling DOE disposed on the substrate and configured to receive the image light for the left and right portions of the FOV respectively from the left and right intermediate DOEs, the out-coupling DOE configured for pupil expansion of the image light for each of the left and right portions of the FOV along the second axis, and further configured to out-couple image light for combined left and right portions over the entirety of the FOV from the waveguide, wherein the left intermediate DOE includes a top portion and a bottom portion, the top portion disposed in the waveguide adjacent to the in-coupling DOE, and the bottom portion disposed in the waveguide adjacent to the out-coupling DOE, and wherein the right intermediate DOE includes a top portion and a bottom portion, the top portion disposed in the waveguide adjacent to the in-coupling DOE, and the bottom portion disposed in the waveguide adjacent to the out-coupling DOE.

In another example, the left intermediate DOE and right intermediate DOE each interface with the in-coupling DOE around respective portions the of in-coupling DOE's perimeter. The in-coupling DOE is centrally located between the left intermediate DOE and right intermediate DOE. In another example, a left upper intermediate DOE laterally extends from the in-coupling DOE and a right upper intermediate DOE laterally extends from the in-coupling DOE. In another example, the substrate is planar. In another example, the left and right intermediate DOEs are disposed on opposite sides of the substrate. In another example, the in-coupling DOE comprises a front side and a back side that are disposed on opposite sides of the substrate, the front side and back side having respective grating vectors with different directions.

A further example includes an electronic device configured for displaying image light for virtual images in a full field of view (FOV) comprising a first partial FOV and a second partial FOV, the full FOV having horizontal and vertical directions, comprising: a waveguide on which multiple diffractive optical elements (DOEs) are disposed, the waveguide comprising a plurality of plates configured to respectively guide red, green, and blue color components of the image light; an in-coupling DOE disposed on the waveguide and configured with grating features on a first portion of the in-coupling DOE and grating features on a second portion of the in-coupling DOE, the grating features on the first portion having different grating vectors from grating features on the second portion, the grating features on the first portion configured to in-couple image light into the waveguide and the grating features on the second portion configured to steer the in-coupled image light in the vertical direction while minimizing cross-coupling among the color components; a first intermediate DOE configured to expand the first partial FOV in the horizontal direction; and a second intermediate DOE configured to expand the second partial FOV in the horizontal direction.

In another example, the first portion comprises a first surface and the second portion comprises a second surface and the in-coupling DOE is configured as a two-sided DOE and the first and second surfaces are located on opposing sides. In another example, the grating features on the first or second surface of the in-coupling DOE are arranged in a split-slant configuration. In another example, the grating features on the first or second surface of the in-coupling DOE are arranged as one of refraction index-modulated, refraction index-switchable, or polarization-sensitive gratings. In another example, the electronic device further includes an out-coupling DOE disposed on the waveguide and configured to expand the image light for each of the first and second partial FOVs in the vertical direction and further to out-couple image light from the waveguide across the full FOV with an expanded exit pupil in the horizontal and vertical directions. In another example, the first intermediate DOE comprises a first portion disposed in the waveguide adjacent to the in-coupling DOE and a second portion disposed in the waveguide adjacent to the out-coupling DOE and the second intermediate DOE comprises a first portion disposed in the waveguide adjacent to the in-coupling DOE and a second portion disposed in the waveguide adjacent to the out-coupling DOE. In another example, the first portion of the first intermediate DOE and the second portion of the second intermediate DOE share a common grating vector direction.

A further example includes a method of operating a waveguide display with left, right, top, and bottom boundaries and vertical and horizontal axes, comprising: receiving image light having an entrance pupil within a full field of view (FOV) at an in-coupling diffractive optical element (DOE) disposed in a waveguide, the image light having red, green, and blue components; using the in-coupling DOE, splitting the FOV of the received image light into a left FOV portion and a right FOV portion; using the in-coupling DOE, steering the left FOV portion of the in-coupled image light horizontally to the left and steering the right FOV portion of the in-coupled image light horizontally to the right; propagating the left FOV portion of the in-coupled image light in a left intermediate DOE disposed in the waveguide in which an exit pupil of the left FOV portion is expanded along the horizontal axis and diffracted downward along the vertical axis to an out-coupling DOE, wherein a red component of the image light is evanescent and non-propagating along the vertical axis; propagating the right FOV portion of the in-coupled image light in a right intermediate DOE disposed in the waveguide in which an exit pupil of the right FOV portion is expanded along the horizontal axis and diffracted downward along the vertical axis to the out-coupling DOE; expanding the exit pupil of the left and right FOV portions of the propagating image light along the vertical axis in the out-coupling DOE disposed in the waveguide; and outputting image light for the left and right FOV portions with an expanded exit pupil relative to the entrance pupil at the in-coupling DOE along the horizontal and vertical axes using the out-coupling DOE.

In another example, image light propagates in opposite directions in the left and right intermediate DOEs or the image light propagates with orthogonal states of polarization in the left and right intermediate DOEs. In another example, the in-coupling DOE is centrally disposed on an exit pupil expander and the left and right intermediate DOEs extend laterally from the in-coupling DOE on the exit pupil. In another example, the method further includes stitching the left and right FOV portions together to provide a full FOV at the out-coupling DOE. In another example, the stitched FOV portions are in one of symmetric or asymmetric configuration in the full FOV. In another example, the splitting comprises selection of the FOV propagation based on evanescent diffraction order.

Claim 1:
An optical display (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) for displaying image light for a virtual image in a full field of view, FOV, the display comprising: multiple diffractive optical elements, DOEs, wherein each DOE is an optical element comprising a periodic structure that can modulate properties of light in a periodic pattern; and
a waveguide (<NUM>) configured to provide in-coupling, expansion of an exit pupil in two directions, and out-coupling, wherein the FOV is split into a left portion and a right portion at an in-coupling DOE (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>);
wherein each of the left and right portions expands the exit pupil in a first direction along a first coordinate axis;
characterized in that
the waveguide comprises a plurality of plates configured to respectively guide red, green, and blue color components of the image light;
the left and right portions are then optically stitched together at an out-coupling DOE (<NUM>) to provide an extended FOV for the virtual image that is out-coupled to the user's eye;
the left portion extends from the center of the waveguide (<NUM>) to its left edge and the right portion extends from the center to the right edge of the waveguide (<NUM>);
the left and right portions couple light between the in-coupling DOE (<NUM>) and the out-coupling DOE (<NUM>) that is centrally located towards the bottom portion of the waveguide (<NUM>);
the out-coupling DOE (<NUM>) expands the exit pupil in a second direction along a second coordinate axis and couples light out of the waveguide (<NUM>) to the user's eye; and in that
zeroth diffraction order waves of the red, green and blue color components are evanescent and are not coupled downward by the in coupling DOE (<NUM>) as compared to first order diffraction waves which are coupled downwards.