Optical system comprising two-dimensional extended light guide optical element with intermediate extended region

Abstract

The LOE has a first region having a first set of facets and a second region having a second set of facets that are different in orientation than the first set of facets. The two sets of facets are located between a set of parallel major outer surfaces. An intermediate region between the facet regions has a diffractive optical aperture expansion configuration. An image illumination introduced into the LOE from an image projector propagates along the LOE, is redirected by a first set of facets to an intermediate region in which the image illumination is deflected by a diffractive optical aperture expansion configuration to a second region to expand an optical aperture of the image projector in a first dimension such that the optical aperture is further expanded in the first dimension. The image illumination is then coupled out of LOE through a second set of facets, thereby expanding the optical aperture in a second dimension.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 426,753, filed on November 20, 2022, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] The present disclosure relates to optical systems, and in particular, to optical systems including a light-guide optical element (LOE) for achieving optical aperture expansion. Background Art

[0004] The optics of Near Eye Display (NED), Head Mounted Display (HMD) and Head Up Display (HUD) require a large aperture to cover the area where the observer's (user's) eyes are located (commonly referred to as an eye box or EMB). In order to achieve a compact device, the image to be projected into the observer's eye is generated by a small optical image generator (projector) with a small optical aperture. The image from the image projector is transmitted to the eye through the LOE, which expands (multiplies) the image to generate a large aperture.

[0005] To achieve uniformity of the viewed image, the LOE should be uniformly "filled" by the projected image and its conjugate image. This imposes design constraints on the size of the image projector and various other aspects of the optical design. Summary of the invention

[0006] The present disclosure provides one or more optical systems each having at least one light guide optical element (LOE) for directing image illumination from an image projector to an eye box for viewing by an eye of a user.

[0007] According to the teachings of embodiments of the present disclosure, a light guide optical element (LOE) is provided for directing image illumination from an image projector to an eye box for viewing by an eye of a user. The LOE is formed of a transparent material and includes: a first region comprising a first optical aperture expansion configuration including mutually parallel partially reflective surfaces of a first set of planes having a first orientation; a second region comprising a second optical aperture expansion configuration including mutually parallel partially reflective surfaces of a second set of planes having a second orientation that is not parallel to the first orientation; an intermediate region located between the first region and the second region having a diffractive optical aperture expansion configuration including at least one diffractive element; and a pair of mutually parallel primary outer surfaces extending across the first region and the second region such that both the first set of partially reflective surfaces and the second set of partially reflective surfaces are located between the primary outer surfaces, and image illumination from the image projector is propagated by internal reflections at the primary outer surfaces. The optical aperture expansion configuration is configured such that: image illumination injected into the LOE and propagated by internal reflection at the main outer surface is deflected by the first optical aperture expansion configuration to an intermediate region to expand the optical aperture of the image projector in a first dimension, in the intermediate region, the image illumination is deflected by the diffractive optical aperture expansion configuration to a second region to further expand the optical aperture of the image projector in the first dimension, and in the second region, the image illumination is deflected by the second optical aperture expansion configuration so that the image illumination is coupled out of the LOE toward the eye box and the optical aperture of the image projector is expanded in a second dimension.

[0008] Optionally, the diffractive optical aperture expansion configuration is configured to expand the optical aperture of the image projector in a second dimension.

[0009] Optionally, at least one diffractive element is located at a mid-plane of the LOE parallel to the main outer surface.

[0010] Optionally, at least one diffractive element is configured to deflect the image at a right angle to a first color, and to deflect the image at a slightly smaller angle than the right angle to a second color, and to deflect the image at a slightly larger angle than the right angle to a third color.

[0011] Optionally, at least one diffractive element is located at one of the major outer surfaces.

[0012] Optionally, at least one diffractive element is located as a surface relief grating at one of the major outer surfaces.

[0013] Optionally, the at least one diffraction element includes a first diffraction element located at a first one of the main outer surfaces and a second diffraction element located at a second one of the main outer surfaces.

[0014] Optionally, the first diffraction element is located at a first one of the major outer surfaces as a first surface relief grating, and the second diffraction element is located at a second one of the major outer surfaces as a second surface relief grating.

[0015] Optionally, the first diffraction element and the second diffraction element have the same grating orientation and spacing.

[0016] Optionally, the first diffractive element is configured to diffract image illumination of a first color and image illumination of a second color, and the second diffractive element is configured to diffract image illumination of the first color and image illumination of a third color.

[0017] Optionally, the first diffraction element and the second diffraction element have the same grating orientation and spacing, but different grating shapes.

[0018] Optionally, the diffractive optical aperture expansion arrangement is configured to deflect image illumination propagating by internal reflection between the major outer surfaces from the third region to the second region at approximately a right angle.

[0019] Optionally, the second region is offset relative to the first region and the intermediate region along the first dimension.

[0020] Optionally, the image illumination propagates in the intermediate region by total internal reflection (TIR) ​​between the major exterior surfaces and encounters the diffractive optical aperture expansion configuration twice in a single TIR round trip.

[0021] Optionally, the image illumination propagates in the intermediate region by total internal reflection (TIR) ​​between the major exterior surfaces and encounters the diffractive optical aperture expansion configuration once in a single TIR round trip.

[0022] Optionally, the LOE further comprises: a second pair of mutually parallel major outer surfaces forming a rectangular cross-section at the first region, such that image illumination injected into the LOE advances through the first region by quadruple internal reflection at the two pairs of major outer surfaces.

[0023] According to the teachings of embodiments of the present disclosure, there is also provided a light guide optical element (LOE) for directing image illumination from an image projector to an eye box for viewing by an eye of a user. The LOE is formed of a transparent material and includes: a first region comprising a first set of mutually parallel partially reflective surfaces of a plane; a second region comprising a second set of mutually parallel partially reflective surfaces of a plane; a third region comprising a third set of mutually parallel partially reflective surfaces of a plane; and a pair of mutually parallel main outer surfaces, the main outer surfaces extending across the first region, the second region, and the third region, such that the first set of partially reflective surfaces, the second set of partially reflective surfaces, and the third set of partially reflective surfaces are located between the main outer surfaces, and the image illumination from the image projector is propagated by internal reflection at the main outer surfaces. The third group of partially reflective surfaces is oriented non-parallel to the first group of partially reflective surfaces, and the second group of partially reflective surfaces is oriented non-parallel to the third group of partially reflective surfaces, and the first group of partially reflective surfaces, the second group of partially reflective surfaces and the third group of partially reflective surfaces are configured such that: image illumination injected into the LOE and propagated by internal reflection at the main outer surface is deflected by the first group of partially reflective surfaces to the second region to expand the optical aperture of the image projector in the first dimension, wherein the image illumination is deflected by the second group of partially reflective surfaces to the third region to further expand the optical aperture of the image projector in the first dimension, and wherein the image illumination is deflected by the third group of partially reflective surfaces so that the image illumination is coupled out of the LOE toward the eye box and the optical aperture of the image projector is expanded in the second dimension.

[0024] Optionally, the second set of partially reflective surfaces is perpendicular to the main outer surface.

[0025] Optionally, the second set of partially reflective surfaces are inclined relative to the main outer surface.

[0026] According to the teachings of the embodiments of the present disclosure, an optical system is also provided. The optical system includes: a LOE according to the teachings of any of the embodiments discussed above; and an image projector configured to project image illumination corresponding to the collimated image and optically coupled to the LOE to inject the image illumination into a first region of the LOE to propagate within the LOE by internal reflection at the main outer surface.

[0027] According to the teachings of embodiments of the present disclosure, an optical system is also provided for directing image illumination to an eye box for viewing by an eye of a user. The optical system includes: an image projector having an optical aperture and configured to project image illumination corresponding to a collimated image; and a light guide optical element (LOE) formed of a transparent material and optically coupled to the image projector. The LOE comprises: a first major outer surface and a second major outer surface, the first major outer surface and the second major outer surface are parallel to each other, and image illumination from an image projector is propagated by internal reflection at the major outer surfaces; a first region, which contains a first optical aperture expansion configuration, the first optical aperture expansion configuration includes mutually parallel partially reflective surfaces of a first set of planes having a first orientation; a second region, which contains a second optical aperture expansion configuration, the second optical aperture expansion configuration includes mutually parallel partially reflective surfaces of a second set of planes having a second orientation that is not parallel to the first orientation; and an intermediate region, which is located between the first region and the second region, and has a diffractive optical aperture expansion configuration including a first diffractive element and a second diffractive element, the first diffractive element is located at the first major outer surface, and the second diffractive element is located at the second major outer surface, so that the first diffractive element and the second diffractive element are parallel. The major outer surfaces extend across the first region and the second region, so that both the first set of partially reflective surfaces and the second set of partially reflective surfaces are located between the major outer surfaces. The optical aperture expansion configuration is configured such that: image illumination injected into the LOE and propagated by internal reflection at the main outer surface is deflected by the first optical aperture expansion configuration to an intermediate region to expand the optical aperture of the image projector in a first dimension, in the intermediate region, the image illumination is deflected by the diffractive optical aperture expansion configuration to a second region to further expand the optical aperture of the image projector in the first dimension, and in the second region, the image illumination is deflected by the second optical aperture expansion configuration so that the image illumination is coupled out of the LOE toward the eye box and the optical aperture of the image projector is expanded in a second dimension.

[0028] In the context of this document, the term "guiding" generally refers to light captured within a light-transmitting material (e.g., a substrate) by internal reflection at a major outer surface of the light-transmitting material, such that the light captured within the light-transmitting material propagates through the light-transmitting material in a propagation direction. Light propagating within a light-transmitting substrate is captured by internal reflection when the propagating light is incident on the major outer surface of the light-transmitting material at an angle of incidence within a specific angle range. The internal reflection of the captured light can be in the form of total internal reflection, whereby the propagating light incident on the major outer surface of the light-transmitting material at an angle greater than a critical angle (partially defined by the refractive index of the light-transmitting material and the refractive index of the medium surrounding the light-transmitting material (e.g., air)) is totally internally reflected at the major outer surface. Alternatively, the internal reflection of the captured light can be achieved by a coating, such as an angle-selective reflective coating, which is applied to the major outer surface of the light-transmitting material to achieve reflection of light incident on the major outer surface within a specific angle range.

[0029] Unless otherwise defined herein, all technical terms and / or scientific terms used herein have the same meaning as those generally understood by those of ordinary skill in the art to which the present disclosure belongs. Although methods and materials similar or equivalent to those described herein can be used in practice or when testing the embodiments of the present disclosure, exemplary methods and / or materials are described below. In the event of a conflict, the patent specification (including definitions) shall prevail. In addition, materials, methods and examples are only illustrative and are not intended to be necessarily restrictive. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Some embodiments of the present disclosure are described herein by way of example only with reference to the accompanying drawings. With specific reference to the accompanying drawings in detail, it is emphasized that the details shown are by way of example and for the purpose of illustrative discussion of the embodiments of the present disclosure. In this regard, the description in conjunction with the accompanying drawings makes it clear to those skilled in the art how the embodiments of the present disclosure can be practiced.

[0031] Attention is now directed to the drawings, wherein like reference numerals or characters indicate corresponding or identical parts. In the drawings:

[0032] Figure 1 is a schematic isometric view of a device having a pair of optical systems each implemented using a light-guiding optical element (LOE) constructed and operated according to the teachings of an embodiment of the present disclosure;

[0033] Figure 2A and Figure 2B Schematic front and side views, respectively, showing a LOE according to an embodiment of the present disclosure, the LOE having: a set of major outer surfaces; two regions, each of which comprises a set of partially reflective surfaces (facets) between the major outer surfaces; and an intermediate region, located between the two facet regions, having an intermediate beam expansion configuration implemented as a diffractive device having a diffractive element located in a mid-plane of the LOE;

[0034] Figure 3A and Figure 3B According to the embodiments of the present disclosure, Figure 2A and Figure 2B Schematic front and side views similar but with a single diffractive element located at one of the major outer surfaces of the LOE;

[0035] Figure 4 According to the embodiments of the present disclosure Figure 3B a similar schematic side view but with a diffractive device having a pair of parallel diffractive elements, each diffractive element being located at a respective one of the major outer surfaces of the LOE;

[0036] Figure 5 is an enlarged schematic elevation view of a diffraction device showing the LOE of the paths of different color components of a principal ray incident on the diffraction device according to an embodiment of the present disclosure;

[0037] Figure 6 According to the embodiments of the present disclosure Figure 2A a schematic elevation view of a similar intermediate beam expansion configuration but having a set of partially reflective surfaces implemented between the main outer surfaces; and

[0038] Figure 7 According to the embodiments of the present disclosure Figure 2B A schematic side view of a similar arrangement but where one set of major exterior surfaces comprises two pairs of major exterior surfaces forming a rectangular cross-section at a first facet region. DETAILED DESCRIPTION

[0039] Certain embodiments of the present disclosure provide light-guiding optical elements (LOEs) and optical systems comprising one or more LOEs for achieving optical aperture expansion for the purpose of a heads-up display, and most preferably for the purpose of a near-eye display, which can be a virtual reality display or, more preferably, an augmented reality display.

[0040] The principles and operations of the optical system and LOE according to the present disclosure may be better understood with reference to the accompanying drawings.

[0041] Before describing in detail at least one embodiment of the present disclosure, it should be understood that the present disclosure is not necessarily limited in its application to the details of the construction and arrangement of the methods and / or components set forth in the following description and / or shown in the drawings and / or examples. The present disclosure can have other embodiments or can be practiced or implemented in various ways.

[0042] Referring now to the accompanying drawings, Figure 1 An exemplary implementation of a device near-eye display (generally represented as device 1) employing paired optical systems 2 (one for each eye) in accordance with the teachings of embodiments of the present disclosure is schematically illustrated. Each optical system 2 employs a LOE 8 and a compact image projector ("projection optical device" or "POD") 5 optically coupled to the LOE 8 to inject an image into the LOE (interchangeably referred to as a "waveguide", "substrate" or "plate") 8 within which image light (illumination) is captured by internal reflection at a set of mutually parallel planar major exterior surfaces. In most embodiments described herein, image light is captured in one dimension. However, embodiments will be described in which image light is captured in two dimensions.

[0043] The optical coupling of the POD 5 to the LOE 8 may be achieved by any suitable optical coupling (e.g., via a coupling prism having an input surface with an inclined angle, or via a reflective coupling device, via one of the side edges of the main outer surface of the LOE and / or the main outer surface). The details of the coupling device are not important to the present disclosure and are therefore not shown here.

[0044] LOE 8 has three different regions (also referred to as "sections"), each with an associated optical aperture expansion configuration (also referred to as a "beam expander"). The three regions are denoted as region 10, region 20 and region 15.

[0045] Note that in some of the appended claims, the term “first region” refers to region 10, the term “second region” refers to region 20, and the term “intermediate region” refers to region 15, while in other of the appended claims, the term “first region” refers to region 10, the term “second region” refers to region 15, and the term “third region” refers to region 20.

[0046] Area 10 has Figure 1 , which corresponds to the elongation direction in the Y direction. Region 15 is located between (between) two regions, region 10 and region 20. LOE 8 also includes a fourth region 9 (also referred to as a "coupling" region 9), which is generally defined as the region of LOE 8 where the image from POD 5 is introduced into LOE 8 (i.e., the region of LOE 8 where the coupling device is optically coupled).

[0047] The injected image light passes through the LOE 8 by internal reflection at the major outer surface and is incident on a first optical expansion configuration comprising a set of partially reflective surfaces (interchangeably referred to as "facets") that are parallel to each other and obliquely inclined to the propagation direction of the image light, wherein each successive facet deflects a portion of the image light into a deflection direction that is also captured / guided within the substrate by internal reflection. Figure 1 8, but is located in region 10 of LOE 8. This partial reflection at successive facets expands the optical aperture of POD 5 in a first dimension (referred to as the "lateral" dimension), where the first dimension corresponds to the direction of elongation of region 10. In other words, this partial reflection at successive facets achieves an optical aperture expansion in the first dimension.

[0048] In a first set of preferred but non-limiting examples of the present disclosure, the above-mentioned set of facets are orthogonal to the major outer surface of the substrate. In this case, both the injected image and its conjugate that undergoes internal reflection when propagating within the region 10 are deflected and become conjugate images propagating in the deflected direction. In an alternative set of preferred but non-limiting examples, the first set of partially reflective surfaces is angled obliquely relative to the major outer surface of the LOE 8. In the latter case, the injected image or its conjugate forms the desired deflected image propagating within the LOE 8, while other reflections can be minimized, for example, by employing an angle-selective coating on the facet that makes the facet relatively transparent to the range of incident angles presented by the image for which reflection is not desired.

[0049] The first set of partially reflective surfaces deflects image illumination from region 10 (wherein the image illumination propagates in a first direction of propagation and is captured within the substrate by total internal reflection (TIR)) to region 15, where the image illumination propagates in a second direction of propagation and is also captured within the substrate by TIR. Region 15 has an intermediate optical expansion configuration, the details of which will be described later, which deflects image illumination propagating from region 10 to region 15 (wherein the image illumination propagates in the second direction) to region 20, and also expands the optical aperture in the first dimension, where the image illumination propagates in another direction of propagation and is also captured within the substrate by TIR. Region 20 contains a second optical expansion configuration, which is an optical outcoupling device implemented as another set of partially reflective facets that gradually couples a portion of the image illumination out toward the eye of an observer located within a region defined as an eye-motion box (EMB), thereby achieving optical aperture expansion in a second dimension.

[0050] Each of the LOE regions may be formed as a distinct substrate, or may be a continuation of a single substrate. For example, in a preferred but non-limiting implementation, three regions, region 10, region 15, region 20, are contained within a single substrate. Regardless of the implementation, a pair of major outer surfaces of the LOE 8 extends across the three regions, region 10, region 15, region 20, such that both sets of partially reflective surfaces are located between the major outer surfaces. Depending on the particular implementation, the intermediate optical expansion configuration may have components located between the major outer surfaces, or may have components located on one or both of the major outer surfaces.

[0051] With respect to the size of the aperture of POD 5 and the coupling arrangement, these can be achieved to sufficiently "fill" the thickness of LOE 8 with the image illumination to achieve lateral uniformity of the viewed image. However, this typically requires an aperture of approximately twice the size of the input aperture of LOE 8. In order to minimize the size of POD 5 (particularly the lateral dimension of POD 5), it may be preferred to provide a reduced size projector aperture that does not achieve filling of LOE 8. In this case, the facets in region 10 can be configured so that the first dimension aperture expansion achieved by the facets is a partial expansion, i.e., the deflected illumination is not uniform in the first (lateral) dimension. High uniformity of the output image in the lateral dimension can be achieved by an intermediate optical expansion configuration (in region 15) which completes the lateral expansion of the image performed by the facets in region 10 and produces a uniform image in the lateral dimension.

[0052] like Figure 1 As shown, the entire device 1 can be implemented with a pair of optical systems 2 (one for each eye) and preferably supported relative to the head of a user (also referred to as a "viewer"), wherein each LOE 8 faces a corresponding eye of the user. In a particularly preferred option as shown here, the support means is implemented as an eyeglass frame with a side (or "arm") 50 for supporting the device 1 relative to the user's ear so that one of the main outer surfaces is in facing relationship with the user's eye. Other forms of support means may also be used, including but not limited to headbands, masks or devices suspended from helmets.

[0053] Reference is made herein to the drawings and to the Y-axis ( Figure 1 ), and perpendicular to the Y axis (i.e., Figure 1 An X-axis extending vertically in the image.

[0054] In very approximate terms, the region 10 can be considered to achieve an aperture expansion in the Y direction (which is the so-called first (lateral) dimension, which coincides with the direction of elongation of the region 10), while the region 20 achieves an aperture expansion in the X direction (which is the so-called second (vertical) dimension). The details of the expansion in the angular direction in which the different parts of the field of view propagate will be expressed more precisely below. It should be noted that Figure 1 The orientation shown may be considered a "top-down" implementation, where image illumination into the main region (region) of the LOE enters from the top edge. However, other implementations (e.g., "side injection" implementations, where an axis referred to herein as the Y-axis is disposed vertically) or other intermediate orientations are also contemplated herein and fall within the scope of the present disclosure unless expressly excluded.

[0055] The POD 5 employed with the device 1 of the present disclosure is preferably configured to generate a collimated image, that is, the light of each image pixel in the collimated image is a parallel beam collimated to infinity with an angular direction corresponding to the pixel position. Therefore, the image illumination spans an angular range corresponding to the two-dimensional angular field of view. The POD 5 includes at least one light source, which is typically deployed to illuminate a spatial light modulator such as an LCOS chip. The spatial light modulator modulates the projection intensity of each pixel of the image to generate an image. Alternatively, the image projector may include a scanning device, typically implemented using a fast scanning mirror, that scans the illumination from a laser light source across the image plane of the projector, while synchronously changing the intensity of the light beam on a pixel-by-pixel basis with the movement, thereby projecting the desired intensity for each pixel. In both cases, a collimating optical device is provided to generate an output projection image that is collimated to infinity. Some or all of the above components are typically arranged on the surface of one or more polarizing beam splitters (PBS) cubes or other prism devices known in the art.

[0056] It will be appreciated that the near-eye display 1 includes various additional components, typically including a controller 45 for actuating the image projector 5, typically using power from a small on-board battery (not shown) or some other suitable power source. It will be appreciated that the controller 40 includes all necessary electronic components for driving the image projector, such as at least one processor or processing circuitry, all of which are known in the art.

[0057] Now go to Figure 2A and Figure 2B , showing in more detail the optical characteristics of an embodiment of a near-eye display. Specifically, a more detailed view of a light-guiding optical element (LOE) 8 formed of a transparent material is shown, the LOE including: a region 10, which includes a first optical aperture expansion configuration, the first optical aperture expansion configuration including a set of mutually parallel partially reflective surfaces (facets) 12 having a certain orientation; and a region 20, which includes a second optical aperture expansion configuration, the second optical aperture expansion configuration including a set of mutually parallel partially reflective surfaces (facets) 22 having an orientation that is not parallel to the orientation of the facets 12. The LOE 8 also includes an intermediate region 15, which is between the two regions, namely the region 10 and the region 20, and has or includes an intermediate optical aperture expansion configuration 16.

[0058] A set of mutually parallel major outer surfaces s1 and s2 extend across regions 10, 15, and 20, such that two sets of partially reflective surfaces 12 and 22 are located between major outer surfaces s1 and s2. In the illustrated embodiment, the set of major outer surfaces s1 and s2 are pairs of surfaces that are entirely continuous across regions 10 and 20, respectively, but options for reduced or increased thickness between regions 10 and 20 also fall within the scope of the present disclosure. Each of the pairs of adjacent regions 10 and 15 and pairs of adjacent regions 15 and 20 may be juxtaposed immediately so that they touch at a boundary, which may be a straight boundary or some other form of boundary, or, depending on the particular application, one or more additional LOE regions may be present between the regions to provide various additional optical or mechanical functions.

[0059] The near-eye display is designed to present a full field of view of the projected image from the POD 5 to the user's eye, which is located somewhere within a range of allowed positions specified by the "eye box" (EMB) 35 (i.e., a shape generally represented as a rectangle, spaced from the plane of the LOE, from which the pupil will view the projected image). The optical properties of the LOE 8 can be better understood by tracing the image illumination path from the POD 5 to the EMB 35.

[0060] The POD 5 injects the light beam 22 into the LOE 8 at the coupling region 9 of the LOE 8 through a suitable coupling device (which, as mentioned previously, may be a coupling prism, a coupling reflector, etc.). As discussed above, the image illumination produced by the POD 5 spans an angular range corresponding to a two-dimensional angular field of view, wherein each angular direction corresponds to a pixel position. Thus, the light beam 22 represents a plurality of light beams that make up a collimated image.

[0061] An injected light beam (image illumination) 22 propagates in the LOE 8 by internal reflection at the major outer surfaces s1 and s2. As the light beam 22 propagates in the LOE 8, it enters the region 10 from the region 9 of the LOE 8 and encounters partially reflective surfaces 12 embedded between the major outer surfaces s1 and s2. These partially reflective surfaces 12 are oriented so that a portion of the image illumination 22 propagating within the LOE 8 by internal reflection at the major outer surfaces s1 and s2 from the coupling region 9 of the LOE 8 is deflected to enter the region 15. In principle, the partially reflective surfaces 12 reflect multiple light beams originating from the light beam 22, but for clarity of illustration, the partially reflective surfaces 12 are used to deflect the image illumination 22 from the coupling region 9 of the LOE 8. Figure 2A and Figure 2B Only one of the deflected / reflected beams, denoted as beam 24, is shown in FIG. The deflection of the image illumination causes the image illumination to be deflected from a first propagation direction to a second propagation direction and causes the original optical aperture defined by the POD 5 to expand in a first (lateral) dimension.

[0062] The region 15 includes an intermediate optical aperture expansion configuration 16 that diffracts a light beam 24 (discussed later) at approximately right angles. In the illustrated embodiment, the intermediate optical aperture expansion configuration 16 is implemented as a diffractive optical aperture expansion configuration having a diffractive optical element (DOE) 15A ( Figure 2B ) is embedded within the LOE 8 between the major outer surfaces s1 and s2, and in particular at a mid-plane of the LOE 8 parallel to the major outer surfaces s1 and s2. Therefore, the propagating beam 24 will encounter the DOE 15A twice in a single TIR round trip.

[0063] like Figure 2B As shown, beam 24 encounters DOE 15A, where a portion of beam 24 (i.e., a portion of the intensity of the beam) is diffracted into beam 26, and another portion of beam 24 continues as beam 28A. Diffracted beam 26 is reflected by TIR at major outer surfaces s1 and s2, so that it also encounters DOE 15A, where a portion of beam 26 is diffracted into beam 28B parallel to beam 28A. Beam 26 continues to produce additional parallel beams, which are not shown in the figure for clarity and simplicity. Figure 2A ) shows only one of the additional parallel beams (denoted as 28C). The set of parallel beams 28A, 28B, 28C, etc. is an expansion of the beam 24. This expansion is a two-dimensional expansion, i.e., an expansion in a first dimension (i.e., a transverse dimension, approximately in the Y direction) (e.g., Figure 2A ), and the expansion in the second dimension (i.e., the vertical dimension, approximately in the X direction) (as shown in Figure 2B 15A). The expansion in the lateral dimension is complementary to the lateral expansion performed by the partially reflective surface 12, so that the image illumination is uniform in the first dimension. Thus, in effect, the diffraction performed by the DOE 15A completes part of the lateral expansion imparted by the partially reflective surface 12.

[0064] DOE 15A performs two diffractions. Specifically, DOE 15A performs a first diffraction on light beam 24 (which propagates in the input direction) to redirect (deflect) light beam 24 into light beam 26 in a first direction (approximately at right angles) that is not parallel to the input direction, and performs a second diffraction on light beam 26 to redirect (deflect) light beam 26 into light beam 28B, light beam 28C, etc. in a second direction parallel to the input direction while expanding the illumination laterally. DOE 15A is implemented as a strong diffraction element, so that the diffraction performed to redirect (deflect) light beam 26 into light beam 28B, light beam 28C, etc. is a strong diffraction that allows DOE 15A to achieve expansion in the lateral dimension.

[0065] In addition to expanding the optical aperture, diffraction of image illumination 24 by intermediate optical aperture expansion configuration 16 also causes image illumination propagating in region 15 to be redirected (deflected) into region 20. Thus, light beams 28A, 28B, 28C, etc. generated by intermediate optical aperture expansion configuration 16 enter region 20, where light beams 28A, 28B, 28C, etc. continue to propagate through internal reflections at major outer surfaces s1 and s2. As light beams 28A, 28B, 28C, etc. propagate in region 20 of LOE 8, they encounter partially reflective surface 22 embedded between major outer surface s1 and major outer surface s2. These partially reflective surfaces 22 are oriented to be obliquely inclined with respect to the major outer surfaces s1 and s2 so that a portion of the image illumination propagated by internal reflection at the major outer surfaces s1 and s2 (i.e., a portion of the intensity of beam 28A, beam 28B, beam 28C, etc.) is deflected to couple out of the LOE 8 toward the EMB 35 as a beam 30. The deflection by the partially reflective surfaces 22 also causes the optical aperture defined by the POD 5 to expand in a second dimension (the vertical dimension, approximately in the X direction).

[0066] exist Figure 2A and Figure 2B In a practical implementation of the illustrated embodiment, DOE 15A should be designed to have a certain width and diffraction efficiency so that a large amount of energy (intensity) is transferred from beam 28A (which is a continuation of beam 24, also known as the zeroth order). In fact, it is preferred that more than 50% of the energy (intensity) is transferred from beam 28A to other parallel beams (e.g., beams 28B, 28C, etc.) generated by DOE 15A.

[0067] Note that the lateral spacing between the set of parallel beams 28A, 28B, 28C, etc. should be taken into account when designing the position of EMB 35. The position of EMB 35 is dictated by the position of region 20 (and more specifically partially reflective surface 22) relative to the other two portions / regions 10, 15 of LOE 8. In order for the near-eye display to provide a full field of view of the projected image from POD 5 to the user's eye, region 20 should be offset along the first (lateral) dimension (i.e., along the Y direction) relative to the other two regions, i.e., regions 10 and 15. For example, the central portion of region 20 (e.g., Figure 2A as a bisector passing through the region 20 in the X direction) can be relative to the central portion of the region 10 (for example, Figure 2A as a bisector passing through the region 10 in the X direction) and the central portion of the region 15 (e.g., Figure 2A as a bisector passing through the region 15 in the X direction) is laterally offset (in Figure 2AThe amount of lateral offset is based on the lateral spacing between beam 28A, beam 28B, beam 28C, etc. In particular, the offset should approximate the distance a beam travels through the intermediate optical aperture expansion configuration 16 until its intensity is approximately half (i.e., 50%) of its original intensity.

[0068] Figure 2A and Figure 2B The illustrated embodiment provides advantages in optical performance: the intermediate optical aperture expansion arrangement 16 performs aperture expansion in both the lateral and vertical dimensions, and the lateral spacing between the generated beams 28A, 28B, 28C, etc. is relatively small, thereby achieving a correspondingly relatively small lateral offset of region 20 relative to regions 10 and 15, which can result in a more compact optical device. However, it may be challenging to manufacture a substrate with a diffractive surface embedded within the substrate, particularly at the mid-plane of the substrate. In practice, it may be simpler to provide the diffractive element on a major outer surface of the substrate rather than at the mid-plane of the substrate.

[0069] Certain non-limiting embodiments of the present disclosure provide an intermediate optical aperture expansion configuration 16 having a diffractive device implemented as a diffractive element located on one of the main outer surfaces s1 or s2, which supports a simpler manufacturing process. Figures 1 to 2B , now refer to Figure 3A and Figure 3B , Figure 3A and Figure 3B An embodiment of a LOE 8 is shown in which the intermediate optical aperture expansion arrangement 16 has a diffractive device comprising a DOE 15U (e.g., as a surface relief grating) located on one of the major outer surfaces s1. The major outer surface s1 is arbitrarily referred to as the "top" or "upper" surface of the LOE 8. Note that the choice of surface s1 is arbitrary and the DOE could just as easily be located on the other major outer surface s2.

[0070] exist Figure 3A and Figure 3B In the embodiment shown, Figure 2A and Figure 2B Unlike the dual interaction in the illustrated embodiment, the guided beams 24 and 26 interact with the DOE 15U only once per TIR round trip. Thus, the lateral spacing between the deflected beams 28A, 28BT, 28CT, etc. is Figure 2A twice the spacing between beams 28A, 28B, 28C, etc., which may result in Figure 2A and Figure 2B The embodiment shown has a smaller uniformity in the lateral dimension than that shown. Figure 3AAs shown, this increase in lateral spacing dictates a greater aperture offset to accommodate placement of the EMB, whereby the region 20 and partially reflective surface 22 are aligned with the Figure 2A is further shifted upwards in the Y direction compared to its counterpart in .

[0071] In addition, due to Figure 3A and Figure 3B The intermediate optical aperture expansion configuration 16 includes a DOE 15U deployed on only one main outer surface s1 among the main outer surfaces, so that the intermediate optical aperture expansion configuration 16 only produces lateral beam multiplication, that is, the intermediate optical aperture expansion configuration 16 only realizes the optical aperture expansion in the first (lateral) dimension, but does not realize the optical aperture expansion in the second (vertical) dimension.

[0072] To achieve both lateral and longitudinal optical aperture expansion as well as tighter lateral spacing between light beams, a second DOE may be positioned on the other major outer surface. Figure 4 An embodiment is shown whereby the diffractive device of the intermediate optical aperture expansion configuration 16 includes a second DOE 15D located on a major outer surface s2, such that the two DOEs 15U and DOE 15D are parallel gratings due to their deployment on parallel surfaces s1 and s2, and therefore the two DOEs 15U and DOE 15D have the same grating orientation and spacing. The major outer surface s2 is arbitrarily referred to as the "bottom" surface or "lower" surface of the LOE 8. In the illustrated embodiment, the DOE 15D is located at the major outer surface s2 as a surface engraved grating. Due to the use of parallel DOEs 15U and DOE 15D, the beams 24 and 26 encounter the diffractive device of the intermediate optical aperture expansion configuration 16 twice in a single TIR round trip, resulting in a tighter lateral spacing of the parallel beams (beams 28A, beams 28BU, etc.) than in Figure 2A and Figure 2B The spacing achieved in the embodiments shown in FIG. 1 is the same or similar. Therefore, Figure 4 The intermediate optical aperture expansion arrangement 16 in the embodiment shown in FIG. 1 is functionally equivalent to the embodiment shown in FIG. 1 for all intents and purposes. Figure 2A and Figure 2B The intermediate optical aperture expansion arrangement 16 in the illustrated embodiment is also shown and may be simpler to manufacture.

[0073] As mentioned above, the intermediate optical aperture expansion arrangement 16 performs redirection (deflection) of the input light beam at approximately right angles. The variation of the deflection angle (i.e., the dispersion) is spectrally dependent, i.e., different color components of the image illumination will be deflected at different angles. In fact, the dispersion of the diffracted light beam dictates the shape and size of the diffractive elements of the intermediate optical aperture expansion arrangement 16. With this in mind, reference is now made to Figure 5 , Figure 5DOE 15A ( Figure 2A ) deflects the different color components of the input image illumination (beam) 24. Initially, the beam 24 includes the entire spectrum of colors of the image (e.g., red, green, and blue). Figure 2B DOE 15A can be designed to redirect (deflect) a first color (e.g., green) (also referred to as first order) of light beam 24 at a right angle (i.e., 90°) (indicated as light beam 26G). Thus, DOE 15A deflects a second color (e.g., blue) of light beam 24 to an angle slightly less than a right angle (in this context, "slightly less" means about 20% less than a right angle, i.e., about 70°) (indicated as light beam 26B), and deflects a third color (e.g., red) of light beam 24 to an angle slightly greater than a right angle (in this context, "slightly greater" means about 20% less than a right angle, i.e., about 110°).

[0074] The interaction length of the deflected beam can dictate the width (measured in the X direction) of region 15. In particular, the width of region 15 can be designed based on the interaction length of beam 24 required to deflect approximately 50% of the intensity to beam 26, and the interaction lengths of beams 26R and 26B required to minimize residual leakage 26RL and 26BL, respectively.

[0075] The improved interaction efficiency (i.e., shorter interaction lengths for all color components) can be determined by the shape of the diffractive optical element. Figure 2A and Figure 2B The configuration relies on a single DOE 15A and is therefore different from the configuration using a pair of DOE 15U and DOE 15D. Figure 4 Compared to the configuration of the DOE 15D, there are inherently fewer degrees of freedom in the diffractive element design. In some embodiments, one of the DOEs 15D can be optimized to diffract the first color component and the second color component of the image illumination (e.g., green and red), and the other DOE 15U can be optimized to diffract the third color component and the first color component of the image illumination (e.g., blue and green). The optimization is based on maintaining the same periodicity (relief grating spacing and orientation) on both DOE 15U and DOE 15D, but having different grating shapes (e.g., different grating depths) optimized for different spectral regions (red-green and blue-green).

[0076] Although the embodiments discussed thus far relate to region 15 having an intermediate optical aperture expansion configuration implemented as a diffractive optical aperture expansion configuration, other embodiments are contemplated herein in which the intermediate optical aperture expansion configuration is implemented as a non-diffractive device similar to the devices of the optical aperture expansion configurations of regions 10 and 20. Figure 6One such embodiment is schematically shown in which the intermediate optical aperture expansion configuration 16 is implemented as mutually parallel partially reflective surfaces (facets) 40 of another set of planes embedded between the main outer surface s1 and the main outer surface s2 and having an orientation that is non-parallel to the orientation of the facet 22. The third orientation of the facet 40 can be parallel or non-parallel to the orientation of the facet 12. The facet 40 performs a function similar to the above-mentioned diffraction element in that the facet 40 deflects the light beam 26 at an approximately right angle and returns to the parallel light beam 28, which completes the lateral expansion of the optical aperture of the POD 5 imparted by the facet 12, so that the image illumination is uniform in the first (lateral) dimension. The facet 40 can be deployed perpendicular to the main outer surfaces s1 and s2 or inclined to the main outer surfaces s1 and s2. In such a configuration, all wavelengths (i.e., color components) of the light beam 26 are reflected in the same direction without dispersion. In addition, the higher reflectivity of the optical coating used to implement the facet 40 can achieve an even narrower area 15 (narrower when intercepted along the X direction).

[0077] In the embodiments described so far, the image illumination propagating from the coupling region 9 to the region 10 is captured in one dimension by internal reflections (also referred to as double internal reflections) at the major outer surfaces s1 and s2. However, other embodiments are envisioned in which the image illumination propagating from the coupling region 9 to the region 10 is captured in two dimensions. Figure 7 An embodiment of a LOE having a region 10 that supports capturing light in two dimensions is schematically shown. Here, the region 10 of the LOE 8 includes two pairs of mutually parallel planar main outer surfaces, namely, a first pair of surfaces s1 and s2 and a second pair of main outer surfaces s3 and s4. The two pairs of main outer surfaces s1, s2, s3, s4 form a rectangular cross-section (which is the XZ plane in this configuration). In this embodiment, the coupling device is such that: when the POD 5 injects the image illumination into the LOE 8 at the coupling region with an initial propagation direction at a coupling angle that is inclined to the first pair of main outer surfaces s1, s2 and the second pair of main outer surfaces s3, s4, the image illumination advances along the region 10 by quadruple internal reflection. The region 10 has an elongation direction, which in this configuration is perpendicular to both the Z direction and the X direction, and the small facets ( Figure 7) is obliquely inclined to the elongation direction. In this embodiment, the first pair of major outer surfaces s1 and s2 are still continuous across the other two regions 15 and 20 of the LOE 8, each of which supports the propagation of light through double internal reflection at the major outer surfaces s1 and s2, as in the previously described embodiments. Further details of such a light-guiding optical element can be found in various commonly owned patent documents (including U.S. Patent No. 10,133,070) (the entire contents of these patent documents are incorporated herein by reference), which light-guiding optical element: has a first portion / region that supports the propagation of light through quadruple internal reflection and has a group of obliquely inclined parallel partial reflectors that gradually couple the image light out of the first portion / region; and has or is optically coupled to a second portion / region that supports the propagation of image light through double internal reflection and gradually couples the image light to the user's eyes via a group of parallel partial reflectors.

[0078] It should be noted that in all of the configurations described herein, image illumination propagating within the LOE does not propagate parallel to any major exterior surface of the LOE, nor parallel to any interacting facets.

[0079] Although the embodiments described thus far relate to an optical system having an LOE that directs image illumination to an eye, the optical system may be replicated to support a binocular configuration, and embodiments in which pairs of LOEs, each directing image illumination to a corresponding eye, form part of a single overall optical system are also within the scope of the present disclosure and the appended claims. Figure 1 The described embodiments relate to binocular devices carrying a pair of optical systems, one for each eye, each carrying a respective LOE for directing image illumination to the corresponding eye, but the scope of the present disclosure should not be limited to binocular devices. Devices having an optical system with a LOE for directing image illumination to only a single eye (which is a monocular device) also fall within the scope of the present disclosure and the appended claims.

[0080] The description of various embodiments of the present disclosure has been presented for illustrative purposes, but the description is not intended to be exhaustive or limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terms used herein are selected to best illustrate the principles of the embodiments, practical applications, or technical improvements over technologies found on the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

[0081] As used herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0082] The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any implementation described as “exemplary” is not necessarily to be construed as preferred or advantageous over other implementations and / or to exclude incorporation of features from other implementations.

[0083] It should be appreciated that certain features of the disclosure described in the context of separate embodiments for clarity may also be provided in combination in a single embodiment. Conversely, various features of the disclosure described in the context of a single embodiment for brevity may also be provided individually or in any suitable subcombination or as appropriate in any other described embodiment of the disclosure. Certain features described in the context of various embodiments should not be considered essential features of those embodiments unless the embodiment is inoperable without those elements.

[0084] To the extent that the appended claims are drafted without multiple references, this is done solely to accommodate formal requirements in jurisdictions that do not permit such multiple references. It should be noted that all possible combinations of features that would be implied by making the claims multiple references are expressly contemplated and should be considered part of the present disclosure.

[0085] Although the present disclosure has been described in conjunction with the specific embodiments of the present disclosure, it is apparent that many alternatives, modifications and variations will be apparent to those skilled in the art. Therefore, the present invention is intended to include all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.

Claims

1. A light guide optical element (LOE) for directing image illumination from an image projector to an eye box for viewing by an eye of a user, the LOE being formed of a transparent material and comprising: a first region comprising a first optical aperture expansion configuration including a first set of planar mutually parallel partially reflective surfaces having a first orientation; a second region comprising a second optical aperture expansion configuration including a second set of planar mutually parallel partially reflective surfaces having a second orientation that is non-parallel to the first orientation; an intermediate region, located between the first region and the second region, having a diffractive optical aperture expansion configuration including at least one diffractive element; as well as a pair of mutually parallel major exterior surfaces extending across the first region and the second region such that both the first set of partially reflective surfaces and the second set of partially reflective surfaces are located between the major exterior surfaces, the image illumination from the image projector being propagated by internal reflections at the major exterior surfaces, wherein the optical aperture expansion configuration is configured such that, Image illumination injected into the LOE and propagating through internal reflection at the major outer surface is deflected by the first optical aperture expansion configuration to the intermediate region to expand the optical aperture of the image projector in a first dimension, in the intermediate region, the image illumination is deflected by the diffractive optical aperture expansion configuration to the second region to further expand the optical aperture of the image projector in the first dimension, and in the second region, the image illumination is deflected by the second optical aperture expansion configuration so that the image illumination is coupled out of the LOE toward the eye box and the optical aperture of the image projector is expanded in a second dimension.

2. The LOE according to claim 1, wherein The diffractive optical aperture expansion configuration is configured to expand the optical aperture of the image projector in the second dimension.

3. The LOE according to claim 1, wherein: The at least one diffractive element is located at a mid-plane of the LOE parallel to the major outer surface.

4. The LOE according to claim 1, wherein: The at least one diffractive element is configured to deflect a first color of the image illumination at a right angle, a second color of the image illumination at a slightly less than right angle, and a third color of the image illumination at a slightly greater than right angle.

5. The LOE according to claim 1, wherein: The at least one diffractive element is located at one of the major outer surfaces.

6. The LOE according to claim 5, wherein: The at least one diffractive element is located as a surface relief grating at one of the major outer surfaces.

7. The LOE according to claim 1, wherein: The at least one diffractive element includes a first diffractive element located at a first one of the major outer surfaces and a second diffractive element located at a second one of the major outer surfaces.

8. The LOE according to claim 7, wherein: The first diffractive element is located at the first of the major outer surfaces as a first surface relief grating, and wherein the second diffractive element is located at the second of the major outer surfaces as a second surface relief grating.

9. The LOE according to claim 7, wherein: The first diffraction element and the second diffraction element have the same grating orientation and pitch.

10. The LOE according to claim 7, wherein: The first diffractive element is configured to diffract image illumination of a first color and image illumination of a second color, and wherein the second diffractive element is configured to diffract image illumination of the first color and image illumination of a third color.

11. The LOE according to claim 7, wherein: The first diffraction element and the second diffraction element have the same grating orientation and pitch, but different grating shapes.

12. The LOE of claim 1, wherein: The diffractive optical aperture expansion arrangement is configured to deflect image illumination propagating by internal reflection between the major outer surfaces from the third region to the second region at approximately a right angle.

13. The LOE of claim 1, wherein: The second region is offset relative to the first region and the intermediate region along the first dimension.

14. The LOE of claim 1, wherein: Image illumination propagates in the intermediate region by total internal reflection (TIR) ​​between the major outer surfaces and encounters the diffractive optical aperture expansion configuration twice in a single TIR round trip.

15. The LOE of claim 1, wherein: Image illumination propagates in the intermediate region by total internal reflection (TIR) ​​between the major outer surfaces and encounters the diffractive optical aperture expansion configuration once in a single TIR round trip.

16. The LOE of claim 1 further comprising a second pair of mutually parallel major exterior surfaces forming a rectangular cross-section at the first region such that the image illumination injected into the LOE advances through the first region by quadruple internal reflection at the two pairs of major exterior surfaces.

17. An optical system for directing image illumination to an eye box for viewing by an eye of a user, the optical system comprising: an image projector having an optical aperture and configured to project image illumination corresponding to the collimated image; as well as a light guide optical element (LOE) formed of a transparent material and optically coupled to the image projector, the LOE comprising: a first major outer surface and a second major outer surface, the first major outer surface and the second major outer surface being parallel to each other, the image illumination from the image projector propagating by internal reflections at the major outer surfaces, a first region, the first region comprising a first optical aperture expansion configuration, the first optical aperture expansion configuration comprising a first set of planar mutually parallel partially reflective surfaces having a first orientation, a second region comprising a second optical aperture expansion configuration including a second set of planar mutually parallel partially reflective surfaces having a second orientation that is non-parallel to the first orientation, and an intermediate region, located between the first region and the second region, having a diffractive optical aperture expansion configuration including a first diffractive element and a second diffractive element, wherein the first diffractive element is located at the first main outer surface and the second diffractive element is located at the second main outer surface, such that the first diffractive element and the second diffractive element are parallel, wherein the major outer surface extends across the first region and the second region such that both the first set of partially reflective surfaces and the second set of partially reflective surfaces are located between the major outer surface, and wherein the optical aperture expansion configuration is configured such that, Image illumination injected into the LOE and propagating through internal reflection at the major outer surface is deflected by the first optical aperture expansion configuration to the intermediate region to expand the optical aperture of the image projector in a first dimension, in the intermediate region, the image illumination is deflected by the diffractive optical aperture expansion configuration to the second region to further expand the optical aperture of the image projector in the first dimension, and in the second region, the image illumination is deflected by the second optical aperture expansion configuration so that the image illumination is coupled out of the LOE toward the eye box and the optical aperture of the image projector is expanded in a second dimension.

18. A light guide optical element (LOE) for directing image illumination from an image projector to an eye box for viewing by an eye of a user, the LOE being formed of a transparent material and comprising: a first region comprising a first set of planar mutually parallel partially reflective surfaces; a second region comprising a second set of planar mutually parallel partially reflective surfaces; a third region comprising a third set of planar mutually parallel partially reflective surfaces; as well as a pair of mutually parallel major exterior surfaces extending across the first region, the second region, and the third region such that a first set of partially reflective surfaces, a second set of partially reflective surfaces, and a third set of partially reflective surfaces are located between the major exterior surfaces, the image illumination from the image projector being propagated by internal reflections at the major exterior surfaces, wherein the third group of partially reflective surfaces is oriented non-parallel to the first group of partially reflective surfaces, and wherein the second group of partially reflective surfaces is oriented non-parallel to the third group of partially reflective surfaces, and wherein the first group of partially reflective surfaces, the second group of partially reflective surfaces, and the third group of partially reflective surfaces are configured such that, Image illumination injected into the LOE that propagates through internal reflection at the major outer surface is deflected by the first group of partially reflective surfaces to the second region to expand the optical aperture of the image projector in a first dimension, in the second region, the image illumination is deflected by the second group of partially reflective surfaces to a third region to further expand the optical aperture of the image projector in the first dimension, and in the third region, the image illumination is deflected by the third group of partially reflective surfaces such that the image illumination is coupled out of the LOE toward the eye box and the optical aperture of the image projector is expanded in a second dimension.

19. The LOE according to claim 18, wherein: The second set of partially reflective surfaces is perpendicular to the main exterior surface.

20. The LOE of claim 18, wherein: The second set of partially reflective surfaces are inclined relative to the main outer surface.

Images