High transmission eyepiece architecture

Abstract

An eyepiece includes a substrate, an in-coupling grating on a first side of the substrate; and a deformed grating comprising a characteristic located on at least the first side of the substrate and comprising a primary grating and a secondary grating. The primary and secondary gratings may differ in pitch, orientation, and size.

Description

[0001] Priority claim

[0002] This application claims priority under 35 USC §119(e) to U.S. Patent Application No. 63 / 359,194, filed on July 7, 2022, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The embodiments described herein generally relate to high transmission eyepiece architectures. Background Art

[0004] Waveguides used for augmented reality eyepiece displays have a high refractive index associated with the surface relief pattern and substrate, both of which are criteria for achieving a large field of view with good image brightness and uniformity of displayed digital content. Summary of the invention

[0005] The present disclosure generally describes methods and systems for a high transmission eyepiece architecture having an attached, morphed, or stacked secondary grating and primary grating to improve the transmission and back reflection characteristics of the eyepiece without compromising display performance. The secondary grating can have a smaller pitch relative to the primary grating. The primary and secondary gratings can be one-dimensional (1D) or two-dimensional (2D).

[0006] As described herein, when multiple 1D or 2D gratings with a small pitch (e.g., lattice periodicity of the gratings) are stacked on top of a primary diffraction grating for displaying digital content, the transmission to reflection ratio of the eyepiece can be increased by 5 to 10 times, e.g., the transmission coefficient is increased, the back reflection coefficient is reduced, or both.

[0007] Specific embodiments of the subject matter described in this specification can achieve one or more of the following advantages. First, stacking selected short-pitch gratings, using a specific combination of deformed gratings and diffractive optical elements can help improve see-through transmission and back reflection performance without compromising display performance. Second, in some cases, using the gratings described herein can further improve display performance.

[0008] The details of one or more embodiments of the subject matter of this specification are set forth in the detailed description, claims, and drawings. A person skilled in the art will clearly understand other features, aspects, and advantages of the subject matter from the detailed description, claims, and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figures 1A-1C 1 and 2 are schematic diagrams of photos respectively showing views captured by first to third augmented reality head mounted devices according to an embodiment of the present disclosure.

[0010] Figure 1D is a schematic diagram of a photograph of a laboratory environment according to an embodiment of the present disclosure.

[0011] Figure 2A Depicted is a cross-sectional view of an eyepiece in accordance with an embodiment of the present disclosure.

[0012] Figure 2B Describes an embodiment of the present disclosure. Figure 2A Momentum space diagram of light propagating in the eyepiece.

[0013] Figure 2C and 2D The embodiments according to the present disclosure are respectively described. Figure 2A Plan view of the front and back sides of the eyepiece.

[0014] Figure 3A and 3B Depicted is an architecture according to an embodiment of the present disclosure and two examples of supporting virtual images with a large field of view.

[0015] Figure 3C Including embodiments according to the present disclosure Figure 3A and Figure 3B Legend for .

[0016] FIG. 4A to FIG. 4D Depicted are plan views of examples of eyepieces incorporating different optical elements in accordance with embodiments of the present disclosure.

[0017] Figures 4E to 4G According to the embodiments of the present disclosure, Figures 4A to 4D Simulation of back reflections for the first to third eyepieces discussed.

[0018] FIG. 5A to FIG. 5G Depicted is a cross-sectional view of an example of an architecture including a morphed grating in accordance with an embodiment of the present disclosure.

[0019] Figure 6 is a perspective view of an architecture of FIG. 5 according to an embodiment of the present disclosure.

[0020] FIG. 7A to FIG. 7B Depicted are graphs showing the effect of different deformed gratings on the momentum of light traveling in the eyepiece in accordance with an embodiment of the present disclosure.

[0021] Figure 8 Depicted are graphs showing the effect of different deformed gratings on the momentum of light traveling in the eyepiece in accordance with an embodiment of the present disclosure.

[0022] 9A to 9FDepicted are graphs showing the effect of different deformed gratings on the momentum of light traveling in the eyepiece in accordance with an embodiment of the present disclosure.

[0023] Fig.10 Describes an embodiment of the present disclosure Figures 9A to 9F A plot of the simulated transmission profile of the eyepiece versus wavelength.

[0024] Fig.11A and 11B Depicts the transverse magnetic (TM) and transverse electric (TE) polarized light according to embodiments of the present disclosure, respectively. Figures 9A to 9F A plot of the simulated reflectance distribution of the eyepiece versus wavelength.

[0025] Fig.12 Depicted are graphs of transmittance versus wavelength for normally incident s-polarized and p-polarized light for an eyepiece with and without a recycler according to an embodiment of the present disclosure.

[0026] Figures 13A to 13F The embodiments according to the present disclosure are respectively described. 9A to 9F Far-field efficiency distribution pattern for the large field of view associated with the eyepiece.

[0027] Figure 13G and 13H Virtual image uniformity of a controlled and deformable grating eyepiece, respectively, is depicted according to an embodiment of the present disclosure.

[0028] FIG. 14A to FIG. 14F A schematic diagram depicting an example of a manufacturing process for a deformed grating according to an embodiment of the present disclosure is depicted.

[0029] Figures 15A-15F A schematic diagram depicting an example of a manufacturing process for manufacturing a deformed grating using an intermediate mask layer according to an embodiment of the present disclosure.

[0030] FIG. 16A to FIG. 16F A schematic diagram depicting an example of a manufacturing process for a deformed grating with a graded primary grading according to an embodiment of the present disclosure is depicted.

[0031] FIG. 17A to FIG. 17F A schematic diagram depicting an example of a manufacturing process for a deformed grating according to an embodiment of the present disclosure, wherein both the primary and secondary gratings are graded.

[0032] 18A to 18F A schematic diagram depicting an example of a manufacturing process of a deformed grating according to an embodiment of the present disclosure, wherein the primary grating is a sawtooth grating.

[0033] Fig.19AAn example of an eyepiece including a secondary grating is depicted in accordance with an embodiment of the present disclosure.

[0034] Fig.19B An example of a stacked grating in accordance with an embodiment of the present disclosure is depicted.

[0035] Fig. 20A An example of a stacked grating according to an embodiment of the present disclosure is depicted. Fig. 20B A diagram depicting an embodiment of the present disclosure is shown, wherein Fig. 20A Transmission profiles of the stacked gratings versus wavelength for five versions of the second refractive index.

[0036] Like reference numbers and designations in the various drawings indicate like elements. DETAILED DESCRIPTION

[0037] The following detailed description describes a high transmission eyepiece architecture and is presented to enable a person skilled in the art to make and use the disclosed subject matter in the context of one or more specific embodiments. Various modifications, changes, and substitutions may be made to the disclosed embodiments, and these modifications, changes, and substitutions are obvious to those of ordinary skill in the art, and the general principles defined may be applied to other embodiments and applications without departing from the scope of the present disclosure. In some cases, one or more technical details may be omitted that are not necessary for understanding the subject matter and are within the skill of those of ordinary skill in the art so as not to obscure one or more of the embodiments. The present disclosure is not intended to be limited to the embodiments described or shown, but is intended to be given the widest scope consistent with the principles and features described.

[0038] A single waveguide with a larger refractive index or a stack of multiple waveguides with a larger refractive index may produce poor see-through transmission and significant back reflections. The low transmission to reflection ratio may make such eyepieces less than ideal for use with or without virtual content.

[0039] Figures 1A-1C 100a - 100c are schematic diagrams of photographs respectively showing views captured through first to third head mounted devices according to an embodiment of the present disclosure. Figure 1A The first head mounted device view shown in includes a stack of high refractive index waveguides with EPE. Figure 1B The second head mounted device view shown in has a hollow frame in the eyepiece, e.g., without a waveguide. The third head mounted device is similar to the first head mounted device, but has a different form factor.

[0040] Figure 1D It is used for shooting Figure 1CIllustration 100d of a photograph of a laboratory environment, for example, a room with a checkerboard pattern placed behind first to third head-mounted devices.

[0041] from Figure 1A and 1C As can be seen in Figure 1, although high-refractive-index waveguides can expand the field of view (FOV), using high-refractive-index waveguides in the eyepieces of augmented reality headsets can be problematic. First, high-refractive-index waveguides can reduce the light transmission of the "real scene" that the user is viewing. Figure 1A and 1B , Figure 1A It appears darker because the high refractive index waveguide in the eyepiece of the first head mounted device reduces the light transmission from the "real world" (e.g., the scene with the augmented reality image added in). For example, the light transmission rate of the first head mounted device can be 60% to 65% or less.

[0042] Second, back reflections and rainbow artifacts can obstruct the user’s viewing experience. Figure 1A and 1C As can be seen in the figure, a rainbow flare 102 from the light projection system appears in the photo, but Figure 1B In addition, Figure 1D The chessboard 104a in (located behind the third head mounted device) is Figure 1C 104b. For example, the reflection coefficient of light incident on the waveguide stack at an angle between 0 and 30° may be about 30%. Because the user's face exists, the acceptance angle of the area near the user's temple is larger than the acceptance angle of the area near the nose, so the back reflection may be worse in the part of the FOV near the user's temple than near the user's nose.

[0043] Using sub-wavelength 1D or 2D gratings (e.g., having a pitch or period less than the wavelength of the incident light) can reduce back reflections that occur when light encounters a high refractive index material from a low refractive index vacuum or air. However, adding additional (e.g., secondary) gratings to reduce back reflections can negatively impact the display performance of the eyepiece. The present disclosure provides eyepieces with primary and secondary gratings that are configured to reduce back reflections, increase transmission, or both without negatively impacting the augmented reality display.

[0044] Figure 2A A cross-sectional view of an eyepiece 200a according to an embodiment of the present disclosure is depicted. The eyepiece 200a includes an input coupling grating (ICG) 202, a primary grating 204, and a substrate 206. In the present disclosure, the primary grating refers to an exit pupil expander (EPE), an orthogonal pupil expander (OPE), and a combined pupil expander (CPE).

[0045] ICG 202 couples light from the projector into substrate 206, which may have a high refractive index, for example, n ≥ 2. ICG 202 couples the light at an angle such that the incoupled light propagates within substrate 206 by total internal reflection (TIR).

[0046] The primary grating 204 is graded, for example, the height of each row 208 increases gradually from right to left, from a first value to a second value. Although the middle portion of the primary grating is graded, the ends may have a constant height equal to the first value and the second value, respectively. In some embodiments, the shape of the primary grating 204 is a binary square ridge.

[0047] Figure 2B Describes an embodiment of the present disclosure. Figure 2A Momentum space diagram 200b of light propagating in eyepiece 200. The parameters of eyepiece 200a (e.g., the refractive index of substrate 206 and the pitch of the primary grating) determine the allowed wave vectors (e.g., k-vectors) for light propagating through substrate 206. For example, corresponding to the phase wavefront (~e ik·r-iωt ) depends on the refractive index of the material through which it propagates, i.e., the momentum is proportional to the refractive index.

[0048] As another example, the magnitude of the wave vector representing the change in momentum from the grating is inversely proportional to the pitch of the grating. Figure 2B , inner circle 212 represents the momentum of light for all incident angles (e.g., 360° around the circle) when propagating in a material with n=1 (e.g., air). Outer circle 214 represents the momentum of light for all physically possible angles when propagating in a material with n=2 (e.g., substrate 206).

[0049] The barrel box represents the state of the FOV 216 as it is incoupled and outcoupled through the substrate 206. When light is incoupled by the ICG 202 and interacts with the primary grating 204, the momentum of the light changes. For example, incoupling into the substrate 206 increases the FOV that was originally located at the center of the inner circle (e.g., k x ,k y =(0,0) as the center of the FOV) so that it is located in the ring between the inner circle 212 and the outer circle 214. Arrow 218 represents the change in momentum due to incoupling, which is related to k icg Proportional.

[0050] As light propagates in substrate 206 using TIR, the light periodically interacts with primary grating 204. The parameters of primary grating 204 determine how the momentum of the light changes when it encounters primary grating 204. For example, the pitch and orientation can determine the size and orientation of the k-vector k1 215 representing the change. In addition, light can travel at integer multiples of k1 (e.g., high order and negative values).

[0051] In some embodiments, the primary grating 204 has two layers, for example, diffraction gratings with different periods and pitches on each side of the substrate 206. Therefore, for a two-layer primary grating, there are additional k-vectors, such as k2 217, which are also determined by the pitch and orientation, which represent the change in the momentum of the incoupled light.

[0052] In some embodiments, the grating of the primary grating 204 is 2D, for example, formed by discrete columns rather than continuous rows. When the grating is 2D, the additional k-vectors k2 217 correspond to different changes in the momentum of the propagating light. When one side of the substrate has a 2D primary grating 204, the other side of the substrate can be patterned with an anti-reflective (AR) nano-pattern or a multi-layer AR film coating to reduce reflection losses of "real world" light to compensate for the absence of a primary grating on each side.

[0053] As will be discussed later, the anti-reflective nanopattern can also affect the momentum of light propagating in the substrate. For anti-reflective (AR) coatings made of short pitch (shorter than the wavelength) diffraction grating structures, anti-reflective properties can be achieved by stacking and / or deforming such gratings with the primary diffraction grating of the eyepiece. The associated grating vectors can be selected to avoid interfering with the function of the primary diffraction grating described above.

[0054] In some embodiments, a single eyepiece combines multiple layers of primary gratings and 2D primary gratings. For example, an area of ​​the eyepiece near the user's temple can receive higher intensity light over a larger angle range. Therefore, the area of ​​the eyepiece near the temple can have a 2D CPE on one side and a 1D diffractive structure on the other side. The rest of the eyepiece (the area near the user's pupil and nose) can have a 1D diffractive structure on both sides to have high optical efficiency near the user's pupil.

[0055] By translating from an initial FOV within inner circle 212 to various positions within the ring between inner circle 212 and outer circle 214, the emitted light (e.g., light projected into ICG 202) is spread over a larger area for people to expand. Primary grating 204 also outcouples light so that an increased FOV reaches the user.

[0056] Dashed arrows 219 and 221 represent k-vectors k2 and k1 of primary grating 204, respectively, out-coupling light to the user's pupil, enabling the user to view digital content. In some embodiments, the out-coupled light propagates at an angle equal to the angle of incidence of light from the projector onto ICG 202.

[0057] Figure 2C and 2D The embodiments according to the present disclosure are respectively described. Figure 2A Plan views 200c and 200d of the front and back sides of the eyepiece 200a. Arrows 220 and 222 depict the direction of gradation, e.g., the direction in which the height of the rows of diffraction gratings on each side of the substrate varies. For example, the gradation may have 16 regions 226 of different heights. Plan view 200c shows a first side of the eyepiece 200 having a diffraction grating characterized by a k-vector k1. Plan view 200d shows a second side of the eyepiece 200a having a diffraction grating characterized by a k-vector k2. The second side of the eyepiece also includes a recycler 224, whose function is to "recycle" light back into the eyepiece when the light reaches a certain position in momentum space, which would otherwise leave the FOV after another interaction with the primary grating 204. In some embodiments, the recycler 224 is a diffraction grating whose pitch and orientation are determined by the parameters of the diffraction gratings that make up the primary grating 204. For example, the recycler k rec The k vector of can be equal to the difference between k1 and k2. The grating pitch of the recycler 224 can be half the grating pitch of the primary grating. In some embodiments, k icg The sum of k1, k2 and k3 is zero, which ensures that the light will exit the ICG 202 at the same angle as it entered from the projector.

[0058] 1.0 Case 1: Additional Optical Components

[0059] The first method is to supplement the primary grating with a secondary grating as shown below.

[0060] Figure 3A and 3B Depicted are two examples of architectures 300 and 301 supporting virtual images with large FoV according to embodiments of the present invention. Figure 3CA key 303 is included to explain the symbols for each type of optical element in architectures 300 and 301. Key 303 includes 1D or 2D ICG 302 represented by right triangles, 1D CPE / OPE / EPE 304 represented by square ridges, 2D CPE / OPE / EPE 306 represented by wide ridges with a coating between each ridge, 1D recycler 308 represented by square ridges with diagonal markings, and 1D or 2D anti-reflection grating 310 represented by narrow ridges. The features in key 303 can independently be 1D binary lines and spaces or other 1D structures or 2D structures, such as holes and pillars or other 2D structures.

[0061] For example, the architecture 300 is an eyepiece having a 2D CPE / OPE / EPE 306 (e.g., a multi-layer CPE), wherein at least two wave vectors characterize the CPE / OPE / EPE. On the side of the substrate 312 opposite the CPE / OPE / EPE 306 is an anti-reflection grating 310, which is opposite both the CPE / OPE / EPE 306 and the ICG 302. In some embodiments, the architecture 300 makes the temple side (e.g., the side with the AR grating 310) of the substrate 312 (e.g., a transparent waveguide) less reflective than a 1D diffraction pattern on both sides (e.g., on both sides of the substrate 312), which can result in higher reflectivity for incident angles of 0 to 60° for world light.

[0062] As another example, architecture 301 includes a combination of 1D and 2D CPE / OPE / EPE 304 and 306. A first side of substrate 312 is ICG 302, 2D CPE / OPE / EPE 306, and 1D CPE / OPE / EPE 304. A second side of substrate 312 opposite the first side includes anti-reflection grating 310 below ICG 302 and 2D CPE / OPE / EPE 306, 1D CPE / OPE / EPE 304 below the 1D CPE / OPE / EPE 304 on the first side, and a 1D recycler partially below a portion of the 1D CPE / OPE / EPE 304 on the first side.

[0063] Figures 4A to 4D Plan views 400a to 400d of examples of eyepieces incorporating different optical elements in accordance with embodiments of the present disclosure are depicted. Plan views 400a and 400b are the world side of the eyepiece, e.g., the side closer to the scene viewed by the user, while plan views 400c and 400d are the eye side, e.g., the side closer to the user's eyes.

[0064] Figure 4A and 4CThe world side and eye side of the first eyepiece "D79" are depicted respectively, wherein the world side has a graded 1D CPE and the eye side has a graded 1D CPE and a recycler. Figure 4B and 4D The world side and eye side of a second eyepiece "D79A" are depicted, respectively, wherein a 2D CPE replaces a portion 402 of a 1D CPE on the world side, and an AR grating replaces a portion 404 of a 1D CPE on the eye side. Although not depicted, a third eyepiece "D79B" may include portions 402 and 404, each of which is replaced by a 1D grating with square ridges, such as a half-pitch grating.

[0065] Figures 4E to 4G About Figures 4A to 4D Simulated graphs 400e-400g of back reflection versus wavelength for the first to third eyepieces (e.g., D79, D79A, and D79B) discussed in FIG. Graphs 400e-400g include simulated graphs of s-polarized light and p-polarized light incident at 20°, 40°, and 60°, respectively.

[0066] from Figures 4E to 4G It can be seen that the reflectance of p-polarized light is generally greater than that of s-polarized light. Generally, the reflectance increases or tends to be stable as the wavelength increases.

[0067] Figures 4E to 4G It is shown that, according to an embodiment of the present disclosure, the reflectance as a function of wavelength depends on the angle of incidence. Note that Figures 4E to 4G The scale of the y-axis of each graph in FIG is different. For p-polarized light, the reflectance increases as the incident angle increases from 20° to 60°, while for s-polarized light, the reflectance decreases as the incident angle increases from 20° to 60°.

[0068] In addition, the reflection coefficient of the second eyepiece D79A is usually the lowest, while the reflection coefficient of the first eyepiece D79 is the largest, which indicates that the architecture of the second eyepiece can best reduce the unwanted back reflections of the three eyepieces. However, the associated AR grating vector of the optical element of the second eyepiece D79A may interfere with the function of the CPE, so the design and parameters of the AR grating are very important.

[0069] 2.0 Case 2: Combining Deformed Grating Optical Elements

[0070] A second approach is to use a deformed grating, ie, a grating having both primary and secondary grating characteristics.

[0071] Figures 5A to 5G Depicts cross-sectional views 500a-500g of examples of architectures 500a, 500b, 500c, 500d, 500e, 500f, and 500g including deformed gratings according to embodiments of the present disclosure. The same legend 303 in FIG. 3 applies to Figures 5A to 5G Note that tags 602 and 604 are included to provide Figure 6 Further references and perspectives described in .

[0072] In some embodiments, such as architectures 500a, 500b, 500c, 500d, 500e, 500f, and 500g, the eyepiece area in front of the user's eyes can include a primary grating on each side that includes CPE / EPE / OPE features, such as 1D rows or 2D holes and / or columns combined with 1D or 2D AR elements. In some embodiments, such as architecture 500f, the eyepiece area in front of the user's eyes can include a primary grating on each side that includes CPE / EPE / OPE features, such as 1D rows or 2D holes and / or columns combined with 1D recycler elements. Combining CPE / EPE / OPE features with recycler elements on each side can improve the transmission to reflection ratio and other virtual image key point metrics, such as improved image uniformity, compared to architectures lacking anamorphic optical elements.

[0073] Although the cross-sectional view of architecture 500b depicts a repeating pattern of primary grating 602 and secondary grating 604 (such that the primary grating and secondary grating appear aligned), primary grating 602 and secondary grating 604 may be oriented at a non-zero angle relative to each other.

[0074] Figure 6 5 is a perspective view 600 of the architecture 500b of FIG. 5 according to an embodiment of the present disclosure. The architecture 504 includes a primary grating 602 (labeled in FIG. 5 ) and a secondary grating 606 (labeled in FIG. 5 ). As can be seen from the perspective view 600, the primary grating 602 and the secondary grating 604 can have different orientations and pitches. For example, the primary grating 602 is oriented perpendicular to the direction of each row of the primary grating 602 (e.g., along arrow 610 ) and has a pitch indicated by arrow 612. The secondary grating 604 is oriented perpendicular to the direction of each row of the secondary grating 604 (e.g., along arrow 614 ) and has a pitch indicated by bracket 616. Therefore, other architectures may also include primary gratings and secondary gratings oriented at non-zero angles relative to each other.

[0075] Figure 6 It is shown that the deformed grating can have the characteristics of both the primary grating 602 and the secondary grating 604, such as two orientations and two pitches that characterize the deformed grating. In other words, the characteristics of the primary grating or the secondary grating alone cannot fully capture the shape of the deformed grating.

[0076] Deformable diffraction gratings pose some challenges for augmented reality eyepieces. For example, depending on the parameters of the deformable anti-reflection grating, the user can see multiple shifted copies of the same digital content.

[0077] Figures 7A to 7B Figures 700a-700b are depicted showing the effect of a deformed grating on the momentum of light traveling in the eyepiece according to an embodiment of the present disclosure. In both Figures 700a and 700b, the secondary grating (e.g., an AR grating) corresponds to a k-vector along the x-axis. However, the magnitude of the k-vector is different. In Figure 700a, the k-vector of the secondary grating k AR 702 translates FOV 700 from the ring between inner circle 701 and outer circle 703 to outside outer circle 701. However, the negative version of k-vector k1 705 (e.g., k-vector 706) translates the FOV to be partially inside inner circle 703. Then, the negative version of k-vector k2 707 (e.g., k-vector 708) translates the FOV to be partially inside and outside inner circle 703, which results in different versions of the extended FOV being coupled out to the user's eyes at different angles because some FOVs do not interact with the recycler.

[0078] To avoid this problem, for example, to outcouple the same FOV at different angles, the secondary grating vector may have a momentum shift outside the outer circle 701. As shown in diagram 700b, the k-vector k of the secondary grating is AR 710 also translates the FOV 700 from the ring between the inner circle 701 and the outer circle 703 to outside the outer circle 701. However, neither the negative version of the k-vector k1 712 nor k2 713 (e.g., k-vector 714) can translate the FOV back into the outer circle 701, indicating that the k-vector is allowed to propagate within the substrate with a refractive index of n=2. Therefore, in some embodiments, the secondary grating vector can have a minimum pitch to ensure that light that interacts with the secondary grating does not end up outcoupled at an incorrect angle. For example, the pitch of the secondary grating can be smaller than the pitch of the primary grating by a factor of at least twice the refractive index of the substrate, because the refractive index of the substrate determines the size of the outer circle 701.

[0079] Figure 8 A graph 800 showing the effect of different deformed gratings on the momentum of light traveling in the eyepiece is depicted in accordance with an embodiment of the present disclosure. Another way to avoid the problem of outcoupling the same FOV at different angles is to select a secondary grating vector that is a linear combination of the primary grating vectors k1 and k2. For example, secondary grating vector 802 is equal to k1+k2, secondary grating vector 804 is equal to k1-k2, and secondary grating vector 806 is equal to 2×k1( Fig. 7A and 7B800). As shown in diagram 800, secondary grating vectors 802, 804, and 806 translate FOVs 808 and 810 to another value within the ring between inner circle 812 and outer circle 814. In other words, choosing the secondary grating k-vector as a linear combination of the primary grating k-vectors ensures that the momentum generated by the interaction with the deformed grating shift is outside the inner circle. For example, in direct space, this translation is a design choice to determine the length of the secondary grating. Therefore, only FOVs propagating at the correct angle will be outcoupled. In addition, if the grating pitch of the secondary grating is smaller than the wavelength, the secondary grating can also be used as an anti-reflection grating, thereby improving transmission and reducing back reflections.

[0080] 2.1 Simulation-based Evidence of Transmission Improvement and Backreflection Mitigation

[0081] Figures 9A to 9F Depicted are graphs 900a through 900f showing the effect of a deformed grating on the wave vector of light traveling in a corresponding eyepiece, in accordance with an embodiment of the present disclosure. In each of graphs 900b through 900f, the solid line represents the k-vector of the primary grating. In each of graphs 900b through 900f, the dashed line represents the k-vector of the secondary grating. Graph 900a shows an eyepiece without a secondary grating.

[0082] Fig.10 The embodiment according to the present disclosure is shown Figures 9A to 9F Graph of the simulated transmission distribution of the eyepiece versus wavelength in 1000. Fig.10 In , light is incident from the world at an angle of 10°, where some light is reflected back to the world and some light is transmitted to the user. Each distribution D_A, D_B, D_C, D_D, D_E, and D_F corresponds to Figures 9A to 9F The grating k-vector in . Eyepieces without a secondary grating have the lowest transmission in most of the visible wavelength range (e.g., λ>0.5 microns). Therefore, in general, including Figures 9B to 9F One of the secondary gratings shown may improve (e.g., increase) the transmittance of the eyepiece.

[0083] Fig.11A and 11B Depicted are the TM and TE polarized light according to the embodiments of the present disclosure. Figures 9A to 9F The relationship between the simulated reflection distribution of the eyepiece and the wavelength in Figures 1100a and 1100b. In Figures 1100a and 1100b, light is incident from the user side at an angle of 30°, where some light is reflected back to the user and some light is transmitted to the world. Each distribution D_A, D_B, D_C, D_D, D_E, D_F corresponds to Figures 9A to 9F The eyepiece without a secondary grating has the highest reflectance distribution over the entire wavelength range. Therefore, including Figures 9B to 9FOne of the secondary gratings shown can improve (e.g., reduce) back reflections from the eyepiece. Compared to an eyepiece without the deformable grating, Fig.10 , 11A The combined effect of the transmission and reflection ratios shown in FIG. 11B can increase this ratio by up to 10 times.

[0084] In some embodiments, the light projection system has three channels, such as R, G, and B. Therefore, each active layer (e.g., a deformed grating layer of a particular channel) can be adjusted according to the reflection and transmission distribution as a function of wavelength. For example, the deformed grating of the red channel can have different parameters, such as grating pitch, shape, height, and orientation compared to the deformed grating of the blue channel.

[0085] In some embodiments, the transmission profile of the eyepiece can be increased using only a single active layer of deformable grating.

[0086] Fig.12 Depicted is a graph 1200 of transmission versus wavelength for normally incident s-polarized and p-polarized light for eyepieces with and without a recycler (e.g., "D79" and "D79_REC") in accordance with an embodiment of the present disclosure. As shown, when a deformed grating (a combination of a primary grating and a recycler) is present, transmission for both polarization types increases. The average transmission for the eyepiece without the deformed grating is 86.7% across all wavelengths and polarizations, while the average transmission for the eyepiece with the deformed grating is 93.1%.

[0087] Fig.10 , 11A , 11B, and 12 were generated using simulation software. The simulation software approximates how the deformable grating affects the display performance. The software handles full ray tracing for all incident angles to simulate the display performance of the eyepiece. Based on ray tracing simulations using basic Maxwell equations, the efficiency distribution for different incident angles within the FOV can be analyzed.

[0088] Figures 13A to 13F The embodiments according to the present disclosure are respectively described. Figures 9A to 9F Far-field efficiency distribution patterns 1300a1 to 1300f2 for a large FOV associated with the eyepiece. Figures 13A to 13F The FOV represented in spans 53° by 53°.

[0089] The performance indicators associated with FOV include user side (U EBE ) and the world side (W EBE ) overall transmission efficiency, 80% FOV (U inner80 ) and full FOV (U fov) uniformity score. The uniformity score is the ratio of the difference between the 80th percentile and the 20th percentile values ​​to the 50th percentile (median) value. The distribution pattern on the left is the original image, and the second distribution pattern on the right is gamma corrected, which reduces the contrast. The center-to-peak (CP) ratio, such as the value at the center divided by the maximum efficiency within the full FOV, can characterize the uniformity of the pattern. For example, an ideal CP ratio for an AR image can be 1, while the CP ratio of pattern 1300a2 is 0.62.

[0090] For pattern 1300a1, U EBE =4.66%, W EBE =4.63%, U inner80 =1.610, and U fov =2.954. For pattern 1300b1, U EBE =3.91%, W EBE =3.13%, U inner80 =1.856, and U fov =3.847. For pattern 1300c1, U EBE =3.90%, W EBE =3.32%, U inner80 =1.423, and U fov =2.704. For pattern 1300d1, U EBE =2.49%, W EBE =2.13%, U inner80 =1.352, and U fov =2.552. For pattern 1300e1, U EBE =2.98%, W EBE =3.1119%, U inner80 =1.659, and U fov =3.119. For pattern 1300f1, U EBE =3.67%, W EBE =3.13%, U inner80 =1.291, and U fov =2.704.

[0091] In patterns 1300b1-1300f1, the efficiency U EBE and W EBE The efficiency is slightly lower than that of the pattern 1300a1, for example, by about 1% to 2%. The uniformity U of the patterns 1300c1, 1300d1, and 1300f1 is inner80 and U fov Compared with pattern 1300a1, the uniformity of patterns 1300b1 and 1300e1 (e.g. FIG. 13A to FIG. 13F The dark band marked by the arrow in the middle Fig.13A and 13C To 13F Fig. 13B and 13E Therefore, although some deformable gratings have some disadvantages in terms of uniformity and efficiency, these disadvantages can be mitigated while improving transmission and reflection, as shown in Fig.10 , 11A , 11B and 12 discussed above.

[0092] In some embodiments, a deformed grating (e.g. Fig. 9B eyepiece) can improve uniformity. Fig.13A and Figures 13C-13F compared to, Fig. 13B The efficiency distribution in the image has fewer high-frequency artifacts (e.g., dark bands). In some embodiments, a high-refractive index eyepiece with a deformable grating can transmit 10% more visible wavelengths of light than a high-refractive index eyepiece without a deformable grating, e.g., be more transparent. Fig. 9B The deformed grating can improve uniformity while also improving transmission and back reflection characteristics.

[0093] In some implementations, using a deformed grating can improve virtual image quality.

[0094] Figure 13G and 13H Depicted are virtual image uniformity for control and deformable grating eyepieces according to embodiments of the present disclosure, respectively. In this example, green light from a projector creates virtual images 1300g and 1300h. Virtual image 1300h is generally brighter and more uniform than virtual image 1300g, indicating that the use of deformable gratings can improve virtual image quality.

[0095] 2.2 Example of manufacturing process of combined deformable grating

[0096] Templates for eyepieces with combined primary and secondary gratings (e.g., deformed gratings) can be fabricated using imprint lithography techniques such as jet and flash imprint lithography (J-FIL). These templates can then be used to further replicate the deformed surface relief gratings onto high refractive index waveguide substrates using an imprint lithography process.

[0097] Figures 14A to 14FA schematic diagram depicting an example of a fabrication process for a deformable grating according to an embodiment of the present disclosure is depicted. As a first example, the nanoimprinted primary and secondary gratings can be used directly as an etch mask to transfer the deformable geometry into a polymer, for example, to form an imprinted patterned polymer. In some embodiments, the etching is a full, conformal, directional, or planarizing etch. In some embodiments, the polymer includes a high refractive index non-filler-based polymer having a refractive index of less than 1.8. In some embodiments, the polymer includes a high refractive index filler-based polymer having a refractive index in a range between 1.8 and 2.1.

[0098] exist Figures 14A to 14F In the manufacturing process, the first grating is patterned using photolithography and etching processes in a specific orientation using photolithography technology. The first grating can be a grating with a smaller pitch, such as Figure 6 The secondary grating 604 in Fig.14A In the embodiment, a first pattern 1404 is deposited on a template substrate 1402. Fig. 14B In the process, a first pattern 1404 is etched into the template substrate 1402 to form a template for the secondary grating. Fig. 14C In, a second pattern 1406 is deposited on the template substrate 1402. Fig.14D In the process, the second pattern 1406 is planarized and etched into the template substrate 1402. Fig.14E , the second pattern 1406 is removed from the template substrate 1402, thereby forming a template substrate for a deformed grating 1412a, for example, a grating having features from a primary grating and a secondary grating of different parameters, represented by the dashed box.

[0099] In some embodiments, the following is Fig.14F 1404. The steps in the embodiment of the present invention include creating an inverse tone 1408, e.g., a template having inverse features compared to the template substrate 1402, wherein the deformed grating 1412b is represented by the dashed box. Creating the inverse tone can be performed using nanoimprint lithography. In some embodiments, the inverse tone 1408, a copy of the final template substrate 1402, or both can be patterned into a material with a high refractive index, such as high refractive index glass, lithium niobate, titanium oxide, and silicon nitride. Using a substrate with a high refractive index can result in an extended FOV because the refractive index of the substrate determines the range of allowed wave vectors.

[0100] The etch stop (e.g., the depth at which the etch ends) may determine the resist layer thickness (RLT) 1410. In some embodiments, having a thinner RLT 1410 (e.g., less than 50 nm) may be beneficial. For example, if the RLT 1410 is thin enough (e.g., less than 20 nm), it may be easier to transfer the pattern of the template substrate 1402 into a high refractive index material because the area of ​​the thin RLT does not need to be completely etched. This allows for a refractive index mismatch between the template substrate and the material forming the deformed grating, but retains the advantages of the deformed grating shape. In some embodiments, such as Fig.14D As shown, RLT 1410 is an interconnect RLT, for example, connecting adjacent ridges 1401a and 1401b of the deformed grating. In some embodiments, the etch stop is selected so that the entire vertical portion of the first pattern, the second pattern, or both is removed, such as Fig.14D As shown, the second pattern 1406 has a discontinuous portion.

[0101] In some embodiments, the first pattern 1404 (e.g., primary grating) and the second pattern 1406 (e.g., secondary grating) can have different pitches, such as different duty cycles, line width grading, or both. For example, the first pattern 1404 can have a pitch P1 and a first line width LW1, and the second pattern 1406 can have a second pitch P2 and a second line width LW2. In this example, the first line width LW1 is smaller than the second line width LW2, and the first pitch P1 is smaller than the second pitch P2, but other variations are possible.

[0102] Figures 15A to 15F A schematic diagram of an example of a fabrication process for fabricating a deformed grating using an intermediate masking layer according to an embodiment of the present disclosure is shown. As another example, nanoimprinted primary and secondary gratings can be used with an intermediate masking layer to transfer deformed geometries. Fig.15A , a first pattern 1502 for a secondary grating is imprinted on an intermediate masking layer 1504 on top of a substrate 1506. In some embodiments, the intermediate masking layer 1504 includes chromium. In some embodiments, the substrate 1506 includes silicon dioxide on silicon, such as thermally oxidized silicon or fused quartz.

[0103] exist Fig. 15B In the process, a secondary grating (e.g., a grating with a smaller pitch) is imprinted into the intermediate masking layer 1504. Then, in Fig. 15C In FIG. 1 , a second pattern 1508 for the primary grating is imprinted on top of the intermediate masking layer 1504 and the remaining portion of the substrate 1506 .

[0104] Fig.15D Etching of a primary grating using a second pattern 1508 is depicted. Fig.15EThe substrate is depicted after removing remaining portions of the second pattern 1508 and remaining portions of the intermediate masking layer 1504 , thereby forming a final template 1510 . Fig.15E A cross-sectional view of the final template 1510 is depicted, and Fig.15F A plan view of the final template 1510 is depicted.

[0105] In some embodiments, the remaining intermediate layer may remain and determine the height of additional gratings (e.g., recyclers) in the final imprint. Fig.15A -Electron beam lithography is used in F. In some of these embodiments, a combination of imprint lithography and etching produces sharply defined corners and edges of two-dimensionally patterned holes and pillars.

[0106] Processes such as J-FIL inkjet lithography can produce templates with analog or partitioned graded levels and with different graded axes. In some embodiments, for example when using a J-FIL process with graded residual layer thickness (RLT) using inkjet dispensing, the first raster lithography etch step, the second raster lithography etch step (e.g., Figures 16A-16F as shown), or two steps (as shown Figures 17A-17F The composition transfer hierarchical design is shown in FIG.

[0107] Figures 16A-16F A schematic diagram depicting an example of a process for manufacturing a deformable grating having a grading primary grading according to an embodiment of the present disclosure is depicted. Figures 16A-16F Steps and Figures 14A-14F The steps are similar to those of , except that the primary grating (e.g., second pattern 1606) is graded rather than having a constant height like the second pattern 1406.

[0108] Figures 17A-17F A schematic diagram depicting an example of a manufacturing process for a deformed grating according to an embodiment of the present disclosure, wherein both the primary and secondary gratings are graded. Figures 17A-17F Steps and Figures 14A-14F The steps are similar to those of , except that the primary grating (e.g., second pattern 1706) and the secondary grating (e.g., first pattern 1704) are graded rather than having a constant height like the first pattern 1404 and the second pattern 1406.

[0109] This fabrication process can also accommodate deformed blazed geometries other than binary gratings, such as tilted, sawtooth, blaze sawtooth, multi-step, metastructures, cylinders, tilted cylinders, holes, tilted holes, trapezoidal cubes, cubes, cuboids, and other shapes.

[0110] Figures 18A-18FA schematic diagram illustrating an example of a manufacturing process of a deformed grating according to an embodiment of the present disclosure, where the primary grating is a sawtooth grating. Figures 18A-18F The steps of Figures 14A-14F are similar to those of

[0111] except that the primary grating (e.g., the second pattern 1806) has a sawtooth shape instead of a binary shape like the second pattern 1406. Using a sawtooth-shaped primary grating can increase the user-world light extraction rate by coupling more light out to the user while maintaining a high transmittance. Figures 14A-18F All the manufacturing processes described with reference to

[0112] can be performed on both sides of the substrate (e.g., the world side and the user side). Figures 14A-18F In some embodiments, the grating formed by the manufacturing process described with reference to Fig.14D can be conformally or directionally coated with one or more layers of low refractive index or high refractive index (1.45 < n < 2.7) materials. For example, etching can create trench openings in the deformed grating, e.g., above the position marked RLT 1410 in

[0113] 3.0 Case 3: Stacked Gratings with Multiple Refractive Indices

[0114] and between adjacent ridges 1401a and 1401b. In some embodiments, the grating is coated with a material having a refractive index in the range of 1.15 to 2.1, such as an organic sol-gel material or a flowable Si3N4, to at least partially fill the trench openings. In some embodiments, the maximum thickness of the coating layer can be between 500 nanometers and 10 micrometers. In some embodiments, the coating layer at least partially covers the CPE, OPE, EPE, or a combination thereof on one or both sides of the substrate.

[0115] Fig.19A Depicts an example of an eyepiece including a secondary grating 1902 according to an embodiment of the present disclosure. The secondary grating 1902 can include 1D or 2D CPE / OPE / EPE features embedded in a lower refractive index coating film 1904 on both sides of the substrate 1901. The first side of the eyepiece 1900a is the ICG 1906, while the AR grating 1908 is located on the other side of the eyepiece 1900a.

[0116] Fig.19B Depicted is the eyepiece 1900b after stacking a primary grating 1910 above a secondary grating 1902, in accordance with an embodiment of the present disclosure. Since the primary grating 1910 faces the air and the material refractive index is lower than that of the embedded secondary grating 1902, the refractive index modulation (e.g., the refractive index change between the eyepiece 1900b and the air) still exists. Stacking waveguides of different refractive indices can allow for a more gradual change in refractive index. For example, light from the air can be incident on a first grating having a refractive index closer to 1 (reducing the difference in refractive index and thus reducing back reflections), and then the light can travel from the first grating to a second grating having a large refractive index, allowing for a large FOV. In some embodiments, the primary grating 1910 is coated with a lower refractive index material, such as MgF2 (n=1.38) or SiO2 (n=1.45), which can further improve transmission and reduce back reflections.

[0117] In some embodiments, Fig.19A As shown, a first side of the eyepiece 1900b is close to the user, such as the side with the ICG 1906, and a second side of the eyepiece 1900b, such as the side with the AR grating 1908 away from the user, is such as the "world side". In some embodiments, the first side of the eyepiece 1900b is away from the user, such as the side with the ICG 1906, and the second side of the eyepiece 1900b, such as the side with the AR grating 1908 close to the user, is close to the user. Thus, the primary grating 1910 and the secondary grating 1902 can each be proximal, distal, or both relative to the user (when the primary grating and the secondary grating are located on opposite sides of the substrate).

[0118] Fig. 20A An example of a stacked grating 2000a according to an embodiment of the present disclosure is depicted. The stacked grating 2000a includes a substrate 2002, a primary grating 2004 (e.g., a CPE grating), and a secondary grating 2006 (e.g., an AR grating). The substrate 2002 may have a high refractive index (e.g., glass with n=2), the primary grating 2004 may have a first refractive index (e.g., n1=1.65), and the secondary grating 2006 may have a second refractive index n2.

[0119] Fig. 20B Depicted is a graph 2000b showing the transmission profile of the stacked grating 2000a versus wavelength for five versions of the second refractive index in accordance with an embodiment of the present disclosure. Fig. 20B The light in is vertically incident light and is s-polarized light. "D79" refers to the case where there is no secondary grating 2006, for example, when the primary grating 2004 and the secondary grating 2006 are made of the same material and therefore have the same refractive index, for example n1 = n2 = 1.65. Fig. 20B Distributions for n2 = 2.4, 2.1, 1.8, and 1.4 (eg, n2 is greater and less than n1) are shown.

[0120] Fig. 20B The distributions show that the transmittance of a stacked grating (e.g., a primary grating stacked on a secondary grating with a different refractive index) can be close to the transmittance of a non-stacked surface relief grating (e.g., D79) for wavelengths below about 0.6 microns, and can be greater than the transmittance of a non-stacked surface relief grating for wavelengths above about 0.6 microns. In some embodiments, a secondary grating with a different refractive index than a primary grating can reduce rainbow artifacts when embedded in a primary grating.

[0121] As described herein, primary and secondary gratings have various geometries for increasing transmittance and reducing back reflections without sacrificing the quality of the display of digital content.

[0122] Although the application has been defined in the appended claims, it should be understood that the invention may also (additionally or alternatively) be defined according to the following examples:

[0123] Example 1: An eyepiece, comprising:

[0124] substrate;

[0125] an in-coupling grating located on a first side of the substrate; and

[0126] A deformed grating is located on at least the first side of the substrate and includes characteristics of a primary grating and a secondary grating.

[0127] Example 2: An eyepiece according to Example 1, wherein the primary grating has two or more layers, the two or more layers have two or more associated grating pitches and orientations, the two or more associated grating pitches and orientations determine two or more wave vectors and momentum space, the secondary grating has a grating pitch and orientation that determine the wave vector and momentum space, and the wave vector of the secondary grating is a linear combination of the two or more wave vectors of the primary grating.

[0128] Example 3: An eyepiece according to Example 1 or 2, wherein the pitch of the secondary grating is smaller than any pitch of the primary grating by a factor of at least twice the refractive index of the substrate.

[0129] Example 4: An eyepiece according to any of the preceding examples, wherein the pitch of the primary grating is different from the pitch of the secondary grating.

[0130] Example 5: An eyepiece according to any of the preceding examples, wherein the orientation of the primary grating is different from the orientation of the secondary grating.

[0131] Example 6: An eyepiece according to any of the preceding examples, wherein the shape of the primary grating is different from the shape of the secondary grating, and the shape of the primary grating and the shape of the secondary grating include portions having at least one shape from the group consisting of: binary, tilted, blazed sawtooth, multi-step structure, element structure, cylinder, hole, tilted hole, tilted cylinder, trapezoidal cube, cube, and cuboid.

[0132] Example 7: An eyepiece according to any of the preceding examples, wherein at least one of the primary grating and the secondary grating has a graded height profile.

[0133] Example 8: An eyepiece according to any of the preceding examples, wherein the refractive index of the primary grating is different from the refractive index of the secondary grating.

[0134] Example 9: An eyepiece according to any of the preceding examples, wherein the primary grating is at least partially located on one of: an exit pupil expander, an orthogonal pupil expander, and a combined pupil expander.

[0135] Example 10: An eyepiece according to any of the preceding examples, wherein the secondary grating is a recycler or an anti-reflection grating.

[0136] Example 11: An eyepiece according to any of the preceding examples, wherein at least one of the primary grating and the secondary grating is one-dimensional.

[0137] Example 12: An eyepiece according to any of the preceding examples, wherein at least one of the primary grating and the secondary grating is two-dimensional.

[0138] Example 13: An eyepiece according to any of the preceding examples, wherein the pitch of the secondary grating is different from the pitch of the primary grating.

[0139] Example 14: The eyepiece of Example 13, wherein the pitch of the secondary grating is smaller than the pitch of the primary grating.

[0140] Example 15: An eyepiece according to any of the preceding examples, wherein the line width of the secondary grating is different from the line width of the primary grating.

[0141] Example 16: An eyepiece according to any of the preceding examples, wherein the refractive index of the substrate is in the range of 1.5 to 2.7.

[0142] Example 17: An eyepiece according to any of the preceding examples, wherein the primary grating includes a portion located on a second side of the substrate opposite to the first side of the substrate.

[0143] Example 18: An eyepiece according to any of the preceding examples, wherein the first side of the substrate is close to a user and the second side of the substrate is away from the user.

[0144] Example 19: An eyepiece according to any of the preceding examples, wherein the first side of the substrate is away from a user and the second side of the substrate is close to the user.

[0145] Example 20: The eyepiece of any of the preceding examples further comprising an anti-reflection grating on a second side of the substrate opposite to the first side of the substrate.

[0146] Example 21: An eyepiece according to any of the preceding examples, wherein at least one of the primary grating and the secondary grating is etched into the substrate.

[0147] Example 22: An eyepiece according to any of the preceding examples, wherein at least one of the primary grating and the secondary grating is etched into a coating on the substrate.

[0148] Example 23: The eyepiece of Example 22, wherein the coating is partially located on at least one of the primary grating and the secondary grating.

[0149] Example 24: An eyepiece according to Example 23, wherein the refractive index of the coating is in the range of 1.45 to 2.7.

[0150] Example 25: An eyepiece according to Example 23 or Example 24, wherein the coating includes at least one of SiO2, Si3N4, ZrO2, TiO2 or SiC.

[0151] Example 26: An eyepiece according to any of Examples 23-25, wherein the coating at least partially fills the groove openings in at least one of the primary grating and the secondary grating.

[0152] Example 27: An eyepiece according to Example 23, wherein the refractive index of the coating is in the range of 1.15 to 2.1.

[0153] Example 28: An eyepiece according to Example 26 or Example 27, wherein the maximum thickness of the coating is in the range of 500 nanometers to 10 microns.

[0154] Example 29: An eyepiece according to any one of Examples 26-28, wherein at least one of the primary grating and the secondary grating includes a discontinuous portion.

[0155] Example 30: The eyepiece of any of Examples 26-29, wherein the etching of at least one of the primary grating and the secondary grating is at least one of partial, full, conformal, directional, or planarized

[0156] Example 31: An eyepiece according to any one of Examples 26-30, wherein the etching of at least one of the primary grating and the secondary grating is located on a side of the substrate close to the user, on a side of the substrate away from the user, or on both.

[0157] Example 32: The eyepiece of any of the preceding examples, wherein at least one of the primary grating and the secondary grating is imprinted onto the substrate using nanoimprint lithography.

[0158] Example 33: The eyepiece of Example 32, wherein the eyepiece comprises a resist layer having a thickness of less than 50 nanometers.

[0159] Example 34: An eyepiece according to Example 32 or Example 33, wherein at least one of the primary grating and the secondary grating comprises an imprinted polymer, and the imprinted polymer comprises a non-filler-based polymer having a refractive index less than 1.8.

[0160] Example 35: An eyepiece according to Example 32 or Example 33, wherein at least one of the primary grating and the secondary grating comprises an imprinted polymer, and the imprinted polymer comprises a filler-based polymer having a refractive index in the range of 1.8 to 2.1.

[0161] Example 36: An eyepiece comprising:

[0162] substrate;

[0163] an in-coupling grating located on a first side of the substrate; and

[0164] A stacked grating includes a primary grating having a first refractive index and a secondary grating having a second refractive index, wherein the secondary grating is embedded in the primary grating, and the first refractive index is different from the second refractive index.

[0165] Example 37: An eyepiece according to Example 36, wherein the second refractive index is greater than the first refractive index.

[0166] Example 38: An eyepiece according to Example 36, wherein the second refractive index is less than the first refractive index.

[0167] Example 39: An eyepiece according to any one of Examples 36-38, wherein the pitch of the primary grating is different from the pitch of the secondary grating.

[0168] Example 40: An eyepiece according to any of Examples 36-39, wherein the orientation of the primary grating is different from the orientation of the secondary grating.

[0169] Example 41: An eyepiece according to any one of Examples 36-40, wherein the shape of the primary grating is different from the shape of the secondary grating, and the shape of the primary grating and the shape of the secondary grating include a portion having at least one shape from the group consisting of: binary, tilted, blazed sawtooth, multi-step structure, element structure, cylinder, hole, tilted hole, tilted cylinder, trapezoidal cube, cube, and rectangular parallelepiped.

[0170] Example 42: An eyepiece according to any of Examples 36-41, wherein at least one of the primary grating and the secondary grating has a graded height profile.

[0171] Example 43: An eyepiece according to any of Examples 36-42, wherein the primary grating is at least partially located on one of: an exit pupil expander, an orthogonal pupil expander, and a combined pupil expander.

[0172] Example 44: An eyepiece according to any one of Examples 36-43, wherein the secondary grating is a recycler or an anti-reflection grating.

[0173] Example 45: An eyepiece according to any of Examples 36-44, wherein at least one of the primary grating and the secondary grating is one-dimensional.

[0174] Example 46: An eyepiece according to any of Examples 36-45, wherein at least one of the primary grating and the secondary grating is two-dimensional.

[0175] Example 47: An eyepiece according to any of Examples 36-46, wherein the pitch of the secondary grating is different from the pitch of the primary grating.

[0176] Example 48: An eyepiece according to Example 47, wherein the pitch of the secondary grating is smaller than the pitch of the primary grating.

[0177] Example 49: An eyepiece according to any one of Examples 36-48, wherein the line width of the secondary grating is different from the line width of the primary grating.

[0178] Example 50: An eyepiece according to any one of Examples 36-49, wherein the refractive index of the substrate is in the range of 1.5 to 2.7.

[0179] Example 51: An eyepiece according to any of Examples 36-50, wherein the primary grating includes a portion located on a second side of the substrate opposite to the first side of the substrate.

[0180] Example 52: An eyepiece according to Example 51, wherein the first side of the substrate is close to a user and the second side of the substrate is away from the user.

[0181] Example 53: An eyepiece according to Example 51, wherein the first side of the substrate is away from a user and the second side of the substrate is close to the user.

[0182] Example 54: The eyepiece of any one of Examples 36-53, further comprising an anti-reflection grating located on a second side of the substrate opposite to the first side of the substrate.

[0183] Example 55: An eyepiece according to any of Examples 36-54, wherein at least one of the primary grating and the secondary grating is etched into the substrate.

[0184] Example 56: An eyepiece according to any of Examples 36-55, wherein at least one of the primary grating and the secondary grating is etched into a coating on the substrate.

[0185] Example 57: The eyepiece of Example 56, wherein the coating of at least one of the primary grating and the secondary grating is partial.

[0186] Example 58: An eyepiece according to Example 57, wherein the refractive index of the coating is in the range of 1.45 to 2.7.

[0187] Example 59: An eyepiece according to Example 57 or Example 58, wherein the coating includes at least one of SiO2, Si3N4, ZrO2, TiO2 or SiC.

[0188] Example 60: An eyepiece according to any of Examples 57-59, wherein the coating at least partially fills the groove openings in at least one of the primary grating and the secondary grating.

[0189] Example 61: An eyepiece according to Example 60, wherein the refractive index of the coating is in the range of 1.15 to 2.1.

[0190] Example 62: An eyepiece according to Example 60 or Example 61, wherein the maximum thickness of the coating is in the range of 500 nanometers to 10 microns.

[0191] Example 63: An eyepiece according to any of Examples 60-62, wherein at least one of the primary grating and the secondary grating includes a discontinuous portion.

[0192] Example 64: An eyepiece according to any of Examples 60-63, wherein the etching of at least one of the primary grating and the secondary grating is at least one of partial, full, conformal, directional, or planarized.

[0193] Example 65: An eyepiece according to any one of Examples 60-64, wherein the etching of at least one of the primary grating and the secondary grating is located on a side of the substrate close to the user, on a side of the substrate away from the user, or on both.

[0194] Example 66: An eyepiece according to any one of Examples 36-65, wherein at least one of the primary grating and the secondary grating is imprinted on the substrate using nanoimprint lithography technology.

[0195] Example 67: The eyepiece of Example 66, wherein the eyepiece comprises a resist layer having a thickness of less than 50 nanometers.

[0196] Example 68: An eyepiece according to Example 66 or Example 67, wherein at least one of the primary grating and the secondary grating comprises an imprinted polymer, and the imprinted polymer comprises a non-filler-based polymer having a refractive index less than 1.8.

[0197] Example 69: An eyepiece according to any of Examples 66-69, wherein at least one of the primary grating and the secondary grating comprises an imprinted polymer, and the imprinted polymer comprises a filler-based polymer having a refractive index in the range of 1.8 to 2.1.

[0198] Example 70: An eyepiece comprising:

[0199] substrate;

[0200] an in-coupling grating located on a first side of the substrate;

[0201] a primary grating located on the first side of the substrate; and

[0202] A secondary grating is located on the second side of the substrate opposite to the first side of the substrate, wherein a pitch of the secondary grating is smaller than a pitch of the primary grating.

[0203] Example 71: An eyepiece according to Example 70, wherein the orientation of the primary grating is different from the orientation of the secondary grating.

[0204] Example 72: An eyepiece according to Example 70 or Example 71, wherein the shape of the primary grating is different from the shape of the secondary grating, and the shape of the primary grating and the shape of the secondary grating include a portion having at least one shape from the group consisting of: binary, tilted, blazed sawtooth, multi-step structure, element structure, cylinder, hole, tilted hole, tilted cylinder, trapezoidal cube, cube, and cuboid.

[0205] Example 73: An eyepiece according to any of Examples 70-72, wherein at least one of the primary grating and the secondary grating has a graded height profile.

[0206] Example 74: An eyepiece according to any of Examples 70-73, wherein the refractive index of the primary grating is different from the refractive index of the secondary grating.

[0207] Example 75: An eyepiece according to any of Examples 70-74, wherein the primary grating is at least partially located on one of: an exit pupil expander, an orthogonal pupil expander, and a combined pupil expander.

[0208] Example 76: An eyepiece according to any one of Examples 70-75, wherein the secondary grating is a recycler or an anti-reflection grating.

[0209] Example 77: An eyepiece according to any of Examples 70-76, wherein at least one of the primary grating and the secondary grating is one-dimensional.

[0210] Example 78: An eyepiece according to any of Examples 70-77, wherein at least one of the primary grating and the secondary grating is two-dimensional.

[0211] Example 79: An eyepiece according to any one of Examples 70-78, wherein the line width of the secondary grating is different from the line width of the primary grating.

[0212] Example 80: An eyepiece according to any one of Examples 70-79, wherein the refractive index of the substrate is in the range of 1.5 to 2.7.

[0213] Example 81: An eyepiece according to any of Examples 70-80, wherein the primary grating includes a portion located on a second side of the substrate opposite to the first side of the substrate.

[0214] Example 82: An eyepiece according to Example 81, wherein the first side of the substrate is close to a user and the second side of the substrate is away from the user.

[0215] Example 83: An eyepiece according to Example 81, wherein the first side of the substrate is away from a user and the second side of the substrate is close to the user.

[0216] Example 84: The eyepiece of any one of Examples 70-83, further comprising an anti-reflection grating located on a second side of the substrate opposite to the first side of the substrate.

[0217] Example 85: An eyepiece according to any of Examples 70-84, wherein at least one of the primary grating and the secondary grating is etched into the substrate.

[0218] Example 86: An eyepiece according to any of Examples 70-85, wherein at least one of the primary grating and the secondary grating is etched into a coating on the substrate.

[0219] Example 87: An eyepiece according to Example 86, wherein the coating of at least one of the primary grating and the secondary grating is partial.

[0220] Example 88: An eyepiece according to Example 87, wherein the refractive index of the coating is in the range of 1.45 to 2.7.

[0221] Example 89: An eyepiece according to Example 87 or Example 88, wherein the coating includes at least one of SiO2, Si3N4, ZrO2, TiO2 or SiC.

[0222] Example 90: An eyepiece according to any of Examples 87-89, wherein the coating at least partially fills the groove openings in at least one of the primary grating and the secondary grating.

[0223] Example 91: An eyepiece according to any of Examples 87-90, wherein the refractive index of the coating is in the range of 1.15 to 2.1.

[0224] Example 92: An eyepiece according to any of Examples 87-91, wherein the maximum thickness of the coating is in the range of 500 nanometers to 10 microns.

[0225] Example 93: An eyepiece according to any of Examples 87-92, wherein at least one of the primary grating and the secondary grating includes a discontinuous portion.

[0226] Example 94: An eyepiece according to any of Examples 87-93, wherein the etching of at least one of the primary grating and the secondary grating is at least one of partial, full, conformal, directional, or planarized.

[0227] Example 95: An eyepiece according to any one of Examples 70-94, wherein the etching of at least one of the primary grating and the secondary grating is located on a side of the substrate close to the user, on a side of the substrate away from the user, or on both.

[0228] Example 96: An eyepiece according to any one of Examples 70-95, wherein at least one of the primary grating and the secondary grating is imprinted on the substrate using nanoimprint lithography technology.

[0229] Example 97: The eyepiece of any of Examples 70-96, wherein the eyepiece comprises a resist layer having a thickness of less than 50 nanometers.

[0230] Example 98: An eyepiece according to any of Examples 70-97, wherein at least one of the primary grating and the secondary grating comprises an embossed polymer, and the embossed polymer comprises a non-filler-based polymer having a refractive index less than 1.8.

[0231] Example 99: An eyepiece according to any of Examples 70-98, wherein at least one of the primary grating and the secondary grating comprises an imprinted polymer, and the imprinted polymer comprises a filler-based polymer having a refractive index in the range of 1.8 to 2.1.

[0232] Although the present disclosure contains many specific implementation details, these details should not be interpreted as limitations on any implementation of the present disclosure or the scope of what may be claimed, but rather as descriptions of specific features of the example implementations. Certain features described in this specification in the context of separate implementations may also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation may also be implemented individually or in any suitable sub-combination in multiple implementations. In addition, although features may be described as working in certain combinations and even initially claimed, in some cases, one or more features from the claimed combination may be deleted from the combination, and the claimed combination may be directed to a sub-combination or a variation of the sub-combination.

[0233] Similarly, although the operations are described in a particular order in the figure, this does not mean that these operations must be performed in the particular order or sequence shown, or that all the operations shown must be performed to achieve the desired results. In addition, the process described in the figure does not necessarily require the specific order or sequence shown to be performed to achieve the desired results.

[0234] Although various embodiments of the present invention are described herein, it should be understood that they are described only as examples. Those skilled in the art may think of many variations and modifications after reading this specification. The breadth and scope of the present invention are not limited by the examples described herein, and can be broadly interpreted to include such variations and modifications.

Claims

1. An eyepiece, comprising: substrate; an in-coupling grating located on a first side of the substrate; as well as A deformed grating is located on at least the first side of the substrate and includes characteristics of a primary grating and a secondary grating.

2. The eyepiece according to claim 1, wherein: The primary grating has two or more layers, the two or more layers have two or more associated grating pitches and orientations, the two or more associated grating pitches and orientations determine two or more wave vectors and momentum space, the secondary grating has a grating pitch and orientation that determine the wave vector and momentum space, the wave vector of the secondary grating is a linear combination of the two or more wave vectors of the primary grating.

3. The eyepiece according to claim 1, wherein: The secondary grating has a pitch that is smaller than any pitch of the primary grating by a factor of at least twice the refractive index of the substrate.

4. The eyepiece according to claim 1, wherein: The grating pitch of the primary grating is different from the grating pitch of the secondary grating.

5. The eyepiece according to claim 1, wherein: The orientation of the primary grating is different from the orientation of the secondary grating.

6. The eyepiece according to claim 1, wherein: The shape of the primary grating is different from the shape of the secondary grating, and the shape of the primary grating and the shape of the secondary grating include a portion having at least one shape of the group consisting of: binary, tilted, blazed sawtooth, multi-step structure, element structure, cylinder, hole, tilted hole, tilted cylinder, trapezoidal cube, cube, and cuboid.

7. The eyepiece according to claim 1, wherein: At least one of the primary grating and the secondary grating has a graded height profile.

8. The eyepiece according to claim 1, wherein: The refractive index of the primary grating is different from the refractive index of the secondary grating.

9. The eyepiece of claim 1, wherein: The primary grating is at least partially located on one of: an exit pupil expander, an orthogonal pupil expander, and a combined pupil expander.

10. The eyepiece of claim 1, wherein: The secondary grating is a recycler or an anti-reflection grating.

11. The eyepiece of claim 1, wherein: At least one of the primary grating and the secondary grating is one-dimensional.

12. The eyepiece of claim 1, wherein: At least one of the primary grating and the secondary grating is two-dimensional.

13. The eyepiece of claim 1, wherein: The grating pitch of the secondary grating is different from the grating pitch of the primary grating.

14. The eyepiece according to claim 13, wherein: The grating pitch of the secondary grating is smaller than the grating pitch of the primary grating.

15. The eyepiece of claim 1, wherein: The line width of the secondary grating is different from the line width of the primary grating.

16. The eyepiece of claim 1, wherein: The refractive index of the substrate is in the range of 1.5 to 2.

7.

17. The eyepiece of claim 1, wherein: The primary grating includes a portion located on a second side of the substrate opposite to the first side of the substrate.

18. The eyepiece of claim 17, wherein: The first side of the substrate is close to a user, and the second side of the substrate is far from the user.

19. The eyepiece of claim 17, wherein: The first side of the substrate is away from a user, and the second side of the substrate is close to the user.

20. The eyepiece of claim 1, further comprising an anti-reflection grating located on a second side of the substrate opposite the first side of the substrate.

21. The eyepiece of claim 1, wherein: At least one of the primary grating and the secondary grating is etched into the substrate.

22. The eyepiece of claim 1, wherein: At least one of the primary grating and the secondary grating is etched into a coating on the substrate.

23. The eyepiece of claim 22, wherein: The coating is partially located on at least one of the primary grating and the secondary grating.

24. The eyepiece of claim 23, wherein: The refractive index of the coating is in the range of 1.45 to 2.

7.

25. The eyepiece of claim 23, wherein: The coating includes at least one of SiO2, Si3N4, ZrO2, TiO2 or SiC.

26. The eyepiece of claim 23, wherein: The coating at least partially fills the groove openings in at least one of the primary grating and the secondary grating.

27. The eyepiece of claim 26, wherein: The refractive index of the coating is in the range of 1.15 to 2.

1.

28. The eyepiece of claim 26, wherein: The maximum thickness of the coating is in the range of 500 nanometers to 10 micrometers.

29. The eyepiece of claim 26, wherein: At least one of the primary grating and the secondary grating includes a discontinuity.

30. The eyepiece of claim 26, wherein: The etching of at least one of the primary grating and the secondary grating is at least one of partial, full, conformal, directional, or planar.

31. The eyepiece of claim 26, wherein: The etching of at least one of the primary grating and the secondary grating is located on a side of the substrate close to the user, on a side of the substrate away from the user, or on both.

32. The eyepiece of claim 1, wherein: At least one of the primary grating and the secondary grating is imprinted over the substrate using nanoimprint lithography.

33. The eyepiece of claim 32, wherein: The eyepiece includes a resist layer having a thickness of less than 50 nanometers.

34. The eyepiece of claim 32, wherein: At least one of the primary grating and the secondary grating comprises an imprinted polymer comprising a non-filler based polymer having a refractive index less than 1.

8.

35. The eyepiece of claim 32, wherein: At least one of the primary grating and the secondary grating comprises an imprinted polymer comprising a filler-based polymer having a refractive index in the range of 1.8 to 2.

1.

36. An eyepiece comprising: substrate; an in-coupling grating located on a first side of the substrate; as well as A stacked grating includes a primary grating having a first refractive index and a secondary grating having a second refractive index, wherein the secondary grating is embedded in the primary grating, and the first refractive index is different from the second refractive index.

37. The eyepiece of claim 36, wherein: The second refractive index is greater than the first refractive index.

38. The eyepiece of claim 36, wherein: The second refractive index is lower than the first refractive index.

39. The eyepiece of claim 36, wherein: The grating pitch of the primary grating is different from the grating pitch of the secondary grating.

40. The eyepiece of claim 36, wherein: The orientation of the primary grating is different from the orientation of the secondary grating.

41. The eyepiece of claim 36, wherein: The shape of the primary grating is different from the shape of the secondary grating, and the shape of the primary grating and the shape of the secondary grating include a portion having at least one shape of the group consisting of: binary, tilted, blazed sawtooth, multi-step structure, element structure, cylinder, hole, tilted hole, tilted cylinder, trapezoidal cube, cube, and cuboid.

42. The eyepiece of claim 36, wherein: At least one of the primary grating and the secondary grating has a graded height profile.

43. The eyepiece of claim 36, wherein: The primary grating is at least partially located on one of: an exit pupil expander, an orthogonal pupil expander, and a combined pupil expander.

44. The eyepiece of claim 36, wherein: The secondary grating is a recycler or an anti-reflection grating.

45. The eyepiece of claim 36, wherein: At least one of the primary grating and the secondary grating is one-dimensional.

46. ​​The eyepiece of claim 36, wherein: At least one of the primary grating and the secondary grating is two-dimensional.

47. The eyepiece of claim 36, wherein: The grating pitch of the secondary grating is different from the grating pitch of the primary grating.

48. The eyepiece of claim 47, wherein: The grating pitch of the secondary grating is smaller than the grating pitch of the primary grating.

49. The eyepiece of claim 36, wherein: The line width of the secondary grating is different from the line width of the primary grating.

50. The eyepiece of claim 36, wherein: The refractive index of the substrate is in the range of 1.5 to 2.

7.

51. The eyepiece of claim 36, wherein: The primary grating includes a portion located on a second side of the substrate opposite to the first side of the substrate.

52. The eyepiece of claim 51, wherein: The first side of the substrate is close to a user, and the second side of the substrate is far from the user.

53. The eyepiece of claim 51, wherein: The first side of the substrate is away from a user, and the second side of the substrate is close to the user.

54. The eyepiece of claim 36, further comprising an anti-reflection grating on a second side of the substrate opposite the first side of the substrate.

55. The eyepiece of claim 36, wherein: At least one of the primary grating and the secondary grating is etched into the substrate.

56. The eyepiece of claim 36, wherein: At least one of the primary grating and the secondary grating is etched into a coating on the substrate.

57. The eyepiece of claim 56, wherein: The coating of at least one of the primary grating and the secondary grating is partial.

58. The eyepiece of claim 57, wherein: The refractive index of the coating is in the range of 1.45 to 2.

7.

59. The eyepiece of claim 57, wherein: The coating includes at least one of SiO2, Si3N4, ZrO2, TiO2 or SiC.

60. The eyepiece of claim 57, wherein: The coating at least partially fills the groove openings in at least one of the primary grating and the secondary grating.

61. The eyepiece of claim 60, wherein: The refractive index of the coating is in the range of 1.15 to 2.

1.

62. The eyepiece of claim 60, wherein: The maximum thickness of the coating is in the range of 500 nanometers to 10 micrometers.

63. The eyepiece of claim 60, wherein: At least one of the primary grating and the secondary grating includes a discontinuity.

64. The eyepiece of claim 60, wherein: The etching of at least one of the primary grating and the secondary grating is at least one of partial, full, conformal, directional, or planar.

65. The eyepiece of claim 60, wherein: The etching of at least one of the primary grating and the secondary grating is located on a side of the substrate close to the user, on a side of the substrate away from the user, or on both.

66. The eyepiece of claim 36, wherein: At least one of the primary grating and the secondary grating is imprinted over the substrate using nanoimprint lithography.

67. The eyepiece of claim 66, wherein: The eyepiece includes a resist layer having a thickness of less than 50 nanometers.

68. The eyepiece of claim 66, wherein: At least one of the primary grating and the secondary grating comprises an imprinted polymer comprising a non-filler based polymer having a refractive index less than 1.

8.

69. The eyepiece of claim 66, wherein: At least one of the primary grating and the secondary grating comprises an imprinted polymer comprising a filler-based polymer having a refractive index in the range of 1.8 to 2.

1.

70. An eyepiece comprising: substrate; an in-coupling grating located on a first side of the substrate; a primary grating located on the first side of the substrate; as well as A secondary grating is located on a second side of the substrate opposite to the first side of the substrate, wherein a pitch of the secondary grating is smaller than a pitch of the primary grating.

71. The eyepiece of claim 70, wherein: The orientation of the primary grating is different from the orientation of the secondary grating.

72. The eyepiece of claim 70, wherein: The shape of the primary grating is different from the shape of the secondary grating, and the shape of the primary grating and the shape of the secondary grating include a portion having at least one shape of the group consisting of: binary, tilted, blazed sawtooth, multi-step structure, element structure, cylinder, hole, tilted hole, tilted cylinder, trapezoidal cube, cube, and cuboid.

73. The eyepiece of claim 70, wherein: At least one of the primary grating and the secondary grating has a graded height profile.

74. The eyepiece of claim 70, wherein: The refractive index of the primary grating is different from the refractive index of the secondary grating.

75. The eyepiece of claim 70, wherein: The primary grating is at least partially located on one of: an exit pupil expander, an orthogonal pupil expander, and a combined pupil expander.

76. The eyepiece of claim 70, wherein: The secondary grating is a recycler or an anti-reflection grating.

77. The eyepiece of claim 70, wherein: At least one of the primary grating and the secondary grating is one-dimensional.

78. The eyepiece of claim 70, wherein: At least one of the primary grating and the secondary grating is two-dimensional.

79. The eyepiece of claim 70, wherein: The line width of the secondary grating is different from the line width of the primary grating.

80. The eyepiece of claim 70, wherein: The refractive index of the substrate is in the range of 1.5 to 2.

7.

81. The eyepiece of claim 70, wherein: The primary grating includes a portion located on a second side of the substrate opposite to the first side of the substrate.

82. The eyepiece of claim 81, wherein: The first side of the substrate is close to a user, and the second side of the substrate is far from the user.

83. The eyepiece of claim 81, wherein: The first side of the substrate is away from a user, and the second side of the substrate is close to the user.

84. The eyepiece of claim 70, further comprising an anti-reflection grating located on a second side of the substrate opposite to the first side of the substrate.

85. The eyepiece of claim 70, wherein: At least one of the primary grating and the secondary grating is etched into the substrate.

86. The eyepiece of claim 70, wherein: At least one of the primary grating and the secondary grating is etched into a coating on the substrate.

87. The eyepiece of claim 86, wherein: The coating of at least one of the primary grating and the secondary grating is partial.

88. The eyepiece of claim 87, wherein: The refractive index of the coating is in the range of 1.45 to 2.

7.

89. The eyepiece of claim 87, wherein: The coating includes at least one of SiO2, Si3N4, ZrO2, TiO2 or SiC.

90. The eyepiece of claim 87, wherein: The coating at least partially fills the groove openings in at least one of the primary grating and the secondary grating.

91. The eyepiece of claim 90, wherein: The refractive index of the coating is in the range of 1.15 to 2.

1.

92. The eyepiece of claim 90, wherein: The maximum thickness of the coating is in the range of 500 nanometers to 10 micrometers.

93. The eyepiece of claim 90, wherein: At least one of the primary grating and the secondary grating includes a discontinuity.

94. The eyepiece of claim 90, wherein: The etching of at least one of the primary grating and the secondary grating is at least one of partial, full, conformal, directional, or planar.

95. The eyepiece of claim 70, wherein: The etching of at least one of the primary grating and the secondary grating is located on a side of the substrate close to the user, on a side of the substrate away from the user, or on both.

96. The eyepiece of claim 70, wherein: At least one of the primary grating and the secondary grating is imprinted over the substrate using nanoimprint lithography.

97. The eyepiece of claim 70, wherein: The eyepiece includes a resist layer having a thickness of less than 50 nanometers.

98. The eyepiece of claim 70, wherein: At least one of the primary grating and the secondary grating comprises an imprinted polymer comprising a non-filler based polymer having a refractive index less than 1.

8.

99. The eyepiece of claim 70, wherein: At least one of the primary grating and the secondary grating comprises an imprinted polymer comprising a filler-based polymer having a refractive index in the range of 1.8 to 2.1.

Images