Athermalization concept for polymer eyepieces used in augmented or mixed reality devices

Abstract

An embodiment of the present disclosure provides a system and method for a display. In an embodiment, the display system includes a frame, an eyepiece coupled to the frame, and a first adhesive bond disposed between the frame and the eyepiece. The eyepiece can include a light entry region and a light exit region. The first adhesive bond can be disposed along a first portion of a circumference of the eyepiece, the first portion of the circumference of the eyepiece abutting the light entry region such that the first adhesive bond is configured to maintain a position of the light entry region relative to the frame.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 63 / 160,419, filed March 12, 2021, the contents of both of which are incorporated herein by reference in their entireties.

[0002] Field The present disclosure relates generally to systems for displaying visual information, and more particularly to an eyepiece for displaying visual information in an augmented or mixed reality environment. [Background technology]

[0003] background Virtual environments are ubiquitous in computing environments, being used in video games (where the virtual environment may represent a game world); maps (where the virtual environment may represent a terrain through which a virtual environment is navigated); simulations (where the virtual environment may simulate a real environment); digital storytelling (where virtual characters may interact with one another in a virtual environment); and many other applications. Modern computer users are generally comfortable perceiving and interacting with virtual environments. However, a user's experience with a virtual environment may be limited by the technology for presenting the virtual environment. For example, conventional displays (e.g., 2D display screens) and audio systems (e.g., fixed speakers) may not be able to realize a virtual environment in a way that creates an engaging, realistic, and immersive experience.

[0004] Virtual reality ("VR"), augmented reality ("AR"), mixed reality ("MR"), and related technologies (collectively "XR") share the ability to present to a user of an XR system sensory information corresponding to a virtual environment represented by data in a computer system. This disclosure contemplates a distinction between VR, AR, and MR systems (although some systems may be classified as VR in one aspect (e.g., visual aspects) and AR or MR in another aspect (e.g., audio aspects) simultaneously). As used herein, a VR system presents a virtual environment that replaces the user's real environment in at least one aspect. For example, a VR system may present a user with a view of the virtual environment while simultaneously obscuring the view of the real environment, such as with a light-blocking head-mounted display. Similarly, a VR system may present a user with audio corresponding to the virtual environment while simultaneously blocking (attenuating) audio from the real environment.

[0005] VR systems may experience various drawbacks that result from replacing the user's real environment with a virtual environment. One drawback is the feeling of sickness that can occur when the user's field of view in the virtual environment no longer corresponds to the state of their inner ear, which detects the user's balance and orientation in the real (not virtual) environment. Similarly, users may experience disorientation in a VR environment where they cannot directly see their own body and limbs (the view that the user relies on to feel "grounded" in the real environment). Another drawback is the computational burden (e.g., storage, processing power) imposed on a VR system that must present a complete 3D virtual environment, especially in real-time applications that seek to immerse the user in the virtual environment. Similarly, such an environment may need to reach very high standards of realism to be considered immersive, as users tend to be sensitive to even slight imperfections in the virtual environment, any of which may detract from the sense of immersion in the virtual environment. Furthermore, another drawback of VR systems is the inability of such applications of the system to take advantage of the wide range of sensory data in the real environment, such as the various sights and sounds experienced in the real world. A related drawback is that VR systems may struggle to create a shared environment in which multiple users can interact, because users who share physical space in the real environment may not be able to see or interact with each other directly in the virtual environment.

[0006] As used herein, an AR system presents a virtual environment that overlaps or overlays the real environment in at least one aspect. For example, an AR system can present a user with a view of the virtual environment overlaid on the user's view of the real environment, such as a see-through head-mounted display that presents a display image while allowing light to pass through the display and into the user's eyes. Similarly, an AR system can present a user with audio corresponding to the virtual environment while simultaneously mixing audio from the real environment. Similarly, as used herein, an MR system, like an AR system, can present a virtual environment that overlaps or overlays the real environment in at least one aspect, and further allow the virtual environment in the MR system to interact with the real environment in at least one aspect. For example, a virtual character in the virtual environment can flip a light switch in the real environment, turning on or off a corresponding light bulb in the real environment. As another example, the virtual character can respond (e.g., with facial expressions) to audio signals in the real environment. By maintaining the presentation of the real environment, AR and MR systems can avoid some of the aforementioned shortcomings of VR systems. For example, visual cues from the real environment (including the user's own body) can remain visible, reducing user nausea because such systems do not need to present the user with a fully realized 3D environment in order to be immersed. Additionally, AR and MR systems can create new applications that leverage real-world sensory input (e.g., views and sounds of scenery, objects, and other users) to augment that input.

[0007] It can be difficult to present a virtual environment in a realistic manner to create an immersive experience for a user in a robust and cost-effective manner. For example, a head mounted display can include an optical system having one or more multi-layer glass eyepieces. The glass eyepieces can be expensive and fragile components. For example, each layer can be manufactured through a complex process that includes multiple steps to achieve a diffraction grating and associated films to effectively project a digital image to a user. Furthermore, glass can be a fragile component that is prone to failure or damage without careful handling of the head mounted display. Thus, there is a need for an eyepiece that is easier to manufacture and more robust than a glass eyepiece, without sacrificing the quality of the digital image. Summary of the Invention [Means for solving the problem]

[0008] overview Disclosed herein are systems and methods for displays, such as head-wearable devices. An exemplary display can include a frame, an eyepiece coupled to the frame, and a first adhesive bond disposed between the frame and the eyepiece. The eyepiece can include a light entrance region and a light exit region. The first adhesive bond can be disposed along a first portion of a circumference of the eyepiece, the first portion of the circumference of the eyepiece abutting the light entrance region such that the first adhesive bond is configured to maintain the position of the light entrance region relative to the frame. The embodiments disclosed herein can provide a robust, easy-to-manufacture display system that can provide consistent digital image quality during use. [Brief description of the drawings]

[0009] [Figure 1A] 1A-1C illustrate an exemplary mixed reality environment in accordance with one or more embodiments of the present disclosure. [Figure 1B]1A-1C illustrate an exemplary mixed reality environment in accordance with one or more embodiments of the present disclosure. [Figure 1C] 1A-1C illustrate an exemplary mixed reality environment in accordance with one or more embodiments of the present disclosure.

[0010] [Figure 2A] 2A-2D illustrate components of an example mixed reality system that can be used to generate and interact with a mixed reality environment in accordance with one or more embodiments of the present disclosure. [Figure 2B] 2A-2D illustrate components of an example mixed reality system that can be used to generate and interact with a mixed reality environment in accordance with one or more embodiments of the present disclosure. [Figure 2C] 2A-2D illustrate components of an example mixed reality system that can be used to generate and interact with a mixed reality environment in accordance with one or more embodiments of the present disclosure. [Figure 2D] 2A-2D illustrate components of an example mixed reality system that can be used to generate and interact with a mixed reality environment in accordance with one or more embodiments of the present disclosure.

[0011] [Figure 3A] FIG. 3A illustrates an example mixed reality handheld controller that can be used to provide input to a mixed reality environment, in accordance with one or more embodiments of the present disclosure.

[0012] [Figure 3B] FIG. 3B illustrates an example auxiliary unit that can be used with an example mixed reality system in accordance with one or more embodiments of the present disclosure.

[0013] [Figure 4] FIG. 4 illustrates an example functional block diagram of an example mixed reality system in accordance with one or more embodiments of the present disclosure.

[0014] [Diagram 5] FIG. 5 illustrates an example eyepiece for an example mixed reality system in accordance with one or more embodiments of the present disclosure.

[0015] [Figure 6] FIG. 6 illustrates an example eyepiece for an example mixed reality system in accordance with one or more embodiments of the present disclosure.

[0016] [Figure 7] FIG. 7 illustrates an example eyepiece for an example mixed reality system in accordance with one or more embodiments of the present disclosure.

[0017] [Figure 8] FIG. 8 illustrates an example eyepiece and mounting scheme for an example mixed reality system in accordance with one or more embodiments of the present disclosure.

[0018] [Figure 9] FIG. 9 illustrates an example eyepiece and mounting scheme for an example mixed reality system in accordance with one or more embodiments of the present disclosure.

[0019] [Figure 10] FIG. 10 illustrates an example eyepiece and mounting scheme for an example mixed reality system in accordance with one or more embodiments of the present disclosure.

[0020] [Figure 11] FIG. 11 illustrates an example eyepiece and mounting scheme for an example mixed reality system in accordance with one or more embodiments of the present disclosure.

[0021] [Figure 12] FIG. 12 illustrates an example eyepiece and mounting scheme for an example mixed reality system in accordance with one or more embodiments of the present disclosure.

[0022] [Figure 13] 13A to 13C show an example of the bimetal phenomenon.

[0023] [Figure 14] FIG. 14 is a chart illustrating an example performance degradation based on increasing layer-to-layer CTE variation, in accordance with one or more embodiments of the present disclosure.

[0024] [Figure 15] FIG. 15 illustrates an example eyepiece for an example mixed reality system in accordance with one or more embodiments of the present disclosure.

[0025] [Figure 16] FIG. 16 illustrates an example eyepiece for an example mixed reality system in accordance with one or more embodiments of the present disclosure.

[0026] [Figure 17] FIG. 17 illustrates an example eyepiece for an example mixed reality system in accordance with one or more embodiments of the present disclosure.

[0027] [Figure 18] FIG. 18 illustrates an example eyepiece for an example mixed reality system in accordance with one or more embodiments of the present disclosure.

[0028] [Figure 19] FIG. 19 illustrates an example eyepiece for an example mixed reality system in accordance with one or more embodiments of the present disclosure.

[0029] [Figure 20] FIG. 20 illustrates an example eyepiece for an example mixed reality system in accordance with one or more embodiments of the present disclosure.

[0030] [Figure 21]FIG. 21 illustrates an example eyepiece for an example mixed reality system in accordance with one or more embodiments of the present disclosure.

[0031] [Figure 22] FIG. 22 illustrates an example eyepiece for an example mixed reality system in accordance with one or more embodiments of the present disclosure.

[0032] [Figure 23] FIG. 23 illustrates an example eyepiece for an example mixed reality system in accordance with one or more embodiments of the present disclosure.

[0033] [Figure 24] FIG. 24 illustrates an example eyepiece for an example mixed reality system in accordance with one or more embodiments of the present disclosure.

[0034] [Diagram 25] FIG. 25 illustrates an example eyepiece for an example mixed reality system in accordance with one or more embodiments of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] Detailed Description In the following description of the examples, reference is made to the accompanying drawings which form a part hereof, and which show, by way of illustration, specific examples which may be practiced. It is to be understood that other examples may be used and structural changes may be made without departing from the scope of the disclosed examples. Mixed Reality Environment

[0036] Like all humans, a user of a mixed reality system is present in a real environment, i.e., the three-dimensional portion of the "real world" and all of its contents that are perceptible by the user. For example, the user perceives the real environment using the normal human senses (sight, sound, touch, taste, smell) and interacts with the real environment by moving his or her body within the real environment. Locations in the real environment can be described as coordinates in a coordinate space. For example, the coordinates can include latitude, longitude, and altitude relative to sea level; distances in three orthogonal dimensions from a reference point; or other suitable values. Similarly, a vector can describe a quantity that has a direction and magnitude in a coordinate space.

[0037] The computing device may maintain a representation of the virtual environment, for example, in a memory associated with the device. As used herein, a virtual environment is a computational representation of a three-dimensional space. The virtual environment may include a representation of any objects, actions, signals, parameters, coordinates, vectors, or other properties associated with that space. In some examples, the circuitry (e.g., a processor) of the computing device may maintain and update the state of the virtual environment. That is, the processor may determine the state of the virtual environment at a second time t1 based on data associated with the virtual environment and / or input provided by a user at a first time t0. For example, if an object in the virtual environment is located at a first coordinate at time t0 and has certain programmed physical parameters (e.g., mass, coefficient of friction), input received from the user may indicate that a force should be applied to the object in a directional vector. The processor may apply the laws of kinematics to determine the position of the object at time t1 using basic mechanics. The processor may determine the state of the virtual environment at time t1 using any suitable information known about the virtual environment and / or any suitable input. In maintaining and updating the state of the virtual environment, the processor may execute any suitable software, including software related to creating and deleting virtual objects in the virtual environment; software (e.g., scripts) for defining the behavior of virtual objects or characters in the virtual environment; software for defining the behavior of signals (e.g., audio signals) in the virtual environment; software for creating and updating parameters associated with the virtual environment; software for generating audio signals in the virtual environment; software for handling input and output; software for implementing network operations; software for applying asset data (e.g., animation data for moving virtual objects over time); or many other possibilities.

[0038] An output device, such as a display or speaker, can present any or all aspects of the virtual environment to the user. For example, the virtual environment can include virtual objects (which may include representations of objects such as inanimate objects; people; animals; lights, etc.) that can be presented to the user. The processor can determine a view of the virtual environment (e.g., corresponding to a "camera" having an origin coordinate, a view axis, and a frustum) and render on the display a viewable scene of the virtual environment corresponding to that view. Any suitable rendering technique can be used for this purpose. In some examples, the viewable scene may include only some virtual objects in the virtual environment and exclude certain other virtual objects. Similarly, the virtual environment can include audio aspects that can be presented to the user as one or more audio signals. For example, a virtual object in the virtual environment may generate a sound that originates from the object's position coordinates (e.g., a virtual character may speak or generate a sound effect). Alternatively, the virtual environment may be associated with musical cues or ambient sounds that may or may not be associated with a particular location. The processor can determine an audio signal corresponding to a "listener" coordinate, e.g., an audio signal that corresponds to the synthesis of sounds in the virtual environment and that has been mixed and processed to simulate the audio signal that a listener would hear at the listener coordinate, and present the audio signal to the user via one or more speakers.

[0039] Because the virtual environment exists only as a computational construct, the user cannot directly perceive the virtual environment using normal senses. Instead, the user can only indirectly perceive the virtual environment, for example, as presented to the user by a display, a speaker, a haptic output device, etc. Similarly, the user cannot directly touch, manipulate, or interact with the virtual environment, but can provide input data via an input device or sensor to a processor that can use the device or sensor data to update the virtual environment. For example, a camera sensor can provide optical data indicating that the user is attempting to move an object in the virtual environment, and the processor can use that data to cause the object to respond accordingly in the virtual environment.

[0040] A mixed reality system can present a user with a mixed reality environment ("MRE") that combines aspects of the real environment and the virtual environment, for example, using a see-through display and / or one or more speakers (which may be incorporated, for example, in a wearable head device). In some embodiments, the one or more speakers may be external to the head-mounted wearable unit. As used herein, an MRE is a simultaneous representation of a real environment and a corresponding virtual environment. In some examples, the corresponding real environment and virtual environment share a single coordinate space. In some examples, the real coordinate space and the corresponding virtual coordinate space are related to each other by a transformation matrix (or other suitable representation). Thus, a single coordinate (in some examples, together with the transformation matrix) can define a first location in the real environment and a second corresponding location in the virtual environment, or vice versa.

[0041] In an MRE, a virtual object (e.g., in a virtual environment associated with the MRE) may correspond to a real object (e.g., in a real environment associated with the MRE). For example, if the real environment of the MRE includes a real lamp post (real object) at a location coordinate, the virtual environment of the MRE may include a virtual lamp post (virtual object) at a corresponding location coordinate. As used herein, a real object in combination with a corresponding virtual object constitutes a "mixed reality object." A virtual object need not perfectly match or align with a corresponding real object. In some examples, a virtual object may be a simplified version of a corresponding real object. For example, if a real environment includes a real lamp post, the corresponding virtual object may include a cylinder of approximately the same height and radius as the real lamp post (reflecting that a lamp post may be approximately cylindrical in shape). Simplifying virtual objects in this manner may increase computational efficiency and simplify calculations performed on such virtual objects. Additionally, in some examples of MREs, not all real objects in the real environment are associated with a corresponding virtual object. Similarly, in some instances of the MRE, not all virtual objects in the virtual environment are associated with corresponding real-world objects, i.e., some virtual objects may exist only in the MRE's virtual environment without a real-world counterpart.

[0042] In some examples, virtual objects may have characteristics that are sometimes drastically different from the characteristics of the corresponding real object. For example, a real environment in an MRE may include a green, two-armed cactus (a thorny, inanimate object), while the corresponding virtual object in the MRE may have the characteristics of a green, two-armed virtual character with human facial features and a blank expression. In this example, the virtual object resembles its corresponding real object in certain characteristics (color, number of arms), but other characteristics (facial features, personality) differ from the real object. In this way, virtual objects have the potential to represent real objects in creative, abstract, exaggerated, or imaginative ways, or to give behaviors (e.g., human personality) to otherwise inanimate real objects. In some examples, virtual objects may be purely imaginative creations with no real-world counterpart (e.g., a virtual monster in a virtual environment, possibly in a position that corresponds to an empty space in the real environment).

[0043] Compared to VR systems that present a virtual environment to a user while obscuring the real environment, mixed reality systems that present an MRE offer the advantage that the real environment remains perceptible while the virtual environment is presented. Thus, a user of a mixed reality system can experience and interact with the corresponding virtual environment using visual and audio cues associated with the real environment. By way of example, as discussed above, a user of a VR system may struggle to perceive or interact with virtual objects displayed in a virtual environment because the user cannot directly perceive or interact with the virtual environment, whereas a user of an MR system may find it intuitive and natural to interact with virtual objects by seeing, hearing, and touching the corresponding real objects in their own real environment. This level of interactivity can enhance the sense of immersion, connection, and engagement with the virtual environment. Similarly, by presenting a real environment and a virtual environment simultaneously, a mixed reality system can reduce the negative psychological feelings (e.g., cognitive dissonance) and negative physical feelings (e.g., sickness) associated with a VR system. Mixed reality systems further offer many possibilities for applications that may augment or modify real-world experiences.

[0044] 1A illustrates an exemplary real-world environment 100 in which a user 110 uses a mixed reality system 112. The mixed reality system 112 may include a display (e.g., a see-through display) and one or more speakers, as well as one or more sensors (e.g., a camera), for example, as described below. The illustrated real-world environment 100 includes a rectangular room 104A in which the user 110 is standing, and real objects 122A (a lamp), 124A (a table), 126A (a sofa), and 128A (a painting). The room 104A further includes a position coordinate 106 that may be considered as the origin of the real-world environment 100. As illustrated in FIG. 1A, an environment / world coordinate system 108 (including an x-axis 108X, a y-axis 108Y, and a z-axis 108Z) with its origin 106 (world coordinate) may define the coordinate space of the real-world environment 100. In some embodiments, the origin 106 of the environment / world coordinate system 108 may correspond to where the mixed reality system 112 was powered on. In some embodiments, the origin 106 of the environment / world coordinate system 108 may be reset during operation. In some examples, the user 110 may be considered a real object in the real environment 100. Similarly, the body parts (e.g., hands, feet) of the user 110 may be considered a real object in the real environment 100. In some examples, a user / listener / head coordinate system 114 (including an x-axis 114X, a y-axis 114Y, and a z-axis 114Z) with an origin at a point 115 (e.g., a user / listener / head coordinate) may define a coordinate space for the user / listener / head in which the mixed reality system 112 is located. An origin 115 of the user / listener / head coordinate system 114 may be defined with respect to one or more components of the mixed reality system 112. For example, the origin 115 of the user / listener / head coordinate system 114 may be defined relative to the display of the mixed reality system 112, such as during an initial calibration of the mixed reality system 112. A matrix (which may include translation and quaternion or other rotation matrices), or other suitable representation, may characterize the transformation between the user / listener / head coordinate system 114 space and the environment / world coordinate system 108 space.In some embodiments, the left ear coordinates 116 and right ear coordinates 117 may be defined relative to the origin 115 of the user / listener / head coordinate system 114. A matrix (which may include translation matrices and quaternion matrices or other rotation matrices), or other suitable representation, may characterize the transformation between the left ear coordinates 116 and right ear coordinates 117 and the user / listener / head coordinate system 114 space. The user / listener / head coordinate system 114 may simplify the representation of the position relative to the user's head or head-worn device, for example, relative to the environment / world coordinate system 108. Using simultaneous localization and mapping (SLAM), visual odometry, or other techniques, the transformation between the user coordinate system 114 and the environment coordinate system 108 may be determined and updated in real time.

[0045] 1B illustrates an exemplary virtual environment 130 corresponding to the real environment 100. The illustrated virtual environment 130 includes a virtual rectangular room 104B corresponding to the real rectangular room 104A, a virtual object 122B corresponding to the real object 122A, a virtual object 124B corresponding to the real object 124A, and a virtual object 126B corresponding to the real object 126A. Metadata associated with the virtual objects 122B, 124B, 126B may include information derived from the corresponding real objects 122A, 124A, and 126A. The virtual environment 130 further includes a virtual monster 132 that does not correspond to any real object in the real environment 100. A real object 128A in the real environment 100 does not correspond to any virtual object in the virtual environment 130. A persistent coordinate system 133 (including an x-axis 133X, a y-axis 133Y, and a z-axis 133Z) with point 134 as its origin (persistent coordinates) may define the coordinate space of the virtual content. The origin 134 of the persistent coordinate system 133 may be defined relative to / relative to one or more real objects, such as real object 126A. A matrix (which may include translation matrices and quaternion matrices or other rotation matrices), or other suitable representation, may characterize the transformation between the persistent coordinate system 133 space and the environment / world coordinate system 108 space. In some embodiments, each of the virtual objects 122B, 124B, 126B, and 132 may have its own persistent coordinate point relative to the origin 134 of the persistent coordinate system 133. In some embodiments, there may be multiple persistent coordinate systems, and each of the virtual objects 122B, 124B, 126B, and 132 may have its own persistent coordinate point relative to one or more persistent coordinate systems.

[0046] The persistent coordinate data may be coordinate data that is persistent with respect to the physical environment. The persistent coordinate data may be used by the MR system (e.g., MR system 112, 200) to position persistent virtual content, which may not be tied to the movement of the display on which the virtual object is displayed. For example, a two-dimensional screen may only display the virtual object relative to its position on the screen. As the two-dimensional screen moves, the virtual content may move with the screen. In some embodiments, the persistent virtual content may be displayed in a corner of a room. The MR user may look into the corner, see the virtual content, look out of the corner (where the virtual content may no longer be visible because the user's head movement may have moved the virtual content from within the user's field of view to a position outside the user's field of view), or look behind and see the virtual content in the corner (similar to how a real object may behave).

[0047] In some embodiments, the persistent coordinate data (e.g., persistent coordinate system and / or persistent coordinate frame) may include an origin and three axes. For example, the persistent coordinate system may be assigned by the MR system to the center of the room. In some embodiments, the user may move around the room, exit the room, and re-enter the room, and the persistent coordinate system may remain at the center of the room (e.g., because it persists relative to the physical environment). In some embodiments, virtual objects may be displayed using a transformation to the persistent coordinate data that may enable the display of persistent virtual content. In some embodiments, the MR system may use simultaneous localization and mapping to generate the persistent coordinate data (e.g., the MR system may assign a persistent coordinate system to a point in space). In some embodiments, the MR system may map the environment by generating persistent coordinate data at regular intervals (e.g., the MR system may assign a persistent coordinate system in a grid, and a persistent coordinate system may be within at least 5 feet of another persistent coordinate system).

[0048] In some embodiments, the persistent coordinate data may be generated by the MR system and transmitted to a remote server. In some embodiments, the remote server may be configured to receive the persistent coordinate data. In some embodiments, the remote server may be configured to synchronize persistent coordinate data from multiple observation instances. For example, multiple MR systems may map the same room with persistent coordinate data and transmit the data to a remote server. In some embodiments, the remote server may use this observation data to generate standard persistent coordinate data that may be based on one or more observations. In some embodiments, the standard persistent coordinate data may be more accurate and / or reliable than a single observation of the persistent coordinate data. In some embodiments, the standard persistent coordinate data may be transmitted to one or more MR systems. For example, an MR system may use image recognition and / or position data to recognize that it is located in a room that has corresponding standard persistent coordinate data (e.g., because other MR systems have previously mapped the room). In some embodiments, the MR system may receive standard persistent coordinate data corresponding to its location from the remote server.

[0049] 1A and 1B, the environment / world coordinate system 108 defines a shared coordinate space for both the real environment 100 and the virtual environment 130. In the illustrated example, the coordinate space has its origin at point 106. Furthermore, the coordinate space is defined by the same three orthogonal axes (108X, 108Y, 108Z). Thus, a first location in the real environment 100 and a second corresponding location in the virtual environment 130 can be described with respect to the same coordinate space. This simplifies the identification and display of corresponding locations in the real environment and the virtual environment, since the same coordinates can be used to identify both locations. However, in some examples, the corresponding real environment and virtual environment need not use a shared coordinate space. For example, in some examples (not shown), a matrix (which may include a translation matrix and a quaternion matrix or other rotation matrix), or other suitable representation, can characterize the transformation between the real environment coordinate space and the virtual environment coordinate space.

[0050] 1C illustrates an exemplary MRE 150 that simultaneously presents aspects of real environment 100 and virtual environment 130 to user 110 via mixed reality system 112. In the illustrated example, MRE 150 simultaneously presents real objects 122A, 124A, 126A, and 128A from real environment 100 (e.g., through a transparent portion of a display of mixed reality system 112) and virtual objects 122B, 124B, 126B, and 132 from virtual environment 130 (e.g., through an actively displayed portion of a display of mixed reality system 112) to user 110. As described above, origin 106 serves as the origin of a coordinate space corresponding to MRE 150, and coordinate system 108 defines the x-, y-, and z-axes of the coordinate space.

[0051] In the illustrated example, the mixed reality object includes corresponding pairs of real and virtual objects (i.e., 122A / 122B, 124A / 124B, 126A / 126B) that occupy corresponding positions in the coordinate space 108. In some examples, both real and virtual objects may be visible to the user 110 simultaneously. This may be desirable, for example, when a virtual object presents information designed to augment the view of the corresponding real object (such as in a museum application where a virtual object presents a missing piece of an old damaged sculpture). In some examples, a virtual object (122B, 124B, and / or 126B) may be displayed to occlude the corresponding real object (122A, 124A, and / or 126A) (e.g., via active pixelated occlusion using pixelated occlusion shutters). This may be desirable, for example, when a virtual object serves as a visual replacement for a corresponding real object (such as in an interactive storytelling application where inanimate real objects become "living" characters).

[0052] In some examples, a real object (e.g., 122A, 124A, 126A) may be associated with virtual content or helper data that may not necessarily constitute a virtual object. The virtual content or helper data may facilitate processing or handling of the virtual object in a mixed reality environment. For example, such virtual content may include a two-dimensional representation of the corresponding real object; a custom asset type associated with the corresponding real object; or statistical data associated with the corresponding real object. This information may enable or facilitate computations involving the real object without incurring unnecessary computational overhead.

[0053] In some examples, the presentations described above may also incorporate audio aspects. For example, in MRE 150, virtual monster 132 may be associated with one or more audio signals, such as footstep effects that are generated as the monster walks around MRE 150. As described further below, a processor in mixed reality system 112 may calculate an audio signal that corresponds to a mixed and processed combination of all such sounds within MRE 150 and present the audio signal to user 110 via one or more speakers included in mixed reality system 112 and / or one or more external speakers. Exemplary Mixed Reality System

[0054] An exemplary mixed reality system 112 may include a wearable head device (e.g., a wearable augmented reality or mixed reality head device) with a display (which may include left and right see-through displays, which may be near-eye displays, and associated components for coupling light from the displays to the user's eyes); left and right speakers (e.g., positioned adjacent the user's left and right ears, respectively); an inertial measurement unit (IMU) (e.g., mounted on the temple arms of a head device); a quadrature coil-type electromagnetic receiver (e.g., mounted on the left temple piece); left and right cameras (e.g., depth (time of flight) cameras) pointed away from the user; and left and right eye cameras pointed toward the user (e.g., for detecting the user's eye movements). However, the mixed reality system 112 may incorporate any suitable display technology, and any suitable sensors (e.g., optical, infrared, acoustic, LIDAR, EOG, GPS, magnetic). Additionally, the mixed reality system 112 may incorporate networking capabilities (e.g., Wi-Fi capabilities) for communicating with other devices and systems, including other mixed reality systems. The mixed reality system 112 may further include a battery (which may be attached to an auxiliary unit, such as a belt pack designed to be worn around the user's waist), a processor, and a memory. The wearable head device of the mixed reality system 112 may include a tracking component, such as an IMU or other suitable sensor, configured to output a set of coordinates of the wearable head device relative to the user's environment. In some examples, the tracking component may provide input to a processor that executes simultaneous localization and mapping (SLAM) and / or visual odometry algorithms. In some examples, the mixed reality system 112 may also include a handheld controller 300 and / or an auxiliary unit 320, which may be a wearable belt pack, as described further below.

[0055] 2A-2D show components of an exemplary mixed reality system 200 (which may correspond to the mixed reality system 112) that may be used to present an MRE (which may correspond to the MRE 150) or other virtual environment to a user. FIG. 2A shows a perspective view of a wearable head device 2102 included in the exemplary mixed reality system 200. FIG. 2B shows a top view of the wearable head device 2102 worn on a user's head 2202. FIG. 2C shows a front view of the wearable head device 2102. FIG. 2D shows an end view of an exemplary eyepiece 2110 of the wearable head device 2102. As shown in FIGS. 2A-2C, the exemplary wearable head device 2102 includes an exemplary left eyepiece (e.g., a left transparent waveguide set eyepiece) 2108 and an exemplary right eyepiece (e.g., a right transparent waveguide set eyepiece) 2110. Each eyepiece 2108 and 2110 can include a transmissive element through which the real environment can be seen, as well as a display element for presenting a display (e.g., via image-wise modulated light) that overlaps with the real environment. In some examples, such display elements can include surface diffractive optical elements for controlling the flow of image-wise modulated light. For example, the left eyepiece 2108 can include a left internal coupling grating set 2112, a left orthogonal pupil dilation (OPE) grating set 2120, and a left exit (output) pupil dilation (EPE) grating set 2122. As used herein, pupil may refer to the exit of light from an optical element such as a grating set or reflector. Similarly, the right eyepiece 2110 can include a right internal coupling grating set 2118, a right OPE grating set 2114, and a right EPE grating set 2116. The image-wise modulated light can be transmitted to the user's eye via the internal coupling gratings 2112 and 2118, the OPE 2114 and 2120, and the EPE 2116 and 2122. Each internal coupling grating set 2112, 2118 can be configured to deflect light towards its corresponding OPE grating set 2120, 2114.Each OPE grating set 2120, 2114 can be designed to gradually deflect light downward toward its associated EPE 2122, 2116, thereby extending the exit pupil formed horizontally. Each EPE 2122, 2116 can be configured to gradually redirect at least a portion of the light received from its corresponding OPE grating set 2120, 2114 toward a user's eyebox position (not shown) defined behind the eyepiece 2108, 2110, thereby extending the exit pupil formed at the eyebox vertically. Alternatively, instead of the internal coupling grating sets 2112 and 2118, the OPE grating sets 2114 and 2120, and the EPE grating sets 2116 and 2122, the eyepieces 2108 and 2110 can include other arrangements of gratings and / or refractive and reflective mechanisms to control the coupling of image-wise modulated light into the user's eye.

[0056] In some examples, the wearable head device 2102 can include a left temple arm 2130 and a right temple arm 2132, with the left temple arm 2130 including a left speaker 2134 and the right temple arm 2132 including a right speaker 2136. A quadrature coil electromagnetic receiver 2138 can be disposed in the left temple piece or another suitable location in the wearable head unit 2102. An inertial measurement unit (IMU) 2140 can be disposed in the right temple arm 2132 or another suitable location in the wearable head device 2102. The wearable head device 2102 can also include a left depth (e.g., time-of-flight) camera 2142 and a right depth camera 2144. The depth cameras 2142, 2144 can be suitably oriented in different directions to together cover a wider field of view.

[0057] In the example shown in Figures 2A-2D, a left source 2124 of image-wise modulated light can be optically coupled to the left eyepiece 2108 via a left internal coupling grating set 2112, and a right source 2126 of image-wise modulated light can be optically coupled to the right eyepiece 2110 via a right internal coupling grating set 2118. The sources 2124, 2126 of image-wise modulated light can include, for example, a fiber optic scanner; a projector including an electronic light modulator such as a digital light processing (DLP) chip or a liquid crystal on silicon (LCoS) modulator; or a light-emitting display such as a micro light-emitting diode (μLED) or micro organic light-emitting diode (μOLED) panel coupled to the internal coupling grating set 2112, 2118 using one or more lenses per side. The input coupling grating set 2112, 2118 can deflect light from the sources 2124, 2126 of image-wise modulated light to an angle that exceeds the critical angle of total internal reflection (TIR) ​​of the eyepiece 2108, 2110. The OPE grating sets 2114, 2120 gradually deflect the light propagating by TIR downwards towards the EPE grating sets 2116, 2122. The EPE grating sets 2116, 2122 gradually couple the light towards the user's face, including the pupils of the user's eyes.

[0058] In some examples, as shown in FIG. 2D, each of the left eyepiece 2108 and the right eyepiece 2110 includes multiple waveguides 2402. For example, each eyepiece 2108, 2110 can include multiple individual waveguides, each dedicated to a respective color channel (e.g., red, blue, and green). In some examples, each eyepiece 2108, 2110 can include multiple sets of such waveguides, each set configured to impart a different wavefront curvature to the emitted light. The wavefront curvature may be convex with respect to the user's eye, for example, to present a virtual object located at a distance in front of the user (e.g., a distance corresponding to the inverse of the wavefront curvature). In some examples, the EPE grating sets 2116, 2122 can include curved grating grooves that achieve a convex wavefront curvature by modifying the pointing vector of the exiting light across each EPE.

[0059] In some examples, stereoscopically calibrated left and right eye images can be presented to the user through the image-wise light modulators 2124, 2126 and eyepieces 2108, 2110 to create the perception that the displayed content is three-dimensional. By selecting a waveguide (and thus corresponding wavefront curvature) such that the virtual object is displayed at a distance close to that shown by the stereoscopic left and right images, the perceived realism of the presentation of the three-dimensional virtual object can be enhanced. This technique can also reduce sickness experienced by some users, which may be caused by differences between the depth perception cues provided by the stereoscopic left and right eye images and the autonomic regulation of the human eye (e.g., focus dependent on object distance).

[0060] FIG. 2D shows an end view from above of the right eyepiece 2110 of the exemplary wearable head device 2102. As shown in FIG. 2D, the plurality of waveguides 2402 can include a first subset 2404 of three waveguides and a second subset 2406 of three waveguides. The two subsets 2404, 2406 of waveguides can be differentiated by different EPE gratings featuring different grating line curvatures to impart different wavefront curvatures to the exiting light. Within each subset 2404, 2406 of waveguides, each waveguide can be used to couple a different spectral channel (e.g., one of the red, green, and blue spectral channels) to the user's right eye 2206. (Although not shown in FIG. 2D, the structure of the left eyepiece 2108 is similar to that of the right eyepiece 2110.)

[0061] FIG. 3A illustrates an exemplary handheld controller component 300 of the mixed reality system 200. In some examples, the handheld controller 300 includes a grip portion 346 and one or more buttons 350 disposed along a top surface 348. In some examples, the buttons 350 may be configured for use as optical tracking targets, for example, to track six degrees of freedom (6DOF) movement of the handheld controller 300 in conjunction with a camera or other optical sensor, which may be mounted on a head unit (e.g., the wearable head device 2102) of the mixed reality system 200. In some examples, the handheld controller 300 includes a tracking component (e.g., an IMU or other suitable sensor) for detecting a position or orientation, such as a position or orientation relative to the wearable head device 2102. In some examples, such a tracking component may be disposed within a handle of the handheld controller 300 and / or may be mechanically coupled to the handheld controller. The handheld controller 300 can be configured to provide one or more output signals corresponding to one or more of: a button press state; or a position, orientation, and / or movement of the handheld controller 300 (e.g., via an IMU). Such output signals may be used as inputs to a processor of the mixed reality system 200. Such inputs may correspond to the position, orientation, and / or movement of the handheld controller (and, by extension, to the position, orientation, and / or movement of a user's hand holding the controller). Such inputs may also correspond to a user pressing a button 350.

[0062] 3B illustrates an exemplary auxiliary unit 320 of the mixed reality system 200. The auxiliary unit 320 may include a battery for providing energy to operate the system 200 and may include a processor for executing programs for operating the system 200. As shown, the exemplary auxiliary unit 320 includes a clip 2128 for attaching the auxiliary unit 320 to a user's belt, or the like. Other form factors are suitable for the auxiliary unit 320 and will be apparent, including form factors that do not involve attaching the unit to a user's belt. In some examples, the auxiliary unit 320 is coupled to the wearable head device 2102 via a multi-conduit cable, which may include, for example, electrical wires and optical fibers. A wireless connection between the auxiliary unit 320 and the wearable head device 2102 may also be used.

[0063] In some examples, the mixed reality system 200 may include one or more microphones for detecting sounds and providing corresponding signals to the mixed reality system. In some examples, the microphones may be attached to or integrated with the wearable head device 2102 and may be configured to detect the user's voice. In some examples, the microphones may be attached to or integrated with the handheld controller 300 and / or the auxiliary unit 320. Such microphones may be configured to detect environmental sounds, ambient noise, the user's or a third party's voice, or other sounds.

[0064] FIG. 4 illustrates an example functional block diagram that may correspond to an example mixed reality system, such as the mixed reality system 200 described above (which may correspond to the mixed reality system 112 with respect to FIG. 1). As shown in FIG. 4, an example handheld controller 400B (which may correspond to the handheld controller 300 ("totem")) includes a totem-to-wearable head device six degrees of freedom (6DOF) totem subsystem 404A, and an example wearable head device 400A (which may correspond to the wearable head device 2102) includes a totem-to-wearable head device 6DOF subsystem 404B. In this example, the 6DOF totem subsystem 404A and the 6DOF subsystem 404B cooperate to determine six coordinates (e.g., three translational offsets and rotations along three axes) of the handheld controller 400B relative to the wearable head device 400A. The six degrees of freedom may be expressed relative to the coordinate system of the wearable head device 400A. The three translational offsets may be represented as X, Y, and Z offsets in such a coordinate system, as a translation matrix, or some other representation. The rotational degrees of freedom may be represented as a sequence of yaw, pitch, and roll rotations, as a rotation matrix, as a quaternion, or some other representation. In some examples, the wearable head device 400A; one or more depth cameras 444 (and / or one or more non-depth cameras) included in the wearable head device 400A; and / or one or more optical targets (e.g., the buttons 350 of the handheld controller 400B described above, or a dedicated optical target included in the handheld controller 400B) may be used for 6DOF tracking. In some examples, the handheld controller 400B may include a camera, as described above, and the wearable head device 400A may include an optical target for optical tracking in conjunction with the camera. In some examples, the wearable head device 400A and the handheld controller 400B each include a set of three orthogonally oriented solenoids used to wirelessly transmit and receive three identifiable signals.By measuring the relative magnitudes of the three distinguishable signals received at each of the coils used for receiving, the 6DOF of the wearable head device 400A relative to the handheld controller 400B can be determined. Additionally, the 6DOF totem subsystem 404A can include an inertial measurement unit (IMU) useful for providing improved accuracy and / or more timely information regarding rapid movements of the handheld controller 400B.

[0065] In some embodiments, the wearable system 400 can include a microphone array 407 that can include one or more microphones disposed on the headgear device 400A. In some embodiments, the microphone array 407 can include four microphones. Two microphones can be disposed on the front of the headgear 400A and two microphones can be disposed on the back of the headgear 400A (e.g., one on the left rear and one on the right rear). In some embodiments, the signals received by the microphone array 407 can be transmitted to the DSP 408. The DSP 408 can be configured to perform signal processing on the signals received from the microphone array 407. For example, the DSP 408 can be configured to perform noise reduction, acoustic echo cancellation, and / or beamforming on the signals received from the microphone array 407. The DSP 408 can be configured to transmit the signals to the processor 416.

[0066] In some examples, it may be necessary to transform coordinates from a local coordinate space (e.g., a coordinate space fixed relative to the wearable head device 400A) to an inertial coordinate space (e.g., a coordinate space fixed relative to the real environment), e.g., to compensate for movement of the wearable head device 400A relative to the coordinate system 108. For example, such a transformation may be necessary for the display of the wearable head device 400A to present the virtual object in an expected position and orientation relative to the real environment (e.g., a virtual person sitting in a real chair and facing forward, regardless of the position and orientation of the wearable head device) rather than in a fixed position and orientation on the display (e.g., the same position in the bottom right corner of the display) in order to maintain the illusion that the virtual object is present in the real environment (and does not appear unnaturally placed in the real environment as the wearable head device 400A moves and rotates). In some examples, the compensatory transformation between coordinate spaces can be determined by processing images from the depth camera 444 using SLAM and / or visual odometry procedures to determine the transformation of the wearable head device 400A relative to the coordinate system 108. In the example shown in FIG. 4, the depth camera 444 can be coupled to the SLAM / visual odometry block 406 and can provide images to the block 406. An implementation of the SLAM / visual odometry block 406 can include a processor configured to process this image and determine the position and orientation of the user's head, which can be used to identify a transformation between the head coordinate space and another coordinate space (e.g., an inertial coordinate space). Similarly, in some examples, an additional source of information regarding the user's head pose and position is obtained from the IMU 409. Information from the IMU 409 can be integrated with information from the SLAM / visual odometry block 406 to provide improved accuracy and / or more timely information regarding rapid adjustments to the user's head pose and position.

[0067] In some examples, the depth camera 444 can provide 3D images to a hand gesture tracker 411, which can be implemented in a processor of the wearable head device 400A. The hand gesture tracker 411 can identify the user's hand gestures, for example, by matching the 3D images received from the depth camera 444 with stored patterns representing the hand gestures. Other suitable techniques for identifying the user's hand gestures will be apparent.

[0068] In some examples, the one or more processors 416 may be configured to receive data from the 6DOF headgear subsystem 404B, the IMU 409, the SLAM / visual odometry block 406, the depth camera 444, and / or the hand gesture tracker 411 of the wearable head device. The processor 416 may also receive and send control signals from the 6DOF totem system 404A. The processor 416 may be wirelessly coupled to the 6DOF totem system 404A, such as in an example where the handheld controller 400B is not connected. The processor 416 may further communicate with additional components, such as an audiovisual content memory 418, a graphical processing unit (GPU) 420, and / or a digital signal processor (DSP) sound spatializer 422. The DSP sound spatializer 422 may be coupled to a head-related transfer function (HRTF) memory 425. The GPU 420 may include a left channel output coupled to a left source 424 of image-wise modulated light and a right channel output coupled to a right source 426 of image-wise modulated light. The GPU 420 may output stereoscopic image data to the image-wise modulated light sources 424, 426, for example, as described above with reference to FIGS. 2A-2D. The DSP audio spatializer 422 may output audio to the left speaker 412 and / or the right speaker 414. The DSP audio spatializer 422 may receive an input from the processor 419 indicating a direction vector from the user to a virtual sound source (which may be moved by the user, for example, via the handheld controller 320). Based on the direction vector, the DSP audio spatializer 422 may determine a corresponding HRTF (e.g., by accessing an HRTF or by interpolating multiple HRTFs). The DSP audio spatializer 422 may then apply the determined HRTF to an audio signal, such as an audio signal corresponding to a virtual sound generated by a virtual object.This can increase the realism and presence of virtual sounds by incorporating the user's relative position and orientation to the virtual sounds in a mixed reality environment, i.e., by presenting virtual sounds that match the user's expectations of how the virtual sounds would sound if they were real sounds in a real environment.

[0069] 4, one or more of the processor 416, GPU 420, DSP audio spatializer 422, HRTF memory 425, and audiovisual content memory 418 may be included in an auxiliary unit 400C (which may correspond to auxiliary unit 320 described above). The auxiliary unit 400C may include a battery 427 for powering its components and / or for powering the wearable head device 400A or the handheld controller 400B. Including such components in an auxiliary unit that may be worn on the user's waist can limit the size and weight of the wearable head device 400A, which in turn can reduce fatigue on the user's head and neck.

[0070] 4 illustrates elements corresponding to various components of an exemplary mixed reality system, various other suitable arrangements of these components will be apparent to those skilled in the art. For example, elements illustrated in FIG. 4 as being associated with the auxiliary unit 400C can instead be associated with the wearable head device 400A or the handheld controller 400B. Furthermore, some mixed reality systems may dispense with the handheld controller 400B or the auxiliary unit 400C entirely. Such variations and modifications should be understood to fall within the scope of the disclosed examples. Example Eyepiece

[0071] A wearable head device or head mounted display of an exemplary mixed reality system (e.g., mixed reality system 200) may include an optical system having an eyepiece for presenting images to a user via a display. Figures 5-7 show examples of eyepieces that may be used in a wearable head device (e.g., wearable head device 2102) according to an embodiment of the present disclosure.

[0072] FIG. 5 illustrates an exemplary eyepiece 500 that may be used in a wearable head device (e.g., wearable head device 2102). The eyepiece 500 may include multiple layers 510. The multiple layers 510 may be arranged in parallel to form an eyepiece stack. As used herein, the term eyepiece may refer to an eyepiece stack formed from multiple eyepiece layers. In some embodiments, one or more of the multiple layers of the eyepiece may include a light entrance region 501 and a light exit region 505. The light entrance region 501 may refer to the area of ​​the eyepiece 500 that receives light from a light source. The light exit region 505 may refer to the area that projects light from the eyepiece 500.

[0073] FIG. 6 shows an enlarged cross-sectional view of an eyepiece stack 600 having one or more layers. The eyepiece stack 600 can include multiple layers separated by gaps 607. In one or more embodiments, the gaps can be maintained by multiple edge spacers 609 and pillar spacers 611 disposed between each layer. In some embodiments, the eyepiece stack can include one or more layers 610, 620. In some embodiments, different layers can perform different functions. For example, the eyepiece stack 600 can include one or more active layers 610 and one or more cover layers 620. As shown in the figure, the eyepiece stack 600 can include three active layers 610 and two cover layers 620. The cover layers 620 can be positioned to form an outer surface of the eyepiece stack 600. For example, a first cover layer 620 can be positioned on an outer surface of the eyepiece stack 600 proximate to the external environment, and a second cover layer 620 can be positioned on an opposing outer surface of the eyepiece stack 600 proximate to the user's eye when the wearable head device is in use. The active layer 610 can be disposed between cover layers 620. In this manner, the cover layers 620 can protect the active layer 610 from damage, such as, for example, stress, scratches, cuts, cracks, and the like.

[0074] As shown in the figures, in some examples, the eyepiece 600 may include at least three active layers 610 and two cover layers 620. The eyepiece may further include spacers disposed between each layer to maintain a gap 607 between the layers. The spacers may include edge spacers 609 and pillar spacers 611. The edge spacers 609 may be provided at the periphery of the eyepiece stack 600, e.g., the edges of the eyepiece, to maintain a consistent gap between each layer. In some embodiments, each of the layers 610, 620 may be bonded to the edge spacers 609. These bonds may allow the eyepiece 600 to be handled and mounted as a single unit. In some embodiments, the edge spacers may be formed integrally with the layers. The pillar spacers 611 may be provided across the faces of the layers to maintain a consistent gap 607 between each layer. Maintaining a consistent gap 607 across the periphery and faces of each layer may help ensure that light from each layer is projected in the same direction.

[0075] FIG. 7 illustrates a plan view of an active layer 710 of an eyepiece (e.g., eyepiece 500). Layer 710 may include a light entrance region 701 and a light exit region 705. Light entrance region 701 and light exit region 705 may correspond to light entrance region 501 and light exit region 505 described with respect to eyepiece 500. Light entrance region 701 may be configured to receive light from a light source (not shown). The received light may be incoupled into layer 710 via light entrance region 701. Incoupled light 703 may be projected across layer 710 toward light exit region 705. Light exit region 705 may be configured to project light from layer 710 and the eyepiece (e.g., eyepiece 500) toward the eye of a user wearing a head mounted display.

[0076] As discussed above, an eyepiece, e.g., eyepiece 500 or 600, may include multiple layers having one or more active layers. In some embodiments, each active layer may be configured to diffract or couple light of a particular wavelength into a corresponding waveguide. For example, the optics of the head mounted display may include at least a light source (e.g., light sources 2124, 2126 of FIG. 2A) configured to direct light to the eyepiece. In some embodiments, the light source may be configured to emit light of one or more wavelengths, and the entrance region 701 may be tuned to one of the wavelengths. For example, the entrance region 701 may be configured to diffract light corresponding to the wavelength emitted by the light source. In some embodiments, multiple active layers may be stacked together, and each of the light entrance regions 701 may be tuned to a different wavelength corresponding to the one or more wavelengths emitted by the light source. In this manner, the eyepiece, e.g., eyepiece 500, may form a multi-color digital image that can be presented to a user wearing the head mounted display.

[0077] In some embodiments, one or more layers of the eyepiece (e.g., eyepiece 500 or 600) may be formed from a polymer. As discussed above, glass eyepieces can be fragile and expensive. For example, glass eyepieces included in head mounted displays may be prone to damage due to periodic wear, e.g., dynamic forces from use, handling, and dropping on the head mounted display. Furthermore, fabricating the glass layer may involve numerous complex manufacturing steps to achieve the diffraction gratings and associated films for incoupling and outcoupling light to and from the layer. In comparison, polymer layers can be more robust and easier to fabricate than glass. For example, polymer materials can absorb more energy (approximately 5-8 times) than glass before breaking. Furthermore, the polymer layer can be relatively easily formed into various shapes using a mold, and the diffraction gratings for incoupling and outcoupling light can be molded directly onto the polymer layer.

[0078] Although polymers offer advantages over glass, there are also challenges to using polymers in multi-layer eyepieces for head mounted displays. For example, a polymer layer may have a coefficient of thermal expansion (CTE) that is approximately 10 times greater than glass. In other words, when a polymer layer undergoes a temperature change, the polymer layer may expand (or contract) up to 10 times more than glass. Furthermore, the CTE of a polymer is not consistent compared to the CTE of glass. In other words, there may be a greater variation in CTE between different batches of the same type of polymer when compared to different batches of glass. Thus, layers formed from the same batch of polymer may undergo different amounts of expansion and contraction due to temperature changes.

[0079] In practice, the relatively large and variable CTE of polymers can make it difficult to manufacture a polymer eyepiece that can provide consistent, high-quality digital images and remain robust. For example, a head mounted display may heat up with use of the device and heat generation from electronic components. Thus, the relatively large CTE of a polymer (e.g., compared to glass and metal) can introduce challenges when mounting an eyepiece, e.g., eyepiece 500, to a material with a lower CTE. In some embodiments, the eyepiece may be attached to the head mounted display via a frame. In some embodiments, the entire periphery of the eyepiece may be attached to the frame. The frame may be formed from a rigid material, such as a metal, e.g., magnesium, that has a relatively low CTE compared to the polymer. This difference in CTE between metal and polymer may cause a polymer eyepiece to expand more than a metal frame when the head mounted display undergoes temperature changes. The relative expansion of the polymer eyepiece with respect to the metal frame may result in deformation of the eyepiece that may reduce the performance and quality of the digital image presented to the user.

[0080] Additionally, variable CTE of a polymer, for example between batches of polymer, can make it difficult to maintain the quality of the digital image presented to the user. For example, the quality of a digital image can depend on maintaining a consistent distance or gap between layers and alignment of the layers in the stack, e.g., top-down. Variations in CTE between layers can affect the gap and alignment of the layers. For example, as the eyepiece heats up, differences in CTE can cause some layers to expand (longitudinally and widthwise) more than others. Expansion in the longitudinal direction, e.g., in-plane, can affect the alignment of the layers, particularly the alignment of the light entrance region 701 and the light exit region 705, while expansion in the width direction, e.g., out-of-plane, can affect the gap size.

[0081] Eyepieces according to the present disclosure may provide for athermalization of the fit between the eyepiece, e.g., eyepieces 500 and / or 600, and the frame, as well as between layers of the eyepiece. As used in this disclosure, athermalization may refer to a process and / or structure used to improve the optical stability (e.g., the quality of the displayed image) of the eyepiece and / or display with temperature fluctuations. Athermalized eyepieces may reduce the effects of the relatively large and variable CTE of polymers in eyepieces used in head mounted displays. Exemplary Athermalized Mounting

[0082] As discussed above, a polymer eyepiece mounted on a metal frame without utilizing athermalization techniques may experience performance degradation as the head mounted display undergoes changes in operating temperature and load. For example, a head mounted display may include one or more polymer eyepieces, such as eyepiece 500, mounted on a metal frame. Mounting the eyepiece on the frame may help secure the eyepiece to the head mounted display and align the eyepiece with other components of the optical system, such as a light source, to deliver digital images to the user. During operation, a head mounted display including a polymer eyepiece may generate heat. As a result, the polymer eyepiece may undergo in-plane expansion in all directions, such as the x and y directions, as well as out-of-plane expansion in the z direction. The amount of expansion may correspond to the full span of the polymer material in a given direction. Thus, the eyepiece may expand most in-plane where there is a longer span of the polymer material, and least in the z direction.

[0083] As described above, the periphery of the eyepiece may be attached to the metal frame of the head mounted display via adhesive. Due to the difference in CTE between metal and polymer and the dimensions of the components, when the head mounted display undergoes temperature changes, the polymer eyepiece may expand more than the metal frame. As a result, the polymer eyepiece may be constrained by the adhesive. The constraints imposed by attaching the polymer eyepiece to the metal frame may result in deformation of the eyepiece, reducing the performance and quality of the digital image presented to the user. For example, deformation may cause misalignment between layers of the eyepiece and / or between the eyepiece and the light source, affecting the consistency of the gap.

[0084] A mounting scheme for promoting athermalization between a frame and a polymer eyepiece according to embodiments of the present disclosure can hold the eyepiece securely in place while allowing the polymer eyepiece to expand and / or contract relative to the metal frame without degrading the quality of the output digital image. Embodiments according to the present disclosure can provide a polymer eyepiece, such as eyepiece 500, attached to a metal frame using one or more adhesives along the periphery of the polymer eyepiece. The one or more adhesives and / or the frame can secure the polymer eyepiece, such as eyepiece 500, to the frame while allowing the eyepiece to expand and / or contract.

[0085] FIG. 8 illustrates an optical system for a mixed reality system including an eyepiece 800 mounted in a frame 830 according to an embodiment of the present disclosure. As shown, the eyepiece 800, e.g., a polymer eyepiece, may be disposed in a metal frame 830. The polymer eyepiece 800 may be coupled to the frame 830 using at least two sets of couplings. The first set of couplings 831 may be formed from an adhesive having a first stiffness, and the second set of couplings may be formed from an adhesive having a second relatively soft stiffness compared to the first set of adhesive. For example, if the first set of couplings has a stiffness of about 1000 MPa, the second set of couplings may have a stiffness of about 100 MPa. The adhesives may include, for example, Dymax (E=730 MPa) and Epotek (E=2300 MPa). In some embodiments, the stiffness of the adhesives may be tuned to achieve a desired performance.

[0086] In some embodiments, the first set of couplings 831 may be located near the light entrance region 801 of the eyepiece 800. For example, the first set of couplings 831 may include at least two coupling segments located on either side of the light entrance region 801 along the circumference of the eyepiece 800. The coupling segments may be relatively short in length compared to the size of the eyepiece 800 and the light entrance region 801. For example, the coupling segments may be less than half the length of the light entrance region. In some embodiments, the coupling segments are shown as the same length, but the coupling segments may have different lengths. The first set of couplings 831 may be formed from a relatively rigid or hard adhesive. Positioning the first set of couplings 831 with relatively rigid couplings near the light entrance region 801 may constrain the eyepiece near the light entrance region 801. In this manner, the first set of couplings may be used to maintain alignment of the light entrance region 801 with a light source (not shown) during temperature fluctuations of the head mounted display. Maintaining alignment between the light source and the light entrance area can ensure that the eyepiece 800 can properly in-couple light from the light source into the eyepiece 800.

[0087] The second set of couplings 833 may include at least two coupling segments located near the light exit region 805 along the circumference of the eyepiece. The coupling segments may be relatively short in length compared to the size of the eyepiece 800 and the light exit region 805. In some embodiments, the coupling segments of the second set of couplings 833 may be the same length as the first set of couplings 831 (but are not limited to this). The second set of couplings 833 may be located on either side of the eyepiece 800 and / or the light exit region 805, near the area where the incoming light, e.g., light 703, is projected across the eyepiece 800. In some embodiments, the second set of soft couplings may include a single soft coupling. In some embodiments, the eyepiece 800 can be attached to the frame 830 without the second set of couplings, i.e., the eyepiece is attached to the frame using the first set of couplings 831.

[0088] The second set of couplings 833 may be formed from a relatively compliant or soft adhesive as compared to the first set of couplings 831. For example, the second set of couplings 833 may allow movement of the eyepiece 800 due to in-plane expansion and / or contraction. In comparison, the first set of couplings 831 may limit movement of the eyepiece 800 due to in-plane expansion and / or contraction. The second set of couplings 833 may provide additional strength and stability to the eyepiece attachment while minimizing resistance between the eyepiece and the adhesive as the eyepiece expands and / or contracts in-plane.

[0089] FIG. 9 illustrates an optical system including an eyepiece 900 mounted within a frame 930 according to an embodiment of the present disclosure. As illustrated, the eyepiece 900, e.g., a polymeric eyepiece, may be disposed within a metal frame 930. The polymeric eyepiece 900 may be bonded to the frame 930 using at least two types of bonds, where a first set of hard bonds 931 may be formed from an adhesive having a first stiffness, and a second set of soft bonds 933 may be formed from an adhesive having a second relatively soft stiffness compared to the first set of hard bonds 931. The hard bonds 931 may be disposed near the light entrance region 901. Compared to the first set of bonds 831 illustrated in FIG. 8, the hard bonds 931 may be disposed along a longer length of the circumference of the eyepiece 900 near the light entrance region 901. For example, the hard bonds 931 may form an arc along the circumference of the eyepiece 900. This additional length of adhesive may provide greater bond strength between eyepiece 800 and frame 930 as compared to the mounting configuration of eyepiece 900. Soft bonds 933 may be similar to the second set of bonds 833 described above.

[0090] 8 and 9 are shown with particular configurations of the first set of couplings and the second set of couplings, one of ordinary skill in the art will understand that multiple configurations of the first set of couplings and the second set of couplings can be implemented without departing from the scope of the present disclosure. For example, in some embodiments, the first set of hard couplings may be located at different positions along the circumference of the eyepiece based on, for example, the shape and / or location of the light entry and exit regions.

[0091] FIG. 10 illustrates an exemplary eyepiece 1000 for a mixed reality system mounted on a frame 1030 according to an embodiment of the present disclosure. As shown, the frame may include one or more lips 1035a, 1035b configured to engage with the eyepiece 1000 to prevent out-of-plane deformation and potential damage. The eyepiece 1000 may include one or more layers 1010. The one or more layers may include an active layer and / or a cover layer. The frame 1030 may include a primary frame member 1031 having a lip 1035b. The frame 1030 may also include a cap 1033 having a lip 1035a. The cap 1033 may be disposed on the primary frame member 1031 to form a gap between the lip 1035a and the lip 1035b. As shown in FIG. 10, the lip 1035a may be an upper lip and the lip 1035b may be a lower lip. Those skilled in the art will appreciate that the upper / lower designation is not intended to limit the scope of the present disclosure.

[0092] The eyepiece 1000 may be positioned within the frame 1030 such that the upper lip 1035a may contact the top surface 1021 of the eyepiece 1000. The lower lip 1035b may contact the bottom surface 1022 of the eyepiece 1000. In this manner, the upper lip 1035a and the lower lip 1035b may secure the eyepiece 1000 with light contact between the eyepiece 1000 and the lips 1035a, 1035b. This light contact may allow the eyepiece 1000 to expand within the frame without deforming. In other words, a gap formed between the upper lip 1035a and the lower lip 1035b may be permitted to bound the periphery of the eyepiece 1000 and hold the eyepiece 1000 within the frame 1030 while still allowing the eyepiece to expand and contract with temperature changes.

[0093] In some embodiments, the frame including the frame member 1031 and the cap 1033 may be used with the adhesive bond described above in connection with FIGS. 8 and 9. In some embodiments, the lip 1035a, 1035b may be angled slightly relative to the eyepiece 1000 such that the gap between the lip and the eyepiece (e.g., the lip 1035a and the top surface 1021 of the eyepiece 1000) is smaller at the distal end of the lip. In some embodiments, the cap 1033 may be positioned along the entire circumference of the frame member 1031. In some embodiments, the cap 1039 may be intermittently positioned along segments of the circumference of the frame member 1031. For example, the cap locations may be located in areas without adhesive bonds (e.g., the first bonded segment 831 and the second bonded segment 833).

[0094] FIG. 11 illustrates an exemplary eyepiece 1100 for a mixed reality device mounted on a frame 1130, according to an embodiment of the present disclosure. As shown, the frame 1130 can include one or more lips 1135 configured to engage the eyepiece 1000 to prevent out-of-plane deformation as described with respect to the eyepiece 1100. For example, the frame 1130 can include a primary frame member 1131 and a cap 1133, as described above with respect to the frame 1030. The frame 1130 can further include a layer of foam 1139 disposed on a lower surface of the cap 1133. The layer of foam 1139 can be positioned such that it lightly contacts the upper surface 1121 of the eyepiece 1100 when the eyepiece 1100 is disposed within the frame 1130, i.e., within the gap between the upper lip 1135a and the lower lip 1135b. As the eyepiece 1100 expands and contracts within the frame, the eyepiece 1100 can compress the foam 1039. In this manner, the foam 1139 may allow for expansion of the eyepiece with minimal resistance, yet exert a contact force on the eyepiece 1100 to hold it in place when there is no expansion. Compared to the frame 1030, the frame 1130 may allow for a wider range of tolerances in the cap 1133 and frame member 1131 due to the presence of the layer of foam 1139.

[0095] FIG. 12 illustrates an exemplary eyepiece 1200 attached to a frame 1230 according to an embodiment of the present disclosure. As shown, the eyepiece 1200 may include two glass cover layers 1220 that may sandwich one or more polymer active layers 1210. This eyepiece configuration is described in more detail in the Layer-by-Layer Athermalization section. Due to differences in CTE between glass and polymer, the active layer 1210 and the glass cover layer 1220 may be separately attached to the frame 1230. This may allow the polymer layer 1210 to expand and contract at a different rate than the glass cover layer 1220 without affecting the bond between the frame 1230 and the cover layer 1220. For example, the glass cover layer 1220 may be attached to the frame 1230 using a bond 1235, and the polymer active layer 1210 may be attached to the frame 1230 using a bond 1237.

[0096] As shown, the polymer active layers 1210 may be attached to the frame 1230, for example together as a unit, and bonds 1237 may be used to attach one or more active layers 1210. The active layers 1210 may be attached to the frame as described in Figures 8 and 9. For example, the active layers 1210 may be attached to the frame 1230 using at least one set of hard bonds, for example, hard bonds 831. In some embodiments, the active layers 1210 may be attached using one set of hard bonds and one set of soft bonds, for example, soft bonds 833.

[0097] The glass cover layer 1220 may be attached to the frame 1230 using bonds 1235. As shown, the cover layer 1220 may be separately attached to either side of the active layer 1210. In some embodiments, one or more of the entire perimeters of the glass cover layer 1220 may be bonded to the frame 1230. In other words, the bonds 1235 may be disposed continuously along the perimeter of the glass cover layer 1220. In some embodiments, the bonds 1235 may be disposed along portions of the perimeter of the glass cover layer 1220 such that the bonds 1235 span separate segments of the perimeter.

[0098] While the above examples are described with respect to specific figures, one of ordinary skill in the art will appreciate that an eyepiece-to-frame mounting scheme according to an embodiment of the present disclosure may include embodiments from one or more of the above figures. For example, an optical system having a mounting scheme as described in connection with Figures 8 and 9 may also include a frame having a cap, e.g., cap 1033, cap 1133, to inhibit out-of-plane movement of the eyepiece, for example, when at least one set of hard bonds 831 are used to mount eyepiece 800 to frame 830. Exemplary Interlayer Athermalization

[0099] As discussed above, variable CTE of a polymer, for example between batches of polymer, can make it difficult to maintain the quality of the digital image presented to the user. Negative performance due to normal variations in CTE can be attributed to the bimetallic phenomenon. As used herein, bimetallic phenomenon may refer to material deformation that occurs when two or more materials with different CTEs are attached or bonded together and undergo temperature changes together. Figures 13A-13C show an example of the bimetallic phenomenon. As shown in Figure 13A, component 1300A includes two layers, each layer formed from a different material with a different CTE. For example, layer 1350 may be formed from brass and layer 1355 may be formed from steel. As shown in the figure, when the component is at a reference temperature, the first and second layers may be flat. As used herein, reference temperature may refer to a temperature at which both materials are not deformed.

[0100] FIG. 13B shows component 1300B when heat is applied. The difference in CTE between the two layers can cause one material to expand more than the other, resulting in a displacement or curvature of the component. As can be seen, brass 1350 can expand more than steel 1355, resulting in a convex curvature of component 1300. FIG. 13C shows component 1300B when cooled (relative to a reference temperature). As can be seen, steel 1355 can expand more than brass 1350, resulting in a concave curvature of component 1300C.

[0101] The bimetallic phenomenon can be applied to polymer lenses where differences in CTE can cause the layers of the eyepiece to expand at different rates and separate, adversely affecting the performance of the eyepiece. For example, eyepiece performance and quality of digital images can depend on maintaining a consistent distance or gap between layers and alignment of the layers in a stack, e.g., top-down. Variations in CTE between layers can affect the gap and alignment of the layers.

[0102] For example, different batches of polymers may have a variation in CTE of ±5 ppm. The variation in CTE may result in a degradation of eyepiece performance. FIG. 14 shows a chart 1400 demonstrating the effect of CTE variation on performance degradation, which corresponds to surface normal RMS rotation. Acceptable performance may correspond to a surface normal root mean square (RMS) rotation of 1 arcmin or less. As shown, the surface normal RMS rotation increases with increasing CTE, and a variation of ±1 ppm may correspond to an increase of about 1 arcmin or more. Thus, normal variation in CTE between polymer batches may adversely affect the performance of the eyepiece and the quality of the images produced. Embodiments according to the present disclosure may provide an eyepiece that is less susceptible to bimetallic phenomena.

[0103] FIG. 15 illustrates an exemplary eyepiece 1500 according to an embodiment of the present disclosure. The eyepiece 1500 may include two glass cover layers 1520 sandwiching one or more polymer active layers 1510. As shown, the two glass cover layers 1520 may be substantially flat, and the polymer layer 1510 may include flat regions 1562 (e.g., corresponding to regions where the active layer 1510 is substantially flat) and spherical regions 1564 (e.g., corresponding to regions where the active layer is curved). As discussed above, multiple pillars may be disposed between the various layers to maintain consistent spacing between each layer. For example, the eyepiece 1500 may include multiple variable height pillars 1566 disposed between the glass cover layer 1520 and the polymer active layer 1510. In this manner, the variable height pillars 1566 may maintain spacing between the flat glass cover layer 1520 and the polymer active layer 1510. The eyepiece 1500 may further include a plurality of uniform height pillars 1568 disposed between the polymer active layers 1510. The uniform height pillars 1568 may be provided to maintain a consistent gap between the polymer active layers. In some embodiments, the plurality of variable height pillars 1566 and the plurality of uniform height pillars 1568 may be integrally formed with adjacent polymer active layers. Although the eyepiece 1500 is shown with aligned variable height pillars 1566 and uniform height pillars 1568, in some embodiments, the variable height pillars 1566 and uniform height pillars 1568 may not be aligned.

[0104] FIG. 16 illustrates a detailed view of an eyepiece 1600 for a mixed reality system according to an embodiment of the present disclosure. As shown, the eyepiece 1600 may include one or more layers and a number of spacers, e.g., pillars. For example, the eyepiece 1600 may include a glass cover layer 1620 that sandwiches one or more polymer active layers 1610. The variable height pillars 1666 may span the distance between the flat glass layer 1620 and the polymer layer 1610. In some embodiments, the polymer layer 1610 may include a flat region 1662 and a bulbous region 1664. In some embodiments, the variable height pillars 1666 may be configured to slide along the glass layer 1620 as the adjacent polymer layer 1610 expands. In some embodiments, the variable height pillars 1666 may be integrally formed with the adjacent polymer layer 1610, such that the variable height pillars 1666 may move and / or slide along the glass cover layer 1620 based on the expansion of the polymer layer 1610. Due to the difference in CTE between glass and polymer, the glass layer 1620 can be attached to a frame 1630 separately from the polymer active layer 1610 as described with respect to FIG.

[0105] Forming an eyepiece, e.g., eyepiece 1500 and / or 1600, with one or more glass cover layers instead of a polymer cover layer may take advantage of the relative stiffness of glass compared to polymer to maintain the shape of the active layer as the eyepiece heats up. For example, because of the relatively low CTE of glass, the glass cover layer may retain its shape as the display heats up and / or maintain shape consistently across the operating temperature of the head mounted display. Additionally, because the polymer layer 1610 is sandwiched between the relatively stiff glass cover layers 1620, deformation and / or separation of the polymer active layer 1610 may be limited. That is, the glass cover layers 1620 may be able to resist deformation of the polymer layer 1610 located therein. Additionally, the glass cover layers 1620 may be relatively cost-effective as they do not require expensive manufacturing steps associated with forming a glass active layer. Additionally, a durable surface finish may be achieved on the glass cover layers compared to the glass active layers to provide a more robust eyepiece. Surface finishes may include, but are not limited to, Gorilla Glass. In some examples, embodiments of eyepieces 1500 and / or 1600 may improve performance by up to 90% over non-athermalized eyepieces.

[0106] FIG. 17 illustrates an eyepiece 1700 according to an embodiment of the present disclosure. As shown, the eyepiece may include multiple layers, including one or more cover layers 1722, 1724 and one or more active layers 1710. Example embodiments may utilize the bimetallic phenomenon to "tune" the top and bottom cover layers so that the eyepiece may be deformed as a unit. In other words, the top cover layer 1722 may be preselected to have a relatively high CTE compared to the CTE of the active layer 1710, and the bottom cover layer 1724 may be preselected to have a relatively low CTE. For example, if the active layer 1710 has a CTE variation of ±5 ppm, the cover layers may vary by ±10 ppm or ±20 ppm. In this way, the behavior of the cover layers of the eyepiece is known, and as the eyepiece temperature increases, the top cover layer 1722 may expand, while the bottom cover layer 1724 may contract when the eyepiece 1700 is heated, similar to component 1300B. That is, the eyepiece 1700 may deform into a curved shape above its reference temperature. As the temperature of the eyepiece 1700 increases, each of the active layers 1710 may also expand based on their respective CTEs, but the overall shape of the active layers may adjust to fit a shape determined by the CTEs of the cover layers 1722, 1724.

[0107] FIG. 18 illustrates an eyepiece 1800 for a mixed reality device according to an embodiment of the present disclosure. The figure illustrates the eyepiece 1800 before assembly. The pre-assembled eyepiece 1800 may include one or more substantially flat glass cover layers 1820 sandwiching one or more substantially flat polymer active layers 1810. The eyepiece 1800 may further include a plurality of variable height pillars 1866 disposed between the glass cover layer 1820 and adjacent polymer layers 1810. In some embodiments, a plurality of uniform height pillars (not shown) may be disposed between adjacent polymer layers 1810, as described above with respect to the eyepiece 1500. The eyepiece 1800 may be configured to have a flat shape prior to assembly and a second, different shape after assembly. In some embodiments, one or more active layers may be deformed during assembly.

[0108] FIG. 19 illustrates an assembled eyepiece 1800 that may correspond to eyepiece 1900 after assembly. As seen in the figure, assembled eyepiece 1900 may include flat region 1962 and spherical region 1964. In some embodiments, variable height pillar 1966 may be sized such that when the eyepiece is assembled, variable height pillar 1966 may engage glass cover layer 1920 such that the assembled shape of polymer active layer 1920 includes flat portion 1962 and spherical portion 1964. In other words, the process of assembling eyepiece 1800 may deform a substantially flat polymer active layer to arrive at an eyepiece shape illustrated by eyepiece 1900 that includes flat and spherical portions. The shape of eyepiece 1900 may be exaggerated to illustrate the flat and spherical portions, i.e., the deflection of the spherical portion may not be significant in practice, but one skilled in the art will understand that eyepieces according to embodiments of the present disclosure may include flat and spherical portions. In some embodiments, the configuration of the assembled eyepiece 1900 may be similar to eyepieces 1200, 1500, and 1600.

[0109] In this manner, the assembled eyepiece 1900 may have advantages associated with eyepieces 1500 and 1600, i.e., for example, one or more glass cover layers may help maintain the shape of the active layer 1910 as the eyepiece expands with increasing temperature. For example, because the CTE of glass is relatively low, the glass cover layers may retain their shape as the display heats up and / or maintain their shape consistently over the operating temperature of the head mounted display. Additionally, because the polymer layer 1910 is sandwiched between relatively rigid glass cover layers 1920, deformation and separation of the polymer layer 1910 may be limited.

[0110] Additionally, deforming the active layer 1910 during assembly of the eyepiece 1900 to form a desired shape, for example having flat regions 1962 and spherical regions 1964, may pretension the polymer active layer 1910. A pretensioned polymer active layer 1910 may be less likely to separate due to thermal expansion, for example, when the polymer active layer is molded to include flat regions 1962 and spherical regions 1964, compared to a stack of polymer active layers that is not pretensioned. Additionally, because the preassembled stack of active layers 1810 is flat, the manufacturing process for the active layer 1810 may be simplified. For example, the active layer 1810 may be manufactured as a flat layer and rely on variable height pillars to pretension the eyepiece to a desired shape during assembly. In comparison, the active layers 1510 and / or 1610 may be manufactured to include flat regions and spherical regions, which may add complexity to the manufacturing process.

[0111] FIG. 20 illustrates a perspective view of an eyepiece 2000 according to an embodiment of the present disclosure. As shown, the eyepiece may include multiple layers, including one or more cover layers 2020 and one or more active layers 2010. The active layers 2010 and cover layers 2020 may be configured to slide relative to one another. For example, as described above, edge spacers 2009 may be disposed between the outer periphery of each layer of the eyepiece. In some embodiments, the edge spacer may be bonded to one of the eyepieces. Bonding an edge spacer to one, but not both, adjacent eyepiece layers may allow the eyepiece layers to move and / or slide relative to one another. In contrast, as described above with respect to eyepiece 600, edge spacer 609 may be sandwiched and bonded by both adjacent eyepiece layers to prevent the eyepiece layers from sliding relative to one another. For example, edge spacer 2009a may be disposed between the lower cover layer 2020 and the active layer 2010. As shown, edge spacers 2009 a may be bonded to the lower cover layer 2020 such that the active layer 2010 can slide relative to the upper cover layer 2020 .

[0112] Allowing the eyepiece layers to slide relative to one another may reduce separation of the eyepiece layers caused by bimetallic phenomena. In other words, the eyepiece layers may not undergo deformations associated with bimetallic phenomena because they are allowed to slide relative to one another. Thus, eyepieces according to embodiments of the present disclosure that include layers that are allowed to slide relative to one another may improve eyepiece performance from, for example, a baseline design that does not consider thermal expansion effects.

[0113] In some embodiments, relative sliding of the eyepiece layers may affect optical alignment between the layers. For example, relative sliding of the eyepiece layers may cause misalignment between the light input region and the light source and / or between the light input region and the light output region of the layers in the eyepiece. Some embodiments according to the present disclosure may provide an eyepiece having a sliding layer that can maintain acceptable optical alignment between each of the layers during use. In one or more examples, the acceptable optical alignment can be predetermined based on specific design considerations associated with the eyepiece. Additionally, some embodiments according to the present disclosure may provide an eyepiece including a sliding layer that may be assembled as a unit and that can resist damage and out-of-plane deformation and / or movement when the head mounted display experiences a dynamic event, such as being dropped.

[0114] FIG. 21 illustrates an eyepiece 2100 according to an embodiment of the present disclosure. As shown, the eyepiece 2100 may include one or more eyepiece layers 2110 attached to a frame 2130. The frame 2130 may include one or more stages 2172a-c, with each stage corresponding to an eyepiece layer 2110. In some embodiments, each of the eyepiece layers 2110 may be a different size corresponding to the outer perimeter of the frame in each of the stages 2172. For example, as seen in the figure, the upper stage 2172a of the frame may have a larger outer perimeter than the lower stage 2172c of the frame. Thus, the upper eyepiece layer 2110 may be larger than the lower eyepiece layer 2110 to accommodate the larger outer perimeter of the upper stage 2172a.

[0115] One or more of the eyepiece layers 2110 may be configured to slide relative to one another, as described above with respect to the eyepiece 2000. For example, each eyepiece layer 2110 may be coupled to a respective step 2172 by a coupling 2137. The eyepiece layers 2110 may not be coupled to one another. In this manner, the eyepiece layers 2110 may be allowed to slide relative to one another as the temperature of the eyepiece 2100 changes. In some embodiments, the couplings 2137 may be located along separate portions of the eyepiece layers 2110. In other words, the couplings 2137 may not be located around the entire circumference of the eyepiece layers 2110 and the frame 2130. In some embodiments, the configuration of the couplings 2137 may correspond to the configuration of the couplings 831 and 833 described with respect to the eyepiece 800. That is, at least one set of couplings may be located near the light entrance region of the eyepiece. The bond 2137 between the eyepiece layer 2110 and the frame 2130 can help the eyepieces maintain optical alignment as the layers 2110 slide relative to one another. Additionally, because each eyepiece layer 2110 is bonded to the frame 2130, the eyepieces can be resistant to damage if the head mounted display is dropped or subjected to dynamic forces.

[0116] In some embodiments, the step 2172 may be manufactured to provide a consistent gap between each of the eyepiece layers 2110. The gap may be sized to allow for expansion of each of the eyepiece layers 2110 while maintaining a consistent gap 2107 between the layers. In some embodiments, multiple spacers may further be included to maintain the gap between the layers (e.g., spacers 609, 611).

[0117] 22 illustrates an eyepiece 2200 according to an embodiment of the present disclosure. As can be seen, the eyepiece 2200 can include multiple eyepiece layers 2210 with one or more rollers 2274 disposed between each of the multiple eyepiece layers 2210. In some embodiments, the rollers 2274 can be disposed about the periphery of the eyepiece 2210. The rollers can facilitate relative sliding between the eyepiece layers 2210. The eyepiece layers 2210 can include an active layer and / or a cover layer.

[0118] In some embodiments, one or more of the eyepiece layers 2210 may be formed to include slots 2276 configured to receive the rollers 2274. The slots 2276 may prevent the rollers 2274 from moving from a desired location, such as near the outer periphery of the eyepiece, which may adversely affect the performance and stability of the eyepiece 2210. In some embodiments, the slots 2276 may be molded as a feature of the eyepiece layer 2210. The ability to mold unique shapes is one of the advantages of polymer layers compared to glass layers. For example, the rollers 2274a may be positioned within slots 2276a molded into the top surface of the eyepiece layer 2210a. In this way, the rollers 2274a may be restricted to the slots 2276a while allowing relative sliding of the upper eyepiece layer 2210b over time. In addition to allowing sliding between the layers, the rollers 2274 may act as spacers and help maintain consistent spacing between the eyepiece layers 2210. The rollers 2274 may be made from a variety of materials, such as glass beads. In some embodiments, the rollers may be formed from a material that has a relatively low CTE.

[0119] FIG. 23 illustrates an optical system including an eyepiece 2300 and a frame 2330 according to an embodiment of the present disclosure. The eyepiece 2300 may be similar to the eyepiece 2200. That is, the eyepiece may include a plurality of eyepiece layers 2310, one or more of which include a plurality of slots 2276. As shown, rollers 2374 may be disposed within corresponding slots 2376 to facilitate relative sliding between the plurality of eyepiece layers 2310. Furthermore, the optical system may include a frame 2330 including a cap 2335. The cap 2335 may be provided to prevent deflection in an out-of-plane direction perpendicular to the surface of the eyepiece 2300. In this manner, the optical system including the eyepiece 2300 and the frame 2330 may be more robust by including the cap 2335, as the optical system may withstand the daily loads on the head mounted display resulting from daily use. The configuration of the cap 2335 may be similar to the lips 1035 and 1135. In some embodiments, the cap 2335 may include a layer of foam (not shown) similar to the layer of foam 1139 included in the frame 1130 .

[0120] FIG. 24 illustrates an eyepiece 2400 according to an embodiment of the present disclosure. The eyepiece 2400 may include one or more edge spacers 2409a, 2409b that may be integrally formed with a corresponding eyepiece layer. In this manner, an edge spacer, e.g., edge spacer 2409a, may be integrally formed with a corresponding eyepiece layer, e.g., eyepiece layer 2410a, and may move with the corresponding eyepiece layer. In some embodiments, a layer of lubricant or other material that reduces friction may be applied between the edge spacer 2409 and an adjacent unbonded and / or unintegrated eyepiece layer. For example, in some embodiments, a layer of lubricant may be applied between the edge spacer 2409a and the adjacent eyepiece layer 2410b. In this manner, the lubricant may promote sliding between the eyepiece layers.

[0121] FIG. 25 illustrates an eyepiece 2500 according to an embodiment of the present disclosure. As shown, the eyepiece 2500 can include one or more eyepiece layers 2510 and one or more edge spacers 2509a, 2509b disposed between each of the one or more eyepiece layers 2510. In some embodiments, the edge spacers 2509s, 2509a, 2509b can be formed separately and from a different material than the eyepiece layers. The edge spacers 2509a, 2509b can be bonded to one of the adjacent eyepiece layers. For example, as shown, the edge spacer 2509a can be bonded to the adjacent eyepiece layer 2510a. This can allow the edge spacers 2509a, 2510a to slide relative to the eyepiece layer 2510b. In some embodiments, the edge spacer material may be selected to have a low coefficient of friction to promote sliding between an edge spacer, e.g., edge spacer 2509a, and an adjacent unbonded eyepiece layer, e.g., eyepiece layer 2510b.

[0122] In some embodiments, the eyepiece, for example the eyepieces shown in Figures 15-25, may be assembled at or near the steady state operating temperature of the head mounted display. The above embodiments are generally described under the assumption that the eyepiece is assembled and / or manufactured at a reference temperature that corresponds to the temperature of the eyepiece when the head mounted display is not in use. As the head mounted display is used, the temperature of the display and / or eyepiece may increase as the electronic components heat up. The head mounted display and eyepiece may eventually reach a "steady state" operating temperature at which the head mounted display no longer increases in temperature. Assembling the eyepiece at room temperature may result in an eyepiece that provides peak performance and / or digital image quality at room temperature. As the head mounted display and eyepiece heat up and reach the steady state operating temperature, the image quality of the optical system may be adversely affected. Assembling the eyepiece at or near the steady state operating temperature may provide optimal image quality and performance when the head mounted display is at the steady state operating temperature. This embodiment may result in improved optical performance of the head mounted display as it heats up, such that the head mounted display has peak performance at the steady state temperature. As a result, the image quality during start-up of the device may be inferior to the image quality when the device is operating at steady state temperature.

[0123] Embodiments of the present disclosure provide systems and methods for displays. In some embodiments, the display system includes a frame, an eyepiece coupled to the frame, and a first adhesive bond disposed between the frame and the eyepiece. The eyepiece can include a light entry region and a light exit region. The first adhesive bond can be disposed along a first portion of a circumference of the eyepiece, the first portion of the circumference of the eyepiece abutting the light entry region such that the first adhesive bond is configured to maintain a position of the light entry region relative to the frame.

[0124] In some embodiments, the display may further include a second adhesive bond disposed between the frame and the eyepiece, the second adhesive bond disposed along a second portion of the circumference of the eyepiece, the second portion of the circumference of the eyepiece abutting the light exit region, the second of the adhesive bonds configured to allow lateral expansion of the eyepiece relative to the frame. In some embodiments, the display may include a first adhesive bond associated with a first modulus of elasticity, the second adhesive bond associated with a second modulus of elasticity, the first modulus of elasticity being greater than the second modulus of elasticity. In some embodiments, the display may further include a third adhesive bond, the third adhesive bond associated with a first modulus of elasticity, the first and third adhesive bonds disposed on opposite sides of the light entrance region. In some embodiments, the length of the first adhesive bond may be less than half the length of the light entrance region. In some embodiments, the first adhesive bond may include an arcuate bond disposed proximate to the periphery of the light entrance region.

[0125] An embodiment of the present disclosure provides a system and method for an eyepiece for a display. In some embodiments, the eyepiece may include a first eyepiece layer, a second eyepiece layer disposed substantially parallel to the first eyepiece layer, and one or more edge spacers disposed between the first eyepiece layer and the second eyepiece layer. The one or more edge spacers may be configured to maintain a consistent gap between the first eyepiece layer and the second eyepiece layer and allow relative sliding between the first eyepiece layer and the second eyepiece layer. In some embodiments, the one or more edge spacers of the eyepiece may be bonded to the first eyepiece layer. In some embodiments, the eyepiece may further include a layer of lubricant disposed between the one or more edge spacers and the second eyepiece layer. In some embodiments, the one or more edge spacers are integrally formed with the first eyepiece layer.

[0126] In some embodiments, the first eyepiece layer can be made of a first material and the one or more edge spacers can be made of a second material different from the first material, where the second material can have a lower coefficient of friction with respect to the first material. In some embodiments, the first surface of the first eyepiece layer comprises a slot, where a corresponding edge spacer of the one or more edge spacers is disposed within the slot. In some embodiments, the eyepiece may further include a plurality of pillar spacers disposed between the first eyepiece layer and the second eyepiece layer, where the plurality of pillar spacers are configured to maintain consistent spacing between the first eyepiece layer and the second eyepiece layer.

[0127] The embodiments of the present disclosure provide a system and method for a display. In some embodiments, the display can include a frame and an eyepiece coupled to the frame. The eyepiece can include a first eyepiece layer, a second eyepiece layer disposed substantially parallel to the first eyepiece layer, and one or more edge spacers disposed between the first eyepiece layer and the second eyepiece layer. The one or more edge spacers can be configured to maintain a consistent gap between the first eyepiece layer and the second eyepiece layer and allow relative sliding between the first eyepiece layer and the second eyepiece layer. In some embodiments, the display of the frame of the display can include a cap disposed along an outer periphery of the frame. In some embodiments, the frame includes a first step corresponding to the first outer periphery and a second step corresponding to the second outer periphery. The first eyepiece layer is disposed on the first step along the first outer periphery and the second eyepiece layer is disposed on the second step along the second outer periphery. In some embodiments, the one or more edge spacers can be integrally formed with the first eyepiece layer. In some embodiments, the display may further include a layer of lubricant disposed between the one or more edge spacers and the second eyepiece layer. In some embodiments, the first surface of the first eyepiece layer may include a slot, and a corresponding one of the one or more edge spacers may be disposed within the slot.

[0128] An embodiment of the present disclosure provides a system and method for a display. In some embodiments, the display can include a frame, the frame comprising a first step corresponding to a first perimeter and a second step corresponding to a second perimeter. The display can further include an eyepiece disposed within the frame. The eyepiece can include at least a first eyepiece layer and a second eyepiece layer disposed substantially parallel to the first eyepiece layer, the first eyepiece layer can be disposed in the first step along the first perimeter, and the second eyepiece layer can be disposed in the second step along the second perimeter.

[0129] Although the disclosed examples have been fully described with reference to the accompanying drawings, it should be noted that various modifications and changes will become apparent to those skilled in the art. For example, elements and / or components shown in the drawings may not be to scale and / or may be exaggerated for illustrative purposes. As another example, elements of one or more implementations may be combined, deleted, modified, or supplemented to form further implementations. For example, in some embodiments, an eyepiece according to an embodiment of the present disclosure may include an eyepiece combining features of eyepieces 2100 and 2200, and the eyepiece may be mounted on a frame including multiple stages (e.g., eyepiece 2100 mounted on frame 2130). The eyepiece may further include multiple rollers (e.g., roller 2276) disposed between the multiple layers to maintain spacing of the eyepiece layers and facilitate relative sliding of the eyepiece layers. In some embodiments, a cap, e.g., cap 2335, may be included along a portion of the frame to limit movement of the eyepiece layers in an out-of-plane direction. Other combinations and modifications should be understood to be within the scope of the disclosed examples as defined by the appended claims.

Claims

1. A display, A frame, an eyepiece coupled to the frame, the eyepiece comprising: A light entrance area; Light emission area and an eyepiece comprising: a first adhesive bond disposed between the frame and the eyepiece; Equipped with the frame comprises a first lip and a second lip separated from the first lip by a distance; the first adhesive bond is disposed along a first portion of a circumference of the eyepiece, the first portion of the circumference of the eyepiece contacting the light entry area such that the first adhesive bond is configured to maintain a position of the light entry area relative to the frame; each of the first lip and the second lip contacts a second portion of the periphery of the eyepiece; A display wherein the eyepiece is configured such that expansion of the second portion of the periphery of the eyepiece increases the distance separating the first lip from the second lip.

2. Each of the first lip and the second lip has a first lip portion and a second lip portion; the first lip portion contacts the second lip portion of the outer periphery of the eyepiece; The display of claim 1 , wherein a height of the first lip portion is greater than a height of the second lip portion along the direction of separation.

3. 3. The display of claim 1 or claim 2, further comprising a second adhesive bond disposed between the frame and the eyepiece, the second adhesive bond disposed along a third portion of the circumference of the eyepiece, the third portion of the circumference of the eyepiece abutting the light exit area, the second adhesive bond configured to allow in-plane expansion of the eyepiece relative to the frame.

4. 4. The display of claim 3, wherein the first adhesive bond is associated with a first modulus of elasticity and the second adhesive bond is associated with a second modulus of elasticity, the first modulus of elasticity being greater than the second modulus of elasticity.

5. 3. The display of claim 1 or claim 2, further comprising a third adhesive bond, the third adhesive bond being associated with a first elastic modulus, the first and third adhesive bonds being disposed on opposite sides of the light incidence region.

6. The display of claim 5 , wherein the length of the first adhesive bond is less than half the length of the light entrance area.

7. 3. The display of claim 1 or claim 2, wherein the first adhesive bond includes an arcuate bond located proximate to a periphery of the light entrance area.

8. An eyepiece, a first eyepiece layer; and a second eyepiece layer disposed substantially parallel to the first eyepiece layer; one or more edge spacers disposed between the first eyepiece layer and the second eyepiece layer; Equipped with The one or more edge spacers include: maintaining a consistent gap between the first eyepiece layer and the second eyepiece layer; and enabling relative sliding movement between the first eyepiece layer and the second eyepiece layer; The eyepiece is configured to:

9. The eyepiece of claim 8 , wherein the one or more edge spacers are bonded to the first eyepiece layer.

10. 10. The eyepiece of claim 9, further comprising a layer of lubricant disposed between the one or more edge spacers and the second eyepiece layer.

11. 10. The eyepiece of claim 9, wherein the one or more edge spacers are integrally formed with the first eyepiece layer.

12. the first eyepiece layer is made from a first material; the one or more edge spacers are made from a second material different from the first material; 10. The eyepiece of claim 9, wherein the second material has a lower coefficient of friction than the first material.

13. 9. The eyepiece of claim 8, wherein the first surface of the first eyepiece layer comprises a slot, and a corresponding edge spacer of the one or more edge spacers is disposed in the slot.

14. 9. The eyepiece of claim 8, further comprising a plurality of pillar spacers disposed between the first eyepiece layer and the second eyepiece layer, the plurality of pillar spacers configured to maintain consistent spacing between the first eyepiece layer and the second eyepiece layer.

15. A display, A frame, an eyepiece coupled to the frame, the eyepiece comprising: a first eyepiece layer; and a second eyepiece layer disposed substantially parallel to the first eyepiece layer; one or more edge spacers disposed between the first eyepiece layer and the second eyepiece layer; An eyepiece comprising: Equipped with The one or more edge spacers include: maintaining a consistent gap between the first eyepiece layer and the second eyepiece layer; and enabling relative sliding movement between the first eyepiece layer and the second eyepiece layer; A display configured to:

16. The display of claim 15 , wherein the frame comprises a cap disposed around a periphery of the frame.

17. The frame is a first step corresponding to the first periphery; a second step corresponding to the second outer periphery; Equipped with 16. The display of claim 15, wherein the first eyepiece layer is arranged in the first tier along the first perimeter and the second eyepiece layer is arranged in the second tier along the second perimeter.

18. 16. The display of claim 15, wherein the one or more edge spacers are integrally formed with the first eyepiece layer.

19. 20. The display of claim 18, further comprising a layer of lubricant disposed between the one or more edge spacers and the second eyepiece layer.

20. 16. The display of claim 15, wherein a first surface of the first eyepiece layer comprises a slot, and a corresponding edge spacer of the one or more edge spacers is disposed in the slot.

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