Fixed-distance virtual and augmented reality systems and methods

Description of equivalent WO 2018026737 A1

FIXED-DISTANCE VIRTUAL AND AUGMENTED REALITY SYSTEMS AND

METHODS

0003Cross-Reference to Related Application(s)

0004[0001] This application claims priority to U.S. Provisional Application Serial Number 62/370, 1 17, filed on August 2, 2016 under attorney docket number ML.30040.00 and entitled "FIXED-DISTANCE VIRTUAL AND AUGMENTED REALITY SYSTEMS AND METHODS." This application is related to co-owned U.S. Provisional Application Serial Number 62/301 , 502 filed on February 29, 2016 entitled "VI RTUAL AND AUGMENTED REALISTY SYSTEMS AND METHODS," under attorney docket number ML.30059.00, and co-owned U.S. Patent Application Publication Number 15/146,296 filed on May 4, 2016 entitled "SEPARATED PUPIL OPTICAL SYSTEMS FOR VIRTUAL AND AUGMENTED REALITY AND METHODS FOR DISPLAYING IMAGES USING SAME," under attorney docket number ML.20058.00. The contents of the aforementioned patent applications are hereby expressly and fully incorporated by reference in their entirety, as though set forth in full.

0005Background

0006[0002] Modern computing and display technologies have facilitated the development of virtual reality ("VR"), augmented reality ("AR"), and mixed reality ("MR") systems, wherein digitally reproduced images or portions thereof are presented to a user in a manner wherein they seem to be, or may be perceived as, real. A virtual reality, or "VR", scenario typically involves presentation of digital or virtual image information without transparency to other actual real-world visual input; an augmented reality, or "AR", scenario typically involves presentation of digital or virtual image information as an augmentation to visualization of the actual world around the user. A mixed reality, or "MR", system also introduces simulated objects into a real-world environment, but these objects typically feature a greater degree of interactivity than in AR systems. The simulated elements can often times be interactive in real time. Accordingly, AR and MR scenarios involve presentation of digital or virtual image information with at least partial transparency to other actual real-world visual input. The human visual perception system is very complex, and producing an VR/AR/MR technology that facilitates a comfortable, natural-feeling, rich presentation of virtual image elements amongst other virtual or real-world imagery elements is challenging.

0007[0003] The visualization center of the brain gains valuable perception information from the motion of both eyes and components thereof relative to each other. Vergence movements (i.e., rolling movements of the pupils toward or away from each other to converge the lines of sight of the eyes to fixate upon an object at various distances) of the two eyes relative to each other are closely associated with focusing (or "accommodation") of the lenses of the eyes. Under normal conditions, changing the focus of the lenses of the eyes, or accommodating the eyes, to focus upon an 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 accommodation, under normal conditions. Working against this reflex, as do most conventional stereoscopic VR/AR/MR configurations, is known to produce eye fatigue, headaches, or other forms of discomfort in users.

0008[0004] Stereoscopic wearable glasses generally feature two displays for the left and right eyes that are configured to display images with slightly different element presentation such that a three-dimensional perspective is perceived by the human visual system. Such configurations have been found to be uncomfortable for many users due to a mismatch between vergence and accommodation ("vergence- accommodation conflict") which must be overcome to perceive the images in three dimensions. Indeed, some users are not able to tolerate stereoscopic configurations. These limitations apply to VR/AR/MR systems. Accordingly, most conventional VR/AR/MR systems are not optimally suited for presenting a rich, binocular, three-dimensional experience in a manner that will be comfortable and maximally useful to the user, in part because prior systems fail to address some of the fundamental aspects of the human perception system, including the vergence- accommodation conflict.

0009[0005] Full VR/AR/MR systems must also be capable of displaying virtual digital content at various perceived positions and distances relative to the user. The design of VR/AR/MR systems also presents numerous other challenges, including the speed of the system in delivering virtual digital content, quality of virtual digital content, eye relief of the user (addressing the vergence-accommodation conflict), size and portability of the system, and other system and optical challenges.

0010[0006] One possible approach to address these problems (including the vergence-accommodation conflict) is to project images at multiple depth planes. To implement this type of system, one approach is to use a large number of optical elements (e.g., light sources, prisms, gratings, filters, scan-optics, beam-splitters, mirrors, half-mirrors, shutters, eye pieces, etc.) to project images at a sufficiently large number (e.g., six) of depth planes. The problem with this approach is that using a large number of components in this manner necessarily requires a larger form factor than is desirable, and limits the degree to which the system size can be reduced. The large number of optical elements in these systems also results in a longer optical path, over which the light and the information contained therein can be degraded. These design issues result in cumbersome systems which are also power intensive. The systems and methods described herein are configured to address these challenges by presenting a fixed-distance mixed reality optical system.

0011Summary

0012[0007] In one embodiment, a fixed-distance display system includes a light source configured to generate a light beam. The system also includes a light guiding optical element configured to propagate at least a portion of the light beam by total internal reflection. The system further includes a first inertial measurement unit configured to measure a first value for calculating a head pose of a user. Moreover, the system includes a camera configured to capture an image for machine vision optical flow analysis. The display system is configured to display virtual images only within a tolerance range of a single predetermined optical plane.

0013[0008] In one or more embodiments, the first inertial measurement unit is disposed adjacent the user's head. The system may also include a second inertial measurement unit configured to measure a second value for calculating the head pose of the user. The second inertial measurement unit may be disposed adjacent the user's head. The system may also include a third inertial measurement unit configured to measure a third value for calculating a body pose of the user. The third inertial measurement unit may be disposed adjacent the user's waist. The first inertial measurement unit, the second inertial measurement unit, the third inertial measurement unit, and the camera may be configured to match a field of view of the fixed-distance display system to the user's body position. [0009] In one or more embodiments, the tolerance range is within 0.2 diopters to 0.6 diopters of the single predetermined optical plane. The display system may be configured to display three dimensional virtual images. The display system may be configured to display the three dimensional virtual images having dimensions that do not exceed 0.2 diopters to 0.6 diopters.

0014[0010] In another embodiment, a display method includes measuring a first value relating to a head pose. The method also includes calculating the head pose of a user based on the first value. The method further includes capturing an image. Moreover, the method includes performing machine vision optical flow analysis based on the image. In addition, the method includes generating a light beam. The method also includes propagating at least a portion of the light beam by total internal reflection. The method further includes displaying virtual images only within a tolerance range of a single predetermined optical plane.

0015[0011] In one or more embodiments, the method also includes measuring a second value relating to the head pose. The method may further include calculating the head pose of the user from the first value and the second value. Moreover, the method may include measuring a third value relating to a body pose. In addition, the method may include calculating the body pose of the user from the third value. The method may also include analyzing the first value, the second value, the third value, and the image to match a field of view of the user to the user's body position.

0016[0012] In one or more embodiments, the tolerance range is within 0.2 diopters to 0.6 diopters of the single predetermined optical plane. The method may also include displaying three dimensional virtual images. The displayed three dimensional virtual images may have dimensions that do not exceed 0.2 diopters to 0.6 diopters. [0013] In still another embodiment, a computer program product embodied in a non-transitory computer readable medium, the computer readable medium having stored thereon a sequence of instructions which, when executed by a processor causes the processor to execute a method for displaying, the method includes generating a light beam. The method also includes propagating at least a portion of the light beam by total internal reflection. The method further includes measuring a first value relating to a head pose. Moreover, the method includes calculating the head pose of a user based on the first value. In addition, the method includes capturing an image. The method also includes performing machine vision optical flow analysis based on the image. The method further includes displaying virtual images only within a tolerance range of a single predetermined optical plane.

0017[0014] In yet another embodiment, a body-centric display method includes measuring a first value relating to a head pose. The method also includes calculating the head pose of a user based on the first value. The method further includes measuring a second value relating to a body pose. Moreover, the method includes calculating the body pose of the user from the second value. In addition, the method includes generating a virtual image configured to be displayed only within a tolerance range of a single predetermined optical plane based on the head pose and the body pose. The method also includes displaying the virtual image only within the tolerance range of the single predetermined optical plane.

0018Brief Description of the Drawings

0019[0015] The drawings illustrate the design and utility of various embodiments of the present invention. It should be noted that the figures are not drawn to scale and that elements of similar structures or functions are represented by like reference numerals throughout the figures. In order to better appreciate how to obtain the above-recited and other advantages and objects of various embodiments of the invention, a more detailed description of the present inventions briefly described above will be rendered by reference to specific embodiments thereof, which are illustrated in the accompanying drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:

0020[0016] Figure 1 is a diagram depicting the focal planes of a multiple-plane focus full optical system;

0021[0017] Figure 2 is a diagram depicting the focal plane of a single-plane focus fixed-distance optical system according to one embodiment;

0022[0018] Figures 3 and 4 are schematic views of respective fields-of-view of a user of single-plane focus fixed-distance optical systems according to two embodiments;

0023[0019] Figure 5 is a detailed schematic view of an optical system according to one embodiment;

0024[0020] Fig. 6 is a detailed schematic view of a light-guiding optical element of an optical system according to one embodiment;

0025[0021] Fig. 7 is a detailed perspective view of a light-guiding optical element of an optical system according to one embodiment;

0026[0022] Figures 8A to 8D and 9A to 9D are schematic views of augmented reality/user identification systems according to various embodiments;

0027[0023] Figure 10 is a detailed schematic view of a multiple-plane focus full augmented reality system; [0024] Figures 1 1 and 12 are detailed schematic views of single-plane focus fixed-distance augmented reality systems according to two embodiments;

0028[0025] Figure 13 illustrates a field-of-view of a user of a single-plane focus fixed-distance augmented reality system according to one embodiment;

0029[0026] Figure 14 illustrates the field-of-view of the user of the single-plane focus fixed-distance augmented reality system according to the embodiment depicted in Figure 13 after the user's head has rotated relative to the user's body;

0030[0027] Figures 15 and 16 are flow charts depicting methods for displaying a virtual object in a body-centric manner to a user of a single-plane focus fixed- distance augmented reality system according to two embodiments.

0031Detailed Description

0032[0028] Various embodiments of the invention are directed to systems, methods, and articles of manufacture for implementing fixed-distance mixed reality optical systems in a single embodiment or in multiple embodiments. Other objects, features, and advantages of the invention are described in the detailed description, figures, and claims.

0033[0029] Various embodiments will now be described in detail with reference to the drawings, which are provided as illustrative examples of the invention so as to enable those skilled in the art to practice the invention. Notably, the figures and the examples below are not meant to limit the scope of the present invention. Where certain elements of the present invention may be partially or fully implemented using known components (or methods or processes), only those portions of such known components (or methods or processes) that are necessary for an understanding of the present invention will be described, and the detailed descriptions of other portions of such known components (or methods or processes) will be omitted so as not to obscure the invention. Further, various embodiments encompass present and future known equivalents to the components referred to herein by way of illustration.

0034[0030] The optical systems may be implemented independently of AR/MR systems, but many embodiments below are described in relation to AR/MR systems for illustrative purposes only.

0035Summary of Problem and Solution

0036[0031] One type of optical system for generating virtual images at various depths includes numerous optical components (e.g., light sources, prisms, gratings, filters, scan-optics, beam-splitters, mirrors, half-mirrors, shutters, eye pieces, etc.) that increase in number, thereby increasing the complexity, size and cost of VR/AR/MR systems, as the quality of the 3-D experience/scenario (e.g., the number of imaging planes) and the quality of images (e.g., the number of image colors) increases. The increasing size of optical systems with increasing 3-D scenario/image quality imposes a limit on the minimum size of VR/AR/MR systems resulting in cumbersome systems with reduced optical efficiency.

0037[0032] The following disclosure describes various embodiments of systems and methods for creating 3-D perception around a single predetermined distance using a single-plane focus optical element for each eye that address the problem, by providing optical systems with fewer components and increased efficiency. In particular, the systems described herein utilize a minimal set of optical system components to provide an optical system for displaying virtual objects at a predetermined distance from a user for mixed reality scenarios. This optical system design simplifies and reduces the size of VR/AR/MR systems by limiting the function of such systems to displaying virtual objects at a predetermined distance.

0038Full Augmented Reality Systems [0033] Before describing the details of embodiments of fixed-distance mixed reality optical systems, this disclosure will now provide a brief description of related full AR/MR systems, which are configured to present a full AR scenario with virtual objects appearing at a plurality of positions along a user's optical axis (e.g., from infinity to adjacent the user). Mixed reality optical systems (full and/or fixed-distance) may be implemented independently of AR/MR systems, but many systems below are described in relation to AR/MR systems for illustrative purposes only. Various augmented reality display systems have been discussed in co-owned U.S. Utility Patent Application Serial Number 14/555,585 filed on November 27, 2014 under attorney docket number ML-3001 1 -US and entitled "VI RTUAL AND AUGMENTED REALITY SYSTEMS AND METHODS," the contents of which are hereby expressly and fully incorporated herein by reference as though set forth in full.

0039[0034] One possible approach to implementing a full AR/MR system uses, for each eye of a user, a plurality of volume phase holograms, surface-relief holograms, or light-guiding optical elements ("LOE") that are embedded with depth plane information to generate images that appear to originate from respective depth planes. In other words, a diffraction pattern, or diffractive optical element ("DOE") may be embedded within or imprinted upon an LOE such that as collimated light (light beams with substantially planar wavefronts) is substantially totally internally reflected along the LOE, it intersects the diffraction pattern at multiple locations and at least partially exits toward the user's eye. The DOEs are configured so that light exiting therethrough from an LOE are verged so that they appear to originate from a particular depth plane. The collimated light may be generated using an optical condensing lens (a "condenser"). [0035] For example, a first LOE may be configured to deliver collimated light to the eye that appears to originate from the optical infinity depth plane (0 diopters). Another LOE may be configured to deliver collimated light that appears to originate from a distance of 2 meters (1/2 diopter). Yet another LOE may be configured to deliver collimated light that appears to originate from a distance of 1 meter (1 diopter). By using a stacked LOE assembly, it can be appreciated that multiple depth planes may be created, with each LOE configured to display images that appear to originate from a particular depth plane. It should be appreciated that the stack may include any number of LOEs. However, at least N stacked LOEs are required to generate N depth planes. Further, N, 2N or 3N stacked LOEs may be used to generate RGB colored images at N depth planes.

0040[0036] In order to present virtual content in a full 3-D AR scenario to a user, the full AR/MR system projects images of the virtual content into the user's eye so that they appear to originate from various depth planes in the Z direction (i.e., orthogonally away from the user's eye). In other words, the virtual content may not only change in the X and Y directions (i.e., in a 8D plane orthogonal to a central visual axis of the user's eye), but it may also appear to change in the Z direction such that the user may perceive an object to be very close or at an infinite distance or any distance in between. In full AR/MR systems, the user may perceive multiple objects simultaneously at different depth planes. For example, the user may see a virtual dragon appear from infinity and run towards the user. Alternatively, the user may simultaneously see a virtual bird at a distance of 3 meters away from the user and a virtual coffee cup at arm's length (about 1 meter) from the user.

0041[0037] Multiple-plane focus full AR/MR systems create a perception of variable depth by projecting images on some or all of a plurality of depth planes located at respective fixed distances in the Z direction from the user's eye. Referring now to Figure 1 , it should be appreciated that multiple-plane focus full AR/MR systems typically display frames at fixed depth planes 202 (e.g., the six depth planes 202 shown in Figure 1 ). One exemplary multiple-plane focus full AR/MR system has six fixed depth planes 202 in the Z direction. In generating virtual content at one or more of the six depth planes 202, 3-D perception is created such that the user perceives one or more virtual objects at varying distances from the user's eye. Given that the human eye is more sensitive to objects that are closer in distance than objects that appear to be far away, more depth planes 202 are generated closer to the eye, as shown in Figure 1 . In other systems, the depth planes 202 may be placed at equal distances away from each other.

0042[0038] Depth plane positions 202 are typically measured in diopters, which is a unit of optical power equal to the inverse of the focal length measured in meters. For example, in one system, depth plane 1 may be 1 /3 diopters away, depth plane 2 may be 0.3 diopters away, depth plane 3 may be 0.2 diopters away, depth plane 4 may be 0.15 diopters away, depth plane 5 may be 0.1 diopters away, and depth plane 6 may represent infinity (i.e. , 0 diopters away). It should be appreciated that other systems may generate depth planes 202 at other distances/diopters. Thus, in generating virtual content at strategically placed depth planes 202, the user is able to perceive virtual objects in three dimensions. For example, the user may perceive a first virtual object as being close to him when displayed in depth plane 1 , while another virtual object appears at infinity at depth plane 6. Alternatively, the virtual object may first be displayed at depth plane 6, then depth plane 5, and so on until the virtual object appears very close to the user. It should be appreciated that the above examples are significantly simplified for illustrative purposes. In another system, all six depth planes may be concentrated on a particular focal distance away from the user. For example, if the virtual content to be displayed is a coffee cup half a meter away from the user, all six depth planes could be generated at various cross-sections of the coffee cup, giving the user a highly granulated 3-D view of the coffee cup.

0043[0039] In one system, the full AR/MR system may work as a multiple-plane focus system. In other words, all six LOEs may be illuminated simultaneously, such that images appearing to originate from six fixed depth planes are generated in rapid succession with the light sources rapidly conveying image information to LOE 1 , then LOE 2, then LOE 3 and so on. For example, a portion of the desired image, comprising an image of the sky at optical infinity may be injected at time 1 and the LOE 1090 retaining collimation of light (e.g., depth plane 6 from Figure 1 ) may be utilized. Then an image of a closer tree branch may be injected at time 2 and an LOE 1090 configured to create an image appearing to originate from a depth plane 10 meters away (e.g., depth plane 5 from Figure 1 ) may be utilized; then an image of a pen may be injected at time 3 and an LOE 1090 configured to create an image appearing to originate from a depth plane 1 meter away may be utilized. This type of paradigm can be repeated in rapid time sequential (e.g., at 360 Hz) fashion such that the user's eye and brain (e.g., visual cortex) perceives the input to be all part of the same image.

0044[0040] Full AR/MR systems are required to project images (i.e., by diverging or converging light beams) that appear to originate from various locations along the Z axis (i.e., depth planes) to generate images for a full 3-D experience. As used in this application, "light beams" include, but are not limited to, directional projections of light energy (including visible and invisible light energy) radiating from a light source. Generating images that appear to originate from various depth planes conforms or synchronizes the vergence and accommodation of the user's eye for that image, and minimizes or eliminates vergence-accommodation conflict.

0045[0041] The full AR scenario functional requirement to project images that appear to originate from various depth planes imposes minimum complexity, size and cost limitations on full AR/MR systems. The fixed-distance AR/MR systems described herein avoid these limitations by reducing the function of the system.

0046Fixed-Distance Augmented Reality Systems

0047[0042] Fixed-distance AR/MR systems are configured to display virtual objects near/adjacent (i.e., within about 0.2 diopters to about 0.6 diopters from) a single predetermined distance in the Z direction away from the user (i.e., "depth plane") for a partial AR experience/scenario. Referring now to Figure 2, it should be appreciated that single-plane focus fixed-distance AR/MR systems typically display frames at one fixed depth plane 202. The visual effect for a user of a fixed-distance AR/MR system is that the user is presented with a virtual dome of displayed images in front of and centered on the user. The dome 206 is represented as 2-D arc in Figure 3, where the virtual dome 206 of displayed images is in front of the user. While a user may have a stationary left to right field of view ("FOV") 208 of about 50°, effective L/R FOV will be about 180° due to head rotation, as shown in Figure 3 in a "body-centric" system (described below). In addition, the user's FOV can cover the entire dome 206 with up and down head movement. Accordingly, a fixed- distance AR/MR system can present image information to a user over the entire dome 206 surrounding the user 204. In another embodiment with a stationary user having freedom of body and head rotation, the effective FOV can be an entire sphere 209, as shown in Figure 4. While Figures 3 and 4 represents the dome 206 and sphere 209 of images presented by a fixed-distance AR/MR system in 2-D, it should be understood that the dome 206 and sphere 209 are three dimensional surfaces.

0048[0043] Fixed-distance AR/MR systems can be implemented with, for each eye, a single volume phase hologram, surface-relief hologram, or light-guiding optical element ("LOE") embedded with depth plane information to generate images that appear to originate within a tolerance range of (e.g., within about 0.2 diopters to about 0.6 diopters from) the predetermined depth plane. Fixed-distance AR/MR systems can generate a 3-D effect by using stereoscopic technique (i.e., displaying respective images for each eye at slightly different distances in the Z direction within a tolerance range of the predetermined distance).

0049[0044] While the human visual system is very accurate with respect to vergence, it has some tolerance for differences in accommodation (i.e., focus) before vergence-accommodation reflex related problems arise. Though specific to a particular user, tolerance/uncertainty in accommodation typically occurs between about 0.2 diopters to about 0.6 diopters relative to vergence. Accordingly, the fixed- distance AR/MR systems disclosed herein take advantage of the human visual system's tolerance for differences in accommodation to display 3-D objects near a single predetermined distance in the Z direction, in particular at ranges beyond a user's arm length.

0050[0045] Because a diopter is the inverse of distance from a user's eye (see

0051Figure 1 ), the tolerance/uncertainty in accommodation, which is constant in diopters, varies in terms of linear distance. For illustrative purposes, at a first distance of 1 .00 m (= 1 .0 diopter) from a user, adding 0.2 diopters (the lower range of typical tolerances) would result in a second distance of 0.83 m, a change of -17 cm. Similarly, 0.2 diopters in the opposite direction corresponds to a distance of 1 .25 m, for a total range of 0.83 m to 1 .25 m for content to be viewed within accommodation tolerances of 0.2 diopters if displayed at 1 .00 m (in other words, a range of 42 cm for a fixed-distance AR/MR system to display content at 1 .00 m within tolerance of 0.2 diopters).

0052[0046] On the other hand, for a first distance of 0.50 m (= 2.0 diopters) from a user, adding 0.6 diopters would result in a second distance of 0.38 m, a change of - 12 cm. Moving a corresponding 0.6 diopters away from the 0.50 m first distance results in a distance of 0.71 m, a change of 21 cm or a total range of 33 cm for a fixed AR/MR system to display content at 0.5 m within tolerances of 0.6 diopters. As compared to the 42 cm range of a 1 .00 m fixed-distance AR/MR system with 0.2 diopter tolerance, tripling the tolerance to 0.6 (the other extreme of diopter tolerance) actually decreased the range of content projection for the nearer 0.5 m first distance system. Accordingly, a fixed distance system with more precise (i.e. lower) accommodation tolerances will have greater functional ranges for displaying content at fixed distances further from a user

0053[0047] A fixed-distance AR/MR system employing the tolerance ranges of the present invention around a single optical plane can greatly simplify functionality if content display/rendering is permitted only when such content would appear within certain ranges of a predetermined optical place from a user, preferably at larger distances to maximize tolerance ranges across different users. Similarly, in some embodiments, certain content may be configured to only appear within certain ranges if the optical power establishing the position of a predetermined optical plane of the fixed-distance AR/MR system is known, or a user's particular preferred tolerance is determined. [0048] Table 1 depicts ranges relative to a predetermined optical plane at a fixed-distance from a user that permit content display within diopter tolerances according to some embodiments. Table 1 illustrates the tight ranges that content may be displayed for near-to-user optical planes (see the 0.5 m predetermined optical plane distances), regardless of diopter tolerances, as opposed to the further optical planes that enable greater ranges of content display.

0054<img file="WO2018026737A1_D0001.tif" />

0055[0049] Table 1 1n some embodiments, a tolerance range for a fixed-distance AR/MR system can set rendering domains, such that content that does not appear within a range will not render and thus will save battery life, or content can specifically be programmed to appear within certain distances from a user so as to remain within tolerances of the predetermined optical plane.

0056[0050] In some embodiments, a user may elect a tolerance, either by a functionality (i.e. choosing a fixed-distance AR embodiment that practically would only need to render content within certain distances, for example a virtual computer screen), or by prescription (i.e. recognizing that the user experiences discomfort when exceeding certain diopter tolerances). Such election is akin to selecting customized and simplified AR devices for a particular setting, as opposed to a more complex AR/MR system intended to serve all use cases.

0057[0051] Figure 5 depicts portions of a fixed-distance optical system 100 for projecting images at a single depth plane. The system 100 includes a light source 120 and an LOE 190 having a diffractive optical element (not shown) and an in- coupling grating 192 ("ICG") associated therewith. The diffractive optical elements may be of any type, including volumetric or surface relief. In one embodiment, the ICG 192 can be a reflection-mode aluminized portion of the LOE 190. In another embodiment, the ICG 192 can be a transmissive diffractive portion of the LOE 190. When the system 100 is in use, a "virtual" light beam 210 from the light source 120 enters the LOE 190 via the ICG 192 and propagates along the LOE 190 by substantially total internal reflection ("TI R") for display to an eye of a user. The light beam 210 is "virtual" because it encodes an image of a non-existent "virtual" object or a portion thereof as directed by the system 100. It is understood that although only one beam 210 is illustrated in Figure5, a multitude of beams, which encode an image, may enter the LOE 190 from a wide range of angles through the same ICG 192. The range of angles of entry is related to the FOV achievable for the system 100. A light beam "entering" or being "admitted" into an LOE includes, but is not limited to, the light beam interacting with the LOE so as to propagate along the LOE by substantially TIR. The system 100 depicted in Figure5 can include various light sources 120 (e.g., LEDs, OLEDs, lasers, and masked broad-area/broad-band emitters). In other embodiments, light from the light source 120 may also be delivered to the LOE 190 via fiber optic cables (not shown).

0058[0052] As shown in Figure 6, a portion of the LOE 190 in a fixed-distance optical system 100 can function as an exit pupil expander 196 ("EPE") to increase the numerical aperture of a light source 120 in the Y direction, thereby increasing the resolution of the system 100. Since the light source 120 produces light of a small diameter/spot size, the EPE 196 expands the apparent size of the pupil of light exiting from the LOE 190 to increase the system resolution. The system 100 may further comprise an orthogonal pupil expander 194 ("OPE") in addition to an EPE 196 to expand the light in both the X (OPE) and Y (EPE) directions. More details about the EPEs 196 and OPEs 194 are described in the above-referenced U.S. Utility Patent Application Serial Number 14/555,585, the contents of which have been previously incorporated by reference.

0059[0053] Figure 6 depicts an LOE 190 having an ICG 192, an OPE 194 and an EPE 196. Figure 6 depicts the LOE 190 from a top view that is similar to the view from a user's eyes. The ICG 192, OPE 194, and EPE 196 may be any type of DOE, including volumetric or surface relief. The ICG 192 is a DOE (e.g., a linear grating) that is configured to admit a virtual light beam 210 from a light source 120 for propagation by TIR. In the system 100 depicted in Figure 6, the light source 120 is disposed to the side of the LOE 190.

0060[0054] The OPE 194 is a DOE (e.g., a linear grating) that is slanted in the lateral plane (i.e., perpendicular to the light path) such that a virtual light beam 210 that is propagating through the system 100 will be deflected by 90 degrees laterally. The OPE 194 is also partially transparent and partially reflective along the light path, so that the light beam 210 partially passes through the OPE 194 to form multiple (e.g., eleven) beamlets 210'. In the depicted system 100, the light path is along an X axis, and the OPE 194 configured to bend the beamlets 210' to the Y axis.

0061[0055] The EPE 196 is a DOE (e.g., a linear grating) that is slanted in a Z plane (i.e., normal to the X and Y directions) such that the beamlets 210' that are propagating through the system 100 will be deflected by 90 degrees in the Z plane and toward a user's eye. The EPE 196 is also partially transparent and partially reflective along the light path (the Y axis), so that the beamlets 210' partially pass through the EPE 196 to form multiple (e.g., seven) beamlets 210'. Only select beams 210 and beamlets 210' are labeled for clarity.

0062[0056] The OPE 194 and the EPE 196 are both also at least partially transparent along the Z axis to allow real-world light (e.g., reflecting off real-world objects) to pass through the OPE 194 and the EPE 196 in the Z direction to reach the user's eyes. For AR/MR systems 100, the ICG 192 is at least partially transparent along the Z axis also at least partially transparent along the Z axis to admit real-world light.

0063[0057] Figure 7 depicts another fixed-distance optical system 100 including an LOE 190 having an ICG 192, an OPE 194, and an EPE 196. The system 100 also includes a light source 120 configured to direct a virtual light beam 210 into the LOE 190 via the ICG 192. The light beam 210 is divided into beamlets 210' by the OPE 194 and the EPE 196 as described with respect to Figure 6 above. Further, as the beamlets 210' propagate through the EPE 196, they also exit the LOE 190 via the EPE 196 toward the user's eye. In the system 100 depicted in Figure 7, the light source 120 is disposed orthogonal to the LOE 190. Only select beams 210 and beamlets 210' are labeled for clarity. Fixed-distance mixed reality optical systems may be implemented independently of AR/MR systems, but many systems herein are described in relation to AR/MR systems for illustrative purposes only.

0064[0058] Referring now to Figures 8A-8D, some general AR/MR system component options are illustrated. As shown in Figure 8A, a head-mounted device user 60 is depicted wearing a frame 64 structure coupled to a display system 62 positioned in front of the eyes of the user 60. The following describes possible components of a general AR/MR system. The described components are not all necessary to implement a fixed-distance AR/MR system.

0065[0059] Although not needed to implement a fixed-distance AR/MR system, a speaker 66 may be coupled to the frame 64 in the depicted configuration and positioned adjacent the ear canal of the user 60. In an alternative embodiment, another speaker (not shown) is positioned adjacent the other ear canal of the user 60 to provide for stereo/shapeable sound control. In one or more embodiments, the fixed-distance AR/MR system may have a display 62 that is operatively coupled, such as by a wired lead or wireless connectivity, to a local processing and data module 70, which may be mounted in a variety of configurations, such as fixedly attached to the frame 64, fixedly attached to a helmet or hat 80 as shown in the embodiment depicted in Figure 8B, embedded in headphones, removably attached to the torso 82 of the user 60 in a backpack-style configuration as shown in the embodiment of Figure 8C, or removably attached to the hip 84 of the user 60 in a belt-coupling style configuration as shown in the embodiment of Figure 8D.

0066[0060] The local processing and data module 70 may comprise a power- efficient processor or controller, as well as digital memory, such as flash memory, both of which may be utilized to assist in the processing, caching, and storage of data. The data may be captured from sensors which may be operatively coupled to the frame 64, such as image capture devices (such as cameras), and inertial measurement units (including accelerometers and gyroscopes). Optional sensors, which are not needed to implement a fixed-distance AR/MR system, include compasses, microphones, GPS units, and radio devices. Alternatively or additionally, the data may be acquired and/or processed using the remote processing module 72 and/or remote data repository 74, possibly for passage to the display 62 after such processing or retrieval. The local processing and data module 70 may be operatively coupled 76, 78, such as via a wired or wireless communication links, to the remote processing module 72 and the remote data repository 74 such that these remote modules 72, 74 are operatively coupled to each other and available as resources to the local processing and data module 70.

0067[0061] In one embodiment, the remote processing module 72 may comprise one or more relatively powerful processors or controllers configured to analyze and process data and/or image information. In one embodiment, the remote data repository 74 may comprise a relatively large-scale digital data storage facility, which may be available through the internet or other networking configuration in a "cloud" resource configuration. In one embodiment, all data is stored and all computation is performed in the local processing and data module, allowing fully autonomous use from any remote modules.

0068[0062] In one or more embodiments, a head-worn fixed-distance AR/MR system similar to the ones shown in Figures 8A-8D may be used to display virtual images to a user within a tolerance range of a predetermined distance from the user. It should be appreciated that while a number of the embodiments described below may be implemented in head-worn systems, other embodiments may be implemented in stationary devices. For illustrative purposes, the disclosure will mainly focus on head-worn fixed-distance AR/MR system, but it should be appreciated that the same principles may be applied to non-head-worn and non-AR embodiments as well.

0069[0063] In one or more embodiments, the fixed-distance AR/MR system is typically fitted for a particular user's head, and the optical components are aligned to the user's eyes. These configuration steps may be used in order to ensure that the user is provided with an optimum augmented reality experience without causing any physiological side-effects, such as headaches, nausea, discomfort, etc. Thus, in one or more embodiments, the user-worn fixed-distance AR/MR system is configured (both physically and digitally) for each individual user, and a set of programs may be calibrated specifically for the user. In other scenarios, a loose fitting AR device may be used comfortably by a variety of users. For example, in some embodiments, the user worn fixed-distance AR/MR system knows a distance between the user's eyes, a distance between the head worn display and the user's eyes, and a curvature of the user's forehead. All of these measurements may be used to provide a head- worn fixed-distance AR/MR system customized to fit a given user. In other embodiments, such measurements may not be necessary in order to perform the AR display functions.

0070[0064] For example, referring to Figures 9A-9D, the fixed-distance AR/MR system may be customized for each user. The user's head shape 402 may be taken into account when fitting the head-mounted user-worn user identification system, in one or more embodiments, as shown in Figure 9A. Similarly, the eye components 404 (e.g., optics, structure for the optics, etc.) may be rotated or adjusted for the user's comfort both horizontally and vertically, or rotated for the user's comfort, as shown in Figure 9B. In one or more embodiments, as shown Figure 9C, a rotation point of the head set with respect to the user's head may be adjusted based on the structure of the user's head. Similarly, the inter-pupillary distance (IPD) (i.e., the distance between the user's eyes) may be compensated for, as shown in Figure 9D.

0071[0065] Referring now to Figure 10, the various components of an exemplary full AR/MR system will be described. It should be appreciated that a fixed-distance AR/MR system will have fewer components than a full AR/MR system. However, describing an exemplary full AR/MR system will illustrate the interconnections and functions of the components of a fixed-distance AR/MR system. Figure 10 provides a basic idea of the various components of an AR/MR system or AR device. Figure 10 shows a simplified version of the head-mounted AR/MR system 62 in the block diagram to the right for illustrative purposes.

0072[0066] Referring to Figure 10, one embodiment of a suitable user display device 62 is shown, comprising a display lens 106 which may be mounted to a user's head or eyes by a housing or frame 108. The user display device 62 is a full AR/MR system that is configured to perform a variety of functions, including displaying 3-D virtual objects to a user that appear at various distances away from the user. The display lens 106 may comprise one or more transparent mirrors positioned by the housing 84 in front of the user's eyes 20 and configured to bounce projected light 38 into the eyes 20 and facilitate beam shaping, while also allowing for transmission of at least some light from the local environment. In the depicted embodiment, two wide-field-of-view machine vision cameras 16 are coupled to the housing 108 to image the environment around the user; in one embodiment these cameras 16 are dual capture visible light/infrared light cameras. The depicted system also comprises a pair of scanned-laser shaped-wavefront (i.e., for depth) light projector modules 18 (e.g., spatial light modulators such as DLP, fiber scanning devices (FSDs), LCDs, etc.) with display mirrors and optics configured to project light 38 into the eyes 20 as shown.

0073[0067] While not necessary to implement a fixed-distance AR/MR systems, the depicted full AR/MR system also comprises two miniature infrared cameras 24 paired with infrared light sources 26 (such as light emitting diodes or "LEDs"), which are configured to track the eyes 20 of the user to support rendering and user input. These infrared cameras 24 are also configured to continuously and dynamically capture images of the user's eyes, especially the iris thereof, which can be utilized in user identification.

0074[0068] The system further features a sensor assembly 39, which may comprise X, Y, and Z axis accelerometer capability as well as a magnetic compass and X, Y, and Z axis gyro capability, preferably providing data at a relatively high frequency, such as 200 Hz. An exemplary sensor assembly 39 is an inertial measurement unit ("IMU"). The depicted system 62 also comprises a head pose processor 36 ("image pose processor"), such as an ASIC (application specific integrated circuit), FPGA (field programmable gate array), and/or ARM processor (advanced reduced-instruction-set machine), which may be configured to calculate real or near-real time user head pose from wide field of view image information output from the capture devices 16. The head pose processor 36 is operatively coupled (90, 92, 94; e.g., via wired or wireless connectivity) to the cameras 16 and the rendering engine 34.

0075[0069] Also shown is another processor 32 ("sensor pose processor") configured to execute digital and/or analog processing to derive pose from the gyro, compass, and/or accelerometer data from the sensor assembly 39. The depicted system also features a GPS (global positioning system) subsystem 37 to assist with pose and positioning. In addition, the GPS may further provide cloud-based information about the user's location. This information may be used for user identification purposes. For example, if the user identification algorithm can narrow the detected user characteristics to two potential user identities, a user's current and historical location data may be used to eliminate one of the potential user identities. [0070] Finally, the depicted system comprises a rendering engine 34 which may feature hardware running a software program configured to provide rendering information local to the user to facilitate operation of the scanners and imaging into the eyes of the user, for the user's view of the world. The rendering engine 34 is operatively coupled 94, 100, 102, 104, 105 (i.e., via wired or wireless connectivity) to the image pose processor 36, the optional eye tracking cameras 24, the projecting subsystem 18, and the sensor pose processor 32 such that rendered light 38 is projected using a scanned laser arrangement 18 in a manner similar to a retinal scanning display. The wavefront of the projected light beam 38 may be bent or focused to coincide with a desired focal distance of the projected light 38.

0076[0071] The optional miniature infrared eye tracking cameras 24 may be utilized to track the eyes to support rendering and user input (e.g., where the user is looking, what depth he is focusing, etc.) As discussed below, eye verge may be utilized to estimate a depth of a user's focus. The GPS 37, and the gyros, compasses and accelerometers in the sensor assembly 39 may be utilized to provide coarse and/or fast pose estimates. The camera 16 images and sensor pose information, in conjunction with data from an associated cloud computing resource, may be utilized to map the local world and share user views with a virtual or augmented reality community and/or user identification system.

0077[0072] While much of the hardware in the display system 62 featured in Figure 10 is depicted directly coupled to the housing 108 which is adjacent the display 106 and the eyes 20 of the user, the hardware components depicted may be mounted to or housed within other components, such as a belt-mounted component, as shown, for example, in Figure 8D. [0073] In one full AR/MR system, all of the components of the system 62 featured in Figure 10 are directly coupled to the display housing 108 except for the image pose processor 36, sensor pose processor 32, and rendering engine 34, and communication between the latter three and the remaining components of the system 62 may be by wireless communication, such as ultra-wideband, or wired communication. The depicted housing 108 preferably is head-mounted and wearable by the user. It may also feature speakers, such as those which may be inserted into the ears of a user and utilized to provide sound to the user.

0078[0074] Having described the general components of the full AR/MR system 62 depicted in Figure 10, a fixed-distance AR/MR system 300 will now be described with reference to Figure 1 1 . The fixed-distance AR/MR system 300 includes a pair of light guiding optical elements 302-I, 302-r configured to receive light from respective light sources (not shown) and direct the received light into a user's left and right eyes, respectively. The light from the light sources can be modulated by respective spatial light modulators (not shown) to include image data corresponding to a 3-D virtual object. For instance, light directed to the left and right LOEs 302-I, 302-r can be encoded with image data corresponding to the same 3-D virtual object from two slightly different points of view. The points of view correspond to the positions of the left and right LOEs 302-I, 302-r, which are calibrated for the user's left and right eyes. Accordingly, the light delivered through the left and right LOEs 302-I, 302-r generates an image of a 3-D virtual object for the user using a stereoscopic technique.

0079[0075] The fixed-distance AR/MR system 300 is configured to generate images of 3-D virtual objects that appear near a fixed-distance away from the user, i.e., the point of vergence of the LOEs 302-I, 302-r. As discussed above, the human visual system has a tolerance/uncertainty in accommodation of about 0.2 diopters to about 0.6 diopters. Because the fixed-distance AR/MR system 300 is configured to focus the images of the 3-D virtual object within that tolerance range of the fixed- distance, the system can display images of 3-D virtual objects without noticeable accommodation and vergence issues.

0080[0076] While the light sources and the spatial light modulators are described as separate components, the spatial light modulators can be parts of the respective light sources. In another embodiment, a single light source and a single spatial light modulator (whether separate or combined) can provide modulated light beams for both the left and right LOEs 302-I, 302-r in a time sequential manner. As long as the light beams are provided at a rate of at least about 60 frames per second per LOE (e.g., 120 frames per second for the single light source embodiment), the fixed- distance AR/MR system 300 can render a 3-D virtual object that smoothly moves with minimal motion artifacts.

0081[0077] To that end, the fixed-distance AR/MR system 300 also includes a controller 304 operatively coupled to the other components of the system 300 to coordinate those components. For instance, the controller 304 may include a 3-D rendering engine to generate image data for the left and right LOEs 302-I, 302-r configured to render a 3-D virtual object and send the data to the respective light sources and spatial light modulators. In single light source/spatial light modulator embodiments, the controller 304 may activate the left LOE 302-I and deactivate the right LOE 302-r when the single light source/spatial light modulator generates light encoded with image data configured for the left LOE 302-I. This would minimize crosstalk between the left and right LOEs 302-I, 302-r and artifacts associated therewith. The controller 304 may be a processor in a head mounted fixed-distance AR/MR system 300. In other embodiments, the controller 304 can be a processor in a mobile computer (e.g., a cell phone) or a portion thereon that is wirelessly connected to the other components of the fixed-distance AR/MR system 300.

0082[0078] The fixed-distance AR/MR system 300 further includes left and right IMUs 306-1, 306-r configured to provide data to determine a head pose of a user/wearer of the head mounted fixed-distance AR/MR system 300. While a single IMU is capable of providing data to determining a user head pose, two IMUs 306-1, 306-r provides additional data, which improves the determination of the head pose. In one embodiment, once the gyroscopes in the left and right I MUs 306-1, 306-r are calibrated, the system 300 will be able to track the direction in which a user's head and eye sockets are pointed. While the depicted embodiment of a fixed-distance AR/MR system 300 does not include eye tracking cameras and IR lights, the left and right IMUs 306-I, 306-r provide a practical estimate of the direction in which a user is looking using head pose.

0083[0079] Moreover, the fixed-distance AR/MR system 300 includes an outwardly facing image capture device 308 (e.g., a camera) to capture images approximating the user's field of view. The image capture device sends the captured image data to the controller 304, which performs machine vision optical flow to correct drift resulting from movement of the system 300 and the image capture device 308, which is coupled to the head-mounted portion of the system 300. The image capture device 308 can be a visible and/or infrared light camera such as a CCD camera.

0084[0080] The fixed-distance AR/MR system 300, using the left and right LOEs

0085302-I, 302-r, the controller 304, the left and right IMUs 306-I, 306-r, and the image capture device 308, can generate and render 3-D images of a virtual object in a field of view a user such that the user can view the 3-D images without noticeable accommodation and vergence issues. The left and right LOEs 302-1, 302-r project images into the left and right eyes respectively. The controller 304 renders the images (to generate a 3-D image for the user). The left and right IMUs 306-1, 306-r provide data the controller 304 uses to determine the user's head pose. The image capture device 308 provides image data used to correct drift in the system 300. The controller 304 uses the data provided by the left and right IMUs 306-1, 306-r and the image capture device 308 to render the appropriate images for the user's left and right eyes based on the head pose of the user and system drift.

0086[0081] In another embodiment, depicted in Figure 12, the fixed-distance AR/MR system 300 also includes left and right LOEs 302-I, 302-r, a controller 304, left and right IMUs 306-I, 306-r, and an image capture device 308. These components are operatively coupled and function as described above for the same components in the fixed-distance AR/MR system 300 depicted in Figure 1 1 . In addition, the fixed-distance AR/MR system 300 depicted in Figure 12 includes a third or "body" IMU 306-b, which is fixed to the user's body (e.g., attached to a user's belt). In other embodiments, the body IMU 306-b is fixed to or a part of the user's cell phone, but the body IMU 306-b is only active when the phone is fixed to the user's belt (e.g., in a holder). The body IMU 306-b is configured to provide data to determine a body pose of a user of the fixed-distance AR/MR system 300. Once the gyroscopes in the body IMU 306-b are calibrated, the system 300 will be able to track the direction in which a user's body is pointed.

0087[0082] The controller 304 uses the data from the body I MU 306-b to generate a "body-centric" fixed-distance AR scenario. For instance, the controller 304 can generate a user interface 506 in a FOV 500 of and at a fixed distance from a user, as shown in Figure 13. Unlike a "head-centric" AR scenario, which is simply an overlay on top of the real world scene that moves with motion of the user's head, a body- centric fixed-distance AR scenario "sticks" the user interface 506 at a fixed distance from and a fixed point relative to the body of the user and moves to a different portion of the user interface 506 when the user's head turns toward that portion. This is accomplished by the controller 304 comparing data from the body IMU 306-b with data from the left and right IMUs 306-1, 306-r to determine the head pose relative to the body pose.

0088Exemplary Virtual Object (User Interface)

0089[0083] Figure 13 depicts a FOV 500 of a user wearing a head-mounted fixed- distance AR/MR system 300, such as the one depicted in Figure 12. The user can see in the FOV 500 a real physical building 502 and a real copse of trees 504. The use can also see in the FOV 500 a user interface 506 generated and rendered by the fixed-distance AR/MR system 300. The user interface 506 has sufficient opacity to allow the user to see the trees 504 behind the user interface 506. This opacity is illustrated by depicting the user interface 506 with broken lines. The user interface 506 includes six user interface objects 508-1 to 508-6. The FOV 500 is limited on the left 510-1 and right 510-r sides by the limitations of the user's eyes. The limited FOV 500 is about 50°.

0090[0084] Figure 14 depicts another FOV 500' of the same user wearing the same head-mounted fixed-distance AR/MR system 300 after the user's head has turned to the left by about 25° relative to the user's body. The building 502 and trees 504 have moved to the right side 510-r of the FOV. In fact, the right half of the building 502 has moved out of the FOV 500'. Because the head-mounted fixed- distance AR/MR system 300 is configured to generate and render a body-centric user interface 506, after turning their head, the user can see a different portion of the user interface 506. For instance, user interface objects 508-a, 508-b and 508-c are visible to the user in FOV 500' depicted in Figure 14, but not in FOV 500 depicted in Figure 13. At the same time, user interface objects 508-4, 508-5 and 508-6 are not visible to the user in FOV 500' depicted in Figure 14, but they are visible in FOV 500 depicted in Figure 13. This ability to scan left and right allow for a larger total effective FOV than the approximately 50° FOV of the human eye. The increase in the total effective FOV is not limited to the left and right directions, but also includes up and down, thereby forming a dome 206 on which the head-mounted fixed- distance AR/MR system 300 may render virtual images (see Figure 3). While Figures 13 and 14 depict a 2-D user interface 506, it should be noted that the virtual image can be a stereoscopically rendered 3-D image as described above.

0091[0085] The fixed-distance AR/MR system 300 described above can perform the function of displaying a virtual object in a body-centric manner while minimizing the complexity, size and cost of the system 300. This economic use of optical system components can result in AR/MR systems (and other optical systems) that are easier to manufacture, more comfortable to use, and more affordable for the typical consumer/user.

0092Body-Centric Display of Virtual Object

0093[0086] Having described several embodiments of fixed-distance AR/MR systems 300, a method 600 of displaying a virtual object (e.g., a user interface 506 as in Figure 14) in a body-centric manner to a user of a fixed-distance AR/MR system 300 will now be discussed. As shown in Figure 15, the method begins at step 602 with measuring a first value relating to a head pose. For instance, the left

0094IMU 306-I (see Figure 14) in the fixed-distance AR/MR system 300 may measure gyroscopic data indicative of a head pose. [0087] At step 604, a head pose is calculated from the first value. For instance, the controller 304 in the fixed-distance AR/MR system 300 may calculate a head pose from the measured gyroscopic data.

0095[0088] At step 606, a second value relating to body pose is measured. For instance, the body IMU 306-b (see Figure 14) in the fixed-distance AR/MR system 300 may measure gyroscopic data indicative of a body pose.

0096[0089] At step 608, a body pose is calculated from the second value. For instance, the controller 304 in the fixed-distance AR/MR system 300 may calculate a body pose from the measured gyroscopic data.

0097[0090] At step 610, a virtual image configured to be displayed within a tolerance range of a single predetermined optical plane is generated based on the head pose and the body pose. For instance, the 3-D rendering engine of the controller 304 in the fixed-distance AR/MR system 300 may render a virtual image configured to be displayed in the FOV of a user based on the user's head pose relative to the user's body pose. The 3-D rendering engine may alter the virtual image generated based on the user's head pose relative to the user's body pose (compare Figures 13 and 14). The virtual image may be a part of the user interface 506 depicted in Figures 13 and 14. The virtual image may be a part of a 3-D image (e.g., the left image of a pair of images configured to render a 3-D image when simultaneously displayed to the left and right eyes of a user).

0098[0091] At step 612, the generated virtual image is displayed within a tolerance range of the single predetermined optical plane. As explained above, displaying the virtual image "adjacent" the single predetermined optical plane includes, but is not limited to, displaying the virtual image within about 0.2 diopters to about 0.6 diopters of the single predetermined optical plane. For instance, the light source, the spatial light modulator, and the left LOE 302-1 (see Figure 14) in the fixed-distance AR/MR system 300 may display the generated virtual image to a user. The single predetermined optical plane may be selected such that the vergence of the user's left eye (based on the angle of the light emitted by the left LOE 302-I) corresponds to the focus of the virtual image within a tolerance range of the single predetermined optical plane. Such correspondence minimizes or eliminates problems related to vergence-accommodation conflict.

0099[0092] Figure 19 depicts another method 600' of displaying a virtual object (e.g., a user interface 506 as in Figure 14) in a body-centric manner to a user of a fixed-distance AR/MR system 300. Steps 602, 604, 606, 608, and 612 are identical to the corresponding steps in the method 600 depicted in Figure 18.

0100[0093] The method 600' depicted in Figure 19 is different from the method 600 depicted in Figure 18 because at optional step 614, an image is captured. For instance, the image acquisition device 308 (see Figure 14) in the fixed-distance AR/MR system 300 may capture an image approximating the FOV of the user.

0101[0094] At optional step 616, machine vision optical flow analysis is performed based on the captured image. The optical flow analysis corrects drift resulting from movement of the system. For instance, the controller 304 in the fixed-distance AR/MR system 300 may perform the machine vision optical flow analysis based on the captured image.

0102[0095] At step 610, a virtual image configured to be displayed within a tolerance range of a single predetermined optical plane is generated based on the head pose, the body pose, and the result of the machine vision optical flow analysis. For instance, the 3-D rendering engine of the controller 304 in the fixed-distance AR/MR system 300 may render a virtual image configured to be displayed in the FOV of a user based on the head pose, the body pose, and the result of the machine vision optical flow analysis. The 3-D rendering engine may alter the virtual image generated based on the user's head pose relative to the user's body pose (compare Figures 13 and 14). Including the result of the machine vision optical flow analysis in rendering the virtual image corrects system drift and results in a more accurately rendered virtual image. The virtual image may be a part of the user interface 506 depicted in Figures 13 and 14. The virtual image may be a part of a 3-D image (e.g., the left image of a pair of images configured to render a 3-D image when simultaneously displayed to the left and right eyes of a user).

0103[0096] The above-described fixed-distance AR/MR systems are provided as examples of various common systems that can benefit from reduced complexity, size and cost. Accordingly, use of the fixed-distance optical systems described herein is not limited to the disclosed fixed-distance AR/MR systems, but rather applicable to any optical system.

0104[0097] Various exemplary embodiments of the invention are described herein. Reference is made to these examples in a non-limiting sense. They are provided to illustrate more broadly applicable aspects of the invention. Various changes may be made to the invention described and equivalents may be substituted without departing from the true spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation, material, composition of matter, process, process act(s) or step(s) to the objective(s), spirit or scope of the present invention. Further, as will be appreciated by those with skill in the art that each of the individual variations described and illustrated herein has discrete components and features which may be readily separated from or combined with the features of any of the other several embodiments without departing from the scope or spirit of the present inventions. All such modifications are intended to be within the scope of claims associated with this disclosure.

0105[0098] The invention includes methods that may be performed using the subject devices. The methods may comprise the act of providing such a suitable device. Such provision may be performed by the end user. In other words, the "providing" act merely requires the end user obtain, access, approach, position, setup, activate, power-up or otherwise act to provide the requisite device in the subject method. Methods recited herein may be carried out in any order of the recited events which is logically possible, as well as in the recited order of events.

0106[0099] Exemplary aspects of the invention, together with details regarding material selection and manufacture have been set forth above. As for other details of the present invention, these may be appreciated in connection with the above- referenced patents and publications as well as generally known or appreciated by those with skill in the art. The same may hold true with respect to method-based aspects of the invention in terms of additional acts as commonly or logically employed.

0107[00100] In addition, though the invention has been described in reference to several examples optionally incorporating various features, the invention is not to be limited to that which is described or indicated as contemplated with respect to each variation of the invention. Various changes may be made to the invention described and equivalents (whether recited herein or not included for the sake of some brevity) may be substituted without departing from the true spirit and scope of the invention.

0108In addition, where a range of values is provided, it is understood that every intervening value, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed within the invention. [00101] Also, it is contemplated that any optional feature of the inventive variations described may be set forth and claimed independently, or in combination with any one or more of the features described herein. Reference to a singular item, includes the possibility that there are plural of the same items present. More specifically, as used herein and in claims associated hereto, the singular forms "a," "an," "said," and "the" include plural referents unless the specifically stated otherwise. In other words, use of the articles allow for "at least one" of the subject item in the description above as well as claims associated with this disclosure. It is further noted that such claims may be drafted to exclude any optional element. As such, this statement is intended to serve as antecedent basis for use of such exclusive terminology as "solely," "only" and the like in connection with the recitation of claim elements, or use of a "negative" limitation.

0109[00102] Without the use of such exclusive terminology, the term "comprising" in claims associated with this disclosure shall allow for the inclusion of any additional element-irrespective of whether a given number of elements are enumerated in such claims, or the addition of a feature could be regarded as transforming the nature of an element set forth in such claims. Except as specifically defined herein, all technical and scientific terms used herein are to be given as broad a commonly understood meaning as possible while maintaining claim validity.

0110[00103] The breadth of the present invention is not to be limited to the examples provided and/or the subject specification, but rather only by the scope of claim language associated with this disclosure.

0111[00104] In the foregoing specification, the invention has been described with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention. For example, the above-described process flows are described with reference to a particular ordering of process actions. However, the ordering of many of the described process actions may be changed without affecting the scope or operation of the invention. The specification and drawings are, accordingly, to be regarded in an illustrative rather than restrictive sense.