Overlapping waveguide system

Abstract

A waveguide system for a near-eye display may include a first waveguide section and a second waveguide section, with the waveguide sections overlapping. The waveguide sections may be substantially parallel to each other or may be at some nonzero angle relative to one another. The waveguide sections may include a pair of sets of partially reflecting surfaces configured to expand light in a pair of different dimensions. One or more reflecting surfaces, possibly in combination with a prism, may be used to direct light from the first waveguide section to the second waveguide section.

Description

OVERLAPPING WAVEGUIDE SYSTEMFIELD

[0001] The present disclosure relates to the field of near eye display systems such as head-mounted displays, such as virtual reality (VR) displays. More specifically, the present disclosure relates to a compact waveguide system designed for near eye displays (NEDs).BACKGROUND

[0002] Consumer demands for improved human-computer interfaces have led to an increased interest in high-quality image head-mounted displays (HMDs) or near-eye displays (NED), commonly known as smart glasses. These devices can provide virtual reality (VR) or augmented reality (AR) experiences, enhancing the way users interact with digital content and their surrounding environment.

[0003] Consumers are seeking better image quality, immersive experiences, and greater comfort when using HMDs. They expect displays with high resolution, vibrant colors, and minimal distortion to create a realistic and enjoyable viewing experience. Additionally, comfort is a crucial factor since users often wear these devices for extended periods. Consumers desire lightweight, sleek designs that are less obtrusive and more convenient to wear in various scenarios. Smaller devices also offer improved portability, making them easier to carry and use in different environments. As such, there is a growing demand for higher performing yet smaller and more compact HMDs.

[0004] A critical element in traditional near-eye display systems is the waveguide. It is a device that guides light from a system image projector to the user's eyes. Waveguides rely on total internal reflection along the major surfaces within the device to propagate light. There are inherent limitations in miniaturizing waveguides, which in turn restricts the miniaturization of head-mounted displays. For example, conventional features that would assist more efficient illumination of the waveguides tend to increase their size. In another example, conventional features that would assist in miniaturization of waveguides tend to reduce image quality or aesthetic appeal of the near-eye display system.

[0005] Therefore, there is a demand for innovative compact illuminations systems including compact waveguide systems that would contribute to compactness of the NED.SUMMARY

[0006] A waveguide system for a near-eye display may include a first waveguide section (HLOE) and a second waveguide section (LOE), with the waveguide sections overlapping. The waveguide sections may be substantially parallel to each other or may be at some nonzero angle relative to one another. The waveguide sections may include a pair of sets of partially reflecting surfaces configured to expand light in a pair of different dimensions. One or more reflecting surfaces, possibly in combination with a prism, may be used to direct light from the first waveguide section to the second waveguide section.

[0007] According to an aspect, a waveguide system for a near-eye display, includes: a first waveguide section having an aperture through which light beams corresponding to an image from an image projector enter the waveguide system, one or more first optical elements configured to couple light corresponding to the image so as to expand the aperture in a first dimension; a second waveguide section configured to receive light from the first waveguide section and including one or more second optical elements configured to couple out light corresponding to the image so as to expand the aperture in a second dimension nonparallel to the first dimension; and one or more reflectors that reflect the light corresponding to the image from the first waveguide section towards the second waveguide section; wherein the second waveguide section overlaps the first waveguide section in a direction of light output from the second waveguide section.

[0008] According to an embodiment of any paragraph(s) of this summary, the one or more reflectors include one or more folding mirrors.

[0009] According to an embodiment of any paragraph(s) of this summary, the one or more first optical elements and the one or more second optical elements include partial reflectors.

[0010] According to an embodiment of any paragraph(s) of this summary, the first dimension is perpendicular to the second dimension.

[0011] According to an embodiment of any paragraph(s) of this summary, the first waveguide section and the second waveguide section are substantially parallel to one another.

[0012] According to an embodiment of any paragraph(s) of this summary, the first waveguide section and the second waveguide section are at an angle of 1 to 89 degrees to one another.

[0013] According to an embodiment of any paragraph(s) of this summary, the first waveguide section and the second waveguide section define a gap therebetween.

[0014] According to an embodiment of any paragraph(s) of this summary, the gap is an air gap.

[0015] According to an embodiment of any paragraph(s) of this summary, the gap is filled at least in part by a low-refractive-index adhesive.

[0016] According to an embodiment of any paragraph(s) of this summary, the aperture is at a first end of the first waveguide section, and wherein at least one of the one or more reflectors is at a second end of the first waveguide section that is opposite the first end.

[0017] According to an embodiment of any paragraph(s) of this summary, the one or more reflectors include a reflector in the first waveguide section.

[0018] According to an embodiment of any paragraph(s) of this summary, the one or more reflectors include a reflector in the second waveguide section.

[0019] According to an embodiment of any paragraph(s) of this summary, the one or more reflectors include a first reflector in the first waveguide, and a second reflector in the second waveguide.

[0020] According to an embodiment of any paragraph(s) of this summary, the waveguide system further includes a prism optically coupling the first waveguide section and the second waveguide section.

[0021] According to an embodiment of any paragraph(s) of this summary, the prism cooperates with the one more reflectors to turn light from a first propagation direction in the first waveguide section, toward the prism, to a second propagation direction in the second waveguide section, away from the prism.

[0022] According to an embodiment of any paragraph(s) of this summary, the waveguide system is in combination with an image projector operatively coupled to the aperture.

[0023] According to an embodiment of any paragraph(s) of this summary, the waveguide system includes a polarizer between the first waveguide section and the second waveguide section.

[0024] According to an embodiment of any paragraph(s) of this summary, the waveguide system includes a waveplate between the first waveguide section and the second waveguide section.

[0025] According to an embodiment of any paragraph(s) of this summary, the waveguide system is in combination with a controller coupled to the image projector, to drive the image projector.

[0026] According to an embodiment of any paragraph(s) of this summary, the waveguide system is part of a virtual reality system.

[0027] According to an embodiment of any paragraph(s) of this summary, the waveguide system is part of virtual reality glasses.

[0028] According to another aspect, a waveguide system includes: a first waveguide section having an aperture at through which light beams corresponding to an image from an image projector enter the waveguide system; one or more first optical elements in the first waveguide section; a first coupling prism in the first waveguide section, wherein the first coupling prism has a reflecting surface at substantially 45 degrees relative to major surfaces of the first waveguide surface; a second waveguide section configured to receive light from the first waveguide section; one or more second optical elements configured to couple out light corresponding to the image; and a second coupling prism in the second waveguide section, wherein the second coupling prism has a reflecting surface at substantially 45 degrees relative to major surfaces of the second waveguide surface; wherein the first and second coupling prisms in combination turn and direct light from the first waveguide section into the second waveguide section; and wherein the secondwaveguide section is substantially parallel to the first waveguide section in a direction of light output from the second waveguide section.

[0029] According to an embodiment of any paragraph(s) of this summary, the first coupling prism and the second coupling prism have a higher refractive index than other portions of the first waveguide section and the second waveguide section.

[0030] According to an embodiment of any paragraph(s) of this summary, the one or more first optical elements include an optical mixer.

[0031] According to an embodiment of any paragraph(s) of this summary, the one or more second optical elements include an optical mixer.

[0032] According to an embodiment of any paragraph(s) of this summary, the one or more second optical elements include one or more partially reflective surfaces.

[0033] According to an embodiment of any paragraph(s) of this summary, the one or more partially reflective surfaces include partially reflective surfaces parallel to one another and oblique to the second major surfaces.

[0034] According to an embodiment of any paragraph(s) of this summary, the one or more partially reflective surfaces include partially reflective surfaces parallel to one another and normal to the second major surfaces.

[0035] According to an embodiment of any paragraph(s) of this summary, the system further includes a layer of low-refractive-index material between the coupling prisms, the low-refractive-index material having an index of refraction lower than other portions of the first waveguide section and the second waveguide section.

[0036] According to an embodiment of any paragraph(s) of this summary, the system further includes layers of low-refractive-index material between respective of the coupling prisms, and other portions of the first waveguide section and the second waveguide section, the low-refractive-index material having an index of refraction lower than the other portions of the first waveguide section and the second waveguide section.

[0037] According to an embodiment of any paragraph(s) of this summary, the low- refractive index material includes an optical adhesive.

[0038] According to an embodiment of any paragraph(s) of this summary, the system further includes a third waveguide section substantially parallel to the first waveguide section and the second waveguide section, with light passing from the second waveguide section to the third waveguide section through an additional coupling prism of the second waveguide section, and a third coupling prism of the third waveguide section.

[0039] According to an embodiment of any paragraph(s) of this summary, the additional coupling prism has a reflecting surface at substantially 45 degrees relative to the major surfaces of the second waveguide surface; and the third coupling prism has a reflecting surface at substantially 45 degrees relative to major surfaces of the third waveguide surface.

[0040] According to an embodiment of any paragraph(s) of this summary, the third waveguide surface includes one or more third optical elements.

[0041] According to an embodiment of any paragraph(s) of this summary, the one or more third optical elements include an optical mixer.

[0042] According to an embodiment of any paragraph(s) of this summary, the one or more third optical elements include one or more partially reflective surfaces.

[0043] According to an embodiment of any paragraph(s) of this summary, the one or more partially reflective surfaces include partially reflective surfaces parallel to one another and oblique to the second major surfaces.

[0044] According to an embodiment of any paragraph(s) of this summary, the one or more partially reflective surfaces include partially reflective surfaces parallel to one another and normal to the second major surfaces.

[0045] According to an embodiment of any paragraph(s) of this summary, the one or more third optical elements include a diffractive grating that directs light out of the third waveguide section.

[0046] According to yet another aspect, a method of forming a waveguide system includes: attaching mirror stacks to opposite respective ends of a mixer stack, to form a combined stack; cutting the combined stack to produce first and second waveguide sections, each of the waveguide sections including a mixer from the mixer stack, and a pairof mirrors from the mirror stacks at opposite respective ends of the mixer; and adhesively attaching the waveguide sections together, with the waveguide sections configured such that the mirrors of the waveguide sections cooperate to turn and direct light from the first waveguide section to the second waveguide sections.

[0047] According to an embodiment of any paragraph(s) of this summary, the attaching includes attaching with optical adhesive.

[0048] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate various example systems, methods, and so on, that illustrate various example embodiments of aspects of the invention. It will be appreciated that the illustrated element boundaries (e.g., boxes, groups of boxes, or other shapes) in the figures represent one example of the boundaries. One of ordinary skill in the art will appreciate that one element may be designed as multiple elements or that multiple elements may be designed as one element. An element shown as an internal component of another element may be implemented as an external component and vice versa. Furthermore, elements may not be drawn to scale.BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Fig. 1 is a side view of a prior art folding optical device.

[0050] Fig. 2 shows schematically the concept of a two-dimensional aperture expansion (aperture multiplication) for a near-eye display (NED).

[0051] Fig. 3 illustrates a novel waveguide system for a NED.

[0052] Fig. 4 illustrates a novel waveguide system for a NED.

[0053] Fig. 5 illustrates a novel waveguide system for a NED.

[0054] Fig. 6 illustrates a waveguide system embedded in standard eyeglasses frame to form a virtual reality (VR) system.

[0055] Fig. 7 illustrates a novel waveguide system for a NED.

[0056] Fig. 8 illustrates a novel waveguide system for a NED.

[0057] Fig. 9 illustrates a novel waveguide system for a NED.

[0058] Fig. 10 illustrates a novel waveguide system for a NED.

[0059] Fig. 1 1 illustrates a first step in a novel method of producing a waveguide system.

[0060] Fig. 12 illustrates a second step in a novel method of producing a waveguide system.

[0061] Fig. 13 illustrates a third step in a novel method of producing a waveguide system.DETAILED DESCRIPTION

[0062] Certain embodiments of the present invention provide an optical system and a light projecting system for achieving optical aperture expansion for the purpose of, for example, head-mounted displays (HMDs) or near-eye displays, commonly known as smart glasses, which may be virtual reality or augmented reality displays. Consumer demands for better and more comfortable human computer interfaces have stimulated demand for better image quality and for smaller devices.

[0063] Fig. 1 illustrates a conventional prior art folding optics arrangement, wherein the substrate 2 is illuminated by a display source 4. The display is collimated by a collimating optics 6, e.g., a lens. The light from the display source 4 is coupled into substrate 2 by a first reflecting surface 8, in such a way that the main ray 11 is parallel to the substrate plane. A second reflecting surface 12 couples the light out of the substrate and into the eye of a viewer 14. Despite the compactness of this configuration, this configuration suffers significant drawbacks. In particular, only a very limited field of view (FOV) can be achieved.

[0064] An alternative optical arrangement, a two-dimensional waveguide system 20, is conceptually illustrated in Fig. 2, in combination with a projection optical device (POD) 22, also referred to herein as a compact image projector. The waveguide system 20 and the POD 22 are parts of a display 23. The POD 22 is optically coupled to the waveguide system 20 so as to inject an image into waveguide system (interchangeably referred to as “substrate” or “slab”) 20 within which the image light is trapped in one dimension by internal reflection at a set of mutually-parallel planar external surfaces.

[0065] Optical aperture expansion is achieved within waveguide system 20 by one ormore arrangements for progressively redirecting the image illumination, typically employing a set of partially-reflecting surfaces (interchangeably referred to as “facets”) that may be parallel to each other and inclined obliquely to the direction of propagation of the image light, with each successive facet deflecting a proportion of the image light into a deflected direction. As illustrated in Fig. 2, two-dimensional aperture expansion is achieved by employing a first waveguide section 24 that transmits the light along the X direction and a first set of facets in waveguide section 24 to progressively redirect the image illumination within the waveguide system 20 in the Y direction, also trapped / guided by internal reflection.

[0066] The deflected image illumination then passes into a second waveguide section 26, which may be implemented as an adjacent distinct substrate or as a continuation of a single substrate, in which a coupling-out arrangement (for example, a further set of partially reflective facets) progressively couples out a portion of the image illumination in the Z direction towards the eye of an observer located within a section defined as the eye-motion box (EMB), thereby achieving a second dimension of optical aperture expansion. Similar functionality may be obtained using diffractive optical elements (DOEs) for redirecting and / or coupling-out of image illumination within one or both of sections 24 and 26.

[0067] The overall device may be implemented separately for each eye and is preferably supported relative to the head of a user with each waveguide system 20 facing a corresponding eye of the user. In one particularly preferred option as illustrated here, a support arrangement is implemented as an eyeglass frame with sides for supporting the device relative to ears of the user. Other forms of support arrangement may also be used, including but not limited to, head bands, visors or devices suspended from helmets.

[0068] Reference is made herein in the drawings and claims to an X axis which extends horizontally (or, in alternative embodiments, vertically), in the general extensional direction of the first section 24 of the waveguide system 20, a Y axis which extends perpendicular thereto, i.e. , vertically in Fig. 2 (or, in alternative embodiments, horizontally), and a Z axis which extends perpendicular thereto, i.e., horizontal towards the eye of the user. In very approximate terms, the first section 24 of waveguide system 20, may be considered to achieve aperture expansion in the X direction while the second section 26 of waveguidesystem 20 achieves aperture expansion in the Y direction. The details of the spread of angular directions in which different parts of the field of view propagate will be addressed more precisely below. It should be noted that the orientation as illustrated in Fig. 2 may be regarded as a “top-down” implementation, where the image illumination entering the second section 26 of the waveguide system 20 enters from the top edge, whereas an alternative orientation may be regarded as a “side-injection” implementation, where the axis referred to here as the Y axis is deployed horizontally.

[0069] In the remaining drawings, the various features of certain embodiments of the present invention will be illustrated in the context of a “top-down” orientation, similar to Fig. 2. However, it should be appreciated that all of those features are equally applicable to side-injection implementations, which also fall within the scope of the invention. In certain cases, other intermediate orientations are also applicable, and are included within the scope of the present invention except where explicitly excluded. The two-dimensional expansion embodiments illustrated here are merely exemplary, but the invention is also applicable to embodiments in which only a single dimension of aperture expansion is performed by the waveguide system 20.

[0070] It will be appreciated that the near-eye display 23 includes various additional components, typically including a controller 29 for actuating the image projector or POD 22, typically employing electrical power from a small onboard battery (not shown) or some other suitable power source. It will be appreciated that controller 29 can include all necessary electronic components such as at least one processor or processing circuitry to drive the image projector 22.

[0071] In two-dimensional aperture expansion (aperture multiplication) for a NED, the image projector 22 projects collimated light beams representing an image at infinity (two arrows represent the beams of the edge of the image). The light from projector 22 enters waveguide system 20 and propagates while in one dimension being guided by total internal reflection (TIR) and in the other dimension diverging (different beams of different parts of the image diverge). The beams propagate within waveguide system 20 and specifically first section 24 (also referred to as an HLOE) by total internal reflection as shown in Fig. 2(a) Top View. The beams impinge on embedded partial reflectors 24a of first section 24 asshown in Fig. 2(b) Front View and redirect toward partial reflectors 26a of second section 26 (also referred to as a light-guide optical element (LOE)) that reflect the beams out of the waveguide system 20 and toward the observer or eye motion box (EMB) 28 as shown in Fig. 2(c) Side View.

[0072] Partial reflectors 24a and 26a multiply the aperture laterally and vertically, respectively. The length, position and spacing of facets 24a and 26a may vary (shown as same distance for clarity) for achieving an optimal and uniform projected image. Facets 24a and 26a may be perpendicular or oblique relative to external faces of the HLOE 24 and LOE 26, respectively. A waveplate may be introduced between HLOE 24 and LOE 26 to improve reflectivity. A longitudinal partial reflector (homogenizer) may be introduced before the HLOE 24 (improved light injection) or after the HLOE 24 for better image uniformity.

[0073] Solutions for 2D expansion utilizing the aforementioned HLOE and LOE are commercially available from Lumus Ltd. (Israel), and details of such waveguide systems can be found in, for example, commonly owned International Patent Application Publication WO 2020 / 049542 A1 .

[0074] The waveguide system 20 of Fig. 2 is relatively large, particularly in the height (Y) dimension, which makes a corresponding NED 23 relatively large and bulky. NED users, however, seek greater comfort. Comfort is a crucial factor since users often wear these devices for extended periods. Consumers desire lightweight, sleek designs that are less obtrusive and more convenient to wear in various scenarios. Smaller devices also offer improved portability, making them easier to carry and use in different environments. As such, there is a growing demand for smaller and more compact NED. Miniaturization of waveguides would allow for smaller, more comfortable NED. However, conventionally, there have been limitations in miniaturizing waveguides, which in turn restricts the miniaturization of NED.

[0075] Fig. 3 illustrates a novel waveguide system 40 for a NED, such as a VR NED. In the waveguide system 40 an image projector 42 provides light input to a first waveguide section 44. The first waveguide section (HLOE) 44 overlaps with a second waveguide section (LOE) 46. The waveguide sections 44 and 46 may be substantially parallel to one another or may be at a small angle between one another. Substantially parallel in thiscontext may mean that longitudinal axes (i.e., axes along the Y direction in Fig. 3) of the waveguide sections 44 and 46 are parallel to each other or at a small angle (i.e., 0 to 5 degrees) to each other. The waveguide sections 44 and 46 may define a gap 47 between them. The gap 47 may be configured to maintain the total internal reflection condition within the first waveguide section 44 and within the second waveguide section 46. For example, the gap 47 may be an air gap. As an alternative, the gap 47 may be filled in whole or in part with a low-refractive-index adhesive, for example to bond the waveguide sections 44 and 46 together. Examples of low refractive index adhesives that may be used to fill the gap 47 may include silicone-based adhesives (typical refractive indices in the range of 1 .40 to 1 .43), UV-curable epoxy (typical refractive indices in the range of 1 .47 to 1 .50), acrylic adhesives (typical refractive indices in the range of 1 .45 to 1 .50), cyanoacrylate adhesives, optical gels, polymer optical adhesives, etc.

[0076] The first waveguide section 44 has an aperture 44c through which light beams corresponding to an image from the image projector 42 enter the waveguide system 40. In the first waveguide section 44, light beams propagate in a first dimension (e.g., X). The first waveguide section 44 guides light in the Y dimension by total internal reflection (TIR). The first waveguide section 44 includes the partial reflectors 44a. The partial reflectors 44a expand the aperture in the first dimension (e.g., X).

[0077] At its end (opposite the aperture 44c), the first section 44 includes a redirecting component 44b (e.g., a folding mirror) that redirects the light beams to propagate in a third dimension (e.g., Z) nonparallel (e.g., perpendicular) to the first dimension (e.g., X) and the second dimension (e.g., Y) towards the second waveguide section 46. The second waveguide section 46 has a redirecting component 46b (e.g., a folding mirror) that redirects the incoming light to a direction (e.g., Y) within the second waveguide section 46. The redirecting component 46b redirects the light to partial reflectors 46a of second section 46. The second waveguide section 46 receives and propagates the light beams in the third dimension (e.g., Y). The second waveguide section 46 guides light in the Z dimension by total internal reflection. The second set of partially reflecting surfaces 46a couples out the image in the third dimension (e.g., Z) so as to expand the aperture in the second dimension (e.g., Y).

[0078] Light may be reflected from the partially reflecting surfaces 46a out of the second waveguide section toward a viewer, represented in Fig. 3 as EMB 48. In this configuration the overlapping of the waveguide sections 44 and 46 along the third dimension (Z) reduces the overall size of the waveguide system 40, relative to systems where waveguide sections are stacked edge to edge (Fig. 2) or are perpendicular to one another.

[0079] Fig. 4 shows another embodiment, a waveguide system 50 wherein a first waveguide section (HLOE) 54 overlaps a second waveguide section (LOE) 56, with a nonzero angle a between the sections 54 and 56. An image projector 52 provides light input to an aperture 54c of the first waveguide section 54. Nonlimiting example ranges of angle between the waveguide sections 54 and 56 are 1 to 89 degrees, and 5 to 45 degrees.

[0080] In the first waveguide section 54, light beams propagate in a first dimension (e.g., X). The first waveguide section 54 guides light in the Y dimension by total internal reflection (TIR). More broadly, the direction of propagation by TIR is parallel to the major surfaces (faces) of the first waveguide section 54. The first waveguide section 54 includes the partial reflectors 54a that expand the aperture in the first dimension (e.g., X).

[0081] Adjacent its end (opposite the aperture 54c), the first section 54 is optically coupled to a prism 57, which may be adhered to the first section 54 by a suitable adhesive having a refractive index closely matched to the materials of the first section 54 and the prism 57. Examples of suitable adhesives for this application include refractive index- matched optical adhesives such as UV-curable epoxy, Norland Optical Adhesive 61 (NOA61 ), etc.

[0082] Prism 57 redirects the light beams to propagate from the first waveguide section 54 towards the second waveguide section 56. The second waveguide section 56 has a redirecting component 56b (e.g., a folding mirror) that redirects the incoming light to a direction within the second waveguide section 56. The direction of propagation through the second waveguide section 56 may be parallel to major surfaces (faces) of the waveguide section 56. The redirecting component 56b redirects the light to partial reflectors 56a of second section 56. The second waveguide section 56 guides light between its major surfaces by total internal reflection. The second set of partially reflecting surfaces 56acouples out the image in a direction (which may be from the Z direction to a direction perpendicular to the major surfaces of the second waveguide section 56) so as to expand the aperture in a third dimension (along an axis having Y and Z components extending parallel to the major surfaces of the waveguide section 56).

[0083] Light may be reflected from the partially reflecting surfaces 56a out of the second waveguide section 56 toward a viewer, represented as an EMB 58.

[0084] Fig. 5 shows another embodiment, a waveguide system 60. The waveguide system 60 is similar to the waveguide system 50 (Fig. 4), except that in the waveguide system 60 a reflector 64b is part of a first waveguide section 64, as opposed to part of a second waveguide section (as was the case with the second waveguide section 54 (Fig. 4) of the waveguide system 50.

[0085] In the waveguide system 60, the first waveguide section (HLOE) 64 overlaps a second waveguide section (LOE) 66, with a nonzero angle a between the sections 64 and 66. An image projector 62 provides light input to an aperture 64c of the first waveguide section 64. Nonlimiting example ranges of angle between the waveguide sections 64 and 66 are 1 to 89 degrees, and 5 to 45 degrees.

[0086] In the first waveguide section 64, light beams propagate in a first dimension (e.g., X). The first waveguide section 64 guides light in the Y dimension by total internal reflection (TIR). More broadly, the direction of propagation by TIR is parallel to the major surfaces (faces) of the first waveguide section 64. The first waveguide section 64 includes the partial reflectors 64a that expand the aperture in the first dimension (e.g., X).

[0087] At its end (opposite the aperture 64c), the first section 64 has a redirecting component 64b (e.g., a folding mirror), which directs light toward a prism 67 that is optically coupled to the first section 64. Prism 67 may be coupled to the first section 64 by a suitable adhesive, as described above in reference to the system 50 of Fig. 4. The combination of component 64b and prism 67 redirects the light beams to propagate from the first waveguide section 64 towards the second waveguide section 66. In the second waveguide section 66, light may travel (propagate) in a direction within the second waveguide section 66. The direction of propagation through the second waveguide section 66 may be parallel to major surfaces (faces) of the waveguide section 66. The light propagates to partialreflectors 66a of second section 66. The second waveguide section 66 guides light between its major surfaces by total internal reflection. The second set of partially reflecting surfaces 66a couple out the image in a direction (which may be from the Z direction to a direction perpendicular to the major surfaces of the second waveguide section 66), so as to expand the aperture in a third dimension (along an axis having Y and Z components extending parallel to the major surfaces of the waveguide section 66).

[0088] Light may be reflected from the partially reflecting surfaces 66a out of the second waveguide section 66 toward a viewer, represented as an EMB 68.

[0089] Fig. 6 illustrates an embodiment of a waveguide system 70 embedded in a standard eyeglasses frame 107. The waveguide system 70 may represent any of the novel embodiments described herein. An image projector (POD or display source) 72 may be assembled inside the arm portions 112 of the eyeglasses frame 107. For a case in which the display source 72 is an electronic element, such as a small CRT, LCD, or OLED, the driving electronics (or controller) 114 for the display source might be assembled inside the back portion of the arm 112. A power supply and data interface 116 is connectable to arm 112 by a lead 118 or other communication means including radio or optical transmission. Alternatively, a battery and miniature data link electronics can be integrated in the eyeglasses frame 107. The resulting device may be virtual reality (VR) glasses, or more broadly, a VR display. The embodiment described in Fig. 6 is only an example. Other possible head-mounted displays arrangements can be constructed.

[0090] Fig. 7 shows an alternative arrangement, a waveguide system 140 that has one or more additional optical elements 149 between a first waveguide section 144 that receives light from an image projector 142, and a second waveguide section 146 that receives light from the first waveguide section 144. The one or more additional optical elements 149 may be a polarizer or a waveplate, for example. A waveplate may improve reflectivity, for example. A polarizer may enable the use polarization-selective facets, such as the partially-reflective surfaces 144a and 146a.

[0091] The one or more additional optical elements 149 may be a part of the any of the other embodiments described herein. This includes both the embodiments with substantially-parallel waveguide sections, and embodiments with waveguide sections at anonzero angle relative to each other, as part of embodiments including mirrors and / or prisms, for example.

[0092] Fig. 8 shows another embodiment, a waveguide system 160 that includes a first waveguide section 164 and a second waveguide section 166 that are substantially parallel to each other. Light from an image projector 162 enters the first waveguide section 164 through an aperture 164c, after passing through an external prism 163 that compensates for dichromic aberrations in the entering light, and being reflected by a coupling mirror 164a.

[0093] In the first waveguide section 164, light beams propagate in a first dimension (e.g., X). The first waveguide section 164 guides light in the Y dimension by total internal reflection (TIR). More broadly, the direction of propagation by TIR is parallel to the major surfaces (faces) 163a and 163b of the first waveguide section 164.

[0094] At its end (opposite the aperture 164c), the first section 164 has a coupling prism 164b, which directs light toward the second waveguide section 166. A surface 165a of the coupling prism 164b interfaces with the first waveguide. The coupling prism 164b has a mirror surface (mirror coating) 165b which is rotated at about 45 degrees relative to the major surfaces 163a and 163b of the first waveguide section 164. This results in light hitting the mirror surface 165b changing direction by about 90 degrees. The coupling prism surface 165a may have a low index of refraction, lower than that of the material of the first waveguide section 164 that is adjacent to the coupling prism 164b.

[0095] The coupling prism 164b directs light toward the second waveguide system 166. Light travelling from the first waveguide section 164 to the second waveguide system 166 passes through a low-refractive index layer 168 that is between the waveguide sections 164 and 166. The low-refractive index layer 168 may be an air layer, or may be a layer of another low-refractive index material, such as a low-refractive index optical adhesive. The index of refraction of the low- refractive index layer 168 may be lower than that of the material of the first waveguide section 164 that is adjacent to the coupling prism 164b.

[0096] The light that passes through the low-refractive index layer 168 passes into a coupling prism 166b of the second waveguide section 166. The coupling prism 166b may be similar in configuration and operation to the coupling prism 164b. The coupling prism166b has a surface 167a and a mirror surface 167b. The mirror surface 167b turns light about 45 degrees, to direct the light through the surface 167a and into and along the rest of the second waveguide section 166. The mirror surface 167b thus changes direction of light by about 90 degrees. The coupling prism surface 165a may have a low index of refraction, lower than that of the material of the first waveguide section 164 that is adjacent to the coupling prism 164b. The coupling prism surface 167a may have a low index of refraction, lower than that of the material of the second waveguide section 166 that is adjacent to the coupling prism 166b.

[0097] In the second waveguide section 166, light may travel (propagate) in a direction within the second waveguide section 166. The direction of propagation through the second waveguide section 166 may be parallel to major surfaces (faces) 169a and 169b of the waveguide section 166. The second waveguide section 166 guides light between its major surfaces 169a and 169b by total internal reflection.

[0098] The waveguide sections 164 and 166 may include various types of internal elements, such as mixers and partial reflectors. Mixers are internal surfaces parallel to major surfaces, which mix the light of the waveguide section, and increase spatial homogeneity. The partial reflectors may include partial ly-ref lective surfaces (or “facets”) parallel to one another at oblique angles to major surfaces of the waveguide section, perhaps in combination with partially-reflective surfaces or facets parallel to one another and normal (perpendicular) to major surfaces of the waveguide section. Similar functionality of optical expansion may be obtained using diffractive optical elements (DOEs) for redirecting and / or coupling-out of image illumination within one or both of sections 164 and 166.

[0099] For instance, in the illustrated embodiment the first waveguide section 164 may include a mixer 174 and the second waveguide section 166 may include a mixer 176. The second waveguide section 166 includes partially-reflective surfaces 178 that expand the aperture. The partially-reflective surfaces 178 may be oblique reflectors that reflect light out of the second waveguide section 166 toward a viewer, represented as an EMB 172. The second waveguide section 166 thus may function as an LOE. In addition the second waveguide section 166 may also function as an HLOE, with a second set of partially-reflective surfaces normal to the major surfaces 169a and 169b, that spread the light in an additional direction.

[0100] The change in light direction effected by each of the coupling prisms 164b and 166b may be 90 degrees or very close to 90 degrees. For example, the light direction change may be about 90 degrees, such as being within 30 arcseconds of 90 degrees. More broadly the change in light direction may be about 90 degrees, such as within 1 degree of 90 degrees. The description herein of a mirrored surface being at “about 45 degrees” or “substantially at 45 degrees” relative to major surfaces of a waveguide section, should be understood as referring to this level of precision in light turning.

[0101] The waveguide sections 164 and 166 may be substantially parallel to one another. “Substantially parallel” in this context should be understood as referring to the level of precision described in the previous paragraph.

[0102] Fig. 9 shows another embodiment, a waveguide system 180 that includes three waveguide sections, a first waveguide section 184, a second waveguide section 186, and a third waveguide section 204, all of which are substantially parallel to each other. Light from an image projector 182 enters the first waveguide section 184 through an aperture 184c, after passing through an external prism 183 that compensates for dichromic aberrations in the entering light, thereafter being reflected by a coupling mirror 184a.

[0103] In the first waveguide section 184, light beams propagate in a first dimension (e.g., X). The first waveguide section 184 guides light in the Y dimension by total internal reflection (TIR). More broadly, the direction of propagation by TIR is parallel to the major surfaces (faces) 183a and 183b of the first waveguide section 184.

[0104] At its end (opposite the aperture 184c), the first section 184 has a coupling prism 184b, which directs light toward the second waveguide section 186. A surface 185a of the coupling prism 184b interfaces with the first waveguide. The coupling prism 184b has a mirror surface (mirror coating) 185b which is rotated at about 45 degrees relative to the major surfaces 183a and 183b of the first waveguide section 184. This results in light hitting the mirror surface 185b changing direction by about 90 degrees. The coupling prism surface 185a may have a low index of refraction, lower than that of the material of the first waveguide section 184 that is adjacent to the coupling prism 184b.

[0105] The coupling prism 184b directs light toward the second waveguide system 186. Light travelling from the first waveguide section 184 to the second waveguide system 186 passes through a low- refractive index layer 188 that is between the waveguide sections 184 and 186. The low-refractive index layer 188 may be an air layer, or may be a layer of another low-refractive index material, such as a low-refractive index optical adhesive. The index of refraction of the low- refractive index layer 188 may be lower than that of the material of the first waveguide section 184 that is adjacent to the coupling prism 184b.

[0106] The light that passes through the low-refractive index layer 188 passes into a coupling prism 186b of the second waveguide section 186. The coupling prism 186b may be similar in configuration and operation to the coupling prism 184b. The coupling prism 186b has a surface 187a and a mirror surface 187b. The mirror surface 187b turns light about 45 degrees, to direct the light through the surface 187a and into and along the rest of the second waveguide section 186. The mirror surface 187b thus changes direction of light by about 90 degrees. The coupling prism surface 187a may have a low index of refraction, lower than that of the material of the second waveguide section 186 that is adjacent to the coupling prism 186b.

[0107] In the second waveguide section 186, light may travel (propagate) in a direction within the second waveguide section 186. The direction of propagation through the second waveguide section 186 may be parallel to major surfaces (faces) 189a and 189b of the waveguide section 186. The second waveguide section 186 guides light between its major surfaces 189a and 189b by total internal reflection.

[0108] The second waveguide section 186 also has a second coupling prism 186c for coupling light to the waveguide section 204. The second coupling prism 186c directs light through a low-refractive index layer 208, to a coupling prism 204b of the third waveguide section 204. The coupling and turning between the waveguide sections 186 and 204 may be similar to the coupling between the waveguide sections 184 and 186.

[0109] The waveguide sections 184, 186, and 204 may include various types of internal elements, such as mixers and partial reflectors. Mixers are internal surfaces parallel to major surfaces, which mix the light of the waveguide section, and increasespatial homogeneity. The partial reflectors may include partially-reflective surfaces (or “facets”) parallel to one another at oblique angles to major surfaces of the waveguide section, perhaps in combination with partially-reflective surfaces or facets parallel to one another and normal (perpendicular) to major surfaces of the waveguide section.

[0110] For instance, in the illustrated embodiment the first waveguide section 184 may include a mixer 194 and the second waveguide section 186 may include a mixer 196. The third waveguide section 204 may also include a mixer 206. The third waveguide section 204 includes partially-reflective surfaces 208 that expand the aperture. The partially-reflective surfaces 208 may be oblique reflectors that reflect light out of the third waveguide section 204 toward a viewer, represented as an EMB 212. The third waveguide section 204 thus may function as an LOE. In addition the third waveguide section 204 may also function as an HLOE, with a second set of partially-reflective surfaces normal to its major surfaces, that spread the light in an additional direction.

[0111] The change in light direction effected by each of the coupling prisms 184b, 186b, 186c, and 204b may be 90 degrees or very close to 90 degrees. For example, the light direction change may be about 90 degrees, such as being within 30 arcseconds of 90 degrees. More broadly the change in light direction may be about 90 degrees, such as within 1 degree of 90 degrees. The description herein of a mirrored surface being at “about 45 degrees” or “substantially at 45 degrees” relative to major surfaces of a waveguide section, should be understood as referring to this level of precision in light turning.

[0112] The waveguide sections 184, 186, and 204 may be substantially parallel to one another. “Substantially parallel” in this context should be understood as referring to the level of precision described in the previous paragraph.

[0113] Fig. 10 shows another embodiment, a waveguide system 220 that has three waveguide sections 224, 226, and 228. The waveguide sections 224 and 226 may be similar in function and configuration to the waveguide sections 184 and 186 (Fig. 9), as described above. The third waveguide section 228 is similar to the third waveguide section 204 (Fig. 9), with the substitution of a diffraction grating 230 for the partially-reflective surfaces 208 (Fig. 9).

[0114] Figs. 11 -13 illustrates steps in a process of producing waveguide sections,such as those described above in other embodiments. The process of manufacturing the waveguide sections can be done in a way which better suits mass production. Instead of manufacturing every waveguide section singly, it is possible to form multiple waveguide sections in a single batch.

[0115] Fig. 1 1 illustrates a first step in process, where stacks of mirrors 302 and 304 are placed on opposite sides of a stack of mixers 306. The mirrors of the mirror stacks 302 and 304 have their mirrored surfaces 302a and 304a at 45 degrees relative to their flat end surfaces 302b and 304b. The mixer stack 306 has internal mixer facets 306a at 90 degrees relative to flat end surfaces 306b and 306c. The stacks 302, 304, and 306 are then glued or adhesively joined together, with the end surfaces 302b and 306b joined together, and the end surfaces 394b and 306c joined together. This yields a combined stack 310. The optical adhesive is preferably of low refractive index relative to the material of the mirror stacks 302 and 304.

[0116] Fig. 12 shows a next step in the process, where the combined stack 310 is cut parallel to the internal mixer facets 306a. This cutting is accomplished, for example, at cut lines 312 midway between adjacent of the mixer facets 306a. This yields a set of singulated identical waveguide sections 322, 324, 326, and 328.

[0117] As illustrated in Fig. 13, two of the waveguide sections 322 and 324 may be combined to produce a waveguide system 330. As shown, first one of the waveguide sections 324 is flipped (or reversed or rotated). Then the waveguide sections 322 and 324 are adhesively joined together, such as with a low-refractive-index optical adhesive, to produce the waveguide system 330. It will be appreciated that the waveguide system 330 that is produced by this process corresponds to the combined waveguide sections 184 and 186 (Fig. 9) described above.DEFINITIONS

[0118] The following includes definitions of selected terms employed herein. The definitions include various examples or forms of components that fall within the scope of a term and that may be used for implementation. The examples are not intended to be limiting. Both singular and plural forms of terms may be within the definitions.

[0119] An “operable connection,” or a connection by which entities are “operably connected,” is one in which signals, physical communications, or logical communications may be sent or received. Typically, an operable connection includes a physical interface, an electrical interface, or a data interface, but it is to be noted that an operable connection may include differing combinations of these or other types of connections sufficient to allow operable control. For example, two entities can be operably connected by being able to communicate signals to each other directly or through one or more intermediate entities like a processor, operating system, a logic, software, or other entity. Logical or physical communication channels can be used to create an operable connection.

[0120] To the extent that the term “includes” or “including” is employed in the detailed description or the claims, it is intended to be inclusive in a manner similar to the term “comprising” as that term is interpreted when employed as a transitional word in a claim. Furthermore, to the extent that the term “or” is employed in the detailed description or claims (e.g., A or B) it is intended to mean “A or B or both.” When the applicants intend to indicate “only A or B but not both” then the term “only A or B but not both” will be employed. Thus, use of the term “or” herein is the inclusive, and not the exclusive use. See, Bryan A. Garner, A Dictionary of Modern Legal Usage 624 (2d. Ed. 1995).

[0121] While example systems, methods, and so on, have been illustrated by describing examples, and while the examples have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit scope to such detail. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the systems, methods, and so on, described herein. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention is not limited to the specific details, the representative apparatus, and illustrative examples shown and described. Thus, this application is intended to embrace alterations, modifications, and variations that fall within the scope of the appended claims. Furthermore, the preceding description is not meant to limit the scope of the invention. Rather, the scope of the invention is to be determined by the appended claims and their equivalents.

Claims

CLAIMSWhat is claimed is:1 . A waveguide system for a near-eye display, the waveguide system comprising: a first waveguide section having an aperture through which light beams corresponding to an image from an image projector enter the waveguide system; one or more first optical elements configured to couple light corresponding to the image out of the first waveguide section so as to expand the aperture in a first dimension; a second waveguide section configured to receive light from the first waveguide section and including one or more second optical elements configured to couple out light corresponding to the image so as to expand the aperture in a second dimension nonparallel to the first dimension; and one or more reflectors that reflect the light corresponding to the image from the first waveguide section towards the second waveguide section; wherein the second waveguide section overlaps the first waveguide section in a direction of light output from the second waveguide section.

2. The waveguide section of claim 1 , wherein the one or more reflectors include one or more folding mirrors.

3. The waveguide section of claim 1 , wherein the one or more first optical elements and the one or more second optical elements include partial reflectors.

4. The waveguide system of claim 1 , wherein the first dimension is perpendicular to the second dimension.

5. The waveguide system of claim 1 , wherein the first waveguide section and thesecond waveguide section are substantially parallel to one another.

6. The waveguide system of claim 1 , wherein the first waveguide section and the second waveguide section are at an angle of 1 to 89 degrees to one another.

7. The waveguide system of claim 1 , wherein the first waveguide section and the second waveguide section define a gap therebetween.

8. The waveguide system of claim 7, wherein the gap is an air gap.

9. The waveguide system of claim 7, wherein the gap is filled at least in part by a low-refractive-index adhesive.

10. The waveguide system of claim 1 , wherein the aperture is at a first end of the first waveguide section, and wherein at least one of the one or more reflectors is disposed at a second end of the first waveguide section that is opposite the first end.11 . The waveguide system of claim 1 , wherein the one or more reflectors include a reflector in the first waveguide section.

12. The waveguide system of claim 1 , wherein the one or more reflectors include a reflector in the second waveguide section.

13. The waveguide system of claim 1 , wherein the one or more reflectors include a first reflector in the first waveguide, and a second reflector in the second waveguide.

14. The waveguide system of claim 1 , further comprising a prism optically coupling the first waveguide section and the second waveguide section.

15. The waveguide system of claim 14, wherein the prism cooperates with the one more reflectors to turn light from a first propagation direction in the first waveguide section, toward the prism, to a second propagation direction in the second waveguide section, away from the prism.

16. The waveguide system of claim 1 , further comprising one or both of a polarizer and a waveplate, between the first waveguide section and the second waveguide section.

17. The waveguide system of claim 1 , in combination with an image projector operatively coupled to the aperture.

18. The combination of claim 17, in combination with a controller coupled to the image projector, to drive the image projector.

19. The waveguide system of claim 1 , wherein the waveguide system is part of a virtual reality system.

20. The waveguide system of claim 1 , wherein the waveguide system is part of virtual reality glasses.21 . A waveguide system for a near-eye display, the waveguide system comprising: a first waveguide section having an aperture at through which light beams corresponding to an image from an image projector enter the waveguide system; one or more first optical elements in the first waveguide section;a first coupling prism in the first waveguide section, wherein the first coupling prism has a reflecting surface at substantially 45 degrees relative to major surfaces of the first waveguide surface; a second waveguide section configured to receive light from the first waveguide section; one or more second optical elements configured to couple out light corresponding to the image; and a second coupling prism in the second waveguide section, wherein the second coupling prism has a reflecting surface at substantially 45 degrees relative to major surfaces of the second waveguide surface; wherein the first and second coupling prisms in combination turn and direct light from the first waveguide section into the second waveguide section; and wherein the second waveguide section is substantially parallel to the first waveguide section in a direction of light output from the second waveguide section.

22. The waveguide system of claim 21 , wherein the first coupling prism and the second coupling prism have a higher refractive index than other portions of the first waveguide section and the second waveguide section.

23. The waveguide system of claim 21 , wherein the one or more first optical elements include an optical mixer.

24. The waveguide system of claim 21 , wherein the one or more second optical elements include an optical mixer.

25. The waveguide system of claim 21 , wherein the one or more second opticalelements include one or more partially reflective surfaces.

26. The waveguide system of claim 25, wherein the one or more partially reflective surfaces include partially reflective surfaces parallel to one another and oblique to the second major surfaces.

27. The waveguide system of claim 25, wherein the one or more partially reflective surfaces include partially reflective surfaces parallel to one another and normal to the second major surfaces.

28. The waveguide system of claim 21 , further comprising a layer of low-refractive- index material between the coupling prisms, the low-refractive-index material having an index of refraction lower than other portions of the first waveguide section and the second waveguide section.

29. The waveguide system of claim 28, wherein the low-refractive index material includes an optical adhesive.

30. The waveguide system of claim 21 , further comprising layers of low-refractive- index material between respective of the coupling prisms, and other portions of the first waveguide section and the second waveguide section, the low-refractive-index material having an index of refraction lower than the other portions of the first waveguide section and the second waveguide section.31 . The waveguide system of claim 30, wherein the low-refractive index material includes an optical adhesive.

32. The waveguide system of claim 21 , further comprising a third waveguide section substantially parallel to the first waveguide section and the second waveguide section, with light passing from the second waveguide section to the third waveguide section through an additional coupling prism of the second waveguide section, and a third coupling prism of the third waveguide section.

33. The waveguide system of claim 32, wherein the additional coupling prism has a reflecting surface at substantially 45 degrees relative to the major surfaces of the second waveguide surface; and wherein the third coupling prism has a reflecting surface at substantially 45 degrees relative to major surfaces of the third waveguide surface.

34. The waveguide system of claim 32, wherein the third waveguide surface includes one or more third optical elements.

35. The waveguide system of claim 34, wherein the one or more third optical elements include an optical mixer.

36. The waveguide system of claim 34, wherein the one or more third optical elements include one or more partially reflective surfaces.

37. The waveguide system of claim 36, wherein the one or more partially reflective surfaces include partially reflective surfaces parallel to one another and oblique to the second major surfaces.

38. The waveguide system of claim 36, wherein the one or more partially reflective surfaces include partially reflective surfaces parallel to one another and normal to thesecond major surfaces.

39. The waveguide system of claim 34, wherein the one or more third optical elements include a diffractive grating that directs light out of the third waveguide section.

40. The waveguide system of claim 21 , wherein the waveguide system is part of virtual reality glasses.41 . A method of forming a waveguide system, the method comprising: attaching mirror stacks to opposite respective ends of a mixer stack, to form a combined stack; cutting the combined stack to produce first and second waveguide sections, each of the waveguide sections including a mixer from the mixer stack, and a pair of mirrors from the mirror stacks at opposite respective ends of the mixer; and adhesively attaching the waveguide sections together, with the waveguide sections configured such that the mirrors of the waveguide sections cooperate to turn and direct light from the first waveguide section to the second waveguide sections.

42. The method of claim 41 , wherein the attaching includes attaching with optical adhesive.

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