Compact extended depth of field lenses for wearable display devices

Abstract

A wearable display device includes waveguide(s) that present virtual image elements as an augmentation to the real-world environment. The display device includes a first extended depth of field (EDOF) refractive lens arranged between the waveguide(s) and the user's eye(s), and a second EDOF refractive lens located outward from the waveguide(s). The first EDOF lens has a (e.g., negative) optical power to alter the depth of the virtual image elements. The second EDOF lens has a substantially equal and opposite (e.g., positive) optical power to that of the first EDOF lens, such that the depth of real-world objects is not altered along with the depth of the virtual image elements. To reduce the weight and / or size of the device, one or both EDOF lenses is a compact lens, e.g., Fresnel lens or flattened periphery lens. The compact lens may be coated and / or embedded in another material to enhance its performance.

Description

COMPACT EXTENDED DEPTH OF FIELD LENSES FOR WEARABLE DISPLAYDEVICESBACKGROUNDField

[0001] This disclosure generally relates to optical devices and techniques for manufacturing optical devices. In particular, this disclosure relates to wearable optical devices that include extended depth of field lens(es), and techniques for manufacturing such devices.Description of the Related Art

[0002] Modem computing and display technologies have facilitated the development of virtual reality' (VR), augmented reality' (AR), and mixed reality' (MR) systems. VR systems create a simulated environment for a user to experience. This can be done by presenting computer-generated image data to the user through a wearable display device such as a head-mountable display (HMD) device. This image data creates a sensory experience which immerses the user in the simulated environment. A VR scenario typically involves presentation of computer-generated image data and does not also include actual real-world image data.

[0003] AR systems generally supplement a real-world environment with simulated, computer-generated elements. For example, AR systems may provide a user with a view of the surrounding real-world environment via a head-mounted display, while computergenerated image data is also presented on the display to enhance and / or augment the real- world environment. This computer-generated image data can include elements which are contextually related to the real-world environment. Such elements can include simulated text, images, objects, and so forth. An MR system is a type of AR system which also introduces simulated objects into a real -world environment, and these objects ty pically feature a greater degree of interactivity, e.g., interactivity between the simulated objects and elements of the real world. The simulated elements can be interactive in real time. In some examples of AR or MR systems, simulated elements can be presented such that theyappear to interact with physical objects in the real world. As used herein, AR generally refers to either AR or MR, or both AR and MR, unless specified otherwise.

[0004] FIG. 1 depicts an example AR scene 1 where a user sees a real-world park setting 6 featuring people, trees, buildings in the background, and a concrete platform 20. In addition to these items, computer-generated image data is also presented to the user. The computer-generated image data can include, for example, a robot statue 10 standing upon the real-world platform 20, and a cartoon-like avatar character 2 flying by which seems to be a personification of a bumblebee, even though these elements 2, 10 are not actually present in the real-world environment. The AR technology used to provide the AR scene 1 may allow the user to perceive the computer-generated (e.g., virtual) objects as if they were physically present in the real world, even though they are not actually physically present. Given the complexity of the human visual perception system, it is challenging to produce AR technology that facilitates a comfortable, natural-feeling, rich presentation of virtual image elements among other virtual elements and / or real-world objects.SUMMARY

[0005] The embodiments described herein address various challenges related to AR, VR, and / or MR technology . In some embodiments, a wearable AR display device includes one or more waveguides that convey light for virtual image elements (e.g., virtual objects) from a proj ection system that generates the light for the virtual image elements, to the ey e(s) of a user of the wearable AR display device. The waveguide(s) may convey the light by way of total internal reflection (TIR) until the light is redirected out from the waveguide(s) (e.g., out-coupled) and toward the user’s eye(s).

[0006] In some embodiments, the AR display device includes a first extended depth of field (EDOF) lens that is arranged between the waveguide(s) (or at least the out-coupling elements of the waveguide(s)) and the user’s eye(s) while the device is being worn. The first EDOF lens is configured to impart some optical power to the virtual image elements, to change a perceived depth of the virtual image elements so that they appear closer to the user’s eye(s) or farther from the user’s eye(s) than they would otherwise be perceived if the first EDOF lens was not present in the device. The AR display device also enables the user to perceive the real-world in front of or otherwise in proximity' to the user. For example, the waveguide(s) may be transparent such that the real-world light passes through the waveguide(s) to the user’s eye(s), as the virtual image elements are projected as an augmentation to the real-world scene. To prevent the optical power of the first EDOF lensfrom also be applied to the real-world light, thus changing the appearance of the real-world environment, a second EDOF lens may be included in the AR display device between the waveguide(s) and the world. The second EDOF lens may have an equal and opposite optical power to that of the first EDOF lens, to ensure that the perceived depth of real-world objects is not altered along with the virtual image elements. In some embodiments, the first EDOF lens (e.g., the eye-side EDOF lens) between the waveguide(s) and the eye(s) has a negative optical power, and the second EDOF lens the waveguide(s) and the world (e.g., the world-side EDOF lens) has a positive optical power to cancel out the optical power of the first EDOF lens. In this example, the EDOF lenses operate to impart negative optical power to the projected virtual image elements without altering the perceived depth of real- world objects.

[0007] It is desirable to minimize the size and weight of the wearable AR display device to provide a comfortable wearing experience for the user, for example to have the form factor of the wearable device be as close as possible to that of a ty pical pair of eyeglasses, while still maintaining the desired functionality of the wearable AR display device. Use of traditional concave and convex lenses as the EDOF lenses may add undesirable width and / or weight to the portion of the wearable device that is in front of the user’s eye(s) while the device is being worn. Accordingly, in some embodiments one or both of the eye-side and world-side EDOF lenses is a compact lens that provides the desired optical power but has a width and / or weight that is lens than that of a traditional lens. In some embodiments, the compact lens is a Fresnel lens. In some embodiments, the compact lens is a flattened periphery' lens in which an outer region of the lens (away from its center) is at least partly flattened in shape relative to the center portion of the lens that has optical power. Embodiments also support the use of other types of compact lenses.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 illustrates a user’s view of augmented reality (AR) through an AR device.

[0009] FIG. 2 illustrates an example of a wearable display system.

[0010] FIG. 3 illustrates a conventional display system for simulating three-dimensional(3D) image data for a user.

[0011] FIG. 4 illustrates aspects of an approach for simulating 3D image data using multiple depth planes.

[0012] FIGS. 5A. 5B, and 5C illustrate relationships between radius of curvature and focal radius.

[0013] FIG. 5D illustrates a representation of the accommodation-vergence response of the human visual system.

[0014] FIG. 5E illustrates examples of different accommodative states and vergence states of a pair of eyes of the user.

[0015] FIG. 5F illustrates an example of a representation of a view of a user viewing content via a display system.

[0016] FIG. 5G illustrates another example of a representation of a view of a user viewing content via a display system.

[0017] FIG. 6 illustrates an example of a waveguide stack for outputting image information to a user in an AR eyepiece.

[0018] FIGS. 7A and 7B illustrate examples of exit beams that are output by a waveguide.

[0019] FIG. 7C illustrates aspects of an approach for simulating three-dimensional imagery' by modifying wavefront divergence.

[0020] FIG. 8 illustrates an example of a stacked waveguide assembly in which each depth plane includes images formed using multiple different component colors.

[0021] FIG. 9A illustrates a cross-sectional side view of an example of a set of stacked waveguides that each includes an in-coupling optical element.

[0022] FIG. 9B illustrates a perspective view of an example of the plurality of stacked waveguides of FIG. 9A.

[0023] FIG. 9C illustrates a top-down plan view of an example of a plurality of stacked waveguides.

[0024] FIG. 9D illustrates a top-down plan view of an example of a plurality of stacked waveguides.

[0025] FIG. 10 illustrates an example of a visible optics assembly in a wearable display system.

[0026] FIG. 11 illustrates a cross-sectional side view of example extended depth of field (EDOF) lenses.

[0027] FIG. 12 illustrates a cross-sectional side view of example EDOF lenses with a coating and / or embedding material.

[0028] FIGS. 13A, 13B, 13C, and 13D illustrate example arrangements of EDOF lenses providing optical power in one or more regions of the lens.

[0029] FIGS. 14A and 14B illustrate a cross-sectional side view of example EDOF lenses providing optical power in one or more regions of the lens.

[0030] FIG. 15 illustrates a schematic of an example process for fabricating an EDOF lens.

[0031] FIG. 16 illustrates a cross-sectional side view of example EDOF lenses.

[0032] FIG. 17 illustrates example fields of view in a display system.

[0033] FIGS. 18, 19, and 20 illustrate a cross-sectional side view7of example EDOF lenses providing optical power within a display device.DETAILED DESCRIPTION

[0034] This disclosure describes the use of compact extended depth of field (EDOF) lenses in a wearable augmented reality (AR) display device, to reduce the weight and / or size of a visible optics assembly (VOA) of the device that is at least partly situated in front of the user’s eye(s) while the device is being worn. In some embodiments, the VOA of a wearable AR display device includes waveguide(s) that convey light for virtual image elements (e.g., virtual objects) from a projection system that generates the light for the virtual image elements, to the eye(s) of the user while the device is being worn. A first (eye-side) EDOF lens is located in the VOA between the waveguide(s) and the eye(s) to impart a (e.g., negative) optical powder to the virtual image elements, and a second (worldwide) EDOF lens is located in the VOA between the waveguide(s) and the world (e.g., on an opposite side of the waveguide(s) from the eye-side EDOF lens) to impart a (e.g., positive) optical power to the world light entering the device from the real world. The substantially equal and opposite optical powers of the two EDOF lenses ensure that the depth of real -world objects is not perceivably altered (or is minimally altered) while the perceived depth of the virtual image elements is altered by the eye-side EDOF lens. To reduce the size and weight of the VOA, one or more of the EDOF lenses is a compact lens such as a Fresnel lens or a flattened periphery lens, as described further herein.

[0035] FIG. 2 illustrates an example wearable display system 60, which may also be described as a head-mountable display (HMD) system 60. The display system 60 includes a display 70, which may also be described as eyepiece 70. The display system 60 can be configured to provide an AR experience for the user 90, while the user is wearing the display headset. The system 60 includes various mechanical and electronic modules and systems to support the functioning of the display 70. The display 70 may be coupled to or otherwise supported by a frame 80, which is wearable by the display system user 90 and which is configured to position the display 70 in front of one or both of the eyes of the user 90. Accordingly, the display 70 may be considered eyewear in some embodiments. Thedisplay 70 may include waveguide(s), projection system(s), and / or other optical components as described further herein.

[0036] In some embodiments, at least one speaker 100 is coupled to the frame 80 and is positioned adjacent to the ear canal of the user 90. At least one other speaker (not shown) may optionally be positioned adjacent to the other ear canal of the user 90, e.g., to provide a stereo and / or shapeable sound experience. The display system 60 may also include one or more microphones 110 to detect sound. The microphone(s) 110 can allow the user 90 to provide audio inputs or commands to the system 60 (e.g., through the selection of voice menu commands, natural language questions, etc.), and / or can allow audio communication with other person(s) (e g., with other users of similar display systems). The microphone(s) 110 can also collect audio data from the user's surroundings (e.g.. sounds from the user 90, other user(s), and / or environment). In some embodiments, the display system 60 may also include one or more peripheral sensors 120a, which may be separate from the frame 80 and attached to the body of the user 90 (e.g., on the head, torso, an extremity, etc.). In some instances, the peripheral sensor(s) 120a and / or other sensor(s) described herein may acquire data that indicates the physiological state of the user 90. In some examples, at least peripheral sensor 120a is an electrode.

[0037] In some embodiments, the display 70 is operatively coupled by a communications link 130, such as by a wired lead or through a wireless connection, to a local processing module 140. The module 140 may be mounted in a variety of configurations, such as fixedly attached to the frame 80 or otherwise integrated into the wearable headset, fixedly attached to a helmet or hat worn by the user, embedded in headphones, or removably attached to the user 90 (e.g., in a backpack-sty le configuration or in a belt-coupling style configuration). Similarly, the sensor(s) 120a may be operatively coupled by a communications link 120b (e.g., a wired lead or wireless connection) to the module 140. The module 140 may include at least one hardware computer processor configured to execute instructions to perform operations, such as a central processing unit (CPU), a graphics processing unit (GPU), dedicated processing hardware, and so forth. The module 140 may also include digital memory, such as non-volatile memory (e.g., flash memory or a hard disk drive), which may be utilized to assist in the processing, caching, and storage of data.

[0038] The data that is processed, cached, stored, and / or otherwise handled by the local module 140 may include data captured from sensors, which may be operatively coupled to the frame 80 or otherwise attached to the user 90. Such sensors may include the sensor(s)120a, image capture device(s) (e.g., cameras), the microphone(s) 110, inertial measurement units (IMUs), accelerometers, compasses, navigation systems (e.g.. satellite-based or otherwise) such as Global Positioning System (GPS) transceivers, radio devices, gyroscopic sensors (gyros), and / or other sensors discussed herein. The data may also include data that is acquired, processed, or stored using a remote processing module 150 and / or a remote data repository 160. In some instances, the data includes data related to virtual content, such as data describing virtual object(s) to be rendered through the display 70.

[0039] The module 140 may be operatively coupled through communication links 170, 180 (e.g., wired or wireless communication links) to the remote processing module 150 and the remote data repository 160 such that these remote modules 150, 160 are operatively coupled to each other and available as resources to the module 140. In some embodiments, the module 140 may include one or more of the sensors discussed herein, such as the image capture devices, microphones, inertial measurement units, accelerometers, compasses, GPS units, radio devices, and / or gyros. In some embodiments, one or more of these sensors may be attached to the frame 80 or may be standalone devices that communicate with module 140 by wired or wireless communication pathways.

[0040] The remote processing module 150 may include one or more processors (e.g., CPU, GPU, etc.) to analyze and process data, such as image, graphics, and / or audio information. In some embodiments, the remote data repository 160 may be a digital data storage facility, which may be available through the internet or other networking configuration, e.g., in a cloud-based resource configuration. In some embodiments, the remote data repository' 160 may include one or more remote servers, which provide information (e.g., information for generating AR content) to the local module 140 and / or the remote processing module 150. In some embodiments, the local module 140 may communicate with the remote modules 150 and / or 160 to share data processing or data storage load to facilitate operations of the system 60. In other embodiments, the wearable system 60 may operate in a manner that is fully autonomous without necessitating use of the remote module(s) 150 or 160, such that all of the data is stored on, and all of the computations are performed by, the local module 140.

[0041] The perception of an image as being three-dimensional (3D) may be achieved by providing slightly different presentations of the image to each eye of the user. FIG. 3 illustrates a conventional display system for simulating three-dimensional image data for a user. Two distinct images 190 and 200 - one for each of the eyes 210 and 220 - are outputto the user. The images 190 and 200 are spaced from the eyes 210 and 220 by a distance 230 along an optical axis (e.g., the Z-axis) that is parallel to the line of sight of the user. The images 190 and 200 are flat and the eyes 210 and 220 may focus on the images by assuming a single accommodated state. Such 3D display systems rely on the human visual system to combine the images 190 and 200 to provide a perception of depth and / or scale for the combined image.

[0042] However, the human visual system is complicated and providing a realistic perception of depth is challenging. For example, many users of conventional 3D display systems find such systems to be uncomfortable or may not perceive a sense of depth at all. Objects may be perceived as being 3D due to a combination of vergence and accommodation. Vergence movements (e.g., rotation of the eyes so that the pupils move toward or away from each other to converge the respective lines of sight of the eyes to fixate upon an object) of the two eyes relative to each other are closely associated with focusing (accommodation) of the lenses of the eyes. Under normal conditions, changing the focus of the lenses of the eyes, or accommodating the eyes, to change focus from one object to another object at a different distance will automatically cause a matching change in vergence to the same distance, under a relationship known as the accommodationvergence reflex, as well as pupil dilation or constriction. Likewise, under normal conditions, a change in vergence w ill trigger a matching change in accommodation of lens shape and pupil size. Many stereoscopic or 3D display systems display a scene using slightly different presentations (e g., slightly different images) to each eye such that a 3D perspective is perceived by the human visual system. Such systems can be uncomfortable for some users, however, since they simply provide image information at a single accommodated state and work against the accommodation-vergence reflex. Display systems that provide a better match between accommodation and vergence may form more realistic and comfortable simulations of 3D image data.

[0043] FIG. 4 illustrates aspects of an approach for simulating three-dimensional image data using multiple depth planes. With reference to FIG. 4, the eyes 210 and 220 assume different accommodated states to focus on objects at various distances on the z-axis. Consequently, a particular accommodated state may be said to be associated with a particular one of the illustrated depth planes 240, which has an associated focal distance, such that objects or parts of objects in a particular depth plane are in focus when the eye is in the accommodated state for that depth plane. In some embodiments, 3D image data may be simulated by providing different presentations of an image for each of the eyes 210 and220, and also by providing different presentations of the image corresponding to multiple depth planes. While the respective fields of view of the eyes 210 and 220 are shown as being separate for cl ari ty of illustration, they may overlap, for example, as distance along the z-axis increases. In addition, while the depth planes are show n as being flat for ease of illustration, it will be appreciated that the contours of a depth plane may be curved in physical space, such that all features in a depth plane are in focus with the eye in a particular accommodated state.

[0044] The distance between an object and an eye 210 or 220 may also change the amount of divergence of light from that object, as viewed by that eye. That is, light from objects at different distances from the eyes have wavefronts with different amounts of divergence. FIGS. 5A-5C illustrate relationships between distance and the divergence of light rays. The distance between the object and the eye 210 is represented by, in order of decreasing distance, Rl, R2, and R3. As shown in FIGS. 5A-5C, the light rays become more divergent as distance to the object decreases. As distance increases, the light rays become more collimated. Stated another way, it may be said that the light field produced by a point (e.g., the object or a part of the object) has a spherical wavefront curvature, which is a function of how far aw ay the point is from the eye of the user. The curvature increases with decreasing distance between the object and the eye 210. Consequently, at different depth planes, the degree of divergence of light rays is also different, with the degree of divergence increasing with decreasing distance between the depth planes and the user's eye 210. While only a single eye 210 is illustrated for clarity of illustration in FIGS. 5A-5C and other figures herein, it will be appreciated that the discussions regarding the eye 210 may be applied to both eyes 210 and 220 of a user.

[0045] With continued reference to FIGS. 5A-5C, light from an object that the viewer's eyes are fixated on may have different degrees of wavefront divergence. Due to the different amounts of wavefront divergence, the light may be focused differently by the lens of the eye, which in turn may cause the lens to assume different shapes to form a focused image on the retina of the eye. Where a focused image is not formed on the retina, the resulting retinal blur acts as a cue to accommodation that causes a change in the shape of the lens of the eye until a focused image is formed on the retina. For example, the cue to accommodation may trigger the ci 1 i ary muscles surrounding the lens of the eye to relax or contract, thereby modulating the force applied to the suspensory ligaments holding the lens, thus causing the shape of the lens of the eye to change until retinal blur of an object of fixation is eliminated or minimized, thereby forming a focused image of the object offixation on the retina (e.g., fovea) of the eye. The process by which the lens of the eye changes shape may be referred to as accommodation, and the shape of the lens of the eye to form a focused image of the object of fixation on the retina (e.g., fovea) of the eye may be referred to as an accommodative state.

[0046] A highly believable simulation of perceived depth may be achieved by providing, to the eye. different presentations of an image corresponding to each of a limited number of depth planes. The different presentations may be separately focused by the user’s eye, thereby helping to provide the user with depth cues based on the amount of accommodation of the eye to bring into focus different image features for the scene located on different depth planes and / or based on observing different image features on different depth planes being out of focus.

[0047] With reference now to FIG. 5D, a representation of the accommodationvergence response of the human visual system is illustrated. The movement of the eyes to fixate on an object causes the eyes to receive light from the object, with the light forming an image on each of the retinas of the eyes. The presence of retinal blur in the image formed on the retina may provide a cue to accommodation, and the relative locations of the image on the retinas may provide a cue to vergence. The cue to accommodation causes accommodation to occur, resulting in the lenses of the eyes each assuming a particular accommodative state that forms a focused image of the object on the retina (e.g., fovea) of the eye. On the other hand, the cue to vergence causes vergence movements (rotation of the eyes) to occur such that the images formed on each retina of each eye are at corresponding retinal points that maintain single binocular vision. In these positions, the eyes may be said to have assumed a particular vergence state. With continued reference to FIG. 5D, accommodation may be understood to be the process by which the eye achieves a particular accommodative state, and vergence may be understood to be the process by which the eye achieves a particular vergence state. As indicated in FIG. 5D, the accommodative and vergence states of the eyes may change if the user fixates on another object. For example, the accommodated state may change if the user fixates on a new object at a different depth on the z-axis.

[0048] Without being limited by theory, viewers of an object may perceive the object as being 3D due to a combination of vergence and accommodation. As noted above, vergence movements (e.g., rotation of the eyes so that the pupils move toward or away from each other to converge the lines of sight of the eyes to fixate upon an object) of the two eyes relative to each other are closely associated with accommodation of the lenses ofthe eyes. Under normal conditions, changing the shapes of the lenses of the eyes to change focus from one object to another object at a different distance will automatically cause a matching change in vergence to the same distance, under a relationship known as the accommodation-vergence reflex. Likewise, a change in vergence will trigger a matching change in lens shape under normal conditions.

[0049] With reference now to FIG. 5E, examples of different accommodative and vergence states of the eyes are illustrated. In the example show n, a first pair of eyes 222a are fixated on an object at optical infinity, while a second pair of eyes 222b are fixated on an object 221 at a distance that is less than optical infinity. Notably, the vergence states of each pair of eyes is different, with the first pair of eyes 222a directed straight ahead and the second pair of eyes 222b converged on the object 221. The accommodative states of the eyes forming each pair of eyes 222a and 222b are also different, as represented by the different shapes of the lenses 220a, 220b.

[0050] Undesirably, many users of conventional 3D display systems find such conventional systems to be uncomfortable or may not perceive a sense of depth at all due to a mismatch between accommodative and vergence states in these displays. As noted above, many stereoscopic or 3D display systems display a scene by providing slightly different images to each eye. Such systems are uncomfortable for many viewers, because they provide different presentations of a scene that cause changes in the vergence states of the eyes without causing a corresponding change in the accommodative states of those eyes. Rather, the images are shown by a display at a fixed distance from the eyes, such that the eyes view all the image information at a single accommodative state. Such an arrangement works against the accommodation-vergence reflex by causing changes in the vergence state without a matching change in the accommodative state. This mismatch is believed to cause viewer discomfort. Display systems that provide a better match between accommodation and vergence may form more realistic and comfortable simulations of 3D imagery.

[0051] Without being limited by theory , it is believed that the human eye typically may interpret a finite number of depth planes to provide depth perception. Consequently, a highly believable simulation of perceived depth may be achieved by providing, to the eye, different presentations of an image corresponding to each of these limited numbers of depth planes. In some embodiments, the different presentations may provide both cues to vergence and matching cues to accommodation, thereby providing physiologically correct accommodation-vergence matching.-l i

[0052] With continued reference to FIG. 5E, two depth planes 240a and 240b are show n, corresponding to different distances in space from the eyes. For a given depth plane, vergence cues may be provided by the displaying of images of appropriately different perspectives for each eye. In addition, for a given depth plane, light forming the images provided to each eye may have a wavefront divergence corresponding to a light field produced by a point at the distance of that depth plane.

[0053] In the illustrated embodiment, the distance, along the z-axis, of the depth plane 240a containing the point 221 is 1 m. As used herein, distances or depths along the z-axis may be measured with a zero-point located at the exit pupils of the user's eyes. Thus, a depth plane 240a located at a depth of 1 m corresponds to a distance of 1 m away from the exit pupils of the user's eyes, on the optical axis of those eyes with the eyes directed towards optical infinity. As an approximation, the depth or distance along the z-axis may be measured from the display in front of the user's eyes (e.g., from the surface of a waveguide), plus a value for the distance betw een the device and the exit pupils of the user's eyes. That value may be called the eye relief and corresponds to the distance between the exit pupil of the user's eye and the display worn by the user in front of the eye. In practice, the value for the eye relief may be a normalized value used generally for all viewers. For example, the eye relief may be assumed to be 20 millimeters (mm) such that a depth plane that is at a depth of 1 meter (m) may be at a distance of 980 mm in front of the display.

[0054] With reference now to FIGS. 5F and 5G, examples of matched accommodationvergence distances and mismatched accommodation-vergence distances are illustrated, respectively. As illustrated in FIG. 5F, the display system may provide images of a virtual object to each of the user's eyes 210, 220. The images may cause the eyes to assume a vergence state in which the eyes converge on a point 15 on a depth plane 240. In addition, the images may be formed by light having a wavefront curvature corresponding to real objects at that depth plane 240. As a result, the eyes assume an accommodative state in which the images are in focus on the retinas of those eyes. Thus, the user may perceive the virtual object as being at the point 15 on the depth plane 240.

[0055] It will be appreciated that each of the accommodative and vergence states of the eyes are associated with a particular distance on the z-axis. For example, an object at a particular distance from the eyes causes those eyes to assume particular accommodative states based upon the distance of the object. The distance associated with a particular accommodative state may be referred to as the accommodation distance Ad. Similarly, there are particular vergence distances Vad associated with the eyes in particular vergencestates or positions relative to one another. If the accommodation distance and the vergence distance match, as in the example of FIG. 5F, the relationship between accommodation and vergence may be said to be physiologically correct. This is considered to be the most comfortable scenario for a viewer.

[0056] In stereoscopic displays, however, the accommodation distance and the vergence distance may not always match. For example, as illustrated in FIG. 5G, images displayed to the eyes may be displayed with wavefront divergence corresponding to depth plane 240, and the eyes may assume a particular accommodative state in which the points 15a, 15b on that depth plane are in focus for the respective eyes. However, the images displayed to the eyes may provide cues for vergence that cause the eyes to converge on a point 15 that is not located on the depth plane 240, e.g.. that is located beyond the depth plane as shown, or closer than the depth plane. As a result, the accommodation distance Ad, corresponding to the distance from the exit pupils of the eyes to the depth plane 240, is different from the vergence distance Ved corresponding to the larger distance from the exit pupils of the eyes to the point 15. Consequently, there is an accommodation-vergence mismatch. Such a mismatch is considered undesirable and may cause discomfort in the user. It will be appreciated that the mismatch corresponds to the difference between the two distances (e.g., Ved - Ad) and may be characterized using diopters.

[0057] In some embodiments, it will be appreciated that a reference point other than exit pupils of the eyes may be utilized for determining distance for determining accommodation-vergence mismatch, so long as the same reference point is utilized consistently for both the accommodation distance and the vergence distance. For example, the distances could be measured from the cornea to the depth plane, from the retina to the depth plane, from the eyepiece (e.g., a waveguide of the display device) to the depth plane, and so on.

[0058] Without being limited by theory, it is believed that users may still perceive accommodation-vergence mismatches of up to about 0.25 diopter, up to about 0.33 diopter, and up to about 0.5 diopter as being physiologically correct, without the mismatch itself causing significant discomfort. In some embodiments, display systems disclosed herein present images to the viewer having accommodation-vergence mismatch of about 0.5 diopter or less. In some embodiments, the accommodation-vergence mismatch of the images provided by the display system is about 0.33 diopter or less. In some embodiments, the accommodation-vergence mismatch of the images provided by the display system is about 0.25 diopter or less, including about 0.1 diopter or less.

[0059] FIG. 6 illustrates an example of a waveguide stack for outputting image information to a user in an example AR display system 250. The display system 250 includes a stack of waveguides 260, also described as a stacked waveguide assembly, which may be utilized to provide 3D perception to the eye / brain of the user through use of a plurality of waveguides 270, 280, 290, 300, and 310. In some embodiments, the display system 250 is the system 60 of FIG. 2, with FIG. 6 schematically showing some parts of that system 60 in greater detail. For example, the waveguide assembly 260 may be part of the display 70 of FIG. 2. It will be appreciated that the display system 250 may be considered a light field display in some embodiments.

[0060] The waveguide assembly 260 may also include a plurality of features 320, 330, 340, and 350 that are arranged between the waveguides. In some embodiments, the features 320, 330, 340, and 350 may be one or more lenses. The waveguides 270, 280, 290, 300, 310 and / or the plurality of lenses 320, 330, 340, 350 may be configured to send image information to the eye with various levels of wavefront curvature or light ray divergence. Each waveguide level may be associated with a particular depth plane and may be configured to output image information corresponding to that depth plane. Image injection devices 360, 370, 380, 390, 400 may function as a source of light for the waveguides and may be utilized to inject image information into the waveguides 270, 280, 290, 300, 310, each of which may be configured, as described herein, to distribute incoming light across each respective waveguide, for output toward the eye 210. Light exits an output surface 410, 420, 430, 440, 450 of each respective image injection device 360, 370, 380, 390, 400 and is injected into a corresponding input surface 460, 470, 480, 490, 500 of the respective waveguides 270, 280, 290, 300, 310. In some embodiments, the each of the input surfaces 460, 470. 480, 490, 500 may be an edge of a corresponding waveguide, or may be part of a major surface of the corresponding waveguide (e.g., one of the broader waveguide surfaces that directly faces outward toward the world 510 or inward toward the user’s eye 210 when the system is being worn). In some embodiments, a beam of light (e.g., a collimated beam) may be injected into each waveguide and may be replicated, such as by sampling into beamlets by diffraction, in the waveguide and then directed toward the eye 210 with an amount of optical power corresponding to the depth plane associated with that particular w aveguide. In some embodiments, a single one of the image injection devices 360, 370, 380, 390, 400 may be associated with, and inject light into, a plurality (e.g., three) of the waveguides 270, 280, 290, 300. 310.

[0061] In some embodiments, the image injection devices 360, 370, 380, 390, 400 are discrete displays that each produce image information for injection into a corresponding waveguide 270, 280, 290, 300, 310, respectively. In some other embodiments, the image injection devices 360, 370, 380, 390, 400 are the output ends of a single multiplexed display which may transmit image information via one or more optical conduits, such as fiber optic cables, to each of the image injection devices 360, 370. 380, 390. 400. It will be appreciated that the image information provided by the image injection devices 360, 370, 380, 390, 400 may include light of different wavelengths, or colors.

[0062] In some embodiments, the light injected into the waveguides 270, 280, 290, 300, 310 is provided by a light projector system 520, which includes at least one light module 530, which may include at least one light source or light emitter, such as a light emitting diode (LED). The light from the light module(s) 530 may be directed to, and modulated by, at least one light modulator 540 (e.g., a spatial light modulator), in some instances via at least one beamsplitter (BS) 550. The light modulator(s) 540 may spatially and / or temporally change the perceived intensity of the light injected into the waveguides 270, 280, 290. 300, 310. Examples of spatial light modulators include liquid crystal displays (LCD), such as a liquid crystal on silicon (LCOS) displays. In some implementations, the spatial light modulators include a microelectromechanical system (MEMS), such as a digital light processing (DLP) device.

[0063] In some embodiments, the light projector system 520. or one or more components thereof, may be attached to the frame 80 described with reference to FIG. 2. For example, the light projector system 520 may be part of a temporal portion (e.g., ear stem 82) of the frame 80 or disposed at an edge of the display 70. In some embodiments, the light module(s) 530 may be separate from the BS 550 and / or light modulator(s) 540.

[0064] In some embodiments, the display system 250 may be a scanning fiber display comprising one or more scanning fibers to project light in various patterns (e.g., raster scan, spiral scan, Lissajous patterns, etc.) into one or more waveguides 270, 280, 290, 300, 310 and ultimately into the eye 210 of the user. In some embodiments, the illustrated image injection devices 360, 370, 380, 390, 400 may schematically represent a single scanning fiber or a bundle of scanning fibers configured to inject light into one or a plurality of the waveguides 270, 280, 290, 300, 310. In some other embodiments, the illustrated image injection devices 360, 370, 380, 390, 400 may schematically represent a plurality of scanning fibers or a plurality of bundles of scanning fibers, each of which are configured to inject light into an associated one of the waveguides 270, 280, 290, 300, 310. One ormore optical fibers may transmit light from the light module 530 to the one or more waveguides 270. 280, 290, 300, and 310. In addition, one or more intervening optical structures may be provided between the scanning fiber, or fibers, and the one or more waveguides 270, 280, 290, 300, 310 to, for example, redirect light exiting the scanning fiber into the one or more waveguides 270, 280, 290, 300, 310.

[0065] A controller 560 controls the operation of the stacked waveguide assembly 260, including operation of the image injection devices 360, 370, 380, 390, 400, the light source(s) 530, and the light modulator(s) 540. In some embodiments, the controller 560 is part of the local data processing module 140. The controller 560 includes programming (e.g., instructions in a non-transitory medium) that regulates the timing and provision of image information to the waveguides 270. 280, 290, 300, 310. In some embodiments, the controller 560 may be a single integral device, or a distributed system connected by wired or wireless communication channels. The controller 560 may be part of the processing modules 140 and / or 150 (as shown in FIG. 2) in some embodiments.

[0066] The waveguides 270, 280, 290. 300, 310 may be configured to propagate light within each respective waveguide by total internal reflection (TIR). The waveguides 270, 280, 290, 300, 310 may each be planar or have another shape (e.g., curved), with major top and bottom surfaces and edges extending between those major top and bottom surfaces. In the illustrated configuration, the waveguides 270, 280, 290, 300, 310 may each include out- coupling optical elements 570, 580. 590, 600, 610 that are configured to extract light out of a waveguide by redirecting at least a portion of the light, which is propagating within each respective w aveguide, out of the waveguide to output image information to the eye 210. Extracted light may also be referred to as out-coupled light and the out-coupling optical elements light may also be referred to light extracting optical elements. An extracted beam of light may be output by the waveguide at locations at which the light propagating in the w aveguide strikes a light extracting optical element. The out-coupling optical elements 570, 580, 590, 600, 610 may be, for example, diffractive optical features, including diffractive gratings, as discussed further herein. While the out-coupling optical elements 570, 580, 590, 600, 610 are illustrated as being disposed at the bottom major surfaces of the waveguides 270, 280, 290, 300, 310, in some embodiments they may be disposed at the top and / or bottom major surfaces, and / or may be disposed directly in the volume of the waveguides 270, 280, 290, 300, 310, as discussed further herein. In some embodiments, the out-coupling optical elements 570, 580. 590, 600, 610 may be formed in a layer of material that is attached to a transparent substrate to form the waveguides 270,280, 290, 300, 310. In some other embodiments, the waveguides 270, 280, 290, 300, 310 may be a monolithic piece of material and the out-coupling optical elements 570, 580, 590, 600, 610 may be formed on a surface and / or in the interior of that piece of material.

[0067] In some embodiments, the display system 250 may be configured to provide substantially continuous cues to vergence and multiple discrete cues to accommodation. The cues to vergence may be provided by displaying different images to each of the eyes of the user, and the cues to accommodation may be provided by outputting the light that forms the images with selectable discrete amounts of wavefront divergence. Stated another way, the display system 250 may be configured to output light with variable levels of wavefront divergence. In some embodiments, each discrete level of wavefront divergence corresponds to a particular depth plane and may be provided by a particular one of the waveguides 270, 280, 290, 300, 310.

[0068] Each waveguide 270, 280, 290, 300, 310 may output light to form an image corresponding to a particular depth plane. For example, the waveguide 270 nearest the eye may deliver collimated beams of light to the eye 210. The collimated beams of light may be representative of the optical infinity focal plane. The waveguide 280, e.g., the next waveguide further from the eye, may output collimated beams of light which pass through the first lens 350 (e.g., a negative lens) before reaching the eye 210. The first lens 350 may add a slight convex wavefront curvature to the collimated beams so that the eye / brain interprets light coming from that waveguide 280 as originating from a first focal plane closer inward toward the eye 210 from optical infinity. Similarly, the third waveguide 290 passes its output light through both the first lens 350 and the second lens 340 before reaching the eye 210. The combined optical power of the first lens 350 and the second lens 340 may add another incremental amount of wavefront curvature so that the eye / brain interprets light coming from the third waveguide 290 as originating from a second focal plane that is even closer inward from optical infinity than was light from the second waveguide 280.

[0069] The other waveguide layers 300, 310 and lenses 330, 320 may be similarly configured, with the highest waveguide 310 in the stack (e.g., the waveguide farthest from the eye) sending its output through all of the lenses between it and the eye for an aggregate focal power representative of the closest focal plane to the person. To compensate for the stack of lenses 320, 330, 340, 350 when viewing / interpreting light coming from the world 510 on the other side of the stacked waveguide assembly 260, a compensating lens layer 620 may be disposed at the top of the stack to compensate for the aggregate optical powerof the lens stack 320, 330, 340, 350 below. Such a configuration provides as many perceived focal planes as there are available waveguide / lens pairings. Both the out- coupling optical elements of the waveguides and the focusing aspects of the lenses may be static (e.g., not dynamic or electro-active). In some alternative embodiments, either or both may be dynamic using electro-active features.

[0070] In some embodiments, two or more of the waveguides 270, 280, 290, 300, 310 may have the same associated depth plane. For example, multiple waveguides 270, 280, 290, 300, 310 may output images set to the same depth plane, or multiple subsets of the waveguides 270, 280, 290, 300, 310 may output images set to the same plurality of depth planes, with one set for each depth plane. This can provide advantages for forming a tiled image to provide an expanded field of view at those depth planes.

[0071] The out-coupling optical elements 570, 580, 590, 600, 610 may be configured to both redirect light out of their respective waveguides and to output this light with the appropriate amount of divergence or collimation for a particular depth plane associated with the waveguide. As a result, waveguides having different associated depth planes may have different configurations of out-coupling optical elements 570, 580, 590, 600, 610, which output light with a different amount of divergence depending on the associated depth plane. In some embodiments, the light extracting optical elements 570, 580, 590, 600, 610 may be volumetric or surface features, which may be configured to output light at specific angles. For example, the light extracting optical elements 570, 580, 590. 600, 610 may be volume holograms, surface holograms, and / or diffraction gratings. In some embodiments, the features 320, 330, 340, 350 may not be lenses; rather, they may simply be spacers (e.g., cladding layers and / or structures for forming air gaps).

[0072] In some embodiments, the out-coupling optical elements 570. 580, 590. 600, 610 are diffractive features that form a diffraction pattern, or a diffractive optical element (DOE). In some examples, the DOEs have a diffraction efficiency sufficiently low such that only a portion of the light in a beam is deflected and re-directed toward the eye 210 with each interaction of the beam with the DOE, while the remaining light continues to move through a waveguide via TIR. In this way, the light cany i ng the image information is divided into a number of related exit beams that exit the waveguide at a multiplicity of locations and the result is a fairly uniform pattern of exit emission toward the eye 210 for a particular collimated beam propagating in the waveguide. Stated somewhat differently, the exit pupil of the light module 530 is replicated across the waveguide to create a plurality of output beams carrying the image information from light source 530, effectivelyexpanding the number of locations where the eye 210 may intercept the replicated light source exit pupil. These diffractive features may also have a variable diffractive efficiency across their geometry to improve uniformity of light output by the waveguide.

[0073] In some embodiments, one or more diffractive features may be switchable between “on"’ states in which they actively diffract, and “off’ states in which they do not significantly diffract. For instance, a switchable diffractive element may include a layer of polymer dispersed liquid crystal in which microdroplets form a diffraction pattern in a host medium, and the refractive index of the microdroplets may be switched to substantially match the refractive index of the host material (in which case the pattern does not appreciably diffract incident light) or the microdroplet may be switched to an index that does not match that of the host medium (in which case the pattern actively diffracts incident light).

[0074] In some embodiments, a camera assembly 630, e.g., a digital camera, including visible light and / or infrared (IR) light cameras, may be provided to capture images of the eye 210, parts of the eye 210, or at least a portion of the tissue surrounding the eye 210 to, for example, detect user inputs, extract biometric information from the eye, estimate and track the gaze direction of the eye, to monitor the physiological state of the user, and so forth. In some embodiments, the camera assembly 630 may include an image capture device and a light source to project light (e.g., IR or near-IR light) to the eye, which may then be reflected by the eye and detected by the image capture device. In some embodiments, the light source includes one or more LEDs, emitting in IR or near-IR. In some embodiments, the camera assembly 630 may be attached to the frame 80 (FIG. 2) and may be in electrical communication with the processing modules 140 and / or 150, which may process image information from the camera assembly 630 to make various determinations regarding, for example, the physiological state of the user, the gaze direction of the wearer, iris identification, etc. In some embodiments, one camera assembly 630 may be utilized for each eye, to separately monitor each eye.

[0075] FIG. 7A illustrates an example of exit beams output by a waveguide. One waveguide 270 is illustrated (with a perspective view), but other waveguides in the waveguide assembly 260 (FIG. 6) may function similarly. Light 640 is injected into the waveguide 270 at the input surface 460 of the waveguide 270 and propagates within the waveguide 270 by TIR. Through interaction with diffractive features, at least a portion of the light exits the waveguide as exit beams 650. The exit beams 650 replicate the exit pupil from a projector device (e.g., projector system 520) which projects images into thewaveguide. Any one of the exit beams 650 includes a sub-portion of the total energy of the input light 640. And in a perfectly efficient system, the summation of the energy in all the exit beams 650 would equal the energy of the input light 640. The exit beams 650 are illustrated as being substantially parallel in FIG. 7A but, as discussed herein, some amount of optical power may be imparted depending on the depth plane associated with the waveguide 270. Parallel exit beams may be indicative of a waveguide including out- coupling optical elements that out-couple light to form images that appear to be set on a depth plane at a large distance (e.g., optical infinity) from the eye 210. Other waveguides or other sets of out-coupling optical elements may output an exit beam pattern that is more divergent, as shown in FIG. 7B, which would cause the eye 210 to accommodate to a closer distance to bring it into focus on the retina and would thus be interpreted by the brain as light from a distance closer to the eye 210 than optical infinity.

[0076] FIG. 7C illustrates aspects of an approach for simulating three-dimensional imagery' by modifying wavefront divergence. The display system includes a waveguide 270 that is configured to receive light 770 that is encoded with image information, and to output that light to the user’s eye 210. The waveguide 270 may also be referred to as an eyepiece, which relays image light 770 to the user’s eye 210. The waveguide 270 may output the light 650 with a defined amount of wavefront divergence corresponding to the wavefront divergence of a light field produced by a point on a desired depth plane 240. In some implementations, the same amount of wavefront divergence is provided for all objects presented on that depth plane. In addition, it will be illustrated that the other eye of the user may be provided with image information from a similar waveguide.

[0077] In some implementations, a single waveguide may be configured to output light with a set amount of wavefront divergence corresponding to a single or limited number of depth planes and / or the waveguide may be configured to output light of a limited range of wavelengths. Consequently, in some implementations, a plurality or stack of waveguides may be utilized to provide different amounts of w avefront divergence for different depth planes and / or to output light of different ranges of wavelengths. It will be appreciated that a depth plane may be planar or may follow the contours of a curved surface.

[0078] In some embodiments, a full color image may be formed at each depth plane by overlaying images in each of a plurality of component colors (e.g., three or more component colors, such as red, green, and blue). FIG. 8 illustrates an example of a stacked waveguide assembly in which each depth plane includes images formed using multiple different component colors. The illustrated embodiment shows depth planes 240a through 240f,although more or fewer depths are also contemplated. Each depth plane may have three or more component color images associated with it, including: a first image of a first color, G; a second image of a second color, R; and a third image of a third color, B. Different depth planes are indicated in the figure by different diopter powers following the letters G, R, and B. The numbers following each of these letters indicate diopters (1 / m), or inverse distance of the depth plane from a user, and each box in the figure represents an individual component color image. In some embodiments, to account for differences in the eye’s focusing of light of different wavelengths, the exact placement of the depth planes for different component colors may vary. For example, different component color images for a given depth plane may be placed on depth planes corresponding to different distances from the user. Such an arrangement may increase visual acuity and user comfort or may decrease chromatic aberrations.

[0079] In some embodiments, light of each component color may be output by a single dedicated waveguide and, consequently, each depth plane may have multiple waveguides associated with it. In such embodiments, each box in the figure may be understood to represent an individual waveguide, and three waveguides may be provided per depth plane so as to display three component color images per depth plane. While the waveguides associated with each depth plane are shown adjacent to one another in this drawing for ease of illustration, it will be appreciated that, in a phy sical device, the waveguides may be arranged in a stack with one waveguide per level. In some other embodiments, multiple component colors may be output by the same waveguide, such that, for example, a single waveguide may be provided per depth plane, two or more w aveguides may be provided per depth plane, and so forth.

[0080] With continued reference to FIG. 8. in some embodiments. G is the color green, R is the color red, and B is the color blue. In some other embodiments, other colors associated with other wavelengths of light, including yellow, magenta, and cyan, may be used in addition to or may replace one or more of red, green, or blue. In some embodiments, features 320, 330, 340, and 350 may be active or passive optical filters configured to block or selectively pass light from the ambient environment to the user’s eyes.

[0081] References to a given color of light throughout this disclosure should be understood to encompass light of one or more wavelengths within a range of wavelengths of light that are perceived by a user as being of that given color. For example, red light may include light of one or more wavelengths in the range of about 620 to 780 nm, green light may include light of one or more wavelengths in the range of about 492 to 577 nm,and blue light may include light of one or more wavelengths in the range of about 435 to 493 nm.

[0082] In some embodiments, the light source 530 (e.g., as in FIG. 6) may be configured to emit light of one or more wavelengths outside the visual perception range of the user, for example, IR or ultraviolet wavelengths. IR light can include light with wavelengths in a range from 700 nm to 10 pm. In some embodiments. IR light can include near-IR light with wavelengths in a range from 700 nm to 1.5 pm. In addition, the in-coupling, out- coupling, and other light redirecting structures of the waveguides of the display 250 may be configured to direct and emit this light out of the display towards the user’s eye 210, e.g., for imaging or user stimulation applications.

[0083] With reference now to FIG. 9A. in some embodiments, light impinging on a waveguide may be redirected so as to in-couple the light into the waveguide and enable the light to propagate within the waveguide through TIR. At least one in-coupling optical element may be used to redirect and in-couple the light into a corresponding waveguide. FIG. 9A illustrates a cross-sectional side view of an example of a set 660 of stacked waveguides that each includes an in-coupling optical element. The waveguides may each be configured to output light of one or more different wavelengths, or one or more different ranges of w avelengths. It will be appreciated that the stack 660 may correspond to the stack 260 (e.g.. as in FIG. 6) and the illustrated waveguides of the stack 660 may correspond to part of the plurality of waveguides 270. 280, 290, 300, 310, except that light from one or more of the image injection devices 360, 370, 380, 390, 400 is injected into the waveguides from a position or orientation that enables the light to be redirected for in-coupling into the waveguides.

[0084] The illustrated set 660 of stacked waveguides includes waveguides 670, 680, and 690. Each waveguide includes an associated in-coupling optical element (which may also be referred to as a light input area on the waveguide), with, for example, in-coupling optical element 700 disposed on a major surface (e.g., an upper major surface) of waveguide 670, in-coupling optical element 710 disposed on a major surface (e.g., an upper major surface) of waveguide 680, and in-coupling optical element 720 disposed on a major surface (e.g., an upper major surface) of waveguide 690. In some embodiments, one or more of the incoupling optical elements 700, 710, 720 may be disposed on the bottom major surface of the respective waveguide 670. 680, 690 (particularly where the one or more in-coupling optical elements are reflective optical elements). As illustrated, the in-coupling optical elements 700, 710, 720 may be disposed on the upper major surface of their respectivewav eguide 670, 680, 690 (or the top of the next lower waveguide), particularly where those in-coupling optical elements are transmissive optical elements. In some embodiments, the in-coupling optical elements 700, 710, 720 may be disposed in the body of the respective waveguide 670, 680, 690. In some embodiments, as discussed herein, the in-coupling optical elements 700, 710, 720 are wavelength selective, such that they selectively redirect one or more wavelengths of light, while transmitting other wavelengths of light. While illustrated on one side or comer of their respective waveguide 670, 680, 690, it will be appreciated that the in-coupling optical elements 700, 710, 720 may be disposed in other areas of their respective waveguide 670, 680, 690 in some embodiments. A waveguide may include any suitable number of in-coupling optical elements in any suitable location on one or both of the top major surface or the bottom major surface, or otherwise arranged in the waveguide.

[0085] As illustrated, the in-coupling optical elements 700, 710, 720 may be laterally offset from one another. In some embodiments, each in-coupling optical element may be offset such that it receives light without that light passing through another in-coupling optical element. For example, each in-coupling optical element 700, 710, 720 may be configured to receive light from a different image injection device 360, 370, 380, 390, and 400 as shown in FIG. 6, and may be separated (e.g., laterally spaced apart) from other incoupling optical elements 700, 710, 720 such that it substantially does not receive light from the other ones of the in-coupling optical elements 700, 710. 720. Alternatively, at least two of the in-coupling optical elements may be arranged at least partly over one another, such that at least a portion of the light that is in-coupled by one in-coupling optical element has previously passed through another in-coupling optical element.

[0086] Each waveguide also includes associated light distributing elements, with, for example, light distributing elements 730 disposed on a major surface (e.g., a top major surface) of waveguide 670, light distributing elements 740 disposed on a major surface (e.g., a top major surface) of waveguide 680, and light distributing elements 750 disposed on a major surface (e.g., a top major surface) of waveguide 690. In some other embodiments, the light distributing elements 730, 740, 750 may be disposed on a bottom major surface of associated waveguides 670, 680, 690, respectively. In some other embodiments, the light distributing elements 730, 740, 750 may be disposed on both top and bottom major surface of associated waveguides 670, 680, 690 respectively; or the light distributing elements 730. 740, 750, may be disposed on different ones of the top and bottom major surfaces in different associated waveguides 670, 680, 690, respectively.

[0087] The waveguides 670. 680, 690 may be spaced apart and separated by, for example, gas, liquid, or solid layers of material. For example, as illustrated, layer 760a may separate waveguides 670 and 680; and layer 760b may separate waveguides 680 and 690. In some embodiments, the layers 760a and 760b are formed of low refractive index materials (that is, materials having a lower refractive index than the material forming the immediately adjacent one of waveguides 670. 680, 690). Preferably, the refractive index of the material forming the layers 760a, 760b is at least 0.05, or at least 0.10, less than the refractive index of the material forming the waveguides 670, 680, 690. Advantageously, the lower refractive index layers 760a, 760b may function as cladding layers that facilitate TIR of light through the waveguides 670, 680, 690 (e.g., TIR between the top and bottom major surfaces of each waveguide). In some embodiments, the layers 760a, 760b are formed of air. While not illustrated, it will be appreciated that the top and bottom of the illustrated set 660 of waveguides may include immediately neighboring cladding layers.

[0088] Preferably, for ease of manufacturing and other considerations, the material forming the waveguides 670, 680, 690 are similar or the same, and the material forming the layers 760a, 760b are similar or the same. In other embodiments, the material forming the waveguides 670, 680, 690 may be different between one or more waveguides, or the material forming the layers 760a, 760b may be different, while still holding to the various refractive index relationships noted above.

[0089] With continued reference to FIG. 9A, light rays 770, 780, 790 are incident on the set 660 of waveguides. Light rays 770, 780, 790 may be injected into the waveguides 670, 680, 690 by one or more image injection devices 360, 370, 380, 390, 400 (e.g., as shown in FIG. 6).

[0090] In some embodiments, the light rays 770. 780, 790 have different properties (e.g., different wavelengths or different ranges of wavelengths), which may correspond to different colors. In some examples. The light rays 770, 780, 790 may have different polarization states. The in-coupling optical elements 700, 710, 720 each re-direct the incident light such that the light propagates through a respective one of the waveguides 670, 680. 690 by TIR.

[0091] For example, in-coupling optical element 700 may be configured to re-direct ray 770, which has a first wavelength or range of wavelengths. Similarly, transmitted ray 780 impinges on and is re-directed by in-coupling optical element 710, which is configured to re-direct light of a second wavelength or range of wavelengths. Likewise, ray 790 is re-directed by in-coupling optical element 720, which is configured to selectively re-direct light of third wavelength or range of wavelengths.

[0092] With continued reference to FIG. 9A, light rays 770, 780, 790 are re-directed so that they propagate through a corresponding waveguide 670, 680, 690; that is, the incoupling optical element 700, 710, 720 of each waveguide re-directs light into that corresponding waveguide 670, 680, 690 to in-couple light into that corresponding waveguide. The light rays 770, 780, 790 are re-directed at angles that cause the light to propagate through the respective waveguide 670, 680, 690 by TIR. The light rays 770, 780, 790 propagate through the respective waveguide 670, 680, 690 by TIR until interacting with the waveguide’s corresponding light distributing elements 730, 740, 750.

[0093] With reference now to FIG. 9B, a perspective view of an example of the plurality of stacked waveguides of FIG. 9A is illustrated. As noted above, the light rays 770, 780, 790, are in-coupled by the in-coupling optical elements 700, 710, 720, respectively, and then propagate by TIR within the waveguides 670, 680, 690, respectively. The light rays 770, 780. 790 then interact with the light distributing elements 730, 740, 750, respectively. The light distributing elements 730, 740, 750 re-direct the light rays 770, 780, 790 so that they propagate towards the out-coupling optical elements 800, 810, and 820, respectively.

[0094] In some embodiments, the light distributing elements 730, 740, 750 are orthogonal pupil expanders (OPEs). In some embodiments, the OPEs both re-direct light to the out-coupling optical elements 800, 810. 820 and, in some examples, also expand the pupil associated with this light by sampling the light rays 770, 780, 790 at many locations across the light distributing elements 730, 740, 750 as they propagate to the out-coupling optical elements. In some embodiments (e.g.. where the exit pupil is already of a desired size), the light distributing elements 730. 740, 750 may be omitted and the in-coupling optical elements 700, 710, 720 may be configured to re-direct light directly to the out- coupling optical elements 800, 810, 820. For example, with reference to FIG. 9A, the light distributing elements 730, 740, 750 may be replaced with out-coupling optical elements 800, 810, 820, respectively. In some embodiments, the out-coupling optical elements 800, 810, 820 are exit pupils (EPs) or exit pupil expanders (EPEs) that re-direct light out of the waveguides and toward a user’s eye 210 (FIG. 7). The OPEs may be configured to increase the dimensions of the eye box in at least one axis and the EPEs may be configured to increase the eye box in an axis crossing (e g., orthogonal to) the axis of the OPEs. For example, each OPE may be configured to redirect a portion of the light striking the OPE to an EPE of the same waveguide, while allowing the remaining portion of the light tocontinue to propagate down the waveguide. Upon impinging on the OPE again, another portion of the remaining light is redirected to the EPE. and the remaining portion of that portion continues to propagate further down the waveguide, and so on. Similarly, upon striking the EPE, a portion of the impinging light is directed out of the waveguide toward the user’s eye, and a remaining portion of the light continues to propagate through the waveguide until it impinges on the EP again, at which time another portion of the impinging light is directed out of the waveguide, and so on. Consequently, a single beam of in-coupled light may be replicated each time a portion of that light is redirected by an OPE or EPE, thereby forming a field of cloned beams of light. In some implementations, the OPE and / or EPE may be configured to modify the respective size(s) of one or more of the beams of light.

[0095] Accordingly, with reference to FIGS. 9A and 9B, in some embodiments, the set 660 of waveguides includes waveguides 670, 680, 690; in-coupling optical elements 700, 710, 720; light distributing elements (e.g., OPEs) 730, 740, 750; and out-coupling optical elements (e.g., EPEs) 800, 810, 820 for each component color. The waveguides 670, 680, 690 may be stacked with an air gap / cladding layer between each one. The in-coupling optical elements 700, 710, 720 each direct incident light (e g., with different in-coupling optical elements receiving light of different wavelengths) into a corresponding waveguide. The light then propagates at angles that enable the light to travel via TIR within the respective waveguide 670. 680, 690. Since TIR only occurs for a certain range of angles, the range of propagation angles of the light rays 770, 780, 790 is limited. The range of angles which support TIR may be thought of in such an example as the angular limits of the field of view which can be displayed by the waveguides 670, 680, 690. In the example shown, light ray 770 (e.g., blue light) is in-coupled by the first in-coupling optical element 700, and then continues to reflect back and forth from the surfaces of the waveguide while traveling down the waveguide, with the light distributing element (e.g., OPE) 730 progressively sampling it to create additional replicated rays which are directed tow ard the out-coupling optical element (e.g., EPE) 800, in a manner described earlier. The light rays 780 and 790 (e.g., green and red light, respectively) pass through the waveguide 670, with light ray 780 impinging on and being in-coupled by in-coupling optical element 710. The light ray 780 then propagates down the waveguide 680 via TIR, proceeding on to its light distributing element (e.g., OPE) 740 and then the out-coupling optical element (e.g., EPE) 810. Finally, light ray 790 (e.g., red light) passes through the waveguides 670. 680 to impinge on the light in-coupling optical element 720 of the waveguide 690. The light in-coupling optical element 720 in-couples the light ray 790 such that the light ray propagates to light distributing element (e.g., OPE) 750 by TIR, and then to the out-coupling optical element (e.g., EPE) 820 by TIR. The out-coupling optical element 820 then finally out- couples the light ray 790 to the user, who also receives the out-coupled light from the other waveguides 670, 680.

[0096] FIG. 9C illustrates a top-down plan view of an example of the plurality of stacked waveguides of FIGS. 9 A and 9B. Such a top-down plan view may also be referred to as a head-on view as seen in the direction of propagation of light toward the in-coupling optical elements. That is, the top-down view is a view of the waveguides in which the incident image light would be normal to the drawing page. As illustrated, the waveguides 670, 680. 690, along with each waveguide's associated light distributing element 730, 740, 750 and associated out-coupling optical element 800, 810, 820, may be vertically aligned. However, as discussed herein, the in-coupling optical elements 700, 710, 720 are not vertically aligned; rather, the in-coupling optical elements may be non-overlapping (e.g., laterally spaced apart as seen in the top-down view). This non-overlapping spatial arrangement may facilitate the injection of light from different sources into different waveguides on a one-to-one basis, thereby allowing a specific light source to be uniquely optically coupled to a specific waveguide. In some embodiments, arrangements including non-overlapping spatially separated in-coupling optical elements may be referred to as a shifted pupil system, and the in-coupling optical elements within these arrangements may correspond to sub-pupils.

[0097] It will be appreciated that the spatially overlapping areas may have lateral overlap of 70% or more, 80% or more, or 90% or more of their areas, as seen in the top- down view. On the other hand, the laterally shifted areas may have less than 30% overlap, less than 20% overlap, or less than 10% overlap of their areas, as seen in top-down view. In some implementations, laterally shifted areas have no overlap.

[0098] FIG. 9D illustrates a top-down plan view of another example of a plurality of stacked waveguides. As illustrated, the waveguides 670. 680, 690 may be vertically aligned. However, in comparison to the configuration of FIG. 9C, separate light distributing elements 730, 740, 750 and associated out-coupling optical elements 800, 810, 820 are omitted. Instead, light distributing elements and out-coupling optical elements are effectively superimposed and occupy the same area as seen in the top-down view. In some implementations, light distributing elements (e.g., OPEs) may be disposed on one major surface of the waveguides 670, 680, 690 and out-coupling optical elements (e.g., EPEs)may be disposed on the other major surface of those waveguides. Thus, each waveguide 670, 680. 690 may have superimposed light distributing and out coupling optical elements, collectively referred to as combined OPE / EPEs 1281, 1282, 1283, respectively. The incoupling optical elements 700, 710, 720 in-couple and direct light to the combined OPE / EPEs 1281, 1282, 1283, respectively. In some implementations, as illustrated, the incoupling optical elements 700, 710. 720 may be laterally shifted (e.g., they are laterally spaced apart as seen in the illustrated top-down view) and have a shifted pupil spatial arrangement. As with the configuration of FIG. 9C, this laterally shifted spatial arrangement facilitates the injection of light of different wavelengths (e.g., from different light sources) into different waveguides on a one-to-one basis.

[0099] As discussed herein, AR systems may display virtual content to a user to augment the user’s view of the real world, that is the physical environment proximal the user. The user of an AR system may also be referred to as the viewer or, in instances where the AR system is a wearable system, the wearer. A wearable display (e.g., AR or VR) maybe worn on the head of the user such that the display is situated in front of one or both of the user’s eyes. In such instances, the wearable display may be referred to as a headmounted display. The physical arrangement of the wearable display, as well as at least some of its features and functions, are the same regardless of whether the display is currently being worn by a user. Accordingly, the term head-mounted display as used herein is understood as synonymous with the term head-mountable display. The virtual content may be displayed on ahead-mounted display, for example, as part of eyewear, that projects image information to the user’s eyes. In addition, where the system is an AR system, the display may also transmit light from a surrounding environment to the user’s eyes, to allow a view of the surrounding environment. As used herein, it will be appreciated that a headmounted or head mountable display is a display that may be mounted on the head of the user or viewer. The display may also be described as anear-eye display, e.g., situated close to the user’s eye(s) when the display device is being worn.

[0100] When using AR devices, the user is able to see both the surrounding, or ambient, environment and also virtual content presented by a display. The display may output image light rearwards toward the user’s eye to display the virtual content. In addition, the display may eject some of this image light forward, toward the surrounding environment and away from the user. For example, image light may be ejected from the display to the user’s eyes using diffractive optical elements, which function symmetrically to also eject image light in an opposite direction, toward the surrounding environment. Thus, another individualwho is looking at the user may undesirably be able to see the content being displayed to the user, or the other individual may see otherwise outputted light that negatively impacts the aesthetic appeal of the outward appearance of the display device. Maintaining the privacy of this displayed content, however, is particularly difficult in AR devices because the AR devices are designed to be transmissive, to let in light from the surrounding environment. Thus, it is not an option to merely block all image light from exiting out into the surrounding environment.

[0101] In some implementations, privacy, aesthetics, and mechanical stability and strength may be improved using a one-way mirror. The one-way mirror is partially reflective, such that light from the surrounding environment is partially reflected back toward the world and partially transmitted to the user. The light reflected toward the surrounding environment may be used to obscure the content of the image light outputted from the display toward the surrounding environment, while the transmission of light through the one-way mirror allows the user to see the surrounding environment. Thus, both privacy and aesthetics may be improved. In addition, by providing an additional structure in front of a display, the mechanical strength of the assembly may be increased, while the one-way mirror may also provide some physical protection for the display.

[0102] In some implementations, the one-way mirror is formed using a polarization selective mirror forward of a polarizer. As used herein, forward (or outward) refers to the relative positions of two structures while the AR device is being worn, with the forward side of the structure being the side in the direction that the one-way mirror is configured to reflect light (e.g., out toward the surrounding environment and away from the user). The rearward (or inward) side of the structure is the side in a direction that the one-way mirror is configured to transmit light (e.g.. toward the user). For example, for a head-mounted display, with a one-way mirror configured to reflect light back into the world, a polarization selective mirror forward of a polarizer is disposed on the world side of the polarizer, with the polarizer being rearward of the polarization selective mirror (or on the user side of the polarization selective mirror). The polarization selective mirror reflects light of one polarization, while transmitting light of another polarization, e.g.. to a user’s eye. The oneway mirror may be provided forward of the display. However, image light may also be ejected from the display to the polarization-selective mirror, which may undesirably reflect the light back to the user's eye and decrease perceived image quality. Advantageously, the polarizer may be utilized to change the polarization of light ejected from the display, such that the light is transmitted through the polarization-selective minor.

[0103] The use of one-way mirrors poses various challenges, which may advantageously be addressed by certain implementations disclosed herein. For example, light generated by objects in the ambient environment may be generated as polarized light, such as light from other display devices including smart phones, watches, televisions, and so forth. Thus, depending on the orientation of the one-mirror relative to the source of that light, the polarized ambient light may not be transmitted through the one-way mirror. As a result, the user may not be able to see objects in the ambient environment that output, or are otherwise made visible by, polarized light. To enable the user to see such polarized light, in some implementations a depolarizer may be provided, e.g., as part of the one-way mirror and / or forward of the polarization-selective mirror. In some implementations, the depolarizer randomizes the polarization of incoming light, e.g.. converting light of one polarization into light of two different polarizations, one of which is reflected by the polarization-selective mirror and one of which is transmitted through the polarization- selective mirror and the polarizer, thereby allowing a user to receive the transmitted polarized light and to perceive content provided by that polarized light or otherwise see objects illuminated by polarized light. The depolanzer changes the polarization of light that is incident on and transmitted through it, so that any changes of the polarization of the incident light are not perceivable by human vision, even when polarizing elements such as polarizers are applied to filter the transmitted light.

[0104] In some implementations, the presence of the polarizer rearward of the polarization selective mirror allows for the formation of compact integrated structures with additional optical functionality. For example, the polarizer may be used in conjunction with an actively variable dimmer formed using a rearward array of liquid crystal elements and an additional rearw ard polarizer. The variable dimmer allows the transmission of light from the ambient environment to be modulated, e.g., to facilitate the presentation of virtual content by the display device by blocking ambient light that may overlap spatially with the virtual content.

[0105] In some embodiments, the polarization-selective mirror and the polarizer of the one-way minor are aligned such that the light (e.g., image light from the display) converted by the polarizer is transmitted through the one-way mirror towards the ambient environment, and vice versa. Proper alignment of the polarization-selective mirror and the polarizer, however, may be challenging, e.g., in implementations where the polarization selective mirror is spaced apart from the polarizer by a gap. e.g., an air gap of 1 mm or more. An alignment error between the transmission axes of the polarization-selectivemirror and the polarizer may lead to un-desired reflection of the display light from the polarization-selective mirror back to the user, which may degrade visual qualities of displays (e.g., cause duplicated images of display contents with perceivable mismatches between images). In such cases, because the polarization selective mirror and the polarizer are not directly attached to one another, misalignments may occur during manufacture and / or may develop over time in the course of using the device. In some implementations, the alignment tolerances between the polarization-selective mirror and the polarizer may be increased using optical retarders attached to the polarization-selective mirror and the polarizer, respectively. The optical retarders may be configured to convert linear polarization to circular polarization. In some implementations, the optical retarders may be quarter-wave plates. In some implementations, these retarders may also be designed to operate over the visible wavelength spectrum. A first retarder converts light passing through the polarization-selective mirror into circularly polarized light, which propagates to a second retarder that converts the circularly polarized light into linearly polarized light for propagation through the polarizer. A similar conversion of linearly polarized light to circularly applied light and back to linearly polarized light occurs for light traveling in the opposite direction, from the display out towards the ambient environment. In some embodiments, the first retarder is attached or laminated to the polarization selective mirror and the second retarder is attached or laminated to the polarizer rearward of the polarization selective mirror. Because the light propagating between the first and second retarders is circularly polarized, the one-way mirror is relatively insensitive to the relative orientations of the first and second retarders, thereby increasing alignment tolerances. In addition, as discussed herein, the second retarder may advantageously reduce the reflection of image light back to the user due to Fresnel reflections off surfaces forward of the second retarder.

[0106] In some implementations, the polarization selective mirror may be a cholesteric liquid crystal reflective polarizer. Such a polarization selective mirror advantageously provides for a compact one-way mirror, with large alignment tolerances. For example, a cholesteric liquid crystal reflective polarizer may convert linearly polarized light from the ambient environment into circularly polarized light, thereby providing large alignment tolerances with rearward polarizers, as discussed above. This may be achieved without need of first and second retarders, as described above, which may thereby allow the formation of a highly compact one-way mirror. In some other implementations, the polarization selective mirror may be a wire-grid polarizer, which may comprise an array ofnano-wires of metallic materials such as aluminum, or a multi-layer polarizer, which may comprise alternating layers of anisotropic films such as stretched polymer films.

[0107] Implementations disclosed herein may provide various advantages, as discussed herein. For example, the one-way mirror may increase the aesthetic appeal of the display system by providing an appearance more closely resembling eyewear, such as sunglasses. In addition, by providing a separate structure forward of a display, the one-way mirror may increase the mechanical strength of the display and also shields and protects parts of the display providing image content to the user. In addition, the one-way mirror may hide complex functional components in the display, thereby further increasing the aesthetic appeal of the display system. Further, as discussed herein, privacy may be increased by reducing the visibility of image light that is output towards the ambient environment.

[0108] FIG. 10 is a diagram showing an example arrangement of physical and / or optical elements in a wearable display system, such as a head-mountable AR system. The arrangement of physical and / or optical elements may also be described as the VOA discussed above, and may include various sections that provide various functions such as dimming, optical artifact mitigation, eye illumination (e.g., for eye imaging and / or tracking), physical protection of the optical elements, and so forth. The arrangement 1000 may include any suitable number of physical and / or optical elements, arranged in layers as shown, to provide various technical effects as described further here. The arrangement 1000 may be mounted to a frame (not shown) of the wearable display device such as that shown in the example of FIG. 2. The arrangement 1000 may be mounted so that the elements included in the arrangement 1000 are situated in front of one or both eyes 210 of the user while the wearable display system is being worn.

[0109] As shown in FIG. 10, the arrangement 1000 can include any suitable number of sections that each provide various functional elements for altering light that is travelling inward through the arrangement toward the eye 210 or outward through the arrangement toward the world. In this example, the arrangement 1000 includes: section 1010, referred to as the rear carrier; section 1020. referred to as the eyepiece; section 1030, referred to as the front carrier; and section 1040, referred to as the cosmetic window. In some embodiments, the arrangement 1000 may also provide for the use of an optional prescription lens insert 1008. This insert 1008 may provide a layer that is closest to the eye(s) 210, in some embodiments, and may be a lens that is configured according to a prescription of the user, i.e., a corrective lens to adjust incoming light based on the user's particular prescription to correct for myopia (near-sightedness), hyperopia or presbyopia(far-sightedness), and / or other conditions. The arrangement 1000 may include two EDOF refractive lenses 1002 and 1004 separated by some distance and / or by other layers within the arrangement 1000. These EDOF refractive lenses are also referred to as EDOF lenses, and are discussed in further detail herein.

[0110] In some embodiments, the rear carrier section 1010 includes a first EDOF 1002. This EDOF 1002 may be the layer closest to the eye(s) 210 (apart from the prescription insert 1008 if it is in use). The rear carrier section 1010 may also include an illumination layer 1006. The illumination layer 1006 may be configured to illuminate the eye(s) 210 with light of a suitable wavelength range, for example infrared light. The light provided by the illumination layer 1006 may reflect off the surface of the eye(s) 210 and be detected by one or more sensors (e.g.. cameras) not shown here. The reflected light may be detected and analyzed for various purposes. For example, the light reflecting of the eye(s) 210 (e.g., in one or more glints) may be analyzed to determine a pose of the eye, a direction in which the eye is looking. The reflected light may also be analyzed to determine a current shape of the lens of the eye(s) 210 and thus determine a current accommodation of the eye(s), a depth at which the eye(s) are focused. The illumination layer 1006 may be composed of any suitable number of materials and any suitable type(s) of material. In some embodiments, the illumination layer 1006 comprises polyethylene terephthalate (PET).

[0111] The eyepiece section 1020. also referred to as the eyepiece, may include any suitable number of waveguide layers 1014. In the example shown, the arrangement 1000 includes three waveguide layers 1014(1), 1014(2), and 1014(3). Each waveguide may be configured to in-couple light generated by a projection system (e.g., light that presents computer-generated virtual objects or other virtual content), convey the in-coupled light through TIR within the waveguide, and out-couple the light from the waveguide such that the light is transmitted toward the user’s eye(s) 210. As discussed previously herein, the in-coupling and out-coupling may be accomplished through use of diffractive element(s) (e.g., grating(s)) arranged on or in the waveguide. A waveguide may also include diffractive element(s) such as grating(s) that function to multiply the light as it is being conveyed through the waveguide, such as the OPEs discussed herein. Each waveguide layer 1014 may include a single waveguide, or a stack of multiple waveguides, as described herein. In some examples, the different waveguide layers 1014 may be configured to convey light of different wavelength ranges, e.g., different colors. For example, the waveguide layer 1014(1) may convey green light, the waveguide layer 1014(2) may convey red light, and the waveguide layer 1014(3) may convey blue light. It will be readilyunderstood that green light, red light, or blue light includes light of a particular wavelength range that is perceivable by the human visual system as being green, red. or blue respectively. In some examples, a single waveguide layer 1014 may be configured to convey light of at least two different colors. For example, a single waveguide layer 1014 may convey both red and green light.

[0112] In some embodiments, the eyepiece section 1020 also includes one or more cover layers 1012 on one side or either side of the waveguide layers 1014. In the example shown, a cover layer 1012(1) is provided on the inward side (eye side) of the waveguide layers 1014, and a cover layer 1012(2) is provided on the outward side (world side) of the waveguide layers 1014. The cover layer(s) 1012 may be composed of any suitable, and preferably transparent, material that does not alter the light passing through, or that minimally alters the light passing through. For example, the cover layer(s) 1012 may be composed of a glass. The cover layer(s) 1012 may be included in the arrangement 1000 to protect the waveguide layer(s) 1014 from physical damage, and / or provide further mechanical stability to the arrangement 1000.

[0113] The front carrier section 1030 can include a plurality of layers which, individually and / or in combination with one another, alter the light passing inward and / or outward through the section. In some embodiments, the front carrier section 1030 may include layers that provide for dimming of the light travelling inw ard, e.g., either selective dimming and / or overall dimming. In the example shown, the front carrier section 1030 includes, from the inward side to the outside side: layer 1022, layer 1024(1 ), layer 1026, layer 1024(2), layer 1016(1), layer 1024(3), layer 1018, layer 1024(4), layer 1016(2), layer 1024(5), and layer 1004. Layer 1004 is the second EDOF lens, which operates in conjunction with EDOF lens 1002 as described further herein.

[0114] Layer 1022 is a high contrast linear polanzer (HCLP). The HCLP operates to reduce or prevent the leakage of light toward the user in instances when the other dimming components of the front carrier section may operate to block or dim such light, as described below.

[0115] Layers 1024(1), 1024(2), 1024(3), 1024(4), and 1024(5) are quarter wave plate (QWP) layers that alter the polarization state of light passing through the layers, to convert linearly polarized light to circularly polarized light and to convert circularly polarized light to linearly polarized light. These layers may be of any suitable thickness and may be composed of any suitable material.

[0116] Layer 1026 is a liquid crystal (LC) panel. Layers 1016(1) and 1016(2) are absorptive polarizers. The LC panel layer 1026, between QWP layers 1024(1) and 1024(2) and with the absorptive polarizer layer 1016(1) arranged on the world side of the LC panel layer 1026, operates as a selective dimmer apparatus that is able to selectively and variably dim certain portions of the display. This dimming effect is controllable by an electric input (e.g., voltage) provided to the LC elements (e.g., molecules) of the LC panel 1026, to selectively switch one or more of the LC elements between a transmission mode and an attenuation mode. This provides a mechanism by which the brightness of each pixel in the display is controlled dynamically. For example, a portion of the display that corresponds to a particularly bright light source in the physical environment may be selectively dimmed to avoid the introduction of optical artifacts that may be caused by such a point of brightness.

[0117] The LC panel layer 1026 operates as a selective dimmer to selectively dim (i.e., attenuate) light at selected portions of the FOV, to reduce the intensity of the light propagating inward to the user’s eye at the selected portions of the FOV. The LC panel layer 1026 includes a layer of LC elements (e.g., molecules) sandwiched between two electrode layers of electrodes arranged to provide a voltage across the layer of LC elements at selected locations. In some embodiments, the electrode layers are arranged between an outer polarizer and an inner polarizer. The outer and inner polarizers may be configured to linearly polarize unpolarized light that passes therethrough. In some embodiments, the assembly includes an outer substrate layer positioned between the outer polarizer and the outer electrode layer, and an inner substrate layer positioned between the inner polarizer and the inner electrode layer. Substrate layers may also be present to support the electrode layers, and can be formed from an optically transparent material, such as a glass or plastic. The assembly can also include an outer optical retarder (e.g., an A-plate) positioned between the outer polarizer and the outer electrode layer, and an inner optical retarder (e.g., an A-plate) positioned between the inner polarizer and the inner electrode layer. Such selective dimming may be advantageous to mitigate or prevent optical artifacts such as ghost images that may be created by stray light in the assembly. The assembly may include other suitable elements and / or arrangements of elements to provide selective dimming functionality, as described further in U.S. Patent No. 11,169,380 B2 titled “Ghost Image Mitigation in See-Through Displays with Pixel Arrays,’’ granted on November 9, 2021, the entire contents of which are hereby incorporated by reference into the present disclosure.

[0118] Layer 1018 is a C-plate retarder. In some embodiments, the C-plate retarder of layer 1018 is positioned between QWPs, such as layers 1024(3) and 1024(4) in the example shown. This combination can operate as an angle attenuator apparatus that prevents or mitigates high-angle of incidence light from passing through the polarizers (e.g., QWP layers 1024(1) and 1024(2)) on either side of the LC panel of layer 1026 and into the user’s eye through the waveguide stack 1020. In this way, the occurrence of rainbow artifacts caused by front light sources in the world can be reduced or eliminated. The assembly may include other suitable elements and / or arrangements of elements to manage ambient light and mitigate or prevent artifacts, as described further in U.S. Patent No. 11,561,401 B2 titled “Ambient Light Management Systems and Methods for Wearable Devices,” granted on January 24, 2023, the entire contents of which are hereby incorporated by reference into the present disclosure.

[0119] The cosmetic window section 1040 can include a plurality of layers which, individually and / or in combination with one another, alter the light passing inward and / or outward through the section. In some embodiments, the cosmetic window section 1040 may include layers that provide a one-way mirror that reflects a portion of the light travelling inward from the physical world, e.g., to provide additional privacy and obscure the virtual content being shown to the user through the display device.

[0120] The cosmetic window section 1040 can include, from the inward side to the outward side: a QWP layer 1024(6), a reflective polarizer layer 1028, a depolarizer layer 1036, and a base substrate layer 1032. In some embodiments, the C-plate layer 1018 may be part of the section 1040 instead of section 1030, and may be provided immediately inward of the QWP layer 1024(6). In some embodiments, the cosmetic window uses a reflective (e.g.. white) polarizer (e.g., layer 1028) which, when combined with a retarding film or layer (e.g., QWP layer 1024(6)), allows users to view- displays, monitors, or other light sources that output polarized light, such as LCD monitors, while the reflection from the reflective polarizer prevents the presented virtual content from being visible to external persons in the world who may be looking at the user who is wearing the AR device.

[0121] The reflective polarizer layer 1028 may also be described as a polarization selective mirror that reflects incident light having a particular polarization and transmits light that has another polarization. In some implementations, the reflective polarizer layer 1028 is a wire-grid polarizer configured to reflect linearly polarized light. For example, the wire-grid polarizer may include a nano-scale wire pattern with repeating parallel wires.The wires of the wire pattern may be elongated perpendicular to the transmission axis of the reflective polarizer layer 1028.

[0122] In some implementations, the reflective polarizer layer 1028 may be a multilayer polarizer. The multi-layer polarizer may be configured to reflect incident light of a pre-determined wavelength. For example, the pre-determined wavelength may include wavelengths corresponding to different colors. In some implementations, the multilayer polarizer may include a plurality of polymer thin films that have been extruded and stretched along an axis, which may provide differences in refractive indices along the stretch axis and the transverse axis. Advantageously, the multi-layer polarizer may allow for customization of the color of the one-way mirror, thereby providing the ability to provide display systems of a variety of different colors, just as sunglasses may be provided in different tints. This may improve the cosmetic appeal of the display system. For example, the different colors may be provided by use of a multi-layer polarizer that reflects light of a predetermined wavelength (corresponding to a desired color). In addition, while reflecting light of certain wavelengths, the color point of world light reaching the user’s eye 214 may not be affected as the transmitted light will be determined by the absorptive polarizer 208, which may be configured to alter the color point by preferentially transmitting some wavelengths of light. Further, it will be appreciated that multi-layer polarizers may have different reflectivity. The multi-layer polarizer may advantageously be configured to provide a tailored amount of privacy based on the amount of light reflected; for example, multi-layer polarizers with higher reflectivity may be utilized for higher privacy and multi-layer polarizers with lower reflectivity may be utilized when privacy requirements are lower.

[0123] In some implementations, the reflective polarizer layer 1028 may be a reflective circular polarizer such as a cholesteric liquid crystal reflective polarizer. Use of such a cholesteric liquid crystal polarizer may provide one or more advantages. The cholesteric liquid crystal polarizer may be substantially insensitive to the angular orientation of incident circularly polarized light and therefore may not need to be oriented with a specific transmission axis alignment relative to the absorptive polarizer(s) provide in other layers of the arrangement 1000. Further, use of such a polarizer provides for a one-way mirror that reflects light with a circular polarization and transmits light with an opposite circular polarization. By providing reflected light with a circular polarization, other individuals wearing linear polarizers such as some sunglasses are prevented from filtering out the reflected light and seeing the projected virtual image light that is escaping into the world.In addition, advantageously, the tint color of the one-way mirror may be adjusted by adjusting the composition of the cholesteric liquid crystal within the cholesteric liquid crystal polarizer. By adjusting the composition, the polarizer may be configured to reflect predetermined wavelengths of light, thereby impacting the external appearance of the display system utilizing the one-way mirror. In addition, while the cholesteric liquid crystal polarizer may transmit less of some wavelengths of light, the color point of world light reaching the eye(s) 210 would not be affected as the user’s view of the world is determined by the absorptive polarizer(s), which may be configured to alter the color point by preferentially transmitting some wavelengths of light. Further, the reflectivity' of the cholesteric liquid crystal polarizer may be adjusted based on the thickness of the cholesteric liquid cry stal polarizer. In some implementations, the cholesteric liquid crystal polarizer may reflect up to 50% of the world light, e.g., 30-50% or 40-50% of the world light. In some implementations, the cholesteric liquid cry stal polarizer may reflect 20-70%, 30-70% 30-60%, or 40-60% of the incident world light. In this way, by tailoring the amount of light reflected, the cholesteric liquid crystal polarizer may tailor the level of privacy provided.

[0124] In some implementations, the depolarizer layer 1030 may be a QWP such as an achromatic quarter waveplate (AQWP). In some implementations, the depolarizer layer may be a super retarder or one or more layers of material having high retardation values. In some implementations, the depolarizer layer may be a retarder with random optical axis orientations. In some implementations, the depolarizer layer may be configured to convert a portion of polarized light from the outside world to circularly polarized light. In situations where the world light is polarized, the depolarizer layer may convert a portion of the polarized world light into light that is right-hand circularly polarized and / or left-hand circularly polarized before the light reaches reflective polarizer layer 1028, which may also be referred to as a polarization selective mirror. Whether the light output by the depolarizer layer is randomly, linearly, or circularly polarized, a portion of the light output by the depolarizer layer is of a polarization such that that portion of the light is transmitted through the reflective polarizer layer 1028. In some embodiments. 20-70%, 30-70% 30-60%, or 40-60% of the light outputted by the depolarizer layer has a linear component aligned with the transmission axis of the reflective polarizer layer 1028, so as to be transmitted through reflective polarizer layer 1028. In some implementations, the light which is reflected off the reflective polarizer layer 1028 may have a linear polarization, and the depolarizer layer may convert this light into circularly polarized light before it passes out of the arrangement 1000.

[0125] The base substrate layer 1032 may be a protective layer provided to prevent physical damage and / or degradation to other layers of the cosmetic window section 1040. The base substrate layer 1032 may be composed of any suitable material, such as glass.

[0126] Although the layers of the cosmetic window section 1040 are shown as planar in FIG. 10, embodiments are not so limited. In some embodiments, one or more layers of the section 1040 may be configured with a suitable non-planar shape, e.g., curved.

[0127] In the example arrangement 1000 shown, certain consecutive layers are shown separate by a gap (e g., an air gap) and certain layers are shown as immediately adjacent to each other without a separating gap. The supported embodiments are not limited to the example shown. In some instances, a gap of any suitable width may be provided between layers, or layers may be immediately adjacent and / or in physical contact with one another without an intervening gap, to provide the desired technical operation and / or technical advantages of the display device. The arrangement 1000 may also include additional layers of any suitable configuration in addition to those shown, and / or may omit one or more of the illustrated layers, to achieve the desired effect(s).

[0128] The example of FIG. 10 shows frame elements 1034(1), 1034(2), 1034(3), and 1034(4) between different sections. Such frame elements may provide mechanical stability to the arrangement 1000, e.g., to ensure that the various elements of the arrangement maintain their position relative to one another and relative to the user. Where there is a gap between layers, the frame elements may ensure that the gap remains present over time and maintains the desired gap width. Though not shown in FIG. 10 for the sake of clarity, the frame element(s) may include component(s) that extend along one or more sides of the arrangement 1000, in addition to providing a physical separation between sections as shown. The frame element(s) 1034(1), 1034(2), 1034(3), and 1034(4) may be arranged with any suitable configuration, and may be composed of any suitable material.

[0129] The example arrangement shown in FIG. 10 is not limiting of embodiments that are supported by this disclosure. One of more of the lay ers shown may be omitted from the VOA. in some embodiments. Also, additional layers may be incorporated into the VOA other than those shown, layers of any suitable type and function. The arrangement 1000 shown in FIG. 10, and variants thereof according to embodiments, may also be described as an integrated structure in which one or more components of the structure may each serve multiple purposes. For example, one of the layers that is included in the selective dimming apparatus described above may also be included in the structure that blocks or mitigates high angle of incidence light, as also described above. In this way, the arrangement 1000may be configured to be as compact as possible while still providing the desired functionality. Such compactness is particularly advantageous in a wearable device to minimize the weight and size of the wearable device and thereby provide a positive user experience. Such compactness also reduces cost and provides for faster and more efficient manufacture of the wearable device.

[0130] FIG. 11 illustrates a cross-sectional side view of several examples of EDOF lenses that may be used in an AR display device or other type of optical device. Although the examples shown are convex lenses that may impart positive optical power to light entering the lens (e.g., from the top of the page), the lenses may also include concave lenses having negative optical power.

[0131] Lens 1100 is a conventional lens with substantially continuous curvature across the surface of the lens, e.g., a spherical lens, aspherical lens, and so forth. The maximum thickness (width) of the lens is shown as thickness 1106.

[0132] Lens 1102 is an example of a Fresnel lens. In a Fresnel lens, the lens surface is divided into at least two (e.g., concentric) annular regions arranged radially from a center 1118 of the lens. The lens curvature in each region may be similar to the surface curvature of a conventional lens (e.g., lens 1100) at a corresponding distance from the center of the lens. However, in aFresnel lens, different adjacent regions are separated by a discontinuity, such as discontinuity 1112 as shown in this example. This discontinuity is also described as a groove or ridge. This configuration enables the lens to provide similar optical power as a conventional lens (e g., lens 1 100), but with a maximum thickness 1 108 that is less than the thickness 1106 of a traditional lens. Lens 1102 is an example of a Fresnel lens in which the height of the discontinuities is the same or approximately the same maximum thickness 1108, and which may also be the same as the thickness of the center region of the lens. This is referred to as a Fresnel lens with a constant (or substantially constant) ridge or discontinuity height.

[0133] Alternatively, a Fresnel lens can have a varying discontinuity height across its surface, as shown by the example lens 1104. In this example, the height of the discontinuities 1114 varies with distance from the center 1120 of the lens. In this example, the discontinuity height increases as the distance from the center of the lens increases. The maximum thickness 1110 of the lens 1104 is less than the maximum thickness 1106 of the convention lens 1100. In lens 1104, the discontinuity height varies while the ridge width 1116 remains substantially constant from ridge to ridge, where ridge width 1116 is defined as the distance between the maxima of adjacent discontinuities, as shown in the example.Accordingly, such a lens is referred to as a Fresnel lens with a constant (or substantially constant) ridge or discontinuity width.

[0134] Fresnel lenses are thin lenses that allow for a large lens aperture while being more compact, with reduced thickness, compared to conventional refractive lenses having similar optical power. The use of Fresnel lenses instead of conventional lenses reduces the material volume needed in a device, relative to using conventional refractive lenses of similar optical power. The optical power of the Fresnel lens across its aperture is accomplished by dividing the lens into concentric regions as discussed above. The discontinuities of a Fresnel lens can be described by specifying discontinuities (grooves) per unit length, which can be constant (e.g., with vary ing heights as in lens 1104) or varying (e.g., with consistent heights as in lens 1102).

[0135] The lenses can be made of any suitable material. In some embodiments, the lenses are made of a suitable polymer having a refractive index of at least 1.5. In some embodiments, the lenses can be made of a suitable glass having a refractive index of at least 1.45. The maximum thickness of the Fresnel lenses employed as EDOF lenses may be any suitable thickness, for example approximately 100 microns (pm) or less.

[0136] The use of Fresnel lenses as EDOF lenses in a display device causes some disadvantages compared to the use of conventional refractive lenses. In particular, the presence of the discontinuities in the Fresnel lens causes a scattering of the light that can lead to a haze effect and / or aberrations perceivable by a user of the optical device in which the lens is employed. Accordingly, the use of a Fresnel lens alone as an EDOF lens of an AR display device can lead to images that are hazy7and / or with aberrations that detract from the user’s experience when viewing real world objects and / or virtual image data.

[0137] To address such disadvantages, in some embodiments one or both of the EDOF lenses is a Fresnel lens that has been modified with a conformal coating across at least a portion of its surface, and / or is embedded in some suitable material.

[0138] FIG. 12 illustrates a cross-sectional side view of example EDOF lenses with a coating and / or embedding material, for use in an AR display device or other type of optical device. Although the examples shown are convex lenses that may impart positive optical power to light entering the lens (e g., from the top of the page), the lenses may also include concave lenses having negative optical power.

[0139] Lens 1202 is an example of a Fresnel lens in which the base material 1204 of the lens has been coated with a coating 1206 that conforms to the surface of the lens across its discontinuous surface. Lens 1208 is an example of a Fresnel lens in which the base material1204 of the lens has been coated with the conformal coating 1206, and the base material 1204 and coating 1206 are also embedded (wholly or in part) in an embedding material 1210. These examples show coating and / or embedding of a constant height Fresnel lens, but similar treatment(s) may also be applied to a Fresnel lens of constant width and varying height.

[0140] Adding a coating that conforms to the surface of the lens can provide significant reduction in haze and improvement in image quality with reduced optical power, compared to lenses without such a coating. For example, the lens can be coated with a Silicon Dioxide (SiCh) coating, and / or another suitable ty pe of hard and / or anti -reflective coating. The refractive index of the SiOi material used in the coating is 1.45, and in general the material used in the coating may have a lower refractive index than the refractive index (e.g., approximately 1.5 to 1.6) of the polymer or glass used to make the lens. Various suitable techniques can be used to apply the (e.g., SiCh) coating to the lens surface, including physical vapor deposition (PVD) processes (e.g., sputter, evaporation, etc.) and chemical vapor deposition (CVD) processes such as Plasma Enhanced Low Pressure CVD, Atomic Layer Deposition, Atmospheric Plasma CVD, and so forth. Use of such a coating to reduce reflection and haze provides an improved viewing experience for the user.

[0141] Use of the embedding material 1210 can also provide further reduction in haze and improved image sharpness. Embodiments support the use of the coating, the embedding, or both coating and embedding to improve optical performance of the Fresnel lenses used as EDOF lenses. The coating material (e.g., SiOz) can also act as ahard coating for the lens and a surface for adhesion of the embedding material to the conformally coated surface of the lens. The embedding (also described as laminating) material may be any suitable material. For example, the embedding material may be an ultraviolet (UV) or thermally curable material. In some embodiments, the embedding material 1210 is an adhesive material with refractive index between about 1.1 and about 1.7. In one example, the embedding material 1210 is a Norland™ Optical Adhesive with refractive index of 1.315. Selection of the particular embedding material may further depend on the power of the lens being embedded and / or the index of the substrate and / or lens. In some embodiments, the embedding material is a planarizing structure that creates a substantially flat surface for both sides of the lens, making it easier to assemble (stack) into the VOA arrangement described above, or other ty pe of optical stack of optical elements.

[0142] In some embodiments, the embedding material is a laminating material that has a refractive index different from that of the material that forms the compact lens beingembedded (e.g., a Fresnel lens or flatened periphery' lens). The minimum thickness of the embedded (e.g., laminated, encapsulated) lens may depend on the maximum ridge or groove height of the Fresnel lens in the area to be embedded or the maximum thickness of the flatened periphery lens.

[0143] Embedding the lens causes a reduction in haze and improved image quality7, but with a reduction in the optical power of the lens. Measurements showed that using a SiCh coating over a 25 pm ridge height Fresnel lens and the lens being embedded between two flat surfaces significantly reduced haze and improved image quality, but with reduced optical power. Accordingly, in some embodiments the power of the lens is increased to achieve the desired final power, prior to the coating and / or embedding of the lens. For example, groove height can be increased to provide a higher optical power for the lens. Other techniques may also be used to achieve the desired optical power for the lens, for example by varying the refractive index of the lens material and / or the refractive index of the laminating material that the lens is being embedded into, for a given lens geometry7and material.

[0144] Although FIG. 12 shows an example of a compact lens that is a Fresnel lens that has been coated and / or embedded, embodiments are not so limited. The compact lens may also be a flatened periphery7lens as discussed herein, which may be embedded and / or coated similarly to achieve the desired optical performance and / or physical configuration.

[0145] Table 1 below shows improvements in lens performance with use of the coating and / or embedding.Table 1

[0146] In Table 1, the first column is a name of a sample component being tested, and the second through fourth columns represent measurements of the lightness of colors being viewed through the component. The fifth column is a measurement of the amount of haze visible through the component, and the sixth column is a measurement of optical power in diopters. As shown by the table, the use of embedding reduces the amount of haze, whiledecreasing the optical power of the lens. In some embodiments, the material that forms the compact lens and / or the optical power of the compact lens can be selected such that embedding the lens in an embedding material of a particularly selected refractive index results in a desired overall optical power for the embedded compact lens.

[0147] Table 2 below shows improvements in lens performance with use of the coating and / or embedding.Table 2

[0148] In Table 2, the first column is a name of a sample component being tested, and the second through fourth columns represent measurements of the lightness of colors being viewed through the component. The fifth column in Table 2 is a measurement of the amount of haze visible through the component. As shown, use of either coating or embedding reduces the amount of haze, and haze is minimized by using both coating and embedding.

[0149] FIGS. 13 A, 13B, 13C, and 13D illustrate example arrangements of EDOF lenses providing optical power in one or more regions of the lens. In some embodiments, each EDOF lens is divided into regions, and the lens may have a different optical power in different regions, e.g., analogous to a bifocal or trifocal lens arrangement.

[0150] FIG. 13A shows an example in which each EDOF lens, including the eye-side EDOF lens 1002 and the world-side EDOF lens 1004, has a single region across its aperture. The eye-side lens 1002 may have a single region 1302(1) with a (e.g., negative) optical power that is substantially the same across most or all of the aperture. The worldside lens 1004 may have a single region 1302(2) with a (e.g., positive) optical power that is substantially the same across most or all of the aperture. The power of the eye-side lens1002 may be substantially equal to, and opposite to, the power of the world-side lens 1004, to ensure that the real-world objects being viewed are not being depth-adjusted while the projected virtual content is being depth-adjusted, as discussed above.

[0151] In some embodiments, as shown in the examples of FIGS. 13A-13D, the eyeside lens 1002 is smaller in at least one dimension, e.g., spans a smaller portion of the user’s FOV. than the world-side lens 1004. Given that the lens 1002 is closer to the eye(s) than the lens 1004, a larger size lens 1004 can ensure that the lens 1004 spans an angular FOV at least as large as that spanned by the lens 1002, e.g., to ensure than any world light passing through the lens 1002 has already passed through the lens 1004. In the example shown, the lens 1002 is smaller than the lens 1004 in both width and height, e.g., in both the X- and Y-dimensions where the Z-direction is along an optical axis that extends outward from the user’s eye through the components of the VOA to the world (e.g., approximately perpendicular to the various layers of the VOA).

[0152] FIG. 13B shows an example of a "bifocal" arrangement, in which each of the lenses 1002 and 1004 are divided into two regions, with lens 1002 divided into regions 1304(1) and 1306(1), and lens 1004 divided into regions 1304(2) and 1306(2). As shown in this example, the (e g., top) regions 1304(1) and 1304(2) may have substantially equal and opposite optical power, and the (e.g., bottom) regions 1306(1) and 1306(2) may have substantially equal and opposite optical power. As shown in this example, the optical power of the bottom regions is greater than the optical power of the top regions. Using such an arrangement, the display system can selectively display virtual objects in a particular region, and the lens 1002 will alter the perceived depth of the object(s) depending on what region they are displayed in. In this example, virtual objects projected through the bottom region appear to be closer than virtual objects projected through the top region. Alternatively, the lenses may be arranged such that the top regions have the higher optical power, so that virtual objects shown in the top region appear closer than virtual objects show n in the bottom region.

[0153] FIG. 13C shows an example of a ‘“trifocal” arrangement, in which each of the lenses 1002 and 1004 are divided into three regions, with lens 1002 divided into regions 1308(1), 13010(1), and 1312(1), and lens 1004 divided into regions 1308(2), 1310(2), and 1312(2). As shown in this example, the (e.g., top) regions 1308(1) and 1308(2) may have substantially equal and opposite optical power, the (e.g., middle) regions 1310(1) and 1310(2) may have substantially equal and opposite optical power, and the (e.g., bottom) regions 1312(1) and 1312(2) may have substantially equal and opposite optical power. Asshown in this example, the optical power of the bottom regions is greater than the optical power of the middle regions, and the optical power of the middle regions is greater than the optical power of the top regions. Using such an arrangement, the display system can selectively display virtual objects in a particular region, and the lens 1002 will alter the perceived depth of the object(s) depending on what region they are displayed in. In this example, virtual objects projected through the bottom region appear to be closer than virtual objects projected through the middle region, which themselves appear to be closer than virtual objects projected through the top region. Alternatively, the lenses may be arranged such that the top regions have the higher optical power, so that virtual objects shown in the top region appear closer than virtual objects shown in the middle region, which themselves appear closer than virtual objects shown in the bottom region.

[0154] Embodiments support the use of any suitable number of regions of any suitable configuration in the EDOF lenses, with each region having any suitable pow er to alter the focal depth of virtual objects projected to the user’s eye(s) through each region. Moreover, although the boundaries dividing the regions are shown to be straight lines in the examples of FIGS. 13B and 13C, embodiments are not limited to linear boundaries in this way. In some embodiments, the boundaries dividing regions from one another may be curved boundaries, or segmented (e.g., spline) boundaries made up of any suitable number of connected linear segments. In some embodiments, these regions may be a single continuous freeform surface with a smooth transition boundary region. In some embodiments, a region may also be surrounded by another region. For example, a first (high power or low' power) region may be near the center of the lens aperture, and may be surrounded by a second (lower power or higher power) region, which itself may be surrounded by a third region and so forth, in concentric rings or some other suitable configuration.

[0155] FIG. 13D shows an example of a progressive arrangement, in which the optical pow er of each lens varies across its aperture, e.g., that may change from location to location in the aperture of the lens. In this example, lens 1002 includes a region 1314(1) in which the (e.g., negative) optical power varies from top to bottom, such that the power at the top is lower than the pow er at the bottom, and such that the power progressively increases from top to bottom. Stated somewhat differently, the optical powder increases with the distance from the top of the lens. Lens 1004 includes a region 1314(2) in which the (e.g., positive) optical power similarly varies. The lenses 1002 and 1004 may have approximately equal and opposite optical power at a point in each lens that corresponds to a same angularlocation within the user’s FOV. Using such an arrangement, the display system can selectively display virtual objects at a particular location in the aperture, and the lens 1002 will alter the perceived depth of the object(s) depending on the location(s) they are displayed in. For example, objects presented toward the bottom of the user’s FOV can appear to be closer than objects presented toward the top of the user’s FOV. Although this example shows a progressive increase in optical power from top to bottom, embodiments are not limited to this particular example. In some embodiments, the optical power may progressively increase from bottom to top, from left side to right side, from right side to left side, diagonally from comer to comer across the aperture, and / or in other suitable arrangements.

[0156] Other suitable arrangements may be supported by embodiments, in which different locations within the aperture of the lenses (e.g., with the FOV) may have different optical power, and in which corresponding locations in the eye-side lens 1002 and worldside lens 1004 have substantially equal and opposite optical power to neutralize the world light and ensure that it appears to the user with minimal or no change in the real-world depth of real -world objects. Such EDOF lenses in which the lenses have different optical power in different regions or locations within the aperture may be described as multi-focal EDOF lenses.

[0157] FIGS. 14A and 14B illustrate a cross-sectional side view of example EDOF lenses providing optical power in one or more regions of the lens, e.g.. in which different regions or locations in the lens aperture have different optical power, as discussed with regard to FIGS. 13A-13D.

[0158] FIG. 14A shows an example of an eye-side EDOF lens 1002 and a world-side EDOF lens 1004, configured to provide a 'bifocal" arrangement in which two regions of each lens provide different optical power relative to each other. In this example, the different power regions in the world-side EDOF 1004 are created through use of two separate lens layers 1416 and 1418 that each includes an embedded compact (e.g., Fresnel) lens (1402 and 1406 respectively) embedded in a layer of embedding material (1404 and 1408 respectively). The layers 1416 and 1418 may be separated from each other by another layer 1420 of optically transparent material. In some embodiments, layer 1420 is a carrier substrate on which the lens 1406 has been formed. Layer 1420 may be omitted if the lens 1406 is thick enough or otherwise configured to be suitably mechanically stiff.

[0159] The eye-side lens 1002 shown in FIG. 14A may also be configured into two regions as the counterpart to world-side lens 1004, with a two-sided compact lens 1412(e.g., Fresnel lens) embedded on either side of the lens in embedding material 1410 and 1414. Alternatively, two separated (e.g., plano-Fresnel) lens layers may be used as in the example of FIG. 14 A.

[0160] FIG. 14B shows an example of an eye-side EDOF lens 1002 and a world-side EDOF lens 1004, configured to provide a “trifocal” arrangement in which three regions of each lens provide different optical power relative to each other. In this example, the different power regions in the world-side EDOF 1004 are created through use of three separate lens layers 1450, 1452, and 1454 that each includes an embedded compact (e.g., Fresnel) lens (1442, 1444, and 1426 respectively) embedded in a layer of embedding material (1440, 1422, and 1448 respectively). The layers 1450, 1452, and 1454 may be separated from each other by other layers 1446 and 1424 of optically transparent material. In some embodiments, layers 1446 and / or 1424 are a carrier substrate on which a respective one or more lenses has been formed. These layers may be omitted if the lens is thick enough or otherwise configured to be suitably mechanically stiff.

[0161] The eye-side lens 1002 shown in FIG. 14B may also be configured into three regions as the counterpart to world-side lens 1004. In the example show n, three lens layers 1456, 1458, and 1460 are stacked to create the composite EDOF lens 1002, with each layer including an embedded compact (e.g., Fresnel) lens (1428, 1434, and 1438 respectively) embedded in a layer of embedding material (1430, 1432, and 1434 respectively). The layers may be separated from each other by other layers 1462 and 1464 of optically transparent material. In some embodiments, layers 1462 and / or 1464 are a carrier substrate on which a respective one or more lenses has been formed. These layers may be omitted if the lens is thick enough or otherwise configured to be suitably mechanically stiff.

[0162] Any suitable fabrication technique may be used to manufacture embedded lenses such as those shown in FIGS. 14A and 14B, for example molding of a polymer material through use of a template, followed by curing (UV, thermal, etc.) the material to form the desired lens shape. In some implementations, injection molding may be employed, for example to fabricate a two-sided lens such as lens 1412.

[0163] The example of FIG. 14A shows a lens arrangement that may be used to achieve the “bifocal” effect described with reference to FIG. 13B. For example, the top region of lower optical power may correspond to the top of the page (e.g., the top side of the user’s FOV), and the bottom region of higher optical power may correspond to the bottom of the page (e.g., the bottom side of the user’s FOV). Similarly, the example of FIG. 14B shows a lens arrangement that may be used to achieve the “trifocal” effect described with referenceto FIG. 13C. For example, the top region of lower optical power may correspond to the top of the page (e.g., the top side of the user's FOV), and the bottom region of higher optical power may correspond to the bottom of the page (e.g., the bottom side of the user’s FOV), with the middle region between the top and bottom regions.

[0164] In some examples, the number of regions of different optical power may be achieved by stacking a number of lens layers to form a composite lens, in which each lens layer is an embedded piano-compact (e.g., plano-Fresnel) lens. Alternatively, two pianocompact lens layers may be replaced by a two-sided lens in which the front and back sides have different configurations (as in the example of lens 1412). The number of regions of different optical power may correspond to a sum, in each lens, of the number of pianocompact lens layers plus two times the number of two-sided asymmetric lenses included in the arrangement.

[0165] FIG. 15 illustrates a schematic 1500 of an example process for fabricating an EDOF lens. Any suitable technique can be used to manufacture the compact (e.g., Fresnel) lenses used in various embodiments, such as diamond turning, injection molding, direct UV or thermal molding, and so forth. In this example, a molding technique is employed.

[0166] In 1510, a suitable amount of molding material 1502 is deposited onto a substrate 1504. The molding material 1502 may be a curable polymer material, for example an acrylate-based UV-cured or thermal-cured polymer material. The molding material 1502 can also be an epoxy or epoxy-based material. In some embodiments, the substrate 1504 has been previously treated to apply a vapor coating to create an adhesion layer. A mold 1506 (or template) is then provided. In some embodiments, the mold 1506 is heated or cooled to be at a desired temperature prior to molding the material 1502. The mold 1506 may then be applied (e.g., lowered) onto the material 1502. In some examples, the substrate 1504 may be held in place by a suitable stage (not shown) to ensure that the substrate is reliably positioned at the desired location relative to the mold, during the process. The substrate may also be referred to as a carrier substrate. The substrate may be included in the final VOA stack following manufacture, or the lens may be removed from the substrate prior to inclusion in the stack (e.g., if the lens by itself is suitably stiff to provide desired mechanical stability without the substrate).

[0167] In 1520, the mold 1506 has been pressed (e.g., downward) onto the material 1502 to mold the material 1502 into the desired lens shape 1508. The material 1502 may also be cured at this stage, through application of heat, UV radiation, or through other meanssuitable for the curable material 1502 being used. Curing may be performed for a sufficient amount of time to ensure adequate curing of the material 1502.

[0168] In 1530, the mold 1506 is moved away from the material 1502 and substrate 1504, leaving the cured material in the desired shape of the compact lens, in this example a Fresnel lens.

[0169] After the cured lens of the desired shape has been created, the lens may be coated with an anti-reflective coating and / or embedded in an embedding material as discussed with reference to FIG. 12. An anti -reflective coating may be composed of any suitable material(s) and / or configured in any suitable configuration. For example, an anti-reflective coating can be formed of alternating layers of TiCh and SiCh. As another example, the anti-reflective coating can be made of a single material of low refractive index, such as MgF2, SiCh, and so forth. The embedded and / or coated lens may be arranged (e.g., sandwiched) between layers of glass to provide for a component that is flat on one or both sides and may be more suitable for inclusion in a VOA stack.

[0170] Although this example shows the use of a molding / curing technique to create a positive-powered lens, a similar technique can also create a negative-powered lens. In some embodiments, the material 1502 is initially deposited onto the mold 1506 instead of onto the substrate 1504, and the mold 1506 with deposited material 1502 may then be brought into contact with the substrate 1504 by moving one or both of the mold 1506 or substrate 1504. to press the material into the desired lens configuration.

[0171] FIG. 16 illustrates a cross-sectional side view of example EDOF lenses. In this example, the eye-side EDOF lens 1002 and the world-side EDOF lens 1004 are a ty pe of compact lens that has a substantially flattened periphery, i.e., a substantially flat peripheral or outer region. In this type of compact lens, an outer or peripheral region 1604 of the lens (away from its center) is at least partly flattened in shape relative to the center region 1602 of the lens that has optical power. The peripheral region 1604 transitions to the center region 1602 at a discontinuity 1606. In the example of FIG. 16, the eye-side EDOF lens 1002 and world-side EDOF lens 1004 are piano-flattened periphery lenses with the flattened periphery configuration on one surface of the lens, with the opposite surface being substantially planar. In this example, the eye-side lens 1002 has negative optical power in its center region 1602, and the world-side lens 1004 has positive optical powder in its center region 1602. The optical power of the lens 1004 is substantially equal in magnitude, and opposite to, the optical power of the lens 1002. to neutralize the 1002 and ensure that world light is minimally or not depth-adjusted, as described above.

[0172] In some embodiments, the flattened periphery lenses described herein as shown in the example of FIG. 16 may be treated with a coating and / or embedded in an embedding material as described with regard to the Fresnel lens embodiments.

[0173] Although this and other examples herein may discuss lenses that exhibit radial symmetry, embodiments are not so limited. For example, the center region 1602 may be oval or ellipsoid in shape, and the peripheral region 1604 may surround the center region 1602.

[0174] As with the Fresnel EDOF lenses discussed above, the eye-side flattened periphery' EDOF lens may be used to alter the perceived depth of virtual objects that are projected into the eye(s) of the user by way of the waveguide(s). Accordingly, objects projected within the center region 1602 are depth-altered to appear closer than they would otherwise appear (e.g., at optical infinity) in the absence of a negative-powered eye-side EDOF lens. Any objects that would be projected in the peripheral region 1604 would not be depth-altered. The world-side EDOF lens operates to ensure that world light (e.g., conveying real world objects) is not depth-altered. Accordingly, the center region 1602 may also be referred to as the virtual view zone or virtual zone, and the peripheral region 1604 may also be referred to as the peripheral view zone.

[0175] A flattened periphery' lens used as an EDOF lens may have any suitable dimensions and / or configuration. For example, the curved center region 1602 of the lens can be about 72 mm wide and about 2.28 mm thick, surrounded by a flattened peripheral region 1604 that is less than 1 mm wide.

[0176] In some embodiments, a traditional plano-convex (or plano-concave) lens can be used as at least one of the EDOF lenses in the VOA stack. In one example, a traditional plano-convex (or plano-concave) lens used as an EDOF lens has a lens thickness of 1.455 mm with a 40 mm lens clear aperture. In another example, a traditional lens has a lens thickness of 2.28 mm with a 72 mm aperture. By' using a flattened periphery lens instead, the same 1.455 mm lens thickness as a traditional lens can be maintained with a larger aperture of 72 mm. Accordingly, use of a flattened periphery lens (or Fresnel lens) as a compact lens instead of a traditional lens can provide a larger aperture with similar optical power and thickness within the stack.

[0177] FIG. 17 illustrates example FOVs within a display system. The display system may support the definition of two different FOVs that each extend outward through a range of angles from the center of the user’s eye(s) 210. A virtual FOV 1702 is the portion of the user’s FOV in the center of the device aperture, into which the display system may projectvirtual objects through use of the projector system and waveguide(s). A see-through FOV 1704 may be defined as the user's entire FOV out to an edge 1706 of the aperture to view the real world, or at least a larger angular portion of the user’s FOV than that spanned by the virtual FOV 1702. The see-through FOV 1704 is larger (e.g., much larger) than the virtual FOV 1702. Although this example shows the two FOVs bounded by concentric circles, with a circular outer edge 106 of the aperture, embodiments are not so limited. Other suitable shapes may be employed for the virtual FOV 1702 and see-through FOV 1704, as well as for the overall system aperture. In some examples, the virtual FOV 1702 spans an arc segment that is at least 50 degrees in horizontal by at least 50 degrees in vertical, or at least 45 degrees in horizontal by at least 45 degrees in vertical, with the see- through FOV 1704 is larger than the virtual FOV 1702.

[0178] FIGS. 18, 19, and 20 illustrate a cross-sectional side view of example EDOF lenses providing optical power within a display device. In the example view 1800 shown in FIG. 18, the EDOF lenses are traditional plano-convex or plano-concave lenses. In this particular example, the eye-side EDOF lens 1002 is a plano-convex lens having negative power, and the world-side EDOF lens 1004 is a plano-concave lens having positive power. Between the two lenses 1002 and 1004 is a VOA portion 1806, which at least includes the waveguide(s) and may also include other layers of the VOA. Embodiments support various options for placing the EDOF lenses in the VOA stack, as discussed further below, with the lens 1002 being between the eye(s) 210 and the nearest waveguide to the eye(s), and the lens 1004 being between the world and the farthest waveguide from the eye(s). The virtual FOV 1702 and the see-through FOV 1704 each extend outward from the center 1808 of the user's eye 210, with the virtual FOV 1702 being smaller than the see-through FOV 1704.

[0179] In the example view 1900 shown in FIG. 19, the EDOF lenses are Fresnel lenses as discussed above. In some embodiments, the lenses are coated and / or embedded as discussed above. In this example, the eye-side EDOF lens 1002 is a plano-Fresnel lens having negative power, and the world-side EDOF lens 1004 is a plano-Fresnel lens having positive power. Between the two lenses 1002 and 1004 is a VOA portion 1806, which at least includes the waveguide(s) and may also include other layers of the VOA.

[0180] The Fresnel lenses exhibit discontinuities in their surface, such as discontinuities 1112 and 1114 discussed above, which separate a fold from an adjacent fold. The discontinuities tend to introduce optical artifacts that may negatively impact the quality of the images projected to the user’s eye(s). Accordingly, in some embodiments the lenses1002 and 1004 are arranged such that the virtual FOV 1702 is within, or no broader than, the center region of the lens 1002 bounded by the first discontinuity 1902 (e.g., peak or trough) in the surface of lens 1002, and / or such that the virtual FOV 1702 is within, or no broader than, the center region of the lens 1004 bounded by the first discontinuity 1904 in the surface of lens 1004, where the first discontinuity is defined as the innermost discontinuity that is closest to the center of the lens. The see-through FOV 1704 may extend beyond the first discontinuity of either or both lenses. The discontinuity may be the local maximum of a particular ridge of the Fresnel lens, as shown in the example of FIG. 19. Alternatively, the discontinuity may be the local minimum of a particular ridge.

[0181] Keeping the virtual FOV 1702 within the non-discontinuous region(s) of the lens(es) ensures that any artifacts introduced by the discontinuities do not affect the appearance of the projected virtual objects. Moreover, because the human vision system has low visual acuity in its peripheral vision, artifacts introduced into that portion of the see-through FOV 1704 that includes the lens discontinuities may not be a readily perceived by the user, and may have little impact on the user’s overall visual experience using the wearable display device.

[0182] In the example view 2000 shown in FIG. 20, the EDOF lenses are flattened periphery' lenses as discussed above. In some embodiments, the lenses are coated and / or embedded as discussed above. In this example, the eye-side EDOF lens 1002 is a piano- flattened periphery lens having negative power, and the world-side EDOF lens 1004 is a piano-flattened periphery lens having positive power. Between the two lenses 1002 and 1004 is a V O A portion 1806, which at least includes the waveguide(s) and may also include other layers of the VOA.

[0183] As with the Fresnel lenses, the flattened periphery’ lenses also exhibit discontinuities in their surface, such as discontinuities 1606 discussed above that separate the center region 1602 from the peripheral region 1604. These discontinuities also tend to introduce optical artifacts that may negatively impact the quality of the images projected to the user’s eye(s). Accordingly, in some embodiments the lenses 1002 and 1004 are arranged such that the virtual FOV 1702 is within, or no broader than, the center region 1602 of the lens 1002 bounded by the discontinuity 2002 in the surface of lens 1002, and / or such that the virtual FOV 1702 is within, or no broader than, the center region 1602 of the lens 1004 bounded by the first discontinuity' 2004 in the surface of lens 1004. The see- through FOV 1704 may extend beyond the discontinuity of either or both lenses.

[0184] In some embodiments, the innermost discontinuity of the compact lens (e.g., Fresnel lens or flattened periphery lens) is within the virtual FOV 1702 while being at least a threshold angular distance (e.g., 30 degrees) away from the optical axis (e.g., the Z-axis).

[0185] An arrangement of the display device that keeps the virtual FOV 1702 within the non-discontinuous region(s) of the lens(es) ensures that any artifacts introduced by the discontinuities do not affect the appearance of the projected virtual objects. Moreover, because the human vision system has low visual acuity in its peripheral vision, artifacts introduced into that portion of the see-through FOV 1704 that includes the lens discontinuities may not be readily perceived by the user, and therefore may have little impact on the user's overall visual experience using the wearable display device.

[0186] Although examples herein describe a virtual FOV or see-through FOV that is approximately circular, as shown in the example of FIG. 17 in which a FOV exhibits radial symmetry, embodiments are not so limited. In some embodiments, a virtual FOV and / or a see-through FOV may be radially asymmetric to span an arc segment that is wider in one dimension than in another dimension. Accordingly, a FOV may be elliptically shaped. In some examples, the long axis of the elliptical FOV may be along an X direction such that the FOV extends longer side-to-side relative to the user’s eyes than the FOV extends along a Y direction up and / or down relative to the user’s eyes (e.g., with the optical axis along the Z direction). In some examples the long axis of the elliptical FOV may be along the Y direction. The long axis may also be along another suitable direction.

[0187] In some examples, the virtual FOV is at least 45 degrees in at least one dimension. In some examples, the virtual FOV is at least 30 degrees in at least one dimension. In some examples, the virtual FOV is at most 60 degrees in at least one dimension. In some examples, the virtual FOV is at most 45 degrees in at least one dimension. In some examples, the virtual FOV is at most 30 degrees in at least one dimension.

[0188] Returning to FIG. 10, the example arrangement 1000 shows the eye-side EDOF lens 1002 and the world-side EDOF lens 1004 at particular positions on the VOA stack. However, this example is not limiting for embodiments. The eye-side EDOF lens 1002 and world-side EDOF lens 1004 may be located at any suitable locations within the stack such that they are on opposite sides of the waveguide(s) in the assembly, with the eye-side EDOF lens 1002 inward from the waveguide(s) and the world-side EDOF lens 1004 outward from the waveguide(s). As stated above, the eye-side EDOF lens 1002 is positioned inward from the waveguide(s) to alter the depth of the virtual objects that areprojected using the waveguide(s) into the eye 210. For example, a negative powered eyeside EDOF lens 1002 can be employed to alter the depth of the virtual objects from optical infinity to a nearer depth. The world-side EDOF lens 1004 is configured with substantially equal magnitude, and opposite, optical power as the eye-side EDOF lens 1002, to neutralize the effect of the eye-side lens 1002 and ensure that the light passing through the assembly to the eye 210 (e.g., world light) is not shifted in depth. Accordingly, the world-side EDOF lens 1004 may be arranged at a suitable position in the stack that is outward from the waveguide(s).

[0189] The eye-side EDOF lens 1002 may be located at any suitable position in the stack that is between the eye 210 and the waveguide layer 1014(1) that is nearest to the eye 210 or, in instances where the prescription insert 1008 is in use and has been inserted into the stack, between the prescription insert 1008 and the waveguide layer 1014(1). For example, the eye-side EDOF lens 1002 can be located: immediately inward from the illumination layer 1006 (as shown), between the illumination layer 1006 and the frame element 1034(1), or between the frame element 1034(2) and the cover layer 1012(1). In instances where the VOA does not include the cover layers 1012(1) and 1012(2), the eye-side EDOF lens 1002 can be located between the waveguide layer 1014(1) and the frame element 1034(2).

[0190] Similarly, the world-side EDOF lens 1004 may be located at any suitable position in the stack that is between the world and the waveguide layer 1014(3) that is farthest from the eye 210. For example, the world-side EDOF lens 1004 may be located between the waveguide layer 1014(3) and the frame element 1034(3) or, in instances where the VOA does not include the cover layers 1012(1) and 1012(2), the world-side EDOF lens 1004 can be located between the waveguide layer 1014(3) and the frame element 1034(3). The world-side EDOF lens 1004 can be located at any suitable location within the front carrier section 1030, for example: between layer 1022 and the frame element 1034(3), between QWP layer 1024(1) and layer 1022, between LC panel layer 1026 and QWP layer 1024(1), between QWP layer 1024(2) and absorptive polarizer layer 1016(1), between absorptive polarizer layer 1016(1) and QWP layer 1024(3), between QWP layer 1024(3) and retarder layer 1018, between retarder layer 1018 and QWP layer 1024(4), between QWP layer 1024(4) and absorptive polarizer layer 1016(2), between absorptive polarizer layer 1016(2) and QWP layer 1024(5), or between QWP layer 1024(5) and frame element 1034(4) (as shown). The world-side EDOF lens 1004 can also be located at any suitable location within the cosmetic window section 1040. for example: between frame element 1034(4) and QWP layer 1024(6), between QWP layer 1024(6) and reflective polarizer layer1028, between reflective polarizer layer 1028 and depolarizer layer 1036, between the depolarizer layer 1036 and the base substrate layer 1032, or immediately outward from the base substrate layer 1032.

[0191] Embodiments support the use of any suitable type of lens for each of the EDOF lenses 1002 and 1004. For example, the eye-side EDOF lens 1002 may be a traditional (e.g., plano-concave) lens, a Fresnel lens that includes or omits the coating and / or the embedding as discussed above, or a flattened periphery lens that includes or omits the coating and / or the embedding as discussed above. Similarly, the world-side EDOF lens 1004 may be a traditional (e.g., plano-convex) lens, a Fresnel lens that includes or omits the coating and / or the embedding as discussed above, or a flattened periphery lens that includes or omits the coating and / or the embedding as discussed above. The two EDOF lenses may be lenses of the same type, or of different types. For example, an embedded, coated Fresnel lens may be used for the eye-side EDOF lens 1002, and a traditional planoconvex lens may be used for the world-side EDOF lens 1004. As another example, an embedded, coated Fresnel lens may be used for the world-side EDOF lens 1004, and a traditional plano-concave lens may be used for the eye-side EDOF lens 1002. The lenses may also be configured to provide different regions of different optical power, as shown in the examples of FIGS. 13B and 13C, or may be configured with a varying optical power across the aperture of the lenses, as shown in the example of FIG. 13D. In instances where a Fresnel lens is used as at least one of the EDOF lenses, the Fresnel lens may be a lens with constant ridge height or constant ridge width, as discussed above with reference to FIG. 11.

[0192] The EDOF lenses may be of any suitable dimensions and of any suitable optical power. For example, the eye-side EDOF lens 1002 may have optical power of about -1 diopter (e.g., negative power) such that the virtual objects projected through the w-aveguide(s) appear to the user to be about 1 m away. As another example, the eye-side EDOF lens 1002 may have optical power of about -0.5 to about -3 diopter such that the virtual obj ects appear to be about a third of a meter to about 2 m away . As another example, the eye-side EDOF lens 1002 may have optical power of about -0.75 to about -2 diopter such that the virtual objects appear to be about 1 and a third meters to about 0.5 m away. As discussed above, the world-side EDOF lens 1004 may have a power opposite that of the eye-side EDOF lens and approximately equal in magnitude, to ensure that real-world objects appear at their actual physical distance from the user.

[0193] The EDOF lenses may have any suitable thickness for incorporation in the VOA stack as described herein. For example, a maximum thickness of one or both of the EDOF lenses (e.g., not embedded) or a total embedded thickness of one or both of the EDOF lenses may be at least about 1.0 mm thick, at least about 1.2 mm thick, at least about 1.6 mm thick, and / or at most about 2.2 mm thick.

[0194] The EDOF lenses may have any suitable lens aperture. For example, one or both of the EDOF lenses may have a lens aperture of at least 20 mm. In examples where one or both of the EDOF lenses is a Fresnel lens, the lens may have any suitable arrangement, number, and dimension of ridges. For example, the ridge height may be at least about 50 pm, in a range of about 50 pm to about 200 pm, in a range of about 50 pm to about 600 pm, or of some other suitable dimension.

[0195] In some embodiments, one or both of the EDOF lenses can be laminated to, or otherwise mechanically coupled to, one of the other components in the VOA. For example, one or both EDOF lenses can be respectively coupled (e.g., laminated) to one of the layers that forms the selective dimmer apparatus, e.g., the LC panel layer 1026, between QWP layers 1024(1) and 1024(2) and with the absorptive polarizer layer 1016(1) arranged on the world side of the LC panel layer 1026. As another example, one or both of the EDOF lenses can be respectively coupled to one of the layers that forms the angle attenuator apparatus, e.g., the C-plate retarder of layer 1018 positioned between QWPs, such as layers 1024(3) and 1024(4). In some embodiments, one or both of the EDOF lenses can be coupled to one of the cover glass layers 1012 that protect the waveguide layer(s). Alternatively, one or both of the EDOF lenses (e.g., embedded as discussed herein) may be situated on either side of the waveguide layer(s) to function as a cover layer 1012 that protects the waveguide layer(s) while functioning as the EDOF lens.Additional Examples

[0196] Example 1 : A wearable display device comprising: one or more waveguides configured to convey and project virtual image elements to an eye of a user of the wearable display device, wherein the one or more waveguides are at least partly transparent to transmit light from a surrounding environment to the eye; a first extended depth of field (EDOF) lens arranged between the one or more waveguides and the eye, the first EDOF lens having an optical power to alter a depth of the projected virtual image elements; and a second EDOF lens arranged on an opposite side of the one or more waveguides from the first EDOF lens, the second EDOF lens having an optical power that is substantially equalin magnitude to, and opposite to, the optical power of the first EDOF lens, wherein at least one of the first EDOF lens and the second EDOF lens comprises a compact lens.

[0197] Example 2: The wearable display device of Example 1, wherein the compact lens is a Fresnel lens.

[0198] Example 3: The wearable display device of Example 2, wherein the compact lens is a constant ridge height Fresnel lens.

[0199] Example 4: The wearable display device of Example 2, wherein the compact lens is a constant ridge width Fresnel lens.

[0200] Example 5: The w earable display device of Example 1, wherein the compact lens is a flattened periphery' lens.

[0201] Example 6: The w earable display device of any of the above Examples, wherein the compact lens is coated with a coating.

[0202] Example 7 : The wearable display device of Example 6, wherein the coating is an anti-reflective coating.

[0203] Example 8: The wearable display device of Example 6 or Example 7, wherein the coating is at least partly composed of one or more of Silicon Dioxide (SiCh), Titanium Dioxide (TiCh), or Magnesium Difluoride (MGF2).

[0204] Example 9: The wearable display device of any of Examples 6-8, wherein the coating has a refractive index less than that of the compact lens.

[0205] Example 10: The wearable display device of any of the above Examples, wherein the compact lens is embedded in an embedding material.

[0206] Example 11 : The wearable display device of Example 10, wherein the embedding material has a refractive index in a range from about 1. 1 to about 1.7.

[0207] Example 12: The wearable display device of any of the above Examples, w herein the compact lens is composed of a material that includes one or more of a curable polymer or an epoxy.

[0208] Example 13: The wearable display device of any of the above Examples, wherein the first EDOF lens has a negative optical power, and wherein the second EDOF lens has a positive optical power.

[0209] Example 14: The wearable display device of any of the above Examples, wherein each of the first EDOF lens and the second EDOF lens has a substantially same optical pow er across its aperture.

[0210] Example 15: The wearable display device of any of the above Examples, wherein each of the first EDOF lens and the second EDOF lens includes two regions of different optical power.

[0211] Example 16: The wearable display device of Example 15, wherein the first EDOF lens includes a first region having a first optical power and a second region having a second optical power, wherein the second EDOF lens includes a third region having a third optical power and a fourth region having a fourth optical power, wherein the first region spans a same portion of the field of view (FOV) of the wearable display device as the third region, wherein the second region spans a same portion of the FOV as the fourth region, wherein the first optical power is substantially equal in magnitude to, and opposite to, the third optical power, and wherein the second optical power is substantially equal in magnitude to, and opposite to, the fourth optical power.

[0212] Example 17: The wearable display device of Example 15 or Example 16, wherein each of the first EDOF lens and the second EDOF lens comprises two compact lenses arranged in a composite lens.

[0213] Example 18: The wearable display device of any of the above Examples, wherein each of the first EDOF lens and the second EDOF lens includes at least three regions of different optical power.

[0214] Example 19: The wearable display device of Example 18, wherein the first EDOF lens includes a first region having a first optical power, a second region having a second optical power, and a third region having a third optical power, wherein the second EDOF lens includes a fourth region having a fourth optical power, a fifth region having a fifth optical power, and a sixth region having a sixth optical power, wherein the first region spans a same portion of the field of view (FOV) of the wearable display device as the fourth region, wherein the second region spans a same portion of the FOV as the fifth region, wherein the third region spans a same portion of the FOV as the sixth region, wherein the first optical power is substantially equal in magnitude to, and opposite to, the fourth optical power, wherein the second optical power is substantially equal in magnitude to, and opposite to, the fifth optical power, and wherein the third optical power is substantially equal in magnitude to, and opposite to, the sixth optical power.

[0215] Example 20: The wearable display device of Example 18 or Example 19, wherein each of the first EDOF lens and the second EDOF lens comprises at least three compact lenses arranged in a composite lens.

[0216] Example 21: The wearable display device of any of the above Examples, wherein each of the first EDOF lens and the second EDOF lens has a varying optical power that varies with location in the aperture of the respective lens.

[0217] Example 22: The wearable display device of Example 21, wherein the magnitude of the vary ing optical power of each of the first EDOF lens and the second EDOF lens increases with increasing distance from the top of the lens.

[0218] Example 23: The wearable display device of any of the above Examples, wherein the wearable display device is configured to project the virtual image elements within a virtual FOV that is smaller in at least one dimension than a see-through FOV of the wearable display device.

[0219] Example 24: The wearable display device of Example 23, wherein the innermost discontinuity of the compact lens is within the virtual FOV while being at least a threshold angular distance away from an optical axis of the wearable display device.

[0220] Example 25: The w earable display device of Example 24, wherein the threshold angular distance is 30 degrees.

[0221] Example 26: The wearable display device of Example 23, wherein the compact lens is arranged such that the virtual FOV, at the location of the compact lens along an optical axis of the wearable display device, is within a center region of the compact lens that is bounded by an innermost discontinuity of the compact lens.

[0222] Example 27: The wearable display device of any of Examples 23-26, wherein the see-through FOV at the location of the compact lens extends beyond the center region of the compact lens.

[0223] Example 28: The wearable display device of either of any of Examples 23-27, wherein the virtual FOV is approximately circular.

[0224] Example 29: The wearable display device of any of Examples 23-27, wherein the virtual FOV is elliptical.

[0225] Example 30: The wearable display device of any of Examples 23-29, wherein the virtual FOV spans an arc segment that is at least about 45 degrees in at least one dimension.

[0226] Example 31 : The wearable display device of any of Examples 23-29, wherein the virtual FOV spans an arc segment that is at least about 30 degrees in at least one dimension.

[0227] Example 32: The wearable display device of any of Examples 23-31, wherein the virtual FOV spans an arc segment that is at most about 60 degrees in at least one dimension.

[0228] Example 33: The wearable display device of any of Examples 23-31, wherein the virtual FOV spans an arc segment that is at most about 45 degrees in at least one dimension.

[0229] Example 34: The wearable display device of any of Examples 23-31, wherein the virtual FOV spans an arc segment that is at most about 30 degrees in at least one dimension.

[0230] Example 35: The wearable display device of any of the above Examples, wherein one or both of the first EDOF lens or the second EDOF lens has a thickness of at least about 1 mm, at least about 1.2 mm, at least about 1.5 mm, or at most about 2.2 mm.

[0231] Example 36: The wearable display device of Example 35, wherein the thickness is the thickness of one or both of the first EDOF lens or the second EDOF lens that is embedded in an embedding material.

[0232] Example 37: The wearable display device of any of the above Examples, wherein one or both of the first EDOF lens or the second EDOF lens has a lens aperture of at least 20 mm.

[0233] Example 38: The wearable display device of any of the above Examples, wherein one or both of the first EDOF lens or the second EDOF lens is a Fresnel lens with a ridge height of at least 50 pm.

[0234] Example 39: The wearable display device of any of the above Examples, wherein one or both of the first EDOF lens or the second EDOF lens is a Fresnel lens with a ridge height in a range of about 50 pm to about 200 pm.

[0235] Example 40: The wearable display device of any of the above Examples, wherein the first EDOF lens is smaller in at least one dimension than the second EDOF lens.

[0236] Example 41: The wearable display device of any of the above Examples, wherein the wearable display device is an augmented reality display device.

[0237] Example 42: The wearable display device of any of the above Examples, further comprising: a projector system configured to inject, into the one or more waveguides, image light that conveys the virtual image elements, wherein the one or more waveguides include at least one in-coupling element that in-couples the image light from the projector system into the one or more waveguides such that the one or more waveguides propagatethe image light within the waveguide by total internal reflection (TIR), and wherein the one or more waveguides include at least one out-coupling element that out-couples the image light from the one or more waveguides to redirect the image light toward the eye.

[0238] Example 43: The wearable display device of Example 42, wherein the first EDOF lens is arranged between the at least one out-coupling element and the eye.

[0239] Example 44: The wearable display device of any of the above Examples, further comprising a visible optics assembly (VOA) that includes the one or more waveguides, the first EDOF lens, and the second EDOF lens.

[0240] Example 45: The wearable display device of Example 44, wherein at least one of the first EDOF lens or the second EDOF lens is coupled to at least one other component of the VOA.

[0241] Example 46: The wearable display device of Example 45, wherein the at least one other component is included in at least one of a selective dimmer apparatus or an angle attenuator apparatus that is included in the VOA.

[0242] Example 47 : The wearable display device of Example 45 or 46. wherein the at least one other component is a cover glass layer arranged on at least one side of the at least one waveguide.

[0243] Example 48: The wearable display device of Example 44, at least one of the first EDOF lens or the second EDOF lens is an embedded compact lens that is arranged on at least one side of the at least one waveguide and that functions as a cover layer to protect the at least one waveguide.

[0244] Example 49: An optical device comprising: a compact lens; and an embedding material in which at least a portion of the compact lens is embedded.

[0245] Example 50: The optical device of Example 49. wherein the compact lens is a Fresnel lens.

[0246] Example 51: The optical device of Example 50, wherein the compact lens is a Fresnel lens having an approximately constant ridge height.

[0247] Example 52: The optical device of Example 50, wherein the compact lens is a Fresnel lens having an approximately constant ridge width.

[0248] Example 53: The optical device of Example 50, wherein the compact lens is a Fresnel lens with a ridge height of at least 50 pm.

[0249] Example 54: The optical device of Example 50, wherein the compact lens is a Fresnel lens with a ridge height in a range of about 50 pm to about 200 pm.

[0250] Example 55: The optical device of Example 50, wherein the compact lens is a Fresnel lens with a ridge height in a range of about 50 pm to about 600 pm.

[0251] Example 56: The optical device of Example 49, wherein the compact lens is a flattened periphery lens.

[0252] Example 57: The optical device of any of Examples 49-56, wherein the compact lens is coated with a coating, and wherein at least the portion of the coated compact lens is embedded in the embedding material.

[0253] Example 58: The optical device of Example 57, wherein the coating is an anti- reflective coating.

[0254] Example 59: The optical device of Example 57 or Example 58, wherein the coating is at least partly composed of one or more of Silicon Dioxide (SiCh), Titanium Dioxide (TiCh), or Magnesium Difluoride (MGF2).

[0255] Example 60: The optical device of any of Examples 57-59, wherein the coating has a refractive index less than that of the compact lens.

[0256] Example 61: The optical device of any of Examples 50-60, wherein the embedding material has a refractive index in a range from about 1. 1 to about 1.7.

[0257] Example 62: The optical device of any of Examples 50-61, wherein the compact lens is composed of a material that includes one or more of a curable polymer or an epoxy.

[0258] Example 63: The optical device of any of Examples 50-62, wherein the embedded compact lens has a thickness of at least about 1 mm, at least about 1.2 mm, at least about 1 .5 mm, or at most about 2.2 mm.

[0259] Example 64: The optical device of any of Examples 50-63, wherein the compact lens has a lens aperture of at least 20 mm.Additional Considerations

[0260] Unless the context clearly indicates otherwise, throughout the description and the claims, the words ‘‘comprise,’' “comprising,’" “include,’" “including,’" “have” and “having” and the like are to be construed in an inclusive sense, as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to.” The word “coupled”, as generally used herein, refers to two or more elements that may be either directly connected, or connected by way of one or more intermediate elements. Likewise, the word “connected"’, as generally used herein, refers to two or more elements that may be either directly connected, or connected by way of one or more intermediate elements. Depending on the context, “coupled” or “connected” may refer to an optical coupling oroptical connection such that light is coupled or connected from one optical element to another optical element. Additionally, the words “herein,” “above,” “below,” “infra,” “supra,” and words of similar import, when used in this application, shall refer to this application as a whole and not to any particular portions of this application. Where the context permits, words in the above Detailed Description using the singular or plural number may also include the plural or singular number, respectively. The word “or” in reference to a list of two or more items is an inclusive (rather than an exclusive) “or”, and “or” covers all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of one or more of the items in the list, and does not exclude other items being added to the list. In addition, the articles “a,” “an,” and “the” as used in this application and the appended claims are to be construed to mean “one or more” or “at least one” unless specified otherwise.

[0261] As used herein, a phrase referring to “at least one of’ a list of items refers to any combination of those items, including single members. As an example, “at least one of: A, B, or C” is intended to cover: A, B, C, A and B, A and C, B and C, and A, B, and C. Conjunctive language such as the phrase “at least one of X, Y and Z,” unless specifically stated otherwise, is otherwise understood with the context as used in general to convey that an item, term, etc. may be at least one of X, Y or Z. Thus, such conjunctive language is not generally intended to imply that certain embodiments require at least one of X, at least one of Y and at least one of Z to each be present.

[0262] The terms “substantially” or “approximately” convey a meaning that is readily understandable by one of ordinary' skill in the art as essentially conforming to a particular shape, dimension, word, or other trait that substantially modified, such that the element being discussed need not be exactly so. For example, substantially circular means that a shape or obj ect resembles a circle and may be perceived by a person (or machine) as a circle even though that shape or object may include one or more deviations from a mathematically precise circle. Similarly, a statement herein that two values are “substantially” or “approximately” “the same” or “equal” indicates that the two values are within a given range, tolerance, or uncertainty of one another, and that range, tolerance, or uncertainty can be expressed as the difference (if any) between the two values being within a threshold proportion of at least one of the values. For example, a statement that “X is substantially equal to Y” indicates that X differs from Y (or Y differs from X) by no more than Z% of X (or Y), wherein Z% can be 0.1%, 0.5%, 1.0%. 2.0%, 5%, and so forth.

[0263] Moreover, conditional language used herein, such as, among others, "can." "could." “might,” “may,” “e.g.,” “for example,” “such as” and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and / or states. Thus, such conditional language is not generally intended to imply that features, elements, and / or states are in any way required for one or more embodiments or whether these features, elements, and / or states are included or are to be performed in any particular embodiment.

[0264] While certain embodiments have been described, these embodiments are presented as examples and are not intended to limit the scope of the disclosure. Features of any one of the embodiments can be combined and / or substituted with features of any other(s) of the embodiments. Certain advantages of various embodiments have been described herein, and such advantages described with respect to a particular embodiment may also be applicable to other embodiments. Not all embodiments necessarily achieve each of the described advantages, and other advantages may be apparent to those of ordinary skill in the art based on this disclosure.

[0265] Embodiments have been described in connection with the accompanying drawings. However, the figures are not drawn to scale. Distances, angles, etc. are merely illustrative and do not necessarily bear an exact relationship to actual dimensions and layout of the devices illustrated.

[0266] The foregoing embodiments have been described at a level of detail to allow one of ordinary' skill in the art to make and use the devices, systems, methods, etc. described herein. A wide variety of variation is possible. Components, elements, and / or steps may be altered, added, removed, or rearranged. While certain embodiments have been explicitly described, other embodiments will become apparent to those of ordinary skill in the art based on this disclosure.

Claims

WHAT IS CLAIMED IS:

1. A wearable display device comprising: one or more waveguides configured to convey and project virtual image elements to an eye of a user of the wearable display device, wherein the one or more waveguides are at least partly transparent to transmit light from a surrounding environment to the eye; a first extended depth of field (EDOF) lens arranged between the one or more waveguides and the eye, the first EDOF lens having an optical power to alter a depth of the projected virtual image elements; and a second EDOF lens arranged on an opposite side of the one or more w aveguides from the first EDOF lens, the second EDOF lens having an optical power that is substantially equal in magnitude to, and opposite to, the optical power of the first EDOF lens, wherein at least one of the first EDOF lens and the second EDOF lens comprises a compact lens.

2. The wearable display device of claim 1, wherein the compact lens is a Fresnel lens.

3. The wearable display device of claim 2, wherein the compact lens is a constant ridge height Fresnel lens.

4. The wearable display device of claim 2, wherein the compact lens is a constant ridge width Fresnel lens.

5. The wearable display device of claim 1, wherein the compact lens is a flattened periphery lens.

6. The wearable display device of any of the above claims, wherein the compact lens is coated with a coating.

7. The wearable display device of claim 6, wherein the coating is an anti -reflective coating.

8. The wearable display device of claim 6 or claim 7, wherein the coating is at least partly composed of one or more of Silicon Dioxide (SiCh), Titanium Dioxide (TiCh), or Magnesium Difluoride (MGF2).

9. The wearable display device of any of claims 6-8, wherein the coating has a refractive index less than that of the compact lens.

10. The wearable display device of any of the above claims, wherein the compact lens is embedded in an embedding material.

11. The wearable display device of claim 10, wherein the embedding material has a refractive index in a range from about 1.1 to about 1.7.

12. The wearable display device of any of the above claims, wherein the compact lens is composed of a material that includes one or more of a curable polymer or an epoxy.

13. The wearable display device of any of the above claims, wherein the first EDOF lens has a negative optical power, and wherein the second EDOF lens has a positive optical power.

14. The wearable display device of any of the above claims, wherein each of the first EDOF lens and the second EDOF lens has a substantially same optical power across its aperture.

15. The wearable display device of any of the above claims, wherein each of the first EDOF lens and the second EDOF lens includes two regions of different optical power.

16. The wearable display device of claim 15. wherein the first EDOF lens includes a first region having a first optical power and a second region having a second optical power, wherein the second EDOF lens includes a third region having a third optical power and a fourth region having a fourth optical power, wherein the first region spans a same portion of the field of view (FOV) of the wearable display device as the third region, wherein the second region spans a same portion of the FOV as the fourth region, wherein the first optical power is substantially equal in magnitude to, and opposite to, the thirdoptical power, and wherein the second optical power is substantially equal in magnitude to, and opposite to, the fourth optical power.

17. The wearable display device of claim 15 or claim 16, wherein each of the first EDOF lens and the second EDOF lens comprises two compact lenses arranged in a composite lens.

18. The wearable display device of any of the above claims, wherein each of the first EDOF lens and the second EDOF lens includes at least three regions of different optical power.

19. The wearable display device of claim 18, wherein the first EDOF lens includes a first region having a first optical power, a second region having a second optical power, and a third region having a third optical power, wherein the second EDOF lens includes a fourth region having a fourth optical power, a fifth region having a fifth optical power, and a sixth region having a sixth optical power, wherein the first region spans a same portion of the field of view (FOV) of the wearable display device as the fourth region, wherein the second region spans a same portion of the FOV as the fifth region, wherein the third region spans a same portion of the FOV as the sixth region, wherein the first optical power is substantially equal in magnitude to, and opposite to, the fourth optical power, wherein the second optical power is substantially equal in magnitude to, and opposite to, the fifth optical power, and wherein the third optical power is substantially equal in magnitude to, and opposite to, the sixth optical pow er.

20. The wearable display device of claim 18 or claim 19, wherein each of the first EDOF lens and the second EDOF lens comprises at least three compact lenses arranged in a composite lens.

21. The wearable display device of any of the above claims, wherein each of the first EDOF lens and the second EDOF lens has a varying optical pow er that varies with location in the aperture of the respective lens.

22. The wearable display device of claim 21, wherein the magnitude of the varying optical power of each of the first EDOF lens and the second EDOF lens increases with increasing distance from the top of the lens.

23. The wearable display device of any of the above claims, wherein the wearable display device is configured to project the virtual image elements within a virtual FOV that is smaller in at least one dimension than a see-through FOV of the wearable display device.

24. The wearable display device of claim 23, wherein the innermost discontinuity7of the compact lens is within the virtual FOV while being at least a threshold angular distance away from an optical axis of the wearable display device.

25. The wearable display device of claim 24, wherein the threshold angular distance is 30 degrees.

26. The wearable display device of claim 23, wherein the compact lens is arranged such that the virtual FOV, at the location of the compact lens along an optical axis of the wearable display device, is within a center region of the compact lens that is bounded by an innermost discontinuity of the compact lens.

27. The wearable display device of any of claims 23-26, wherein the see-through FOV at the location of the compact lens extends beyond the center region of the compact lens.

28. The wearable display device of either of any of claims 23-27, wherein the virtual FOV is approximately circular.

29. The wearable display device of any of claims 23-27, wherein the virtual FOV is elliptical.

30. The wearable display device of any of claims 23-29, wherein the virtual FOV spans an arc segment that is at least about 45 degrees in at least one dimension.

31. The wearable display device of any of claims 23-29, wherein the virtual FOV spans an arc segment that is at least about 30 degrees in at least one dimension.

32. The wearable display device of any of claims 23-31, wherein the virtual FOV spans an arc segment that is at most about 60 degrees in at least one dimension.

33. The wearable display device of any of claims 23-31, wherein the virtual FOV spans an arc segment that is at most about 45 degrees in at least one dimension.

34. The wearable display device of any of claims 23-31, wherein the virtual FOV spans an arc segment that is at most about 30 degrees in at least one dimension.

35. The wearable display device of any of the above claims, wherein one or both of the first EDOF lens or the second EDOF lens has a thickness of at least about 1 mm, at least about 1.2 mm, at least about 1.5 mm, or at most about 2.2 mm.

36. The wearable display device of claim 35, wherein the thickness is the thickness of one or both of the first EDOF lens or the second EDOF lens that is embedded in an embedding material.

37. The wearable display device of any of the above claims, wherein one or both of the first EDOF lens or the second EDOF lens has a lens aperture of at least 20 mm.

38. The wearable display device of any of the above claims, wherein one or both of the first EDOF lens or the second EDOF lens is a Fresnel lens with a ridge height of at least 50 pm.

39. The wearable display device of any of the above claims, wherein one or both of the first EDOF lens or the second EDOF lens is a Fresnel lens with a ridge height in a range of about 50 pm to about 200 pm.

40. The wearable display device of any of the above claims, wherein the first EDOF lens is smaller in at least one dimension than the second EDOF lens.

41. The wearable display device of any of the above claims, wherein the wearable display device is an augmented reality display device.

42. The wearable display device of any of the above claims, further comprising: a projector system configured to inject, into the one or more waveguides, image light that conveys the virtual image elements, wherein the one or more waveguides include at least one in-coupling element that in-couples the image light from the projector system into the one or more waveguides such that the one or more waveguides propagate the image light within the waveguide by total internal reflection (TIR), and wherein the one or more waveguides include at least one out-coupling element that out-couples the image light from the one or more waveguides to redirect the image light toward the eye.

43. The wearable display device of claim 42, wherein the first EDOF lens is arranged between the at least one out-coupling element and the eye.

44. The wearable display device of any of the above claims, further comprising a visible optics assembly (VOA) that includes the one or more waveguides, the first EDOF lens, and the second EDOF lens.

45. The wearable display device of claim 44, wherein at least one of the first EDOF lens or the second EDOF lens is coupled to at least one other component of the VOA.

46. The wearable display device of claim 45, wherein the at least one other component is included in at least one of a selective dimmer apparatus or an angle attenuator apparatus that is included in the VOA.

47. The wearable display device of claim 45 or 46, wherein the at least one other component is a cover glass layer arranged on at least one side of the at least one waveguide.

48. The wearable display device of claim 44, at least one of the first EDOF lens or the second EDOF lens is an embedded compact lens that is arranged on at least one side ofthe at least one waveguide and that functions as a cover layer to protect the at least one waveguide.

49. An optical device comprising: a compact lens; and an embedding material in which at least a portion of the compact lens is embedded.

50. The optical device of claim 49, wherein the compact lens is a Fresnel lens.

51. The optical device of claim 50, wherein the compact lens is a Fresnel lens having an approximately constant ridge height.

52. The optical device of claim 50, wherein the compact lens is a Fresnel lens having an approximately constant ridge width.

53. The optical device of claim 50, wherein the compact lens is a Fresnel lens with a ridge height of at least 50 pm.

54. The optical device of claim 50, wherein the compact lens is a Fresnel lens with a ridge height in a range of about 50 pm to about 200 pm.

55. The optical device of claim 50, wherein the compact lens is a Fresnel lens with a ridge height in a range of about 50 pm to about 600 pm.

56. The optical device of claim 49, wherein the compact lens is a flattened periphery lens.

57. The optical device of any of claims 49-56, wherein the compact lens is coated with a coating, and wherein at least the portion of the coated compact lens is embedded in the embedding material.

58. The optical device of claim 57, wherein the coating is an anti-reflective coating.

59. The optical device of claim 57 or claim 58, wherein the coating is at least partly composed of one or more of Silicon Dioxide (SiCh), Titanium Dioxide (TiCh). or Magnesium Difluoride (MGF2).

60. The optical device of any of claims 57-59, wherein the coating has a refractive index less than that of the compact lens.

61. The optical device of any of claims 50-60, wherein the embedding material has a refractive index in a range from about 1.1 to about 1.7.

62. The optical device of any of claims 50-61. wherein the compact lens is composed of a material that includes one or more of a curable polymer or an epoxy.

63. The optical device of any of claims 50-62, wherein the embedded compact lens has a thickness of at least about 1 mm, at least about 1.2 mm, at least about 1.5 mm. or at most about 2.2 mm.

64. The optical device of any of claims 50-63, wherein the compact lens has a lens aperture of at least 20 mm.

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