Holographic waveguide

Abstract

A waveguide includes at least a first photopolymer layer and a second photopolymer layer with a barrier layer therebetween, and a first transparent layer and a second transparent layer covering the first and second photopolymer layers, respectively. The waveguide can further include at least one holographic input coupler and at least one holographic output coupler, each configured to respond to light within a first wavelength band and not to light outside the first wavelength band, and further configured to be transmissive or reflective.

Description

Background Art

[0001] A waveguide is an optical component that guides light to travel within the volume of the waveguide through total internal reflection (TIR). That is, light incident on the boundary of the waveguide at an angle within a certain range will be reflected back into the waveguide and thus remain within the volume of the waveguide. A waveguide typically includes an input coupler that receives light from a light source and redirects the received light into the volume of the waveguide at an angle within the range required for total internal reflection.

[0002] The waveguide can also include an output coupler that receives light from within the waveguide and redirects the light to travel at an angle outside the range required for total internal reflection. Thus, the light incident on the output coupler within the waveguide can be redirected to exit the volume of the waveguide.

[0003] The waveguide can be combined with or incorporated into a transparent carrier material to form an optical combiner, allowing light from the environment outside the waveguide to travel through the waveguide and "combine" with the light traveling within the waveguide. A wearable heads-up display device (WHUD) is configured to be worn by a user such that the optical combiner is positioned in front of the user's eyes, allowing an image represented by the light within the waveguide to be projected onto the user of the WHUD as an image overlaying the image of the environment viewed by the user through the WHUD. The resulting composite view is also referred to as augmented reality (AR). Brief Description of the Drawings

[0004] By referring to the accompanying drawings, the present disclosure is better understood, and many of its features and advantages are apparent to those skilled in the art. The same reference numerals are used in different drawings to indicate similar or identical items.

[0005] Figure 1 is a top cross-sectional schematic view of a wearable heads-up display having an optical combiner that houses a waveguide according to some embodiments.

[0006] Figure 2 is an orthogonal cross-sectional view of a waveguide system having a transmissive holographic input coupler and a transmissive holographic output coupler according to some embodiments.

[0007] Figure 3 is a Figure 2 orthogonal cross-sectional view of a holographic waveguide system having a reflective holographic input coupler and a reflective holographic output coupler according to some embodiments.

[0008] Figure 4A holographic waveguide system having a plurality of holographic input couplers and holographic output couplers in the same photopolymer layer, according to some embodiments Figure 2 Orthogonal side view of the holographic waveguide system

[0009] Figure 5 Orthogonal cross-sectional view of another holographic waveguide system having a holographic input coupler and a holographic output coupler, according to some embodiments

[0010] Figure 6 Orthogonal front view of a waveguide showing an expander region incorporating a plurality of input couplers and output couplers, according to some embodiments

[0011] Figures 7 to 13 Top cross-sectional view of an optical combiner, according to some embodiments, in which the waveguide is carried by a transparent carrier Detailed Description

[0012] The waveguide can be formed from photopolymer layers bonded together, which can be further joined to other material layers to form a stack of layers having optical properties that facilitate the propagation of light within the waveguide. Certain photopolymers can be exposed to specific wavelengths and angles of light, causing interference patterns to form within the photopolymer. These interference patterns are called "holograms" and can be configured to form wavelength-sensitive gratings within the photopolymer layer. The holograms formed in the waveguide selectively transmit, reflect, or redirect light having wavelengths within a narrow band of light. Since holograms can direct light to a single diffraction order with high efficiency and because the hologram functionality similar to a multi-lens system can be implemented on a plane, such holograms are used as input couplers or output couplers for the waveguide, thus reducing the bulk of the waveguide

[0013] Figures 1 to 13 Illustrative embodiments of a waveguide that uses a holographic input coupler to selectively direct light within a specific band into the waveguide and a holographic output coupler to direct light out of the waveguide. The holographic input couplers and output couplers can be configured as reflective or transmissive, causing the light within the waveguide to be directed along different optical paths within the waveguide before being directed out of the waveguide, typically towards the user's eye. To use the waveguide described herein as part of a WHUD, the waveguide is coupled to or integrated into a transparent carrier material to form an optical combiner that can be implemented as a lens-like structure held by a frame in front of the user's eye to allow an image to be displayed to the user such that the image appears to overlay the environment visible to the user through the optical combiner

[0014] Figure 1FIG. is a top-down cross-sectional schematic view of a WHUD 100 employing waveguides 116, 118. The WHUD 100 includes a first arm 102 to be positioned on a first side of a user's head, a second arm 104 to be positioned on a second side of the user's head, and a front frame 106 to be positioned on a front side of the user's head (i.e., in front of the user's eyes). The front frame 106 is coupled to each of the first arm 102 and the second arm 104, for example, by hinges. Figure 1 The frame 106 represented in can be configured to have a shape similar to that of glasses, such that the waveguides are supported under the portions of the frame 106 shown. In the WHUD 100, each of the waveguides 116 and 118 can be carried by a transparent optical carrier to form an optical combiner or "lens". Such a lens can be planar or curved. The optical combiner can also be configured to provide prescription optical correction to the user (i.e., apply optical power to the light passing therethrough) or non-prescription optical correction (i.e., not apply optical power to the light passing therethrough).

[0015] The first arm 102 includes a first light engine 108, and the second arm 104 includes a second light engine 110. The first and second light engines 108, 110 can be respectively housed within or coupled to the first and second arms 102, 104. The front frame 106 is configured to support a first waveguide 116 and a second waveguide 118. The first and second waveguides 116, 118 can be housed within or coupled to the front frame 106.

[0016] The first light engine 108 is configured to output a first display light 122 representative of display content (e.g., image or video content) to be viewed by the user. The first display light 122 is redirected by the first waveguide 116 towards the user's first eye 120, such that the user can see the display content. In the case of the WHUD 100, the first waveguide 116 includes a waveguide combiner that includes an input coupler 130 and an output coupler 132. The first display light 122 from the first light engine 108 impinges on the input coupler 130 and is redirected into the first waveguide 116, where the first display light 122 is guided through the waveguide by TIR. Subsequently, the first display light 122 in the waveguide 116 impinges on the output coupler 132, which redirects the first display light 122 out of the waveguide 116 and towards the user's first eye 120.

[0017] Similarly, the second waveguide 118 includes an input coupler 134 and an output coupler 136. Second display light 124 from the second light engine 110 impinges on the input coupler 134 and is redirected into the second waveguide 118, where the second display light 124 is guided through the waveguide 118 by total internal reflection. Subsequently, the second display light 124 in the second waveguide 118 impinges on the output coupler 136, which redirects the second display light 124 out of the waveguide 118 and toward the user's second eye 126.

[0018] Further, as Figure 1 illustrated, the WHUD 100 is a binocular display that provides a first light engine 108 and a first waveguide 116 that present first display light 122 to the first eye 120, and a second light engine 110 and a second waveguide 118 that present second display light 124 to the second eye 126. However, a monocular display can be implemented by eliminating either the first light engine 108 and the first waveguide 116, or the second light engine 110 and the second waveguide 118.

[0019] Figure 2 Illustrated is an orthogonal cross-section of a holographic waveguide system 200 that includes transmissive holographic input couplers 204, 206 and transmissive holographic output couplers 208, 230 within a waveguide 202. In the context of the holographic waveguides described herein, an "input coupler" refers to an element that receives input light and redirects the input light to satisfy the total internal reflection condition of the waveguide. That is, the input light is redirected by the input coupler within a certain angular range for which the light will be reflected by the boundary of the waveguide rather than pass through the boundary. In the context of the holographic waveguides described herein, an "output coupler" refers to an element that receives light traveling within the waveguide and redirects the received light to a condition that does not satisfy the total internal reflection condition of the waveguide. That is, the received light is redirected by the output coupler to an angular range for which the light will be reflected by the boundary of the waveguide such that the light will pass through the boundary. In view of the foregoing, an "input coupler" substantially redirects external light to travel within the waveguide, and an "output coupler" substantially redirects light within the waveguide to exit the waveguide.

[0020] The waveguide 202 includes a first photopolymer layer 210, a second photopolymer layer 220, and a barrier layer 240 positioned between the first photopolymer layer 210 and the second photopolymer layer 220. The waveguide 202 also includes a first transparent layer 260 and a second transparent layer 270. The first photopolymer layer 210, the second photopolymer layer 220, and the barrier layer 240 are disposed between the first transparent layer 260 and the second transparent layer 270. Preferably, each of the first photopolymer layer 210, the second photopolymer layer 220, the barrier layer 240, the first transparent layer 260, and the second transparent layer 270 will have the same or a similar refractive index to minimize unwanted refraction of light traveling through the waveguide 202. Thus, light that undergoes total internal reflection within the volume of the waveguide 202 will be reflected away from the outermost surface 262 of the first transparent layer 260 or the outermost surface 272 of the second transparent layer 270. Further, each of the first photopolymer layer 210, the second photopolymer layer 220, the barrier layer 240, the first transparent layer 260, and the second transparent layer 270 can be planar or curved.

[0021] Additional layers can be included in the waveguide 202, such as in the embodiment described below with reference to Figure 5 the example shown. Figure 2 The layers of the waveguide 202 shown in can be stacked on one another such that the first photopolymer layer 210 is carried by the first transparent layer 260, the barrier layer 240 is carried by the first photopolymer layer 210, the second photopolymer layer 220 is carried by the barrier layer 240, and the second transparent layer 270 is carried by the second photopolymer layer 220.

[0022] The waveguide system 200 includes a light source 310 that outputs light 312 having a wavelength within a first wavelength band and light 314 having a wavelength within a second wavelength band that is different from the first wavelength band. For ease of illustration, in the corresponding operations described below and in the figures, the separate light wavelength bands 312 are shown as single rays. Preferably, the first wavelength band and the second wavelength band do not overlap. The input coupler 204 and the output coupler 208 are responsive to light within the first wavelength band and not responsive to light outside the first wavelength band. The input coupler 206 and the output coupler 230 are responsive to light within the second wavelength band and not responsive to light outside the second wavelength band.

[0023] Accordingly, the input coupler 204 is capable of receiving the light 312 and redirecting the light 312 to travel within the waveguide 202. Subsequently, the output coupler 208 is capable of receiving the light 312 traveling in the waveguide 202 and redirecting the light 312 to exit the waveguide 202. Similarly, the input coupler 206 is capable of receiving the light 314 and redirecting the light 314 to travel within the waveguide 202. Subsequently, the output coupler 230 is capable of receiving the light 314 traveling in the waveguide 202 and redirecting the light 314 to exit the waveguide 202. Since the input coupler 204 does not respond to light having a wavelength outside the first wavelength band, the light 314 can pass through the input coupler 204 without being affected. This allows the waveguide to be designed around a narrow-band light source selection group, where each narrow-band light has a corresponding set of input and output coupling holograms in the waveguide.

[0024] Figure 2 Each of the input couplers shown in can be laterally aligned with each other along a first axis 280 orthogonal to the light polymer layer. For example, as Figure 2 illustrated, the first light polymer layer 210 and the second light polymer layer 220 are parallel to each other, and the first input coupler 204 and the second input coupler 206 are aligned with each other along the first axis 280, which is orthogonal to the first light polymer layer 210 and the second light polymer layer 220. This allows the light source 310 to output the light 312 and the light 314 to the same region of the waveguide 202, such that both the light 312 and the light 314 are incident on the first input coupler 204, but the light 312 is refracted from the first input coupler 204 while the light 314 is transmitted through the first input coupler 204 unchanged to the second input coupler 206.

[0025] Similarly, Figure 2 each of the output couplers shown in

[0024] can be laterally aligned with each other along a second axis 282 orthogonal to the light polymer layer. As can be seen in Figure 2 Figure 2 , each of the first output coupler 208 and the second output coupler 230 is aligned with each other along the second axis 306, which is orthogonal to the first light polymer layer 210 and the second light polymer layer 220. This allows the light 312 and the light 314 traveling within the waveguide 202 to be coupled and output onto the display area. Although, as detailed above, each of the input couplers can generally be aligned with each other, each of the input couplers does not have to occupy the same region within different layers of the waveguide 202. For example, the light source 310 can be positioned at an oblique angle relative to the waveguide 202 such that each input coupler is positioned to occupy a slightly different region, even though the input couplers are generally aligned.

[0026] Figure 2Each of the input coupler and the output coupler shown is a transmissive hologram. In a transmissive hologram, light of a particular wavelength incident on a given input coupler or output coupler configured to act on that wavelength passes through the input coupler or output coupler but is refracted to travel at different angles. However, holograms can also be recorded in the layers of waveguide 202, and these holograms are reflective, as discussed below with reference to Figure 3 as discussed.

[0027] In Figure 2 the following description, the "first section" of the optical path refers to the path traveled by the first light 312 or the second light 314 from the point where light enters waveguide 202 to the reflection region 284. The "second section" corresponds to the path traveled by the representation of the light from the reflection region 284 to the reflection region 286. The "third section" refers to the path traveled by the representation of the light from the reflection region 286 to the reflection region 288. The "fourth section" corresponds to the path traveled by the representation of the light from the reflection region 288 to the point where the representation of the light exits waveguide 202. Details of the first through fourth sections of the optical path are described below. The reflection regions described herein do not have unique properties compared to the rest of the waveguide. Instead, the term "reflection region" is intended to depict such a region of the waveguide where light is totally internally reflected at the boundary of the waveguide, and depending on the angle of incidence of the light entering the waveguide and the redirection angle of the holographic input coupler, this region could conceivably be anywhere on the boundary of the waveguide. Note that once light from the light source 310 enters the waveguide, it is described as a "representation" of the light because properties of the light, such as, for example, the polarization direction, can change as the light passes through the layers and surfaces of waveguide 202 and / or is refracted and / or reflected by the layers and surfaces of waveguide 202.

[0028] The first holographic input coupler 204 and the first holographic output coupler 208 of the waveguide 202 define a first optical path for a first light 312 having a wavelength within a first wavelength band entering the waveguide 202. The first optical path includes a first section in which the first light 312 passes through the first transparent layer 260, is redirected by the first holographic input coupler 204, passes through the first barrier layer 240, passes through the second photopolymer layer 220, enters the second transparent layer 270, and is totally internally reflected by the outermost surface 272 of the second transparent layer 270 at the reflection region 284. The first optical path includes a second section in which the representation of the first light 312 reflected by the outermost surface (at the reflection region 284) of the second transparent layer 270 exits the second transparent layer 270, passes through the second photopolymer layer 220, passes through the first barrier layer 240, passes through the first photopolymer layer 210, enters the first transparent layer 260, and is totally internally reflected by the outermost surface 262 of the first transparent layer 260 at the reflection region 286. The first optical path includes a third section in which the representation of the first light 312 reflected by the outermost surface 262 of the first transparent layer 260 exits the first transparent layer 260, passes through the first photopolymer layer 210, passes through the first barrier layer 240, passes through the second photopolymer layer 220, enters the second transparent layer 270, and is totally internally reflected by the outermost surface 272 of the second transparent layer 270 at the reflection region 288. The first optical path further includes a fourth section in which the representation of the first light 312 reflected by the outermost surface 272 of the second transparent layer 270 exits the second transparent layer 270, passes through the second photopolymer layer 220, passes through the first barrier layer 240, is redirected by the first holographic output coupler 208, and passes through the first transparent layer 260, thereby exiting the waveguide 202.

[0029] Figure 2Also illustrated is a second optical path of a second light 314 having a wavelength within a second wavelength band entering waveguide 202. The second optical path includes a first section in which the second light 314 passes through a first transparent layer 260, through a first optical polymer layer 210, through a first barrier layer 240, is redirected by a second holographic input coupler 206, enters a second transparent layer 270, and is totally internally reflected by an outermost surface 272 of the second transparent layer 270 at a reflection region 284. The second optical path includes a second section in which a representation of the second light 314 reflected by the outermost surface of the second transparent layer 270 exits the second transparent layer 270, passes through a second optical polymer layer 220, through a first barrier layer 240, through a first optical polymer layer 210, enters a first transparent layer 260, and is totally internally reflected by an outermost surface 262 of the first transparent layer 260 at a reflection region 286. The second optical path includes a third section in which a representation of the second light 314 reflected by the outermost surface 262 of the first transparent layer 260 exits the first transparent layer 260, passes through a first optical polymer layer 210, through a first barrier layer 240, through a second optical polymer layer 220, enters a second transparent layer 270, and is totally internally reflected by an outermost surface 272 of the second transparent layer 270. The second optical path further includes a fourth section in which a representation of the second light 314 reflected by the outermost surface of the second transparent layer 270 exits the second transparent layer 270, is redirected by a second holographic output coupler 230, passes through a first barrier layer 240, through a first optical polymer layer 210, and through a first transparent layer 260, thereby exiting waveguide 202.

[0030] Figure 3 is an orthogonal cross-section of a waveguide system 300 that includes a light source 310 and a waveguide 302 having similar layers as discussed above with reference to Figure 2 Waveguide 302 includes a first holographic input coupler 320 recorded in a first optical polymer layer 210 and a first holographic output coupler 322 recorded in the first optical polymer layer 210. Waveguide 302 further includes a second holographic input coupler 324 recorded in a second optical polymer layer 220 and a second holographic output coupler 326 recorded in the second optical polymer layer 220. Compared with the transmissive holographic input couplers 204 and 206 shown in Figure 2 , each of the input couplers and output couplers shown in Figure 3 is a reflective hologram. That is, light incident on a given input coupler or output coupler shown in Figure 3 is reflected from the corresponding input coupler or output coupler to travel back in a direction generally in which the light originated but at a different angle. Using reflective holograms for the input couplers and output couplers results in an optical path for light traveling within waveguide 302, as discussed below.

[0031] The waveguide system 300 includes a light source 310 that outputs a first light 312 having a wavelength within a first band and a second light 314 having a wavelength within a second band different from the first band. Preferably, the first band and the second band do not overlap. The input coupler 320 and the output coupler 322 respond to light within the first band and do not respond to light outside the first band. The input coupler 324 and the output coupler 326 respond to light within the second band and do not respond to light outside the second band.

[0032] Accordingly, the input coupler 320 receives the light 312 and redirects the light 312 to travel within the waveguide 302. Subsequently, the output coupler 322 receives the light 312 traveling in the waveguide 302 and redirects the light 312 to exit the waveguide 302. Similarly, the input coupler 324 receives the light 314 and redirects the light 314 to travel within the waveguide 302.

[0033] Subsequently, the output coupler 326 receives the light 314 traveling in the waveguide 302 and redirects the light 314 to exit the waveguide 302. Since the input coupler 320 does not respond to light having a wavelength outside the first band, the light 314 passes through the input coupler 320 without being affected. This allows the waveguide 302 to be designed around a narrow-band light source selection group, where each narrow-band light has a corresponding set of input and output coupling holograms in the waveguide 302.

[0034] In the subsequent Figure 3 description, the "first section" corresponds to the path traveled by the first light 312 or the second light 314 from the point where the light 312, 314 enters the waveguide 302 to the reflection region 330. The "second section" corresponds to the path traveled by the representation of the first or second light 312, 314 from the reflection region 330 to the reflection region 332. The "third section" corresponds to the path traveled by the representation of the first or second light 312, 314 from the reflection region 332 to the reflection region 334. The "fourth section" corresponds to the path traveled by the representation of the first or second light 312, 314 from the reflection region 334 to the point where the representation of the first or second light 312, 314 exits the waveguide 302.

[0035] The first holographic input coupler 320 and the first holographic output coupler 322 define a first optical path for a first light 312 having a wavelength within a first wavelength band entering the waveguide 302. The first optical path includes a first section in which the first light 312 passes through the first transparent layer 260, is reflected back into the first transparent layer 260 by the first holographic input coupler 320, and is totally internally reflected by the outermost surface 262 of the first transparent layer 260 at the reflection region 330. The first optical path includes a second section in which a representation of the first light 312 reflected by the outermost surface 262 of the first transparent layer 260 at the reflection region 330 exits the first transparent layer 260, passes through the first light polymer layer 210, passes through the first barrier layer 240, passes through the second light polymer layer 220, enters the second transparent layer 270, and is totally internally reflected by the outermost surface 272 of the second transparent layer 270 at the reflection region 332. The first optical path includes a third section in which a representation of the first light 312 reflected by the outermost surface 272 of the second transparent layer 270 at the reflection region 332 exits the second transparent layer 270, passes through the second light polymer layer 220, passes through the first barrier layer 240, passes through the first light polymer layer 210, enters the first transparent layer 260, and is totally internally reflected by the outermost surface 262 of the first transparent layer 260 at the reflection region 334. The first optical path further includes a fourth section in which a representation of the first light 312 reflected by the outermost surface 262 of the first transparent layer 260 exits the first transparent layer 260, is reflected back into the first transparent layer 260 by the first holographic output coupler 322, and passes through the first transparent layer 260, thereby exiting the waveguide 302.

[0036] Figure 3Also illustrated is a second optical path of a second light 314 having a wavelength within a second wavelength band entering waveguide 302. The second optical path includes a first section in which the second light 314 passes through a first transparent layer 260, through a first optical polymer layer 210, through a first barrier layer 240, is reflected back to the first barrier layer 240 by a second holographic input coupler 322, passes through the first barrier layer 240, through the first optical polymer layer 210, into the first transparent layer 260, and is totally internally reflected by an outermost surface 262 of the first transparent layer 260 at a reflection region 330. The second optical path includes a second section in which a representation of the second light 314 reflected by the outermost surface 262 of the first transparent layer 260 at the reflection region 330 exits the first transparent layer 260, passes through the first optical polymer layer 210, through the first barrier layer 240, through a second optical polymer layer 220, into a second transparent layer 270, and is totally internally reflected by an outermost surface 272 of the second transparent layer 270 at a reflection region 332. The second optical path includes a third section in which a representation of the second light 314 reflected by the outermost surface 272 of the second transparent layer 270 exits the second transparent layer 270, passes through the second optical polymer layer 220, through the first barrier layer 240, through the first optical polymer layer 210, into the first transparent layer 260, and is totally internally reflected by the outermost surface 262 of the first transparent layer 260 at a reflection region 334. The second optical path includes a fourth section in which a representation of the second light 314 reflected by the outermost surface of the first transparent layer 260 exits the first transparent layer 260, passes through the first optical polymer layer 210, through the first barrier layer 240, is reflected back into the first barrier layer 240 by a second holographic output coupler 326, passes through the first barrier layer 240, through the first optical polymer layer 210, and through the first transparent layer 260, thereby exiting waveguide 302.

[0037] Each of input coupler 320 and input coupler 324 can be laterally aligned with each other, such as along a first axis perpendicular to the first optical polymer layer 210 and the second optical polymer layer 220. Further, each of output coupler 322 and output coupler 326 can be laterally aligned with each other, such as along a second axis perpendicular to the first optical polymer layer 210 and the second optical polymer layer 220.

[0038] Figure 2 and Figure 3 Also illustrated are a first light 312 and a second light 314 each undergoing total internal reflection three times within waveguide 202 or waveguide 302. This number of reflections is merely exemplary and can be smaller or larger. For example, light coupled into waveguide 202 or waveguide 302 may be totally internally reflected only once, twice, five times, ten times, twenty times, or more, depending on the circumstances of a given application.

[0039] Figure 2 and Figure 3 also each illustrate a light source 310 that outputs first light 312 having a wavelength within a first wavelength band and second light 314 having a wavelength within a second wavelength band different from the first wavelength band. However, the light source may emit light in more wavelength bands, and the waveguide may be capable of guiding such light in other wavelength bands.

[0040] Figure 4 is an orthogonal cross-sectional view of a waveguide system 400 that includes a waveguide 402 having similar layers as discussed above with reference to Figure 2 and having a plurality of input couplers and output couplers in the same light polymer layer. The waveguide system 400 includes a light source 410 that outputs first light 412 having a wavelength within a first wavelength band, second light 414 having a wavelength within a second wavelength band, and third light 416 having a wavelength within a third wavelength band. The first wavelength band, the second wavelength band, and the third wavelength band are different from each other and preferably do not overlap with each other.

[0041] The first light polymer layer 210 includes a first holographic input coupler 204 and a first holographic output coupler 208 that redirect the first light 412 into the waveguide 402. The second light polymer layer 220 includes a second holographic input coupler 206 and a second holographic output coupler 230 that redirect the second light 414 into the waveguide 402. In addition, the first light polymer layer 210 in the waveguide 402 includes a third holographic input coupler 214 and a third holographic output coupler 218 that redirect the third light 416 into the waveguide 402.

[0042] In Figure 4 the following description of the third optical path illustrated in, "the first section" corresponds to the path traveled by the third light 416 from the point where the third light 416 enters the waveguide 402 to the reflection region 420. "The second section" corresponds to the path traveled by the representation of the third light 416 from the reflection region 420 to the reflection region 422. "The third section" corresponds to the path traveled by the representation of the third light 416 from the reflection region 422 to the reflection region 424. "The fourth section" corresponds to the path traveled by the representation of the third light 416 from the reflection region 424 to the point where the representation of the third light 416 exits the waveguide 402.

[0043] The third holographic input coupler 214 and the third holographic output coupler 218 define a third optical path for a third light 416 having a wavelength within a third wavelength band that enters waveguide 402. The third optical path includes a first section in which the third light 416 passes through the first transparent layer 260, is redirected by the third holographic input coupler 214, passes through the first barrier layer 240, passes through the second photopolymer layer 220, enters the second transparent layer 270, and is totally internally reflected by the outermost surface 272 of the second transparent layer 270 at the reflection region 420. The third optical path includes a second section in which a representation of the third light 416 reflected by the outermost surface 272 of the second transparent layer 270 exits the second transparent layer 270, passes through the second photopolymer layer 220, passes through the first barrier layer 240, passes through the first photopolymer layer 210, enters the first transparent layer 260, and is totally internally reflected by the outermost surface 262 of the first transparent layer 260 at the reflection region 422. The third optical path includes a third section in which a representation of the third light 416 reflected by the outermost surface 262 of the first transparent layer 260 exits the first transparent layer 260, passes through the first photopolymer layer 210, passes through the first barrier layer 240, passes through the second photopolymer layer 220, enters the second transparent layer 270, and is totally internally reflected by the outermost surface 272 of the second transparent layer 270 at the reflection region 424. The third optical path further includes a fourth section in which a representation of the third light 416 reflected by the outermost surface 272 of the second transparent layer 270 exits the second transparent layer 270, passes through the second photopolymer layer 220, passes through the first barrier layer 240, is redirected by the third holographic output coupler 218, and passes through the first transparent layer 260, thereby exiting waveguide 402.

[0044] Figure 4 Each of the holographic input coupler and the holographic output coupler is shown as a transmissive hologram. However, either the holographic input coupler or the output coupler can be a reflective hologram, such as those described above with reference to Figure 2 Those. In particular, the first holographic input coupler 204 and the first holographic output coupler 208 can be reflective holograms, which are similar to how the first holographic input coupler 320 and the first holographic output coupler 322 redirect the first light 312 through waveguide 302 to redirect the first light 412 through waveguide 402, such as according to Figure 3 The first optical path shown and described above. The second holographic input coupler 206 and the second holographic output coupler 230 can be reflective holograms, which are similar to how the second holographic input coupler 324 and the second holographic output coupler 326 redirect the second light 314 through waveguide 302 to redirect the second light 414 through waveguide 402, such as according to Figure 3 The first optical path shown and described above.

[0045] Additionally, the third holographic input coupler 214 and the third holographic output coupler 218 can be reflective holograms that define an alternative third optical path for third light 416 having a wavelength within the third wavelength band into waveguide 402. The alternative third optical path can include a first section in which the third light 416 passes through the first transparent layer 260, is reflected back into the first transparent layer 260 by the third holographic input coupler 214, and is totally internally reflected by the outermost surface of the first transparent layer 260. The alternative third optical path can include a second section in which a representation of the third light 416 reflected by the outermost surface of the first transparent layer 260 exits the first transparent layer 260, passes through the first photopolymer layer 210, passes through the first barrier layer 240, passes through the second photopolymer layer 220, enters the second transparent layer 270, and is totally internally reflected by the outermost surface 272 of the second transparent layer 270. The alternative third optical path can include a third section in which a representation of the third light 416 reflected by the outermost surface 272 of the second transparent layer 270 exits the second transparent layer 270, passes through the second photopolymer layer 220, passes through the first barrier layer 240, passes through the first photopolymer layer 210, enters the first transparent layer 260, and is totally internally reflected by the outermost surface 262 of the first transparent layer 260. The alternative third optical path can include a fourth section in which a representation of the third light 416 reflected by the outermost surface 262 of the first transparent layer 260 exits the first transparent layer 260, is reflected back into the first transparent layer 260 by the third holographic output coupler 218, and passes through the first transparent layer 260, thereby exiting waveguide 402.

[0046] Figure 4 Illustrated are first, second, and third lights 412, 414, and 416 that each undergo total internal reflection three times within waveguide 402. This number of reflections is merely exemplary and can be smaller or larger. For example, light coupled into waveguide 402 can be totally internally reflected one, five, ten, twenty, or more times, depending on the circumstances of a given application.

[0047] The first input coupler 212 is depicted in Figure 4 as being spatially offset from the third input coupler 214 in the first photopolymer layer 210. However, in reality, the first input coupler 212 and the third input coupler 214 can be recorded to occupy a similar volume within the photopolymer layer 210. Similarly, the first output coupler 216 is depicted in Figure 4 as being spatially offset from the third output coupler 218 in the first photopolymer layer 210. However, in reality, the first output coupler 216 and the third output coupler 218 can be recorded to occupy a similar volume within the first photopolymer layer 210.

[0048] The first optical polymer layer 210 of the waveguide 402 includes two holographic input couplers and two holographic output couplers recorded in the first optical polymer layer 210. Similar features may be implemented in the second optical polymer layer 220 such that the second optical polymer layer 220 includes two holographic input couplers responsive to different respective wavelength bands and two output couplers responsive to different respective wavelength bands. In an exemplary embodiment, the first optical polymer layer 210 may include a single holographic input coupler and a single holographic output coupler, while the second optical polymer layer 220 may include two holographic input couplers and two holographic output couplers. In another exemplary embodiment, the first optical polymer layer 210 may include two or more holographic input couplers and two or more holographic output couplers, and the second optical polymer layer 220 may include two or more holographic input couplers and two or more holographic output couplers.

[0049] As discussed above with reference to Figure 2 and Figure 3 each of the input coupler 204, the input coupler 214, and the input coupler 222 can be laterally aligned with each other, such as along a first axis perpendicular to the first optical polymer layer 210 and the second optical polymer layer 220. Further, each of the output coupler 208, the output coupler 218, and the output coupler 230 can be laterally aligned with each other, such as along a second axis perpendicular to the first optical polymer layer 210 and the second optical polymer layer 220.

[0050] Figure 5 Orthogonal side view illustrating another waveguide system 500. Although Figure 5 the waveguide system 500 of Figure 2Waveguide system 200, but waveguide 502 includes additional layers. Waveguide 502 includes a first photopolymer layer 510, a second photopolymer layer 520, a third photopolymer layer 530, a first barrier layer 540 disposed between the first photopolymer layer 510 and the second photopolymer layer 520, and a second barrier layer 550 disposed between the second photopolymer layer 520 and the third photopolymer layer 530. Waveguide 502 further includes a first transparent layer 560 and a second transparent layer 570. The first photopolymer layer 510, the second photopolymer layer 520, the third photopolymer layer 530, barrier layer 54 and barrier layer 550 are disposed between the first transparent layer 560 and the second transparent layer 570. Preferably, each of the first photopolymer layer 510, the second photopolymer layer 520, the third photopolymer layer 530, the first barrier layer 540, the second barrier layer 550, the first transparent layer 560 and the second transparent layer 570 will have the same or similar refractive index to minimize unwanted refraction of light traveling through waveguide 502 as the light passes between the layers. Further, each of the first photopolymer layer 510, the second photopolymer layer 520, the third photopolymer layer 530, the first barrier layer 540, the second barrier layer 550, the first transparent layer 560 and the second transparent layer 570 can be planar or curved.

[0051] Waveguide 502 includes a first holographic input coupler 512 recorded in the first photopolymer layer 510 and a first holographic output coupler 516 recorded in the first photopolymer layer 510. The waveguide further includes a second holographic input coupler 522 recorded in the second photopolymer layer 520, a second holographic output coupler 526 recorded in the second photopolymer layer 520, a third holographic input coupler 532 recorded in the third photopolymer layer 530, and a third holographic output coupler 536 recorded in the third photopolymer layer 530.

[0052] The waveguide system 500 also includes a light source 610 that outputs a first light 612 having a wavelength within a first band, a second light 614 having a wavelength within a second band, and a third light 616 having a wavelength within a third band. The first band, the second band, and the third band are different from each other and preferably do not overlap. The first holographic input coupler 512 and the first holographic output coupler 516 respond to light within the first band and do not respond to light outside the first band. The second holographic input coupler 522 and the second holographic output coupler 526 respond to light within the second band and do not respond to light outside the second band. The third holographic input coupler 532 and the third holographic output coupler 536 respond to light within the third band and do not respond to light outside the third band. Thus, the first holographic input coupler 512 receives the first light 612 and redirects the first light 612 to travel within the waveguide 502. Subsequently, the first holographic output coupler 516 receives a representation of the first light 612 traveling in the waveguide 502 and redirects the representation of the first light 612 to exit the waveguide 502. Similarly, the second holographic input coupler 522 receives the second light 614 and redirects the second light 614 to travel within the waveguide 502. Subsequently, the second holographic output coupler 526 receives the second light 614 traveling in the waveguide 502 and redirects the representation of the second light 614 to exit the waveguide 502. Because the first holographic input coupler 512 does not respond to light having a wavelength outside the first band, the second light 614 passes through the first holographic input coupler 512 without being affected. Similarly, the third holographic input coupler 532 receives the third light 616 and redirects the third light 616 to travel within the waveguide 502. Subsequently, the third holographic output coupler 536 receives a representation of the third light 616 traveling in the waveguide 502 and redirects the representation of the third light 616 to exit the waveguide 502. Because the first holographic input coupler 512 does not respond to light having a wavelength outside the first band and the second holographic input coupler 522 does not respond to light having a wavelength outside the second band, the third light 616 can pass through the first holographic input coupler 512 and the second holographic input coupler 522 without being affected. This allows the waveguide to be designed around a selected group of narrow-band light sources, where each narrow-band light is guided in the waveguide by a corresponding set of input and output coupling holograms.

[0053] In Figure 5In the following description of the optical path shown, the "first section" corresponds to the path traveled by the first, second, or third light 612, 614, 616 from the point where the light 612, 614, 616 enters the waveguide 502 to the reflection region 620. The "second section" corresponds to the path traveled by the light 612, 614, 616 from the reflection region 620 to the reflection region 622. The "third section" corresponds to the path traveled by the light 612, 614, 616 from the reflection region 622 to the reflection region 624, and the "fourth section" corresponds to the path traveled by the light 612, 614, 616 from the reflection region 624 to the point where the light 612, 614, 616 exits the waveguide 502.

[0054] The first holographic input coupler 512 and the first holographic output coupler 516 define a first optical path for the first light 612 having a wavelength within the first wavelength band entering the waveguide 502. The first optical path includes a first section in which the first light 612 passes through the first transparent layer 560, is redirected by the first holographic input coupler 512, passes through the first barrier layer 540, passes through the second photopolymer layer 520, passes through the second barrier layer 550, passes through the third photopolymer layer 530, enters the second transparent layer 570, and is totally internally reflected by the outermost surface 572 of the second transparent layer 570 at the reflection region 620. The first optical path includes a second section in which the representation of the first light 612 reflected by the outermost surface 572 of the second transparent layer 570 exits the second transparent layer 570, passes through the third photopolymer layer 530, passes through the second barrier layer 550, passes through the second photopolymer layer 520, passes through the first barrier layer 540, passes through the first photopolymer layer 510, enters the first transparent layer 560, and is totally internally reflected by the outermost surface 562 of the first transparent layer 560 at the reflection region 622. The first optical path includes a third section in which the representation of the first light 612 reflected by the outermost surface 562 of the first transparent layer 560 exits the first transparent layer 560, passes through the first photopolymer layer 510, passes through the first barrier layer 540, passes through the second photopolymer layer 520, passes through the second barrier layer 550, passes through the third photopolymer layer 530, enters the second transparent layer 570, and is totally internally reflected by the outermost surface 572 of the second transparent layer 570 at the reflection region 624. The first optical path includes a fourth section in which the representation of the first light 612 reflected by the outermost surface 572 of the second transparent layer 570 exits the second transparent layer 570, passes through the third photopolymer layer 530, passes through the second barrier layer 550, passes through the second photopolymer layer 520, passes through the first barrier layer 540, is redirected by the first holographic output coupler 516, and passes through the first transparent layer 560, thereby exiting the holographic waveguide 502.

[0055] Figure 5Also illustrated is a second optical path for second light 614 having a wavelength within a second wavelength band entering waveguide 502. The second optical path includes a first section in which the second light 614 passes through a first transparent layer 560, through a first optical polymer layer 510, through a first barrier layer 540, is redirected by a second holographic input coupler 522, through a second barrier layer 550, through a third optical polymer layer 530, into a second transparent layer 570, and is totally internally reflected by an outermost surface 572 of the second transparent layer 570 at a reflection region 620. The second optical path includes a second section in which a representation of the second light 614 reflected by the outermost surface 572 of the second transparent layer 570 exits the second transparent layer 570, passes through the third optical polymer layer 530, through the second barrier layer 550, through the second optical polymer layer 520, through the first barrier layer 540, through the first optical polymer layer 510, into the first transparent layer 560, and is totally internally reflected by an outermost surface 562 of the first transparent layer 560 at a reflection region 622. The second optical path includes a third section in which a representation of the second light 614 reflected by the outermost surface 562 of the first transparent layer 560 exits the first transparent layer 560, passes through the first optical polymer layer 510, through the first barrier layer 540, through the second optical polymer layer 520, through the second barrier layer 550, through the third optical polymer layer 530, into the second transparent layer 570, and is totally internally reflected by an outermost surface 572 of the second transparent layer 570 at a reflection region 624. The second optical path includes a third section in which a representation of the second light 614 reflected by the outermost surface 572 of the second transparent layer 570 exits the second transparent layer 570, passes through the third optical polymer layer 530, through the second barrier layer 550, is redirected by a second holographic output coupler 526, through the first barrier layer 540, through the first optical polymer layer 510, and through the first transparent layer 560, thereby exiting waveguide 502.

[0056] The third holographic input coupler 532 and the third holographic output coupler 536 of the waveguide 502 are also capable of defining a third optical path for a third light 616 having a wavelength within a third wavelength band that enters the waveguide 502. The third optical path includes a first section in which the third light 616 passes through the first transparent layer 560, through the first light polymer layer 510, through the first barrier layer 540, through the second light polymer layer 520, through the second barrier layer 550, is redirected by the third holographic input coupler 532, enters the second transparent layer 570, and is totally internally reflected by the outermost surface 572 of the second transparent layer 570 at the reflection region 620. The third optical path includes a second section in which the third light 616 reflected by the outermost surface 572 of the second transparent layer exits the second transparent layer 570, passes through the third light polymer layer 530, through the second barrier layer 550, through the second light polymer layer 520, through the first barrier layer 540, through the first light polymer layer 510, enters the first transparent layer 560, and is totally internally reflected by the outermost surface 562 of the first transparent layer 560 at the reflection region 622. The third optical path includes a third section in which the representation of the third light 616 reflected by the outermost surface of the first transparent layer 560 exits the first transparent layer 560, passes through the first light polymer layer 510, through the first barrier layer 540, through the second light polymer layer 520, through the second barrier layer 550, through the third light polymer layer 530, enters the second transparent layer 570, and is totally internally reflected by the outermost surface 572 of the second transparent layer 570 at the reflection region 624. The third optical path further includes a fourth section in which the representation of the third light 616 reflected by the outermost surface 572 of the second transparent layer 570 exits the second transparent layer 570, is redirected by the third holographic output coupler 536, passes through the second barrier layer 550, through the second light polymer layer 520, through the first barrier layer 540, through the first light polymer layer 510, and passes through the first transparent layer 560, thereby exiting the waveguide 502.

[0057] Figure 5 Each of the holographic input couplers and holographic output couplers illustrated in is a transmissive hologram. However, any one of the holographic input couplers and holographic output couplers can be a reflective hologram, such as Figure 3 those illustrated in. In the case where the first holographic input coupler 512 and the first holographic output coupler 516 are reflective holograms, an exemplary first optical path for the first light 612 is described below. In the case where the second holographic input coupler 522 and the second holographic output coupler 526 are reflective holograms, an exemplary second optical path for the second light 614 is discussed below. In the case where the third holographic input coupler 532 and the third holographic output coupler 536 are reflective holograms, an exemplary third optical path for the third light 616 is discussed below.

[0058] The reflective first holographic input coupler 512 and the reflective first holographic output coupler 516 can define a first optical path for first light 612 having a wavelength within a first wavelength band entering the waveguide 502. The first optical path can include a first section in which the first light 612 passes through the first transparent layer 560, is reflected back into the first transparent layer 560 by the first holographic input coupler 512, and is totally internally reflected by the outermost surface 562 of the first transparent layer 560. The first optical path can include a second section in which a representation of the first light 612 reflected by the outermost surface 562 of the first transparent layer 560 exits the first transparent layer 560, passes through the first light polymer layer 510, passes through the first barrier layer 540, passes through the second light polymer layer 520, passes through the second barrier layer 550, passes through the third light polymer layer 530, enters the second transparent layer 570, and is totally internally reflected by the outermost surface 572 of the second transparent layer 570. The first optical path can include a third section in which a representation of the first light 612 reflected by the outermost surface 572 of the second transparent layer 570 exits the second transparent layer 570, passes through the third light polymer layer 530, passes through the second barrier layer 550, passes through the second light polymer layer 520, passes through the first barrier layer 540, passes through the first light polymer layer 510, enters the first transparent layer 560, and is totally internally reflected by the outermost surface of the first transparent layer 560. The first optical path can include a fourth section in which a representation of the first light 612 reflected by the outermost surface 562 of the first transparent layer 560 exits the first transparent layer 560, is reflected back into the first transparent layer 560 by the first holographic output coupler 516, and passes through the first transparent layer 560, thereby exiting the waveguide 502.

[0059] The reflective second holographic input coupler 522 and the reflective second holographic output coupler 526 can define a second optical path for a second light 614 having a wavelength within a second band entering the waveguide 502. The second optical path can include a first section in which the second light 614 passes through the first transparent layer 560, through the first photopolymer layer 510, through the first barrier layer 540, is reflected back by the second holographic input coupler 522 to the first barrier layer 540, passes through the first barrier layer 540, through the first photopolymer layer 510, enters the first transparent layer 560, and is totally internally reflected by the outermost surface 562 of the first transparent layer 560. The second optical path can include a second section in which a representation of the second light 614 reflected by the outermost surface 562 of the first transparent layer 560 leaves the first transparent layer 560, passes through the first photopolymer layer 510, through the first barrier layer 540, through the second photopolymer layer 520, through the second barrier layer 550, through the third photopolymer layer 530, enters the second transparent layer 570, and is totally internally reflected by the outermost surface 572 of the second transparent layer 570. The second optical path can include a third section in which a representation of the second light 614 reflected by the outermost surface 572 of the second transparent layer 570 leaves the second transparent layer 570, passes through the third photopolymer layer 530, through the second barrier layer 550, through the second photopolymer layer 520, through the first barrier layer 540, through the first photopolymer layer 510, enters the first transparent layer 560, and is totally internally reflected by the outermost surface 562 of the first transparent layer 560. The second optical path can include a fourth section in which a representation of the second light 614 reflected by the outermost surface 562 of the first transparent layer 560 leaves the first transparent layer 560, passes through the first photopolymer layer 510, through the first barrier layer 540, is reflected back by the second holographic output coupler 526 into the first barrier layer 540, passes through the first barrier layer 540, through the first photopolymer layer 510, and through the first transparent layer 560, thereby leaving the waveguide 502.

[0060] The reflective third holographic input coupler 532 and the reflective third holographic output coupler 536 are capable of defining a third optical path for a third light 616 having a wavelength within a third wavelength band entering the waveguide 502. The third optical path can include a first section in which the third light 616 passes through the first transparent layer 660, through the first photopolymer layer 510, through the first barrier layer 540, through the second photopolymer layer 520, through the second barrier layer 550, is reflected back into the second barrier layer 550 by the third holographic input coupler 532, passes through the second barrier layer 550, through the second photopolymer layer 520, through the first barrier layer 540, through the first photopolymer layer 510, enters the first transparent layer 560, and is totally internally reflected by the outermost surface 562 of the first transparent layer 560. The third optical path can include a second section in which the third light 616 reflected by the outermost surface of the first transparent layer 660 exits the first transparent layer 660, passes through the first photopolymer layer 510, through the first barrier layer 540, through the second photopolymer layer 520, through the second barrier layer 550, through the third photopolymer layer 530, enters the second transparent layer 570, and is totally internally reflected by the outermost surface 572 of the second transparent layer 570. The third optical path can include a third section in which the third light 616 reflected by the outermost surface of the second transparent layer 570 exits the second transparent layer 570, passes through the third photopolymer layer 530, through the second barrier layer 550, through the second photopolymer layer 520, through the first barrier layer 540, through the first photopolymer layer 510, enters the first transparent layer 560, and is totally internally reflected by the outermost surface 562 of the first transparent layer 560. The third optical path can include a fourth section in which the third light 616 reflected by the outermost surface 562 of the first transparent layer 560 exits the first transparent layer 560, passes through the first photopolymer layer 510, through the first barrier layer 540, through the second photopolymer layer 520, through the second barrier layer 550, is reflected back into the second barrier layer 550 by the third holographic output coupler 536, passes through the second barrier layer 550, through the second photopolymer layer 520, through the first barrier layer 540, through the first photopolymer layer 510, and passes through the first transparent layer 560, thereby exiting the waveguide 502.

[0061] Further, Figure 5 The first light 612, the second light 614, and the third light 616, each totally internally reflected three times within the waveguide 502, are shown. This number of reflections is merely exemplary and can be smaller or larger. For example, the light coupled into the waveguide 502 may be totally internally reflected only once, five times, ten times, twenty times, or more, depending on the circumstances of a given application.

[0062] In Figure 5In the illustrated embodiments, a corresponding photopolymer layer is provided that includes a holographic input coupler and a holographic output coupler for each band of light provided by a light source. In such embodiments, the chemistry of each photopolymer layer can be selected to optimize performance, efficiency, and responsiveness to the light of the desired band that will be guided by the corresponding photopolymer layer.

[0063] Each of input coupler 512, input coupler 522, and input coupler 532 can be laterally aligned with one another, such as along a first axis perpendicular to the first photopolymer layer 510, the second photopolymer layer 520, and the third photopolymer layer 530. Further, each of output coupler 216, output coupler 226, and output coupler 236 can be laterally aligned with one another, such as along a second axis perpendicular to the first photopolymer layer 510, the second photopolymer layer 520, and the third photopolymer layer 530.

[0064] Regardless of whether the holographic input coupler and the holographic output coupler are reflective holograms or transmissive holograms, Figure 2 、 Figure 3 、 Figure 4 and Figure 5 each of the illustrated holographic input couplers in receives input light from a light source and redirects the input light to undergo total internal reflection from the outer boundary of the transparent layer of the holographic element surrounding the waveguide. It is noted that total internal reflection within the waveguide herein can encompass total internal reflection at the boundary of the transparent layer surrounding the holographic element; total internal reflection at the holographic element itself is not required. To achieve this, each of the transparent layer, the photopolymer layer, and the barrier layer can have the same refractive index.

[0065] Figure 6 is an orthogonal front view that illustrates an exemplary waveguide 602 that implements an expander to achieve eye box expansion through exit pupil replication. Waveguide 602 includes an input coupler region 630 that receives input light 632 from a light source such as a scanning laser projector. Input coupler region 630 redirects input light 632 to travel within waveguide 602 in at least one direction. Input coupler region 630 includes a plurality of holographic input couplers that are vertically aligned with one another, such as the holographic input couplers 204, 206, 212, 214, 222, 320, 324, 512, 522, or 532 described above. In Figure 6In the example, a first set of at least one holographic input coupler redirects a first subset 632-1 of the input light 632 to travel towards the first expander region 634. A second set of the holographic input coupler redirects a second subset 632-2 of the input light 632 to travel towards the second expander region 636. As an example, the input light 632 may include a red component, a green component, and a blue component. The input coupler region 630 may include a holographic input coupler that only responds to red light, which redirects the red component of the input light 632 towards the first expander region 634. The input coupler region 630 may also include a holographic input coupler that only responds to green light, which redirects the green component of the input light 632 towards the second expander region 636. The input coupler region 630 may also include a holographic input coupler that only responds to blue light, which redirects the blue component of the input light 632 towards the second expander region 636. In this example, the first subset 632-1 of the input light 632 includes the red component of the input light 632, while the second subset 632-2 of the input light 632 includes the green component and the blue component of the input light 632.

[0066] For the purpose of emitting a pupil copy, the expander region 634 and the expander region 636 are used to form a copy of the input light 632. In Figure 6 the example, the light 632-1 travels through the waveguide 602 by total internal reflection to reach the expander region 634. The expander region 634 includes a redirector region, such as a surface relief grating or a holographic grating, which redirects the light 632-1 towards the output coupler region 640 when irradiated by the light 632-1. Further, the expander region 634 is configured such that less than 100% of the light incident thereon will be redirected. In this way, the light 632-1 can continue to travel through the waveguide 602 by total internal reflection at the surface boundary of the waveguide 602, where each time the light 632-1 irradiates on the expander region 634, a portion of the light 632-1 is redirected towards the output coupler region 640. In this way, several copies of the light 632-1 will be formed, and these copies travel towards the output coupler region 640 in a spatially separated manner. A similar discussion applies to the expander region 636, where several copies of the light 632-2 are formed, and these copies travel towards the output coupler region 640 in a spatially separated manner.

[0067] The output coupler region 640 includes a plurality of holographic output couplers 650 aligned vertically with each other, such as the above-mentioned holographic output couplers 208, 216, 218, 226, 230, 322, 326, 516, 526, or 536. In Figure 6In the example, the output coupler region 640 includes a holographic output coupler responsive to red light, a holographic output coupler responsive to green light, and a holographic output coupler responsive to blue light. Light from both expander regions 634 and 636 impinges on the holographic region 640, which redirects the light from the expander regions out of the waveguide 602. Similar to expander regions 634 and 636, the output coupler region 640 can couple out less than 100% of the light incident thereon, such that the remaining light that is not coupled out will continue to travel through the output coupler region 640 by total internal reflection. Subsequently, when this remaining light again impinges on the corresponding holographic output coupler in the output coupler region 640, another portion of the light can be coupled out. In this way, several copies of the display light can be coupled out from the waveguide 602 at spatially separated locations. This forms a display having multiple spatially separated replicated exit pupils and thus a larger eyebox compared to a single exit pupil.

[0068] Although Figure 6 illustrates separate expander regions 634 and 636 each receiving a different subset of the display light 632, in some embodiments, a single expander region can be used, where all of the display light 632 is directed towards a single expander region. Having separate expander regions advantageously allows each expander region to be specifically tuned for the wavelength of the display light that is to be directed towards it, while having a single expander region can advantageously reduce the required size of the waveguide.

[0069] Figures 7 to 13 The illustration includes embodiments of an optical combiner comprising a transparent carrier or lens structure carrying a waveguide to be positioned in a user's field of view. Although Figures 7 to 13 the illustration can correspond to one of the waveguides 116 or 118 detailed in Figure 1 or a waveguide described herein, such as Figure 2 the waveguide 202 shown in Figure 3 the waveguide 302 shown in Figure 4 the waveguide 402 shown in Figure 5 the waveguide 502 shown in Figure 6 or the waveguide 602 shown in Figures 7 to 13 any one of the waveguides 1002. Further, Figure 13 each of the transparent carriers shown in

[0070] Figure 7is a top cross-sectional view of an optical combiner 700 that includes a waveguide 1002 embedded in a transparent carrier 702. The transparent carrier 702 can be formed around the waveguide 1002 so as to completely encapsulate the waveguide 1002 within the transparent carrier 702. For example, the transparent carrier 702 can be molded into a lens around the waveguide 1002. Additionally, the transparent carrier 702 is shown as having a curved convex surface 704 and a curved concave surface 706 on a side of the optical combiner 700 opposite the curved convex surface 704. Similar convex and concave surfaces are included in other optical combiner embodiments discussed below.

[0071] Figure 8 is a top cross-sectional view of an optical combiner 800 that includes a waveguide 1002 embedded between a first component 802 of a transparent carrier 804 and a second component 806 of the transparent carrier 804. The first component 802 and the second component 806 can be formed separately and attached together around the waveguide 1002, such as using an adhesive or mechanical fasteners. Further, the first component 802 includes a curved convex surface 808, and the second component 806 includes a curved concave surface 810 on a side of the optical combiner 800 opposite the curved convex surface 808.

[0072] Figure 7 and Figure 8 both show the waveguide 1002 in direct contact with the surrounding transparent carriers 702, 804. However, in order to maintain TIR at the boundary of the waveguide 1002, the refractive index of the material outside the waveguide 1002 should be less than the refractive index of the boundary material of the waveguide 1002. This is achieved by forming the transparent carrier 702 or the transparent carrier 804 from a material having a refractive index lower than the outermost layer of the waveguide 1002.

[0073] Figure 9 is a top cross-sectional view of an optical combiner 900 illustrating a waveguide 1002 embedded in a transparent carrier 902. The transparent carrier 902 can be configured to include an air gap between the waveguide 1002 and the material forming the transparent carrier 902. Since air has a low refractive index, the air gap between the waveguide 1002 and the transparent carrier 902 will improve the efficiency of the waveguide 1002 by enhancing TIR within the waveguide 1002. A first component 904 of the transparent carrier 902 includes at least one support region 906 in contact with the waveguide 1002. The remaining portion of the first component 904 not in contact with the support region 906 is spatially separated from the waveguide 1002, resulting in an air gap 908. Similarly, a second component 910 of the transparent carrier 902 includes at least one support 912 in contact with the waveguide 1002. The remainder of the second component 910 can be spatially separated from the waveguide 1002, resulting in an air gap 914.

[0074] The support regions 906, 912 are inFigure 9 shown as the edges of the contact waveguide 1002. This can be achieved by each of the support regions 906, 912 being formed to partially surround the vertical edges 920, 922 of the waveguide 1002, or by each of the support regions 906, 912 having multiple separate supports that contact different regions of the waveguide 1002. Such supports are not limited to being positioned at the vertical edges 920, 922 of the waveguide 1002. For example, one or more supports (not shown) can be positioned closer to the center of the waveguide 1002 to provide greater stability and strength to maintain the air gaps 908 and 914.

[0075] Figure 10 is a top cross-sectional view of an optical combiner 1000 showing a waveguide 1002 embedded in a transparent carrier 1004. The transparent carrier 1004 includes a first member 1006 and a second member 1008 that surround the waveguide 1002. A plurality of beads 1010 can be positioned between the first member 1006 and the waveguide 1002 to maintain an air gap 1012 therebetween. Similarly, a plurality of beads 1010 can be positioned between the second member 1008 and the waveguide 1002 to maintain an air gap 1014 therebetween. The beads 1010 can be made of, for example, glass or plastic or the same material that forms the first or second member 1006 or 1008.

[0076] Figure 11 is a top cross-sectional view of an optical combiner 1100 showing a waveguide 1002 embedded in a transparent carrier 1102. The transparent carrier 1102 includes a first member 1104 and a second member 1106 that surround the waveguide 1002. The optical combiner 1100 includes a first separation layer 1108 and a second separation layer 1110. The first separation layer 1108 is positioned between the first member 1104 and the waveguide 1002 and is made of a low refractive index material having a refractive index lower than that of the outermost layer of the waveguide 1002 to optimize TIR within the waveguide 1002. Similarly, the second separation layer 1110 made of a low refractive index material is positioned between the second member 1106 and the waveguide 1002 to optimize TIR within the waveguide 1002.

[0077] Figure 12 is a top cross-sectional view showing an optical combiner 1200 that includes a waveguide combiner 1002 embedded in a transparent carrier 1202. The optical combiner 1200 can include any of the features of the optical combiners 700, 800, 900, 1000, or 1100 discussed above. However, the size of the waveguide 1002 relative to the transparent carrier 1202 is larger than in the previously discussed optical combiners. For example, Figures 7 to 11 discussed optical combiners 700, 800, 900, 1000, or 1100. However, the size of the waveguide 1002 relative to the transparent carrier 1202 is larger than in the previously discussed optical combiners. For example, Figure 12Illustrated is a waveguide 1002 that extends over the entire length of a transparent carrier 1202, starting flush with a first edge 1204 of the transparent carrier 1202 and extending beyond a second edge 1206 of the transparent carrier 1202. An input coupler region can be provided in a portion 1208 of the waveguide 1002 that extends beyond the edge 1206 of the transparent carrier 1202, which provides for more direct coupling of display light into the waveguide 1002.

[0078] Figure 13 is a top cross-sectional view of an optical combiner 1300 that illustrates a waveguide 1002 carried by a transparent carrier 1302. As Figure 13 shown, the transparent carrier 1302 can be planar, with the waveguide 1002 attached to a surface 1304 of the transparent carrier 1302. For example, a first transparent layer or a second transparent layer, such as Figure 2 the first and second transparent layers 260, 270 of the waveguide 202 shown in, are attached to the surface 1304 of the transparent carrier 1302 using, for example, an adhesive or mechanical fasteners. Although Figure 13 shown with the waveguide 1002 covering only a sub-segment of the surface 1304 of the transparent carrier 1302, the waveguide 1002 can alternatively cover the entire surface 1304, or can even extend beyond the surface 1304, similar to Figure 12 the waveguide 1002 illustrated in.

[0079] In some embodiments, certain aspects of the techniques described above can be implemented by one or more processors of a processing system executing software. The software includes one or more sets of executable instructions stored on or otherwise tangibly embodied in a non-transitory computer-readable storage medium. The software can include instructions and certain data that, when executed by one or more processors, manipulate the one or more processors to perform one or more aspects of the techniques described above. The non-transitory computer-readable storage medium can include, for example, a magnetic or optical disk storage device, a solid-state storage device such as flash memory, a cache, a random access memory (RAM), or one or more other non-volatile memory devices, etc. The executable instructions stored on the non-transitory computer-readable storage medium can be in source code, assembly language code, object code, or other instruction formats interpretable or otherwise executable by one or more processors.

[0080] A computer-readable storage medium can include any storage medium or combination of storage media that can be accessed by a computer system during use to provide instructions and / or data to the computer system. Such storage media can include, but are not limited to, optical media (e.g., compact disc (CD), digital versatile disc (DVD), Blu-ray disc), magnetic media (e.g., floppy disk, magnetic tape, or magnetic hard disk drive), volatile memory (e.g., random access memory (RAM) or cache), non-volatile memory (e.g., read-only memory (ROM) or flash memory), or microelectromechanical system (MEMS)-based storage media. The computer-readable storage medium can be embedded in the computing system (e.g., system RAM or ROM), fixedly attached to the computing system (e.g., magnetic hard disk drive), removably attached to the computing system (e.g., optical disc or Universal Serial Bus (USB)-based flash memory), or coupled to the computer system via a wired or wireless network (e.g., network accessible storage (NAS)).

[0081] Note that not all activities or elements described in the foregoing general description are required, some particular activities or parts of devices may not be required, and one or more additional activities or elements may be performed or included in addition to those described. Further, the order in which the activities are listed is not necessarily the order in which they are performed. Also, these concepts have been described with reference to specific embodiments. However, those of ordinary skill in the art understand that various modifications and variations can be made without departing from the scope of the present disclosure as set forth in the following claims. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present disclosure.

[0082] Advantages, other advantages, and solutions to problems have been described above with reference to specific embodiments. However, an advantage, a benefit, a solution to a problem, and any feature that may cause any advantage, benefit, or solution to occur or become more pronounced should not be construed as a critical, required, or essential feature of any or all of the claims. Further, the particular embodiments disclosed above are illustrative only and the claimed subject matter may be modified and practiced in different but equivalent manners apparent to those skilled in the art that benefit from the teachings herein. The details of the construction or design shown herein are not intended to be limiting other than as defined in the following claims. Thus, it is evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered to be within the scope of the claimed subject matter. Accordingly, the protection sought herein is set forth in the following claims.

Claims

1. A waveguide, comprising: a first photopolymer layer; a second photopolymer layer; a first barrier layer disposed between the first photopolymer layer and the second photopolymer layer; a first transparent layer; and a second transparent layer, wherein the first photopolymer layer, the first barrier layer, and the second photopolymer layer are disposed between the first transparent layer and the second transparent layer, wherein: the first photopolymer layer has a first holographic input coupler and a first holographic output coupler recorded therein, the first holographic input coupler and the first holographic output coupler being responsive to light having a wavelength in a first band and non-responsive to light having a wavelength outside the first band, and the second photopolymer layer has a second holographic input coupler and a second holographic output coupler recorded therein, the second holographic input coupler and the second holographic output coupler being responsive to light having a wavelength within a second band and non-responsive to light having a wavelength outside the second band, the second band being different from the first band.

2. The waveguide according to claim 1, wherein: the first holographic input coupler is positioned and oriented to redirect first light having a wavelength within the first band to undergo total internal reflection within the volume of the waveguide toward the first holographic output coupler; the first holographic output coupler is positioned and oriented to receive the first light from the first holographic input coupler and redirect the first light to exit the volume of the waveguide; the second holographic input coupler is positioned and oriented to redirect second light having a wavelength within the second band to undergo total internal reflection within the volume of the waveguide toward the second holographic output coupler; and the second holographic output coupler is positioned and oriented to receive the second light from the second holographic input coupler and redirect the second light to exit the volume of the waveguide.

3. The waveguide according to claim 2, wherein: the first photopolymer layer has a third holographic input coupler and a third holographic output coupler recorded therein, the third holographic input coupler and the third holographic output coupler being responsive to light having a wavelength in a third band and non-responsive to light having a wavelength outside the third band, the third band being different from the first band and the second band; the third holographic input coupler is positioned and oriented to redirect third light having a wavelength within the third band to undergo total internal reflection within the volume of the waveguide toward the third holographic output coupler; and the third holographic output coupler is positioned and oriented to receive the third light from the third holographic input coupler and redirect the third light to exit the volume of the waveguide.

4. The waveguide according to claim 3, wherein, the first band, the second band, and the third band do not overlap.

5. The waveguide according to claim 3, wherein: the first photopolymer layer and the second photopolymer layer are parallel to each other; The first holographic input coupler, the second holographic input coupler, and the third holographic input coupler are aligned with each other along a first axis orthogonal to the first photopolymer layer and the second photopolymer layer; and The first holographic output coupler, the second holographic output coupler, and the third holographic output coupler are aligned with each other along a second axis orthogonal to the first photopolymer layer and the second photopolymer layer.

6. The waveguide according to claim 1, wherein, each of the first photopolymer layer, the second photopolymer layer, the first barrier layer, the first transparent layer, and the second transparent layer has the same refractive index, and light that undergoes total internal reflection within the volume of the waveguide is reflected away from the outermost surfaces of the first transparent layer and the second transparent layer.

7. The waveguide according to claim 1, further comprising: a third photopolymer layer; and a second barrier layer disposed between the second photopolymer layer and the third photopolymer layer, wherein the second barrier layer and the third photopolymer layer are disposed between the first transparent layer and the second transparent layer.

8. The waveguide according to claim 7, wherein: The first photopolymer layer has a first holographic input coupler and a first holographic output coupler recorded therein, the first holographic input coupler and the first holographic output coupler being responsive to light having a wavelength within a first wavelength band and non-responsive to light having a wavelength outside the first wavelength band; The second photopolymer layer has a second holographic input coupler and a second holographic output coupler recorded therein, the second holographic input coupler and the second holographic output coupler being responsive to light having a wavelength within a second wavelength band and non-responsive to light having a wavelength outside the second wavelength band, the second wavelength band being different from the first wavelength band; and The third photopolymer layer has a third holographic input coupler and a third holographic output coupler recorded therein, the third holographic input coupler and the third holographic output coupler being responsive to light having a wavelength within a third wavelength band and non-responsive to light having a wavelength outside the third wavelength band, the third wavelength band being different from the first wavelength band and the second wavelength band.

9. The waveguide according to claim 8, wherein: The first holographic input coupler is positioned and oriented to redirect first light having a wavelength within the first wavelength band to undergo total internal reflection within the volume of the waveguide toward the first holographic output coupler; The first holographic output coupler is positioned and oriented to receive the first light from the first holographic input coupler and redirect the first light to exit the volume of the waveguide; The second holographic input coupler is positioned and oriented to redirect second light having a wavelength within the second wavelength band to undergo total internal reflection within the volume of the waveguide toward the second holographic output coupler; and The second holographic output coupler is positioned and oriented to receive the second light from the second holographic input coupler and redirect the second light to exit the volume of the waveguide; The third holographic input coupler is positioned and oriented to redirect third light having a wavelength within a third wavelength band to undergo total internal reflection within the volume of the waveguide toward the third holographic output coupler; and The third holographic output coupler is positioned and oriented to receive the third light from the third holographic input coupler and redirect the third light to exit the volume of the waveguide.

10. The waveguide according to any one of claims 1-9, wherein, each of the first photopolymer layer, the second photopolymer layer, the first barrier layer, the first transparent layer, and the second transparent layer is planar.

11. A waveguide, comprising: a first transparent layer; a first photopolymer layer carried by the first transparent layer; a barrier layer carried by the first photopolymer layer; a second photopolymer layer carried by the barrier layer; and a second transparent layer carried by the second photopolymer layer, wherein: the first photopolymer layer has a first holographic input coupler and a first holographic output coupler recorded therein, the first holographic input coupler and the first holographic output coupler being responsive to light having a wavelength within a first wavelength band and non-responsive to light having a wavelength outside the first wavelength band, and the second photopolymer layer has a second holographic input coupler and a second holographic output coupler recorded therein, the second holographic input coupler and the second holographic output coupler being responsive to light having a wavelength within a second wavelength band and non-responsive to light having a wavelength outside the second wavelength band, the second wavelength band being different from the first wavelength band.

12. The waveguide according to claim 11, wherein: the first holographic input coupler is positioned and oriented to redirect first light having a wavelength within the first wavelength band to undergo total internal reflection within the volume of the waveguide toward the first holographic output coupler; the first holographic output coupler is positioned and oriented to receive the first light from the first holographic input coupler and redirect the first light to exit the volume of the waveguide; the second holographic input coupler is positioned and oriented to redirect second light having a wavelength within the second wavelength band to undergo total internal reflection within the volume of the waveguide toward the second holographic output coupler; and the second holographic output coupler is positioned and oriented to receive the second light from the second holographic input coupler and redirect the second light to exit the volume of the waveguide.

13. The waveguide according to claim 12, wherein: The first photopolymer layer has a third holographic input coupler and a third holographic output coupler recorded therein. The third holographic input coupler and the third holographic output coupler respond to light having a wavelength within a third wavelength band and do not respond to light having a wavelength outside the third wavelength band, where the third wavelength band is different from the first wavelength band and the second wavelength band; The third holographic input coupler is positioned and oriented to redirect a third light having a wavelength within the third wavelength band to undergo total internal reflection within the volume of the waveguide toward the third holographic output coupler; And The third holographic output coupler is positioned and oriented to receive the third light from the third holographic input coupler and redirect the third light to exit the volume of the waveguide.

14. The waveguide according to claim 13, wherein, the first wavelength band, the second wavelength band, and the third wavelength band do not overlap.

15. The waveguide according to claim 13, wherein: the first photopolymer layer and the second photopolymer layer are parallel to each other; the first holographic input coupler, the second holographic input coupler, and the third holographic input coupler are laterally aligned with each other; And the first holographic output coupler, the second holographic output coupler, and the third holographic output coupler are laterally aligned with each other.

16. The waveguide according to claim 11, wherein, each of the first photopolymer layer, the second photopolymer layer, the barrier layer, the first transparent layer, and the second transparent layer has the same refractive index, and the light undergoing total internal reflection within the volume of the waveguide is reflected away from the outermost surfaces of the first transparent layer and the second transparent layer.

17. The waveguide according to claim 11, wherein, each of the first photopolymer layer, the second photopolymer layer, the barrier layer, the first transparent layer, and the second transparent layer is planar.

18. The waveguide according to any one of claims 11 to 17, wherein, the waveguide is disposed between a first curved surface and a second curved surface of a transparent carrier material to form an optical combiner.

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