Systems and methods for mixed reality

Abstract

To provide systems and methods for mixed reality.SOLUTION: A virtual image generation system comprises: a planar optical waveguide having opposing first and second faces; an in-coupling (IC) element configured for optically coupling a collimated light beam from an image projection assembly into the planar optical waveguide as an in-coupled light beam; a first orthogonal pupil expansion (OPE) element associated with the first face of the planar optical waveguide for splitting the in-coupled light beam into a first set of orthogonal light beamlets; a second orthogonal pupil expansion (OPE) element associated with the second face of the planar optical waveguide for splitting the in-coupled light beam into a second set of orthogonal light beamlets; and an exit pupil expansion (EPE) element associated with the planar optical waveguide for splitting the first and second sets of orthogonal light beamlets into an array of out-coupled light beamlets that exit the planar optical waveguide.SELECTED DRAWING: Figure 44

Description

Technical Field

[0001] The present disclosure relates to virtual reality, augmented reality, and mixed reality imaging and visualization systems.

Background Art

[0002] Modern computing and display technologies have facilitated the development of "mixed reality" (MR) systems for so-called "virtual reality" (VR) or "augmented reality" (AR) experiences, where digitally reproduced images or portions thereof are presented to a user in a manner that appears or is perceived to be real. VR scenarios typically involve the presentation of digital or virtual image information without transparency to other actual real-world visual inputs. Augmented reality (AR) scenarios typically involve the presentation of digital or virtual image information as an augmentation to the visualization of the real world surrounding the user (i.e., transparency to real-world visual inputs). Thus, AR scenarios involve the presentation of digital or virtual image information with transparency to real-world visual inputs.

[0003] MR systems typically generate and display color data, which increases the realism of MR scenarios. Many of these MR systems display color data by sequentially projecting sub-images within different (e.g., primary) colors or "fields" (e.g., red, green, and blue) corresponding to a color image at a high rate in rapid succession. Projecting the color sub-images at a sufficiently high rate (e.g., 60 Hz, 120 Hz, etc.) can result in a smooth color MR scenario for the user's memory.

[0004] For example, referring to Figure 1, an augmented reality scene 4 is depicted, and the user of AR / MR technology sees a real-world park-like setting 6 featuring people, trees, buildings in the background, and a concrete platform 8. In addition to these items, the end user of AR / MR technology also perceives "seeing" a robot image 10 standing on the real-world platform 8 and a flying cartoon-like avatar character 12 that looks like an anthropomorphic bumblebee, although these elements 10 and 12 do not exist in the real world. In conclusion, the human visual perception system is very complex, and producing VR, AR, and / or MR technologies that facilitate a comfortable, natural, and rich presentation of virtual image elements among other virtual or real-world image elements is difficult.

[0005] Some VR, AR, and / or MR systems employ a head-mounted display (or helmet-mounted display or smart glasses) that is at least loosely fitted to the end user's head and therefore moves with the user's head. When the end user's head movement is detected by the display subsystem, the displayed data can be updated to take into account the change in head orientation (i.e., the orientation and / or location of the user's head). Head-mounted displays that enable AR / MR (i.e., simultaneous viewing of real and virtual objects) can have several different types of configurations. In one such configuration, often referred to as a "video see-through" display, a camera captures elements of the real scene, a computing system superimposes virtual elements onto the captured real scene, and an opaque display presents the composite image to the eye. Another configuration, often referred to as an "optical see-through" display, allows the end user to directly view light from real objects in the environment by looking through transparent (or translucent) elements within the display subsystem. Often referred to as "couplers," transparent elements superimpose light from the display across the perspective of the real-world end user.

[0006] Some head-mounted VR / AR / MR systems employ a display screen within the end user's field of view and an image projection assembly that projects images onto the display screen. In one embodiment, the image projection assembly may take the form of an optical fiber scanning-based image projection assembly, and the display screen may take the form of an optical waveguide-based display, into which scanning and collimating light beams from the image projection assembly are fed via an internal coupling (IC) element and emitted from the surface of the optical waveguide-based display toward the user's eye, thereby producing, for example, an image at a single optical viewing distance closer than infinity (e.g., the length of an arm), images at multiple discrete optical viewing distances or focal planes, and / or stacked image layers at multiple viewing distances or focal planes to represent a three-dimensional object.

[0007] In head-mounted VR / AR / MR systems, assuming a fixed interpupillary distance (i.e., the distance from the final surface of the display screen to the user's single or double eyelid), it is crucial that the user's entrance pupil (i.e., the anatomical pupil image as seen through the cornea) is aligned with and similar in size to the display screen's exit pupil (i.e., the width of the cone of light available to the user's eye) in order to properly couple the device to the user's single eye (monocular array) or double eyelid (binocular array). A display screen exit pupil smaller than the user's entrance pupil will often result in a vignetted or eclipsed image, while a display screen exit pupil larger than the user's entrance pupil will waste some light but allow eye movement without image vignetting or eclipsation.

[0008] To increase the wearability and comfort of head-mounted VR / AR / MR systems, it is desirable to miniaturize the image source and, if any, the image projection assembly as much as possible. Such an image projection assembly, without intervention, would result in an exit pupil much smaller than the entrance pupil of some eyes, assuming a reasonable interpupillary distance between the eye and the display screen. Therefore, the optics should be integrated into the display subsystem to effectively extend the exit pupil of the display screen and match it to the entrance pupil of the user's eye. That is, the exit pupil of the display screen should create an "eyebox" that is slightly larger (e.g., 10 mm) than the entrance pupil of the user's eye (e.g., 5-7 mm), allowing eye movement within that eyebox to maintain a full view of the image presented by the display screen.

[0009] In addition to matching the exit pupil of the display screen with the entrance pupil of the user's eye, it is desirable to maximize angular resolution, minimize depth of field, and maximize wavefront density of the display screen within the VR / AR / MR system. Maximizing angular resolution results in sharper and more lifelike virtual images, maximizing wavefront density mitigates image artifacts (such as the "screen door" effect (grid-like patterns and non-uniformity)), and minimizing depth of field allows the user to more easily adjust to the virtual content on which they are currently focused. In other words, the smaller the depth of field, the easier it is for the eye to adjust to the virtual content, providing a more natural visual real-world experience, while the larger the depth of field, the more difficult it is for the eye to adjust to the virtual content, resulting in a less natural, and possibly nauseating, visual experience.

[0010] Therefore, there remains a need to provide a display screen for VR / AR / MR systems that can produce a highly saturated light beamlet array exit pupil that matches the user's eye's entrance pupil without compromising the wearability of the VR / AR / MR system.

[0011] The brain's visual center obtains valuable perceptual information from the movement of both eyes and their components relative to each other. The convergence and divergence movements of the two eyes relative to each other (i.e., the rotational movement of the pupils toward or away from each other to converge the line of sight of the eyes onto an object and fixate on it) are closely related to the focusing (or "accommodation") of the eye's lens. Under normal conditions, changing the focus of the eye's lens, or accommodating the eyes to focus on an object at a different distance, will automatically produce a consistent change in convergence and divergence to the same distance, under a relationship known as the "accommodation-convergence-divergence reflex." Similarly, changes in convergence and divergence will, under normal conditions, induce a consistent change in accommodation. Actions that oppose this reflex are known to cause eye strain, headaches, or other forms of discomfort in the user, as is the case in most conventional stereoscopic VR / AR / MR configurations.

[0012] Stereoscopic wearable glasses generally feature two displays for the left and right eyes, configured to display images with slightly different element presentations so that a three-dimensional viewpoint is perceived by the human visual system. Such configurations have been found to be uncomfortable for many users due to inconsistencies between convergence / divergence movements and accommodation ("convergence / divergence-accommodation collision"), which must be overcome to perceive images in three dimensions. In fact, some VR / AR / MR users cannot tolerate stereoscopic configurations. Therefore, most conventional VR / AR / MR systems are not optimally suited to presenting rich binocular three-dimensional experiences / scenarios in a manner that would be comfortable and most useful for the user, partly because conventional systems cannot address some of the fundamental aspects of the human perceptual system, including convergence / divergence-accommodation collision.

[0013] One possible approach to address these problems (including convergence / divergence motion and near-accommodative collisions) is to project the image onto multiple depth planes. To implement this type of system, one approach is to direct light to the user's eye using multiple optical stimulators so that the light appears to originate from multiple depth planes. The optical stimulators are designed to internally couple virtual light corresponding to digital or virtual objects, propagate it via total internal reflection ("TIR"), and then externally couple the virtual light to display the digital or virtual object to the user's eye. In AR / MR systems, the optical stimulators are also designed to be transparent to light from (e.g., reflected from) real-world objects. Thus, some of the optical stimulators are designed to be transparent to real-world light from real-world objects while reflecting virtual light for propagation via TIR.

[0014] Various optical systems generate images at various depths to display VR / AR / MR scenarios. Some such optical systems are described in U.S. Utility Patent Application No. 14 / 555,585 (the contents of which are incorporated above by reference). Some VR / AR / MR systems employ a wearable display device (e.g., a head-mounted display, a helmet-mounted display, or smart glasses) that is at least loosely coupled to the user's head and therefore moves with the user's head.

[0015] Some three-dimensional ("3-D") optical systems, such as those in VR / AR / MR systems, optically render virtual objects. The objects are "virtual" in that they are not actual physical objects located in separate positions within 3-D space. Instead, the virtual objects exist only within the viewer's and / or listener's brain (e.g., the visual cortex) when stimulated by a beam of light directed towards the viewer's eyes.

[0016] VR / AR / MR systems must also be capable of displaying virtual digital content to the user at various perceived positions and distances. The design of VR / AR / MR systems presents numerous other challenges, including the system speed in delivering virtual digital content, the quality of the virtual digital content, the user's pupil distance (addressing convergence / divergence motion - near-to-far accommodation collisions), the system size and portability, as well as other system and optical challenges.

[0017] Furthermore, VR / AR / MR systems must be capable of displaying virtual digital content in sharp focus in order to generate the photorealistic images required for a realistic, immersive, and enjoyable VR / AR / MR experience / scenario. The lens of the eye must change shape (i.e., adjust) to better focus on the image or a portion of it.

[0018] The size limitations of head-mounted displays also result in image resolution limitations. Head-mounted VR / AR / MR display systems, such as those described in U.S. Utility Model Patent Application No. 14 / 555,585 (the contents of which are incorporated above by reference), display images to the user using a light beam transmitted by TIR through an optical guiding element that preserves the light beam angle. The light beam diameter remains essentially the same through the optical guiding element. The size limitations of the head-mounted display limit the size of various optical components (e.g., light source, optical guiding element, lens, etc.), which limits the diameter of the light beam produced by the head-mounted display. These light beam diameter limitations result in the resolution and FOV limitations described above.

[0019] The systems and methods described herein are configured to address these challenges. [Overview of the project] [Means for solving the problem]

[0020] According to a first aspect of this disclosure, a virtual image generation system comprises a planar optical waveguide (which may be a single integrated substrate) having opposing first and second surfaces, and an internal coupling (IC) element configured to optically couple a collimated light beam from an image projection assembly into the planar optical waveguide as an internally coupled light beam. The image projection assembly may include a scanning device configured to scan the collimated light beam.

[0021] The virtual image generation system further comprises a first orthogonal pupil expansion (OPE) element associated with a first surface of a planar optical waveguide to split an internally coupled light beam into a first set of orthogonal light beamlets, and a second orthogonal pupil expansion (OPE) element associated with a second surface of the planar optical waveguide to split an internally coupled light beam into a second set of orthogonal light beamlets. In some embodiments, the first OPE element is located on the first surface of the planar optical waveguide, and the second OPE element is located on the second surface of the planar optical waveguide. The IC element may be configured to optically couple a collimated beam from an image projection assembly to a first optical path that alternately intersects the first and second OPE elements via total internal reflection (TIR) ​​within a planar optical waveguide, such that a portion of the internally coupled beam is deflected as a separate first set of orthogonal beamlets and a second set of orthogonal beamlets propagating through the plane optical waveguide via TIR. In this case, the second parallel optical path may be orthogonal to the first optical path.

[0022] The virtual image generation system further includes an exit pupil expansion (EPE) element associated with a planar optical waveguide to divide a set of first and second orthogonal optical beamlets into an array of externally coupled optical beamlets (e.g., a two-dimensional externally coupled optical beamlet array) that exits the planar optical waveguide. The collimated optical beam may define an entrance pupil, and the externally coupled optical beamlet array may define an exit pupil larger than the entrance pupil, for example, at least 10 times larger than the entrance pupil, or even at least 100 times larger than the entrance pupil.

[0023] In some embodiments, the EPE element is disposed on one of the first and second surfaces of the planar optical waveguide. The set of first orthogonal light beamlets and the set of second orthogonal light beamlets may intersect the EPE element such that some of the set of first orthogonal light beamlets and the set of second orthogonal light beamlets are deflected out of the planar optical waveguide as an external coupled light beamlet array. In some embodiments, the EPE element is configured to impart a convex wavefront profile onto an external coupled light beamlet array that exits the planar optical waveguide. In this case, the convex wavefront profile may have the center of the radius at the focus point to produce an image on a given focal plane. In another embodiment, the IC element, the OPE element, and the EPE element are each diffractive.

[0024] According to a second aspect of the present disclosure, a virtual image generation system includes a plurality of substrates including a primary substrate having a first thickness and at least two secondary substrates having a second thickness, and at least two semi-reflective interfaces disposed between the substrates, and includes a planar optical waveguide.

[0025] In some embodiments, each of the second thicknesses is less than the first thickness. For example, the first thickness may be at least twice each of the second thicknesses. In another embodiment, the second thicknesses are substantially equal to each other. In an alternative embodiment, two or more of the secondary substrates have second thicknesses that are not equal to each other. In this case, at least two of the unequal second thicknesses may be non-multiples of each other. In yet another embodiment, the first thickness is a non-multiple of at least one of the second thicknesses and may be a non-multiple of each of the second thicknesses. In yet another embodiment, at least two of the plurality of secondary substrates have second thicknesses that are not substantially equal to each other.

[0026] In yet another embodiment, each of the semi-reflective interfaces comprises a semi-reflective coating, which may be disposed between the substrates via, for example, one of physical vapor deposition (PVD), ion-assisted deposition (IAD), and ion beam sputtering (IBS). The coatings may each consist of, for example, one or more of metals (such as Au, Al, Ag, Ni-Cr, Cr, etc.), dielectrics (oxides, fluorides, and sulfides), and semiconductors (such as Si, Ge). In yet another embodiment, adjacent ones of the substrates are made of materials having different refractive indices.

[0027] The virtual image generation system further comprises an internal coupling (IC) element configured to optically couple a collimated light beam from an image projection assembly as an internally coupled light beam within a planar optical waveguide for propagation. The image projection assembly may comprise a scanning device configured to scan the collimated light beam. The semi-reflective interface is configured to split the internally coupled light beam into a plurality of primary light beamlets propagating within the primary substrate.

[0028] The virtual image generation system further comprises one or more diffractive optical elements (DOEs) associated with the planar optical waveguide for further splitting the plurality of primary light beamlets into an array of externally coupled light beamlets (e.g., a two-dimensional array of externally coupled beamlets) exiting from the surface of the planar optical waveguide. The collimated light beam may define an entrance pupil, and the externally coupled light beamlet array may define an exit pupil larger than the entrance pupil, for example, at least 10 times larger than the entrance pupil, or further, at least 100 times larger than the entrance pupil. In some embodiments, the first thickness of the primary substrate and the second thickness of the secondary substrate are selected such that the spacing between the centers of at least two adjacent ones of the externally coupled light beamlets is no greater than the width of the collimated light beam. In another embodiment, the first thickness and the second thickness are selected such that a gap greater than half of adjacent ones of the externally coupled light beamlets does not reside at the edge.

[0029] In some embodiments, the semi-reflective interface is configured to split an internally coupled beam into at least two internally coupled beamlets. In this case, the DOE comprises orthogonal pupil extension (OPE) elements, each configured to split at least two internally coupled beamlets into at least two sets of orthogonal beamlets, the semi-reflective interface is configured to further split the sets of at least two sets of orthogonal beamlets into at least four sets of orthogonal beamlets, and the DOE comprises exit pupil extension (EPE) elements, each configured to split the sets of at least four sets of orthogonal beamlets into a set of externally coupled beamlets. The OPE and EPE elements may be positioned on the surface of the optical plane waveguide.

[0030] At least two internally coupled beamlets may propagate through the plane optical waveguide along a first optical path intersecting the OPE element via total internal reflection (TIR) ​​such that portions of at least two internally coupled beamlets propagate through the plane optical waveguide along a second parallel optical path via TIR. The second parallel optical path may be orthogonal to the first optical path. The set of at least two orthogonal beamlets may intersect the EPE element such that portions of the set of at least two orthogonal beamlets are diffracted as a set of beamlets that are externally coupled outward from the plane of the plane optical waveguide. In some embodiments, the EPE element may be configured to impart a convex wavefront profile onto the externally coupled beamlet array emanating from the plane optical waveguide. In this case, the convex wavefront profile may have its radius center at the focal point and produce an image on a given focal plane.

[0031] According to a third aspect of this disclosure, the virtual image generation system includes a plane optical waveguide comprising a plurality of substrates, each including a primary substrate having a first thickness and at least one secondary substrate, each having at least one second thickness, and each substrate having at least one semi-reflective interface disposed between the substrates.

[0032] The first thickness is at least twice each of at least one second thickness. In some embodiments, the first thickness is a non-multiple of each of the second thicknesses. In another embodiment, the secondary substrate comprises a plurality of secondary substrates. In this case, the second thicknesses may be equal to each other, or two or more of the secondary substrates may have second thicknesses that are not equal to each other. The first thickness may be a non-multiple of at least one of the second thicknesses. At least two of the non-equal second thicknesses may be non-multiples of each other.

[0033] In some embodiments, each semi-reflective interface is provided with a semi-reflective coating, which may be disposed between substrates, for example, via one of physical vapor deposition (PVD), ion-assisted vapor deposition (IAD), and ion beam sputtering (IBS). Each coating may consist of one or more of the following: metals (Au, Al, Ag, Ni-Cr, Cr, etc.), dielectrics (oxides, fluorides, and sulfides), and semiconductors (Si, Ge). In yet another embodiment, adjacent substrates are made of materials having different refractive indices.

[0034] The virtual image generation system further includes an internal coupling (IC) element configured to optically couple a collimated light beam from an image projection assembly as an internally coupled light beam within a planar optical waveguide for propagation. The image projection assembly may include a scanning device configured to scan the collimated light beam. A semi-reflective interface is configured to split the internally coupled light beam into a plurality of primary light beamlets that propagate within the primary substrate.

[0035] The virtual image generation system further comprises one or more diffractive optical elements (DOEs) associated with the planar optical waveguide to further divide a plurality of primary light beamlets into an array of externally coupled light beamlets (e.g., a two-dimensional externally coupled beamlet array) that exit the plane of the planar optical waveguide. The collimated light beam may define an entrance pupil, and the externally coupled light beamlet array may define an exit pupil larger than the entrance pupil, for example, at least 10 times larger than the entrance pupil, or even at least 100 times larger than the entrance pupil. In some embodiments, the first thickness of the primary substrate and the second thickness of the secondary substrate are selected such that the distance between the centers of at least two adjacent externally coupled light beamlets is less than or equal to the width of the collimated light beam. In another embodiment, the first and second thicknesses are selected so that no gaps exceeding half of the adjacent externally coupled light beamlets reside between the edges.

[0036] In some embodiments, the semi-reflective interface is configured to split an internally coupled beam into at least two internally coupled beamlets. In this case, the DOE comprises orthogonal pupil extension (OPE) elements, each configured to split at least two internally coupled beamlets into at least two sets of orthogonal beamlets, the semi-reflective interface is configured to further split the sets of at least two sets of orthogonal beamlets into at least four sets of orthogonal beamlets, and the DOE comprises exit pupil extension (EPE) elements, each configured to split the sets of at least four sets of orthogonal beamlets into a set of externally coupled beamlets. The OPE and EPE elements may be positioned on the surface of the optical plane waveguide.

[0037] At least two internally coupled beamlets may propagate through the plane optical waveguide along a first optical path intersecting the OPE element via total internal reflection (TIR) ​​such that portions of at least two internally coupled beamlets propagate through the plane optical waveguide along a second parallel optical path via TIR. The second parallel optical path may be orthogonal to the first optical path. The set of at least two orthogonal beamlets may intersect the EPE element such that portions of the set of at least two orthogonal beamlets are diffracted as a set of beamlets that are externally coupled outward from the plane of the plane optical waveguide. In some embodiments, the EPE element may be configured to impart a convex wavefront profile onto the externally coupled beamlet array emanating from the plane optical waveguide. In this case, the convex wavefront profile may have its radius center at the focal point and produce an image on a given focal plane.

[0038] According to a fourth aspect of the present disclosure, a virtual image generation system comprises a pre-pupil dilation (PPE) element configured to receive a collimating light beam from an imaging element and to split the collimating light beam into a set of initial externally coupled light beamlets. The virtual image generation system further comprises a planar optical waveguide, an internal coupling (IC) element configured to optically couple the initial set of externally coupled light beamlets into the planar optical waveguide as a set of internally coupled light beamlets, and one or more diffraction elements associated with the planar optical waveguide to split the set of internally coupled light beamlets into a set of final externally coupled light beamlets exiting from the surface of the planar optical waveguide. The diffraction elements may also comprise an orthogonal pupil dilation (OPE) element associated with the planar optical waveguide to further split the set of internally coupled light beamlets into a set of orthogonal light beamlets, and an exit pupil dilation (EPE) element associated with the planar optical waveguide to split the set of orthogonal light beamlets into a set of final externally coupled light beamlets.

[0039] In some embodiments, a collimated light beam defines the entrance pupil, an initial set of externally coupled light beamlets defines a pre-expanded pupil larger than the entrance pupil, and a final set of externally coupled light beamlets defines an exit pupil larger than the pre-expanded pupil. In one embodiment, the pre-expanded pupil is at least 10 times larger than the entrance pupil, and the exit pupil is at least 10 times larger than the pre-expanded pupil. In some embodiments, the initial set of externally coupled light beamlets is optically coupled into a planar optical waveguide as a two-dimensional light beamlet array, and the final set of externally coupled light beamlets exits from the surface of the planar optical waveguide as a two-dimensional light beamlet array. In another embodiment, the initial set of externally coupled light beamlets is optically coupled into a planar optical waveguide as a one-dimensional light beamlet array, and the final set of externally coupled light beamlets exits from the surface of the planar optical waveguide as a two-dimensional light beamlet array.

[0040] In some embodiments, the PPE element comprises a miniature planar optical waveguide, a miniature OPE element associated with the miniature planar optical waveguide to split a collimated light beam into a set of initial orthogonal light beamlets, and a miniature EPE element associated with the miniature planar optical waveguide to split the set of initial orthogonal light beamlets into a set of initial externally coupled light beamlets that exit the surface of the miniature planar optical waveguide. The PPE may further comprise a miniature IC element configured to optically couple the collimated light beam into the planar optical waveguide.

[0041] In another embodiment, the PPE element comprises a diffraction beam splitter (e.g., a 1×N beam splitter or an M×N beam splitter) configured to split a collimated light beam into an initial set of diverging light beamlets, and a lens (e.g., a diffraction lens) configured to recollimate the initial set of diverging light beamlets into an initial set of externally coupled light beamlets.

[0042] In yet another embodiment, the PPE element comprises a prism (e.g., a solid prism or a hollow prism) configured to split the collimated light beam into a set of internally coupled light beamlets. The prism may comprise a semi-reflective prism plane configured to split the collimated light beam into a set of internally coupled light beamlets. The prism may comprise a plurality of parallel prism planes configured to split the collimated light beam into a set of internally coupled light beamlets. In this case, the parallel prism planes may comprise a semi-reflective prism plane. The plurality of parallel prism planes may comprise a perfectly reflective prism plane, in which case a portion of the collimated light beam may be reflected in a first direction by at least one semi-reflective prism, and a portion of the collimated light beam may be transmitted to the perfectly reflective prism plane for reflection in the first direction. The prism may comprise a first set of parallel prism planes configured to split the collimated light beam into a set of initial orthogonal light beamlets reflected in a first direction, and a second set of parallel prism planes configured to split the initial orthogonal light beamlets into a set of internally coupled light beamlets reflected in a second direction different from the first direction. The first and second directivity planes may be mutually orthogonal.

[0043] In yet another embodiment, the PPE element comprises a first planar optical waveguide assembly configured to split a collimated light beam into a two-dimensional array of externally coupled light beamlets (e.g., an N×N light beamlet array) that exits from the face of the first planar optical waveguide assembly, and a second planar optical waveguide assembly configured to split the two-dimensional array of externally coupled light beamlets into a plurality of two-dimensional arrays of externally coupled light beamlets that exit from the face of the second planar optical waveguide assembly as a set of internally coupled light beamlets. The first and second planar optical waveguide assemblies may each have unequal thicknesses.

[0044] A two-dimensional externally coupled optical beamlet array has an inter-beamlet spacing, and multiple two-dimensional externally coupled optical beamlet arrays are spatially offset from each other by an inter-array spacing that differs from the inter-beamlet spacing of the two-dimensional externally coupled optical beamlet array. In some embodiments, the inter-array spacing of multiple two-dimensional externally coupled optical beamlet arrays and the inter-beamlet spacing of the two-dimensional externally coupled optical beamlet arrays are not multiples of each other. The inter-array spacing of multiple two-dimensional externally coupled optical beamlet arrays may exceed the inter-beamlet spacing of the two-dimensional externally coupled optical beamlet array.

[0045] In some embodiments, the first planar optical waveguide assembly comprises a first planar optical waveguide having opposing first and second surfaces; a first internal coupling (IC) element configured to optically couple a collimated light beam within the first planar optical waveguide along a first optical path via total internal reflection (TIR) ​​for propagation; and a first exit pupil expander (E) associated with the first planar optical waveguide to split the collimated light beam into a one-dimensional light beamlet array exiting from the second surface of the first planar optical waveguide. The system comprises a second planar optical waveguide having a PE) element and opposing first and second faces, a second IC element configured to optically couple a one-dimensional optical beamlet array within the second planar optical waveguide via TIR along a separate second optical path perpendicular to the first optical path for propagation, and a second exit pupil expander (EPE) element associated with the second planar optical waveguide to split the one-dimensional optical beamlet array into a two-dimensional optical beamlet array exiting from the second face of the second planar optical waveguide. In this case, the first face of the second planar optical waveguide may be attached to the second face of the first planar optical waveguide. The first and second planar optical waveguides may each have substantially equal thicknesses.

[0046] The second planar optical waveguide assembly comprises a third planar optical waveguide having opposing first and second faces, a third IC element configured to optically couple a first two-dimensional optical beamlet array within the third planar optical waveguide via TIR along separate third optical paths for propagation, and a third EPE element associated with the third planar optical waveguide to divide the two-dimensional optical beamlet array into multiple two-dimensional optical beamlet arrays exiting from the second face of the third planar optical waveguide, and opposing first and second The system may also include a fourth planar optical waveguide having two faces, a fourth IC element configured to optically couple a plurality of two-dimensional optical beamlet arrays within the fourth planar optical waveguide via a TIR along a separate fourth optical path perpendicular to the third optical path for propagation, and a fourth EPE element associated with the fourth planar optical waveguide to divide the plurality of two-dimensional optical beamlet arrays into a plurality of two-dimensional optical beamlet arrays that exit from the second face of the fourth planar optical waveguide as an input set of optical beamlets. In this case, the first face of the fourth planar optical waveguide may be attached to the second face of the third planar optical waveguide, and the first face of the third planar optical waveguide may be attached to the second face of the second planar optical waveguide. The first and second planar optical waveguides may each have substantially equal thickness, and the third and fourth planar optical waveguides may each have substantially equal thickness. In this case, the substantially equal thicknesses of the first and second planar optical waveguides may differ from the substantially equal thicknesses of the third and fourth planar optical waveguides. The equal thicknesses of the third and fourth planar optical waveguides may exceed the equal thicknesses of the first and second planar optical waveguides.

[0047] In some embodiments, the mixed reality system includes a light source configured to generate a virtual light beam. The system also includes an optical stimulating optical element having an incident portion, an exit portion, a first optical stimulating optical sub-element, and a second optical stimulating optical sub-element. The first optical stimulating optical sub-element has a first thickness, and the second optical stimulating optical sub-element has a second thickness different from the first thickness.

[0048] In one or more embodiments, the light source and the optical stimulator are configured such that a virtual light beam enters the optical stimulator through an incident portion, propagates through the optical stimulator by substantially total internal reflection, and is divided into a plurality of virtual light beamlets. At least a portion of the plurality of virtual light beamlets may exit the optical stimulator through an exit portion. The optical stimulator may be transparent to a real-world light beam.

[0049] In one or more embodiments, neither the first ratio of the first and second thicknesses nor the second ratio of the second and first thicknesses is an integer. The incident portion may include an internally coupled grating on the first optical stimulating sub-element. The exit portion may include an exit pupil expander on the first optical stimulating sub-element. The second optical stimulating sub-element does not have to cover the exit pupil expander on the first optical stimulating sub-element.

[0050] In one or more embodiments, the second thickness of the second optical sub-element promotes substantially total internal reflection of light having a predetermined wavelength. The predetermined wavelength may be 515 nm to 540 nm. The predetermined wavelength may be 520 nm or 532 nm. The predetermined wavelength may be 475 nm or 650 nm. The second thickness of the second optical sub-element may promote substantially total internal reflection of a light beam substantially parallel to the optical axis of the system to a greater extent than that of a light beam oblique to the optical axis.

[0051] In one or more embodiments, a second optical sub-element covers substantially the entirety of the first optical sub-element. The second thickness may be substantially equal to an integer multiple of the wavelength of the virtual light beam. The second thickness may be an integer multiple of 475 nm, 520 nm, or 650 nm.

[0052] In one or more embodiments, the first and second optical sub-elements each include a separate substantially flat sheet such that the optical sub-element includes a stack of substantially flat sheets. The optical sub-element may also have a refractive index gap between the first and second optical sub-elements. The refractive index gap may be an air layer.

[0053] In one or more embodiments, the second optical sub-element includes two reflective surfaces that reflect light in substantially the same direction. The second optical sub-element may also include two reflective surfaces that reflect light in substantially opposite directions. The system may also include a third optical sub-element.

[0054] In another embodiment, the mixed reality system includes a light source configured to generate a virtual light beam. The system also includes an optical stimulating optical element having an incident portion, an exit portion, a first optical stimulating optical sub-element, and a second optical stimulating optical sub-element. The first optical stimulating optical sub-element has a first diffraction coefficient. The second optical stimulating optical sub-element has a second diffraction coefficient different from the first diffraction coefficient.

[0055] In one or more embodiments, the light source and the optical stimulator are configured such that a virtual light beam enters the optical stimulator through an incident portion, propagates through the optical stimulator by substantially total internal reflection, and is divided into a plurality of virtual light beamlets. At least a portion of the plurality of virtual light beamlets exit the optical stimulator through an exit portion. The optical stimulator may be transparent to the real-world light beam.

[0056] In one or more embodiments, neither the first ratio of the first and second diffraction rates nor the second ratio of the second and first diffraction rates is an integer. The incident portion may include an internally coupled grating on the first optically stimulating sub-element. The exit portion may include an exit pupil expander on the first optically stimulating sub-element. The second optically stimulating sub-element does not have to cover the exit pupil expander on the first optically stimulating sub-element.

[0057] In one or more embodiments, the second diffraction rate of the second optical sub-element promotes substantially total internal reflection of light having a predetermined wavelength. The predetermined wavelength may be 515 nm to 540 nm. The predetermined wavelength may be 520 nm or 532 nm. The predetermined wavelength may be 475 nm or 650 nm.

[0058] In one or more embodiments, the second diffraction coefficient of the second optical stimulating sub-element enhances the substantially total internal reflection of a light beam substantially parallel to the optical axis of the system to a greater extent than that of a light beam oblique to the optical axis. The second optical stimulating sub-element may cover substantially all of the first optical stimulating sub-element.

[0059] In one or more embodiments, the first and second optical sub-elements each include a separate substantially flat sheet such that the optical sub-element includes a stack of substantially flat sheets. The optical sub-element may also have a refractive index gap between the first and second optical sub-elements. The refractive index gap may be an air layer.

[0060] In one or more embodiments, the second optical sub-element includes two reflective surfaces that reflect light in substantially the same direction. The second optical sub-element may also include two reflective surfaces that reflect light in substantially opposite directions. The system may also include a third optical sub-element.

[0061] In yet another embodiment, the mixed reality system includes a light source configured to generate a virtual light beam. The system also includes an optical stimulating element having an incident portion, an orthogonal pupil expander, and a plurality of exit pupil expanders. The light source and the optical stimulating element are configured such that the virtual light beam is incident on the optical stimulating element through the incident portion, propagates through the optical stimulating element by substantially total internal reflection, and splits into a plurality of first virtual light beamlets by interacting with the orthogonal pupil expander, and the plurality of first virtual light beamlets are incident on individual of the plurality of exit pupil expanders and split into a plurality of second virtual light beamlets by interacting with the plurality of exit pupil expanders. At least a portion of the plurality of second virtual light beamlets exit from the optical stimulating element through the exit pupil expander.

[0062] In one or more embodiments, the light-guiding optical element is transparent to a real-world light beam. Each of the multiple exit pupil expanders may include a substantially flat sheet, such that the multiple exit pupil expanders include a stack of substantially flat sheets.

[0063] In one or more embodiments, the orthogonal pupil expander facilitates the substantial total internal reflection of light having a predetermined wavelength. The predetermined wavelength may be 515 nm to 540 nm. The predetermined wavelength may be 520 nm or 532 nm. The predetermined wavelength may be 475 nm or 650 nm.

[0064] In one or more embodiments, the system also includes a plurality of light blockers that selectively block light to a plurality of exit pupil expanders. The plurality of light blockers may include LC shutters or PDLC external coupling gratings. At least one of the plurality of light blockers may be positioned adjacent to the edge of the orthogonal pupil expander. At least one of the plurality of light blockers may be positioned adjacent to the central portion of the orthogonal pupil expander.

[0065] In yet another embodiment, the mixed reality system includes a light source configured to generate a virtual light beam. The system also includes an optical stimulator having an incident portion, an orthogonal pupil expander, and an exit portion. The light source and optical stimulator are configured such that the virtual light beam enters the optical stimulator through the incident portion, propagates through the optical stimulator by substantially total internal reflection, and is split into a plurality of virtual light beamlets by interacting with the orthogonal pupil expander. At least a portion of the plurality of virtual light beamlets exits the optical stimulator through the exit portion.

[0066] In one or more embodiments, the orthogonal pupil expander includes a first orthogonal pupil sub-expander and a second orthogonal pupil sub-expander. The first and second orthogonal pupil sub-expanders each divide the light beam incident on the individual first and second orthogonal pupil sub-expanders. The first and second orthogonal pupil sub-expanders may each be individual flat sheets. The first and second orthogonal pupil sub-expanders may be stacked on top of each other.

[0067] In one or more embodiments, the first orthogonal pupil subexpander includes a first exit rim for directing the beamlet into the second orthogonal pupil subexpander. The first exit rim may include a mirror. The first orthogonal pupil subexpander may also include a second exit rim for directing the beamlet into the second orthogonal pupil subexpander. The first and second exit rims may each include separate mirrors.

[0068] In one or more embodiments, the orthogonal pupil expander includes first and second reflective rims. The first and second reflective rims may be orthogonal to each other. The orthogonal pupil expander may also include a third reflective rim.

[0069] In one or more embodiments, the orthogonal pupil expander includes an internally coupled grating and a high-diffraction region located opposite the internally coupled grating. The orthogonal pupil expander may include a first optical modifier configured to absorb light within a first wavelength range. The orthogonal pupil expander may also include a second optical modifier configured to absorb light within a second wavelength range. The first and second optical modifiers may be orthogonal to each other.

[0070] In one or more embodiments, the orthogonal pupil expander also includes a third optical modifier configured to absorb light within a third wavelength range. The orthogonal pupil expander may include diffractive optical elements that form a "V" shape. The orthogonal pupil expander may include a plurality of PDLC switches.

[0071] In yet another embodiment, the mixed reality system includes a light source configured to generate a virtual light beam. The system also includes an optical stimulating optical element having an incident portion, an outgoing portion, a first optical stimulating optical sub-element, and a second optical stimulating optical sub-element. The first optical stimulating optical sub-element has a first optical modification characteristic. The second optical stimulating optical sub-element has a second optical modification characteristic that is different from the first optical modification characteristic.

[0072] The virtual image generation system comprises a plane optical waveguide having a plurality of substrates, each including a primary substrate having a first thickness and at least two secondary substrates having a second thickness, and at least two semi-reflective interfaces disposed between the substrates. The first thickness may be at least twice each of the second thicknesses. The system further comprises an internal coupling (IC) element configured to optically couple a collimated light beam as an internally coupled light beam within the plane optical waveguide for propagation. The semi-reflective interfaces are configured to split the internally coupled light beam into a plurality of primary light beamlets propagating within the primary substrate. The system further comprises one or more diffractive optical elements (DOEs) associated with the plane optical waveguide to further split the plurality of primary light beamlets into an array of externally coupled light beamlets exiting from the surface of the plane optical waveguide.

[0073] The virtual image generation system comprises a pre-pupil dilation (PPE) element configured to receive a collimating light beam from an imaging element and split the collimating light beam into a set of initial externally coupled light beamlets; an internal coupling (IC) element configured to optically couple the set of initial externally coupled light beamlets into a set of internally coupled light beamlets within a planar optical waveguide; and one or more diffraction elements associated with the planar optical waveguide to split the set of internally coupled light beamlets into a set of final externally coupled light beamlets that exit the surface of the planar optical waveguide.

[0074] The mixed reality system includes a light source configured to generate a virtual light beam. The system also includes an optical stimulating element having an incident portion, an exit portion, a first optical stimulating sub-element, and a second optical stimulating sub-element. The first optical stimulating sub-element has a first thickness, and the second optical stimulating sub-element has a second thickness different from the first thickness.

[0075] Additional and other purposes, features, and advantages of this disclosure are described in the embodiments, drawings, and claims for carrying out the invention. This specification also provides, for example, the following items: (Item 1) A virtual image generation system, A planar optical waveguide comprising a plurality of substrates, each including a primary substrate having a first thickness and at least one secondary substrate having at least one second thickness, and at least one semi-reflective interface disposed between the substrates, wherein the first thickness is at least twice the thickness of each of the at least one second thicknesses, An internal coupling (IC) element, wherein the internal coupling (IC) element is configured to optically couple a collimated light beam from an image projection assembly as an internally coupled light beam within the plane optical waveguide for propagation, and the at least one semi-reflective interface is configured to split the internally coupled light beam into a plurality of primary light beamlets propagating within the primary substrate, One or more diffractive optical elements (DOEs), wherein the one or more diffractive optical elements (DOEs) are associated with the plane optical waveguide to further divide the plurality of primary light beamlets into an array of externally coupled light beamlets that exit the plane optical waveguide. A virtual image generation system equipped with the following features. (Item 2) The virtual image generation system according to item 1, wherein the first thickness is a non-multiple of each of the at least one second thickness. (Item 3) The virtual image generation system according to item 1, wherein the at least one secondary substrate comprises a plurality of secondary substrates. (Item 4) The virtual image generation system according to item 3, wherein at least two of the plurality of secondary substrates have a second thickness that is substantially equal to each other. (Item 5) The virtual image generation system according to item 3, wherein at least two of the plurality of secondary substrates have a second thickness that is not substantially equal to each other. (Item 6) The virtual image generation system according to item 5, wherein the first thickness is a non-multiple of at least one of the second thicknesses. (Item 7) The virtual image generation system according to item 5, wherein at least two of the aforementioned unequal second thicknesses are not multiples of each other. (Item 8) The virtual image generation system according to item 1, wherein the first and second thicknesses are selected such that the distance between the centers of at least two adjacent externally coupled light beamlets is less than or equal to the width of the collimated light beam. (Item 9) The virtual image generation system according to item 1, wherein the first and second thicknesses are selected so that no gaps exceeding half of the adjacent externally coupled light beamlets are permanently present between the edges. (Item 10) The virtual image generation system according to item 1, wherein each of the at least one semi-reflective interfaces comprises a semi-reflective coating. (Item 11) The virtual image generation system according to item 10, wherein the at least one semi-reflective coating is placed between the substrates via one of physical vapor deposition (PVD), ion-assisted vapor deposition (IAD), and ion beam sputtering (IBS). (Item 12) The virtual image generation system according to item 10, wherein each of the at least one semi-reflective coatings consists of one or more of the following: metals (Au, Al, Ag, Ni-Cr, Cr, etc.), dielectrics (oxides, fluorides, and sulfides), and semiconductors (Si, Ge). (Item 13) The virtual image generation system according to item 1, wherein adjacent substrates are made of materials having different refractive indices. (Item 14) The virtual image generation system according to item 1, wherein the at least one semi-reflective interface is configured to split the internally coupled beam into at least two internally coupled beamlets, and one or more DOEs each include an orthogonal pupil extension (OPE) element configured to split the at least two internally coupled beamlets into a set of at least two orthogonal beamlets, and the at least one semi-reflective interface is further configured to split the set of at least two orthogonal beamlets into a set of at least four orthogonal beamlets, and one or more DOEs include an exit pupil extension (EPE) element configured to split the set of at least four orthogonal beamlets into a set of externally coupled beamlets. (Item 15) The virtual image generation system according to item 14, wherein the OPE element and EPE element are arranged on the surface of the optical plane waveguide. (Item 16) The virtual image generation system according to item 14, wherein the at least two internally coupled light beamlets propagate through the plane optical waveguide along a first optical path intersecting the OPE element via total internal reflection (TIR), such that a portion of the at least two internally coupled light beamlets propagate through the plane optical waveguide along a second parallel optical path via TIR. (Item 17) The second parallel optical path is the virtual image generation system described in item 16, which is orthogonal to the first optical path. (Item 18) The virtual image generation system according to item 16, wherein the set of at least two orthogonal light beamlets intersects the EPE element such that a portion of the set of at least two orthogonal light beamlets is diffracted as a set of light beamlets externally coupled outward from the plane of the planar optical waveguide. (Item 19) The virtual image generation system according to item 14, wherein the EPE element is configured to impart a convex wavefront profile onto the externally coupled light beamlet array emanating from the planar optical waveguide, the convex wavefront profile having its radius center at the focal point and producing an image on a given focal plane. (Item 20) The virtual image generation system according to item 1, wherein the collimated light beam defines the entrance pupil, and the externally coupled light beamlet array defines an exit pupil larger than the entrance pupil. (Item 21) The virtual image generation system according to item 20, wherein the exit pupil is at least 10 times larger than the entrance pupil. (Item 22) The virtual image generation system according to item 20, wherein the exit pupil is at least 100 times larger than the entrance pupil. (Item 23) The virtual image generation system described in item 1, wherein the externally coupled light beamlet array is a two-dimensional externally coupled light beamlet array. (Item 24) The virtual image generation system according to item 1, further comprising a display subsystem having an image projection assembly configured to generate the collimated light beam. (Item 25) The virtual image generation system according to item 24, wherein the image projection assembly comprises a scanning device configured to scan the collimated light beam. (Item 26) A virtual image generation system, A planar optical waveguide having opposing first and second surfaces, An internal coupling (IC) element configured to optically couple a collimated light beam from an image projection assembly into the planar optical waveguide as an internally coupled light beam, A first orthogonal pupil extension (OPE) element associated with the first surface of the plane optical waveguide is used to split the internally coupled light beam into a first set of orthogonal light beamlets, A second orthogonal pupil extension (OPE) element associated with the second surface of the plane optical waveguide is used to split the internally coupled light beam into a second set of orthogonal light beamlets, To divide the set of first and second orthogonal light beamlets into an array of externally coupled light beamlets emanating from the planar optical waveguide, an exit pupil dilation (EPE) element associated with the planar optical waveguide and A virtual image generation system equipped with the following features. (Item 27) The planar optical waveguide is formed from a single, integrated substrate, as described in item 25 of the virtual image generation system. (Item 28) The virtual image generation system according to item 25, wherein the first OPE element is positioned on the first surface of the plane optical waveguide, and the second OPE element is positioned on the second surface of the plane optical waveguide. (Item 29) The virtual image generation system according to item 25, wherein the EPE element is positioned on one of the first and second surfaces of the planar optical waveguide. (Item 30) The virtual image generation system according to item 25, wherein the IC element is configured to optically couple a collimated light beam from the image projection assembly to the plane optical waveguide as an internally coupled light beam for propagation, along a first optical path that alternately intersects the first OPE element and the second OPE element, via total internal reflection (TIR), along a second parallel optical path, such that a portion of the internally coupled light beam is deflected via TIR as the individual first orthogonal light beams and the second orthogonal light beams propagating through the plane optical waveguide. (Item 31) The second parallel optical path is the virtual image generation system described in item 30, which is orthogonal to the first optical path. (Item 32) The virtual image generation system according to item 25, wherein the first set of orthogonal beamlets and the second set of orthogonal beamlets intersect the EPE element such that a portion of the first set of orthogonal beamlets and the second set of orthogonal beamlets are deflected out of the planar optical waveguide as an externally coupled beamlet array. (Item 33) The virtual image generation system according to item 25, wherein the EPE element is configured to impart a convex wavefront profile onto the externally coupled optical beamlet array emanating from the planar optical waveguide, the convex wavefront profile having its radius center at the focal point and producing an image on a given focal plane. (Item 34) The virtual image generation system according to item 25, wherein the collimated light beam defines the entrance pupil, and the externally coupled light beamlet array defines an exit pupil larger than the entrance pupil. (Item 35) The virtual image generation system according to item 34, wherein the exit pupil is at least 10 times larger than the entrance pupil. (Item 36) The virtual image generation system according to item 34, wherein the exit pupil is at least 100 times larger than the entrance pupil. (Item 37) The virtual image generation system described in item 25, wherein the IC element, OPE element, and EPE element are each diffractive. (Item 38) The virtual image generation system described in item 25, wherein the externally coupled optical beamlet array is a two-dimensional externally coupled optical beamlet array. (Item 39) The virtual image generation system according to item 25, further comprising the image projection assembly. (Item 40) The virtual image generation system according to item 39, wherein the image projection assembly comprises a scanning device configured to scan the collimated light beam. (Item 41) A virtual image generation system, A planar optical waveguide comprising a plurality of substrates, each including a primary substrate having a first thickness and at least two secondary substrates having a second thickness, and at least two semi-reflective interfaces disposed between each of the substrates, An internal coupling (IC) element, wherein the internal coupling (IC) element is configured to optically couple a collimated light beam from an image projection assembly as an internally coupled light beam within the planar optical waveguide for propagation, and the at least two semi-reflective interfaces are configured to split the internally coupled light beam into a plurality of primary light beamlets propagating within the primary substrate, One or more diffractive optical elements (DOEs), wherein the one or more diffractive optical elements (DOEs) are associated with the plane optical waveguide to further divide the plurality of primary light beamlets into an array of externally coupled light beamlets that exit the plane optical waveguide. A virtual image generation system equipped with the following features. (Item 42) The virtual image generation system according to item 41, wherein the second thickness is less than the first thickness. (Item 43) The virtual image generation system according to item 41, wherein the first thickness is at least twice the second thickness. (Item 44) The virtual image generation system according to item 41, wherein the second thickness is substantially equal to each other. (Item 45) The virtual image generation system according to item 41, wherein the first thickness is a non-multiple of at least one of the second thicknesses. (Item 46) The virtual image generation system according to item 41, wherein two or more of the at least two secondary substrates have a second thickness that is not substantially equal to each other. (Item 47) The virtual image generation system according to item 46, wherein the first thickness is a non-multiple of at least one of the second thicknesses. (Item 48) The virtual image generation system according to item 46, wherein at least two of the aforementioned unequal second thicknesses are not multiples of each other. (Item 49) The virtual image generation system according to item 41, wherein the first and second thicknesses are selected such that the distance between the centers of at least two adjacent externally coupled light beamlets is less than or equal to the width of the collimated light beam. (Item 50) The virtual image generation system according to item 41, wherein the first and second thicknesses are selected so that gaps exceeding half of the adjacent externally coupled light beamlets do not permanently reside between the edges. (Item 51) The virtual image generation system according to item 41, wherein each of the at least two semi-reflective interfaces is provided with a semi-reflective coating. (Item 52) The virtual image generation system according to item 51, wherein the at least two semi-reflective coatings are each placed between the substrates via one of physical vapor deposition (PVD), ion-assisted vapor deposition (IAD), and ion beam sputtering (IBS). (Item 53) The virtual image generation system according to item 51, wherein each of the at least two semi-reflective coatings consists of one or more of the following: metals (Au, Al, Ag, Ni-Cr, Cr, etc.), dielectrics (oxides, fluorides, and sulfides), and semiconductors (Si, Ge). (Item 54) The virtual image generation system according to item 41, wherein adjacent substrates are made of materials having different refractive indices. (Item 55) The virtual image generation system according to item 41, wherein the at least two semi-reflective interfaces are configured to split the internally coupled beam into at least two internally coupled beamlets, and one or more DOEs each include an orthogonal pupil extension (OPE) element configured to split the at least two internally coupled beamlets into a set of at least two orthogonal beamlets, and the at least two semi-reflective interfaces are configured to further split the set of at least two orthogonal beamlets into a set of at least four orthogonal beamlets, and one or more DOEs include an exit pupil extension (EPE) element configured to split the set of at least four orthogonal beamlets into a set of externally coupled beamlets. (Item 56) The virtual image generation system according to item 55, wherein the OPE element and EPE element are arranged on the surface of the optical plane waveguide. (Item 57) The virtual image generation system according to item 55, wherein the at least two internally coupled light beamlets propagate through the plane optical waveguide along a first optical path intersecting the OPE element via total internal reflection (TIR) ​​so that a portion of the at least two internally coupled light beamlets propagate through the plane optical waveguide along a second parallel optical path via TIR. (Item 58) The second parallel optical path is the virtual image generation system described in item 57, which is orthogonal to the first optical path. (Item 59) The virtual image generation system according to item 57, wherein the set of at least two orthogonal light beamlets intersects the EPE element such that a portion of the set of at least two orthogonal light beamlets is diffracted as a set of light beamlets externally coupled outward from the plane of the planar optical waveguide. (Item 60) The virtual image generation system according to item 55, wherein the EPE element is configured to impart a convex wavefront profile onto the externally coupled light beamlet array emanating from the planar optical waveguide, the convex wavefront profile having its radius center at the focal point and producing an image on a given focal plane. (Item 61) The virtual image generation system according to item 41, wherein the collimated light beam defines an entrance pupil, and the externally coupled light beamlet array defines an exit pupil larger than the entrance pupil. (Item 62) The virtual image generation system according to item 61, wherein the exit pupil is at least 10 times larger than the entrance pupil. (Item 63) The virtual image generation system according to item 61, wherein the exit pupil is at least 100 times larger than the entrance pupil. (Item 64) The virtual image generation system described in item 41, wherein the externally coupled optical beamlet array is a two-dimensional externally coupled optical beamlet array. (Item 65) The virtual image generation system according to item 41, further comprising a display subsystem having an image projection assembly configured to generate the collimated light beam. (Item 66) The virtual image generation system according to item 65, wherein the image projection assembly comprises a scanning device configured to scan the collimated light beam. (Item 67) A virtual image generation system, A pre-pupil dilation (PPE) element, wherein the pre-pupil dilation (PPE) element is configured to receive a collimated light beam from an imaging element and to split the collimated light beam into a set of initial externally coupled light beamlets, Planar optical waveguide and, An internal coupling (IC) element, wherein the internal coupling (IC) element is configured to optically couple the initial set of externally coupled optical beamlets into the planar optical waveguide as a set of internally coupled optical beamlets, One or more diffraction elements, the one or more diffraction elements being associated with the plane optical waveguide to split the set of internally coupled light beamlets into a set of final externally coupled light beamlets that exit the plane optical waveguide, and A virtual image generation system equipped with the following features. (Item 68) The virtual image generation system according to item 67, wherein the collimated light beam defines the entrance pupil, the initial set of externally coupled light beamlets defines a pre-dilated pupil larger than the entrance pupil, and the final set of externally coupled light beamlets defines an exit pupil larger than the pre-dilated pupil. (Item 69) The virtual image generation system according to item 68, wherein the pre-expanded pupil is at least 10 times larger than the entrance pupil, and the exit pupil is at least 10 times larger than the pre-expanded pupil. (Item 70) The virtual image generation system according to item 67, wherein the initial set of externally coupled optical beamlets is optically coupled into the planar optical waveguide as a two-dimensional optical beamlet array, and the final set of externally coupled optical beamlets is emitted from the surface of the planar optical waveguide as a two-dimensional optical beamlet array. (Item 71) The virtual image generation system according to item 67, wherein the initial set of externally coupled optical beamlets is optically coupled into the plane optical waveguide as a one-dimensional optical beamlet array, and the final set of externally coupled optical beamlets is emitted from the surface of the plane optical waveguide as a two-dimensional optical beamlet array. (Item 72) The virtual image generation system according to item 67, wherein the one or more diffraction elements include an orthogonal pupil dilation (OPE) element associated with the planar optical waveguide to further divide the set of internally coupled light beamlets into an orthogonal light beamlets, and an exit pupil dilation (EPE) element associated with the planar optical waveguide to divide the set of orthogonal light beamlets into an end-out externally coupled light beamlets. (Item 73) The aforementioned PPE element is A small planar optical waveguide, A small OPE element associated with the small plane optical waveguide is used to split the collimated light beam into a set of initial orthogonal light beamlets, A small EPE element associated with the small plane optical waveguide is used to divide the set of initial orthogonal light beamlets into a set of initial externally coupled light beamlets that exit from the surface of the small plane optical waveguide. A virtual image generation system as described in item 72, comprising: (Item 74) The virtual image generation system according to item 73, further comprising a miniature IC element configured to optically couple the collimated light beam into the planar optical waveguide. (Item 75) The aforementioned PPE element is A diffraction beam splitter configured to split the collimated light beam into an initial set of diverging light beamlets, A lens configured to recollimate the initial set of diverging light beamlets into the initial set of externally coupled light beamlets. A virtual image generation system as described in item 67, comprising: (Item 76) The said diffraction beam splitter is a 1×N beam splitter, as described in item 75 of the virtual image generation system. (Item 77) The said diffraction beam splitter is an M×N beam splitter, as described in item 75 of the virtual image generation system. (Item 78) The aforementioned lens is a diffractive lens, as described in item 75 of the virtual image generation system. (Item 79) The virtual image generation system according to item 67, comprising a prism configured to split the collimated light beam into the set of internally coupled light beamlets, wherein the PPE element comprises a prism. (Item 80) The virtual image generation system described in item 79, wherein the prism is a solid prism. (Item 81) The prism is a hollow prism, as described in item 79 of the virtual image generation system. (Item 82) The virtual image generation system according to item 79, wherein the prism comprises a semi-reflective prism plane configured to split the collimated light beam into the set of internally coupled light beamlets. (Item 83) The virtual image generation system according to item 82, wherein the prism comprises a plurality of parallel prism planes configured to split the collimated light beam into the set of internally coupled light beamlets, and the two parallel prism planes comprise the semi-reflective prism plane. (Item 84) The virtual image generation system according to item 83, wherein the plurality of parallel prism planes comprise a perfectly reflective prism plane, a portion of the collimated light beam is reflected in a first direction by the at least one semi-reflective prism, and a portion of the collimated light beam is transmitted to the perfectly reflective prism plane for reflection in the first direction. (Item 85) The virtual image generation system according to item 79, wherein the prism comprises a first set of parallel prism planes configured to split the collimated light beam into a set of initial orthogonal light beamlets reflected in a first direction, and a second set of parallel prism planes configured to split the initial orthogonal light beamlets into a set of internally coupled light beamlets reflected in a second direction different from the first direction. (Item 86) The first and second directions are mutually orthogonal, as described in item 85, in the virtual image generation system. (Item 87) The aforementioned PPE element is A first planar optical waveguide assembly configured to split the collimated light beam into a two-dimensional array of externally coupled light beamlets that exit the surface of the first planar optical waveguide assembly, wherein the two-dimensional array of externally coupled light beamlets has an inter-beamlet spacing between the first planar optical waveguide assembly, A second planar optical waveguide assembly configured to divide the two-dimensional externally coupled optical beamlet array into a plurality of arrays of two-dimensional externally coupled optical beamlets that exit from the surface of the second planar optical waveguide assembly as a set of internally coupled optical beamlets, wherein the plurality of two-dimensional externally coupled optical beamlet arrays are spatially offset from each other by an inter-array spacing that differs from the inter-beamlet spacing of the two-dimensional externally coupled optical beamlet arrays, and A virtual image generation system as described in item 67, comprising: (Item 88) The virtual image generation system described in item 87, wherein the two-dimensional optical beamlet array is an N×N optical beamlet array. (Item 89) The virtual image generation system according to item 87, wherein the inter-array spacing of the plurality of two-dimensional externally coupled optical beamlet arrays and the inter-beamlet spacing of the two-dimensional externally coupled optical beamlet arrays are not multiples of each other. (Item 90) The virtual image generation system according to item 87, wherein the inter-array spacing of the plurality of two-dimensional externally coupled optical beamlet arrays exceeds the inter-beamlet spacing of the two-dimensional externally coupled optical beamlet arrays. (Item 91) The virtual image generation system according to item 87, wherein the first and second planar optical waveguide assemblies each have unequal thicknesses. (Item 92) The first planar optical waveguide assembly is A first planar optical waveguide having opposing first and second surfaces, A first internal coupling (IC) element, the first internal coupling (IC) element is configured to optically couple the collimated light beam in the first plane optical waveguide along a first optical path via total internal reflection (TIR) ​​for propagation, A first exit pupil expander (EPE) element, the first exit pupil expander (EPE) element being associated with the first planar optical waveguide to split the collimated light beam into a one-dimensional light beamlet array that exits from a second surface of the first planar optical waveguide, A second planar optical waveguide having opposing first and second surfaces, A second IC element, the second IC element is configured to optically couple the one-dimensional optical beamlet array via TIR along a separate second optical path perpendicular to the first optical path in the second planar optical waveguide for propagation. A second exit pupil expander (EPE) element, the second exit pupil expander (EPE) element being associated with the second planar optical waveguide to split the one-dimensional optical beamlet array into a two-dimensional optical beamlet array emitting from the second surface of the second planar optical waveguide, and A virtual image generation system as described in item 87, comprising: (Item 93) The virtual image generation system according to item 92, wherein the first surface of the second planar optical waveguide is attached to the second surface of the first planar optical waveguide. (Item 94) The virtual image generation system according to item 92, wherein the first and second planar optical waveguides each have substantially equal thickness. (Item 95) The second planar optical waveguide assembly is, A third planar optical waveguide having opposing first and second surfaces, A third IC element, the third IC element is configured to optically couple the first two-dimensional optical beamlet array via TIR along a separate third optical path within the third planar optical waveguide for propagation. A third EPE element, the third EPE element being associated with the third planar optical waveguide to divide the two-dimensional optical beamlet array into a plurality of two-dimensional optical beamlet arrays emitting from a second surface of the third planar optical waveguide, A fourth planar optical waveguide having opposing first and second surfaces, A fourth IC element, the fourth IC element is configured to optically couple the plurality of two-dimensional optical beamlet arrays in the fourth planar optical waveguide via TIR along a separate fourth optical path perpendicular to the third optical path, for propagation. A fourth EPE element, the fourth EPE element being associated with the fourth planar optical waveguide to divide the plurality of two-dimensional optical beamlet arrays into a plurality of two-dimensional optical beamlet arrays that exit from the second surface of the fourth planar optical waveguide as an input set of optical beamlets, and A virtual image generation system as described in item 92, comprising: (Item 96) The virtual image generation system according to item 95, wherein the first surface of the fourth planar optical waveguide is attached to the second surface of the third planar optical waveguide. (Item 97) The virtual image generation system according to item 96, wherein the first surface of the third planar optical waveguide is attached to the second surface of the second planar optical waveguide. (Item 98) The virtual image generation system according to item 95, wherein the first and second planar optical waveguides each have substantially equal thickness, and the third and fourth planar optical waveguides each have substantially equal thickness. (Item 99) The virtual image generation system according to item 97, wherein the substantially equal thicknesses of the first and second planar optical waveguides differ from the substantially equal thicknesses of the third and fourth planar optical waveguides. (Item 100) The virtual image generation system according to item 99, wherein the substantially equal thicknesses of the third and fourth planar optical waveguides exceed the substantially equal thicknesses of the first and second planar optical waveguides. (Item 101) It is a mixed reality system, A light source configured to generate a virtual light beam, An optically stimulating element having an input portion, an output portion, a first optically stimulating sub-element, and a second optically stimulating sub-element. Equipped with, The first optical sub-element described above has a first thickness, The second optical sub-element having a second thickness different from the first thickness, Mixed reality system. (Item 102) The light source and the optical element that guides the virtual light beam (a) Through the incident portion, light enters the light-guiding optical element, (b) Propagated through the optical element by substantially total internal reflection, (c) Divide into multiple virtual light beamlets The system according to item 101, configured such that at least a portion of the plurality of virtual light beamlets are emitted from the light-stimulating optical element through the emission portion. (Item 103) The system described in item 101, wherein the optically induced optical element is transparent to a real-world light beam. (Item 104) The system according to item 101, wherein neither the first ratio of the first and second thicknesses nor the second ratio of the second and first thicknesses is an integer. (Item 105) The incident portion comprises an internal coupling grating on the first photo-inducing optical sub-element, The exit portion comprises an exit pupil expander on the first light-guiding optical sub-element, The second optical sub-element is not covered by the exit pupil expander on the first optical sub-element. The system described in item 101. (Item 106) The system according to item 101, wherein the second thickness of the second optical sub-element promotes substantially total internal reflection of light having a predetermined wavelength. (Item 107) The system according to item 106, wherein the predetermined wavelength is 515 nm to 540 nm. (Item 108) The system according to item 107, wherein the predetermined wavelength is 520 nm or 532 nm. (Item 109) The system according to item 106, wherein the predetermined wavelength is 475 nm or 650 nm. (Item 110) The system according to item 101, wherein the second thickness of the second optical sub-element promotes substantially total internal reflection of a light beam substantially parallel to the optical axis of the system to a greater extent than that of a light beam oblique to the optical axis. (Item 111) The system according to item 101, wherein the second optical sub-element covers substantially the entirety of the first optical sub-element. (Item 112) The system according to item 111, wherein the second thickness is substantially equal to an integer multiple of the wavelength of the virtual light beam. (Item 113) The system according to item 111, wherein the second thickness is an integer multiple of 475 nm, 520 nm, or 650 nm. (Item 114) The system according to item 101, wherein each of the first and second optical sub-elements comprises a separate substantially flat sheet such that the optical sub-element comprises a stack of substantially flat sheets. (Item 115) The system according to item 114, wherein the optically induced optical element also has a refractive index gap between the first and second optically induced optical sub-elements. (Item 116) The refractive index gap is an air layer, as described in item 115. (Item 117) The system according to item 101, wherein the second light-guiding optical sub-element comprises two reflective surfaces that reflect light in substantially the same direction. (Item 118) The system according to item 101, wherein the second light-guiding optical sub-element comprises two reflective surfaces that reflect light in substantially opposite directions. (Item 119) The system described in item 101, further comprising a third optically induced sub-element. (Item 120) It is a mixed reality system, A light source configured to generate a virtual light beam, An optically stimulating element having an input portion, an output portion, a first optically stimulating sub-element, and a second optically stimulating sub-element. Equipped with, The first optical sub-element having a first diffraction coefficient, The second optical sub-element has a second diffraction coefficient different from the first diffraction coefficient. Mixed reality system. (Item 121) The light source and the optical element that guides the virtual light beam (a) Through the incident portion, light enters the light-guiding optical element, (b) Propagated through the optical element by substantially total internal reflection, (c) Divide into multiple virtual light beamlets The system according to item 120, configured such that at least a portion of the plurality of virtual light beamlets are emitted from the light-stimulating optical element through the emission portion. (Item 122) The system described in item 120, wherein the optically guiding element is transparent to a real-world light beam. (Item 123) The system according to item 120, wherein neither the first ratio of the first and second diffraction rates nor the second ratio of the second and first diffraction rates is an integer. (Item 124) The incident portion comprises an internal coupling grating on the first photo-inducing optical sub-element, The exit portion comprises an exit pupil expander on the first light-guiding optical sub-element, The second optical sub-element is not covered by the exit pupil expander on the first optical sub-element. The system described in item 120. (Item 125) The system according to item 120, wherein the second diffraction rate of the second optical sub-element promotes substantially total internal reflection of light having a predetermined wavelength. (Item 126) The system described in item 125, wherein the predetermined wavelength is 515 nm to 540 nm. (Item 127) The system according to item 126, wherein the predetermined wavelength is 520 nm or 532 nm. (Item 128) The system according to item 125, wherein the predetermined wavelength is 475 nm or 650 nm. (Item 129) The system according to item 120, wherein the second diffraction rate of the second optically stimulated sub-element promotes substantially total internal reflection of a light beam substantially parallel to the optical axis of the system to a greater extent than that of a light beam oblique to the optical axis. (Item 130) The system according to item 120, wherein the second optical sub-element covers substantially the entirety of the first optical sub-element. (Item 131) The system according to item 120, wherein each of the first and second optical sub-elements comprises a separate substantially flat sheet such that the optical sub-element comprises a stack of substantially flat sheets. (Item 132) The system according to item 131, wherein the optically induced optical element also has a refractive index gap between the first and second optically induced optical sub-elements. (Item 133) The refractive index gap is an air layer, as described in item 132. (Item 134) The system according to item 120, wherein the second light-guiding optical sub-element comprises two reflective surfaces that reflect light in substantially the same direction. (Item 135) The system according to item 120, wherein the second light-guiding optical sub-element comprises two reflective surfaces that reflect light in substantially opposite directions. (Item 136) The system described in item 120, further comprising a third optically induced sub-element. (Item 137) It is a mixed reality system, A light source configured to generate a virtual light beam, An optically guiding element having an entrance portion, an orthogonal pupil expander, and a plurality of exit pupil expanders, Equipped with, The light source and the optical element that guides the virtual light beam (a) Through the incident portion, light enters the light-guiding optical element, (b) Propagated through the optical element by substantially total internal reflection, (c) By interacting with the orthogonal pupil expander, it is divided into a plurality of first virtual light beamlets, the plurality of first virtual light beamlets incident on individual of the plurality of exit pupil expanders, (d) Interacting with the plurality of exit pupil expanders, the beam is divided into a plurality of second virtual light beamlets. A mixed reality system configured such that at least a portion of the plurality of second virtual light beamlets are emitted from the light-guiding optical element through the exit pupil expander. (Item 138) The system described in item 137, wherein the optically induced optical element is transparent to a real-world light beam. (Item 139) The system according to item 137, wherein each of the plurality of exit pupil expanders comprises a substantially flat sheet such that the plurality of exit pupil expanders comprises a stack of substantially flat sheets. (Item 140) The system according to item 137, wherein the orthogonal pupil expander facilitates substantially total internal reflection of light having a predetermined wavelength. (Item 141) The system described in item 140, wherein the predetermined wavelength is 515 nm to 540 nm. (Item 142) The system according to item 141, wherein the predetermined wavelength is 520 nm or 532 nm. (Item 143) The system according to item 140, wherein the predetermined wavelength is 475 nm or 650 nm. (Item 144) The system according to item 143, further comprising a plurality of light blockers for selectively blocking light to the plurality of exit pupil expanders. (Item 145) The system according to item 144, wherein the plurality of light blockers comprises LC shutters or PDLC external coupling grids. (Item 146) The system according to item 144, wherein at least one of the plurality of light blockers is positioned adjacent to the edge of the orthogonal pupil expander. (Item 147) The system according to item 144, wherein at least one of the plurality of light blockers is positioned adjacent to the central portion of the orthogonal pupil expander. (Item 148) It is a mixed reality system, A light source configured to generate a virtual light beam, A light-guided optical element having an input portion, an orthogonal pupil expander, and an output portion. Equipped with, The light source and the optical element that guides the virtual light beam (a) Through the incident portion, light enters the light-guiding optical element, (b) Propagated through the optical element by substantially total internal reflection, (c) By interacting with the orthogonal pupil expander, it is divided into multiple virtual light beamlets. A mixed reality system configured such that at least a portion of the plurality of virtual light beamlets are emitted from the light-guided optical element through the emission portion. (Item 149) The orthogonal pupil expander comprises a first orthogonal pupil sub-expander and a second orthogonal pupil sub-expander. The first and second orthogonal pupil subexpanders each divide the light beam incident on the individual first and second orthogonal pupil subexpanders. The system described in item 148. (Item 150) The first and second orthogonal pupil subexpanders are each separate flat sheets, and The first and second orthogonal pupil subexpanders are stacked on top of each other. The system described in item 149. (Item 151) The system according to item 150, wherein the first orthogonal pupil subexpander comprises a first exit rim for directing a beamlet into the second orthogonal pupil subexpander. (Item 152) The system according to item 151, wherein the first ejection edge comprises a mirror. (Item 153) The system according to item 151, wherein the first orthogonal pupil subexpander comprises a second exit edge for directing a beamlet into the second orthogonal pupil subexpander. (Item 154) The system according to item 153, wherein the first and second emission edges each include a separate mirror. (Item 155) The system according to item 148, wherein the orthogonal pupil expander comprises first and second reflective rims. (Item 156) The first and second reflective edges are mutually orthogonal, as per the system described in item 155. (Item 157) The system according to item 155, wherein the orthogonal pupil expander further comprises a third reflective rim. (Item 158) The system according to item 148, wherein the orthogonal pupil expander comprises an internally coupled grating and a high-diffraction region located opposite the internally coupled grating. (Item 159) The system according to item 148, wherein the orthogonal pupil expander comprises a first optical modifier configured to absorb light within a first wavelength range. (Item 160) The system according to item 159, wherein the orthogonal pupil expander further comprises a second optical modifier configured to absorb light within a second wavelength range. (Item 161) The first and second optical correctors are mutually orthogonal, as described in item 160. (Item 162) The system according to item 160, wherein the orthogonal pupil expander further comprises a third optical modifier configured to absorb light within a third wavelength range. (Item 163) The system according to item 148, wherein the orthogonal pupil expander comprises diffractive optical elements that form a "V" shape. (Item 164) The orthogonal pupil expander is the system described in item 148, comprising a plurality of PDLC switches. (Item 165) It is a mixed reality system, A light source configured to generate a virtual light beam, An optically stimulating element having an input portion, an output portion, a first optically stimulating sub-element, and a second optically stimulating sub-element. Equipped with, The first optically induced optical sub-element has a first optical modification characteristic, The second optical sub-element has a second optical modification characteristic that is different from the first optical modification characteristic. Mixed reality system. [Brief explanation of the drawing]

[0076] The drawings illustrate the design and utility of preferred embodiments of the present disclosure, and similar elements are referenced by common reference numbers. To gain a deeper understanding of the aforementioned and other advantages and objectives of the present disclosure, a more detailed description of the invention, briefly mentioned above, will be given by reference to its specific embodiments illustrated in the accompanying drawings. With the understanding that these drawings depict only typical embodiments of the present disclosure and should therefore not be considered as limiting its scope, the present disclosure will be described and presented with additional specificity and detail through the use of the accompanying drawings.

[0077] [Figure 1]Figure 1 is a photograph of a three-dimensional augmented reality scene that can be displayed to an end user by a prior art augmented reality generation device.

[0078] [Figure 2] Figure 2 is a block diagram of a virtual image generation system constructed according to some embodiments of the present disclosure.

[0079] [Figure 3A] Figure 3A is a plan view of one technique that may be used to mount the virtual image generation system shown in Figure 2.

[0080] [Figure 3B] Figure 3B is a plan view of another technique that may be used to mount the virtual image generation system shown in Figure 2.

[0081] [Figure 3C] Figure 3C is a plan view of yet another technique that may be used to mount the virtual image generation system shown in Figure 2.

[0082] [Figure 3D] Figure 3D is a plan view of yet another technique that may be used to mount the virtual image generation system shown in Figure 2.

[0083] [Figure 4] Figures 4, 7, and 8 are detailed schematic diagrams of various mixed reality systems.

[0084] [Figure 5] Figure 5 is a plan view of several embodiments of the display subsystem used in the virtual image generation system of Figure 2.

[0085] [Figure 6] Figure 6 is a conceptual diagram of several embodiments of the primary waveguide apparatus used in the display subsystem of Figure 5. [Figure 7]Figures 4, 7, and 8 are detailed schematic diagrams of various mixed reality systems. [Figure 8] Figures 4, 7, and 8 are detailed schematic diagrams of various mixed reality systems.

[0086] [Figure 9] Figure 9 is a schematic diagram illustrating the focal plane of a mixed reality system.

[0087] [Figure 10] Figure 10 is a detailed schematic diagram of the optically stimulated optical elements of a mixed reality system.

[0088] [Figure 11] Figure 11A is a schematic diagram of a light beam incident on the eye according to various embodiments. Figure 11B is the energy distribution pattern of the corresponding light beam in Figure 11A, which is focused on the retina by the lens, according to various embodiments. [Figure 12] Figure 12A is a schematic diagram of a light beam incident on the eye according to various embodiments. Figure 12B is the energy distribution pattern of the corresponding light beam in Figure 12A, which is focused on the retina by the lens, according to various embodiments. [Figure 13] Figure 13A is a schematic diagram of a light beam incident on the eye according to various embodiments. Figure 13B is the energy distribution pattern of the corresponding light beam in Figure 13A, which is focused on the retina by the lens, according to various embodiments. [Figure 14] Figure 14A is a schematic diagram of a light beam incident on the eye according to various embodiments. Figure 14B is the energy distribution pattern of the corresponding light beam in Figure 14A, which is focused on the retina by the lens, according to various embodiments. [Figure 15] Figure 15A is a schematic diagram of a light beam incident on the eye according to various embodiments. Figure 15B is the energy distribution pattern of the corresponding light beam in Figure 15A, which is focused on the retina by the lens, according to various embodiments.

[0089] [Figure 16A] Figure 16A is a schematic diagram of a light beamlet incident on the eye, according to several embodiments.

[0090] [Figure 16B] Figure 16B shows the energy distribution pattern of the light beamlet in Figure 16A, which is focused onto the retina by the lens, according to several embodiments.

[0091] [Figure 17A] Figure 17A is a schematic diagram of an optically stimulated element that generates an array of beamlets, according to several embodiments.

[0092] [Figure 17B] Figure 17B is a schematic diagram of a light beamlet associated with the pupil formed by the iris, according to several embodiments.

[0093] [Figure 18] Figures 18A-18C are schematic diagrams showing light beamlets on the retina according to various embodiments.

[0094] [Figure 19] Figure 19 is a schematic diagram of an optical beam and beamlet propagating through a beam multiplier tube in several embodiments.

[0095] [Figure 20] Figure 20 is a schematic diagram of a light beam and beamlet propagating into the eye through a beam multiplier tube, according to several embodiments.

[0096] [Figure 21] Figure 21 is a schematic diagram of a light beam and beamlet propagating into the eye through two beam multiplier tubes, according to several embodiments.

[0097] [Figure 22A]Figure 22A-33I is a schematic diagram of optical beams and beamlets propagating through a beam multiplier tube according to various embodiments. [Figure 22B] Figure 22A-33I is a schematic diagram of optical beams and beamlets propagating through a beam multiplier tube according to various embodiments. [Figure 23] Figure 22A-33I is a schematic diagram of optical beams and beamlets propagating through a beam multiplier tube according to various embodiments. [Figure 24] Figure 22A-33I is a schematic diagram of optical beams and beamlets propagating through a beam multiplier tube according to various embodiments. [Figure 25] Figure 22A-33I is a schematic diagram of optical beams and beamlets propagating through a beam multiplier tube according to various embodiments. [Figure 26] Figure 22A-33I is a schematic diagram of optical beams and beamlets propagating through a beam multiplier tube according to various embodiments. [Figure 27] Figure 22A-33I is a schematic diagram of optical beams and beamlets propagating through a beam multiplier tube according to various embodiments. [Figure 28] Figure 22A-33I is a schematic diagram of optical beams and beamlets propagating through a beam multiplier tube according to various embodiments. [Figure 29] Figure 22A-33I is a schematic diagram of optical beams and beamlets propagating through a beam multiplier tube according to various embodiments. [Figure 30] Figure 22A-33I is a schematic diagram of optical beams and beamlets propagating through a beam multiplier tube according to various embodiments. [Figure 31] Figure 22A-33I is a schematic diagram of optical beams and beamlets propagating through a beam multiplier tube according to various embodiments. [Figure 32] Figure 22A-33I is a schematic diagram of optical beams and beamlets propagating through a beam multiplier tube according to various embodiments. [Figure 33-1]Figure 22A-33I is a schematic diagram of optical beams and beamlets propagating through a beam multiplier tube according to various embodiments. [Figure 33-2] Figure 22A-33I is a schematic diagram of optical beams and beamlets propagating through a beam multiplier tube according to various embodiments.

[0098] [Figure 34] Figure 34 is a plan view of several embodiments of the primary waveguide apparatus shown in Figure 6.

[0099] [Figure 35] Figure 35 is a cross-sectional view of the primary waveguide apparatus of Figure 34 obtained along line 35-35.

[0100] [Figure 36] Figure 36 is a cross-sectional view of the primary waveguide apparatus of Figure 34 obtained along line 36-36.

[0101] [Figure 37] Figure 37 is a plan view of another embodiment of the primary waveguide apparatus shown in Figure 6.

[0102] [Figure 38] Figure 38 is a plan view of yet another embodiment of the primary waveguide apparatus shown in Figure 6.

[0103] [Figure 39] Figures 39A-39C are perspective views of the primary waveguide apparatus in Figure 34, and in particular show the emission of externally coupled light beamlets at different focal planes.

[0104] [Figure 40A] Figure 40A is a conceptual diagram of the relatively dense exit pupil of a waveguide device for a display screen.

[0105] [Figure 40B] Figure 40B is a conceptual diagram of a relatively dense exit pupil in a modified embodiment of the primary waveguide apparatus of Figure 34.

[0106] [Figure 41] Figure 41 is a plan view of several embodiments of the modified primary waveguide apparatus shown in Figure 40B.

[0107] [Figure 42] Figure 42 is a cross-sectional view of the primary waveguide apparatus of Figure 41 obtained along line 42-42.

[0108] [Figure 43] Figure 43 is a cross-sectional view of the primary waveguide apparatus of Figure 41 obtained along line 43-43.

[0109] [Figure 44] Figure 44 is a plan view of another embodiment of the modified primary waveguide apparatus shown in Figure 40B.

[0110] [Figure 45] Figure 45 is a cross-sectional view of a first modified example of the primary waveguide apparatus of Figure 44 obtained along line 45-45.

[0111] [Figure 46] Figure 46 is a cross-sectional view of a first modified example of the primary waveguide apparatus of Figure 44 obtained along line 46-46.

[0112] [Figure 47] Figures 47A-47D are profile diagrams illustrating the beam splitting techniques employed in the modified primary waveguide apparatus shown in Figure 45.

[0113] [Figure 48] Figure 48 is a cross-sectional view of a first modified example of the primary waveguide apparatus of Figure 44 obtained along line 48-48, and in particular shows the overlap of the optical beamlets.

[0114] [Figure 49] Figure 49 is a cross-sectional view of a first modified example of the primary waveguide apparatus of Figure 44 obtained along line 49-49, and in particular shows the overlap of the optical beamlets.

[0115] [Figure 50] Figure 50 is a cross-sectional view of a second modification of the primary waveguide device of FIG. 44 taken along line 50-50.

[0116] [Figure 51] Figure 51 is a cross-sectional view of a second modification of the primary waveguide device of FIG. 44 taken along line 51-51.

[0117] [Figure 52] Figure 52 is a cross-sectional view of a second modification of the primary waveguide device of FIG. 44 taken along line 52-52, and particularly shows the overlap of the light beamlets.

[0118] [Figure 53] Figure 53 is a cross-sectional view of a second modification of the primary waveguide device of FIG. 44 taken along line 53-53, and particularly shows the overlap of the light beamlets.

[0119] [Figure 54] Figure 54 is a cross-sectional view of a third modification of the primary waveguide device of FIG. 44 taken along line 54-54.

[0120] [Figure 55] Figure 55 is a cross-sectional view of a third modification of the primary waveguide device of FIG. 44 taken along line 55-55.

[0121] [Figure 56] Figure 56 is a cross-sectional view of a fourth modification of the primary waveguide device of FIG. 44 taken along line 56-56.

[0122] [Figure 57] Figure 57 is a cross-sectional view of a fourth modification of the primary waveguide device of FIG. 44 taken along line 57-57.

[0123] [Figure 58]FIG. 58 is a plan view of another embodiment of a display subsystem used in the virtual image generation system of FIG. 2.

[0124] [Figure 59A] FIGS. 59A and 59B are conceptual diagrams of a relatively dense exit pupil of a primary waveguide device of a display screen pre-expanded with a pre-pupil expander (PPE). [Figure 59B] FIGS. 59A and 59B are conceptual diagrams of a relatively dense exit pupil of a primary waveguide device of a display screen pre-expanded with a pre-pupil expander (PPE).

[0125] [Figure 60] FIG. 60 is a plan view of some embodiments of the PPE of FIGS. 59A and 59B used in combination with the primary waveguide device of FIG. 6.

[0126] [Figure 61] FIG. 61 is a cross-sectional view of the primary waveguide device and the PPE of FIG. 60 obtained along line 61-61.

[0127] [Figure 62] FIG. 62 is a cross-sectional view of the primary waveguide device and the PPE of FIG. 60 obtained along line 62-62.

[0128] [Figure 63] FIG. 63 is a conceptual diagram of pre-expansion and conventional expansion of an entrance pupil of a collimated light beam to an exit pupil using the PPE of FIG. 60.

[0129] [Figure 64] FIG. 64 is a plan view of another embodiment of the PPE of FIGS. 59A and 59B used in combination with the primary waveguide device of FIG. 34.

[0130] [Figure 65] FIG. 65 is a cross-sectional view of the primary waveguide device and the PPE of FIG. 64 obtained along line 65-65.

[0131] [Figure 66] Figure 66 is a cross-sectional view of the primary waveguide apparatus and PPE of Figure 64 obtained along line 66-66.

[0132] [Figure 67] Figures 67A and 67B are profile diagrams of different variations of the PPE shown in Figure 64.

[0133] [Figure 68] Figure 68 is a plan view of yet another embodiment of the PPE shown in Figures 59A and 59B, used in conjunction with the primary waveguide apparatus of Figure 34.

[0134] [Figure 69] Figure 69 is a cross-sectional view of the primary waveguide apparatus and PPE of Figure 68 obtained along line 69-69.

[0135] [Figure 70] Figure 70 is a cross-sectional view of the primary waveguide apparatus and PPE of Figure 68 obtained along line 70-70.

[0136] [Figure 71] Figure 71 is a perspective view of the PPE shown in Figure 68.

[0137] [Figure 72] Figure 72 is a cross-sectional view of a first modified example of the PPE of Figure 71 obtained along line 72-72.

[0138] [Figure 73] Figure 73 is a cross-sectional view of a first modified example of the PPE of Figure 71 obtained along line 73-73.

[0139] [Figure 74] Figure 74 is a cross-sectional view of a second modified example of the PPE of Figure 71 obtained along line 74-74.

[0140] [Figure 75]Figure 75 is a cross-sectional view of a second modified example of the PPE of Figure 71 obtained along line 75-75.

[0141] [Figure 76] Figure 76 is a plan view of yet another embodiment of the PPE shown in Figures 31A and 31B, used in conjunction with the primary waveguide apparatus of Figure 34.

[0142] [Figure 77] Figure 77 is a cross-sectional view of the primary waveguide apparatus and PPE of Figure 76 obtained along line 77-77.

[0143] [Figure 78] Figure 78 is a cross-sectional view of the primary waveguide apparatus and PPE of Figure 76 obtained along line 78-78.

[0144] [Figure 79] Figure 79 is a perspective view of the PPE shown in Figure 76.

[0145] [Figure 80] Figure 80 is a plan view of yet another embodiment of the PPE of Figures 59A and 59A used in conjunction with the primary waveguide apparatus of Figure 34.

[0146] [Figure 81] Figure 81 is a cross-sectional view of the primary waveguide apparatus and PPE of Figure 80 obtained along line 81-81.

[0147] [Figure 82] Figure 82 is a cross-sectional view of the primary waveguide apparatus and PPE of Figure 80 obtained along line 82-82.

[0148] [Figure 83] Figure 83 is an exploded perspective view of the PPE shown in Figure 80.

[0149] [Figure 84] Figure 84 is a perspective view of several embodiments of the planar waveguide assembly used in the PPE of Figure 83.

[0150] [Figure 85] Figures 85A and 85B are perspective views of the upper and lower planar orthogonal waveguide units used in the planar waveguide assembly of Figure 84.

[0151] [Figure 86] Figures 86A and 86B are cross-sectional views of the PPE shown in Figure 80.

[0152] [Figure 87A] Figures 87A-87C are plan views of the transfer functions of the upper and lower plane orthogonal waveguide units shown in Figures 85A and 85B. [Figure 87B] Figures 87A-87C are plan views of the transfer functions of the upper and lower plane orthogonal waveguide units shown in Figures 85A and 85B. [Figure 87C] Figures 87A-87C are plan views of the transfer functions of the upper and lower plane orthogonal waveguide units shown in Figures 85A and 85B.

[0153] [Figure 88] Figure 88 is a schematic diagram illustrating various generation of beam splitting performed by the upper planar waveguide assembly used in the PPE of Figure 80 to split an array of two-dimensional beamlets into multiple arrays of two-dimensional beamlets that accumulate to define a highly saturated exit pupil.

[0154] [Figure 89A] Figures 89A-89H are plan views illustrating the generation of multiple arrays of two-dimensional optical beamlets from a single array of two-dimensional optical beamlets using the PPE shown in Figure 80. [Figure 89B] Figures 89A-89H are plan views illustrating the generation of multiple arrays of two-dimensional optical beamlets from a single array of two-dimensional optical beamlets using the PPE shown in Figure 80. [Figure 89C]Figures 89A-89H are plan views illustrating the generation of multiple arrays of two-dimensional optical beamlets from a single array of two-dimensional optical beamlets using the PPE shown in Figure 80. [Figure 89D] Figures 89A-89H are plan views illustrating the generation of multiple arrays of two-dimensional optical beamlets from a single array of two-dimensional optical beamlets using the PPE shown in Figure 80. [Figure 89E] Figures 89A-89H are plan views illustrating the generation of multiple arrays of two-dimensional optical beamlets from a single array of two-dimensional optical beamlets using the PPE shown in Figure 80. [Figure 89F] Figures 89A-89H are plan views illustrating the generation of multiple arrays of two-dimensional optical beamlets from a single array of two-dimensional optical beamlets using the PPE shown in Figure 80. [Figure 89G] Figures 89A-89H are plan views illustrating the generation of multiple arrays of two-dimensional optical beamlets from a single array of two-dimensional optical beamlets using the PPE shown in Figure 80. [Figure 89H] Figures 89A-89H are plan views illustrating the generation of multiple arrays of two-dimensional optical beamlets from a single array of two-dimensional optical beamlets using the PPE shown in Figure 80.

[0155] [Figure 90A] Figures 90A-90D are plan views illustrating the correspondence between the four different beamlet groups in the beam patterns of Figures 89A and 89A and the four different initial beamlets in the single two-dimensional array of optical beamlets in Figure 89A. [Figure 90B] Figures 90A-90D are plan views illustrating the correspondence between the four different beamlet groups in the beam patterns of Figures 89A and 89A and the four different initial beamlets in the single two-dimensional array of optical beamlets in Figure 89A. [Figure 90C] Figures 90A-90D are plan views illustrating the correspondence between the four different beamlet groups in the beam patterns of Figures 89A and 89A and the four different initial beamlets in the single two-dimensional array of optical beamlets in Figure 89A. [Figure 90D] Figures 90A-90D are plan views illustrating the correspondence between the four different beamlet groups in the beam patterns of Figures 89A and 89A and the four different initial beamlets in the single two-dimensional array of optical beamlets in Figure 89A. [Modes for carrying out the invention]

[0156] The following description relates to display subsystems and methods to be used in augmented reality systems. However, while this disclosure is well suited to applications in augmented reality systems, it should be understood that, in its broadest aspects, it is not limited thereto and may be applied to any waveguide-based imaging system. For example, this disclosure can be applied to virtual reality systems. Therefore, although this specification is often described in the context of augmented reality systems, the disclosure should not be limited to such systems of use.

[0157] The various embodiments of this disclosure cover systems, methods, and articles for implementing optical systems, either in one or more embodiments. Other objects, features, and advantages of this disclosure are described in the embodiments, drawings, and claims for carrying out the invention.

[0158] Various embodiments will be described in detail here with reference to the drawings, which are provided as illustrative examples of the disclosure, so as to enable those skilled in the art to practice the disclosure. It should be noted that the drawings and the embodiments described below are not intended to limit the scope of the disclosure. Some elements of the disclosure may be implemented in part or in whole using known components (or methods or processes), and only those parts of such known components (or methods or processes) necessary for understanding the disclosure will be described, and detailed descriptions of other parts of such known components (or methods or processes) will be omitted so as not to obscure the disclosure. Furthermore, the various embodiments will include currently known and hereafter known equivalents of the components referenced herein as illustrations.

[0159] The optical system may be implemented independently of the AR / MR system, but many of the embodiments described below are explained in relation to the AR / MR system for illustrative purposes only.

[0160] Referring to Figure 2, several embodiments of the virtual image generation system 100 configured in accordance with this disclosure will be described here. The virtual image generation system 100 may operate as an augmented reality subsystem and provide an image of virtual objects mixed with physical objects within the field of view of an end user 50. There are two basic approaches to operating the virtual image generation system 100. The first approach employs one or more imaging devices (e.g., cameras) to capture an image of the surrounding environment. The virtual image generation system 100 mixes the virtual image into data representing the image of the surrounding environment. The second approach employs one or more at least partially transparent surfaces through which the surrounding environment is viewed, and on which the virtual image generation system 100 generates an image of virtual objects.

[0161] The virtual image generation system 100 and the various techniques taught herein may be employed in applications other than augmented reality and virtual reality subsystems. For example, the various techniques may be applied to any projection or display subsystem, or to a pico projector where movement can be performed by the end user's hands rather than the head. Thus, although much of the description herein is from the perspective of augmented reality subsystems or virtual reality subsystems, the teachings should not be limited to such subsystems of such uses.

[0162] For augmented reality applications at least, it may be desirable to spatially position various virtual objects relative to individual physical objects within the end user's field of view 50. Virtual objects are also referred herein as virtual tags, tags, or callouts, and may take a wide variety of forms, essentially any various data, information, concepts, or logical structures that can be represented as images. Non-limiting embodiments of virtual objects include virtual text objects, virtual numeric objects, virtual alphanumeric objects, virtual tag objects, virtual field objects, virtual chart objects, virtual map objects, virtual instrumentation objects, or virtual visual representations of physical objects.

[0163] The virtual image generation system 100 comprises a frame structure 102 worn by an end user 50, a display subsystem 104 supported by the frame structure 102 so as to be positioned in front of the end user 50's eye 52, and a speaker 106 supported by the frame structure 102 so as to be positioned adjacent to the end user 50's ear canal (optionally, another speaker (not shown) may be positioned adjacent to the end user 50's other ear canal to provide stereo / shapeable sound control). The display subsystem 104 is designed to present to the end user 50's eye 52 a light-based radiation pattern that is comfortably perceived as an extension of physical reality with a high level of image quality and three-dimensional perception, and which may be capable of presenting two-dimensional content. The display subsystem 104 presents a sequence of frames at high frequencies, providing the perception of a single coherent scene.

[0164] In the illustrated embodiment, the display subsystem 104 employs an “optical see-through” display through which the user can directly see light from real objects through transparent (or semi-transparent) elements. The transparent elements are often referred to as “couplers” and superimpose light from the display onto the real-world user’s field of view. To achieve this, the display subsystem 104 comprises a projection subsystem 108 and a partially transparent display screen 110 on which the projection subsystem 108 projects an image. The display screen 110 is positioned in the end user’s field of view between the end user’s eye 52 and the surrounding environment, such that direct light from the surrounding environment is transmitted through the display screen 110 to the end user’s eye 52.

[0165] In the illustrated embodiment, the image projection assembly 108 provides scanned light to a partially transparent display screen 110, thereby combining with direct light from the surrounding environment and transmitting it from the display screen 110 to the user's eye 52. In the illustrated embodiment, the projection subsystem 108 takes the form of an optical fiber scanning-based projection device, and the display screen 110 takes the form of a waveguide-based display into which scanned light from the projection subsystem 108 is fed, generating image layers representing stereoscopic 3D objects, for example, an image at a single optical viewing distance closer to infinity (e.g., arm length), images at multiple discrete optical viewing distances or focal planes, and / or stacked at multiple viewing distances or focal planes. These layers in the light field may be stacked close enough so that they appear consecutively together in the human visual subsystem (i.e., one layer is within the ragged signal cone region of the adjacent layer). In addition, or alternatively, the perceived continuity of transitions between layers in the light field may be increased even if the photographic elements are mixed across two or more layers and those layers are stacked more sparsely (i.e., one layer is outside the random signal cone region of the adjacent layer). The display subsystem 104 may be monocular or binocular.

[0166] The virtual image generation system 100 further includes one or more sensors (not shown) mounted on the frame structure 102 to detect the position and movement of the end user 50's head 54 and / or the position and interocular distance of the end user 50's eyes. Such sensors may include an image acquisition device (such as a camera), a microphone, an inertial measurement unit, an accelerometer, a compass, a GPS unit, a wireless device, and / or a gyroscope.

[0167] The virtual image generation system 100 further includes a user orientation detection module 112. The user orientation detection module 112 may detect the instantaneous position of the end user 50's head 54 and predict the position of the end user 50's head 54 based on position data received from sensors. Detection of the instantaneous position of the end user 50's head 54 facilitates the determination of the specific actual object that the end user 50 is looking at, thereby providing indication of a specific text message to be generated for that actual object, and further providing indication of the text area from which the text message should be streamed. The user orientation module 112 also tracks the end user 50's eyes 52 based on tracking data received from sensors.

[0168] The virtual image generation system 100 further includes a control subsystem, which can take any of a wide variety of forms. The control subsystem includes several controllers, for example, one or more microcontrollers, microprocessors or central processing units (CPUs), digital signal processors, graphics processing units (GPUs), other integrated circuit controllers, for example, application-specific integrated circuits (ASICs), programmable gate arrays (PGAs), for example, field PGAs (FPGAS), and / or programmable logic controllers (PLUs).

[0169] The control subsystem of the virtual image generation system 100 comprises a central processing unit (CPU), a graphics processing unit (GPU) 116, one or more frame buffers 118, and a 3D database 120 for storing 3D data. The CPU 114 controls the overall operation, while the GPU 116 renders frames from the 3D data stored in the 3D database 120 (i.e., converts 3D scenes into 2D images) and stores these frames in the frame buffer 116. Although not shown, one or more additional integrated circuits may control the loading of frames into and / or reading from the frame buffer 116, as well as the operation of the image projection assembly 108 of the display subsystem 104.

[0170] Various processing components of the virtual image generation system 100 may be physically contained within a distributed subsystem. For example, as shown in Figures 3A-3D, the virtual image generation system 100 includes a local processing and data module 130 that is operably coupled to the display subsystem 104 and sensors by wired connections or wireless connectivity 136, etc. The local processing and data module 130 may be mounted in various configurations, such as being fixedly attached to the frame structure 102 (Figure 3A), fixedly attached to a helmet or cap 56 (Figure 3B), embedded in headphones, detachably attached to the torso 58 of the end user 50 (Figure 3C), or detachably attached to the waist 60 of the end user 50 in a belt-mounted configuration (Figure 3D). The virtual image generation system 100 further includes a remote processing module 132 and a remote data repository 134, which are operably coupled to the local processing and data module 130 by wired connections or wireless connectivity 138, 140, etc., and these remote modules 132 and 134 are operably coupled to each other and become available as resources to the local processing and data module 130.

[0171] The local processing and data module 130 may include a power-efficient processor or controller and digital memory such as flash memory, both of which may be used to assist in the processing, caching, and storage of data acquired and / or processed using the remote processing module 132 and / or remote data repository 134 for passage to the display subsystem 104 after being captured from the sensor and / or processed or read. The remote processing module 132 may include one or more relatively powerful processors or controllers configured to analyze and process data and / or image information. The remote data repository 134 may include a relatively large digital data storage facility, which may be available through the internet or other networking configurations in a “cloud” resource configuration. In some embodiments, all data is stored and all calculations are performed in the local processing and data module 130, enabling fully autonomous use from any remote module.

[0172] The connections 136, 138, and 140 between the various components described above may include one or more wired interfaces or ports for providing wired or optical communication, or one or more wireless interfaces or ports via RF, microwave, and IR, etc., for providing wireless communication. In some implementations, all communication may be wired, while in other implementations, all communication may be wireless. In further implementations, the choice between wired and wireless communication may differ from that illustrated in Figures 3A-3D. Therefore, any particular choice between wired or wireless communication should not be considered limiting.

[0173] In the illustrated embodiment, the user-oriented module 112 is contained within the local processing and data module 130, while the CPU 114 and GPU 116 are contained within the remote processing module 132. In an alternative embodiment, the CPU 114, GPU 124, or a portion thereof, may be contained within the local processing and data module 130. The 3D database 120 can be associated with the remote data repository 134.

[0174] Before describing in detail the embodiments of the optically guided elements, this disclosure will hereby provide a brief description of an illustrative MR system.

[0175] One possible approach for implementing an MR system is to use multiple volume phase holograms, surface relief holograms, or optically stimulating optical elements that contain depth plane information to generate images that appear to originate from individual depth planes. In other words, a diffraction pattern or diffractive optical element ("DOE") may be embedded in or imprinted / embossed on an optically stimulating optical element ("LOE," e.g., a plane waveguide) such that the collimated light (a beam of light with a substantially plane wavefront) intersects with the diffraction pattern at multiple locations as it undergoes substantially total internal reflection along the LOE and emerges toward the user's eye. The DOE is configured such that light emanating from and through the LOE converges and appears to originate from a particular depth plane. The collimated light may be generated using an optical focusing lens ("focuser").

[0176] For example, a first LOE may be configured to deliver collimated light to the eye, appearing as if originating from the optical infinite depth plane (0 diopters). Another LOE may be configured to deliver collimated light, appearing as if originating from a distance of 2 meters (1 / 2 diopters). Yet another LOE may be configured to deliver collimated light, appearing as if originating from a distance of 1 meter (1 diopter). It can be understood that by using a stacked LOE assembly, multiple depth planes can be created, and each LOE is configured to display an image appearing as if originating from a particular depth plane. It should be understood that a stack may contain any number of LOEs. However, at least N stacked LOEs are required to generate N depth planes. Furthermore, N, 2N, or 3N stacked LOEs may be used to generate RGB color images on N depth planes.

[0177] To present 3-D virtual content to a user, a mixed reality (MR) system projects images of the virtual content into the user's eyes so that they appear to originate from various depth planes in the Z direction (i.e., orthogonal to the user's eyes). In other words, the virtual content can change not only in the X and Y directions (i.e., in a 2D plane orthogonal to the central visual axis of the user's eyes), but also in the Z direction so that the user may perceive the object as being at a very close distance, an infinite distance, or any distance in between. In other embodiments, the user may perceive multiple objects simultaneously in different depth planes. For example, the user may see a virtual dragon appearing from infinity and running towards them. Alternatively, the user may simultaneously see a virtual bird at a distance of 3 meters from them and a virtual coffee cup at arm's length (approximately 1 meter) from them.

[0178] A multi-plane focus system creates a variable depth perception by projecting an image onto some or all of multiple depth planes located at separate fixed distances in the Z direction from the user's eye. Referring here to Figure 9, it should be understood that a multi-plane focus system can display a frame on a fixed depth plane 502 (for example, six depth planes 502 as shown in Figure 9). While an MR system can include any number of depth planes 502, one exemplary multi-plane focus system has six fixed depth planes 502 in the Z direction. When generating virtual content on one or more of the six depth planes 502, 3-D perception is created so that the user perceives one or more virtual objects at a variable distance from the user's eye. Assuming that the human eye is more sensitive to objects that appear closer than objects that appear farther away, more depth planes 502 are generated closer to the eye, as shown in Figure 9. In other embodiments, the depth planes 502 may be placed equidistant from each other.

[0179] The depth plane position 502 may be measured in diopters, which is a unit of refractive power equal to the reciprocal of the focal length measured in meters. For example, in some embodiments, depth plane 1 may be 1 / 3 diopter 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 understood that in other embodiments, depth plane 502 may be generated at other distances / diopters. Thus, when virtual content is generated in a strategically placed depth plane 502, the user can perceive the virtual objects in three dimensions. For example, the user may perceive a first virtual object as being close when it is displayed in depth plane 1, while another virtual object appears at infinity in depth plane 6. Alternatively, the virtual object may first appear on depth plane 6, and then on depth plane 5, etc., until the virtual object appears very close to the user. It should be understood that the above embodiment is significantly simplified for illustrative purposes. In another embodiment, all six depth planes may be concentrated on specific focal distances away from the user. For example, if the virtual content to be displayed is a coffee cup 0.5 meters away from the user, all six depth planes may be generated on various cross-sections of the coffee cup, giving the user a highly granular 3-D view of the coffee cup.

[0180] In some embodiments, the AR system may function as a multi-plane focal system. In other words, all six LOEs may be rapidly and continuously generated, producing images that appear to originate from six fixed depth planes, and the light source may be simultaneously illuminated so as to rapidly transmit image information to LOE1, then LOE2, then LOE3, and so on. For example, a portion of a desired image, including an image of the sky at optical infinity, may be input at time 1, and LOE1090 (e.g., depth plane 6 from Figure 9), which reserves light collimation, may be used. Then, an image of a closer tree branch may be input at time 2, and LOE1090 may be used, configured to produce an image that appears to originate from a depth plane 10 meters away (e.g., depth plane 5 from Figure 9). Then, an image of a pen may be input at time 3, and LOE1090 may be used, configured to produce an image that appears to originate from a depth plane 1 meter away. This type of paradigm can be repeated in a high-speed time-series manner (e.g., 360Hz) so that the user's eyes and brain (e.g., the visual cortex) perceive all inputs as part of the same image.

[0181] AR systems are required to project images (i.e., by diverging or converging a light beam) that appear to emerge from various locations along the Z-axis (i.e., the depth plane) and generate images for 3-D experiences / scenarios. As used in this application, the light beam includes, but is not limited to, directional projection of light energy (including visible and invisible light energy) emitted from a light source. Generating images that appear to emerge from various depth planes is in accordance with the convergence-divergence and accommodation of the user's eyes for that image, minimizing or eliminating convergence-divergence-accommodation collisions.

[0182] Figure 4 depicts a basic optical system 400 for projecting an image onto a single depth plane. The system 400 includes a light source 420 and an associated diffractive optical element (not shown) and an internally coupled grating 492 (ICG) of LOE 490. The diffractive optical element may be of any type, including volume or surface relief. In some embodiments, the ICG 492 is a reflective-mode aluminum-coated portion of the LOE 490. In other embodiments, the ICG 492 is a transmissive-diffractive portion of the LOE 490. When the system 400 is in use, a light beam from the light source 420 enters the LOE 490 through the ICG 492 for display to the user's eye and propagates along the LOE 490 by substantially total internal reflection ("TIR"). While only one beam is illustrated in Figure 4, it should be understood that multiple beams may enter the LOE 490 from a wide range of angles through the same ICG 492. A light beam “incident” or “captured” into the LOE includes, but is not limited to, a light beam that interacts with the LOE to propagate along the LOE by substantial TIR. The system 400 depicted in Figure 4 may include various light sources 420 (e.g., LEDs, OLEDs, lasers, and masked large-area / broadband emitters). In other embodiments, light from the light source 420 may be delivered to the LOE 490 via an optical fiber cable (not shown).

[0183] Referring here to Figure 5, the image projection assembly 108 includes one or more light sources 150 that generate light (e.g., emit light of different colors in a defined pattern). The light sources 150 may take any of a wide variety of forms, for example, a set of RGB lasers (e.g., laser diodes capable of outputting red, green, and blue light) each capable of generating coherent collimated red, green, and blue light according to a defined pixel pattern defined within individual frames of pixel information or data. Laser light provides high color saturation and is highly energy efficient.

[0184] The image projection assembly 108 further includes a scanning device 152 that scans light in a predetermined scanning pattern in response to a control signal. The scanning device 152 comprises one or more optical fibers 154 (e.g., single-mode optical fibers), each having a proximal end 154a in which light is received from a light source 150, and a distal end 154b from which light is supplied to the display screen 110. The scanning device 152 further includes a mechanical drive assembly 156 on which the optical fibers 154 are mounted. The drive assembly 156 is configured to displace the distal end 154b of each optical fiber 154 about a pivot point 158 ​​according to the scanning pattern.

[0185] To achieve this objective, the drive assembly 156 comprises a piezoelectric element 160 on which an optical fiber 154 is mounted, and the drive electronics 162 is configured to transmit an electrical signal to the piezoelectric element 160, thereby causing the distal end 154b of the optical fiber 154 to vibrate according to a scanning pattern. Thus, the operation of the light source 150 and the drive electronics 162 are coordinated in such a manner that they generate image data encoded in a spatially and / or temporally variable form of light. A description of the optical fiber scanning technique is provided in U.S. Patent No. 2015 / 0309264 (expressly incorporated herein by reference).

[0186] The projection assembly 108 further comprises an optical coupling assembly 164 that couples light from the scanning device 152 into the display screen 110. The optical coupling assembly 164 comprises a collimating element 166 that collimates the light emitted by the scanning device 152 into the collimated light beam 250. The collimating element 166 is illustrated in Figure 5 as being physically separated from the optical fiber 154, but the collimating element may be physically mounted on the distal end 154b of each optical fiber 154 in a “microlens” array, as described in U.S. Patent Application No. 15 / 286,215, “Microlens Collimator for Scanning Optical Fiberin Virtual / Augmented Reality System” (expressly incorporated herein by reference). The optical coupling subsystem 164 further comprises internal coupling (IC) elements 168, such as one or more reflective surfaces, diffraction gratings, mirrors, dichroic mirrors, or prisms, which optically couple light into the edges of the display screen 110 at an angle that ensures the light propagates within the display screen 110 in a desired direction.

[0187] As will be described in more detail below, the optical coupling subsystem 164 optically couples the collimated light beam 250 into the display screen 110, which will expand the pupil size of the collimated light beam 250 to be proportional to the entrance pupil size of the end user 50. In the embodiments described below, the display screen 110 employs a technique known as “beam doubling,” which refers to an exit pupil expansion method specifically designed to expand the small-diameter entrance pupil (e.g., about 50 microns to 1 mm) of each collimated light beam 250 from the image projection assembly 108 by doubling the individual light beams 250 into multiple light beamlets, resulting in a light beamlet array exit pupil that virtually matches the entrance pupils (e.g., about 5 mm to 7 mm) of one or both eyes of the user over a fixed pupil distance. It should be noted that while the “beam doubling” technique is described herein as being performed on the display screen 110, such “beam doubling” techniques can be applied anywhere within the image generation system 100, including any similar substrate system / subsystem upstream of the display screen 110.

[0188] The extent to which the collimated light beam 250 needs to be doubled to achieve a given filling rate will depend on the original pupil size of the collimated light beam 250. For example, if the original pupil size of the collimated light beam 250 output by the image projection assembly 108 is 500 microns, such a pupil size may need to be doubled tenfold to achieve the desired filling rate, while if the original pupil size of the collimated light beam output by the image projection assembly 108 is 50 microns, such a pupil may need to be doubled a hundredfold to achieve the desired filling rate.

[0189] Preferably, the light beamlet array exit pupil of the display screen is completely filled or saturated with light beamlets to maximize wavefront density and minimize depth of field. If the light beamlets in the exit pupil are too densely packed, the wavefront density and depth of field of the display screen will be impaired, and if the diameter of the light beamlets is too small, the angular resolution of the display screen will be impaired.

[0190] Theoretically, the thickness of the display screen 110 can be reduced to increase the number of light beamlets created from a single collimated light beam 250 input into the display screen 110, thereby increasing the internal filling of the exit pupil with light beamlets. However, due to durability and manufacturing limitations, the extent to which the display screen 110 can be thinned is limited, thereby limiting the internal filling of the exit pupil. Also, the entrance pupil of the collimated light beam 250 transmitted from the image projection assembly 108 into the display screen 110 can theoretically be increased to increase the internal filling of the exit pupil with light beamlets, but this would require a proportional increase in the size of the image projection assembly 108, thereby negatively impacting the wearability of the VR / AR system. Importantly, the embodiments described below increase the internal filling of the exit pupil without requiring an increase in the size of the image projection assembly 108.

[0191] To achieve this objective, the display screen 110 acts as a pupil expander (PE) that expands the effective entrance pupil of the collimated light beam 250 (carrying image information) for display to one eye 52 (monocular) or both eyes 52 (binocular) of the end user 50. The display screen 110 takes the form of a waveguide apparatus 170, which includes a planar optical waveguide 172 and one or more diffractive optical elements (DOEs) 174 that are optically coupled within the planar optical waveguide 172 and associated with the planar optical waveguide 172 to expand the effective entrance pupil of the collimated light beam 250 in two dimensions. In an alternative embodiment, the waveguide apparatus 170 may comprise a plurality of planar optical waveguides 172 and DOEs 174, each associated with a planar optical waveguide 172.

[0192] As best illustrated in Figure 6, the plane optical waveguide 172 has a first end 176a and a second end 176b, the second end 176b facing the first end 176a along the length 178 of the plane optical waveguide 172. The plane optical waveguide 172 has a first surface 180a and a second surface 180b, and at least the first and second surfaces 180a, 180b (collectively, 180) form an internal reflective optical path (illustrated by solid arrows 182a and dashed arrows 182b, collectively, 182) at least partially along at least a portion of the length 178 of the plane optical waveguide 172. The plane optical waveguide 172 may take various forms that provide substantially total internal reflection (TIR) ​​for light to strike the surface 180 below a defined critical angle.

[0193] DOE174 (illustrated by double dashed lines in Figures 5 and 6) may take a variety of forms, interrupting the TIR optical path 182 and extending along at least a portion of the length 178 of the plane optical waveguide 172, providing multiple optical paths (illustrated by solid arrows 184a and dashed arrows 184b, collectively, 184) between the interior 185a and exterior 185b of the plane optical waveguide 172. As will be described in more detail below, light propagates through the plane optical waveguide 172 along the internal reflective optical path and intersects with DOE174 for splitting the light into optical beamlets, which at various locations are either diffracted along different internal reflective optical paths or diffracted outward from the plane 180b of the plane optical waveguide 172.

[0194] In the illustrated embodiment, DOE174 can be characterized as an optical component comprising one or more diffraction gratings, each with a periodic structure such as a wavelength of light, which splits and diffracts light into several beams traveling in different directions. The diffraction gratings can consist of, for example, surface nano-ridges, nano-patterns, gaps, etc., which can be photolithograph printed onto a substrate. DOE174 can provide apparent object positioning and a focal plane for the apparent object. This may be achieved frame by frame, subframe by subframe, or even pixel by pixel.

[0195] As illustrated in Figure 6, light propagates along the planar optical waveguide 172, accompanied by at least some reflections or "bounces" resulting from TIR propagation. Note that some implementations may employ one or more reflectors in the internal optical path, such as thin films, dielectric coatings, or metallic coatings, which may facilitate reflection. The light propagates along the length 178 of the planar optical waveguide 172 and intersects with the DOE 174 at various positions along the length 178. The DOE 174 may be incorporated within the planar optical waveguide 172 or may be in contact with or adjacent to one or more of the surfaces 180 of the planar optical waveguide 172. The DOE 174 performs at least two functions. The DOE 174 shifts the angle of the light, diverting some of the light from the TIR and causing it to emerge from the interior 185a, through the surface 180 of the planar optical waveguide 172, onto the exterior 185b surface. The DOE 174 focuses the externally coupled light to the viewing distance. Therefore, when viewed through the surface 180 of the plane optical waveguide 172, a digital image is visible at one or more viewing distances.

[0196] A collimated light beam 250, incident on waveguide 172 at one of two different angles, will follow one of two TIR optical paths 182a, 182b and produce a light beamlet 256 that exits planar optical waveguide 172 along one of two sets of external optical paths 185a, 185b. That is, a collimated light beam 250a, incident on waveguide 172 at the angle represented by TIR optical path 182a, will produce a light beamlet 256a that exits planar optical waveguide 172 along the set of external optical paths 185a, and a collimated light beam 250b, incident on waveguide 172 at the angle represented by TIR optical path 182b, will produce a light beamlet 256b that exits planar optical waveguide 172 along the set of external optical paths 185b.

[0197] From the foregoing, it can be understood that the display subsystem 104 generates a composite image frame of pixel information that presents an image of one or more virtual objects to the user. Further details describing the display subsystem are provided in U.S. Patent Application No. 14 / 212,961, entitled "Display Subsystem and Method," and U.S. Patent Application No. 14 / 696,347, entitled "Planar Optical Waveguide Apparatus With Diffraction Elements(s) and Subsystem Employing Same" (expressly incorporated herein by reference).

[0198] As described above, Figure 4 depicts a basic optical system 400 for projecting an image onto a single depth plane. Figure 7 depicts another optical system 400', which includes a light source 420, three LOEs 490, and three separate internally coupled gratings 492. Optical system 400' also includes three beam splitters or dichroic mirrors 462 (for directing light to the individual LOEs) and three LC shutters 464 (for controlling when the LOEs are illuminated). When system 400' is in use, the light beam from the light source 420 is split into three sub-beams / beamlets by the three beam splitters 462. The three beam splitters also redirect the beamlets toward the individual internally coupled gratings 492. After the beamlets enter the LOE490 through individual internally coupled gratings 492, they propagate along the LOE490 by substantial TIR, where they interact with additional optical structures that result in display to the user's eye. The surface of the internally coupled gratings 492 on the far side of the optical path can be coated with an opaque material (e.g., aluminum) to prevent light from passing through the internally coupled grating 492 to the next LOE490. In some embodiments, a beam splitter 462 can be combined with a wavelength filter to generate red, green, and blue beamlets. In such embodiments, three LOE490 are required to display a color image in a single depth plane. In another embodiment, each LOE490 may present a portion of a larger single depth plane image area that is laterally displaced angularly within the user's field of view, either of similar or different colors ("tiled field of view").

[0199] Figure 8 depicts yet another optical system 400'' having six beam splitters 462, six LC shutters 464, and six LOE490s, each having an individual ICG492. As mentioned in the discussion of Figure 7, three LOE490s are required to display a color image in a single depth plane. Therefore, the six LOE490s of this system 400'' can display a color image in two depth planes.

[0200] Figure 10 depicts the LOE490, which has an ICG492, a cross pupil expander 494 ("OPE"), and an exit pupil expander 496 ("EPE").

[0201] As shown in Figure 4-9, as the number of depth planes, field tiles, or colors generated increases (e.g., with increased MR scenario quality), the number of LOE490s and ICG492s also increases. For example, a single RGB color depth plane requires at least three LOE490s, accompanied by three ICG492s. Consequently, any image defects (e.g., blurring from a limited beam diameter) are also amplified, with an additional opportunity to degrade MR scenario quality. Thus, increasing the number of optical elements required to produce an acceptable MR scenario exacerbates image quality problems.

[0202] The LOE490 discussed above also functions as an exit pupil expander 496 ("EPE"), which increases the numerical aperture of the light source 420, thereby increasing the resolution of the system 400. Because the light source 420 produces small diameter / spot-sized light, the EPE496 expands the apparent pupil size of the light emitted from the LOE490, thereby increasing the system resolution. In other embodiments of the MR system 400, the system may further include, in addition to the EPE496, an orthogonal pupil expander 494 ("OPE") to expand the light in both the X and Y directions. Further details of the EPE496 and OPE494 are described in U.S. Utility Patent Application No. 14 / 555,585 and U.S. Utility Patent Application No. 14 / 726,424, whose contents are incorporated above by reference.

[0203] Figure 10 depicts LOE490 having ICG492, OPE494, and EPE496. Figure 10 depicts LOE490 from an overhead view, similar to the view from the user's eye. ICG492, OPE494, and EPE496 may be any type of DOE, including volume or surface relief.

[0204] ICG492 is a DOE (e.g., a linear grid) configured to capture light from light source 420 for TIR propagation. In the embodiment depicted in Figure 10, light source 420 is positioned on the side of LOE490.

[0205] OPE494 is a DOE (e.g., a linear grid) that is tilted in the lateral plane (i.e., perpendicular to the optical path) such that the light beam propagating through the system 400 will be deflected 90 degrees to the side. OPE494 is also partially transparent and partially reflective along the optical path so that the light beam partially passes through OPE494 and forms multiple (e.g., 11) beamlets. In some embodiments, the optical path is along the X-axis, and OPE494 is configured to bend the beamlets with respect to the Y-axis.

[0206] EPE496 is a DOE (e.g., a linear grid) that is tilted in the axial plane (i.e., parallel to the optical path or in the Y direction) so that beamlets propagating through System 400 will be deflected in the 90-degree axial direction. EPE496 is also partially transmissive and partially reflective along the optical path (Y-axis) so that beamlets partially pass through EPE496 and form multiple (e.g., seven) beamlets. EPE496 is also tilted in the Z direction to direct a portion of the propagating beamlets toward the user's eye.

[0207] Both OPE494 and EPE496 are also at least partially transparent along the Z-axis, allowing real-world light (e.g., reflected from real-world objects) to pass through OPE494 and EPE496 in the Z-direction and reach the user's eyes. In some embodiments, ICG492 is also at least partially transparent along the Z-axis to capture real-world light.

[0208] Figure 11A shows a first light beam 610 that enters the eye 600 and is focused by the lens 602 to a small spot 612 on the retina 604. Preferably, the small spot 612 is approximately the size of a photoreceptor on the retina 604. The first image or first portion of the image corresponding to the first light beam 610 is in focus, as shown by the energy distribution curve 614 corresponding to the first light beam 610 in the graph in Figure 11B. Figure 11A also depicts a second light beam 620 that enters the eye 600 and is focused by the lens 602 to a larger spot 622 on the retina 604. The second image or second portion of the image corresponding to the second light beam 620 (with the larger spot 622) is not in focus (e.g., out of focus), as shown by the energy distribution curve 624 corresponding to the second light beam 620 in the graph in Figure 11B. Figure 11B illustrates the energy distribution patterns of two real-world light beams that are focused onto the retina by the lens.

[0209] Figure 12A shows an eye 700 with a lens 702, which is accommodated so that a second light beam 720 is focused onto a small spot 722 on the retina 704. As a result, the second image or second portion of the image corresponding to the second light beam 710 is in focus, as shown by the energy distribution curve 724 corresponding to the second light beam 720 in the graph in Figure 12B. However, in Figure 12A, the first light beam 710 is focused onto a larger spot 712 on the retina 704, resulting in a larger spot 712 on the retina 704. The first image or first portion of the image corresponding to the first light beam 710 (with the larger spot 712) is not in focus (e.g., out of focus), as shown by the energy distribution curve 714 corresponding to the first light beam 710 in the graph in Figure 12B. Figure 12B depicts the energy distribution patterns of two real-world light beams focused onto the retina by the lens.

[0210] The size of the beam spot on the retina affects the image resolution as follows: The function of the eye is to collect light information related to a "3-D" scene consisting of multiple point sources of light (e.g., emitted or reflected). For example, a tree may contain millions of point sources of light that reflect light from the sun. The eye (e.g., the lens within it) bends the light beam into a spot on the retina. Ideally, the beam spot on the retina is the size of the photoreceptor. When the eye is well focused on an object, the eye will focus the light beam from the object into the smallest possible spot on the retina. When the eye is out of focus on an object, the light beam is focused in front of or behind the retina, and the spot becomes closer to a circle rather than a point. A wider circular spot may hit several photoreceptors on the retina, resulting in a blurred image when interpreted by the viewer's occipital cortex. Furthermore, a smaller beam spot (e.g., a 2-3 mm diameter beam) will change the spot size (i.e., blur or focus) more rapidly with lens accommodation. On the other hand, a larger beam spot (e.g., a 0.5 mm diameter beam) would not change the spot size (i.e., blur or focus) with lens focusing.

[0211] Figure 13A shows an eye 800 with a lens 802, which is accommodated so that the first and second light beams 810, 820 are focused onto separate, larger spots 812, 822 on the retina 804. As a result, the first and second images, or the first and second portions of one or more images, corresponding to the first and second light beams 810, 820, are less in focus (e.g., out of focus) compared to the in-focus image, as shown by the energy distribution curves 814, 824 corresponding to the first and second light beams 810, 820 in the graph in Figure 13B. Figure 13B depicts the energy distribution patterns of two real-world light beams focused onto the retina by the lens. As shown in Figures 11A-13B, the anatomical structure of a single lens makes it difficult to focus two light beams with different angles of incidence in parallel. When one beam is in focus, the other beam will be out of focus. As shown in Figures 13A and 13B, attempts to adjust the lens to the intermediate focal point of two light beams may result in two out-of-focus images or parts of one or more images. As a result of anatomical limitations, if a single lens focuses on a portion of a light beam or field of view ("FOV"), the other light beam or portion of the FOV will be out of focus.

[0212] As the image focal limit increases, various other optical, anatomical, and technical limitations arise. Image resolution is a function of beam diameter and beam angle ("optical invariants"), which are tied to the number of resolvable spots (e.g., in the laser scanner industry). The optical invariants are related to the numerical aperture focused by the pixels, which is multiplied by the number of pixels. A larger optical beam diameter results in higher image resolution. A smaller optical beam diameter results in the ability to conserve an increasing optical beam angle and maximize the field of view (FOV). These optical limitations make beam diameter optimization difficult, as beam diameter affects both image resolution and optical beam angle, resulting in a trade-off between image quality and FOV size.

[0213] Figures 14A-14B demonstrate the relationship between light beam diameter and image resolution. As shown in Figure 14A, a light beam 910 with a maximum beam diameter 916 (e.g., sufficient to fill the entire pupil of eye 900, or about 2-3 mm) produces a minimum spot size 912 for a given eye 900. The small spot size 912 results in a corresponding in-focus image or a portion thereof, as shown in the energy distribution curve 914 in Figure 14B. Figure 14B depicts the energy distribution pattern of a real-world light beam as it is focused onto the retina by the lens. The larger diameter of the light beam 910 allows eye 900 to focus the light beam 900 by changing the shape of the lens 902. The ability to focus a maximum-size light beam results in increased image resolution. However, a light beam 1010 with a smaller beam diameter 1016 (e.g., about 0.5 mm) produces a larger spot size 1012, as shown in Figure 15A. The larger spot size 1012 results in a correspondingly defocused image or a portion thereof, as shown in the energy distribution curve 1014 in Figure 15B. Figure 15B depicts the energy distribution pattern of a real-world light beam as it is focused onto the retina by the lens.

[0214] Furthermore, if the light beam diameter is approximately 0.5 mm, some eyes will exhibit open-loop accommodation, resulting in all objects appearing at the same level of poor focus. As in a pinhole camera, the entire field of view will be equally and poorly focused, as shown in Figures 15A and 15B, because the retinal space is too small to resolve larger spots displayed on it. Additionally, if the light beam diameter is approximately 0.5 mm, the pupil will be fully dilated, potentially leading to optical aberrations such as a halo around the point source of light.

[0215] As described above, various other optical, anatomical, and technical limitations result in performance limitations for head-mounted displays. For example, a light beam with a smaller diameter (e.g., about 0.5 mm) will result in lower image resolution and optical aberrations compared to a light beam with a larger diameter (e.g., about 2-3 mm). On the other hand, a light beam with a larger diameter (e.g., about 2-3 mm) will result in a narrower field of view (FOV) compared to a light beam with a smaller diameter (e.g., about 0.5 mm). The balance between image resolution and FOV results in suboptimal image resolution and FOV.

[0216] The following disclosure describes various embodiments of systems and methods for simulating a larger diameter light beam using multiple (e.g., arrays) smaller diameter light beams. These beam doubling systems and methods generate a bundle of interconnected, interacting, and cloned beamlets 1116 that pass through the pupil and collide with the retina 1104, as shown in Figure 16A. Combinations of beam arrays, relative spacing, and beam diameters can generate a concentrated energy image on the retina 1104 (see Figure 16B). Figure 16B depicts the energy distribution pattern of a real-world array of light beams, including the optical interactions of the light beams, as they are focused onto the retina 1104 by the lens 1102. Through interference and other optical properties of the beam array (e.g., coherence, phase uniformity, etc.), the light energy (e.g., irradiance, peak intensity, etc.) is concentrated in the center of the graph, as shown by the energy distribution curve 1114 corresponding to the beamlet 1116 in the graph in Figure 16B, by eliminating energy in the side lobes (constant power). This focused light energy, in turn, produces a more focused image with higher image resolution. For example, the coherence and phase uniformity across the beamlet 1116 may correspond to an energy distribution with relatively high peak values ​​and attenuated side lobes, and thus may play a role in producing a relatively focused and visually sharp image. In fact, an array of cloned smaller diameter beamlets 1116 generates smaller spots 1112 on the retina 1104, with a sharp point spreading function 1114 that approximates the sharp point spreading function 914 (see Figures 14A and 14B) produced by the larger diameter beam 910. The array of smaller diameter beamlets 1116 allows the system to overcome beam diameter limitations (resulting from diffraction and / or device size limitations). At the same time, the use of a system with smaller diameter light beams results in a wider field of view (FOV).

[0217] Multiple / array beamlets (each with a smaller diameter) simulate the light energy from a much larger diameter light beam, increasing image resolution while maintaining a wider field of view (FOV) based on the smaller beam diameter.

[0218] Figure 17A schematically depicts an LOE490 that generates an array of beamlets 1216 from a single incident light beam 1210 (see beam multiplier tube described below). A portion of the beamlets 1216 passing through the pupil 1206 formed by the iris 1208 is focused by the lens 1202. Figure 17A depicts multiple beamlets 1216, but does not illustrate a two-dimensional beamlet array according to some embodiments. Figure 17B schematically depicts a selected beamlet 1206 from the beamlet array passing through the pupil 1206 formed by the iris 1208.

[0219] The spacing of the beamlet spots can also affect image quality. As shown in Figure 18A, the beamlet spots 1316 on the retina may overlap, with each beamlet spot 1316 covering more than one photoreceptor. When coherent and in phase, the distribution pattern of beamlet spots 1316 depicted in Figure 18A can result in a focused, sharp image. However, when each beamlet spot 1316 collides on more than one photoreceptor, or when there is a phase difference between multiple beamlet spots colliding on a single photoreceptor, the resulting image may appear less sharp. Figures 18B and 18C depict other beamlet spot 1316 distribution patterns on the retina, where each beamlet spot 1316 may cover approximately one photoreceptor. Generally, these distribution patterns are less affected by coherence and phase uniformity than those in Figure 18A, and can therefore result in a very focused, sharp image. Therefore, beam array architecture, relative beam / beamlet spacing, and beam / beamlet diameter are factors that can affect the resolution / sharpness of images in the retina.

[0220] Figure 19 depicts a beam multiplier tube 1430 (i.e., a thin beam multiplier tube), which may be an optically guided optical element such as OPE494 and / or EPE496 of LOE490 (see Figure 67). The input beam 1410 is incident on the beam multiplier tube 1430 (e.g., via an ICG or other incident portion) and propagates along the beam multiplier tube 1430 via substantial TIR. As the input beam 1410 propagates along the beam multiplier tube 1430, each time the input beam 1410 interacts with the external coupling grating ("OCG") 1498, a portion of the input beam 1410 exits the beam multiplier tube 1430 via the OCG 1498. The OCG 1498 is configured to allow a portion of the optical beam to exit the beam multiplier tube 1430 while another portion of the optical beam propagates along the beam multiplier tube 1430 via substantial TIR. OCG1498 may be any type of diffractive optical element, including volume or surface relief. The beam multiplier tube 1430 clones a single input beam 1410 into three output beamlets 1416, each encoding the same pixel information as the input beam 1410.

[0221] The beam multiplier tube 1430 is depicted in a side view in Figure 19, but the beam multiplier tube 1430 may have a length and width similar to OPE494 and / or EPE496 shown in Figure 67. Furthermore, the input beam 1410 is generally depicted to propagate from left to right, but the beam multiplier tube 1430 may be configured to direct the optical beam in various patterns, including, but not limited to, a zigzag pattern, which generates an array of beamlets 1416 (see, for example, Figure 18B).

[0222] As shown in Figure 20, only a portion (i.e., one) of the beamlets 1516 emitted from the beam multiplier tube 1530 passes through the pupil 1506 defined by the iris 1508 and is focused by the lens 1502. Therefore, even with beam multiplication, the spacing of the beamlets 1516 can affect the actual number of beams perceived by the user. Figure 20 also shows that the number of bounces of the input beam 1510 per length of the beam multiplier tube 1530 determines the number of beamlets 1516 emitted from a given length of the beam multiplier tube 1530.

[0223] Figure 21 depicts thinner beam multiplier tubes 1630' according to several embodiments. A thicker beam multiplier tube 1630 is also depicted for comparison. Over nearly the same length, each input optical beam 1610 (incident angle is preserved between the two multiplier tubes) bounces more times in the thinner beam multiplier tube 1630' compared to the thicker beam multiplier tube 1630. The input optical beam 1610 bounces back and forth at a higher spatial frequency because the distance it traverses before encountering each surface of the thinner beam multiplier tube 1630' is shorter. Therefore, a higher density of beamlets emerges from the thinner beam multiplier tube 1630' compared to the thicker beam multiplier tube 1630. For example, each input optical beam 1610 bounces 13 times in a thinner beam multiplier tube 1630', while a similar input optical beam 1610 bounces only 3 times in a thicker beam multiplier tube 1630. The thinner beam multiplier tube 1630' provides more beam doubling (i.e., cloning) per unit length of the beam multiplier tube compared to the thicker beam multiplier tube 1630. Furthermore, when this linear increase in cloning efficiency is doubled over two dimensions (e.g., length and width), the increase in cloning efficiency from the reduced beam multiplier tube thickness becomes exponential. The individual spacings between doubled beamlets in two dimensions are not necessarily identical (although symmetry is preferred). Moreover, the thinner beam multiplier tube 1630' can reduce overlap through coherent interactions despite the increased beam.

[0224] The beam multiplier tube depicted in Figures 19-21 includes two opposing reflective surfaces that reflect light in substantially opposite directions, thereby enabling substantial TIR. In other embodiments, the beam multiplier tube includes more than two reflective surfaces. For example, the multi-surface beam multiplier tube 1730 depicted in Figure 22A includes first and second optically guided sub-elements ("LOS") 1730A and 1730B. The first LOS 1730A is similar to the beam multiplier tube 1530 depicted in Figure 20 in that it has two (i.e., first and second) opposing reflective surfaces 1732 and 1734. The second LOS 1730B depicted in Figure 22A has a third reflective surface 1736 that reflects light in substantially the same direction as the second reflective surface 1734 in the first LOS 1730A.

[0225] The second LOS 1730B is positioned across the first LOS 1730A such that the incident light beam 1710 passes through the first LOS 1730A at least partially and enters the second LOS 1730B. As the incident light beam 1710 passes through the first LOS 1730A, a portion of it is partially reflected by the second reflective surface 1734. The portion of the incident light beam 1710 passing through the second LOS 1730B is reflected by the third reflective surface 1736 in substantially the same direction as the portion of the incident light beam 1710 reflected by the second reflective surface 1734. The addition of the second LOS 1730B and its third reflective surface 1736 results in a doubling of the number of beamlets 1716 propagating along the first and second LOS 1730A, 1730B by substantially TIR.

[0226] The thickness of the second LOS 1730B depicted in Figure 22A is such that a portion of the beamlets 1716 reflected from the third reflective surface 1736 substantially overlaps with the beamlets 1716 reflected from the second reflective surface 1734. Given the situation where portions of the beamlets 1716 are out of phase with each other, such overlap can amplify the effects of destructive interference between phase-mismatched beamlets. In addition, high levels of overlap can minimize the degree of doubling in the number of beamlets 1716. For example, a first bounce from the second and third reflective surfaces 1734, 1736 doubles the number of beams 1710 / beamlets 1716 from 1 to 2, while a second bounce only doubles the number of beamlets 1716 from 2 to 3. The extent to which at least a portion of the beamlets 1716 overlap can be controlled by adjusting the input beam 1710 diameter and / or input beam 1710 separation, both of which are substantially preserved during substantial TIR. For example, the distance between the edges of two adjacent beamlets from among the number of beamlets 1716 can be increased by reducing the diameter of the input beam 1710.

[0227] The beam doubling tube 1730 depicted in Figure 22B includes first and second LOS 1730A, 1730B, similar to the beam doubling tube 1730 depicted in Figure 22A. However, the thickness of the second LOS 1730B is adjusted / selected so that the beamlets 1716 reflected from the third reflective surface 1736 do not overlap with the beamlets 1716 reflected from the second reflective surface 1734. As a result, the beam doubling tube 1730 depicted in Figure 22B has a higher degree of beamlet doubling than the beam doubling tube 1730 depicted in Figure 22A. For example, the first bounce from the second and third reflective surfaces 1734, 1736 doubles the number of beams 1710 / beamlets 1716 from 1 to 2, while the second bounce doubles the number of beamlets 1716 from 2 to 4. Continuing this pattern, each bounce from the second and third reflective surfaces 1734 and 1736 will substantially double the number of beamlets 1716 in exponential growth.

[0228] The beam multiplier tube 1830 depicted in Figure 23 includes first and second LOS 1830A and 1830B, similar to the beam multiplier tube 1730 depicted in Figure 22A. The difference between beam multiplier tubes 1730 and 1830 is that the second LOS 1830B depicted in Figure 23 has a fourth reflective surface 1838 in addition to a third reflective surface 1836. The third and fourth reflective surfaces 1836 and 1838 are located on the opposite side of the second LOS 1830B and reflect light in substantially opposite directions.

[0229] The second LOS1830B is positioned across the first LOS1830A such that the incident light beam 1810 passes through the first LOS1830A at least partially and enters the second LOS1830B. As the incident light beam 1810 passes through the first LOS1830A, a portion of it is partially reflected by the second reflective surface 1834. The portion of the incident light beam 1810 passing through the second LOS1830B is reflected by the third reflective surface 1836 in substantially the same direction as the portion of the incident light beam 1810 reflected by the second reflective surface 1834. Before the reflected beamlet 1816 exits the second LOS1830B, a portion of the reflected beamlet 1816 is reflected by the fourth reflective surface 1838 so as to return towards the third reflective surface 1836. The addition of a fourth reflective surface 1838 within the second LOS 1830B results in a further doubling of the number of beamlets 1816 propagating along the first and second LOS 1830A, 1830B by substantial TIR, even compared to the beam multiplier tube 1730 depicted in Figure 22A. As shown in Figure 23, the addition of the fourth reflective surface 1838 results in an additional bounce for each optical beam 1810 / beamlet 1816, thereby doubling the number of beamlets produced in each interaction with the first and second LOS 1830A, 1830B (i.e., the optical multiplier tube 1830).

[0230] The beam multiplier tube 1930 depicted in Figure 24 includes first and second LOS 1930A, 1930B, similar to the beam multiplier tube 1830 depicted in Figure 23. The difference between beam multiplier tubes 1830, 1930 is that the beam multiplier tube 1930 depicted in Figure 24 includes a third LOS 1930C. Like the second LOS 1930B, the third LOS 1930C includes opposing reflective surfaces (i.e., fifth and sixth reflective surfaces 1940, 1942) that reflect light in substantially opposite directions. The fifth and sixth reflective surfaces 1940, 1942 are located on the opposite side of the third LOS 1930C.

[0231] A third LOS1930C is positioned across the second LOS1930B (and therefore the first LOS1930A) such that the incident light beam 1910 passes at least partially through the first and second LOS1930A, 1930B and enters the third LOS1930C. As the incident light beam 1910 passes through the first LOS1930A, a portion of it is partially reflected by the second reflective surface 1934. Similarly, as the incident light beam 1910 passes through the second LOS1930B, a portion of it is partially reflected by the third reflective surface 1936. The portion of the incident light beam 1910 passing through the second LOS1930B is reflected by the third reflective surface 1936 in substantially the same direction as the portion of the incident light beam 1910 reflected by the second reflective surface 1934. Similarly, a portion of the incident light beam 1910 passing through the third LOS 1930C is reflected by the fifth reflective surface 1940 in substantially the same direction as the portion of the incident light beam 1910 reflected by the second and third reflective surfaces 1934 and 1936, respectively.

[0232] Before the reflected beamlet 1916 exits the second LOS 1930B, a portion of the reflected beamlet 1916 is reflected back towards the third reflective surface 1936 by the fourth reflective surface 1938. Similarly, before the reflected beamlet 1916 exits the third LOS 1930C, a portion of the reflected beamlet 1916 is reflected back towards the fifth reflective surface 1940 by the sixth reflective surface 1942. The addition of the third LOS 1930C and its fifth and sixth reflective surfaces 1940, 1942 results in a further doubling of the number of beamlets 1916 propagating along the first, second, and third LOS 1930A, 1930B, and 1930C by substantial TIR. As shown in Figure 24, the addition of a third LOS1930C results in an additional pair of bounces for each optical beam 1910 / beamlet 1916, thereby doubling the number of beamlets produced in each interaction with the first, second, and third LOS1930A, 1930B, and 1930C (i.e., the photomultiplier tube 1930).

[0233] Multi-surface beam doubling tubes can be fabricated using a lamination process. In some embodiments, a second substrate (e.g., a second LOS) having a second thickness is laminated on a first substrate (e.g., a first LOS) having a first thickness. The interface between the two substrates may be partially reflective (e.g., a metal coating / semisilver mirror, a thin film coating, a dichroic mirror, a dielectric interface, a diffraction grating, a diffraction element, etc.). In another embodiment, a separate waveguide / LOE can be laminated together with a partially reflective interface.

[0234] Furthermore, the thickness ratio of the first and second LOS (and various secondary combinations of any multiple LOS in the system) can also affect beamlet doubling due to beamlet overlap. If the individual thicknesses are integer multiples or ratios (i.e., coefficients), cloned beamlets may overlap when they exit the first and second LOS, reducing the degree of beamlet doubling. Thus, in some embodiments (see Figure 22B), the first thickness of the first LOS may be a non-even coefficient of the second thickness of the second LOS. For example, the first thickness may be 0.3256 times the second thickness (e.g., instead of 0.2 or 0.5). Quasi-random beamlet arrays with multiple LOS may be insensitive to angles or imperfect in LOS thickness.

[0235] Beam doublers can also be adjusted by varying the degree of reflectivity / transmittance of various surfaces (e.g., other than 50 / 50). Using this and other techniques, doublers can be adjusted to have a uniform energy distribution across the beamlets. For moderate beam doubling amounts (e.g., sufficient to fill the pupil of the eye), there may be two beam doublers to ensure that the beamlets (and groups thereof) have the same amount of energy as the eye sweeps across different sets of beamlets. Equalizing the amount of energy across the beamlets minimizes intensity drops (artifacts; winking) as the user's eye sweeps the FOV. With an exponential increase in the number of beamlets, the beamlets will eventually overlap randomly, thereby reducing intensity artifacts.

[0236] Figure 25 depicts a beam multiplier tube 2030 that is tuned / optimized to produce most of the light (e.g., with an optimal beam diameter / energy distribution) for a beamlet 2016 directed toward the center 2044 of the FOV. For example, the beam multiplier tube 2030 can be tuned to vary the light intensity / energy as a function of the angle of the beamlet 2016 that will emerge from the beam multiplier tube 2030. The beamlet 2016 is directed toward the center 2044 of the FOV so that it is more perpendicular / orthogonal (i.e., has a smaller incident angle) to the surface of the beam multiplier tube 2030. This design minimizes artifacts at the center 2044 of the FOV, which some users' eyes will be directed toward for most of the time, while simultaneously controlling the amount of energy required to display the image. As a trade-off, the beam multiplier tube 2030 is not as tuned / optimized for more eccentric beamlets 2016 in the peripheral part of the FOV.

[0237] The field of view (FOV) may be expanded using a kaleidoscopically tuned beam multiplier tube. The relative reflectivity of the surface can be tuned so that the beam multiplier tube has dense beam multiplication in optically important regions (e.g., the center of the FOV) and sparse beam multiplication in optically less important regions (e.g., the periphery of the FOV). The FOV can be determined for various types of eye tracking, including, but not limited to, interpupillary distance measurement and pupillary movement tracking.

[0238] The OPE494 and EPE496 depicted in Figure 67 are not covered / covered by each other. However, if the OPE covers the EPE or part thereof, there is an increased chance of multiple reflections of the beam (i.e., mirrored beam) that may be emitted from LOE490 toward the user's eye. Mirrored beams are phase-shifted and can result in artifacts (e.g., bullseye or Fresnel zone artifacts "FZA"). One way to reduce FZA is by using an anti-reflective coating to reduce the mirrored beam. Another way to reduce FZA is to separate the thin waveguide OPE from the EPE. The thickness of the thin waveguide OPE can also be adjusted to minimize FZA, as the thin waveguide OPE brings the beamlet back into phase with respect to one wavelength (e.g., using the 2π thickness relation). The relative phase difference between beamlets is a function of wavelength and scanning angle. The thickness of the thin waveguide OPE can be adjusted to minimize FZA with respect to green light, which the human eye is most sensitive to. For example, a thin waveguide OPE can be tuned to 515nm-540nm, 520nm (green), or 532nm (green). In other embodiments, a thin waveguide OPE can be tuned to minimize FZA with 475nm (blue) or 650nm (red) light. Since the human eye is better able to distinguish blue light in the annular region around the fovea, certain FZAs are more harmful to blue light, and minimizing those FZAs with respect to blue light can significantly improve image quality. Therefore, a thin waveguide OPE can cover an EPE while reducing FZA when its thickness is tuned to have a 2π thickness relationship.

[0239] Figures 26A and 26B depict a beam multiplier tube 2600 having a refractive index gap (e.g., an air gap) 2602, which ensures that light propagates by substantial TIR at the interface (with a refractive index gap) rather than being partially transmitted into adjacent layers. The optical path beam through the multiplier tube begins with incidence into OPE12604 (e.g., a thicker LOS), exits OPE12604 via OCG2606, enters OPE22608 via ICG2610, and then passes through OPE22608 (e.g., a thinner LOS). The refractive index gap 2602 controls the optical flow through the beam multiplier tube 2600, allowing light to pass between OPE12604 and OPE22608 only through OCG2606 and ICG2610. By varying the thickness of OPE12604 and OPE22608, different periodic relationships can be achieved for OPE12604 and OPE22608. This can be adjusted to generate different spatial frequencies for beamlet cloning. The variable optical (optical modification) property described above is the LOE thickness, but other optical properties (such as diffraction) can also be varied to achieve effects similar to those described herein.

[0240] Two exit edges 2612 and 2614 exist for OPE12604 (see Figure 26B). In some embodiments, both exit edges are coupled to OPE2 2608. In other embodiments, the diffraction efficiency of OPE1 2604 can be varied so that in various parts of OPE1 2604, most of the light is directed to a single exit edge (e.g., 2606) which is coupled into OPE2 2608.

[0241] Using such a system, the OPE (as a separate element) can be removed from the LOE490 (see, for example, Figure 10) and extended into a separate layer 494 that covers the entire eyepiece or a significant portion thereof. Light is coupled into the LOE490 and incident on a separate large OPE494 for doubling, which acts as a controlled interface between the two optical elements. The light beam progresses stepwise through the OPE494 and can be doubling in accordance with multiple interactions with the elements of the OPE494. The beamlet exiting the OPE494 is not a single beam, but rather multiple superimposed beamlets from beam splitting by the OPE494.

[0242] The use of this design can also create a large region containing a smaller region in which all or most of the information / optical energy is contained. Such a system can transmit light to different layers (e.g., multiple depth planar layers) using a depth switching mechanism. The layers can be polymer dispersed liquid crystal ("PDLC") switchable layers. Alternatively, the layers can be waveguides with separate LC shutters. Such a system can generate multiple output ports for redundant optical information, which can be selected by LC shutters or PDLC switches, using a TIR-based structure from the main LOE. In some embodiments, a single OPE can feed optical information to multiple EPE layers (e.g., EPEs corresponding to red, green, and blue light).

[0243] Figure 27 depicts a beam doubling tube 2700 in which a single OPE 2702 feeds optical information to two EPE layers 2704, 2706 using two spatially displaced OCGs 2708, 2710. OCG1 2708 couples OPE 2702 to EPE1 2704 through ICG1 2712. OCG2 2710 couples OPE 2702 to EPE2 2706 through ICG2 2714. OCG2708, 2710 can be PDLCs, which can be turned on or off. Alternatively, an LC shutter layer (not shown) can be interposed between OPE 2702 and the EPE layers 2704, 2706. In some embodiments, the number of EPE layers can be set to correspond to a number of multiple depth layers for the MR system. In an alternative embodiment, a single OCG can be divided into multiple windows with shutters or switches for selectively feeding optical information to multiple EPE layers. In another embodiment 2800 (Figure 28), OCGs 2808, 2810 can be formed at or from the two exit edges of OPE 2802.

[0244] Figure 29 depicts a beam doubling tube 2900 with OPE2902, which is designed similarly to a “mirror room”. In this independent large OPE module 2902, the input / primary beam 2904 is doubled by OPE2902, and the doubled beamlet exits OPE2902 via one or more OCG2906. Three of the four OPE edges 2908, 2910, and 2912 may be polished and coated with aluminum to make them reflective. Two opposing mirrors 2908 and 2912 reflect the beam and beamlet propagating through OPE2902, generating an additional beamlet (with identical optical information) as the reflected beamlet interacting with OPE2902. Such an OPE2902 may be tuned to have a low diffraction efficiency toward the OCG2906, but the beam doubling will be greatly increased with multiple passes through OPE2902. Optionally, OPE2902 may have one or more regions with relatively higher diffraction efficiencies 2914, and beam doubling may be facilitated by increasing the beam length through OPE2902 before the beam / beamlet exits through OCG2906.

[0245] In the similar embodiment 3000 depicted in Figure 30, only a small portion of two of the edges of OPE 3002, 3010, 3012 (vertical edges), and the third edge 3008, are polished and coated with aluminum to make them reflective. This treatment results in a reduced beamlet doubling but doubles the amount of area for emission 3016 (e.g., for OCG (not shown)). This design increases the surface area 3016 for external bonding.

[0246] In both embodiments depicted in Figures 29 and 30, OPE2902, 3002 can be optimized / tuned using variable diffraction efficiency. For example, the upper left region in both of these embodiments can be tuned to minimize light that is reflected back toward ICG2918, 3018, which may diffract light vertically and unintentionally couple out of OPE2902, 3002.

[0247] The beam doubling tube 3100 depicted in Figure 31 includes OPE3102, which is shared across wavelengths. The first OCG3104 is tuned to externally couple green light using blue and red absorbers 3106 coupled to the OCG3104. The second OCG3108 is tuned to externally couple blue and red (i.e., magenta) light using a green absorber 3110 coupled to the OCG3108.

[0248] The beam doubling tube 3200 depicted in Figure 32 includes an OPE 3202 with three output regions 3204, 3206, and 3208. The three output regions 3204, 3206, and 3208, along with matching absorbers 3210, 3212, and 3214, are tuned using OCG 3204, 3206, and 3208 to externally couple red 3204, green 3206, and blue 3208 light, respectively. The DOE 3216 within the OPE 3202 forms a "V" shape 3218 with an angle of approximately 90 degrees, although the DOE may form other shapes with different angles in other embodiments (e.g., to modify the beamlet density (not shown)).

[0249] The beam doubling tube 3300 depicted in Figures 33A-33I illustrates various "quilts" of different OPE3302 regions, allowing for tuning of OPE3302 for various external coupling patterns. In all of these OPE3302, a single input / primary beam 3304 is doubled, diffracted, and / or reflected by various components of OPE3302 to form various doubled beams / beamlets 3306 with various external coupling patterns. For example, Figure 33A depicts OPE3302 including three sections 3308, 3310, and 3312 having different diffraction properties. The three sections may be independently switchable PDLC components (e.g., for changing the external coupling pattern), or they may be static components. Figure 33C depicts OPE3302 having a diffraction section 3314 as well as first and second PDLC components 3316, 3318 (e.g., for changing the external coupling pattern). Figure 33G depicts OPE3302, in which DOE3320 within OPE3302 forms a "V" shape 3322 similar to OPE3202 in Figure 32.

[0250] Referring here to Figures 34-36, one specific embodiment of the display screen 110 will be described. As shown in Figure 34, the waveguide 172 is a single, integrated substrate or plane of an optically transparent material such as glass, fused silica, acrylic, or polycarbonate, but in an alternative embodiment, the waveguide 172 may consist of separate, distinctly different substrates or planes of an optically transparent material that are joined together in the same plane or different planes. The IC element 168 may be closely associated with (e.g., embedded within) the surface 180b of the waveguide 172 to receive the collimated light beam 250 from the image projection assembly 108 into the waveguide 172 via surface 180b, but in an alternative embodiment, the IC element 168 may be associated with another surface 180a or even an edge of the waveguide 172 to couple the collimated light beam 250 into the waveguide 172 as an internally coupled light beam (e.g., embedded within). DOE174 is associated with the waveguide 172 (for example, incorporated within the waveguide 172, or in contact with or adjacent to one or more of the surfaces 180a, 180b of the waveguide 172) in order to extend the effective entrance pupil of the collimated light beam 250 in two dimensions, as briefly discussed above.

[0251] To achieve this objective, the DOE 174 comprises an orthogonal pupil dilation (OPE) element 186, which is closely associated with (e.g., built into) the plane 180b of the waveguide 172 to split the internally coupled light beam 252 into orthogonal light beamlets 254, and an exit pupil dilation (EPE) element 188, which is closely associated with (e.g., built into) the plane 180b of the waveguide 172 to split the orthogonal light beamlets 254 into a set of externally coupled light beamlets 256 that exit from the plane 180b of the waveguide 172 toward the eye 52 of the end user 50. In alternative embodiments where the waveguide 172 consists of distinctly different planes, the OPE element 174 and the EPE element 188 may be incorporated into the different planes of the waveguide 172.

[0252] The OPE element 186 relays light along the first axis (horizontal or x-axis in Figure 34) and extends the effective pupil of the light along the second axis (vertical or y-axis in Figure 34). In particular, as best shown in Figure 35, the IC element 168 optically internally couples the collimated light beam 250 as an internally coupled light beam in the waveguide 172 via TIR along an internal reflective optical path parallel to axis 262 (in this case, along the vertical or y-axis), thereby repeatedly intersecting with the OPE element 186. In the illustrated embodiment, the OPE element 186 has a relatively low diffraction efficiency (e.g., less than 50%), and at each intersection with the OPE element 186, a portion of the internally coupled light beam 252 (e.g., more than 90%) is diffracted through TIR along an internal reflective optical path parallel to axis 262 (y-axis) and propagates through TIR along an internal reflective optical path parallel to axis 262 (y-axis) and through a series of diagonal diffraction elements (45 degrees with respect to the x-axis) so as an orthogonal light beamlet 254 (shown as a dashed line in Figure 35) and propagates through TIR along an internal reflective optical path parallel to axis 264 (in this case, horizontal or along the x-axis) and through the waveguide 172 toward the EPE element 188, comprising a series of diagonal diffraction elements (45 degrees with respect to the x-axis). Although axis 264 is described as being perpendicular or orthogonal to axis 262 (y-axis), it should be understood that axis 264 may, alternatively, be oriented obliquely to axis 262 (y-axis).

[0253] In a similar scheme, at each intersection with the OPE element 186, a portion (e.g., more than 90%) of each orthogonal beamlet 254 continues to propagate through TIR along a separate internal reflective optical path parallel to axis 264 (x-axis) within the waveguide 172, while the remaining portion (e.g., less than 10%) of the individual orthogonal beamlets 254 is diffracted as a secondary beamlet 256, propagating through TIR along a separate internal reflective optical path (indicated by dashed lines) parallel to axis 262 (y-axis) within the waveguide 172. Consequently, at each intersection with the OPE element 186, a portion of each secondary beamlet 256 (e.g., more than 90%) continues to propagate through TIR along a separate internal reflective optical path parallel to axis 262 (y-axis) within the waveguide 172, while the remaining portion of each secondary beamlet 256 (e.g., less than 10%) is combined in phase with the orthogonal beamlet 254 and diffracted as a tertiary beamlet 258 that propagates through TIR along a separate internal reflective optical path parallel to axis 264 (x-axis) within the waveguide 172.

[0254] Therefore, by splitting the internally coupled light beam 252 into multiple orthogonal light beamlets 254 that propagate through the waveguide 172 along separate internal reflective optical paths parallel to axis 264 (x-axis) via TIR, the entrance pupil of the collimated light beam 250 internally coupled into the display screen 110 is extended vertically along the y-axis by the OPE element 186.

[0255] The EPE element 188 further extends the effective exit pupil of light along the first axis (horizontal x-axis in Figure 36). In particular, as best shown in Figure 36, the EPE element 188, like the OPE element 186, has a relatively low diffraction efficiency (e.g., less than 50%), and at each intersection with the EPE element 188, a portion of each orthogonal beamlet 254 (e.g., more than 90%) continues to propagate within the waveguide 172 along separate internal reflective optical paths parallel to axis 264 (x-axis), while the remainder of each orthogonal beamlet 254 is diffracted as an externally coupled beamlet 256 that exits from the plane 180b of the waveguide 172 (along the z-axis), as shown in Figure 36. In other words, each time the optical beamlet strikes the EPE element 188, a portion of it will be diffracted toward the surface 180b of the waveguide 172, while the remainder will continue to propagate within the waveguide 172 via TIR along an internal reflective optical path parallel to axis 264 (x-axis).

[0256] Therefore, by dividing each orthogonal light beamlet 254 into multiple externally coupled light beamlets 256, the entrance pupil of the collimated light beam 250 is further extended horizontally along the x-axis by the EPE element 188, resulting in a two-dimensional array of externally coupled light beamlets 256 that resembles a larger version of the original internally coupled light beam 252.

[0257] Although the OPE element 186 and EPE element 188 are shown in Figure 34 so as not to overlap in the xy plane, it should be noted that the OPE element 186 and EPE element 188 may completely overlap with each other in the xy plane, as shown in Figure 39, or may partially overlap with each other in the xy plane, as shown in Figure 38. In both cases, as in the embodiment shown in Figure 34, the OPE element 186 will split the internally coupled optical beam 252, which propagates through the waveguide 172 along an internally reflected optical path parallel to axis 262 (y-axis) via TIR, into orthogonal optical beamlets 254, which propagate through the waveguide 172 along separate internally reflected optical paths parallel to axis 264 (x-axis) via TIR. In these cases, the OPE element 186 and EPE element 188 will need to be positioned on opposite faces 180a and 180b of the waveguide 172, respectively.

[0258] In addition to its function of externally coupling the optical beamlet 256 from the surface 180b of the waveguide 172, the EPE element 188 also plays a role in focusing the output set of the optical beamlet 256 along a given focal plane so that it can be seen by the end user 50 at a viewing distance where a portion of the image or virtual object coincides with the focal plane. For example, if the EPE element 188 has only a linear diffraction pattern, the externally coupled rays 256 emanating from the surface 180b of the waveguide 172 toward the end user 50's eye 52 will be substantially parallel, as shown in Figure 39A, and will be interpreted by the end user 50's brain as light from the viewing distance (focal plane) at optical infinity. However, if the EPE element 188 has both a linear diffraction pattern component and a radially symmetric diffraction pattern component, the externally coupled light beamlet 256 emanating from the surface 180b of the waveguide 172 will be rendered more divergent from the viewpoint of the end user's eye 52 (i.e., convex curvature is imparted to the light wavefront), requiring the eye 52 to adjust to a closer distance and bring the resulting image into focus on the retina, which will be interpreted by the end user's brain as light from a viewing distance closer to the eye 52 than optical infinity (e.g., 4 meters), as shown in Figure 39B. The externally coupled light beamlet 256 emanating from the surface 180b of the waveguide 172 is rendered further diverging from the viewpoint of the end-user's eye 52 (i.e., a greater convex curvature will be imparted to the light wavefront), which may require the eye 52 to adjust to a closer distance and bring the resulting image into focus on the retina, and will be interpreted by the end-user's brain as light from a closer viewing distance (e.g., 0.5 meters) to the eye 52, as shown in Figure 39C.

[0259] Although the waveguide apparatus 170 is described herein as having only one focal plane, it should be understood that multiple planar optical waveguides 172, with associated OPE 176 and EPE 178, can be used to generate images on multiple focal planes simultaneously or sequentially, as discussed in U.S. Patent Publications 2015 / 0309264 and 2015 / 0346490 (expressly incorporated herein by reference).

[0260] As mentioned above, it is desirable to increase the saturation or internal filling of the exit pupil of the display screen 110. Without modification, the exit pupil of the display screen 110 may not be optimally saturated. For example, as shown in Figure 40A, the pupil of the collimated light beam 250 may extend to the exit pupil 300a of the 3×3 array of externally coupled light beamlets 256, which is relatively sparse by nature (i.e., the gaps between the externally coupled light beamlets 256 are relatively large). However, the display screen 110 can be improved to extend the pupil of the collimated light beam 250 to the more saturated 9×9 array of exit pupil 300b of the externally coupled light beamlets 256 using beam doubling features, as shown in Figure 40B.

[0261] For example, in some embodiments, two OPE186s are employed to double the number of orthogonal beamlets 254 acquired from the internally coupled light beam 252, and thus double the saturation of the two-dimensional array of externally coupled light beamlets 256 emanating from the surface 180b of the waveguide 172.

[0262] In particular, as shown in Figures 41-43, waveguide apparatus 170a is similar to waveguide apparatus 170 described, but waveguide apparatus 170a divides the internally coupled light beam 252, which propagates within waveguide 172 along an internally reflected optical path parallel to axis 262 (y-axis) via TIR, into a first set of orthogonal light beamlets 254a for propagation within waveguide 172 via TIR along separate internally reflected optical paths parallel to axis 264 (x-axis), adjacent to the first surface 180a of waveguide 172 (for example, above The system comprises a first OPE element 186a (best shown in Figure 41) positioned on the second surface 180b of the waveguide 172, and a second OPE element 186b positioned adjacent to (e.g., on) the second surface 180b of the waveguide 172 to split an internally coupled light beam 252, which propagates through TIR along an internally reflected optical path parallel to axis 262 (y-axis) within the waveguide 172, into a second set of orthogonal light beamlets 254b for propagation through TIR along a separate internally reflected optical path parallel to axis 264 (x-axis) within the waveguide 172. The first and second sets of orthogonal light beamlets 254a, 254b alternate with each other, as best shown in Figure 41.

[0263] That is, the internally coupled light beam 252, propagating through the waveguide 172 along an internal reflective optical path parallel to axis 262 (y-axis) via TIR, alternately intersects with the first and second OPE elements 186a, 186b on the opposite faces 180a, 180b of the waveguide 172. As a result, portions of the internally coupled light beam 252 are diffracted as primary sets 254a, 254b of first and second light beamlets, respectively, for propagation through the waveguide 172 along alternating internal reflective optical paths parallel to axis 264 (x-axis) via TIR. Secondary light beamlets 256a, 256b (shown in Figures 41 and 42) are also generated from beamlets 254a, 254b, respectively, which further create tertiary light beamlets 258a, 258b (shown only in Figure 41), which are combined in phase with the orthogonal light beamlets 254a, 254b, respectively. Consequently, the primary sets 254a and 254b of the first and second optical beamlets intersect with the EPE element 188 on the surface 180b of the waveguide 172, and portions thereof are diffracted as the first externally coupled optical beamlet set 256a and the second externally coupled optical beamlet set 256b, respectively, exiting from the surface 180b of the waveguide 172. Therefore, doubling the orthogonal optical beamlets 254 corresponds to increasing the saturation of the exit pupil 300a, which is expanded by the display screen 110 (shown in Figure 40B).

[0264] In another embodiment, a partially reflective interface is incorporated into the waveguide 172 to increase the number of light beamlets propagating within the waveguide 172, and thus increase the saturation of the two-dimensional array of externally coupled light beamlets 256 emanating from the surface 180b of the waveguide 172. In the embodiment illustrated below, the waveguide 172 comprises a plurality of layered substrates having at least one pair of adjacent substrates and a partially reflective interface between each pair of adjacent substrates, such that a light beam intersecting each semi-reflective interface is divided into a plurality of beamlets propagating within the waveguide 172 via TIR, thereby increasing the density of externally coupled light beamlets emanating from the surface 180b of the waveguide 172. Note that the adjacent substrates described below are not drawn to exact scale and are shown as multiples of each other for the sake of simplification. However, adjacent substrates may be non-multiples of each other, preferably non-multiples, so as to maximize the density of internal filling of the externally coupled light beamlet that exits from the surface of the waveguide.

[0265] In particular, referring to Figure 44-46, the waveguide apparatus 170b is similar to the waveguide apparatus 170 described, but the waveguide 172 is a composite substrate consisting of a primary waveguide 172a and a secondary waveguide 172b. The waveguide apparatus 170b further includes a semi-reflective interface 190 positioned between the primary waveguide 172a and the secondary waveguide 172b.

[0266] In some embodiments, the semi-reflective interface 190 may take the form of a semi-reflective coating, such as one made of a metal (e.g., gold, aluminum, silver, nickel-chromium, chromium), an oxide, a dielectric (e.g., a fluoride, sulfide), a semiconductor (e.g., silicon, germanium), and / or a glue or adhesive with reflective properties, and may be placed between the primary waveguide 172a and the secondary waveguide 172b via any preferred process such as physical vapor deposition (PVD), ion-assisted vapor deposition (IAD), or ion beam sputtering (IBS). The ratio of reflection to transmission of the semi-reflective coating 190 may be selected or determined, at least partially, based on the thickness of the coating 190, or the semi-reflective coating 190 may have a plurality of small perforations to control the ratio of reflection to transmission. In an alternative embodiment, the primary waveguide 172a and the secondary waveguide 172b are made of materials having different refractive indices such that the interface between waveguides 172a and 172b is semi-reflective with respect to light incident on the semi-reflective interface at an angle less than the critical angle (i.e., the angle of incidence at which some of the light is transmitted through the semi-reflective interface and the rest of the light is reflected by the semi-reflective interface). The semi-reflective interface 190 is preferably designed so as to preserve the angle of the light beam incident on the semi-reflective interface 190.

[0267] In either case, as best shown in Figure 45, the IC element 168 couples the collimated light beam 250 into the planar optical waveguide 172 as an internally coupled light beam 252, which propagates through the waveguide 172 via TIR along an internally reflected optical path parallel to the axis 262 (y-axis). The semi-reflective interface 190 is configured to split the internally coupled light beam 252 into a plurality of internally coupled light beamlets.

[0268] In particular, the semi-reflective interface 190 is configured to split the internally coupled light beam 252 into two primary internally coupled light beamlets (in this case, a first primary internally coupled light beamlet 252a (shown by a solid line) and a second primary internally coupled light beamlet 252b (shown by a dashed line)) that propagate through the primary waveguide 172a along an internal reflective optical path parallel to the axis 262 (y-axis). As shown in Figure 45, the semi-reflective interface 190 generates a secondary internally coupled light beamlet 252' that propagates through the secondary waveguide 172b along an internal reflective optical path parallel to the axis 262 (y-axis) via TIR, from which the second primary internally coupled light beamlet 252b is created.

[0269] Since the thickness of the primary waveguide 172 is a multiple of the thickness of the secondary waveguide 172b (in this case, exactly twice the thickness), it should be understood that only two primary internally coupled optical beamlets 252a and 252b are generated as a result of the rearrangement of the optical beamlets. However, in the preferred case where the thickness of the primary waveguide 172a is not a multiple of the thickness of the secondary waveguide 172b, additional primary internally coupled optical beamlets 252 are generated at each intersection between the secondary internally coupled optical beamlet 252' and the semi-reflective interface 190, and similarly, additional secondary internally coupled optical beamlets 252' are generated at each intersection between the primary internally coupled optical beamlet 252 and the semi-reflective interface 190. Thus, the number of primary internally coupled optical beamlets 252 increases geometrically along axis 262 from ICO168.

[0270] Each OPE element 186 is configured to split the primary internally coupled optical beamlets 252a and 252b into two sets of primary orthogonal optical beamlets. Specifically, the primary internally coupled optical beamlets 252a and 252b intersect with an OPE element 186 adjacent to the plane 180b of the waveguide 172 such that portions of the primary internally coupled optical beamlets 252a and 252b are diffracted through TIR as two sets of primary orthogonal optical beamlets 254a and 254b propagating through the waveguide 172 along separate internally reflected optical paths parallel to axis 264 (x-axis).

[0271] As best illustrated in Figure 46, the semi-reflective interface 190 is configured to split two sets of orthogonal beamlets 254a, 254b into four sets of orthogonal beamlets. In particular, the semi-reflective interface 190 splits the set of primary orthogonal beamlets 254a into two sets of primary orthogonal beamlets (in this case, the first set of primary orthogonal beamlets 254a(1) (shown by a solid line) and the second set of primary orthogonal beamlets 254a(2) (shown by a dashed line) which propagate through the TIR in the primary waveguide 172a along separate internal reflective optical paths parallel to axis 264 (x-axis). As shown in Figure 46, the semi-reflective interface 190 via the TIR A set of secondary orthogonal beamlets 252' is generated, propagating through the secondary waveguide 172b along a separate internal reflective optical path parallel to the x-axis 264', from which a second set of primary orthogonal beamlets 254a(2) is created. Similarly, the semi-reflective interface 190 divides the set of orthogonal beamlets 254b into two further sets of primary orthogonal beamlets (not shown), propagating through the TIR through the primary waveguide 172a along a separate internal reflective optical path parallel to the x-axis 264'.

[0272] It should be understood that since the thickness of the primary waveguide 172a is a multiple of the thickness of the secondary waveguide 172b (in this case, exactly twice the thickness), only two primary orthogonal beamlets 254 are generated from each orthogonal beamlet 254. However, in the preferred case where the thickness of the primary waveguide 172a is not a multiple of the thickness of the secondary waveguide 172b, additional primary orthogonal beamlets 254 are generated at each intersection between the secondary orthogonal beamlet 254' and the semi-reflective interface 190, and similarly, additional secondary orthogonal beamlets 254' are generated at each intersection between the primary internally coupled beamlet 254 and the semi-reflective interface 190. Thus, the number of primary orthogonal beamlets 254 increases geometrically along axis 264 (x-axis) from ICO168.

[0273] The EPE element 188 is configured to split each of the orthogonal beamlets into a set of externally coupled beamlets 256. For example, a set of primary orthogonal beamlets 254 (only sets 254a(1) and 254a(2) are shown) intersects with an EPE element 188 adjacent to the surface 180b of the waveguide 172 such that a portion of the primary orthogonal beamlets 254 is diffracted as a set of externally coupled beamlets 256 that exit the surface 180b of the waveguide 172. Thus, increasing the number of internally coupled beamlets 252 and the number of orthogonal beamlets 254 correspondingly increases the saturation of the exit pupil 300a, which is expanded by the display screen 110 (shown in Figure 40B).

[0274] Referring to Figures 47A-47D, a manner in which the semi-reflective interface 190 doubles the optical beam (in this case, an internally coupled optical beam 252, but the same technique can be applied to an orthogonal beam 254) into multiple beamlets 252 (in this case, two optical beamlets 252a and 252b) will be described. In the embodiment of Figures 47A-47D, the primary waveguide 172a is a multiple of the secondary waveguide 172b, and therefore the primary optical beamlet 252 and the secondary optical beamlet 252' may share several intersections at the semi-reflective interface 190. However, as briefly discussed above, the primary waveguide 172a is preferably a non-multiple of the secondary waveguide 172b so that the number of common intersections at the semi-reflective interface 190 is minimized, thereby generating additional optical beamlets 252 and maximizing the internal filling of the externally coupled beamlets.

[0275] At the first intersection P1 with the semi-reflective interface 190, a portion of the light beam 252 is transmitted through the semi-reflective interface 190 into the secondary waveguide 172b as a secondary light beamlet 252', which is reflected by the surface 180a of the waveguide 172 back to the second intersection P2 of the semi-reflective interface 190, while a portion of the light beam 252 is reflected by the semi-reflective interface 190 back into the primary waveguide 172a as a primary light beamlet 252a, which is reflected by the surface 180b of the waveguide 172 back to the third intersection P3 of the semi-reflective interface 190 (Figure 47A).

[0276] At the second intersection P2 with the semi-reflective interface 190, a portion of the secondary beamlet 252' is transmitted through the semi-reflective interface 190 into the primary waveguide 172b as the primary beamlet 252b, which is reflected by the surface 180a of the waveguide 172 back to the fourth intersection P4 of the semi-reflective interface 190. Meanwhile, a portion of the secondary beamlet 252' is reflected by the semi-reflective interface 190 back into the secondary waveguide 172b as the secondary beamlet 252', which is reflected by the surface 180a of the waveguide 172 back to the third intersection P3 of the semi-reflective interface 190 (Figure 47B).

[0277] At the third intersection P3 with the semi-reflective interface 190, a portion of the primary beamlet 252a is transmitted through the semi-reflective interface 190 into the secondary waveguide 172b, and a portion of the secondary beamlet 252' is reflected back into the secondary waveguide 172b by the semi-reflective interface 190. Some of this is incidentally combined with the secondary beamlet 252' and reflected back to the fourth intersection P4 by the surface 180b of the waveguide 172 (Figure 47C). Naturally, the primary beamlet 252a and the secondary beamlet 252' may not have a common intersection P3, in which case an additional secondary beamlet 252' may be generated. Furthermore, at the third intersection P3 with the semi-reflective interface 190, a portion of the secondary beamlet 252' is transmitted through the semi-reflective interface 190 into the primary waveguide 172a, and a portion of the primary beamlet 252a is reflected back into the primary waveguide 172a by the semi-reflective interface 190. This portion can be combined with the primary beamlet 252a, which is then reflected back to the fifth intersection P5 of the semi-reflective interface 190 by the surface 180b of the waveguide 172 (Figure 47C). Naturally, the secondary beamlet 252' and the primary beamlet 252a may not have a common intersection P3, in which case an additional primary beamlet 252 may be generated.

[0278] At the fourth intersection P4 with the semi-reflective interface 190, a portion of the primary beamlet 252b is transmitted through the semi-reflective interface 190 into the secondary waveguide 172b, and a portion of the secondary beamlet 252' is reflected back into the secondary waveguide 172b by the semi-reflective interface 190. This portion may be combined with the primary beamlet 252' and reflected back to the fifth intersection P5 by the surface 180b of the waveguide 172 (Figure 47D). Naturally, the primary beamlet 252b and the secondary beamlet 252' may not have a common intersection P4, in which case an additional secondary beamlet 252' may be generated. Furthermore, at the fourth intersection P4 with the semi-reflective interface 190, a portion of the secondary beamlet 252' is transmitted through the semi-reflective interface 190 into the primary waveguide 172a, and a portion of the primary beamlet 252b is reflected back into the primary waveguide 172a by the semi-reflective interface 190. This portion is combined with the secondary beamlet 252b, which is then reflected back to the sixth intersection P6 of the semi-reflective interface 190 by the surface 180b of the waveguide 172 (Figure 47D). Naturally, the secondary beamlet 252' and the primary beamlet 252b may not have a common intersection P4, in which case an additional primary beamlet 252 may be generated.

[0279] Therefore, from the foregoing, it can be understood that light energy is transmitted between the primary waveguide 172a and the secondary waveguide 172b, generating and propagating two light beamlets 252a and 252b within the waveguide apparatus 170.

[0280] Importantly, the thickness of the layered substrate is selected in conjunction with the expected angle of incidence of the light beam onto each semi-reflective interface, so that there are no gaps between the edges of adjacent externally coupled beamlets 256.

[0281] For example, in the embodiment illustrated in Figures 44-46, the thickness of the secondary waveguide 172b is less than the thickness of the primary waveguide 172a, and the thickness Δt of the secondary waveguide 172b is selected such that the distance between the centers of adjacent resulting externally coupled light beamlets 256 is less than or equal to the width w of the collimated light beamlet 250. Naturally, if the primary waveguide 172a is not a multiple of the secondary waveguide 172b, the distance between the centers of adjacent resulting externally coupled light beamlets 256 may exceed the width w of the collimated light beamlet 250.

[0282] It should be noted that the width w of the collimated light beam 250 relative to the size of the IC element 168 is exaggerated for illustrative purposes. In reality, the width w of the collimated light beam 250 will be much smaller than the size of the IC element 168, and it will need to be large enough to accommodate all scanning angles of the collimated light beam 250. In a preferred embodiment, the average spacing between adjacent externally coupled light beamlets 256 is minimized for the worst-case scanning angle. For example, with respect to the worst-case scanning angle, gaps may exist between some of the adjacent externally coupled light beamlets 256, but there will be no gaps between most of the adjacent externally coupled light beamlets 256.

[0283] Therefore, the thickness Δt of the secondary waveguide 172b may be selected to minimize the spacing between adjacent externally coupled beamlets 256 based on the worst-case scanning angle. Note that the worst-case scanning angle is the angle of incidence of the internally coupled light beam 252 onto the semi-reflective interface 190. Naturally, if the primary waveguide 172a is not a multiple of the secondary waveguide 172b, more externally coupled beamlets 256 will be generated, thereby inevitably reducing the average spacing between adjacent externally coupled beamlets 256. In this case, it may be beneficial to select thickness values ​​t and Δt that have a relatively high least common multiple. For example, when selecting thickness values ​​t and Δt, one may seek to maximize the least common multiple of the thickness values ​​t and Δt in order to maximize the amount of externally coupled beamlets 256 for the worst-case scanning angle. Furthermore, the selection of thickness values ​​t and Δt can also result in a non-uniform / complex distribution of the externally coupled beamlets 256, which can minimize the adverse effects created by coherent optical interactions between adjacent externally coupled beamlets 256.

[0284] For example, assuming that the worst-case incident angle between the internally coupled light beam 252 and the semi-reflective interface 190 is 60 degrees, and that the thickness t of the primary waveguide 172a is exactly twice the thickness Δt of the secondary waveguide 172b, then the thickness Δt of the secondary waveguide 172b is such that adjacent primary internally coupled light beamlets 252 have no gaps between them, as shown in Figure 48, adjacent primary orthogonal light beamlets 254 have no gaps between them, as shown in Figure 49, and therefore adjacent externally coupled light beamlets 256 have no gaps between them, the width w of the internally coupled light beam 252. [ka] That should be the case.

[0285] For the sake of simplification in this explanation, it should be understood that the absence of refraction of light transmitted through the semi-reflective interface 190 is assumed. However, if substantial refraction of light occurs when transmitted through the semi-reflective interface 190, the angle of light transmission due to such refraction must be taken into consideration when selecting the thickness Δt of the secondary waveguide 172b. For example, the greater the refraction of light, the greater the thickness Δt of the secondary waveguide 172b must be reduced to compensate for such refraction, so that the angle of light transmitted with respect to the semi-reflective interface 190 decreases.

[0286] Furthermore, as described above, it should be understood that the generation of a primary internally coupled light beamlet 252 propagating through the primary waveguide 172a along an internal reflective optical path parallel to axis 262 (y-axis) via TIR, and then the generation of a primary externally coupled light beamlet 256 propagating through the primary waveguide 172a along an internal reflective optical path parallel to axis 264 (x-axis), will completely fill the exit pupil of the display screen 110, assuming an appropriate thickness Δt of the secondary waveguide 172b.

[0287] If it is desirable to reduce the thickness Δt of the secondary waveguide 172b and further reduce the average spacing between adjacent primary internally coupled optical beamlets 252, primary orthogonal optical beamlets 254, and externally coupled optical beamlets 256, the thickness t of the primary waveguide 172a may be far greater than the thickness Δt of the secondary waveguide 172b, for example, three times, four times, five times, or even more.

[0288] For example, as illustrated with respect to the waveguide apparatus 170c in Figures 50 and 51, the thickness t of the primary waveguide 172a is three times the thickness Δt of the secondary waveguide 172b. As best shown in Figure 50, the IC element 168 couples the internally coupled optical beam 252 into the waveguide 172, which propagates through the waveguide 172 via TIR along an internally reflected optical path parallel to the axis 262 (y-axis). The semi-reflective interface 190 is configured to split the internally coupled optical beam 252 into three internally coupled optical beamlets. In particular, the semi-reflective interface 190 splits the internally coupled beam 252 into three primary internally coupled beamlets 252 (the first primary internally coupled beamlet 252a (shown by a solid line) and two further primary internally coupled beamlets 252b and 252c (shown by dashed lines)) that propagate through the primary waveguide 172a along separate internally reflected optical paths parallel to axis 262. As shown in Figure 50, the semi-reflective interface 190 generates a secondary internally coupled beamlet 252' that propagates through the secondary waveguide 172b along an internally reflected optical path parallel to axis 264' (x-axis) via TIR, from which two primary internally coupled beamlets 252b and 252c are created.

[0289] Since the thickness of the primary waveguide 172a is a multiple of the thickness of the secondary waveguide 172b (in this case, exactly three times the thickness), it should be understood that only three primary internally coupled optical beamlets 252a, 252b, and 252c are generated as a result of the rearrangement of the optical beamlets. However, in the preferred case where the thickness of the primary waveguide 172a is not a multiple of the thickness of the secondary waveguide 172b, additional primary internally coupled optical beamlets 252 are generated at each intersection between the secondary internally coupled optical beamlet 252' and the semi-reflective interface 190, and similarly, additional secondary internally coupled optical beamlets 252' are generated at each intersection between the primary internally coupled optical beamlet 252 and the semi-reflective interface 190. Thus, the number of primary internally coupled optical beamlets 252 increases geometrically along axis 262 (y-axis) from ICO168.

[0290] Each OPE element 186 is configured to split the primary internally coupled optical beamlets 252a-252c into a set of three primary orthogonal optical beamlets. Specifically, the primary internally coupled optical beamlets 252a-252c intersect with an OPE element 186 adjacent to the plane 180b of the waveguide 172 such that a portion of the primary internally coupled optical beamlets 252a-252c are diffracted as a set of three primary orthogonal optical beamlets 254a-254c that propagate through the waveguide 172 along separate internally reflected optical paths parallel to axis 264 (x-axis) via TIR.

[0291] As best illustrated in Figure 51, the semi-reflective interface 190 is configured to split a set of three orthogonal beamlets 254a-254c into a set of nine orthogonal beamlets. In particular, the semi-reflective interface 190 splits the set of primary orthogonal beamlets 254a into a set of three primary orthogonal beamlets 254a (shown by a solid line) and two further sets of primary internally coupled beamlets 254b, 254c (shown by dashed lines), which propagate through the TIR along separate internally reflected optical paths parallel to axis 264 (x-axis) within the primary waveguide 172a. As shown in Figure 51, the semi-reflective interface 190 propagates through the TIR along separate internally reflected optical paths parallel to axis 262' (y-axis) within the primary waveguide 172a. A set of secondary internally coupled optical beamlets 252' is generated, propagating through the secondary waveguide 172b along the TIR, from which two sets of primary internally coupled optical beamlets 254b and 254c are created. Similarly, the semi-reflective interface 190 divides the set of orthogonal optical beamlets 254b into a set of three more primary orthogonal optical beamlets (not shown) propagating through the primary waveguide 172a along separate internally reflected optical paths parallel to axis 264 (x-axis) via TIR, and the set of orthogonal optical beamlets 254c into a set of three more primary orthogonal optical beamlets (not shown).

[0292] Since the thickness of the primary waveguide 172a is a multiple of the thickness of the secondary waveguide 172b (in this case, exactly three times the thickness), it should be understood that only three sets of primary orthogonal optical beamlets 254a, 254b, and 254c are generated as a result of the rearrangement of the optical beamlets. However, in the preferred case where the thickness of the primary waveguide 172a is not a multiple of the thickness of the secondary waveguide 172b, an additional set of primary orthogonal optical beamlets 254 is generated at each intersection between the set of secondary orthogonal optical beamlets 254' and the semi-reflective interface 190, and similarly, an additional set of secondary orthogonal optical beamlets 254' is generated at each intersection between the set of primary orthogonal optical beamlets 254 and the semi-reflective interface 190. Thus, the number of primary orthogonal optical beamlets 254 increases geometrically along axis 264 (x-axis) from ICO168.

[0293] The EPE element 188 is configured to split a set of nine orthogonal beamlets into a set of 256 externally coupled beamlets. In particular, as shown in Figure 51, the set of primary orthogonal beamlets 254 (only sets 254a(1)-254a(3) are shown) intersects with the EPE element 188 adjacent to the surface 180b of the waveguide 172, such that a portion of the primary orthogonal beamlets 254 are diffracted as the set of externally coupled beamlets 256 that exit from the surface 180b of the waveguide 172. Thus, increasing the number of internally coupled beamlets 252 and the number of orthogonal beamlets 254 correspondingly increases the saturation of the exit pupil 300a, which is expanded by the display screen 110 (shown in Figure 40B).

[0294] Of particular note is that such saturation of the exit pupil 300a by waveguide apparatus 170c in Figures 50-51 is comparable to the saturation of the exit pupil 300a by waveguide apparatus 170b in Figures 45-46 when the width w of the collimated light beam 250 internally coupled in waveguide apparatus 170c is 2 / 3 smaller than the width of the collimated light beam 250 internally coupled in waveguide apparatus 170b. That is, the thickness Δt of the secondary waveguide 172b needs to be downscaled only in proportion to the decrease in the width w of the collimated light beam 250 internally coupled in waveguide apparatus 170b. For example, assuming that the same worst-case incident angle between the internally coupled light beam 252 and the semi-reflective interface 190 is 60 degrees, the thickness Δt of the secondary waveguide 172b is such that, as shown in Figure 52, the edges of adjacent primary internally coupled light beamlets 252 have no gaps between them, as shown in Figure 53, the edges of primary orthogonal light beamlets 254 have no gaps between them, and therefore the edges of adjacent externally coupled light beamlets 256 have no gaps between them, and the width w of the internally coupled light beam 252 is such that [ka] It can be scaled down.

[0295] From the foregoing, it can be understood that the thickness t of the primary waveguide 172a may be much larger than the width w of the collimated light beam 250 that is internally coupled in the waveguide apparatus 170b, 170c illustrated in Figures 44-53, while the thickness Δt of the secondary waveguide 172b may be smaller than the width w of the collimated light beam 250. However, if the thickness Δt of the secondary waveguide 172b, required to eliminate the resulting gap between the centers of adjacent externally coupled light beamlets 256, is too small for manufacturability purposes, assuming the worst-case scanning angle, the thickness of the secondary waveguide 172b may be alternatively selected such that the difference in thickness between the primary waveguide 172a and the secondary waveguide 172b is equal to the difference thickness Δt, as illustrated in the waveguide apparatus 170d in Figures 54 and 55.

[0296] Therefore, in this case, the thickness of the secondary waveguide 172b may be selected to be slightly less than the thickness t of the primary waveguide 172a, i.e., t-Δt. As best shown in Figure 54, the IC element 168 couples the internally coupled optical beam 252 into the waveguide 172, which propagates through the waveguide 172 via TIR along an internally reflected optical path parallel to the axis 262 (y-axis). The semi-reflective interface 190 is configured to split the internally coupled optical beam 252 into three internally coupled optical beamlets. In particular, the semi-reflective interface 190 splits the internally coupled beam 252 into three primary internally coupled beamlets 252 (the first primary internally coupled beamlet 252a (shown by a solid line) and two further primary internally coupled beamlets 252b and 252c (shown by dashed lines)) which propagate through the primary waveguide 172a along separate internally reflected optical paths parallel to axis 262. As shown in Figure 54, the semi-reflective interface 190 generates two secondary internally coupled beamlets 252(1)' and (2)' which propagate through the secondary waveguide 172b along separate internally reflected optical paths parallel to axis 262' (y-axis) via TIR, from which two primary internally coupled beamlets 252b and 252c are created.

[0297] Each OPE element 186 is configured to split the primary internally coupled optical beamlets 252a-252c into a set of three primary orthogonal optical beamlets. Specifically, the primary internally coupled optical beamlets 252a-252c intersect with an OPE element 186 adjacent to the plane 180b of the waveguide 172 such that a portion of the primary internally coupled optical beamlets 252a-252c are diffracted as a set of three primary orthogonal optical beamlets 254a-254c that propagate through the waveguide 172 along separate internally reflected optical paths parallel to axis 264 (x-axis) via TIR.

[0298] As best illustrated in Figure 55, the semi-reflective interface 190 is configured to split a set of three orthogonal beamlets 254a-254c into a set of nine orthogonal beamlets. In particular, the semi-reflective interface 190 splits the set of primary orthogonal beamlets 254a into a set of three primary orthogonal beamlets 254a (shown by a solid line) and two further sets of primary internally coupled beamlets 254b, 254c (shown by dashed lines), which propagate through the primary waveguide 172 along separate internally reflected optical paths parallel to axis 264' (x-axis). As shown in Figure 55, the semi-reflective interface 190 propagates through the secondary waveguide via a separate internally reflected optical path parallel to axis 264' (x-axis) Two sets of secondary internally coupled optical beamlets, 254(1)' and 254(2)', propagate within 172b, from which two sets of primary internally coupled optical beamlets, 254b and 254c, are created. Similarly, the semi-reflective interface 190 divides the set of orthogonal optical beamlets 254b into three more sets of primary orthogonal optical beamlets (not shown) propagating within the primary waveguide 172a along separate internally reflected optical paths parallel to axis 264 (x-axis), and the set of orthogonal optical beamlets 254c into three more sets of primary orthogonal optical beamlets (not shown).

[0299] The EPE element 188 is configured to split a set of nine orthogonal beamlets into a set of 256 externally coupled beamlets. In particular, as shown in Figure 55, the set of primary orthogonal beamlets 254 (only the sets of primary orthogonal beamlets 254a(1)-254a(3) are shown) intersects with the EPE element 188 adjacent to the surface 180b of the waveguide 172, such that a portion of the primary orthogonal beamlets 254 are diffracted as the set of externally coupled beamlets 256 that exit from the surface 180b of the waveguide 172. Thus, increasing the number of internally coupled beamlets 252 and the number of orthogonal beamlets 254 correspondingly increases the saturation of the exit pupil 300a, which is expanded by the display screen 110 (shown in Figure 40B).

[0300] The difference in thickness Δt between the primary waveguide 172a and the secondary waveguide 172b in the embodiment of Figures 54-55, assuming the same worst-case incident angle between the internally coupled light beam 252 and the semi-reflective interface 190 is 60 degrees, is such that the edges of adjacent primary internally coupled light beamlets 252 and adjacent primary orthogonal light beamlets 254 have no gap between them, and therefore the edges of adjacent externally coupled light beamlets 256 have no gap between them, and the width w of the internally coupled light beam 252 is such that the width w of the internally coupled light beam 252 [ka] It can be selected to be such. Therefore, in this case, the thickness of the secondary waveguide 172b will exceed the width w of the internally coupled light beam 252.

[0301] Although the waveguide devices 170a-170d illustrated in Figures 44-55 have been described as having only one secondary waveguide 172b, it should be understood that the waveguide device 170 may have multiple secondary waveguides 172b. For example, referring to Figures 56 and 57, the waveguide device 170e comprises two secondary waveguides 172b and four semi-reflective interfaces 190 arranged on the primary waveguide 172a, one of which is positioned between the primary waveguide 172a and one of the secondary waveguides 172b, and the remaining one is positioned between the individual secondary waveguides 172b.

[0302] As best shown in Figure 56, the IC element 168 couples the internally coupled optical beam 252 into the waveguide 172, which propagates through the waveguide 172 via TIR along an internally reflected optical path parallel to the axis 262 (y-axis). The semi-reflective interface 190 is configured to split the internally coupled optical beam 252 into three internally coupled optical beamlets. In particular, the semi-reflective interface 190 splits the internally coupled beam 252 into three primary internally coupled beamlets 252 (the first primary internally coupled beamlet 252a (shown by a solid line) and two further primary internally coupled beamlets 252b and 252c (shown by dashed lines)) which propagate through the primary waveguide 172a along separate internally reflected optical paths parallel to axis 262' (y-axis). As shown in Figure 56, the semi-reflective interface 190 generates two secondary internally coupled beamlets 252' which propagate through the TIR through two separate secondary waveguides 172b along separate internally reflected optical paths parallel to axis 262' (y-axis), from which the two primary internally coupled beamlets 252b and 252c are created.

[0303] Each OPE element 186 is configured to split the primary internally coupled optical beamlets 252a-252c into a set of three primary orthogonal optical beamlets. Specifically, the primary internally coupled optical beamlets 252a-252c intersect with an OPE element 186 adjacent to the plane 180b of the waveguide 172 such that a portion of the primary internally coupled optical beamlets 252a-252c is diffracted as a set of three primary orthogonal optical beamlets 254a-254c that propagate through the waveguide 172 along an internal reflective optical path parallel to axis 264 (x-axis) via TIR.

[0304] As best shown in Figure 57, the semi-reflective interface 190 is configured to split the set of three orthogonal beamlets 254a-254c into a set of nine orthogonal beamlets. In particular, the semi-reflective interface 190 divides the set of primary orthogonal beamlets 254a into three sets of primary orthogonal beamlets 254a (shown by a solid line) and two further sets of primary orthogonal beamlets 254b, 254c (shown by dashed lines), which propagate through the TIR along separate internal reflective optical paths parallel to axis 264 (x-axis) within the primary waveguide 172a. As shown in Figure 57, the semi-reflective interface 190 generates two sets of secondary internally coupled beamlets 252', which propagate through the TIR along separate internal reflective optical paths parallel to axis 264' (x-axis) within two separate secondary waveguides 172b, from which two primary orthogonal beamlets 252b, 252c are created. Similarly, the semi-reflective interface 190 This divides the set of orthogonal beamlets 254b into three further sets of primary orthogonal beamlets (not shown) that propagate within the primary waveguide 172a along separate internal reflective optical paths parallel to axis 264 (x-axis), and the set of orthogonal beamlets 254c into three further sets of primary orthogonal beamlets (not shown). In some embodiments, the two secondary waveguides 172b may have different thicknesses. In addition, for reasons similar to those described above with reference to Figures 44-55, in some embodiments these different thicknesses may not be multiples of each other. Also, the thickness of the primary waveguide 172a may not be a multiple of one or both of the two different thicknesses of the two secondary waveguides 172b. In other embodiments, the two secondary waveguides 172b may have equal thicknesses.

[0305] The EPE element 188 is configured to split a set of nine orthogonal beamlets into a set of 256 externally coupled beamlets. In particular, as shown in Figure 57, the set of primary orthogonal beamlets 254 (only the set of primary orthogonal beamlets 254a(1)-254a(3) is shown) intersects with the EPE element 188 adjacent to the surface 180b of the waveguide 172, such that a portion of the primary orthogonal beamlets 254 are diffracted as the set of externally coupled beamlets 256 that exit from the surface 180b of the waveguide 172. Thus, increasing the number of internally coupled beamlets 252 and the number of orthogonal beamlets 254 correspondingly increases the saturation of the exit pupil 300a, which is expanded by the display screen 110 (shown in Figure 40B). Although the waveguide apparatus 170e illustrated in Figures 56 and 57 has been described above to comprise two secondary waveguides 172b, it should be understood that the waveguide apparatus 170e and others described herein may have at least two (e.g., three, four, five, or more) secondary waveguides 172b.

[0306] In the embodiments described above, the entrance pupil of the collimated light beam output by the collimation element 154 is extended only by the combination of the OPE element 186 and EPE element 188 of the display screen 110, and includes features closely associated with the OPE element 186 and EPE element 188 for increasing the saturation of the exit pupil of the display screen 110. Subsequently, in embodiments of the display subsystem 104' described herein, the image projection assembly 108 further includes a pre-pupil extension (PPE) 192, which, in the embodiment illustrated in Figure 58, is positioned between the collimation element 166 and IC element 168 of the display screen 110.

[0307] PPE192 represents the first pupil dilation stage, which is designed to pre-dilate the entrance pupil of the collimated light beam 250 to the intermediate exit pupil 300a of the initial set of externally coupled light beamlets 256' (in this case, a two-dimensional 3x3 array) prior to internal coupling of the display screen 110 into the waveguide apparatus 170 using one or more beam doubling techniques (emulating the input of a conventional collimated light beam with a larger pupil size, as shown in Figure 59A). The display screen 110 then represents the second pupil dilation stage, which further dilates the pupil size of the collimated light beam 250 to the final exit pupil 300b of the final set of externally coupled light beamlets 256 (in this case, a two-dimensional 9x9 array), in a conventional manner, as shown in Figure 59B.

[0308] In an alternative embodiment, the display screen 110 may further expand the pupil size of the collimated light beam 250 to the exit pupil of a more saturated final externally coupled light beamlet set 256 using the improved beam doubling technique described above. However, it should be understood that the use of the PPE 192 is particularly well suited to small imaging devices that output a relatively small pupil-sized light beam, which can be expanded to a normal pupil-sized light beam for input into a conventional PE for expansion to an exit pupil proportional to the entrance pupil size of the end user's eye 52. For example, the PPE 192 can expand the entrance pupil of the collimated beam to a pre-expanded pupil (e.g., at least 0.5 mm pupil) that is at least 10 times larger than the entrance pupil (e.g., 50 mil pupil size), and the waveguide device 170 of the display screen 110 can further expand the pre-expanded pupil of the collimated light beam 250 to an exit pupil (e.g., at least 5 mm pupil) that is at least 10 times larger than the pre-expanded pupil of the collimated light beam 250. By utilizing a multi-stage pupil dilation system, the manufacturing constraints associated with dilating a collimated beam from a relatively small pupil to a relatively large and saturated exit pupil do not need to be imposed on a single pupil dilation device, but rather can be distributed across multiple dilation devices, thereby facilitating the manufacturing of the entire system.

[0309] Referring here to Figure 60-63, some embodiments of the display subsystem 104' utilize a conventional PE, comprising the waveguide device 170 shown in Figure 34-36 and a PPE 192a, which in the illustrated embodiments takes the form of a smaller version of the waveguide device 170 mounted on the IC element 168.

[0310] To achieve this objective, the PPE192a takes the form of a waveguide apparatus 170' having a size proportional to the size of the IC element 168 of the primary waveguide apparatus 170. Similar to the primary waveguide apparatus 170 of the display screen 110, the miniature waveguide apparatus 170' comprises a planar optical waveguide 172', which takes the form of a single, integrated substrate or plane of optically transparent material (as described above with respect to waveguide 172), and one or more DOEs 174' associated with the waveguide 172' to pre-two-dimensionally expand the effective exit pupil of a collimated light beam 250 that is optically coupled into the waveguide 172'. PPE192a further comprises an IC element 168' positioned on the surface 180b' of waveguide 172' to receive the collimated light beam 250 into waveguide 172' via surface 180b' from collimation element 166, although in alternative embodiments, the IC element 168' may be positioned on other surfaces 180a' or even on the edge of waveguide 172' to couple the collimated light beam 250 into waveguide 172 as an internally coupled light beam. DOE174' is associated with waveguide 172' (e.g., incorporated into waveguide 172' or in contact with or adjacent to one or more surfaces 180a', 180b' of waveguide 172') to pre-expand the effective entrance pupil of the collimated light beam 250 that is optically coupled into waveguide 172', as briefly discussed above.

[0311] To achieve this objective, the DOE174 comprises an orthogonal pupil extension (OPE) element 186 for splitting the internally coupled optical beam 252 into a set of initial orthogonal optical beamlets 254', and an exit pupil extension (EPE) element 188' for splitting each initial orthogonal optical beamlet 254' into a set of initial externally coupled optical beamlets 256' that exit from the plane 180b' of the waveguide 172'. In the particular embodiment illustrated in Figures 60-63, the OPE element 186' and the EPE element 188' completely overlap each other in the xy plane, so that the OPE element 186' is located on the plane 180a of the waveguide 172' and the EPE element 188' is located on the plane 180b of the waveguide 172'. Alternatively, the OPE element 186' and the EPE element 188' may not overlap at all in the xy plane, in which case both the OPE element 186' and the EPE element 188' may be located on the same plane 180b of the waveguide 172'.

[0312] The OPE element 186' relays the light along a first axis (horizontal or x-axis in Figure 60) and pre-extends the effective exit pupil of the light along a second axis (vertical or y-axis in Figure 60). In particular, as best shown in Figure 61, the IC element 168' optically internally couples the collimated light beam 250 as an internally coupled light beam 252' for propagation in the waveguide 172' along the internal reflective optical path 262 via TIR (in this case, along the vertical or y-axis), thereby repeatedly intersecting with the OPE element 186'. In the illustrated embodiment, the OPE element 186' has a relatively low diffraction efficiency (e.g., less than 50%) and comprises a series of diagonal diffraction elements (45 degrees with respect to the x-axis) such that at each intersection with the OPE element 186', a portion of the internally coupled light beam 252' (e.g., more than 90%) continues to propagate through the TIR along an internal reflective optical path parallel to axis 262 (y-axis) within the waveguide 172', and the remaining portion of the internally coupled light beam 252' (e.g., less than 10%) propagates through the TIR along an internal reflective optical path parallel to axis 264 (in this case, horizontal or along the x-axis) within the waveguide 172' toward the EPE element 188', as an initial orthogonal light beamlet 254' (shown as a dashed line in Figure 61). Although axis 264 is described as being perpendicular or orthogonal to axis 262 (y-axis), it should be understood that axis 264 may, alternatively, be oriented obliquely to axis 262.

[0313] Therefore, the entrance pupil of the collimated light beam 250, which is internally coupled into the miniature waveguide device 170' by splitting the internally coupled light beam 252' into multiple initial orthogonal light beamlets 254' that propagate along the parallel internal reflection optical path 264, is pre-extended perpendicularly along the y-axis by the OPE element 186'.

[0314] The EPE element 188' further pre-extends the effective pupil of light along the first axis (horizontal x-axis in Figure 62). In particular, the EPE element 188' has a relatively low diffraction efficiency (e.g., less than 50%) such that at each intersection with the EPE element 188', a portion (e.g., more than 90%) of each initial orthogonal optical beamlet 254' continues to propagate along a separate internal reflective optical path parallel to axis 264 (x-axis), while the remaining portion of each initial orthogonal optical beamlet 254' is diffracted as an initial externally coupled optical beamlet 256' that exits from the plane 180b' of the waveguide 172' (along the z-axis), as shown in Figure 62. In other words, each time the optical beamlet strikes the EPE element 188', a portion of it will be diffracted toward the plane 180b of the waveguide 172', while the remainder will continue to propagate along separate internal reflective optical paths parallel to axis 264 (x-axis).

[0315] Therefore, by splitting each initial orthogonal optical beamlet 254' into multiple initial externally coupled optical beamlets 256', the exit pupil of the internally coupled optical beam 252 is further pre-extended horizontally along the x-axis by the EPE element 188', resulting in a two-dimensional array of initial externally coupled optical beamlets 256' that are closer to a larger version of the original internally coupled optical beam 252.

[0316] With respect to Figures 34-36, in the same manner as described above, the primary waveguide apparatus 170 further expands the pupil of the collimated light beam 250 in two dimensions. That is, the initial externally coupled light beamlet 256' is input into the IC element 168 of the primary waveguide apparatus 170 as internally coupled light beamlets 252(1)-252(4), which are then divided by the OPE element 186 into a set of four orthogonal light beamlets 254(1)-254(4), which are further divided by the EPE element 188 into a final externally coupled light beamlet 256 that exits from the surface 180b of the waveguide 172 toward the eye 52 of the end user 50.

[0317] Therefore, as illustrated in Figure 63, the single collimated light beam 250 is split by the OPE element 186' into a one-dimensional array of four initial orthogonal light beamlets 254', which is further split by the EPE element 188' into a two-dimensional 4×4 array of initial externally coupled light beamlets 256', which is further split by the OPE element 174' into a two-dimensional 4×16 array of orthogonal light beamlets 254, which is further split by the OPE element 174' into a 16×16 array of final externally coupled light beamlets 256. As can be understood, the use of PPE 192a (i.e., the miniature waveguide device 170') increases the saturation of the exit pupil of the display screen 110 from the 4×4 array of final externally coupled light beamlets 256 to the 16×16 array of final externally coupled light beamlets 256. Naturally, PPE192a can be designed to create smaller or larger arrays of initial externally coupled optical beamlets 256', such as 2×2, 3×3, and 5×5 arrays, and furthermore, it can be designed to create non-square matrices of initial externally coupled optical beamlets 256', such as 2×3, 3×2, 3×4, and 4×3 arrays. Importantly, the thickness of the waveguide 172 of the primary waveguide apparatus 170 will exceed the thickness of the waveguide 172' of the miniature waveguide apparatus 170'. In this case, for the purpose of simplification in the illustration, the thickness of the primary waveguide 172 is four times the thickness of the secondary waveguide 172'. However, as discussed above with respect to the embodiment in Figures 44-57, it should be understood that it may be beneficial to maximize the least common multiple of the individual thickness values ​​of waveguides 172, 172', thereby maximizing the amount of exit pupil resulting for the widest scanning angle, and further minimizing the adverse effects created by coherent optical interactions between adjacent externally coupled beamlets 256, resulting in a non-uniform / complex distribution of the externally coupled beamlets 256.

[0318] Referring here to Figures 64-66, another embodiment of the display subsystem 104' utilizes a conventional PE, comprising the waveguide device 170 shown in Figure 34-36, and a PPE192b, which, like the PPE192a, pre-extends the effective entrance pupil of the collimated light beam 250 that is optically coupled into the PPE192b in a two-dimensional manner, but unlike the PPE192a, takes the form of an adapter rather than a waveguide.

[0319] In particular, PPE192b includes a diffraction beam splitter 194 that utilizes a single DOE to split a collimated light beam 250 into a set of initial externally coupled light beamlets 256'. As best shown in Figures 65 and 66, the diffraction beam splitter 194 includes an optical planar substrate 196 having opposing first and second faces 196a, 196b and a diffraction grating 198 associated with one of the faces 196a, 196b and, in this case, face 196b of the substrate 196. The diffraction grating 198 splits the collimated light beam 250 incident on face 196a of the substrate 196 into a set of diverging light beamlets 254' that exit from face 196b of the substrate 196 at a divergence angle.

[0320] The diffraction grating 198 can be designed to produce odd-numbered divergent optical beamlets 254' from a single collimated optical beam 250 or even-numbered divergent optical beamlets 254' from a single collimated optical beam 250. Importantly, when the collimated optical beam 250 intersects with the diffraction grating 198, beamlets are created at different diffraction orders. For example, as shown in Figure 67A, one diffraction grating 198' is designed to split the collimated optical beam 250 into five divergent optical beamlets 254' corresponding to five diffraction orders (-2, -1, 0, +1, +2), and each divergent optical beamlet 254' is separated at a separation angle θ sOnly is it separated from the adjacent diverging light beamlet 254'. As shown in Figure 67B, another diffraction grating 198'' is designed to split the collimated light beam 250 into four diverging light beamlets 254', each corresponding to four diffraction orders (-3, -1, +1, +3), and each diverging light beamlet 256' is separated at a separation angle 2θ s It is separated only from the adjacent diverging light beamlet 256'.

[0321] The diffraction grating 198 may be divided into either a one-dimensional array of diverging optical beamlets 254' or a two-dimensional (M×N) array of diverging optical beamlets 254'. In the embodiment illustrated in Figures 64-66, the diffraction grating divides the collimated optical beam 250 into a 4×4 array of diverging optical beamlets 254'. Naturally, the PPE192b can be designed to create smaller or larger arrays of diverging optical beamlets 254', such as a 1×2 array, a 2×1 array, a 2×2 array, a 3×3 array, a 5×5 array, and further, it can be designed to create non-square two-dimensional arrays of diverging optical beamlets 254', such as a 2×3 array, a 3×2 array, a 3×4 array, a 4×3 array, and so on.

[0322] Importantly, PPE192b applies angle-preserving extension to the collimated light beam 250. That is, PPE192b bends a set of diverging light beamlets 254' emanating from the surface 196b of the substrate 196 back to the original angle of the collimated light beam 250'. To achieve this objective, PPE192b includes a diffractive lens 200, in this embodiment, which refocuses the diverging light beamlets 254' back to the original angle of the collimated light beam 250' as an initial set of externally coupled light beamlets 256'. Although the diffractive lens 200 is shown as separate from the IC element 168, the function of the diffractive lens 200 can be incorporated into the IC element 168.

[0323] From the above, it can be understood that PPE192b pre-expands the effective entrance pupil of the collimated light beam 250 in two dimensions. In the same manner as described above with respect to Figures 34-36, the primary waveguide apparatus 170 further expands the pupil of the collimated light beam 250 in two dimensions. That is, the initial 4x4 array of externally coupled light beamlets 256' is input into the IC element 168 of the primary waveguide apparatus 170 as a 4x4 array of internally coupled light beamlets 252 (only 252(1)-252(4) are shown), as shown in Figures 64-66. This is then divided by the OPE element 186 into a 4x4 array of orthogonal light beamlets 254 (only 254(1)-254(4) are shown), which is further divided by the EPE element 188 into the final externally coupled light beamlet 256 that exits from the surface 180b of the waveguide 172 toward the eyes 52 of the end user 50. Of particular note is the separation angle θ in the embodiment of Figure 67A. s Alternatively, the separation angle 2θ in Figure 67B s The separation distance s between adjacent initial externally coupled light beamlets 256' at the intersection with lens 200 will be selected such that it is equal to the desired spacing of the final externally coupled light beamlets 256 emitting from the primary waveguide apparatus 170.

[0324] Referring here to Figures 68-73, yet another embodiment of the display subsystem 104 utilizes a conventional PE, comprising the waveguide device 170 shown in Figures 34-36, and a PPE192c which, like the PPE192a, pre-expands the effective exit pupil of the collimated light beam 250 that is optically coupled into the PPE192c in a two-dimensional manner, but unlike the PPE192a, takes the form of a prism rather than a waveguide.

[0325] As best shown in Figures 71-73, the PPE192c comprises, in the illustrated embodiment, an optically transparent prism body 202 having a rectangular parallelepiped shape with a first face 202a and a second face 202b, and a plurality of prism planes 204 disposed inside the prism body 202. The plurality of prism planes 204 comprises a set of first parallel prism planes 204a positioned at an oblique angle (in this case, 45 degrees) with respect to the first face 202a, and a set of second parallel prism planes 204b positioned at an oblique angle (in this case, 45 degrees) with respect to the second face 202b. In the illustrated embodiment, the first set of parallel prism planes 204a consists of two prism planes 202a(1) and 202a(2), and the second set of parallel prism planes 204b consists of two prism planes 202b(1) and 202b(2); however, in an alternative embodiment, each set of parallel prism planes 204 may consist of more than two prism planes.

[0326] The prism body 202 comprises prism sections 206a-202f, which are joined together to form the entire prism body 202. A prism plane 204a(1) is formed at the interface between prism sections 206a and 206b, a prism plane 204a(2) is formed at the interface between prism sections 206b and 206c, a prism plane 204b(1) is formed at the interface between prism sections 206d and 206e, and a prism plane 204b(2) is formed at the interface between prism sections 206e and 206f.

[0327] The prism plane 204 is configured to split the collimated light beam 250 incident on the first surface 202a of the prism body 202 into a set of initial externally coupled light beamlets 256' (in this case, a 2x2 array of light beamlets 256') that exit from the second surface 202b of the prism body 202.

[0328] To achieve this objective, the prism planes 204a(1) and 204b(1) are each formed from a semi-reflective coating, such as gold, aluminum, silver, nickel-chromium, chromium, or other metals; dielectrics such as oxides, fluorides, or sulfides; semiconductors such as silicon or germanium; and / or adhesives or glues with reflective properties, which can be placed between adjacent prism sections 206 via any preferred process such as physical vapor deposition (PVD), ion-assisted vapor deposition (IAD), or ion beam sputtering (IBS). The ratio of reflection to transmission of the semi-reflective coating may be selected or determined, at least partially, based on the thickness of the coating, or the semi-reflective coating may have multiple small perforations to control the ratio of reflection to transmission. Thus, the prism planes 204a(1) and 204b(1) will each split the light beam by reflecting a portion of the light beam and transmitting the rest. In contrast, the prism planes 204a(2) and 204b(2) are preferably formed from a fully reflective coating, which may be made of the same material as the semi-reflective coating. However, the thickness of the coating may be selected so that the prism planes 204a(2) and 204b(2) are fully reflective.

[0329] In alternative embodiments, adjacent prism sections 206 may be made of materials having different refractive indices, such that the prism planes 204 between the individual prism sections 206 are semi-reflective (for prism planes 204a(1) or 204b(1)) or perfectly reflective (for prism planes 204a(2) and 204b(2)) with respect to light incident on the semi-reflective interface below a critical angle. In either case, each prism plane 204 is preferably designed so as to preserve the angle of the light beam incident on the prism plane 204.

[0330] As best illustrated in Figure 72, the first set of prism planes 204a relays light along a first axis (horizontal or x-axis) and pre-extends the effective exit pupil of the light along a second axis (vertical or y-axis). In particular, the first set of prism planes 204a splits the collimated light beam 250 incident on the first surface 202a of the prism body 202 into two orthogonal light beamlets 254(1)' and 254(2)', and reflects these light beamlets 254' in a first direction toward the second set of prism planes 204b. In other words, a portion of the collimated light beam 250 is reflected by the prism plane 204a(1) as an orthogonal light beamlet 254(1)', and the remaining portion of the collimated light beam 250 is transmitted by the prism plane 204a(1) to the prism plane 204a(2) for reflection as an orthogonal light beamlet 254(2)'.

[0331] As best shown in Figure 73, the second set of prism planes 204b further pre-extends the effective exit pupil of light along the second axis (horizontal or x-axis). In particular, the second set of prism planes 204b splits each of the orthogonal light beamlets 254' into two initial externally coupled light beamlets 256', and reflects these initial externally coupled light beamlets 256' outward from the second surface 202b of the prism body 202 in a second direction perpendicular to the first direction, although the second direction may not be perpendicular to the first direction. That is, a portion of the orthogonal beamlet 254(1)' is reflected by the prism plane 204b(1) as the initial externally coupled beamlet 256(1)', and the remaining portion of the orthogonal beamlet 254(1)' is transmitted by the prism plane 204b(1) to the prism plane 204b(2) for reflection as the initial externally coupled beamlet 256(2)'. Similarly, a portion of the orthogonal beamlet 254(2)' is reflected by the prism plane 204b(1) as the initial externally coupled beamlet 256(3)', and the remaining portion of the orthogonal beamlet 254(2)' is transmitted by the prism plane 204b(1) to the prism plane 204b(2) for reflection as the initial externally coupled beamlet 256(4)'. Thus, a 2×2 array of the initial externally coupled beamlets 256' exits from the second surface 202b of the prism body 202.

[0332] From the above, it can be understood that PPE192c pre-extends the effective entrance pupil of the collimated light beam 250 in two dimensions. In the same manner as described above with respect to Figures 34-36, the primary waveguide apparatus 170 further extends the pupil of the collimated light beam 250 in two dimensions. That is, the initial externally coupled light beamlet 256' is input into the IC element 168 of the primary waveguide apparatus 170 as a 2x2 array of internally coupled light beamlets (only 252(1)-252(2) are shown), as shown in Figures 68-70, which is then divided by the OPE element 186 into a set of four orthogonal light beamlets (only 254(1)-254(2) are shown), which is further divided by the EPE element 188 into a final externally coupled light beamlet 256 that exits from the surface 180b of the waveguide 172 toward the eye 52 of the end user 50.

[0333] The distance d between the prism planes 204 is preferably selected such that the distance s between adjacent initial externally coupled light beamlets 256' is equal to the desired spacing of the final externally coupled light beamlets 256 emitting from the primary waveguide apparatus 170. In the illustrated embodiment, the prism planes 204 are oriented at an angle of 45 degrees with respect to the planes 202a and 202b of the prism body 202, and therefore the distance d is less than or equal to d = s * It can be expressed as a function of distance s, such as sin45°. The thickness of the waveguide 172 in the primary waveguide apparatus 170 can be a multiple of the distance d between the prism planes 204 in each set of parallel prism planes 204 of the PPE 192c (in this case, 2 × the distance d between the parallel prism planes 204) so ​​as to facilitate the internal filling of the final externally coupled optical beamlet 256.

[0334] As illustrated in Figures 74 and 75, it should be understood that a larger array of the initial externally coupled light beamlets 256' may be created by reducing the distance between the prism planes 204 in each set of parallel prism planes 204 of the PPE192c relative to the size of the prism body 202.

[0335] For example, as shown in Figure 74, the first set of prism planes 204a may split the collimating light beam 250 incident on the first surface 202a of the prism body 202 into three orthogonal light beamlets 254(1)'-254(3)', and reflect these light beamlets 254' toward the second set of prism planes 204b. That is, a portion of the collimating light beam 250 is reflected by the prism plane 204a(1) as an orthogonal light beamlet 254(1)', and the remaining portion of the collimating light beam 250 is transmitted by the prism plane 204a(1) to the prism plane 204a(2), which is repeatedly reflected between the prism planes 204a(1) and 204a(2), with some of it being transmitted back through the prism plane 204a(1) as orthogonal light beamlets 254(2)' and 254(3)'.

[0336] As shown in Figure 75, the second set of prism planes 204b divides each of the orthogonal light beamlets 254' into three initial externally coupled light beamlets 256', which are then reflected outwards from the second surface 202b of the prism body 202. Thus, a 3×3 array of initial externally coupled light beamlets 256' exits from the second surface 202b of the prism body 202. That is, a portion of each orthogonal beamlet 254 is reflected by the prism plane 204b(1) as the initial externally coupled beamlet 256(1)', and the remaining portion of this orthogonal beamlet 254' is transmitted by the prism plane 204b(1) to the prism plane 204b(2), which is repeatedly reflected between the prism planes 204b(1) and 204b(2), with some of it being transmitted back through the prism plane 204b(1) as the initial externally coupled beamlets 256(2)' and 256(3)'.

[0337] Again, the distance d between the prism planes 204 is preferably selected such that the distance between adjacent initial externally coupled light beamlets 256' is equal to the desired spacing of the final externally coupled light beamlets 256 emanating from the primary waveguide apparatus 170. In the illustrated embodiment, the prism planes 204 are oriented at an angle of 45 degrees with respect to the planes 202a, 202b of the prism body 202, and therefore the distance d is less than or equal to d = s * It can be expressed as a function of distance s, such as sin45°.

[0338] Therefore, for each orthogonal optical beamlet 254, three initial externally coupled optical beamlets 256' will be generated, thereby creating a 3x3 array of initial externally coupled optical beamlets 256' that exit from the second surface 202b of the prism body 202. Naturally, the PPE192c can be designed to create even larger arrays of initial externally coupled optical beamlets 256', such as a 4x4 array or a 5x5 array, by further reducing the distance between prism planes 204 within each set of parallel prism planes 204 of the PPE192c relative to the size of the prism body 202.

[0339] While PPE192c is described as generating a square array of initial externally coupled optical beamlets 256', PPE192c can also be designed to generate non-square arrays of initial externally coupled optical beamlets 256', such as 2×3 arrays, 3×2 arrays, etc., by making the distance between prism planes 204a(1) and 204a(2) different from the distance between prism planes 204b(1) and 204b(2). Furthermore, while PPE192c is described as creating a two-dimensional array of initial externally coupled optical beamlets 256', PPE192c can also be designed to create a one-dimensional array of initial externally coupled optical beamlets 256', such as 1×2 arrays, 1×3 arrays, etc., by designing PPE192c with only one set of parallel prism planes 204.

[0340] Furthermore, while PPE192c has been described as generating an initial externally coupled light beamlet 256' that exits the prism body 202 at an angle perpendicular to the surface 202b of the prism body 202, PPE192c can be designed so that the initial externally coupled light beamlet 256' exits the prism body 202 at an oblique angle to the surface 202b of the prism body 202 by changing the orientation of one or both of the set of prism planes 204 relative to the surface 202b of the prism body 202.

[0341] Referring here to Figures 76-79, yet another embodiment of the display subsystem 104' utilizes a conventional PE, comprising the waveguide device 170 shown in Figure 34-36, and a PPE192e, which takes the form of a prism, but unlike the PPE192c, it utilizes a hollow prism, as opposed to a solid prism, to one-dimensionally pre-extend the effective entrance pupil of the collimated light beam 250 that is optically coupled into the PPE192e.

[0342] As best shown in Figure 79, the PPE192e comprises an optically transparent hollow prism 208, which includes a first triangular prism section 210a and a second triangular prism section 210b. The prism sections 210a and 210b are spaced apart from each other, creating an open space 212 between them, one side of which is bounded by the prism plane 212a of prism section 210a and the other side by the prism plane 212b of prism section 210b, the prism planes 212a and 212b being parallel to each other. The first prism section 210a has a first surface 214a opposite to the prism plane 212a and a second surface 214b. The prism plane 212a is positioned at an oblique angle (in this case, 45 degrees) to the first and second surfaces 214a and 214b.

[0343] The prism plane 212 is configured to split the collimated light beam 250 incident on the first surface 202a of the prism section 210 into a set of initial light beamlets 256' (in this case, a 1 × 4 array of initial externally coupled light beamlets 256') that exit from the second surface 214b of the first prism section 210a. To achieve this objective, in the same manner that the prism plane 204 of the PPE192c described above is designed to be partially reflective or fully reflective, the first prism plane 212a is designed to be partially reflective, while the second prism plane 212b is designed to be fully reflective. Each prism plane 212 is preferably designed so as to preserve the angle of the light beam incident on the prism plane 212.

[0344] As best illustrated in Figure 79, the PPE192c pre-extends the effective exit pupil of light one-dimensionally along a first axis (horizontal or x-axis). In particular, the set of prism planes 212 splits the collimated light beam 250 into four initial externally coupled light beamlets 256', which are reflected outward from the second surface 214b of the prism section 210b. Thus, a 1×4 array of initial externally coupled light beamlets 256' exits from the second surface 214b of the prism body 210. That is, a portion of the collimated light beam 250 is reflected by the prism plane 212a as the initial externally coupled light beamlet 256(1)', and the remainder of the collimated light beam 250 is transmitted to the prism plane 212a by the prism plane 212b, which is repeatedly reflected between the prism planes 212a and 212b, with some of it being transmitted back through the prism plane 212a as the initial externally coupled light beamlet 256(2)'-256(4)'. Naturally, the PPE192e can be designed to create smaller or larger one-dimensional arrays of the initial externally coupled light beamlets 256', such as 1×2 arrays, 1×3 arrays, 1×5 arrays, etc., by decreasing or increasing the distance between the prism planes 212 relative to the size of the prism 208.

[0345] From the above, it can be understood that the PPE192e pre-extends the effective entrance pupil of the collimated light beam 250 in one dimension. In the same manner as described above with respect to Figures 34-36, the primary waveguide apparatus 170 further extends the pupil of the collimated light beam 250 in two dimensions. That is, the initial externally coupled light beamlet 256' is input into the IC element 168 of the primary waveguide apparatus 170 as a 1×4 array of internally coupled light beamlets 252(1)-252(4), as shown in Figures 76-78, which is then divided by the OPE element 186 into a 1×4 array of orthogonal light beamlets 254(1)-254(4), which is further divided by the EPE element 188 into the final externally coupled light beamlet 256 that exits from the surface 180b of the waveguide 172 toward the eye 52 of the end user 50.

[0346] The distance d between the prism planes 212 is preferably selected such that the distance s between adjacent initial externally coupled light beamlets 256' is equal to the desired spacing of the final externally coupled light beamlets 256 emitting from the primary waveguide apparatus 170. In the illustrated embodiment, the prism planes 212 are oriented at an angle of 45 degrees with respect to the planes 214a, 214b of the prism body 202, and therefore the distance d is less than or equal to d = s * It can be expressed as a function of distance s, such as sin45°. Importantly, the thickness of the waveguide 172 within the primary waveguide apparatus 170 will be a multiple of the distance d between the prism planes 212 of the PPE 192e (in this case, 2 × the distance d between the prism planes 212) so as to facilitate the internal filling of the final externally coupled optical beamlet 256.

[0347] It should be understood that the distance d between the prism planes 212 is set simply by positioning the prism planes 212 relative to each other, and therefore the spacing between the final externally coupled optical beamlets 256 can be set arbitrarily without concerns regarding manufacturing limits. That is, since the PPE192e does not utilize an optical substrate between the prism planes 212, but rather utilizes the cavity between the prism planes 212, there is no need to be concerned about limits related to the minimum thickness of such an optical substrate.

[0348] Referring here to Figures 80-89, several embodiments of the display subsystem 104 utilize conventional PEs, comprising the waveguide device 170 shown in Figures 34-36 and a PPE 192f, which in the illustrated embodiments takes the form of a multilayer miniature waveguide device 220 mounted on an IC element 168.

[0349] The miniature waveguide apparatus 220 has a size proportional to the size of the IC element 168 of the primary waveguide apparatus 170. The miniature waveguide apparatus 220 comprises a plurality of waveguide assemblies 222, in this case an upper waveguide assembly 222a and a bottom waveguide assembly 222b. Each waveguide assembly 222 is configured to divide one or more collimated beams or beamlets (collimated light beam 250 in the bottom waveguide assembly 222b and externally coupled light beamlet 256' in the upper waveguide assembly 222b) into a two-dimensional array (in this case a 4x4 array) of externally coupled light beamlets 256', as will be described in more detail below.

[0350] In a particular miniature waveguide apparatus 220 described herein, as shown in Figure 83, the bottom waveguide assembly 222b functions to split a single collimated light beam 250 into a two-dimensional array of externally coupled light beamlets 256', while the top waveguide assembly 222a functions to split the two-dimensional array of externally coupled light beamlets 256' from the bottom waveguide assembly 222b into a two-dimensional array of multiple externally coupled light beamlets 256''. To achieve this objective, the top waveguide assembly 222a and the bottom waveguide assembly 222b are positioned relative to each other such that the top waveguide assembly 222a receives the externally coupled light beamlets 256' from the bottom waveguide assembly 222b. For example, as may be shown below, the top surface 224a of the bottom waveguide assembly 222b is attached to the bottom surface 224b of the top waveguide assembly 222a.

[0351] Referring further to Figures 84 and 85A-85B, each waveguide assembly 222 comprises a pair of orthogonal waveguide units, which consist of an upper orthogonal waveguide unit 226a and a bottom orthogonal waveguide unit 226b, with the bottom surface 228b of the upper orthogonal waveguide unit 226a attached to the upper surface 228a of the bottom orthogonal waveguide unit 226b. The orthogonal waveguide units 226 are identical to each other, differing only in that they are oriented orthogonally to each other. Each orthogonal waveguide unit 226 comprises a planar optical waveguide 230 in the form of a single, integrated substrate or plane of an optically transparent material (as described above with respect to waveguide 172). The planar optical waveguides 230 of the individual orthogonal waveguide units 226 are of the same size and have upper and bottom surfaces 230a and 230b, respectively. Each orthogonal waveguide unit 226 further comprises an IC element 232 associated with (e.g., positioned on) the bottom surface 230b of an individual planar optical waveguide 230, and an EPE 234 associated with (e.g., positioned on) the top surface 230a of the planar optical waveguide 230.

[0352] Each IC element 232 is configured to internally couple one or more optical beams or beamlets into individual planar optical waveguides 230 (236a in the case of the upper orthogonal waveguide unit 226a, 236b in the case of the lower orthogonal waveguide unit 226b) for propagation along the internal reflective optical path via TIR, thereby repeatedly intersecting with the EPE element 234. In the same manner as described above with respect to the EPE element 188 of the primary waveguide apparatus 170, the EPE element 234 has a relatively low diffraction efficiency (e.g., less than 50%) such that at each intersection with the EPE element 234, a portion of each optical beam or beamlet (e.g., more than 90%) continues to propagate along the individual internal reflective optical path 236, and the remainder of each optical beam or beamlet is diffracted as an initial externally coupled optical beamlet 256' that exits from the upper surface 230a of the individual planar optical waveguide 230. In the illustrated embodiment, the sizes of the IC element 232 and the EPE element 234 are equal to each other and proportional to the size of the individual planar optical waveguide 230, to maximize pupil dilation of the collimated light beam 250, while also facilitating the internal coupling of the two-dimensional array of externally coupled light beamlets 256' from the bottom orthogonal waveguide unit 226b to the upper orthogonal waveguide unit 226a.

[0353] The IC elements 232 of the orthogonal waveguide unit 226 are oriented orthogonally to each other so that each optical beam or beamlet (250 or 256'), which is internally coupled into the bottom surface 224b of the individual waveguide assembly 222, is divided into a two-dimensional array of initial externally coupled optical beamlets 256' (or 256'') that exit from the top surface 224a of the waveguide assembly 222, as shown in Figure 84.

[0354] In particular, the IC elements 232 of each waveguide assembly 222 are oriented orthogonal to each other such that the IC element 232 associated with the bottom orthogonal waveguide unit 226b internally couples light for propagation along an internal reflective optical path parallel to the first axis 262 via TIR (in this case, along the y-axis), and the light is extended along the first axis 262 by the corresponding EPE element 234 (see Figure 85B), while the IC elements 232 associated with the upper orthogonal waveguide unit 226a internally couple each light beam or beamlet for propagation along an internal reflective optical path parallel to the second axis 264 perpendicular to the first axis 264 via TIR (in this case, along the x-axis), and the light is extended along its second axis 264 by the corresponding EPE element 234 (see Figure 85A).

[0355] As briefly discussed above with respect to Figure 83, the bottom surface 224b of the upper waveguide assembly 222a is attached to the upper surface 224a of the bottom waveguide assembly 222b so that the output of the bottom waveguide assembly 222a is provided as an input to the upper waveguide assembly 222a, thereby generating multiple arrays of externally coupled optical beamlets 256'' from a single collimated optical beam 250.

[0356] In particular, referring further to Figures 86A and 86B, the bottom waveguide assembly 222b receives the collimated light beam 250 from the collimation element 166 and emits it from the upper surface 224a of the bottom waveguide assembly 222b, splitting the collimated light beam 250 into a two-dimensional array of initial externally coupled light beamlets 256'.

[0357] Specifically, the IC element 224 associated with the bottom orthogonal waveguide unit 226b of the bottom waveguide assembly 222b optically couples the collimated light beam 250 as an initial internally coupled light beam 252' for propagation in the individual planar optical waveguide 230 along a first internally reflected optical path parallel to the axis 262 (y-axis) via TIR, and the EPE element 226 associated with the bottom orthogonal waveguide unit 226b of the bottom waveguide assembly 222b splits the collimated light beam 250 into a one-dimensional array of initial externally coupled light beamlets 256' that exit from the upper surface 228a of the individual bottom orthogonal waveguide unit 226b.

[0358] Subsequently, the IC element 224 associated with the upper orthogonal waveguide unit 226a of the bottom waveguide assembly 222b optically couples a one-dimensional array of initial externally coupled optical beamlets 256' as an initial orthogonal optical beamlet 254' for propagation within a separate planar optical waveguide 230 along a second internal reflective optical path parallel to a separate axis 264 (x-axis) orthogonal to a first internal reflective optical path parallel to axis 262 (y-axis) via TIR, and the EPE element 226 associated with the upper orthogonal waveguide unit 226a of the bottom waveguide assembly 222b splits the initial orthogonal optical beamlet 254' into a two-dimensional array of initial externally coupled optical beamlets 256' that exit from the upper surface 228a of the separate upper orthogonal waveguide unit 226a.

[0359] The upper waveguide assembly 222a receives a two-dimensional array of the initial externally coupled light beamlet 256' from the bottom waveguide assembly 222b, and divides this two-dimensional array of the initial externally coupled light beamlet 256' into multiple two-dimensional arrays of intermediate externally coupled light beamlets 256'' that are emitted from the upper surface 224a of the upper waveguide assembly 222a.

[0360] Specifically, the IC element 224 associated with the bottom orthogonal waveguide unit 226b of the upper waveguide assembly 222a optically couples a two-dimensional array of initial externally coupled optical beamlets 256' as an intermediate set of internally coupled optical beams 252'' for propagation within the individual planar optical waveguide 230 along a first internally reflected optical path parallel to axis 262 (y-axis) via TIR, and the EPE element 226 associated with the bottom orthogonal waveguide unit 226b of the upper waveguide assembly 222a divides the intermediate set 252'' of internally coupled optical beamlets into a two-dimensional array of intermediate externally coupled optical beamlets 256'' of the initial externally coupled optical beamlets 256' that exit from the upper surface 228a of the individual bottom orthogonal waveguide unit 226b.

[0361] Subsequently, the IC element 224 associated with the upper orthogonal waveguide unit 226a of the upper waveguide assembly 222a optically couples a two-dimensional array of intermediate externally coupled optical beamlets 256'' as an intermediate orthogonal optical beamlet 254'' for propagation within a separate planar optical waveguide 230 along a separate second internal reflective optical path 264 (x-axis) perpendicular to a first internal reflective optical path parallel to axis 262 (y-axis) via TIR, and the EPE element 226 associated with the upper orthogonal waveguide unit 226a of the upper waveguide assembly 222a splits the intermediate orthogonal optical beamlet 254'' into a two-dimensional array of intermediate externally coupled optical beamlets 256'' that exit from the upper surface 228a of the separate upper orthogonal waveguide unit 226a.

[0362] Therefore, the bottom waveguide assembly 222b divides the collimated light beam 250 into a two-dimensional array of initial externally coupled light beamlets 256', and the upper waveguide assembly 222a divides the two-dimensional array of externally coupled light beamlets 256' into several two-dimensional arrays of intermediate externally coupled light beamlets 256''. Each of the two-dimensional arrays of initial externally coupled light beamlets 256' and the two-dimensional arrays of intermediate externally coupled light beamlets 256'' has an inter-beamlet spacing s1, and the two-dimensional array of intermediate externally coupled light beamlets 256'' has an inter-array spacing s2 that is different from the inter-beamlet spacing s1 of the two-dimensional arrays of initial externally coupled light beamlets 256' and intermediate externally coupled light beamlets 256'' (see, for example, Figures 89A and 89B). The array spacing s2 and the beamlet spacing s1 are non-multiples of each other, as will be described in more detail below, so that the optical beamlets 256'' are dispersed in a manner that maximizes the density of the internal filling of the exit pupil of the PPE192f, and thus the exit pupil of the display screen 110.

[0363] Of particular note is that the beamlet spacing s1 is determined by the individual thickness of the waveguide 230 of the bottom waveguide assembly 222b. Similarly, the array spacing s2 is determined by the individual thickness of the waveguide 240 of the upper waveguide assembly 222a. The thickness of the waveguide 230 of the upper and bottom waveguide assemblies 222 may be strategically selected based on the diameter of the collimated light beam 250. In some embodiments, the beamlet spacing s1 and the array spacing s2 are different from each other, but each is a multiple of the diameter of the collimated light beam 250, which can maximize the internal filling of the exit pupil of the PPE192f.

[0364] Therefore, the beamlet spacing s1 can be a multiple ("m") of the diameter ("d") of the collimated light beam 250, such that s1 = m × d. Using this value of s1, the array spacing s2 can be described by s2 = s1 + d. That is, s1 and s2 can be consecutive multiples of the diameter of the collimated light beam 250, such that s2 = (m + 1) × d. For example, the beamlet spacing s1 can be 3 times the diameter of the collimated light beam 250. Using this value of s1, the array spacing s2 can be 4 times the diameter of the collimated light beam 250. As illustrated in the illustrated embodiment below, this results in the array spacing s2 being 1.33 × beamlet spacing s1.

[0365] The first and second planar optical waveguide assemblies 222a and 222b have unequal thicknesses t1 and t2, respectively, as shown in Figure 83, and such thicknesses are determined by the thickness of the individual planar optical waveguides 230 incorporated into the individual orthogonal waveguide units 226a and 226b of the optical waveguide assemblies 222a and 222b. For example, as shown in Figures 86A and 86B, the thickness of the planar optical waveguide 230 incorporated into the upper planar optical waveguide assembly 222a exceeds the thickness of the planar optical waveguide 230 incorporated into the lower planar optical waveguide assembly 222b. Preferably, the spacings s1, s2 between the first and second beamlets, and therefore the thicknesses t1, t2 of the first and second planar optical waveguide assemblies 222a, 222b, are not multiples of each other, ensuring that multiple arrays of intermediate externally coupled optical beamlets 252'' are generated from a single array of initial externally coupled optical beamlets 252''.

[0366] As briefly discussed above, the bottom waveguide assembly 222b splits the collimated light beam 250 into a two-dimensional array of initial externally coupled light beamlets 256', and the top waveguide assembly 222a splits the two-dimensional array of externally coupled light beamlets 256' into several two-dimensional arrays of intermediate externally coupled light beamlets 256''. In other words, the bottom waveguide assembly 222b and the top waveguide assembly 222a each generate two transfer functions that are convolved to produce a desired pattern of intermediate externally coupled light beamlets 252''.

[0367] For example, as shown in Figure 87A, the bottom waveguide assembly 222b (as the first expander) is, [ka] The first transfer function h1 is such that, where x is the optical input (a beam of light with diameter a) into the bottom waveguide assembly 222b and y is the optical output from the bottom waveguide assembly 222b. In this embodiment, the transfer function h1 results in a 4x4 array of light beamlets of diameter a, spaced apart from each other by a distance of 3a. Similarly, as shown in Figure 87B, the upper waveguide assembly 222a (as a second expander) is, [ka] The second transfer function h2 is such that x is the optical input (a beam of light with diameter a) into the upper waveguide assembly 222a, and y is the optical output from the lower waveguide assembly 222a. In this embodiment, the transfer function h2 results in a 4x4 array of light beamlets of diameter a, spaced 4a apart from each other. As shown in Figure 87C, the transfer functions h1 and h2 are [ka] It can be convolved in such a way. Thus, the collimated light beam 250 (as optical input x) can be input into the bottom waveguide assembly 222b, which applies the transfer function h1 to the collimated light beam 250, thereby generating a two-dimensional array of intermediate externally coupled light beamlets 256' having the beam pattern illustrated in Figure 87A. The two-dimensional array of intermediate externally coupled light beamlets 256' output by the bottom waveguide assembly 222b can be input into the top waveguide assembly 222a, which applies the transfer function h2 to the two-dimensional array of intermediate externally coupled light beamlets 256', thereby generating multiple two-dimensional arrays of intermediate externally coupled light beamlets 256'', the synthesis of which creates the light beamlet pattern illustrated in Figure 87C.

[0368] Referring here to Figures 88 and 89A–89H, the generation of multiple intermediate externally coupled optical beamlets 256'' increases rapidly as the two-dimensional array of initial externally coupled optical beamlets 256'' propagates through the upper optical waveguide assembly 222a. As a result, the density of intermediate externally coupled optical beamlets 256'' gradually increases from left to right and from top to bottom across the upper surface 224a of the upper planar optical waveguide assembly 222a through several generation of beam splitting until an N×N array is generated that is completely filled with externally coupled optical beamlets 258'', in this case a 10×10 array of externally coupled optical beamlets 258'' (shown in Figure 89H). In the illustrated embodiment, seven generation of beam splitting, which generate 16 two-dimensional arrays (in this case a 4×4 array) of intermediate externally coupled optical beamlets 256(1)''-256(16)'', results in a densely saturated 10×10 array of externally coupled optical beamlets 258''. As shown therein, the beamlet designated "0" is a two-dimensional array of the initial externally coupled optical beamlet 256', while the beamlets designated "1" to "16" are, respectively, two-dimensional arrays of 16 intermediate externally coupled optical beamlets 256(1)''-256(16)''. Notably, a letter scheme is used in Figures 89A-89H to facilitate understanding of the initial externally coupled optical beamlet 256' to which the intermediate externally coupled optical beamlet 256'' corresponds. Under this letter scheme, each beamlet in the 4x4 array of beamlets 256', output by the bottom waveguide assembly 222b (first expander) illustrated in Figure 87A and input into the upper waveguide assembly 222a (second expander) illustrated in Figure 87B, corresponds to a different alphabetical letter ("A" to "P"). Thus, each beamlet 256'' output by the upper waveguide assembly 222a (second expander) can be considered to correspond to both the specific two-dimensional array of intermediate externally coupled optical beamlets 256(1)''-256(16)'' and the associated beamlet group ("A"-"P").

[0369] In particular, the two-dimensional array of the intermediate externally coupled beamlet 256(1)'' is generated directly from the two-dimensional array of the initial externally coupled beamlet 256' (see Figure 89A). In the first generation, the two-dimensional array ...

Claims

1. A virtual image generation system, wherein the virtual image generation system is A planar optical waveguide having opposing first and second surfaces, An internal coupling (IC) element configured to optically couple a collimated light beam from an image projection assembly into the planar optical waveguide as an internally coupled light beam, A first orthogonal pupil expansion (OPE) element associated with the first surface of the plane optical waveguide, the first orthogonal pupil expansion (OPE) element for splitting the internally coupled light beam into a first set of orthogonal light beamlets, A second orthogonal pupil expansion (OPE) element associated with the second surface of the plane optical waveguide, the second orthogonal pupil expansion (OPE) element for splitting the internally coupled light beam into a second set of orthogonal light beamlets, An exit pupil expansion (EPE) element associated with the plane optical waveguide, wherein the exit pupil expansion (EPE) element divides the first set of orthogonal beamlets and the second set of orthogonal beamlets into an array of externally coupled beamlets exiting the plane optical waveguide. Equipped with, A virtual image generation system in which the array of externally coupled light beamlets includes externally coupled light beamlets generated from a first set of orthogonal light beamlets and externally coupled light beamlets generated from a second set of orthogonal light beamlets alternating with the externally coupled light beamlets generated from the first set of orthogonal light beamlets.

2. The virtual image generation system according to claim 1, wherein the planar optical waveguide is formed from a single, integrated substrate.

3. The virtual image generation system according to claim 1, wherein the first OPE element is arranged on the first surface of the planar optical waveguide, and the second OPE element is arranged on the second surface of the planar optical waveguide.

4. The virtual image generation system according to claim 1, wherein the EPE element is arranged on one of the first and second surfaces of the planar optical waveguide.

5. The virtual image generation system according to claim 1, wherein the IC element is configured to optically couple the collimated light beam from the image projection assembly as the internally coupled light beam for propagation in the planar optical waveguide along a first optical path that alternately intersects the first OPE element and the second OPE element via total internal reflection (TIR), thereby deflecting a portion of the internally coupled light beam as each of the first set of orthogonal light beamlets and the second set of orthogonal light beamlets propagating in the planar optical waveguide along a second parallel optical path via TIR.

6. The virtual image generation system according to claim 5, wherein the second parallel optical path is orthogonal to the first optical path.

7. The virtual image generation system according to claim 1, wherein the first set of orthogonal beamlets and the second set of orthogonal beamlets intersect with the EPE element, thereby deflecting portions of the first set of orthogonal beamlets and the second set of orthogonal beamlets as the array of externally coupled beamlets out of the planar optical waveguide.

8. The virtual image generation system according to claim 1, wherein the EPE element is configured to impart a convex wavefront profile onto the array of externally coupled light beamlets emitted from the plane optical waveguide, thereby causing the array of externally coupled light beamlets to become an array of diverging light beamlets, thereby generating an image on a given focal plane.

9. The virtual image generation system according to claim 1, wherein the collimated light beam defines an entrance pupil, and the array of the externally coupled light beamlets defines an exit pupil that is larger than the entrance pupil.

10. The virtual image generation system according to claim 9, wherein the exit pupil is at least 10 times larger than the entrance pupil.

11. The virtual image generation system according to claim 9, wherein the exit pupil is at least 100 times larger than the entrance pupil.

12. The virtual image generation system according to claim 1, wherein each of the IC element, the OPE element, and the EPE element is diffractive.

13. The virtual image generation system according to claim 1, wherein the array of externally coupled light beamlets is a two-dimensional externally coupled light beamlet array.

14. The virtual image generation system according to claim 1, further comprising the image projection assembly.

15. The virtual image generation system according to claim 14, wherein the image projection assembly comprises a scanning device configured to scan the collimated light beam.

Images