WAVEGUIDE COMBINER WITH IN-PLANE RELAY AND WAVEGUIDE DISPLAY SYSTEM INCLUDING THE SAME

A system includes a waveguide configured to guide an in-coupled image light to propagate inside the waveguide via total internal reflection. The system also includes an in-coupling element configured to couple an input image light into the waveguide as the in-coupled image light. The system also includes a plurality of partial reflectors at least partially embedded inside the waveguide. The system further includes an in-plane relay at least partially embedded inside the waveguide and disposed between the in-coupling element and the partial reflectors. The in-plane relay includes a plurality of cylindrical reflectors. The in-plane relay is configured to convert the in-coupled image light received from the in-coupling element into a relayed image light.

TECHNICAL FIELD

The present disclosure generally relates to optical devices and systems, more specifically, to a waveguide combiner with an in-plane relay and a waveguide display system including the same.

BACKGROUND

An artificial reality system, such as a head-mounted display (“HMD”) or heads-up display (“HUD”) system, generally includes a near-eye display (“NED”) system in the form of a headset or a pair of glasses. The NED system is configured to present content to a user via an electronic or optic display within, for example, about 10-20 mm in front of the eyes of a user. The NED system may display virtual objects or combine images of real objects with virtual objects, as in VR, AR, or MR applications. For example, in an AR or MR system, a user may view both images of virtual objects (e.g., computer-generated images (“CGIs”)) and the surrounding environment by, for example, seeing through transparent display glasses or lenses.

One example of an AR system may include a pupil-expansion waveguide display system, in which an image light representing a CGI may be coupled into a waveguide, propagate within the waveguide via totally internal reflection, and be coupled out of the waveguide at different locations to expand an effective pupil. The waveguide may also combine the image light representing the CGI and a light from a real-world environment, such that the virtual image may be superimposed with real-world images.

SUMMARY OF THE DISCLOSURE

According to an aspect of the present disclosure, a system is provided. The system includes a waveguide configured to guide an in-coupled image light to propagate inside the waveguide via total internal reflection. The system also includes an in-coupling element configured to couple an input image light into the waveguide as the in-coupled image light. The system also includes a plurality of partial reflectors at least partially embedded inside the waveguide. The system further includes an in-plane relay at least partially embedded inside the waveguide and disposed between the in-coupling element and the partial reflectors. The in-plane relay includes a plurality of cylindrical reflectors. The in-plane relay is configured to convert the in-coupled image light received from the in-coupling element into a relayed image light.

Other aspects of the present disclosure can be understood by those skilled in the art in light of the description, the claims, and the drawings of the present disclosure. The foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the claims.

DETAILED DESCRIPTION

Various aspects of the present disclosure will be described with reference to the accompanying drawings, which are merely examples for illustrative purposes and are not intended to limit the scope of the present disclosure. Wherever possible, the same reference numbers are used throughout the drawings to refer to the same or similar parts, and a detailed description thereof may be omitted.

As used herein, the terms “couple,” “coupled,” “coupling,” or the like may encompass an optical coupling, a mechanical coupling, an electrical coupling, an electromagnetic coupling, or any combination thereof. An “optical coupling” between two optical elements refers to a configuration in which the two optical elements are arranged in an optical series, and a light output from one optical element may be directly or indirectly received by the other optical element. An optical series refers to optical positioning of a plurality of optical elements in a light path, such that a light output from one optical element may be transmitted, reflected, diffracted, converted, modified, or otherwise processed or manipulated by one or more of other optical elements. In some embodiments, the sequence in which the plurality of optical elements are arranged may or may not affect an overall output of the plurality of optical elements. A coupling may be a direct coupling or an indirect coupling (e.g., coupling through an intermediate element).

The phrase “one or more” may be interpreted as “at least one.” The phrase “at least one of A or B” may encompass various combinations of A and B, such as A only, B only, or A and B. Likewise, the phrase “at least one of A, B, or C” may encompass various combinations of A, B, and C, such as A only, B only, C only, A and B, A and C, B and C, or A and B and C. The phrase “A and/or B” may be interpreted in a manner similar to that of the phrase “at least one of A or B.” For example, the phrase “A and/or B” may encompass various combinations of A and B, such as A only, B only, or A and B. Likewise, the phrase “A, B, and/or C” has a meaning similar to that of the phrase “at least one of A, B, or C.” For example, the phrase “A, B, and/or C” may encompass various combinations of A, B, and C, such as A only, B only, C only, A and B, A and C, B and C, or A and B and C.

When a first element is described as “attached,” “provided,” “formed,” “affixed,” “mounted,” “secured,” “connected,” “bonded,” “recorded,” or “disposed,” to, on, at, or at least partially in a second element, the first element may be “attached,” “provided,” “formed,” “affixed,” “mounted,” “secured,” “connected,” “bonded,” “recorded,” or “disposed,” to, on, at, or at least partially in the second element using any suitable mechanical or non-mechanical manner, such as depositing, coating, etching, bonding, gluing, screwing, press-fitting, snap-fitting, clamping, etc. In addition, the first element may be in direct contact with the second element, or there may be an intermediate element between the first element and the second element. The first element may be disposed at any suitable side of the second element, such as left, right, front, back, top, or bottom.

When the first element is shown or described as being disposed or arranged “on” the second element, term “on” is merely used to indicate an example relative orientation between the first element and the second element. The description may be based on a reference coordinate system shown in a figure, or may be based on a current view or example configuration shown in a figure. For example, when a view shown in a figure is described, the first element may be described as being disposed “on” the second element. It is understood that the term “on” may not necessarily imply that the first element is over the second element in the vertical, gravitational direction. For example, when the assembly of the first element and the second element is turned 180 degrees, the first element may be “under” the second element (or the second element may be “on” the first element). Thus, it is understood that when a figure shows that the first element is “on” the second element, the configuration is merely an illustrative example. The first element may be disposed or arranged at any suitable orientation relative to the second element (e.g., over or above the second element, below or under the second element, left to the second element, right to the second element, behind the second element, in front of the second element, etc.).

When the first element is described as being disposed “on” the second element, the first element may be directly or indirectly disposed on the second element. The first element being directly disposed on the second element indicates that no additional element is disposed between the first element and the second element. The first element being indirectly disposed on the second element indicates that one or more additional elements are disposed between the first element and the second element.

The term “film,” “layer,” “coating,” or “plate” may include rigid or flexible, self-supporting or free-standing film, layer, coating, or plate, which may be disposed on a supporting substrate or between substrates. The terms “film,” “layer,” “coating,” and “plate” may be interchangeable.

The term “orthogonal” as used in “orthogonal polarizations” or the term “orthogonally” as used in “orthogonally polarized” means that an inner product of two vectors representing the two polarizations is substantially zero. For example, two lights or beams with orthogonal polarizations (or two orthogonally polarized lights or beams) may be two linearly polarized lights (or beams) with two orthogonal polarization directions (e.g., an x-axis direction and a y-axis direction in a Cartesian coordinate system) or two circularly polarized lights with opposite handednesses (e.g., a left-handed circularly polarized light and a right-handed circularly polarized light).

FIGS.1A and1Billustrate x-z sectional views of a conventional geometrical waveguide display system100(also referred to as system100, or waveguide display system100).FIG.1Cillustrates an x-y sectional views of the system100shown inFIGS.1A and1B. The system100may include a light source assembly (not shown), a waveguide110, an in-coupling mirror135, an array of folding mirrors140(shown inFIG.1C), and an array of out-coupling mirrors145. The in-coupling mirror135, the folding mirrors140, and the out-coupling mirrors145may be embedded inside different portions of the waveguide110. The in-coupling mirror135may be a highly reflective mirror. The folding mirrors140in the array may be arranged in parallel along a first direction, e.g., a y-axis direction. The out-coupling mirrors145in the array may be arranged in parallel along a second direction, e.g., an x-axis direction. Each of the folding mirror140and the out-coupling mirror145may be a facet including a flat partial reflective surface, which reflects a portion of an incident light as a reflected light and transmits the remaining portion of the incident light as a transmitted light. The flat partial reflective surface may not change the degree of the divergence or the degree of the convergence of the light while reflecting and transmitting the light. The flat partial reflective surfaces of the folding mirrors140in the array may be arranged in parallel with one another, and the flat partial reflective surfaces of the out-coupling mirrors145in the array may be arranged in parallel with one another.

The light source assembly may emit an image light (referred to as an input image light)130representing a virtual image toward the waveguide110. The input image light130may be a divergent image light that includes a plurality of bundles of parallel rays.FIG.1Aillustrates an optical path of the input image light130inside the system100, andFIG.1Billustrates an optical path of a single bundle of parallel rays130bin the input image light130inside the system100. The waveguide110including the in-coupling mirror135, the folding mirrors140, and the out-coupling mirrors145may guide or deliver the divergent input image light130(that is formed by a plurality of bundles of parallel rays) as a plurality of divergent output image lights132(each image light132is formed by a plurality of bundles of parallel rays) propagating toward an eye-box region159. An eye160of a user of the system100may be positioned within the eye-box region159to perceive the virtual image. In addition, the waveguide110may also receive a light from a real-world environment (referred to as a real-world light), and may combine the real-world light with the output image lights132, and deliver the combined light to the eye-box region159. Thus, the waveguide110including the multiple embedded mirrors may also be referred to as a geometric waveguide combiner or an image combiner.

As shown inFIGS.1A-1C, the in-coupling mirror135may couple the input image light130into the waveguide110as an in-coupled image light131propagating inside the waveguide110via total internal reflection (“TIR”) toward the array of folding mirrors140. As shown inFIG.1C, the in-coupled image light131, which is a divergent image light, may be incident onto the folding mirror140. Each folding mirror140may reflect a portion of the in-coupled image light131as a redirected image light131a(indicated by dashed arrows) propagating toward the array of out-coupling mirrors145, and transmit the remaining portion of the in-coupled image light131for further TIR propagation toward a next folding mirror140. The redirected image light131amay be a divergent image light. Thus, the array of folding mirrors140may split the in-coupled image light131into a plurality of divergent redirected image lights131a(indicated by dashed arrows inFIG.1C) propagating toward the array of out-coupling mirrors145, thereby expanding the input image light130in the first direction (e.g., the y-axis direction). For discussion purposes,FIG.1Cshows five redirected image lights131a(denoted by dashed arrows) propagating inside the waveguide110toward the array of out-coupling mirrors145.

Referring back toFIG.1A, when each of the divergent redirected image lights131amay be incident onto the out-coupling mirrors145, each out-coupling mirror145may couple, via reflection, a portion of the redirected image light131aout of the waveguide110as an output image light132, and transmit the remaining portion of the redirected image light131afor further TIR propagation toward a next out-coupling mirror145. Thus, each redirected image light131amay be reflected by the array of out-coupling mirrors145as a plurality of output image lights132, and the array of out-coupling mirrors145may expand the input image light130in the second direction (e.g., the x-axis direction). For discussion purposes,FIG.1Amerely shows two output image lights132(from two out-coupling mirrors145), which may be divergent image lights. Thus, the waveguide110with the embedded out-coupling mirrors145and folding mirrors140may provide a 2D pupil replication at the output side of the waveguide110.

In addition, the rays in each bundle of the input image light130may remain parallel rays when propagating throughout the geometric waveguide combiner. For example,FIG.1Bshows that the in-coupling mirror135couples a bundle of parallel rays130bin the input image light130as a bundle of parallel rays131bin the in-coupled image light131. The array of folding mirrors140and the array of out-coupling mirrors145may convert the bundle of parallel rays131binto a plurality of bundles (e.g., two) of parallel rays132bof the output image lights132.

The conventional waveguide display system100shown inFIGS.1A-1Cmay have a low eye-box efficiency (e.g., below 5%) due to the layout waste, and the face illumination waste. The eye-box efficiency is a ratio between the energy received by the eye-box region159and the energy output by a display element (e.g., projector) included in the light source assembly. FIG.1B shows the layout waste in the system100, andFIG.1Ashows the face illumination waste in the system100. As shown inFIG.1B, when the redirected image lights131a, which may be divergent image lights, are incident onto the array of out-coupling mirrors145, some of the redirected image lights131amay not be received by the array of out-coupling mirrors145, and may be lost. As shown inFIG.1A, when the redirected image lights131aare incident onto the array of out-coupling mirrors145, the array of out-coupling mirrors145may reflect the redirected image lights131aas the divergent output image lights132propagating toward the eye-box region159. The size of the array of out-coupling mirrors145is often greater than the size of the eye-box region159. Thus, a portion of the output image lights132may propagate through the eye-box region159, and the remaining portion(s) of the output image lights132may be incident onto the face of the user, illuminating the face. Due to the layout waste and the face illumination waste, the eye-box efficiency of the conventional waveguide display system100may be as low as 2%-3%. That is, the conventional waveguide display system100may be power inefficient.

In view of the limitations in the conventional technologies, the present disclosure provides an optical waveguide combiner including an in-plane relay, and a display system configured to increase the eye-box efficiency via the in-plane relay.FIG.2Aillustrates a three-dimensional (“3D”) view of a geometrical waveguide display system200(referred to as system200for simplicity) configured to provide an improved eye-box efficiency (or optical efficiency), according to an example of the present disclosure. The system200may be implemented into an artificial reality device or system for VR, AR, and/or MR applications. As shown inFIG.2A, the system200may include a light source assembly205, a waveguide210, an in-coupling element235, a folding element240(also referred to as a redirecting element240), an out-coupling element245, and an in-plane relay250. In some examples, the in-coupling element235, the folding element240, the out-coupling element245, and the in-plane relay250may be at least partially (including fully) embedded inside different portions of the waveguide210. In some examples, the in-coupling element235may not be embedded inside the waveguide210, and may be disposed at (e.g., on) a surface of the waveguide210.

The light source assembly205may be configured to output an image light (also referred to as an input image light)230representing a virtual image. The waveguide210, together with the in-coupling element235, the folding element240, the out-coupling element245, and the in-plane relay250, may guide the propagation of the input image light230and output the input image light230as a plurality of output image lights232, which propagate toward an eye-box region259of the system200. The system200may provide an improved eye-box efficiency. The waveguide210may also transmit a light from a real-world environment (referred to as a real-world light) toward the eye-box region259, such that the virtual image represented by the output image lights232may be superimposed with a real-world image represented by the real-world light. Thus, the waveguide210, the in-coupling element235, the folding element240, the out-coupling element245, and the in-plane relay250may be collectively referred to as a waveguide combiner.

FIG.2Billustrates a diagram of the light source assembly205included in the system200shown inFIG.2A, according to an example of the present disclosure. As shown inFIG.2B, the light source assembly205may include a display element220(e.g., a projector) and a collimating lens225. The display element220may include a plurality of pixels221arranged in a pixel array, in which neighboring pixels221may be separated by, e.g., a black matrix222. The display element220may output an image light229, which includes a plurality of bundles of divergent rays output from the respective pixels221. For illustrative purposes,FIG.2Bshows that the display element220includes three pixels221, and three bundles229a,229b, and229cof divergent rays output from the three pixels221.

The collimating lens225may convert the bundles229a,229b, and229cof divergent rays in the image light229into bundles230a,230b, and230cof parallel rays in the input image light230. The respective bundles230a,230b, and230cof parallel rays in the input image light230may have different propagation directions, and may have different incidence angles at the waveguide210and the in-coupling element235. That is, the collimating lens225may transform or convert a linear distribution of the pixels221in the image light229into an angular distribution of the pixels in the input image light230. In other words, the collimating lens225may transform or convert the image light229carrying a virtual image in the linear domain into the input image light230carrying the same virtual image in the angular domain.

Referring toFIGS.2A-2B, the in-coupling element235may be at least partially (including fully) embedded inside a first portion (e.g., input portion) of the waveguide210. The in-coupling element235may be configured to couple the input image light230as an in-coupled image light231propagating inside the waveguide210via TIR. In some examples, the in-coupling element235may include a highly reflective mirror. The reflectance of the in-coupling element235may be greater than 95%. For discussion purposes, the in-coupling element235may be referred to as an in-coupling mirror235. The in-coupling mirror235may be configured to reflect the input image light230into a TIR propagation path inside the waveguide210. In particular, the in-coupling mirror235may couple the respective bundles230a,230b, and230cof parallel rays in the input image light230into the waveguide210as respective bundles of parallel rays in the in-coupled image light231. The in-coupled image light231may propagate inside the waveguide210via TIR, toward the in-plane relay250, the folding element240, and the out-coupling element245.

FIG.2Cillustrates an x-y sectional view of a portion of the system200shown inFIG.2A, according to an example of the present disclosure.FIG.2Dillustrates an x-z sectional view of a portion of the system200shown inFIG.2A, according to an example of the present disclosure. Referring toFIG.2AandFIG.2C, the in-plane relay250may be at least partially (including fully) embedded inside a second portion of the waveguide210, the folding element240may be at least partially (including fully) embedded inside a third portion of the waveguide210, and the out-coupling element245may be at least partially (including fully) embedded inside a fourth portion (e.g., an output portion) of the waveguide210. The second portion of the waveguide210where the in-plane relay250is at least partially (including fully) embedded may be located between the first portion where the in-coupling element235is at least partially (including fully) embedded and the third portion where the folding element240is at least partially (including fully) embedded.

As shown inFIG.2A, the in-plane relay250may include a pair of reflectors251and252optically coupled to one another. One or both of the reflectors251and252may be configured with a predetermined optical power (e.g., a positive or negative optical power). In some examples, one or both of the reflectors251and252may function as a cylindrical mirror having a high reflectance (e.g., greater than or equal to 95%). For discussion purposes, the reflectors251and252may also be referred to as a first cylindrical mirror251and a second cylindrical mirror252, respectively. Referring toFIG.2C, the cylindrical mirror251or252may include a reflective layer254aor254b(also referred to as reflective surface254aor254b), and a substrate255aor255bfor supporting and protecting the reflective layer254aor254b. In some examples, the cylindrical mirror251or252may not include the substrate255aor255b, and the reflective layer254aor254bmay have a sufficient rigidity, e.g., may be a free-standing layer. In some examples, when the cylindrical mirror251or252includes the substrate255aor255b, the substrate255aor255bmay include a cylindrical lens having a flat surface and a curved surface, and the reflective layer254aor254bmay be disposed at the curved surface of the substrate255aor255b.

In some examples, the cylindrical mirror251or252may have two orthogonal directions: an optical power direction and a non-optical-power direction. The optical power direction is a direction roughly along a curved length of the cylindrical mirror251or252, and is the axis with optical power. The non-optical-power direction is a direction along the length direction of the cylindrical mirror251or252without any optical power. The length of the cylindrical mirror251or252along the non-optical-power direction may extend without affecting the optical power of the cylindrical mirror251or252. InFIG.2C, the non-optical-power direction of the cylindrical mirror251or252may be along the thickness direction of the waveguide210, e.g., a z-axis direction shown inFIG.2C.

The curved surface of the substrate255aor255bshown inFIG.2Cmay be a suitable curved surface, such as a concave surface, a convex surface, or a freeform surface, etc. The cylindrical mirror251or252may be a suitable cylindrical mirror, such as a concave cylindrical mirror, a convex cylindrical mirror, or a freeform cylindrical mirror, etc. The curved surface of the cylindrical mirror251and the curved surface of the cylindrical mirror251may be arranged facing one another. For discussion purposes,FIG.2Cshow that both the and252are concave cylindrical mirrors (or focusing cylindrical mirrors), and the curved surfaces face one another, such that a light reflected by one curved surface (e.g., the curved surface of the cylindrical mirror251) may be received by the other curved surface (e.g., the curved surface of the cylindrical mirror252). In some examples, although not shown, one of the cylindrical mirrors251and252may include a concave cylindrical mirror, and the other of the cylindrical mirrors251and252may include a convex cylindrical mirror. The concave cylindrical mirror and the convex cylindrical mirror may be positioned or configured such that a light may be transmitted between the concave cylindrical mirror and the convex cylindrical mirror. In some examples, one of the reflectors251and252may be a cylindrical mirror, and the other of the reflectors251and252may be a flat mirror. The cylindrical mirror and the flat mirror may be positioned or configured such that a light may be transmitted between the cylindrical mirror and the flat cylindrical mirror.

The folding element240may include an array of partial reflectors240a, referred to as folding mirrors240afor discussion purposes. In some examples, one or more (e.g., each) of the folding mirrors240amay be a facet including a flat partial reflective surface. When a plurality of folding mirrors240aare facets including a plurality of flat partial reflective surfaces, the plurality of flat partial reflective surfaces may be arranged in parallel with one other, in a first direction (e.g., a y-axis direction shown inFIG.2AandFIG.2C). The flat partial reflective surface of a folding mirror240amay be titled by a first predetermined angle (e.g., 45°) with respect to the first direction (e.g., the y-axis direction).

Referring toFIG.2AandFIG.2D, the out-coupling element245may include an array of partial reflectors245a, referred to as out-coupling mirrors245afor discussion purposes. In some examples, one or more (e.g., each) of the out-coupling mirrors245amay be a facet including a flat partial reflective surface. When a plurality of out-coupling mirrors245aare facets including a plurality of flat partial reflective surfaces, the plurality of flat partial reflective surfaces may be arranged in parallel with one other, in a second direction (e.g., an x-axis direction shown inFIG.2AandFIG.2D). The flat partial reflective surface of an out-coupling mirror245amay form a second predetermined angle (e.g., an acute angle, e.g., 30°) with respect to the surface (e.g., a surface within an x-y plane) of the waveguide210.

Referring toFIGS.2C and2D, the partial reflector240aor245a(or partial reflective surface) may reflect a first portion of the in-coupled image light231incident onto the partial reflector240aor245a, and transmit a second portion of the in-coupled image light231. The reflectance and the transmittance of the partial reflector240aor245amay be configurable depending on different applications. For example, in some examples, the reflectance and the transmittance of the folding mirror240a(or out-coupling mirror245a) may be configured to be about 15% and 85%, respectively. The transmittance and reflectance of the folding mirror240amay be the same as or different from the transmittance and reflectance of the out-coupling mirror245a.

FIG.3Aillustrates an x-y sectional view of the in-plane relay250, showing an optical path of the in-coupled image light231throughout the in-plane relay250, according to an example of the present disclosure.FIG.3Billustrates an A-A′ sectional view of the in-plane relay250, showing an optical path of the in-coupled image light231throughout the in-plane relay250, according to an example of the present disclosure. As shown inFIG.3A, the in-coupled image light231may include a plurality of bundles231a,231b, and231cof parallel rays, which may be respectively converted from the bundles230a,230b, and230cof parallel rays in the input image light230via the in-coupling mirror235shown inFIGS.2A and2B.

Referring toFIG.3A, the in-coupled image light231may be incident onto the first cylindrical mirror251of the in-plane relay250as a divergent image light. The in-plane relay250may be configured to convert the in-coupled image light231into a relayed image light331. The in-plane relay250may convert the bundles231a,231b, and231cof parallel rays in the in-coupled image light231into bundles331a,331b, and331cof parallel rays of the relayed image light331, respectively. The relayed image light331may be incident onto the folding element240as a convergent image light.

For example, the first cylindrical mirror251may be configured to convert, via reflection, the in-coupled image light231into an image light333propagating inside the waveguide210toward the second cylindrical mirror252via TIR, as shown inFIG.3B. Referring back toFIG.3A, the first cylindrical mirror251may reflect the bundles231a,231b, and231cof parallel rays as bundles333a,333b, and333cof non-parallel rays of the image light333, respectively. The bundles333a,333b, and333cof non-parallel rays of the image light333may be converged (or focused) to respective points at a focal plane of the first cylindrical mirror251, then diverged (or defocused) toward the second cylindrical mirror252. The second cylindrical mirror252may convert, via reflection, the image light333into the relayed image light331propagating toward the folding element240. The second cylindrical mirror252may reflect the bundles333a,333b, and333cof non-parallel rays of the image light333as the bundles331a,331b, and331cof parallel rays of the relayed image light331, respectively.

In some examples, the in-plane relay250may be configured to relay the virtual image represented by the in-coupled image light231received from the in-coupling element235to an intermediate image plane369. In some examples, as shown inFIG.3A, the intermediate image plane369may be located at the fourth portion of the waveguide210where the out-coupling element245may be at least partially (including fully) embedded. In some examples, although not shown, the intermediate image plane369may be located at the third portion of the waveguide210where the folding element240may be at least partially (including fully) embedded. In some examples, although not shown, the intermediate image plane369may be located between the third portion of the waveguide210where the folding element240may be at least partially (including fully) embedded and the fourth portion of the waveguide210where the out-coupling element245may be at least partially (including fully) embedded. In some examples, although not shown, the intermediate image plane369may be located outside of the waveguide210. For example, the intermediate image plane369may be located at the eye-box region259, e.g., at an eye pupil258of an eye260of a user that is positioned in the eye-box region259. In some examples, the in-plane relay250may be configured to form an in-plane pupil relay optical assembly. In some examples, the in-plane relay250may be configured to form a suitable imaging assembly, such as a 4-f imaging assembly, a 2-f imaging assembly, a 1-f imaging assembly, or a 0.5-f imaging assembly, etc. In some examples, the in-plane relay250may also be configured to at least partially correct various optical aberrations in the in-coupled image light231.

FIG.3Amerely illustrates an exemplary positional relationship of the relayed image light331, the folding element240, and the out-coupling element245, and does not show the optical path of the relayed image light331throughout the folding element240and the out-coupling element245.FIGS.3C-3Eillustrate various sectional view of the waveguide210, showing an optical path of the relayed image light331throughout the folding element240and the out-coupling element245, according to an example of the present disclosure.FIG.3Cillustrates an x-y sectional view of the waveguide210, showing an optical path of a single ray in the relayed image light331throughout the folding element240.FIG.3Dillustrates an x-y sectional view of the waveguide210, showing an optical path of the relayed image light331throughout the folding element240.

As shown inFIGS.3C and3D, when the relayed image light331is incident onto the array of folding mirrors240a, one or more (e.g., each) of the folding mirrors240amay reflect a portion of the relayed image light331as a redirected image light335(indicated by a dashed arrow) propagating toward the out-coupling element245, and transmit the remaining portion of the relayed image light331for further TIR propagation toward a next folding mirror240a. Thus, the array of folding mirrors240amay split, via reflection, the relayed image light331into a plurality of redirected image lights335(indicated by dashed arrows) propagating toward the out-coupling element245, thereby expanding the input image light230in the first direction (e.g., the y-axis direction). For discussion purposes,FIG.3Dshows that the array of folding mirrors240asplits, via reflection, the relayed image light331into five redirected image lights335. The redirected image lights335may be incident onto the array of out-coupling mirrors245aas convergent image lights.

Compared to the conventional system100shown inFIG.1Bwhere the redirected image lights131aare incident onto the array of out-coupling mirrors145as divergent image lights, the amount of the redirected image lights335that are received by the array of out-coupling mirrors245afor being coupled out of the waveguide210may be increased, whereas the amount of the redirected image lights335that are not received by the array of out-coupling mirrors245amay be reduced. Thus, compared to the conventional system100shown inFIG.1B, the layout waste may be reduced in the system200shown inFIG.3D.

FIG.3Eillustrates an x-z sectional view of the waveguide210, showing an optical path of the relayed image light331(or the redirected image light335) throughout the out-coupling element245. As shown inFIG.3E, when a redirected image light335is incident onto the array of out-coupling mirrors245a, an out-coupling mirror245amay couple, via reflection, a portion of the redirected image light335out of the waveguide210as an output image light232, and transmit the remaining portion of the redirected image light335for further TIR propagation toward a next out-coupling mirror245a. Thus, the redirected image light335may be reflected by the array of out-coupling mirrors245aas a plurality of output image lights232, thereby expanding the input image light230in the second direction (e.g., the x-axis direction). The output image lights234may be distributed along both the first direction and the second direction. For discussion purposes,FIG.3Emerely illustrates three output image lights232distributed along the second direction, and two rays of the respective output image light232. Thus, the waveguide210with the at least partially embedded out-coupling element245and the at least partially embedded redirecting element240may provide a first beam expansion long the first direction and a second beam expansion long the second direction, thereby realizing the 2D pupil replication at the output side of the waveguide210.

The output image lights234may propagate toward a plurality of exit pupils257located within the eye-box region259of the waveguide display system200. An exit pupil257is a region in space where an eye pupil258of the eye260of a user is positioned in the eye-box region259to receive the content of a virtual image output from the display element. The exit pupils257may be arranged in a 2D array within the eye-box region259. The eye-box region259overlaps with all, or most, of the practical positions of the eye pupil258of the user. This feature, referred to as “pupil expansion,” creates the effect of a full real-life image as perceived by the user, rather than a moving eye pupil characteristic provided by other viewing instruments (e.g., binoculars, microscopes, or telescopes).

Further, when the redirected image light335is incident onto the array of out-coupling mirrors245aas a convergent image light, the output image lights232out-coupled from the array of out-coupling mirrors245amay initially propagate in a convergent manner and then diverge towards the eye-box region259. Compared to the conventional system100shown inFIG.1Awhere the redirected image lights131aare incident onto the array of out-coupling mirrors145as divergent image lights, and the output image lights132output from the array of out-coupling mirrors145propagate in a divergent manner towards the eye-box region159, the amount of the output image lights232that are received by the eye-box region259may be increased, whereas the amount of the output image lights232that illustrate the face of the user may be reduced. Thus, compared to the conventional system100shown inFIG.1A, the face illumination waste may be reduced in the system200shown inFIG.3E. Referring toFIGS.3A-3E, the layout waste and the face illumination waste may both be reduced in the system200including the in-plane relay250. As a result, the eye-box efficiency may be significantly increased. The eye-box efficiency of the system200may be increased by at least ten times as compared to the conventional system100shown inFIGS.1A-1C.

The system200shown inFIGS.2A-3Eis used as an example of geometric waveguide display systems for explaining the mechanisms and design principles to increase the eye-box efficiency. The arrangement of the various mirrors251,252,240a, and245aincluded in the system200shown inFIGS.2A-3Eare for illustrative purposes. In some examples, at least one of the in-coupling element235or the out-coupling element245may include one or more gratings that couple the light into or out of the waveguide via diffraction. The mechanisms and design principles disclosed herein for increasing the eye-box efficiency based on the in-plane relay may be applied to other suitable geometric waveguide display systems. For example, the couplers in the geometric waveguide display systems may include partially mirrors, beam splitters, fully reflective mirrors, or a combination thereof, etc. The mirrors in the geometric waveguide display systems may have suitable shapes, such as bar mirror arrays, pin-hole mirrors, etc. The geometric waveguide display system may be a one-dimensional (1D) geometric waveguide display system (that may not include a folding element), a two-dimensional (2D) geometric waveguide display system, or a Kaleido waveguide display system, etc.

FIG.4Aillustrates a schematic diagram of an artificial reality device400according to an example of the present disclosure. The artificial reality device400may produce VR, AR, and/or MR content for a user, such as images, video, audio, or a combination thereof. For example, the artificial reality device400may be smart glasses, or may be a near-eye display (“NED”). In some examples, the artificial reality device400may be in the form of eyeglasses, goggles, a helmet, a visor, or some other type of eyewear. In some examples, the artificial reality device400may be configured to be worn on a head of a user (e.g., by having the form of spectacles or eyeglasses, as shown inFIG.4A), or to be included as part of a helmet that is worn by the user. In some examples, the artificial reality device400may be configured for placement in proximity to an eye or eyes of the user at a fixed location in front of the eye(s), without being mounted to the head of the user. In some examples, the artificial reality device400may be in a form of eyeglasses which provide vision correction to a user's eyesight. In some examples, the artificial reality device400may be in a form of sunglasses which protect the eyes of the user from the bright sunlight. In some examples, the artificial reality device400may be in a form of safety glasses which protect the eyes of the user. In some examples, the artificial reality device400may be in a form of a night vision device or infrared goggles to enhance vision of a user at night.

For discussion purposes,FIG.4Ashows that the artificial reality device400includes a frame405configured to mount to a head of a user, and left-eye and right-eye display systems410L and410R mounted to the frame405.FIG.4Bis a cross-sectional view of half of the artificial reality device400shown inFIG.4Aaccording to an example of the present disclosure. For discussion purposes,FIG.4Bshows the cross-sectional view associated with the left-eye display system410L. The frame405is merely an example structure to which various components of the artificial reality device400may be mounted. Other suitable type of fixtures may be used in place of or in combination with the frame405.

In some examples, one or both of the left-eye and right-eye display systems410L and410R may include suitable image display components configured to generate an image light representing a virtual image, and guide the image light toward the eye-box region259. In some examples, one or both of the left-eye and right-eye display systems410L and410R may include suitable optical components configured to direct the image light toward the eye-box region259. For illustrative purposes,FIG.4Bshows that the left-eye display systems410L may include the light source assembly205(e.g., a projector) coupled to the frame405and configured to generate the image light representing a virtual image. In some examples, one or both of the left-eye and right-eye display systems410L and410R may include a waveguide display system disclosed herein, e.g., the system200shown inFIGS.2A-3E. Thus, the artificial reality device400may provide a significantly increased eye-box efficiency through the system200.

The present disclosure provides a system. The system includes a waveguide configured to guide an in-coupled image light to propagate inside the waveguide via total internal reflection; an in-coupling element configured to couple an input image light into the waveguide as the in-coupled image light; a plurality of partial reflectors at least partially embedded inside the waveguide; and an in-plane relay at least partially embedded inside the waveguide and disposed between the in-coupling element and the partial reflectors. The in-plane relay includes a plurality of cylindrical reflectors. The in-plane relay is configured to convert the in-coupled image light received from the in-coupling element into a relayed image light.

In some examples, the plurality of cylindrical reflectors include at least one cylindrical mirror. In some examples, the in-coupled image light includes a plurality of bundles of first parallel rays, and the in-plane relay is configured to convert the plurality of bundles of first parallel rays into a plurality of bundles of second parallel rays included in the relayed image light. In some examples, the plurality of cylindrical reflectors include a first cylindrical reflector and a second cylindrical reflector arranged opposite to the first cylindrical reflector. The first cylindrical reflector is configured to reflect the plurality of bundles of first parallel rays as a plurality of bundles of non-parallel rays propagating toward the second cylindrical reflector via total internal reflection, and the second cylindrical reflector is configured to reflect the plurality of bundles of non-parallel rays as the plurality of bundles of second parallel rays.

In some examples, the in-plane relay is configured to relay a virtual image represented by the in-coupled image light received from the in-coupling element to an intermediate image plane located at a predetermined portion of the waveguide. The partial reflectors are at least partially embedded at the predetermined portion.

In some examples, the partial reflectors are configured to split the relayed image light into a plurality of redirected image lights propagating inside the waveguide. In some examples, the partial reflectors are first partial reflectors, and the system further includes a plurality of second partial reflectors at least partially embedded inside the waveguide. The first partial reflectors are disposed between the in-plane relay and the second partial reflectors.

In some examples, the relayed image light output from the in-plane relay is incident onto the first partial reflectors as a first convergent image light, and the redirected image lights are incident onto the second partial reflectors as second convergent image lights. In some examples, the second partial reflectors are configured to couple the redirected image lights out of the waveguide as a plurality of output image lights. In some examples, at least one of the output image lights propagates convergently and then divergently toward an eye-box region of the system.

In some examples, the in-plane relay is configured to relay a virtual image represented by the in-coupled image light received from the in-coupling element to an intermediate image plane located at a predetermined portion of the waveguide, and the first partial reflectors are at least partially embedded at the predetermined portion.

In some examples, the in-plane relay is configured to relay a virtual image represented by the in-coupled image light received from the in-coupling element to an intermediate image plane located at a predetermined portion of the waveguide, and the second partial reflectors are at least partially embedded at the predetermined portion.

In some examples, the in-plane relay is configured to relay a virtual image represented by the in-coupled image light received from the in-coupling element to an intermediate image plane located between a first portion of the waveguide and a second portion of the waveguide, the first partial reflectors are at least partially embedded at the first portion, and the second partial reflectors are at least partially embedded at the second portion.

In some examples, the in-plane relay is configured to relay a virtual image represented by the in-coupled image light received from the in-coupling element to an intermediate image plane located within an eye-box region of the system. In some examples, the in-plane relay is configured to form one of a 4-f imaging assembly, a 2-f imaging assembly, a 1-f imaging assembly, or a 0.5-f imaging assembly. In some examples, the in-plane relay is configured to at least partially correct an optical aberration in the in-coupled image light. In some examples, one or more of the plurality of cylindrical reflectors have a non-optical power direction along a thickness direction of the waveguide. In some examples, one or more of the plurality of cylindrical reflectors include at least one of a concave cylindrical mirror, a convex cylindrical mirror, or a freeform cylindrical mirror. In some examples, the partial reflectors include flat partial reflective surfaces arranged in parallel, and one or more of the flat partial reflective surfaces form an acute angle with respect to a surface perpendicular to a thickness direction of the waveguide. In some examples, the relayed image light is incident onto the partial reflectors as a convergent image light. In some examples, the in-coupling element includes at least one of a mirror or a grating. In some examples, the out-coupling element includes at least one of a mirror or a grating.

The foregoing description of the embodiments of the present disclosure have been presented for the purpose of illustration. It is not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Persons skilled in the relevant art can appreciate that modifications and variations are possible in light of the above disclosure.

Some portions of this description may describe the embodiments of the present disclosure in terms of algorithms and symbolic representations of operations on information. These operations, while described functionally, computationally, or logically, may be implemented by computer programs or equivalent electrical circuits, microcode, or the like. Furthermore, it has also proven convenient at times, to refer to these arrangements of operations as modules, without loss of generality. The described operations and their associated modules may be embodied in software, firmware, hardware, or any combinations thereof.

Various aspects of the present disclosure may also relate to an apparatus for performing the operations herein. This apparatus may be specially constructed for the specific purposes, and/or it may include a general-purpose computing device selectively activated or reconfigured by a computer program stored in the computer. Such a computer program may be stored in a non-transitory, tangible computer readable storage medium, or any type of media suitable for storing electronic instructions, which may be coupled to a computer system bus. The non-transitory computer-readable storage medium can be any medium that can store program codes, for example, a magnetic disk, an optical disk, a read-only memory (“ROM”), or a random access memory (“RAM”), an Electrically Programmable read only memory (“EPROM”), an Electrically Erasable Programmable read only memory (“EEPROM”), a register, a hard disk, a solid-state disk drive, a smart media card (“SMC”), a secure digital card (“SD”), a flash card, etc. Furthermore, any computing systems described in the specification may include a single processor or may be architectures employing multiple processors for increased computing capability. The processor may be a central processing unit (“CPU”), a graphics processing unit (“GPU”), or any processing device configured to process data and/or performing computation based on data. The processor may include both software and hardware components. For example, the processor may include a hardware component, such as an application-specific integrated circuit (“ASIC”), a programmable logic device (“PLD”), or a combination thereof. The PLD may be a complex programmable logic device (“CPLD”), a field-programmable gate array (“FPGA”), etc.

Further, when an embodiment illustrated in a drawing shows a single element, it is understood that the embodiment or an embodiment not shown in the figures but within the scope of the present disclosure may include a plurality of such elements. Likewise, when an embodiment illustrated in a drawing shows a plurality of such elements, it is understood that the embodiment or an embodiment not shown in the figures but within the scope of the present disclosure may include only one such element. The number of elements illustrated in the drawing is for illustration purposes only, and should not be construed as limiting the scope of the embodiment. Moreover, unless otherwise noted, the embodiments shown in the drawings are not mutually exclusive, and features of different embodiments may be combined in any suitable manner. For example, elements shown in one figure/embodiment but not shown in another figure/embodiment may nevertheless be included in the other figure/embodiment. In any optical device disclosed herein including one or more optical layers, films, plates, or elements, the numbers of the layers, films, plates, or elements shown in the figures are for illustrative purposes only. In other embodiments not shown in the figures, which are still within the scope of the present disclosure, the same or different layers, films, plates, or elements shown in the same or different figures/embodiments may be combined or repeated in various manners to form a stack.

Various embodiments have been described to illustrate the exemplary implementations. Based on the disclosed embodiments, a person having ordinary skills in the art may make various other changes, modifications, rearrangements, and substitutions without departing from the scope of the present disclosure. Thus, while the present disclosure has been described in detail with reference to the above embodiments, the present disclosure is not limited to the above described embodiments. The present disclosure may be embodied in other equivalent forms without departing from the scope of the present disclosure. The scope of the present disclosure is defined in the appended claims.