Short-focus optical system with multi-focus correction

Abstract

An image light guide system that manages focus discrepancies between real-world and virtual objects presented to a viewer, manages vision problems that affect a particular viewer's ability to accommodate focus, and reduces the viewer's ocular requirements to see virtual objects together with real-world objects in the same field of view. The image light guide system includes negative and positive power optical elements positioned to focus virtual objects at less than optical infinity relative to the eyebox while ensuring that the focusing distance of real-world objects in the same field of view remains unchanged. The image light guide system also includes one or more optical elements that provide one or more corrective optical contributions to correct for a particular optical aberration of the viewer.

Description

[Technical field]

[0001] The present disclosure relates generally to an augmented reality system that includes a near-eye display operable to display a virtual image superimposed on a real-world view through the display. [Background technology]

[0002] Head mounted displays (HMDs) are increasingly taking the form of traditional eyeglasses with unobtrusive optics for conveying virtual image content with a less obscured view of the surrounding environment. An image generator may be supported along the eyeglass temples, and a substantially transparent image light guide conveys the generated image to the wearer's eyes as a virtual image projected into the wearer's real-world field of view as seen through the image light guide.

[0003] The virtual image content can be transmitted along the image light guide as a set of angularly related beams, with the relative angular orientation of each beam in the two angular dimensions corresponding to a different location (e.g., pixel) in the generated image. Typically, the beams themselves are collimated as if they correspond to distant point sources located at unique angular locations in the field of view. Thus, when the collimated beams are directed to overlapping locations in a common eyebox, the wearer's eyes see the generated image from the eyebox as a virtual image located at a distance approaching infinity. However, real-world objects of interest to the wearer may be located much closer and require some significant eye accommodation to focus. Viewing virtual and real-world objects requiring different focus accommodations in the same scene can cause eye strain.

[0004] Vision problems in the wearer's eyes caused by refractive errors such as myopia (nearsightedness), hyperopia (farsightedness), and astigmatism can also pose challenges with low-profile HMDs, which resemble traditional eyeglasses. If the wearer's traditional eyeglasses (including corrective lenses) must be removed to accommodate the low-profile HMD, the wearer's view of both real-world and virtual objects through the HMD can be impaired. Summary of the Invention

[0005] The present disclosure is directed to one or more exemplary embodiments of an image light guide system that manages focus discrepancies between real-world objects and virtual objects presented to a viewer, manages vision issues that affect a particular viewer's ability to accommodate focus, and reduces the viewer's ocular requirements to see virtual objects together with real-world objects in the same field of view. The image light guide system includes negative and positive power optical elements positioned to focus virtual objects at less than optical infinity relative to the eyebox while ensuring that the focusing distance of real-world objects in the same field of view remains unchanged. The image light guide system also includes one or more optical elements that provide one or more corrective optical contributions to correct for a viewer's particular optical aberrations.

[0006] These and other aspects, objects, features, and advantages of the present disclosure will be more clearly understood and appreciated from the following detailed description of the embodiments and appended claims, and by reference to the accompanying drawings. In an exemplary embodiment, the present disclosure provides an image light guide system for viewing virtual objects and real-world objects in a common field of view. The image light guide system includes an image light guide having an inner surface and an outer surface, the image light guide arranged to direct an image-bearing light beam of the virtual object toward an eyebox for viewing at a first focused distance from the eyebox (e.g., optical infinity). The image light guide system also includes a negative power optical element arranged between the image light guide and the eyebox, the negative power optical element arranged to diverge the image-bearing light beam before the eyebox for viewing the virtual object at a second focused distance less than the first focused distance (e.g., closer than optical infinity). The image light guide system further includes a non-variable corrective optical element and a positive power optical element. A corrective optical element is disposed between the image light guide and the real world object and is positioned to reduce optical aberrations in a viewer associated with viewing the real world object at the second focusing distance, and a positive output optical element is disposed between the image light guide and the real world object, the positive output optical element being configured to compensate for the negative light output contribution of the negative output optical element without compensating for the corrective optical contribution of the positive output optical element.

[0007] In another exemplary embodiment, the present disclosure provides an image light guide for viewing virtual objects and real-world objects in a common field of view. The image light guide includes an inner surface and an outer surface arranged to direct an image-bearing light beam of a virtual object toward an eyebox at a first focused distance. A first metamaterial has a negative light output contribution configured to diverge the image-bearing light beam in front of the eyebox at a second focused distance that is shorter than the first focused distance. A second metamaterial is arranged to provide a positive light output contribution to counteract the negative light output contribution of the first metamaterial. [Brief description of the drawings]

[0008] The accompanying drawings are incorporated herein as part of this specification. The drawings described herein illustrate embodiments of the subject matter of the present disclosure and illustrate selected principles and teachings of the present disclosure. However, the drawings do not illustrate every possible implementation of the subject matter of the present disclosure and are not intended to limit the scope of the present disclosure in any way. [Figure 1] FIG. 1 is a top view of an image light guide with an exaggerated thickness to illustrate the propagation of light from an image source along the image light guide to an eyebox within which a virtual image can be displayed. [Diagram 2] FIG. 2 is a perspective view of an image light guide that includes an incoupling diffractive optical element, which is a rotating diffractive optical element, and an outcoupling diffractive optical element for managing the propagation of an image-bearing light beam. [Diagram 3] FIG. 3 is a plan schematic diagram of a portion of an image light guide system according to an exemplary embodiment of the disclosed subject matter. [Figure 4] FIG. 4 is a simplified plan view schematic diagram of a portion of an imaging light system showing a common field of view according to an exemplary embodiment of the disclosed subject matter. [Diagram 5] FIG. 5 is a simplified plan schematic diagram of a portion of an imaging light system having a negative power optical element, in accordance with an exemplary embodiment of the disclosed subject matter. [Figure 6] FIG. 6 is a simplified plan schematic diagram of a portion of an imaging light system having negative and positive output optical elements, in accordance with an exemplary embodiment of the disclosed subject matter. [Figure 7] FIG. 7 is a simplified plan schematic diagram of a portion of an imaging light system having a negative output optical element, a positive output optical element, and a corrective optical element, in accordance with an exemplary embodiment of the disclosed subject matter. [Figure 8A] FIG. 8A is a simplified plan schematic diagram of a portion of an imaging light system having a negative power optical element, a positive power optical element, and a multifocal correction optical element, in accordance with an exemplary embodiment of the disclosed subject matter. [Figure 8B]FIG. 8B is a simplified plan view schematic diagram of a portion of an imaging light system having a negative power optical element, a positive power optical element, and a multifocal correction optical element, in accordance with an exemplary embodiment of the disclosed subject matter. [Figure 9] FIG. 9 is a simplified plan schematic diagram of a portion of an imaging light system having a negative power optical element, a positive power optical element, and a multifocal correction optical element, in accordance with an exemplary embodiment of the disclosed subject matter. [Figure 10A] FIG. 10A is a simplified plan schematic diagram of a portion of an imaging light system having a multi-function optical element according to an exemplary embodiment of the disclosed subject matter. [Figure 10B] FIG. 10B is a simplified plan schematic diagram of a portion of an imaging light system having a multi-function optical element according to another exemplary embodiment of the subject matter of the present disclosure. [Figure 11] FIG. 11 is a simplified plan schematic diagram of a portion of an imaging light system having a multi-function optical element and a lens carrier, according to an exemplary embodiment of the subject matter of this disclosure. [Figure 12] FIG. 12 is a simplified planar schematic diagram of a portion of an imaging light system having first and second metamaterials, according to an exemplary embodiment of the disclosed subject matter. [Figure 13] FIG. 13 is a perspective view of an image light guide system in the form of a head mounted display according to an exemplary embodiment of the subject matter of this disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] It should be understood that the present invention may assume various alternative orientations and step arrangements unless expressly specified to the contrary. It should also be understood that the specific assemblies and systems illustrated in the attached drawings and described in the following specification are merely exemplary embodiments of the inventive concepts defined herein. Thus, specific dimensions, orientations, or other physical characteristics relating to the disclosed embodiments are not to be considered as limiting unless expressly stated otherwise. Also, although not applicable, similar elements in the various embodiments described herein may be generally referred to by similar reference numerals within this section of the specification.

[0010] Those skilled in the relevant art will recognize that the elements and techniques described herein can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In some instances, well-known structures, materials, or operations have not been shown or described in detail to avoid obscuring certain aspects of the disclosure. Throughout this specification, references to "one embodiment" or "embodiment" mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the disclosure. Thus, appearances of the phrase "one embodiment" or "an embodiment" throughout this specification do not necessarily refer to the same embodiment. However, certain features, structures, or characteristics described may be combined in any suitable manner in one or more embodiments.

[0011] As used herein, the terms "first," "second," and the like do not necessarily imply any ordering, sequential, or priority relationship, but are used to more clearly distinguish one element or set of elements from another, unless otherwise specified.

[0012] As used herein, the term "exemplary" means "an example of" and is not intended to suggest any preferred or ideal embodiment.

[0013] As used herein, the terms "viewer," "wearer," "operator," "observer," and "user" are equivalent and refer to a person or machine that wears and displays images using an augmented reality system.

[0014] As used herein, the term "coupled" is intended to indicate a physical coupling, connection, relationship, or association between two or more components such that the arrangement of one component affects the spatial arrangement of the components to which it is coupled. For a mechanical coupling, the two components need not be in direct contact, but may be connected through one or more intermediate components. Components for optical coupling allow for the input or output of optical energy to an optical device.

[0015] As used herein, the term "eyebox" is intended to define a two-dimensional region or three-dimensional volume within which an eye or other optical component located anywhere within the eyebox forms one or more focused images.

[0016] FIG. 1 is a schematic diagram showing a simplified cross-sectional view of one conventional configuration of an image light guide system 10. The image light guide system 10 includes a planar image light guide 12, an incoupling diffractive optical element IDO, and an outcoupling diffractive optical element ODO. The image light guide 12 includes a transparent substrate S, which may be made of optical glass or plastic, for example, with plane-parallel front and back surfaces 14 and 16. In this example, the incoupling diffractive optical element IDO is shown as a transmission grating disposed on the front surface 14 of the image light guide 12. However, the incoupling diffractive optical element IDO may alternatively be a reflection grating or other type of diffractive optical element (such as a volume hologram or other holographic diffractive element) that diffracts an incident image-bearing light beam WI into the image light guide 12. The incoupling diffractive optical element IDO may be located on the front surface 14 or back surface 16 of the image light guide 12, and may be a combination of transmission or reflection, depending on the direction in which the image-bearing light beam WI is intended to approach the image light guide 12.

[0017] When used as part of a near-eye display system or a head-mounted display, the incoupling diffractive optical element IDO of the conventional image light guide system 10 couples an image-bearing light beam WI from an image source 18 of a real, virtual or hybrid image into a substrate S of the image light guide 12. Any real or image dimension formed by the image source 18 is first transformed into an array of overlapping, angle-related collimated beams that code for different locations in the virtual image for presentation to the incoupling diffractive optical element IDO. Typically, the light rays in each bundle forming one of the angle-related beams extend parallel, but the angle-related beams are relatively oblique to one another through an angle that may be defined by two angular dimensions corresponding to the linear dimensions of the image.

[0018] When the angle-related beams engage the incoupling diffractive optical element IDO, at least a portion of the image-bearing light beam WI is diffracted (typically by a first diffraction order) and thereby redirected by the incoupling diffractive optical element IDO into the planar image light guide 12 as an angularly coded image-bearing light beam WG for further propagation along the length dimension X of the image light guide 12 by total internal reflection (TIR) ​​between the plane-parallel front surface 14 and back surface 16. Although diffracted into different combinations of angle-related beams along the boundaries set by the TIR, the image-bearing light beam WG preserves the image information in an angle-coded form that is derivable from the parameters of the incoupling diffractive optical element IDO. The outcoupling diffractive optical element ODO receives the coded image-bearing light beam WG and diffracts at least a portion of the image-bearing light beam WG out of the image light guide 12 as an image-bearing light beam WO (typically also by a first diffraction order) towards a nearby spatial region called the eyebox E, in which the transmitted virtual image can be seen by the viewer's eye or other optical components. The outcoupling diffractive optical element ODO can be designed symmetrically with respect to the incoupling diffractive optical element IDO to restore the original angular relationship of the image-bearing light beam WI from between the output angle-related beams of the image-bearing light beam WO. Furthermore, the outcoupling diffractive optical element ODO can modify the angular relationship of the original field point positions to generate an output virtual image at a finite focusing distance.

[0019] However, in order to increase one dimension of overlap between the angle-related beams injected into the eyebox E (which defines the size of the area in which the virtual image can be seen), the outcoupling diffractive optical element ODO is positioned with a limited thickness T of the image light guide 12 to encounter the image-bearing light beam WG multiple times, diffracting only a portion of the image-bearing light beam WG at each encounter. The multiple encounters along the length of the outcoupling diffractive optical element ODO have the effect of replicating the image-bearing light beam WG and enlarging or expanding at least one dimension of the eyebox E where the replicated beams overlap. The expanded eyebox E reduces the sensitivity to the position of the viewer's eyes for seeing the virtual image.

[0020] The outcoupling diffractive optical element ODO is shown as a transmissive diffraction grating located or fixed on the front surface 14 of the image light guide 12. However, like the incoupling diffractive optical element IDO, the outcoupling diffractive optical element ODO may be a combination of transmissive and reflective types depending on the direction in which the image-bearing light beam WG is intended to exit the image light guide 12, located on the front surface 14 or back surface 16 of the image light guide 12. In addition, the outcoupling diffractive optical element ODO may be formed as another type of diffractive optical element, such as a volume hologram or other holographic diffractive element, which diffracts the image-bearing light beam WG propagating from the image light guide 12 as an image-bearing light beam WO propagating towards the eye box E.

[0021] 2 shows a perspective view of a conventional image light guide system 10 arranged to expand the eyebox E in two dimensions, i.e., along both the x-axis and the y-axis of the intended image. To achieve the second dimension of eyebox expansion, the incoupling diffractive optical element IDO is oriented to diffract at least a portion of the image-bearing light beam WG along the image light guide 12 toward the intermediate rotating optical element TO with a grating vector k1, which is oriented to diffract a portion of the image-bearing light beam WG in a reflective mode along the image light guide 12 toward the outcoupling diffractive optical element ODO. It will be appreciated that only a portion of the image-bearing light beam WG is diffracted by each of multiple encounters with the intermediate rotating optical element TO, thereby laterally replicating each of the angle-related beams of the image-bearing light beam WG as it approaches the outcoupling diffractive optical element ODO. The intermediate rotating optical element TO redirects the image-bearing light beam WG towards the outcoupling diffractive optical element ODO (with grating vector k3) to longitudinally replicate the angle-related beam of the image-bearing light beam WG in a second dimension before it exits the image light guide 12 as the image-bearing light beam WO. The depicted grating vectors k1, k2, and k3 extend in a parallel plane of the image light guide 12 in a direction perpendicular to the diffractive features (e.g., grooves, lines, or rulers) of the diffractive optical element and have inverse magnitude to the period or pitch d (i.e., the center-to-center distance between the diffractive features of the diffractive optical element) of the diffractive optical elements IDO, TO, and ODO, respectively.

[0022] As shown in FIG. 2, the incoupling diffractive optical element IDO receives an incoming image-bearing light beam WI, which includes a series of angle-related beams that correspond to individual pixels or equivalent locations in an image generated by an image source 18, such as a projector. The full range of angle-coded beams to generate a virtual image can be generated by a real display device in combination with collimating optics or other optical components, by a beam scanner to set the angle of the beam more directly, or by a combination such as a one-dimensional real display device used with a scanner. In this configuration, the image light guide 12 outputs a series of replicated angle-related beams (replicated in two dimensions) in two dimensions of the image by providing multiple encounters of the image-bearing light beam WG with both the intermediate rotating optical element TO and the outcoupling diffractive optical element ODO at different orientations. In the illustrated orientation of the image light guide 12, the intermediate rotating optical element TO provides an eyebox expansion in the y-axis direction, and the outcoupling diffractive optical element ODO provides a similar eyebox expansion in the x-axis direction. The relative orientations and respective periods d of the diffractive features of the incoupling optical element IDO, the intermediate rotating optical element TO, and the outcoupling diffractive optical element ODO provide eyebox expansion in two dimensions while maintaining the intended relationships between the angularly related beams of the image-bearing light beam WI that are output from the image light guide system 10 as the image-bearing light beam WO. It will be appreciated that the periods d of the incoupling diffractive optical element IDO, the intermediate rotating optical element TO, and the outcoupling diffractive optical element ODO can each include diffractive features having a common pitch d, and the common pitch d of each optical element can be different.

[0023] In the illustrated configuration, the image-bearing light beam WI input to the image light guide 12 is coded by the incoupling diffractive optical element IDO into a series of different angle-related beams, but the information required to reconstruct the image is preserved by taking into account the systematic effects of the incoupling diffractive optical element IDO. The intermediate rotation optical element TO, located at an intermediate position between the incoupling diffractive optical element IDO and the outcoupling diffractive optical element ODO, can be positioned so as not to induce any significant changes to the coding of the image-bearing light beam WG. The outcoupling diffractive optical element ODO can thus be positioned symmetrically with respect to the incoupling diffractive optical element IDO, including, for example, diffractive features sharing the same period d. Similarly, the period of the intermediate rotation optical element TO typically also matches the common period of the incoupling diffractive optical element IDO and the outcoupling diffractive optical element ODO. Although the grating vector k2 of the intermediate rotation optical element TO is shown oriented at 45 degrees relative to the other grating vectors with possible orientations maintained, the grating vector k2 of the intermediate rotation optical element TO can be oriented at 60 degrees relative to the grating vectors k1 and k3 of the incoupling diffractive optical element IDO and the outcoupling diffractive optical element ODO such that the image-bearing light beam WG is rotated by 120 degrees. By orienting the grating vector k2 of the intermediate rotation optical element TO at 60 degrees relative to the grating vectors k1 and k3 of the incoupling diffractive optical element IDO and the outcoupling diffractive optical element ODO, the grating vectors k1 and k3 of the incoupling diffractive optical element IDO and the outcoupling diffractive optical element ODO are also oriented at 60 degrees relative to each other. Taking the common pitch of the incoupling diffractive optical element IDO, the intermediate rotating diffractive optical element TO and the outcoupling diffractive optical element ODO as the basis for the magnitude of the grating vectors, the three grating vectors k1, k2, k3 (as directed line segments) form an equilateral triangle, the sum of which is the magnitude of a zero vector, thereby avoiding asymmetric effects that may result in undesirable aberrations, including chromatic dispersion.Such asymmetric effects can also be avoided by lattice vectors k1, k2, and k3 having unequal magnitudes in relative orientation such that the sum of the three lattice vectors k1, k2, and k3 has the magnitude of a zero vector.

[0024] In a broader sense, the image-bearing light beam WI directed into the image light guide 12 is effectively coded by the incoupling diffractive optical element IDO, regardless of whether the incoupling optics IDO uses a grating, a hologram, a prism, a mirror, or some other mechanism. The reflection, refraction, and / or diffraction of light occurring at the input should be decoded accordingly by the output to recreate the virtual image presented to the viewer. It may be relevant whether any symmetry is maintained between the intermediate rotating optical element TO, the incoupling optics IDO, and the outcoupling diffractive optical element ODO, or whether changes to the angle-related beam coding of the image-bearing light beam WI occur along the image light guide 12, the intermediate rotating optical element TO, the incoupling diffractive optical element IDO, and the outcoupling diffractive optical element ODO, so that the image-bearing light beam WO output from the image light guide 12 retains or otherwise maintains the original or desired form of the image-bearing light beam WI for generating the intended virtual image.

[0025] As shown in FIG. 2, the letter "R" represents the orientation of the virtual image as seen by a viewer with eyes positioned within the eyebox E. As shown, the orientation of the letter "R" of the represented virtual image coincides with the orientation of the letter "R" encoded by the image-bearing light beam WI. A change in rotation about the z-axis or angular orientation of the incident image-bearing light beam WI with respect to the xy-plane causes a corresponding symmetric change in rotation or angular orientation of the exiting light from the outcoupling diffractive optical element (ODO). From the image orientation aspect, the intermediate rotating optical element TO simply acts as a kind of optical relay, providing an expansion of the angle-coded beam of the image-bearing light beam WG along one axis of the image (e.g., along the y-axis). The outcoupling diffractive optical element ODO further expands the angle-coded eyebox of the image-bearing light beam WI along another axis (e.g., along the x-axis) while maintaining the original orientation of the virtual image encoded by the image-bearing light beam WI. The intermediate rotating optical element TO is typically a tilted or square grating, or alternatively may be a blazed grating, and is typically disposed on one of the plane-parallel front and back surfaces of the image light guide 12. Of course, the representation of the virtual image R produced by the image source consists of light focused at infinity, which requires a lens (e.g., the lens of the human eye) to focus the image so that the orientation discussed above can be detected.

[0026] The incoupling diffractive optical element IDO, the rotating diffractive optical element TO, and the outcoupling diffractive optical element ODO collectively preferably preserve the angular relationships between the beams of different wavelengths that define the virtual image upon transport from the offset position to the near-eye position of the viewer by the image light guide 12. Meanwhile, the incoupling diffractive optical element IDO, the rotating diffractive optical element TO, and the outcoupling diffractive optical element ODO may be positioned and oriented relative to one another in different ways to control the overall shape of the image light guide 12 as well as the overall orientation at which the angularly related beams may be directed into and out of the image light guide 12.

[0027] FIG. 3 shows a planar schematic view of a portion of an exemplary head-mounted image light guide system 100 according to the present disclosure. In some embodiments, the image light guide system 100 can take the form of a head-mounted display (as shown in FIG. 13) or other head-mounted optical system. As shown in FIG. 3, the exemplary image light guide system 100 includes an image light guide 102 in the form of a planar waveguide. Although not shown, the image light guide 102 can include the same structure, function, materials, and / or features as those described above with respect to the image light guide 12, for example, the image light guide 102 can include an in-coupling diffractive optical element, an intermediate rotating optical element, and an out-coupling diffractive optical element. Although illustrated as a planar waveguide, it will be appreciated that the image light guide 102 can be a non-planar waveguide, for example, a curved waveguide. In addition, the image light guide 102 includes a transparent substrate, which can be made of optical glass or plastic, for example, having plane-parallel front and back surfaces 104 and 106, respectively. Of course, similar to the image light guide system 10 described above, the image light guide system 100 and image light guide 102 are configured to receive angularly related image-bearing light beams and couple the angularly related image-bearing light beams into the image light guide 102 by an in-coupling diffractive optical element (located on the front surface 104 or back surface 106 of the image light guide and configured as a transmissive or reflective diffractive element). Once coupled into the image light guide 102, the angularly encoded image-bearing light beams are configured to propagate along the length dimension of the image light guide 102 and exit the image light guide 102 by interaction with the out-coupling diffractive optical element, such that at least one image is formed within the eye box E for viewing by a viewer or other optical components. As described above with respect to the image light guide 12, the image light guide 102 can also utilize one or more encounters with intermediate rotating or out-coupling optical elements to expand the size of the eye box E in one or more dimensions.

[0028] As shown in FIG. 3, the image light guide system 100 also includes an image source 108. In some embodiments, the image source 108 is a projector that includes a light source and one or more optical components for focusing and / or collimating the light generated by the light source. In some embodiments, the image source 108 includes one or more light emitting diodes (LEDs), organic LEDs (OLEDs), or ultra-LEDs (uLEDs). In other embodiments, the image source 108 is a color field sequential projector system operable to pulse image-bearing light of multiple wavelength bands, e.g., light from within the red, green, and blue wavelength ranges, to a digital light modulator / micromirror array ("DLP") or liquid crystal on silicon ("LCOS") display. In further embodiments, the image source 108 includes one or more pico projectors, each pico projector configured to generate a single primary color band (e.g., red, green, or blue). In another embodiment, the image source 108 includes a single pico projector arranged to generate at least three primary color bands (e.g., red, green, and blue). In one example, the three primary color bands include a green band having wavelengths ranging between 495 nm and 570 nm, a red band having wavelengths ranging between 620 nm and 750 nm, and a blue band having wavelengths ranging between 450 nm and 495 nm. The substantially collimated light generated by the pico projector, upon coupling and transmission through the image light guide 102, can be used by the image light guide system 100 to form one or more virtual images viewed by a user's eyes or other optical components positioned within the eye box E.

[0029] With continued reference to FIG. 3, the image light guide system 100 also includes a frame 110 including a right eye rim section 112 having a right temple 114 and a nose bridge portion 116. Between the temple 114 and the nose bridge portion 116, the frame 110 includes a right opening 118 configured to receive the image light guide 102 such that during operation of the image light guide system 100, the image light guide 102 is configured to form at least one image associated with one or more virtual objects in a right eye 120 of a viewer. Although only the right eye rim section 112 and the right eye 120 are illustrated in FIG. 3, it will be appreciated that the frame 110 may be symmetrical, i.e., may include a right eye rim section 112 and a left eye rim section (not shown), each of which may both include a respective temple and a respective image light guide 102 configured to form respective virtual images associated with one or more virtual objects in the right and left eyes of a viewer. In other words, the image light guide system 100 and the frame 110 can be configured as a binocular display system that forms an image in both the right and left eyes of a viewer. In some embodiments, the frame 110 is made of metal, plastic, or wood material (or any combination thereof) and is intended to be opaque, i.e., not transmit visible light. In some embodiments, the image light guide 102 is removably secured between the temple 114 and the nose bridge portion 116, i.e., the image light guide 102 can be removed and / or replaced using additional tools. Furthermore, it should be understood that in one or more exemplary embodiments of the image light guide system 100 (whether a binocular system as described above, or a monocular system), the image light guide system 100 can include multiple stacked image light guides 102. For example, one image light guide 102 in the stack is configured to incouple and propagate light in a first wavelength range (e.g., light in the red portion of the visible spectrum) and another image light guide 102 in the stack is configured to incouple and propagate light in a second wavelength range (e.g., light in the green and / or blue portions of the visible spectrum).

[0030] Additionally, as shown in FIG. 3, the image light guide system 100 may further include a cover window or other protective outer cover 122. In some embodiments, an anti-reflective coating may be provided on the front and / or back surface of the protective outer cover 122. In some embodiments, the protective outer cover 122 may provide filtering or other optical functions that affect the viewer's view of the real-world object RWO without affecting the viewer's view of the virtual object VO, since the protective outer cover 122 is located between the image light guide 102 and the real-world object RWO. Additionally, the image light guide system 100 may include an optical coupler 124. The optical coupler 124 may take the form of an in-coupling diffractive optical element, such as a plurality or set of surface relief gratings or a volume hologram. In some embodiments, the optical coupler 124 may take the form of a prism configured to receive image-bearing light from the projector 106 and redirect and / or in-couple the image-bearing light into the image light guide 102. In some embodiments, optical coupler 124 includes an incoupling diffractive optical element as well as a prism.

[0031] FIG. 4 illustrates a simplified schematic plan view of one exemplary configuration of the right-eye rim section 112 of the image light guide system 100, with certain components of the frame 110 removed for clarity. As shown, the image light guide system 100 is configured to receive virtual image-bearing light 126 generated by an image source (e.g., image source 108 shown in FIG. 3) and form an image related to a virtual object VO (shown as a triangular symbol with a letter "V") in the eye box E using at least the in-coupling, TIR, and out-coupling mechanisms of said image light guide 102. Additionally, within the common field of view FOV, the image light guide 102 is also operable to receive and transmit to the eye box E image-bearing light 128 reflected from a real-world object RWO (shown as a star-shaped symbol with a letter "R"). Thus, the viewer's right eye 120 is configured to form an image related to the virtual object VO and an image related to the real-world object RWO from within the common field of view FOV. Of course, the common field of view FOV can encompass a wider or narrower field of view angle than the field of view shown; for example, the common field of view FOV may be wide enough to completely encompass the image light guide 102 or may cover only a portion of the image light guide 102. As shown in Figures 4-7, the dotted lines associated with the virtual image-bearing light 126 (discussed below) indicate a virtual projection associated with a virtual image originating from a virtual source location. In other words, the dotted lines illustrate the virtual image-bearing light tracing back to a virtual focal point in the environment, such that the light used to form the virtual object VO in the eyebox E appears to originate from a virtual location of the virtual object VO in the environment and in the common FOV. As shown in Figure 4, the virtual image-bearing light 126 is incoupled into the image light guide 102, propagates along the length dimension of the image light guide 102 (vertical direction in Figure 4), via TIR, and outcoupled as virtual image-bearing light 128, operable to form one or more images in the eyebox associated with one or more virtual objects VO from within the environment.Further, real-world image-bearing light 130 is transmitted through image light guide 102, travels to eyebox E, and is operable to form one or more images within eyebox E associated with one or more real-world objects RWO from within the environment and from within the common field of view FOV as virtual objects VO.

[0032] As described above, the image source 108 is configured to generate a substantially collimated virtual image-bearing light 126. In an embodiment of the image light guide system 100 in which the incoupling diffractive optical element and the outcoupling diffractive optical element do not introduce light power into the incoupling virtual image-bearing light 126, an image associated with a virtual object VO formed in the eye box E is focused at optical infinity. For some users, particularly those with certain forms of eye disease such as myopia (nearsightedness) or astigmatism, it may not be desirable to generate images of virtual objects focused at optical infinity. Instead, it may be desirable to focus those objects at a closer focusing distance, i.e., a focusing distance shorter than optical infinity.

[0033] FIG. 5 illustrates a simplified schematic plan view of one exemplary configuration of the right-eye rim section 112 of the image light guide system 100. Although not illustrated for clarity in FIGS. 5-7, it is understood that the virtual image-bearing light 126 may be incoupled into the image light guide 102 and may propagate by TIR along the length dimension of the image light guide 102 (vertical in FIGS. 5-7) until it is outcoupled from the image light guide 102 as virtual image-bearing light 128A. Additionally, although not illustrated in FIG. 5, it is understood that the virtual object VO and the real-world object RWO are in a common field of view, as shown and described with respect to FIG. 4 above. As illustrated in FIG. 5, the image light guide system 100 may also include a negative power optical element 132 that provides a negative light output contribution 134 to the image light guide system 100. As illustrated, the negative power optical element is positioned between the image light guide 102 and the viewer's right eye 120. The negative power optical element 132 operates to diverge the incident image-bearing light, reducing the apparent focal distance of the incident image-bearing light. By positioning the negative power optical element 132 between the image light guide and the user's eye 120, the negative power optical element 132 operates to reduce the focal distance of a virtual object originally focused at optical infinity. For example, the negative power optical element 132 is configured to diverge the virtual image-bearing light 128A such that the focal distance of the virtual object VO is reduced from a first focal distance FD1 (e.g., optical infinity) associated with the virtual image-bearing light 128B to a second focal distance FD2, the second focal distance being shorter than the first focal distance (e.g., less than optical infinity). 5, it should be appreciated that the negative power optical element 132 may be formed as, but is not limited to, a plano-concave lens, a bi-concave lens, a negative meniscus lens, or any optical element that diverges incident light in a predictable manner to form at least one image that has a reduced focused distance from its actual distance to the viewer. In some embodiments, the second focused distance FD2 is between 0.005 m and 6 m. In other embodiments, the second focused distance FD2 is selected from between 0.005 m and 4 m.

[0034] As a result of placing a negative power optical element (e.g., negative power optical element 132) between the image light guide 102 and the eye box E, the virtual image-bearing light 128B is focused by the viewer's eye 120 such that the virtual object VO appears at a second focusing distance FD2 (indicated by a triangle formed by dotted lines in FIG. 5 ). Here, the second focusing distance FD2 is shorter than the first focusing distance FD1 for the eye box E. Furthermore, when the negative power optical element 132 is positioned between the eye box E and the real-world object RWO, the negative power optical element 132 also operates to diverge the real-world image-bearing light 130A such that the focusing distance of any real-world object RWO is shortened, for example, from the first focusing distance FD1 to a second focusing distance FD2 (indicated by a star formed by dotted lines in FIG. 5 ). Of course, the real-world object RWO does not need to be located at a distance of more than 6 meters (20 feet), i.e., at an infinite focusing distance, to be affected by the negative light output contribution of the negative power optical element. For example, the perceived focusing distance of a real-world object RWO located at a finite focusing distance, e.g., 1-5 meters from the viewer, is also reduced. If the viewer wishes to view the virtual object VO at a closer focusing distance without changing the perception of distance to any real-world object RWO, the negative light output contribution 134 of the negative power optical element 132 must offset the real-world image-bearing light 130A.

[0035] As shown in Figure 6, this figure shows a simplified schematic plan view of one exemplary configuration of the right-eye rim section 112 of the image light guide system 100 having both a negative output optical element 132 and a positive output optical element 136, where the positive output optical element 136 is provided with a positive light output contribution 138 that offsets, cancels, or nullifies the negative light output contribution 134 of the negative output optical element 132 to an image formed from light reflected from a real-world object RWO in the environment. As shown, the positive output optical element 136 is positioned between the image light guide 102 and the real-world object RWO, i.e., on the opposite side of the image light guide 102 relative to the negative output optical element 132. The positive output optical element 136 operates to focus the incoming image-bearing light, increasing the apparent focusing distance of any real-world object RWO. By positioning the positive output optical element 136 between the image light guide 102 and the real-world object RWO having an environment, before the real-world image-bearing light 130A reaches the image light guide 102 and / or the negative power optical element 132, the positive output optical element 136 increases the focal length of the real-world object RWO and offsets, cancels or nullifies the reduction in the focal length of the image of the real-world object RWO caused by the negative power optical element 132. Of course, the positive output optical element 136 may be formed as at least a portion of the cover window 122 and / or the positive optical contribution 138 may be provided at least in part by the cover window 122.

[0036] In some embodiments, the negative light output contribution 134 and the positive light output contribution 138 are measured in diopters. In these embodiments, the diopter value of the negative output optical element 132 is equal to and opposite to the light output provided by the positive output optical element 134. For example, the negative light output contribution 134 may be selected as at least one of −0.5, −0.75, −1, −1.5, −2 diopters, etc. Therefore, to preemptively counteract the effect of this negative light output contribution 134 on the image of the real-world object RWO, the positive light output contribution 138 of the positive output optical element 136 is selected to be at least one of +0.5, +0.75, +1, +1.5, +2 diopters, such that the converging effect of the positive output optical element 136 and the diverging effect of the negative output optical element 132 are completely countered such that there is no net effect on the real-world position of the real-world object RWO as perceived by a viewer or other sensor positioned within the eyebox E. In other words, the net effect of providing a negative power optical element 132 between the image light guide 102 and the eye box E, and a positive power optical element 136 between the image light guide 102 and the real-world object RWO in the environment (where the light output contributions of each optical element 132, 136 have the same magnitude and cancel each other out), is that the virtual object VO appears at a focusing distance less than optical infinity, while the focusing distance of the real-world object RWO remains unchanged.

[0037] As shown in FIG. 6, the virtual image-bearing light 126 (shown in FIGS. 3 and 4) is outcoupled from the image light guide 102 as a substantially collimated virtual image-bearing light 128A. As the virtual image-bearing light 128A refracts through the negative power optical element 132, the light diverges (shown as virtual image-bearing light 128B). The virtual image-bearing light 128B enters the eyebox E and forms an image of the virtual object VO at a second focusing distance FD2 (shown as a triangle formed by dotted lines in FIG. 6). Additionally, the real-world image-bearing light 130A reflected off a real-world object RWO in the environment propagates into the image light guide system 100 and encounters a positive output optical element 136 that converges the real-world image-bearing light 130A forming the real-world image-bearing light 130B. In this example, the positive output optical element 136 may be formed with a positive light output contribution of +2 diopters. The real-world image-bearing light 130B is then transmitted through the image light guide 102 and encounters the negative output optical element 132, which has a negative light output contribution 134 of -2 diopters. As the real-world image-bearing light 130B refracts through the negative output optical element 132, the light diverges such that the net effect of the positive light output contribution 138 of the positive light output element 136 and the negative light output contribution 134 of the negative light output element 132 are cancelled, and the real-world image-bearing light 130C is operable to form images of the real-world objects RWO at their true locations in the environment.

[0038] It should be understood that the embodiment described above with respect to +2 and -2 diopter values ​​is merely one example, and in operation, the image light guide system 100 may utilize any possible diopter setting for both the negative light output contribution 134 and the positive light output contribution 138. In some embodiments, these two diopter values ​​cancel each other out and have no net effect on the perceived focused distance of the real-world object RWO. It should also be understood that, although shown diagrammatically in FIG. 6, the positive output optical element 132 may be formed as, but is not limited to, a plano-convex lens, a bi-convex lens, a positive meniscus lens, or any optical element that converges incident light in a predictable manner to form at least one image with an increased focused distance from its actual distance to the viewer.

[0039] In addition to the foregoing, it may be desirable to correct for a particular viewer's optical aberrations associated with various refractive disorders, such as myopia (near-sightedness), hyperopia (far-sightedness), or astigmatism. To that end, as shown in FIG. 7, the imaging light guide system 100 may also include one or more corrective optical elements 140 that provide corrective optical contributions 142 to both the virtual image-bearing light 128 and the real-world image-bearing light 130. In one or more embodiments, the corrective optical elements 140 may be formed as non-variable (e.g., fixed focus) monofocal, bifocal, or multifocal optical elements, such as refractive lenses, diffraction gratings, holographic optical elements (HOEs), or any combination thereof.

[0040] As shown in FIG. 7, the virtual image-bearing light 126 (shown in FIGS. 3 and 4) is outcoupled from the image light guide 102 as a substantially collimated virtual image-bearing light 128A. As the virtual image-bearing light 128A refracts through the negative power optical element 132, the light diverges (shown as virtual image-bearing light 128B). The virtual image-bearing light 128B continues toward the eyebox E until it encounters and refracts the corrective optical element 140. The corrective optical element 140 provides a corrective optical contribution 142 that can be customized to offset the viewer's particular eye condition, e.g., myopia (nearsightedness). The corrected virtual image-bearing light 128C then operates to form one or more images of the virtual object VO at a corrected distance CD. In an embodiment, if the corrective optical element 140 is selected to correct myopia, the corrective optical contribution 142 provides a negative light output, decreasing the apparent distance to the virtual object VO (shown as a black triangle in FIG. 7). It will also be appreciated that when the corrective optical contribution 142 of the negative power optical element 132 and the negative contribution of the negative light power contribution 134 are positioned in series, a negative output is combined and the virtual object VO appears at a corrected distance CD that appears closer to the viewer than the second focusing distance FD2.

[0041] Additionally, the real-world image-bearing light 130A reflected off of a real-world object RWO in the environment propagates into the image light guide system 100 and encounters a positive output optical element 136 that converges the real-world image-bearing light 130A forming real-world image-bearing light 130B. In this example, the positive output optical element 136 may be formed with a positive light output contribution of +2 diopters. The real-world image-bearing light 130B is then transmitted through the image light guide 102 and encounters a negative output optical element 132 having a negative light output contribution 134 of -2 diopters. As the real-world image-bearing light 130B refracts through the negative output optical element 132, the light is converged such that the net effect of the positive light output contribution 138 of the positive light output element 136 and the negative light output contribution 134 of the negative light output element 132 cancel each other out to form a real-world image-bearing light 130C that represents the true position of the real-world object RWO in the environment. The real-world image-bearing light 130C continues to propagate in the direction of the eyebox E and encounters the corrective optics 140. Continuing with the example above in which the corrective optics 140 is selected to correct myopia (nearsightedness), the corrective optical contribution 142 provides a negative light output, decreasing the apparent distance to the real-world object RWO (shown as a black star in FIG. 7). Not surprisingly, the negative output of the corrective optics 140 operates to form an image in the eyebox E of the real-world object RWO at a corrected distance CD that appears closer to the viewer than the true location of the real-world object RWO (e.g., the first focusing distance FD1).

[0042] In some embodiments, FIGS. 8A-8B depict side views of an image light guide system 100 according to the present disclosure, where the corrective optical element 140 may be a multifocal optical element, such as a bifocal optical element (FIG. 8A) or a trifocal optical element (FIG. 8B). In FIG. 8A, for example, the image light guide system 100 may include a bifocal corrective optical element 140. In this manner, the bifocal corrective optical element 140 is comprised of a plurality of corrective sections 144A-144B. The first corrective section 144A and the second corrective section 144B (collectively referred to herein as "multiple corrective sections 144" or "corrective section 144") are intended to be integral sections of a single corrective optical element. However, it should be understood that each corrective section 144 may be an individual optical element positioned adjacent to one another, as shown in FIG. 8A.

[0043] As shown, each correction section 144 provides a different correction light output than any adjacent correction section such that the different light outputs properly focus images from objects at different distances to correct optical aberrations for a particular viewer at each distance. For example, FIG. 8A shows two real-world objects RWO, RWO' present in an environment. The first real-world object RWO may be positioned farther away from the eyebox E than the second real-world object RWO'. For example, the first real-world object RWO may be positioned at a distance of more than 6 meters from the eyebox E, while the second real-world object RWO' may be positioned at a closer distance to the first real-world object RWO, for example, 3 meters from the eyebox E.

[0044] For a first real-world object RWO, light reflected from that object propagates as real-world image-bearing light 130A until it reaches positive output optic 136 where it converges to form real-world image-bearing light 130B. Real-world image-bearing light 130B continues to propagate through image light guide 102 and encounters negative output optic 132 where it diverges in a manner equal to or opposite to the converging effect of positive output optic 136 to form real-world image-bearing light 130C. Real-world image-bearing light 130C continues to propagate in the direction of eyebox E until it encounters first correction section 144A of bifocal correction optic 140. Upon transmission through the first corrected section 144A, the real-world image-bearing light 130C is formed into a real-world image-bearing light 130D, which is used to form an image of the real-world object RWO, for example, appearing closer than the true location of the real-world object RWO in the environment, i.e., at the first corrected focusing distance 146. Additionally, the light reflected from the second real-world object RWO' propagates as real-world image-bearing light 130A' until it reaches the positive output optic 136, where the real-world image-bearing light 130A' converges to form the real-world image-bearing light 130B'. The real-world image-bearing light 130B' continues to propagate through the image light guide 102 and encounters the negative output optic 132, where it diverges in a manner equal to or opposite to the converging effect of the positive output optic 136, forming the real-world image-bearing light 130C'. The real-world image-bearing light 130C' continues to propagate in the direction of the eyebox E until it encounters a second corrected section 144B of the bifocal correction optics 140. Upon transmission through the second corrected section 144B, the real-world image-bearing light 130C' is formed into a real-world image-bearing light 130D', which is used to form an image of the real-world object RWO' that appears closer to the real-world object RWO' in the environment, i.e., at the second corrected focusing distance 148, than its true position.

[0045] Further, as shown in FIG. 8A, it is understood that the first correction section 144A provides a first corrected light output, and the second correction section 144B provides a second corrected light output, where the first corrected light output is different (e.g., larger) than the second corrected light output. For example, if the correction output of the bifocal correction optical element 140 is selected to correct myopia (near-sightedness), the change in the focal distance between the true position of the real-world object RWO and the first focal distance 146 is larger than the change in the focal distance between the true position of the real-world object RWO' and the second focal distance 148. It is understood that the light output of each correction section 144 may also be selected to correct other refractive disorders, such as hyperopia (far-sightedness), in which case the light output of each correction section 144 is selected to have less effect (if any) on objects over 6 meters.

[0046] FIG. 8B illustrates a side view of an image light guide system 100 according to the present disclosure, where the corrective optical element 140 is a trifocal optical element. The real-world image-bearing lights 130A-130D (associated with real-world object RWO) and the real-world image-bearing lights 130A'-130D' (associated with real-world object RWO') are similar to those described in connection with FIG. 8A. However, as shown in FIG. 8B, the corrective optical element 140 includes a third corrective section 144C that provides a third corrected light output that is different from the first corrected light output and the second corrected light output associated with the first corrective section 144A and the second corrective section 144B. Additionally, a third real-world object RWO'' is provided in the environment. Additionally, light reflected from the third real-world object RWO'' propagates as real-world image-bearing light 130A'' until it reaches positive output optic 136 where real-world image-bearing light 130A'' converges to form real-world image-bearing light 130B''. Real-world image-bearing light 130B'' continues to propagate through image light guide 102 and encounters negative output optic 132 where it diverges in a manner equal to or opposite to the converging effect of positive output optic 136 to form real-world image-bearing light 130C''. Real-world image-bearing light 130C'' continues to propagate in the direction of eyebox E until it encounters third corrective section 144C of trifocal corrective optic 140. Upon transmission through the third correction section 144C, the real-world image-bearing light 130C'' is formed into real-world image-bearing light 130D'', which is used to form an image of the real-world object RWO'' that appears, for example, closer than the true position of the real-world object RWO'' in the environment, i.e., at the third corrected focusing distance 150.

[0047] 8A-8B illustrate the effect of multi-focal corrective optics 140 on real-world image-bearing light 130A-130D, 130A'-130D', and 130A''-130D'', and, for illustrative clarity only, do not illustrate the effect of multi-focal corrective optics 140 on virtual image-bearing light 128. However, it will be appreciated that the effects described above with respect to real-world image-bearing light 130B-130D, 130B'-130D', and 130B''-130D'' may equally be applied to virtual image-bearing light 128 prior to entering eyebox E.

[0048] 9, it will be appreciated that the correction optics 140 may be positioned between the image light guide 102 and the real world objects RWO, RWO', RWO''. For example, with respect to a first real world object RWO, light reflected from that object propagates as real world image-bearing light 130A until it reaches the correction optics 140, where real world image-bearing light 130A encounters a first correction section 144A to form real world image-bearing light 130B. Real world image-bearing light 130B continues to propagate until it reaches the positive output optics 136, where the light converges to form real world image-bearing light 130C. Real world image-bearing light 130C continues to propagate through the image light guide 102 and encounters the negative output optics 132, where it diverges in a manner equal to or opposite to the converging effect of the positive output optics 136 to form real world image-bearing light 130D. After transmitting through the negative power optic 132, the real-world image-bearing light 130D continues into the eyebox E and is used to form an image of the real-world object RWO that appears, for example, closer than the true location of the real-world object RWO in the environment, i.e., at the first corrected focusing distance 146. Additionally, the light reflected from the second real-world object RWO' propagates as real-world image-bearing light 130A' until it reaches the correcting optic 140, where the real-world image-bearing light 130A' encounters the second correcting section 144B and forms the real-world image-bearing light 130B'. The real-world image-bearing light 130B' continues to propagate until it reaches the positive power optic 136, where the light converges to form the real-world image-bearing light 130C'. Real-world image-bearing light 130C' continues to propagate through image light guide 102 and encounters negative power optic 132 where it diverges in a manner equal to or opposite to the focusing effect of positive power optic 136 to form real-world image-bearing light 130D'. After transmitting through negative power optic 132, real-world image-bearing light 130D' continues to enter eyebox E and is used to form an image of real-world object RWO' that appears, for example, closer than the true location of real-world object RWO' in the environment, i.e., at second corrected focusing distance 148.As shown, it will be appreciated that the positive output optical element 136 and the corrective optical element 140 may be formed as a single multi-function optical element 152, as described below.

[0049] Of course, although shown as two or three integral correction sections, i.e., correction sections 144A-144C, correction optics 140 can include more than two correction sections 144. For example, correction optics 140 can include four, five, ten, fifteen, twenty, thirty or more correction sections. Multiple correction sections 144 can provide a seamless transition between correction sections 144, with each correction section 144 operating to focus the image formed in the viewer's eye at a different focusing distance.

[0050] 9, in an exemplary embodiment, the image light guide system 100 may include at least one multifunction optical element 152 configured to perform the functions of one or more of the optical elements described above. For example, the positive output optical element 136 and the corrective optical element 140 are formed as a single multifunction optical element 152 arranged to perform the functions of both optical elements 136, 140 as described above. As shown, the single multifunction optical element 152 may be positioned between the image light guide 102 and the real-world object RWO and includes both light output contributions of the corrective optical element 140 (e.g., the corrective optical contribution 142) as well as the positive light output contribution 138 of the positive output optical element 136.

[0051] FIG. 10A illustrates a plan view schematic of a portion of an exemplary head-mounted image light guide system 100 according to the present disclosure. As shown, the image light guide system 100 may include at least one multifunction optical element 152 configured to perform the functions of one or more of the optical elements described above. In the example illustrated in FIG. 10A, the negative power optical element 132 and the corrective optical element 140 are formed as a single multifunction optical element 152 arranged to perform the functions of both optical elements 132, 140 as described above. As shown, the single multifunction optical element 152 may be formed as a doublet lens positioned between the image light guide 102 and the eye box E and includes both light output contributions of the corrective optical element 140 (e.g., the corrective optical contribution 142) as well as the negative light output contribution 134 of the negative power optical element 132. It will further be appreciated that the multifunction optical element 152 may be arranged to perform the functions of the positive power optical element 136 and the corrective optical element 140. This single multifunction optical element 152 can be formed as a doublet lens positioned between the image light guide 102 and the real-world object RWO and includes both light output contributions of the corrective optical element 140 (e.g., the corrective optical contribution 142) as well as the positive light output contribution 138 of the positive output optical element 136.

[0052] In an exemplary embodiment, as shown in FIG. 10B, image light guide system 100 includes at least one multifunction optical element 152 arranged to perform the functions of both negative power optical element 132 and corrective optical element 140, as described above. As shown, a single multifunction optical element 152 can be formed as a doublet lens positioned between image light guide 102 and real-world object RWO and includes both light output contributions of corrective optical element 140 (e.g., corrective optical contribution 142) as well as the negative light output contribution 134 of negative power optical element 132. Of course, cover window 122 is an optional element in at least one embodiment of image light guide system 100 arranged as shown in FIGS. 10A-10B.

[0053] Additionally, it will be appreciated that corrective optics 140, negative power optics 132, and positive power optics 136 may be separate optical elements separated by air or other medium, as shown generally in Figures 7-9. For example, negative power optics 132 and corrective optics 140 may be separate lenses located between image light guide 102 and eyebox E, as shown in Figures 7-8B. Alternatively, positive power optics 136 and corrective optics 140 may be separate lenses located between image light guide 102 and real world object RWO, as shown in Figure 9.

[0054] In some embodiments of the image light guide system 100, as shown in FIG. 11, the right eye rim section 112 can further include a removable lens carrier 154 positioned between the nose bridge section 116 and the right temple 114, and configured to be removably engaged or disengaged with the right eye rim section 112 using an additional tool. Furthermore, in each of the above configurations, each of the above lenses can be placed into and removed from a respective slot in the lens carrier 154 such that each lens is removable and / or replaceable. By having the lens carrier 154 as well as the lenses themselves removable from the image light guide system 100, the viewer can easily customize the light output contribution of each lens to customize the viewing experience to compensate for the viewer's particular optical aberrations.

[0055] In some exemplary embodiments, as shown in FIG. 12, the image light guide system 100 may include one or more electromagnetic metamaterials engaged with or embedded within one or more surfaces of the image light guide system 100. For example, metamaterials may be formed on or embedded within one or both surfaces of (i) the front surface 104 of the image light guide 102, (ii) the back surface 106 of the image light guide 102, and (ii) the cover window or protective outer cover 122 to form one or more electromagnetic metasurfaces. Thus, one or more optical elements within the scope of the present disclosure, such as the negative output optical element 132, the positive output optical element 136, or the corrective optical element 140, may be formed from an optically translucent structure, such as the image light guide 102, that includes one or more metamaterials configured to respectively converge, diverge, or correct image-bearing light passing through the optically translucent structure. Of course, the material properties of the metamaterial can be selected from any material having a subwavelength structure configured to mimic the optical properties of a lens, e.g., concave, convex, or other optical element, without requiring that the surfaces of the optical structure be curved. In other words, the image light guide 102 and / or protective outer layer 122 disclosed in this disclosure may include flat surfaces, but a metamaterial disposed on the surface of one or more of these features may cause light rays and / or electromagnetic wavefronts associated with light passing through these features to behave as if they were passing through a shaped lens.

[0056] FIG. 12 illustrates one exemplary embodiment of a portion of an image light guide system 100 that includes one or more metamaterials instead of lenses. In this example, rather than a lens, a linear grating structure, or a holographic optical element (HOE), the image light guide system 100 provides a negative light output contribution 134, a positive light output contribution 138, or a corrective light output contribution 142 as previously described. As shown in FIG. 12, in one embodiment, the image light guide system 100 includes a first metamaterial 156 located on or embedded within an inner surface 104 of the image light guide 102 and a second metamaterial 158 located on or embedded within an outer surface 106 of the image light guide 102. As shown, the first metamaterial 156 is configured to diverge the virtual image-bearing light 128 and the real-world image-bearing light 130, and thus is operable to provide the negative light output contribution 134. The second metamaterial 158 is configured to focus the real-world image-bearing light 130, and thus is operable to provide the positive light output contribution 138. Of course, as with other exemplary embodiments described herein, the diopter values ​​of the negative light output contribution 134 and the positive light output contribution 138 can be equal and opposite such that they cancel each other out with respect to real-world image-bearing light 130.

[0057] In the example shown in FIG. 12, the virtual image-bearing light 126 (shown in FIGS. 3 and 4) propagates within the image light guide 102 via TIR and is outcoupled from the image light guide 102 as a substantially collimated virtual image-bearing light. Upon being outcoupled from the image light guide 102, the virtual image-bearing light 128 engages a first metamaterial 156 having a negative light output contribution 134. Upon transmitting through the first metamaterial 156, the light diverges (shown as virtual image-bearing light 128B) and enters the eyebox E to form an image of the virtual object VO at a second focusing distance FD2 (shown as a triangle formed by dotted lines in FIG. 12). Additionally, the real-world image-bearing light 130A reflected off a real-world object RWO in the environment propagates into the image light guide system 100 and encounters a second metamaterial 158 that converges the real-world image-bearing light 130A forming the real-world image-bearing light 130B. In this example, the positive light output contribution 138 of the second metamaterial 158 is selected as +2 diopters. The real-world image-bearing light 130B is then transmitted through the image light guide 102 and encounters the first metamaterial 156, which has a negative light output contribution 134 of -2 diopters. As the real-world image-bearing light 130B refracts through the first metamaterial 156, the light is focused such that the net effect of the positive light output contribution 138 of the second metamaterial 158 and the negative light output contribution 134 of the first metamaterial is cancelled, and the real-world image-bearing light 130C is operable to form images of the real-world objects RWO at their true locations in the environment.

[0058] It will be appreciated that at least one of the first metamaterial 156 and the second metamaterial 158 can also include optical structures or features operative to provide the corrective optical contribution 142. That is, it will be appreciated that either (i) the first metamaterial 156 can provide both the negative light output contribution 134 and the corrective optical contribution 142, (ii) the second metamaterial 158 can provide both the positive light output contribution 138 and the corrective optical contribution 142, or (iii) the first metamaterial 156 can provide both the negative light output contribution 134 and a portion of the corrective optical contribution 142, while the second metamaterial 158 can provide both the positive light output contribution 138 and a portion of the corrective optical contribution 142. It will also be appreciated that one or both of the first metamaterial 156 and the second metamaterial 158 can include one or more corrective sections 144A-144C, as described above in connection with FIGS. 8A-8B, and thus can provide multifocal correction capabilities.

[0059] It will also be appreciated that the first metamaterial 156 and / or the second metamaterial 158 may be located on or embedded within one or more surfaces of the protective outer cover 122 rather than, or in addition to, being located on or embedded within the image light guide 102. It will further be appreciated that the first metamaterial 156 and / or the second metamaterial 158 may be disposed on or embedded within a stand-alone optical component, such as a transparent or semi-transparent planar substrate, positioned between the eyebox E and the image light guide 102 and / or between the image light guide and the real-world object RWO.

[0060] In other examples, the corrective optical element 140 may be a focus-adjustable or variable-focus lens. The variable-focus lens may include a liquid lens, an adaptive liquid polymer lens, or one or more adaptively controllable liquid crystal Fresnel layers. The variable-focus lens may be adjusted manually via viewer interaction with, for example, a button, a switch, a capacitive touch sensor, a slide switch, or the like, or automatically via an electronic connection to one or more controllers of the image light guide system 100. To that end, the controller may include a processor and a non-transitory computer-readable memory configured to execute and store, respectively, a set of computer-readable instructions operable to variably change the focus of at least a portion of the variable-focus lens. Additionally, the image light guide system 100 may further include one or more rear-facing sensors (e.g., one or more sensors or cameras directed toward the viewer's eyes and face) configured to determine the angular convergence of the viewer's eyes and automatically adjust or change the focal length of the variable-focus lens to provide a specific corrective optical contribution to help the viewer focus an object at a focusing distance corresponding to the angular convergence of the viewer's eyes.

[0061] The perspective view shown in FIG. 13 illustrates an example of an image light guide system 100 in a display system for augmented reality display of virtual images. The image light guide system 100 uses one or more image light guides (e.g., image light guide 102). The image light guide system 100 is shown as a head mounted display (HMD) having a right eye rim section 112 with an image light guide 102R proximate to a user's right eye. The image light guide system 100 includes an image source 108, such as a pico projector or similar device, that can be energized to generate one or more virtual images. Although not shown, in one embodiment, the image light guide system 100 includes a left eye optical system that includes one or more image light guides and a second image source. In an embodiment using both the right eye rim section 112 and the left eye rim section, the generated virtual image can be a stereoscopic image for 3D display. During operation by a user or viewer, the virtual image or images formed by image light guide system 100 may appear superimposed or overlaid on real-world scene content seen by the viewer through right eye image light guide 102R and / or left eye image light guide 102. Additional components familiar to those skilled in the art of augmented reality visualization may also be provided, such as mounting one or more cameras on the frame of the HMD for viewing scene content or eye tracking of the viewer.

[0062] One or more features of the embodiments described herein may be combined to create additional embodiments not shown. Although various embodiments have been described in detail above, it should be understood that they are presented for illustrative purposes and not for limiting purposes. It will be apparent to those skilled in the relevant art that the subject matter of the present disclosure may be embodied in other specific forms, variations, and modifications without departing from its scope, spirit, or essential characteristics. The above-described embodiments are therefore to be considered in all respects as illustrative and not restrictive. The scope of the present invention is indicated by the appended claims, and all changes that come within the meaning and range of equivalents thereof are intended to be embraced therein.

Claims

1. 1. An image light guide system for viewing virtual and real-world objects in a common field of view, comprising: an image light guide having an inner surface and an outer surface, the image light guide being positioned to direct an image-bearing light beam of the virtual object toward an eyebox at a first focused distance; a negative power optical element disposed between the image light guide and the eyebox, the negative power optical element having a negative light output contribution operable to diverge the image-bearing light beam to a second focused distance prior to the eyebox, the second focused distance being shorter than the first focused distance; a non-variable corrective optical element disposed between the image light guide and the real world object, the corrective optical element having a corrective optical contribution operable to reduce optical aberrations associated with viewing the real world object at the second focusing distance; and an image light guide system comprising: a positive output optical element disposed between the image light guide and the real-world object, the positive output optical element having a positive light output contribution operable to cancel out the negative light output contribution of the negative output optical element without canceling or nullifying the corrective optical contribution of the corrective optical element;

2. The image light guide system of claim 1 , wherein the positive output optical element is formed as at least a portion of a cover window disposed between the image light guide and the real-world object.

3. The image light guide system of claim 2 , wherein the cover window is disposed between the corrective optical element and the real-world object.

4. 2. The image light guide system of claim 1, wherein the positive output optical element and the corrective optical element are formed as a single multifunction optical element, the single multifunction optical element being selected from (i) a lens doublet or (ii) a single lens, the lens doublet or the single lens providing both the negative light output contribution and the corrective optical contribution.

5. The image light guide of system 1, wherein one or more of the negative power optical element, the positive power optical element, and the corrective optical element comprise a metamaterial.

6. The image light guide system of claim 1 , wherein the first focusing distance is a focusing distance between a hyperfocal distance and near infinity.

7. The image light guide system of claim 1 , wherein the second focusing distance is between 0.05 meters and 4 meters.

8. 2. The image light guide system of claim 1, wherein the corrective optical element comprises a plurality of correction sections, the plurality of correction sections including a first correction section arranged to focus one or more real-world objects at a first corrected focusing distance and a second correction section arranged to focus the one or more real-world objects at a second corrected focusing distance, the first corrected focusing distance and the second corrected focusing distance being different.

9. 10. The image light guide system of claim 8, wherein the plurality of correction sections further includes a third correction section arranged to focus the one or more real-world objects at a third focusing distance different from the first focusing distance and the second focusing distance.

10. The image light guide system of claim 9 , wherein the plurality of correction sections are positioned to progressively focus the one or more real world objects.

11. The image light guide system of claim 1 , wherein the positive output optical element is a lens having a convex outer surface, the convex outer surface being treated with a protective coating.

12. 1. An image light guide for viewing virtual objects and real world objects in a common field of view, comprising: an inner surface and an outer surface arranged to direct the image-bearing light beam of the virtual object at a first focused distance toward an eyebox; a first metamaterial having a negative optical power contribution configured to diverge the image-bearing light beam in front of the eyebox at a second focusing distance that is shorter than the first focusing distance; a second metamaterial arranged to provide a positive light output contribution to counter the negative light output contribution of the first metamaterial.

13. The image light guide of claim 12 , wherein at least one of the first metamaterial and the second metamaterial operates as a corrective optical element to provide a corrective optical contribution.

14. 14. The image light guide of claim 13, wherein the corrective optical element comprises a plurality of correction sections, the plurality of correction sections including a first correction section arranged to focus one or more real-world objects at a first corrected focusing distance and a second correction section arranged to focus the one or more real-world objects at a second corrected focusing distance, the first corrected focusing distance and the second corrected focusing distance being different.

15. The image light guide of claim 12 , wherein the first metamaterial is located on or embedded within the inner surface of the image light guide.

16. The image light guide of claim 15 , wherein the second metamaterial is located on or embedded within the outer surface of the image light guide.

17. The image light guide of claim 12 , wherein at least one of the first metamaterial and the second metamaterial is located on or embedded within one or more surfaces of a cover window.

18. The image light guide of claim 12 , wherein at least one of the first metamaterial and the second metamaterial comprises a line grating.

19. The image light guide of claim 12 , wherein at least one of the first metamaterial and the second metamaterial comprises a holographic optical element.

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