High-permeability eyepiece lens architecture

Abstract

The eyepiece lens includes a substrate, an input coupling grating on a first side of the substrate, and a morphed grating including characteristics of both a primary grating and a secondary grating on at least the first side of the substrate. The primary grating and the secondary grating may have different pitches, orientations, and dimensions. The present disclosure generally describes methods and systems for a high-transmission eyepiece lens architecture having additional, morphed, or stacked secondary gratings with primary gratings to improve the transmission and back-reflection characteristics of the eyepiece lens without degrading display performance.

Description

Technical Field

[0001] Priority Claim This application claims priority under 35 USC § 119(e) to U.S. Patent Application No. 63 / 359,194, filed Jul. 7, 2022, the entire contents of which are incorporated herein by reference.

[0002] Technical Field The implementations described herein generally relate to high - transmissivity eyepiece lens architectures.

Background Art

[0003] Background Waveguides used in augmented reality eyepiece lens displays have a high refractive index associated with surface relief patterns and substrates, both of which are criteria for achieving a wide field of view with good image brightness and uniformity of digital content for the display.

Summary of the Invention

Means for Solving the Problems

[0004] Summary The present disclosure generally describes methods and systems for high - transmissivity eyepiece lens architectures having additional, morphed, or laminated secondary gratings with primary gratings to improve the transmission and back - reflection characteristics of the eyepiece lens without degrading display performance. The secondary grating can have a smaller pitch than the primary grating. The primary and secondary gratings can be one - dimensional (1D) or two - dimensional (2D).

[0005] As described herein, when small - pitch, e.g., multiple 1D or 2D gratings of the grating periodicity of the grating, are laminated on top of a primary diffraction grating used for the display of digital content, the transmission - to - reflection ratio of the eyepiece lens can be increased by 5 to 10 times, e.g., the transmission coefficient increases, the back - reflection coefficient decreases, or both.

[0006] Certain implementations of the subject matter described in this specification can be implemented to achieve one or more of the following advantages. First, the stacking of selected short pitch gratings using a morphed grating and a particular combination of diffractive optical elements can help improve the see-through transmission performance and the back reflection performance without degrading the display performance. Second, in some cases, the display performance can be further improved by the gratings described in this specification.

[0007] Details of one or more implementations of the subject matter of this specification are set forth in the detailed description, the claims, and the accompanying drawings. Other features, aspects, and advantages of the subject matter will be apparent to those skilled in the art from the detailed description, the claims, and the accompanying drawings.

Brief Description of the Drawings

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DETAILED DESCRIPTION

[0036] Detailed Description The following detailed description is presented to explain a high-transmission eyepiece lens architecture and to enable one skilled in the art to make and use the subject matter disclosed in the context of one or more specific implementations. Various modifications, changes, and substitutions can be made to the disclosed implementations, which will be readily apparent to one skilled in the art, and the defined general principles can be applied to other implementations and uses without departing from the scope of the present disclosure. In some instances, one or more technical details within the skill of the art that are not necessary for an understanding of the described subject matter may be omitted so as not to obscure one or more of the described implementations. The present disclosure is not intended to be limited to the described or illustrated implementations, but rather is intended to be given the broadest scope consistent with the described principles and features.

[0037] A single waveguide having a large refractive index or a stack of multiple waveguides having a large refractive index may have insufficient through-transmittance and significant back-reflection. A low transmittance-to-reflection ratio may make such an eyepiece less desirable for use regardless of the presence or absence of virtual content.

[0038] Figures 1A - 1C are FIGS. 100a - 100c representing photographs of views taken through the first to third headsets respectively, according to one implementation of the present disclosure. The first headset view shown in FIG. 1A includes a stack of high refractive index waveguides with EPE. The second headset view shown in FIG. 1B has a hollow frame within the eyepiece and, for example, no waveguides. The third headset is similar to the first headset but has a different form factor.

[0039] FIG. 1D is FIG. 100d, a photograph of the laboratory environment used to take FIG. 1C, for example, a checkerboard-patterned room located behind the first to third headsets.

[0040] As can be seen in FIGS. 1A and 1C, high refractive index waveguides can provide an extended field of view (FOV), but using high refractive index waveguides in the eyepiece of an augmented reality headset can cause problems. First, high refractive index waveguides can reduce the transmittance of light from the "actual scene" being observed by the user. Comparing FIG. 1A and FIG. 1B, FIG. 1A appears darker because the high refractive index waveguide within the eyepiece of the first headset reduces the transmittance of light from the "real world", for example, the scene where augmented reality images are added. For example, the first headset may have a light transmittance of 60 - 65% or less.

[0041] Second, back reflections and rainbow artifacts can potentially obstruct the user's view. As can be seen in both FIGS. 1A and 1C, a rainbow flare 102 emitted from the light projection system appears in the photograph, but does not appear in FIG. 1B. Further, the checkerboard 104a in FIG. 1D behind the third headset appears as a back reflection 104b in FIG. 1C. For example, the reflection coefficient of light incident on the waveguide stack at an angle between 0° and 30° can be about 30%. Back reflections can be worse in the portion of the FOV closer to the user's temples than to the user's nose, because the acceptance angle is larger in the region closer to the temples compared to the region near the nose due to the presence of the user's face.

[0042] For example, using a sub-wavelength 1D or 2D grating having a pitch or periodicity smaller than the wavelength of the incident light can reduce the occurrence of back reflections when light encounters a high refractive index material coming from a low refractive index vacuum or air. However, adding additional, e.g., secondary gratings to reduce back reflections can potentially negatively impact the display performance of the eyepiece. The present disclosure presents an eyepiece having primary and secondary gratings configured to reduce back reflections, increase transmittance, or both, without negatively affecting an augmented reality display.

[0043] FIG. 2A shows a cross-sectional view of an eyepiece 200a according to one implementation of the present disclosure. 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 compound pupil expander (CPE).

[0044] The ICG 202 couples light from the projector into the substrate 206, and the substrate can have a high refractive index, e.g., n ≧ 2. The ICG 202 couples the light at an angle such that the in-coupled light travels by total internal reflection (TIR) within the substrate 206.

[0045] The first-order grating 204 is stepped. For example, the height of each row 208 gradually increases from a first value to a second value from right to left. The middle portion of the first-order grating is stepped, but the ends can have a constant height equal to the first and second values, respectively. In some implementations, the shape of the first-order grating 204 is a binary square ridge.

[0046] FIG. 2B shows a momentum space diagram 200b of light propagating within the eyepiece 200 of FIG. 2A according to one implementation of the present disclosure. Parameters of the eyepiece 200a, such as the refractive index of the substrate 206 and the pitch of the first-order grating, determine the allowable wave vectors of the light propagating through the substrate 206, such as k vectors. For example, the linear momentum of light corresponding to the amplitude of the phase wavefront (~e ik·r-iωt ) depends on the refractive index of the material through which it propagates. For example, the momentum is proportional to the refractive index.

[0047] As another example, the magnitude of the wave vector representing the momentum change from the grating is inversely proportional to the pitch of the grating. In FIG. 2B, the inner circle 212 represents the momentum of light for all angles of incidence, e.g., light around about 360° of the circle, for a material with n = 1, such as light traveling in air. The outer circle 214 represents the momentum of light for all physically possible angles for light traveling within a material having n = 2, such as the substrate 206.

[0048] The barrel-shaped box represents the FOV 216 when light travels through the substrate 206 and is in-coupled and out-coupled. The momentum of the light is in-coupled by the ICG 202 and changes when interacting with the first-order grating 204. For example, when in-coupled into the substrate 206, the momentum of the light rays within the FOV that were originally centered within the inner circle increases. For example, the FOV exists within the ring between the inner circle 212 and the outer circle 214, such that k x , k y is centered at (0,0). The arrow 218 represents the change in momentum proportional to k icg due to in-coupling.

[0049] When light propagates using TIR within the substrate 206, the light interacts periodically with the primary grating 204. The parameters of the primary grating 204 determine how the momentum of the light changes when the light encounters the primary grating 204. For example, the pitch and orientation can determine the magnitude and direction of the k-vector k1215 representing the change. Further, the light can propagate only in integer multiples of k1, such as higher-order and negative values.

[0050] In some implementations, the primary grating 204 has two layers, such as diffraction gratings on both sides of the substrate 206 having different periodicities and pitches. Thus, in the case of a two-layer primary grating, there is an additional k-vector, such as k2217, which is also determined by the pitch and orientation representing the change in the momentum of the in-coupled light.

[0051] In some implementations, the grating of the primary grating 204 is 2D and is formed, for example, by discrete pillars rather than continuous columns. When the grating is 2D, the additional k-vector k2217 corresponds to different changes in the momentum of the propagating light. If one side of the substrate has a 2D primary grating 204, the other side of the substrate can be patterned with an anti-reflection (AR) nanopattern or a multilayer AR film coating to reduce the reflection loss of "real-world" light to compensate for not having a primary grating on each side.

[0052] As will be discussed later, the anti-reflection nanopattern can also affect the momentum of the light propagating within the substrate. In the case of an anti-reflection (AR) coating fabricated with a short-pitch (shorter than the wavelength) diffraction grating structure, the anti-reflection characteristics can be achieved by laminating and / or morphing such a grating with the primary diffraction grating of the eyepiece. The associated grating vectors can be selected to avoid interference with the functionality of the primary diffraction grating described above.

[0053] In some implementations, a single eyepiece combines both a multi-layer primary grating and a 2D primary grating. For example, the area of the eyepiece closer to the user's temple may receive higher-intensity light over a larger angular range. Thus, the area of the eyepiece closer to the temple can have a 2D CPE on one side and a 1D diffraction structure on the other side. The remaining portion of the eyepiece, which is the area closer to the user's pupil and nose side, can have 1D diffraction structures on both sides in order to have high optical efficiency near the user's pupil.

[0054] By translating from the initial FOV within the inner circle 212 to various positions within the ring between the inner circle 212 and the outer circle 214, the outgoing light, such as the light projected onto the ICG202, spreads over a wider area for human magnification. The primary grating 204 also out-couples the light so that the increased FOV reaches the user.

[0055] The dashed arrows 219 and 221 represent the k-vectors k2 and k1 of the primary grating 204 that out-couple light to the user's pupil, enabling the user to view digital content. In some implementations, the out-coupled light propagates at an angle equal to the angle of incidence of the light from the projector incident on the ICG202.

[0056] Figures 2C and 2D show plan views 200c and 200d of the front and rear sides of the eyepiece 200a of FIG. 2A according to one implementation of the present disclosure. Arrows 220 and 222 indicate the direction of the gradient, e.g., in which direction the height of the rows of diffraction gratings on each side of the substrate changes. For example, the gradient can have 16 zones 226 of different heights. Plan view 200c shows the first side of the eyepiece 200 having a diffraction grating characterized by the k-vector k1. Plan view 200d shows the second side of the eyepiece 200a having a diffraction grating characterized by the k-vector k2. The second side of the eyepiece also includes a recycler 224, the function of which is to "recycle" the light back into the eyepiece when the light reaches a position in momentum space where it would otherwise leave the FOV after another interaction with the primary grating 204. In some implementations, the recycler 224 is a diffraction grating having a pitch and orientation determined by the parameters of the diffraction grating that makes up the primary grating 204. For example, the k-vector of the recycler k rec can be equal to the difference between k1 and k2. The pitch of the recycler 224 can be half the pitch of the primary grating. In some implementations, k icg , the sum of k1, and k2 is 0, which ensures that the light exits at the same angle as it entered the ICG202 from the projector.

[0057] 1.0 Case 1: Additional Optical Element

[0058] The first approach is to complement the primary grating with a secondary grating as follows.

[0059] Figures 3A and 3B show two examples of architectures 300 and 301 that support virtual images with a wide FoV according to one implementation of the present disclosure. Figure 3C includes a key 303 that explains which symbols represent each type of optical element within architectures 300 and 301. Key 303 includes a 1D or 2D ICG 302 represented by a right triangle, a 1D CPE / OPE / EPE 304 represented by a square ridge, a 2D CPE / OPE / EPE 306 represented by a wide ridge having a coating between each ridge, a 1D recycler 308 represented by a square ridge with a diagonal marking, and a 1D or 2D anti-reflection grating 310 represented by a narrow ridge. The features of key 303 can be, independently, 1D binary lines and spaces, or other 1D structures, or 2D structures such as holes and pillars or other 2D structures.

[0060] For example, architecture 300 is an eyepiece having a 2D CPE / OPE / EPE 306, such as a multi-layer CPE, where at least two wave vectors characterize the CPE / OPE / EPE. On the side of substrate 312 opposite the CPE / OPE / EPE 306 is an anti-reflection grating 310, which is on the opposite side of both the CPE / OPE / EPE 306 and the ICG 302. In some implementations, architecture 300 has a 1D diffraction pattern on both sides of substrate 312, such as the temple side of a transparent waveguide, such as the side having the AR grating 310, thereby maintaining less reflection compared to cases where higher reflection can be provided for world light incident angles from 0 to 60°.

[0061] As another example, architecture 301 includes a combination of 1D and 2D CPE / OPE / EPE 304 and 306. On the first side of substrate 312, there are ICG 302, 2D CPE / OPE / EPE 306, and 1D CPE / OPE / EPE 304. The second side opposite to the first side of substrate 312 includes an anti-reflection grating 310 below ICG 302 and 2D CPE / OPE / EPE 306, a 1D CPE / OPE / EPE 304 below the 1D CPE / OPE / EPE 304 on the first side, and a 1D recycler partially below a part of the 1D CPE / OPE / EPE 304 on the first side.

[0062] Figures 4A to 4D show plan views 400a to 400d of examples of an eyepiece incorporating different optical elements according to one implementation of the present disclosure. Plan views 400a and 400b are on the world side of the eyepiece, for example, the side closer to the scene viewed by the user, and plan views 400c and 400d are on the user's eye side, for example, the side closer to the user's eye.

[0063] Figures 4A and 4C respectively show the world side and the eye side of a first eyepiece "D79" having a stepped 1D CPE on the world side and a stepped 1D CPE and a recycler on the eye side. Figures 4B and 4D respectively show the world side and the eye side of a second eyepiece "D79A", in which case the 2D CPE replaces a part 402 of the 1D CPE on the world side, and the AR grating replaces a part 404 of the 1D CPE on the eye side. Although not shown, a third eyepiece "D79B" can include parts 402 and 404 each replaced by a 1D grating, for example, a half-pitch grating, up to a square ridge.

[0064] Figures 4E to 4G are simulation plots 400e to 400g of the back reflection versus wavelength of the first to third eyepieces, for example, D79, D79A, and D79B, discussed in relation to Figures 4A to 4D. Plots 400e to 400g include simulations for both s-polarized light and p-polarized light of light incident at 20°, 40°, and 60° respectively.

[0065] As can be seen in FIGS. 4E - 4G, the reflectance for p - polarized light is typically greater than that for its s - polarized counterpart. Typically, the reflectance increases or plateaus as the wavelength increases.

[0066] FIGS. 4E - 4G demonstrate that, according to one implementation of the present disclosure, the reflectance as a function of wavelength depends on the angle of incidence. Note that the y - axis of each of FIGS. 4E - 4G is on a different scale. For p - polarized light, the reflectance increases as the angle of incidence increases from 20° to 60°, and for s - polarized light, the reflectance decreases as the angle of incidence increases from 20° to 60°.

[0067] Furthermore, the reflectance is generally lowest for the second eyepiece D79A, highest for the first eyepiece D79, suggesting that the architecture of the second eyepiece minimizes the undesirable back - reflections of these three eyepieces. However, the associated AR grating vectors of the optical elements of the second eyepiece D79A may interfere with the functionality of the CPE, thereby making the design and parameters of the AR grating important.

[0068] 2.0 Case 2: Combined Morphing Grating Optical Element

[0069] The second approach is to use a morphed grating, e.g., a grating having the characteristics of both a primary grating and a second grating.

[0070] FIGS. 5A - 5G show cross - sectional views 500a - 500g of examples of architectures 500a, 500b, 500c, 500d, 500e, 500f, and 500g that include a morphed grating, according to one implementation of the present disclosure. The same key 303 from FIG. 3 is applied to the architectures of FIGS. 5A - 5G. Note that labels 602 and 604 are included to provide additional reference and viewpoints for the description of FIG. 6.

[0071] In some implementations, such as architectures 500a, 500b, 500c, 500d, 500e, 500f, and 500g, the eyepiece region in front of the user's eyes can include, on each side, a primary lattice including CPE / EPE / OPE features, such as 1D or 2D AR elements combined with 1D columns or 2D holes and / or pillars. In some implementations, such as architecture 500f, the eyepiece region in front of the user's eyes can include, on each side, a primary lattice including CPE / EPE / OPE features, such as 1D columns or 2D holes and / or pillars combined with 1D recycler elements. Combining the CPE / EPE / OPE features with the recycler elements on each side can increase other virtual image key point metrics, such as improved transmission-to-reflection ratio and image uniformity, compared to architectures without a morphing optical element.

[0072] The cross-sectional view of architecture 500b shows the repeating patterns of both the primary lattice 602 and the secondary lattice 604 (such that the primary and secondary lattices appear aligned), but the primary lattice 602 and the secondary lattice 604 can be oriented at a non-zero angle relative to each other.

[0073] FIG. 6 is a perspective view 600 of architecture 500b of FIG. 5 according to one implementation of the present disclosure. Architecture 504 includes a primary lattice 602 (marked in FIG. 5) and a secondary lattice 606 (marked in FIG. 5). As can be seen from the perspective view 600, the primary lattice 602 and the secondary lattice 604 can have different orientations and pitches. For example, the primary lattice 602 is oriented perpendicular to the direction of each row of the primary lattice 602, e.g., along arrow 610, and has a pitch indicated by arrow 612. The secondary lattice 604 is oriented perpendicular to the direction of each row of the secondary lattice 604, e.g., along arrow 614, and has a pitch indicated by bracket 616. Thus, other architectures can also include a primary lattice and a secondary lattice oriented at a non-zero angle relative to each other.

[0074] FIG. 6 shows that the morphed grating can have the characteristics of both the primary grating 602 within the secondary grating 604, e.g., two orientations and two pitches that characterize the morphed grating. In other words, the characteristics of only the primary or secondary grating alone cannot fully capture the shape of the morphed grating.

[0075] Morphing the diffraction grating introduces several issues for the augmented reality eyepiece. For example, depending on the parameters of the morphed anti-reflection grating, the user can see multiple shifted copies of the same digital content.

[0076] FIGS. 7A - 7B show plots 700a - 700b representing the effects of various morphed gratings on the momentum of light traveling within the eyepiece according to one implementation of the present disclosure. In both plots 700a and 700b, the secondary grating, e.g., the AR grating, corresponds to the k - vector along the x - axis. However, the magnitudes of the k - vectors are different. In plot 700a, the k - vector k AR 702 of the secondary grating translates the FOV 700 outside the outer circle 701 from the ring between the inner circle and the outer circles 701 and 703. However, the negative version of the k - vector k1705, e.g., the k - vector 706, translates the FOV so that it partially fits within the inner circle 703. Next, the negative version of the k - vector k2707, e.g., the k - vector 708, translates the FOV so that it is positioned partially inside and outside of the inner circle 703, whereby different versions of the expanded FOV out - couple to the user's eye at different angles since some of that FOV does not interact with the recycler.

[0077] To avoid this problem, e.g., out - coupling the same FOV at different angles, the secondary grating vector can have the resulting momentum shift outside the outer circle 701. As shown in plot 700b, the k - vector k of the secondary grating AR710 also translates the FOV700 outward from the ring between the inner and outer circles 701 and 703 to the outside of the outer circle 701. However, none of the negative versions of the k vectors k1712 and k2713, such as the k vector 714, can translate the FOV backward within the outer circle 701, which represents an acceptable k vector for propagation within a substrate having a refractive index of n = 2. Thus, in some implementations, the secondary lattice vector can have a minimum pitch to ensure that light interacting with the secondary lattice is not out-coupled at the wrong angle. For example, the pitch of the secondary lattice can be at least twice smaller than the pitch of the primary lattice by the refractive index of the substrate, because the refractive index of the substrate determines the size of the outer circle 701.

[0078] Figure 8 shows a plot 800 representing the effect of various morphed gratings on the momentum of light traveling within an eyepiece according to one implementation of the present disclosure. Another way to avoid the problem of out-coupling the same FOV at different angles is to select a secondary lattice vector that is a linear combination of the primary lattice vectors k1 and k2. For example, the secondary lattice vector 802 is equal to k1 + k2, the secondary lattice vector 804 is equal to k1 - k2, and the secondary lattice vector 806 is equal to 2×k1 (k1, k2 in FIGS. 7A and 7B). As shown in plot 800, the secondary lattice vectors 802, 804, and 806 translate the FOVs 808 and 810 to another value within the ring between the inner and outer circles 812 and 814. In other words, selecting the secondary lattice k vector to be a linear combination of the primary lattice k vectors ensures that the momentum resulting from the interaction with the morphed lattice shift is outside the outer side of the inner circle. For example, in direct space, this leads to a design choice for the length of the secondary lattice. As a result, only the FOVs propagating at the correct angle are out-coupled. Further, if the pitch of the secondary lattice is less than the wavelength, the secondary lattice also functions as an anti-reflection grating, thereby improving the transmittance and reducing the back reflection.

[0079] 2.1 Simulation-based evidence of transmittance improvement and back reflection reduction

[0080] Figures 9A - 9F show plots 900a - 900f representing the effect of the morphed grating on the wave vectors of light traveling within the corresponding eyepiece according to an implementation of the present disclosure. In each of plots 900b - 900f, the solid line represents the k - vector of the primary grating. In each of plots 900b - 900f, the dashed line represents the k - vector of the secondary grating. Plot 900a represents an eyepiece without a secondary grating.

[0081] Figure 10 shows a plot 1000 of the simulated transmittance profiles of the eyepiece from Figures 9A - 9F versus wavelength according to an implementation of the present disclosure. In Figure 10, light is incident from the world at an angle of 10°, a portion of which is reflected back to the world and a portion of which is transmitted to the user. Each of profiles D_A, D_B, D_C, D_D, D_E, and D_F corresponds respectively to the grating k - vectors of Figures 9A - 9F. An eyepiece without a secondary grating has the lowest transmittance for most of the visible wavelength range, e.g., for λ > 0.5 microns. Thus, typically, including one of the secondary gratings represented by Figures 9B - 9F improves, e.g., increases, the transmittance of the eyepiece.

[0082] Figures 11A and 11B show plot 1100a and plot 1100b of the simulated reflectance profile versus wavelength of the eyepiece from FIGS. 9A - 9F for TM - polarized light and TE - polarized light respectively, according to one implementation of the present disclosure. In plots 1100a and 1100b, light is incident from the user side at an angle of 30°, a part of which is reflected back to the user and a part of which is transmitted to the world. Each of the profiles D_A, D_B, D_C, D_D, D_E, D_F corresponds to the lattice vectors of FIGS. 9A - 9F respectively. The eyepiece without a secondary lattice has the highest reflectance profile over the entire wavelength range. Thus, including one of the secondary lattices represented by FIGS. 9B - 9F improves, for example, reduces the back - reflection of the eyepiece. The combined effect shown by FIGS. 10, 11A, and 11B on the transmission - to - reflection ratio can increase the ratio by up to 10 times compared to an eyepiece without a morphed lattice.

[0083] In some implementations, the light - projection system has three channels, for example, R, G, and B. Thus, each active layer, for example, the layer of the morphed lattice for a particular channel, can be adjusted according to the reflectance and transmittance profiles as a function of wavelength. For example, the morphed lattice for the red channel can have different parameters, such as pitch, shape, height, and orientation, compared to the morphed lattice for the blue channel.

[0084] In some implementations, the transmittance profile of the eyepiece can be increased with only a single active layer of the morphed lattice.

[0085] FIG. 12 shows a plot 1200 of the transmittance versus wavelength of an eyepiece with and without a recycler, such as "D79" and "D79_REC", for both s-polarized and p-polarized light at normal incidence according to an implementation of the present disclosure. As shown by the plot, the transmittance increases for both types of polarization when there is a morphed grating and a primary grating combined with a recycler. The average transmittance over all wavelengths and polarizations of an eyepiece without a morphed grating is 86.7%, while the average is 93.1% for an eyepiece with a morphed grating.

[0086] FIGS. 10, 11A, 11B, and 12 were generated using simulation software. The simulation software approximates how a morphed grating affects display performance. The software processes all ray tracings at all angles of incidence to simulate the display performance of the eyepiece. Based on a ray tracing simulation using basic Maxwell's equations, the efficiency distribution for different angles of incidence within the FOV can be analyzed.

[0087] FIGS. 13A - 13F show far-field efficiency distribution patterns 1300a1 - 1300f2 of a large FoV respectively associated with each of the eyepieces of FIGS. 9A - 9F according to an implementation of the present disclosure. The FOV shown in FIGS. 13A - 13F extends to 53°×53°.

[0088] Performance metrics related to the FOV are the overall efficiency of emissions on the user side (U EBE ) and the world side (W EBE ), the efficiency of 80% of the FOV (U inner80 ) and the full FOV (U fov) is the uniformity score. The uniformity score is the ratio of the difference between the 80th percentile value and the 20th percentile value to the 50th percentile value (median). The left distribution pattern is the raw image, and the second of the right distribution patterns is gamma-corrected with reduced contrast. The center-to-peak (CP) ratio, for example, the value at the center divided by the maximum efficiency within the full FOV, can characterize the uniformity of the pattern. For example, the ideal CP ratio of the AR image can be set to 1, and the CP ratio of pattern 1300a2 is 0.62.

[0089] 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.

[0090] For patterns 1300b1 to 1300f1, the efficiency U EBE and W EBEIt is slightly reduced by, for example, about 1 - 2% compared to the efficiency of pattern 1300a1. The uniformity U of patterns 1300c1, 1300d1, and 1300f1 inner80 and U fov is reduced compared to pattern 1300a1, but the uniformity of patterns 1300b1 and 1300e1 is more prominent in FIGS. 13A and 13C - 13F compared to FIGS. 13B and 13E, as indicated by the dark bands shown by the respective arrows in FIGS. 13A - 13F. Therefore, although there are some drawbacks regarding uniformity and efficiency for certain morphed gratings, those drawbacks can be reduced while improving transmittance and reflectance, as discussed in relation to FIGS. 10, 11A, 11B, and 12.

[0091] In some implementations, using a morphed grating, such as the eyepiece lens of FIG. 9B, can improve uniformity. For example, the efficiency distribution in FIG. 13B has fewer high - frequency artifacts, such as dark bands, compared to FIGS. 13A and 13C - 13F. In some implementations, a high - refractive - index eyepiece lens with a morphed grating can transmit 10% more light over the visible wavelength range than a high - refractive - index eyepiece lens without a morphed grating and can be, for example, more transparent. Therefore, using the morphed grating of FIG. 9B can improve uniformity and, at the same time, improve transmission characteristics and back - reflection characteristics.

[0092] In some implementations, using a morphed grating can improve virtual image quality.

[0093] Figures 13G and 13H show the virtual image uniformity of the eyepiece with the control grating and the morphed grating respectively according to one implementation of the present disclosure. In this example, the green light from the projector creates virtual images 1300g and 1300h. Virtual image 1300h is brighter and more uniform overall than virtual image 1300g, demonstrating that the use of a morphed grating can improve virtual image quality.

[0094] 2.2 Example of the manufacturing process of the combined morphed grating

[0095] Templates for eyepieces with combined primary and secondary gratings, such as morphed 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 morphed surface relief grating onto a high refractive index waveguide substrate using an imprint lithography process.

[0096] Figures 14A - 14F show schematic diagrams of an example of the manufacturing process of a morphed grating according to one implementation of the present disclosure. As a first example, the nanoimprinted primary and secondary gratings can be used directly as an etching mask for transferring the morphed geometry to the polymer to form, for example, an imprint patterned polymer. In some implementations, the etching is complete, conformal, directional, or planarizing etching. In some implementations, the polymer includes a high refractive index non - filler - based polymer with a refractive index of less than 1.8. In some implementations, the polymer includes a high refractive index filler - based polymer with a refractive index in the range between 1.8 and 2.1.

[0097] In FIGS. 14A - 14F, the fabrication process begins by using lithography to pattern a first grating, which can be a grating with a smaller pitch in a specific orientation, e.g., the secondary grating 604 of FIG. 6, using lithography and etching processes. In FIG. 14A, a first pattern 1404 is deposited on a template substrate 1402. In FIG. 14B, the first pattern 1404 is etched into the template substrate 1402, thereby forming a template for the secondary grating. In FIG. 14C, a second pattern 1406 is deposited on the template substrate 1402. In FIG. 14D, the second pattern 1406 is planarized on the template substrate 1402 and etched therein. In FIG. 14E, the second pattern 1406 is removed from the template substrate 1402, thereby forming a template substrate for, e.g., a morphed grating 1412a, a grating having features from both the primary and secondary gratings of different parameters as indicated by the dashed box.

[0098] In some implementations, the step of FIG. 14F follows, which includes creating an inverse tone 1408, e.g., a template having inverse features compared to the template substrate 1402, where the morphed grating 1412b is shown by the dashed box. Creating the inverse tone can be implemented using nanoimprint lithography. In some implementations, the inverse tone 1408, a copy of the final template substrate 1402, or both can be patterned in a material having a high refractive index, such as high refractive index glass, lithium niobate, titanium oxide, and silicon nitride. Using a substrate having a high refractive index can lead to an extended FOV because the refractive index of the substrate determines the range of acceptable wave vectors.

[0099] The etching stop portion, e.g., the depth at which etching ends, can determine the resist layer thickness (RLT) 1410. In some implementations, it may be beneficial to have a thin RLT 1410, e.g., less than 50 nm. For example, when the RLT 1410 is sufficiently thin, e.g., less than 20 nm, it is easier to transfer the pattern of the template substrate 1402 to the high refractive index material because it is not necessary to etch completely through the region of the thin RLT. This allows for a refractive index mismatch between the template substrate and the material forming the morphed grating while retaining the advantages of the shape of the morphed grating. In some implementations, as shown in FIG. 14D, the RLT 1410 is an interconnect RLT, e.g., connecting adjacent ridges 1401a and 1401b of the morphed grating. In some implementations, the etching stop portion is selected such that, as shown in FIG. 14D, the entire vertical portion of the first pattern, the second pattern, or both is removed, in which case the second pattern 1406 has a discontinuous portion.

[0100] In some implementations, the first pattern 1404, e.g., the primary grating, and the second pattern 1406, e.g., the secondary grating, can have different pitches, e.g., different duty cycles, line width gradations, 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.

[0101] Figures 15A - 15F show schematic diagrams of an example of a fabrication process using an intermediate masking layer for a morphed lattice according to one implementation of the present disclosure. As another example, nano - imprinted primary and secondary lattices can be used with an intermediate masking layer for transferring a morphed geometry. In Figure 15A, a first pattern 1502 for a secondary lattice is imprinted onto an intermediate masking layer 1504 on top of a substrate 1506. In some implementations, the intermediate masking layer 1504 contains chromium. In some implementations, the substrate 1506 contains silicon dioxide, such as thermally oxidized silicon or fused silica, on silicon.

[0102] In Figure 15B, a secondary lattice, for example, a lattice with a smaller pitch, is imprinted into the intermediate masking layer 1504. Next, in Figure 15C, a second pattern 1508 for a primary lattice is imprinted on top of the intermediate masking layer 1504 and the remaining portion of the substrate 1506.

[0103] Figure 15D shows etching using the second pattern 1508 for the primary lattice. Figure 15E shows the substrate after removing the remaining portion of the second pattern 1508 and the remaining portion of the intermediate masking layer 1504, thereby forming the final template 1510. Figure 15E shows a cross - sectional view of the final template 1510, while Figure 15F shows a plan view of the final template 1510.

[0104] In some implementations, the remaining intermediate layer can be left to determine the height of additional lattices, such as recyclers, in the final imprint. In some implementations, electron beam lithography is used throughout Figures 15A - 15F. In some implementations, a combination of imprint lithography and etching results in sharply defined corners and edges of two - dimensionally patterned holes and pillars.

[0105] Processes such as J-FIL inkjet lithography can fabricate templates with analog or zoned gradation levels and can have a variable gradation axis. In some implementations, such as when using the J-FIL process with a stepwise residual layer thickness (RLT) using inkjet dispensing, it is possible to pattern transfer a stepwise design in a first lattice lithography etching step, a second lattice lithography etching step (as in FIGS. 16A-16F), or both (as in FIGS. 17A-17F).

[0106] FIGS. 16A-16F show a schematic diagram of an example of a fabrication process for a morphed lattice having a stepwise primary stage according to one implementation of the present disclosure. The steps of FIGS. 16A-16F are similar to the steps of FIGS. 14A-14F, except that the primary lattice, e.g., the second pattern 1606, is stepwise instead of having a constant height as in the second pattern 1406.

[0107] FIGS. 17A-17F show a schematic diagram of an example of a fabrication process for a morphed lattice in which both the primary lattice and the secondary lattice are stepwise according to one implementation of the present disclosure. The steps of FIGS. 17A-17F are similar to the steps of FIGS. 14A-14F, except that the primary lattice, e.g., the second pattern 1706, and the secondary lattice, e.g., the first pattern 1704, are stepwise instead of having a constant height as in the first and second patterns 1404 and 1406.

[0108] This fabrication process can also be adapted to morphed blazed geometric shapes other than binary lattices, such as inclined, serrated, blazed serrated, multi-step, meta-structures, cylindrical, inclined cylindrical, holes, inclined holes, trapezoidal cubes, cubes, rectangular parallelepipeds, and other shapes.

[0109] Figures 18A - 18F show schematic diagrams of an example of a manufacturing process of a morphed grating in which the primary grating is a sawtooth grating according to an implementation of the present disclosure. The steps in Figures 18A - 18F are the same as the steps in Figures 14A - 14F, except that the primary grating, for example, the second pattern 1806 has a sawtooth shape instead of a binary shape like the second pattern 1406. Using a sawtooth shape for the primary grating can improve the light extraction ratio from the user to the world by out - coupling more light towards the user while maintaining a high transmittance.

[0110] All of the manufacturing processes described with reference to Figures 14A - 18F can be performed on both sides of the substrate, for example, the world side and the user side.

[0111] In some implementations, the grating formed by the manufacturing process described with reference to Figures 14A - 18F can be conformally or directionally over - coated with one or more layers of a low - refractive - index or high - refractive - index (1.45 < n < 2.7) material. For example, etching can create trench openings within the morphed grating, for example, above where RLT1410 is labeled in Figure 14D and between adjacent ridges 1401a and 1401b. In some implementations, the grating is over - coated with a material having a refractive index in the range of 1.15 - 2.1, such as an organic sol - gel material or a flowable Si3N4, to at least partially fill the trench openings. In some implementations, the maximum thickness of the over - coating layer can be between 500 nm and 10 microns. In some implementations, the over - coating at least partially covers the CPE, OPE, EPE, or a combination thereof on one or both sides of the substrate.

[0112] 3.0 Case 3: Stacked Gratings with Multiple Refractive Indices

[0113] The third approach is to stack gratings with different refractive indices. For example, a high refractive index first-order diffraction surface relief grating can be etched or patterned using deposition, such as physical vapor deposition (PVD) and atomic layer deposition (ALD). The first surface relief grating can include coatings of high or low refractive index materials such as TiO2, SiC, SiO2, Si3N4, and ZrO2 (1.5 < n < 2.7) that can be planarized using nanoimprint lithography, can include a second grating (1.5 > n > 1.7) such as an AR or recycler pattern, or vice versa.

[0114] FIG. 19A shows an example of an eyepiece lens including a secondary grating 1902 according to one implementation of the present disclosure. The secondary grating 1902 can include 1D or 2D CPE / OPE / EPE features embedded within low refractive index coating films 1904 on both sides of a substrate 1901. There is an ICG 1906 on a first side of the eyepiece lens 1900a, and an AR grating 1908 is on the opposite side of the eyepiece lens 1900a.

[0115] FIG. 19B shows an eyepiece lens 1900b after a primary grating 1910 is stacked on the secondary grating 1902 according to one implementation of the present disclosure. Since the primary grating 1910 faces air and has a lower refractive index material than the refractive index of the embedded secondary grating 1902, there remains a refractive index modulation such as a change in refractive index between the eyepiece lens 1900b and air, for example. Stacking waveguides with different refractive indices can allow for a more gradual change in refractive index. For example, light from air can be incident on a first grating having a refractive index close to 1 (reducing the refractive index difference and thus back reflection), and then the light can proceed from the first grating to a second grating having a large refractive index, thereby enabling a large FOV. In some implementations, the primary grating 1910 is coated with a low refractive index material such as MgF2 (n = 1.38) or SiO2 (n = 1.45), which can further improve transmittance and reduce back reflection.

[0116] In some embodiments, as shown in FIG. 19A, the first side of the eyepiece lens 1900b is proximal to the user, e.g., the side having the ICG 1906, and the second side of the eyepiece lens 1900b, e.g., the side having the AR grating 1908, is distal to the user, e.g., the "world side". In some embodiments, the first side of the eyepiece lens 1900b is distal to the user, e.g., the side having the ICG 1906, and the second side of the eyepiece lens 1900b, e.g., the side having the AR grating 1908, is proximal to the user. Thus, the primary grating 1910 and the secondary grating 1902 can each be proximal to the user, distal to the user, or both (when the primary grating and the secondary grating are on opposite sides of the substrate).

[0117] FIG. 20A shows an example of a stacked grating 2000a according to one embodiment of the present disclosure. 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 can have a high refractive index, such as glass with n = 2, for example, the primary grating 2004 can have a first refractive index, such as n1 = 1.65, for example, and the secondary grating 2006 can have a second refractive index n2.

[0118] FIG. 20B shows a plot 2000b having a transmittance profile of the stacked grating 2000a for five versions of the second refractive index as a function of wavelength according to one embodiment of the present disclosure. The light in FIG. 20B is incident in the normal direction and is s-polarized. "D79" refers to the case where there is no secondary grating 2006, e.g., when the primary grating 2004 and the secondary grating 2006 are made of the same material and thus have the same refractive index, e.g., n1 = n2 = 1.65. FIG. 20B shows profiles where n2 = 2.4, 2.1, 1.8, and 1.4, for example, where n2 is greater than n1 and less than n1.

[0119] The profile of FIG. 20B shows that the transmittance of the stacked gratings, e.g., a primary grating stacked on a secondary grating having different refractive indices, approaches the transmittance of the unstacked surface relief grating, e.g., D79, at wavelengths less than about 0.6 microns and can be greater than the transmittance of the unstacked surface relief grating at wavelengths greater than about 0.6 microns. In some implementations, a secondary grating having a refractive index different from that of the primary grating can reduce the rainbow artifact when embedding the primary grating.

[0120] As described herein, there are various geometric shapes for the primary and secondary gratings to increase transmittance and reduce backreflection without sacrificing the quality of the display of digital content.

[0121] While this application is defined by the appended claims, it should also be understood that the invention can (additionally or alternatively) be defined according to the following examples.

[0122] Example 1: An eyepiece lens, a substrate, an input coupling grating on a first side of the substrate, and a morphed grating including characteristics of both a primary grating and a secondary grating on at least the first side of the substrate.

[0123] Example 2: The eyepiece lens of Example 1, wherein the primary grating has two or more layers having two or more associated pitches and orientations, the two or more associated pitches and orientations determine two or more wave vectors and momentum spaces, the secondary grating has a pitch and orientation that determine a wave vector and a momentum space, and the wave vector of the secondary grating is a linear combination of two or more wave vectors of the primary grating.

[0124] Example 3: The eyepiece lens of either Example 1 or 2, wherein the pitch of the secondary grating is at least twice smaller than any pitch of the primary grating by the refractive index of the substrate.

[0125] Example 4: An eyepiece lens according to any of the preceding examples, wherein the pitch of the first grating is different from the pitch of the second grating.

[0126] Example 5: An eyepiece lens according to any of the preceding examples, wherein the orientation of the first grating is different from the orientation of the second grating.

[0127] Example 6: An eyepiece lens according to any of the preceding examples, wherein the shape of the first grating is different from the shape of the second grating, and the shape of the first grating and the shape of the second grating include a portion having at least one shape selected from the group consisting of binary, inclined, blaze sawtooth, multi-step structure, meta-structure, cylinder, hole, inclined hole, inclined cylinder, trapezoidal cube, cube, and rectangular parallelepiped.

[0128] Example 7: An eyepiece lens according to any of the preceding examples, wherein at least one of the first grating and the second grating has a stepped height profile.

[0129] Example 8: An eyepiece lens according to any of the preceding examples, wherein the refractive index of the first grating is different from the refractive index of the second grating.

[0130] Example 9: An eyepiece lens according to any of the preceding examples, wherein the first grating is at least partially present in one of an exit pupil expander, an orthogonal pupil expander, and a compound pupil expander.

[0131] Example 10: An eyepiece lens according to any of the preceding examples, wherein the second grating is either a recycling grating or an anti-reflection grating.

[0132] Example 11: An eyepiece lens according to any of the preceding examples, wherein at least one of the first grating and the second grating is one-dimensional.

[0133] Example 12: An eyepiece lens according to any of the preceding examples, wherein at least one of the first grating and the second grating is two-dimensional.

[0134] Example 13: An eyepiece lens according to any of the preceding examples, wherein the pitch of the second grating is different from the pitch of the first grating.

[0135] Example 14: The eyepiece lens of Example 13, where the pitch of the secondary grating is smaller than the pitch of the primary grating.

[0136] Example 15: The eyepiece lens of any of the preceding examples, where the line width of the secondary grating is different from the line width of the primary grating.

[0137] Example 16: The eyepiece lens of any of the preceding examples, where the substrate has a refractive index in the range of 1.5 to 2.7.

[0138] Example 17: The eyepiece lens of any of the preceding examples, where the primary grating includes a portion on the second side of the substrate opposite to the first side of the substrate.

[0139] Example 18: The eyepiece lens of any of the preceding examples, where the first side of the substrate is proximal to the user and the second side of the substrate is distal to the user.

[0140] Example 19: The eyepiece lens of any of the preceding examples, where the first side of the substrate is distal to the user and the second side of the substrate is proximal to the user.

[0141] Example 20: The eyepiece lens of any of the preceding examples, further comprising an antireflection grating on the second side of the substrate opposite to the first side of the substrate.

[0142] Example 21: The eyepiece lens of any of the preceding examples, where at least one of the primary grating and the secondary grating is etched into the substrate.

[0143] Example 22: The eyepiece lens of any of the preceding examples, where at least one of the primary grating and the secondary grating is etched into a coating on the substrate.

[0144] Example 23: The eyepiece lens of Example 22, where the coating is partially on at least one of the primary grating and the secondary grating.

[0145] Example 24: The eyepiece lens of Example 23, where the coating has a refractive index in the range of 1.45 to 2.7.

[0146] Example 25: The eyepiece lens according to any one of Examples 23 or 24, wherein the coating contains at least one of SiO2, Si3N4, ZrO2, TiO2, or SiC.

[0147] Example 26: The eyepiece lens according to any one of Examples 23 to 25, wherein the coating at least partially fills the trench openings in at least one of the primary grating and the secondary grating.

[0148] Example 27: The eyepiece lens according to Example 23, wherein the coating has a refractive index in the range of 1.15 to 2.1.

[0149] Example 28: The eyepiece lens according to either Example 26 or Example 27, wherein the maximum thickness of the coating is in the range of 500 nanometers to 10 micrometers.

[0150] Example 29: The eyepiece lens according to any one of Examples 26 to 28, wherein at least one of the primary grating and the secondary grating includes a discontinuous portion.

[0151] Example 30: The eyepiece lens according to any one of Examples 26 to 29, wherein the etching of at least one of the primary grating and the secondary grating is at least one of partial, complete, conformal, directional, or planarized.

[0152] Example 31: The eyepiece lens according to any one of Examples 26 to 30, wherein the etching of at least one of the primary grating and the secondary grating is on the side proximal to the user of the substrate, on the side distal to the user of the substrate, or on both sides thereof.

[0153] Example 32: The eyepiece lens according to any one of the preceding examples, wherein at least one of the primary grating and the secondary grating is imprinted on the substrate by nanoimprint lithography.

[0154] Example 33: The eyepiece lens according to Example 32, wherein the resist layer thickness is less than 50 nanometers.

[0155] Example 34: An eyeglass lens according to any one of Example 32 or Example 33, wherein at least one of the primary grating and the secondary grating includes an imprinted polymer made of a non-filler-based polymer having a refractive index of less than 1.8.

[0156] Example 35: An eyeglass lens according to any one of Example 32 or Example 33, wherein at least one of the primary grating and the secondary grating includes an imprinted polymer made of a filler-based polymer having a refractive index in the range of 1.8 to 2.1.

[0157] Example 36: An eyeglass lens, comprising: a substrate; an input coupling grating on a first side of the substrate; a stacked grating including 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 and the second refractive index are different; and the eyeglass lens is provided with the above components.

[0158] Example 37: The eyeglass lens according to Example 36, wherein the second refractive index is greater than the first refractive index.

[0159] Example 38: The eyeglass lens according to Example 36, wherein the second refractive index is less than the first refractive index.

[0160] Example 39: The eyeglass lens according to any one of Examples 36 to 38, wherein the pitch of the primary grating is different from the pitch of the secondary grating.

[0161] Example 40: The eyeglass lens according to any one of Examples 36 to 39, wherein the orientation of the primary grating is different from the orientation of the secondary grating.

[0162] Example 41: The eyeglass lens according to any one of Examples 36 to 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 at least one part having a shape selected from the group consisting of binary, inclined, blazed sawtooth, multi-stage structure, meta-structure, cylinder, hole, inclined hole, inclined cylinder, trapezoidal cube, cube, and rectangular parallelepiped.

[0163] Example 42: An eyepiece lens according to any one of Examples 36 to 41, wherein at least one of the primary grating and the secondary grating has a stepped height profile.

[0164] Example 43: An eyepiece lens according to any one of Examples 36 to 42, wherein the primary grating is at least partially present in one of an exit pupil expander, an orthogonal pupil expander, and a compound pupil expander.

[0165] Example 44: An eyepiece lens according to any one of Examples 36 to 43, wherein the secondary grating is either a recycling grating or an anti-reflection grating.

[0166] Example 45: An eyepiece lens according to any one of Examples 36 to 44, wherein at least one of the primary grating and the secondary grating is one-dimensional.

[0167] Example 46: An eyepiece lens according to any one of Examples 36 to 45, wherein at least one of the primary grating and the secondary grating is two-dimensional.

[0168] Example 47: An eyepiece lens according to any one of Examples 36 to 46, wherein the pitch of the secondary grating is different from the pitch of the primary grating.

[0169] Example 48: An eyepiece lens according to Example 47, wherein the pitch of the secondary grating is smaller than the pitch of the primary grating.

[0170] Example 49: An eyepiece lens according to any one of Examples 36 to 48, wherein the line width of the secondary grating is different from the line width of the primary grating.

[0171] Example 50: An eyepiece lens according to any one of Examples 36 to 49, wherein the substrate has a refractive index in the range of 1.5 to 2.7.

[0172] Example 51: An eyepiece lens according to any one of Examples 36 to 50, wherein the primary grating includes a portion on a second side of the substrate opposite to a first side of the substrate.

[0173] Example 52: An eyepiece lens according to Example 51, wherein the first side of the substrate is proximal to the user and the second side of the substrate is distal to the user.

[0174] Example 53: The eyepiece of Example 51, wherein the first side of the substrate is distal to the user and the second side of the substrate is proximal to the user.

[0175] Example 54: The eyepiece according to any one of Examples 36 to 53, further comprising an antireflection grating on the second side of the substrate opposite to the first side of the substrate.

[0176] Example 55: The eyepiece according to any one of Examples 36 to 54, wherein at least one of the primary grating and the secondary grating is etched into the substrate.

[0177] Example 56: The eyepiece according to any one of Examples 36 to 55, wherein at least one of the primary grating and the secondary grating is etched into a coating on the substrate.

[0178] Example 57: The eyepiece of Example 56, wherein the coating of at least one of the primary grating and the secondary grating is partial.

[0179] Example 58: The eyepiece of Example 57, wherein the coating has a refractive index in the range of 1.45 to 2.7.

[0180] Example 59: The eyepiece according to either Example 57 or Example 58, wherein the coating contains at least one of SiO2, Si3N4, ZrO2, TiO2, or SiC.

[0181] Example 60: The eyepiece according to any one of Examples 57 to 59, wherein the coating at least partially fills the trench openings in at least one of the primary grating and the secondary grating.

[0182] Example 61: The eyepiece of Example 60, wherein the coating has a refractive index in the range of 1.15 to 2.1.

[0183] Example 62: The eyepiece according to either Example 60 or Example 61, wherein the maximum thickness of the coating is in the range of 500 nanometers to 10 microns.

[0184] Example 63: An eyepiece lens according to any one of Examples 60 to 62, wherein at least the primary grating and the secondary grating include discontinuous portions.

[0185] Example 64: An eyepiece lens according to any one of Examples 60 to 63, wherein the etching of at least one of the primary grating and the secondary grating is at least one of partial, complete, conformal, directional, or planarized.

[0186] Example 65: An eyepiece lens according to any one of Examples 60 to 64, wherein the etching of at least one of the primary grating and the secondary grating is on the side proximal to the user of the substrate, on the side distal to the user of the substrate, or on both sides thereof.

[0187] Example 66: An eyepiece lens according to any one of Examples 36 to 65, wherein at least one of the primary grating and the secondary grating is imprinted on the substrate by nanoimprint lithography.

[0188] Example 67: An eyepiece lens according to Example 66, wherein the eyepiece lens includes a resist layer thickness of less than 50 nanometers.

[0189] Example 68: An eyepiece lens according to either Example 66 or Example 67, wherein at least one of the primary grating and the secondary grating includes an imprinted polymer made of a non-filler-based polymer having a refractive index of less than 1.8.

[0190] Example 69: An eyepiece lens according to any one of Examples 66 to 69, wherein at least one of the primary grating and the secondary grating includes an imprinted polymer made of a filler-based polymer having a refractive index in the range of 1.8 to 2.1.

[0191] Example 70: An eyepiece lens, comprising: a substrate; an input coupling grating on a first side of the substrate; a primary grating on a first side of the substrate; a secondary grating 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; and the eyepiece lens.

[0192] Example 71: The eyepiece lens of Example 70, wherein the orientation of the primary grating is different from the orientation of the secondary grating.

[0193] Example 72: The eyepiece lens according to any one of 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 selected from the group consisting of binary, inclined, blaze sawtooth, multi-stage structure, meta-structure, cylinder, hole, inclined hole, inclined cylinder, trapezoidal cube, cube, and rectangular parallelepiped.

[0194] Example 73: The eyepiece lens according to any one of Examples 70 to 72, wherein at least one of the primary grating and the secondary grating has a stepped height profile.

[0195] Example 74: The eyepiece lens according to any one of Examples 70 to 73, wherein the refractive index of the primary grating is different from the refractive index of the secondary grating.

[0196] Example 75: The eyepiece lens according to any one of Examples 70 to 74, wherein the primary grating is at least partially present in one of an exit pupil expander, an orthogonal pupil expander, and a compound pupil expander.

[0197] Example 76: The eyepiece lens according to any one of Examples 70 to 75, wherein the secondary grating is either a recycling grating or an anti-reflection grating.

[0198] Example 77: The eyepiece lens according to any one of Examples 70 to 76, wherein at least one of the primary grating and the secondary grating is one-dimensional.

[0199] Example 78: The eyepiece lens according to any one of Examples 70 to 77, wherein at least one of the primary grating and the secondary grating is two-dimensional.

[0200] Example 79: The eyepiece lens according to any one of Examples 70 to 78, wherein the line width of the secondary grating is different from the line width of the primary grating.

[0201] Example 80: The eyepiece lens according to any one of Examples 70 to 79, wherein the substrate has a refractive index in the range of 1.5 to 2.7.

[0202] Example 81: The primary grating includes a portion on the second side of the substrate opposite to the first side of the substrate, and is an eyepiece lens according to any one of Examples 70 to 80.

[0203] Example 82: The first side of the substrate is proximal to the user, and the second side of the substrate is distal to the user, and is the eyepiece lens of Example 81.

[0204] Example 83: The first side of the substrate is distal to the user, and the second side of the substrate is proximal to the user, and is the eyepiece lens of Example 81.

[0205] Example 84: The anti-reflection grating is further provided on the second side of the substrate opposite to the first side of the substrate, and is an eyepiece lens according to any one of Examples 70 to 83.

[0206] Example 85: At least one of the primary grating and the secondary grating is etched in the substrate, and is an eyepiece lens according to any one of Examples 70 to 84.

[0207] Example 86: At least one of the primary grating and the secondary grating is etched in a coating on the substrate, and is an eyepiece lens according to any one of Examples 70 to 85.

[0208] Example 87: The coating of at least one of the primary grating and the secondary grating is partial, and is the eyepiece lens of Example 86.

[0209] Example 88: The coating has a refractive index in the range of 1.45 to 2.7, and is the eyepiece lens of Example 87.

[0210] Example 89: The coating includes at least one of SiO2, Si3N4, ZrO2, TiO2, or SiC, and is the eyepiece lens according to either Example 87 or Example 88.

[0211] Example 90: The coating at least partially fills the trench openings in at least one of the primary grating and the secondary grating, and is the eyepiece lens according to any one of Examples 87 to 89.

[0212] Example 91: The coating is an eyepiece lens according to any one of Examples 87 to 90, having a refractive index in the range of 1.15 to 2.1.

[0213] Example 92: The coating has a maximum thickness in the range of 500 nanometers to 10 micrometers, and is an eyepiece lens according to any one of Examples 87 to 91.

[0214] Example 93: The eyepiece lens according to any one of Examples 87 to 92, wherein at least the primary grating and the secondary grating include discontinuous portions.

[0215] Example 94: The eyepiece lens according to any one of Examples 87 to 93, wherein the etching of at least one of the primary grating and the secondary grating is at least one of partial, complete, conformal, directional, or planarized.

[0216] Example 95: The eyepiece lens according to any one of Examples 70 to 94, wherein the etching of at least one of the primary grating and the secondary grating is on the side proximal to the user of the substrate, on the side distal to the user of the substrate, or both.

[0217] Example 96: The eyepiece lens according to any one of Examples 70 to 95, wherein at least one of the primary grating and the secondary grating is imprinted on the substrate by nanoimprint lithography.

[0218] Example 97: The eyepiece lens according to any one of Examples 70 to 96, including a resist layer thickness of less than 50 nanometers.

[0219] Example 98: The eyepiece lens according to any one of Examples 70 to 97, wherein at least one of the primary grating and the secondary grating includes an imprinted polymer made of a non-filler-based polymer having a refractive index of less than 1.8.

[0220] Example 99: The eyepiece lens according to any one of Examples 70 to 98, wherein at least one of the primary grating and the secondary grating includes an imprinted polymer made of a filler-based polymer having a refractive index in the range of 1.8 to 2.1.

[0221] While this disclosure includes details of many specific implementations, these should not be construed as limitations on the scope of any implementation of the disclosure or on what may be claimed, but rather as descriptions of features specific to exemplary implementations. Specific features described herein in the context of separate implementations can also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation can also be implemented separately, or in any suitable sub-combination, in multiple implementations. Further, features may be described above as acting in certain combinations and may initially be claimed as such, but one or more features from a claimed combination may in some cases be deleted from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination.

[0222] Similarly, operations are shown in the drawings in a particular order, but this should not be understood as requiring that such operations be performed in the particular order shown, or in a sequential order, or that all of the operations shown be performed, to achieve desirable results. Additionally, the processes shown in the figures do not necessarily require the particular order, or sequential order, shown to achieve desirable results. Although various implementations of the invention are described herein, it is to be understood that they are presented by way of example only. Many variations and modifications may become apparent to those skilled in the art upon reading this specification. The breadth and scope of the invention are not limited by the examples described herein, but may be interpreted broadly to include such variations and modifications.

Claims

1. An eyepiece lens comprising: a substrate; an input coupling grating on a first side of the substrate; a morphed grating including characteristics of both a primary grating and a secondary grating on at least the first side of the substrate .

2. The eyepiece lens according to claim 1, wherein the primary grating has two or more layers having two or more associated pitches and orientations, the two or more associated pitches and orientations determine two or more wave vectors and momentum spaces, the secondary grating has a pitch and an orientation that determine a wave vector and a 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.

3. The eyepiece lens according to claim 1, wherein the pitch of the secondary grating is at least twice smaller than any pitch of the primary grating with respect to the refractive index of the substrate.

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

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

6. The eyepiece lens 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 at least one part having a shape from the group consisting of binary, inclined, blazed sawtooth, multi-stage structure, meta-structure, cylinder, hole, inclined hole, inclined cylinder, trapezoidal cube, cube, and rectangular parallelepiped.

7. The eyepiece lens according to claim 1, wherein at least one of the primary grating and the secondary grating has a stepped height profile.

8. The eyepiece lens 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 lens according to claim 1, wherein the primary grating is at least partially present in one of an exit pupil expander, an orthogonal pupil expander, and a compound pupil expander.

10. The eyepiece lens according to claim 1, wherein the secondary grating is either a recycling grating or an anti-reflection grating.

11. The eyepiece lens according to claim 1, wherein at least one of the primary grating and the secondary grating is one-dimensional.

12. The eyepiece lens according to claim 1, wherein at least one of the primary grating and the secondary grating is two-dimensional.

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

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

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

16. The eyepiece according to claim 1, wherein the substrate has a refractive index in the range of 1.5 to 2.

7.

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

18. The eyepiece according to claim 17, wherein the first side of the substrate is proximal to the user, and the second side of the substrate is distal to the user.

19. The eyepiece according to claim 17, wherein the first side of the substrate is distal to the user, and the second side of the substrate is proximal to the user.

20. The eyepiece according to claim 1, further comprising an antireflection grating on a second side of the substrate opposite to the first side of the substrate.

21. The eyepiece according to claim 1, wherein at least one of the primary grating and the secondary grating is etched in the substrate.

22. The eyepiece according to claim 1, wherein at least one of the primary grating and the secondary grating is etched in a coating on the substrate.

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

24. The eyepiece according to claim 23, wherein the coating has a refractive index in the range of 1.45 to 2.

7.

25. The coating is SiO ２ , Si ３ N ４ , ZrO ２ , TiO ２ , or at least one of SiC, the eyepiece according to claim 23.

26. The eyepiece according to claim 23, wherein the coating at least partially fills a trench opening in at least one of the primary grating and the secondary grating.

27. The eyepiece according to claim 26, wherein the coating has a refractive index in the range of 1.15 to 2.

1.

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

29. The eyepiece according to claim 26, wherein at least one of the primary grating and the secondary grating includes a discontinuous portion.

30. The eyepiece according to claim 26, wherein at least one of the etching of the primary grating and the secondary grating is at least one of partial, complete, conformal, directional, or planarized.

31. The eyepiece according to claim 26, wherein at least one of the etching of the primary grating and the secondary grating is on the side proximal to the user of the substrate, on the side distal to the user of the substrate, or both.

32. The eyepiece according to claim 1, wherein at least one of the primary grating and the secondary grating is imprinted on the substrate by nanoimprint lithography.

33. The eyepiece according to claim 32, wherein the eyepiece includes a resist layer thickness of less than 50 nanometers.

34. The eyepiece according to claim 32, wherein at least one of the primary grating and the secondary grating includes an imprinted polymer made of a non-filler-based polymer having a refractive index of less than 1.

8.

35. The eyepiece according to claim 32, wherein at least one of the primary grating and the secondary grating includes an imprinted polymer made of a filler-based polymer having a refractive index in the range of 1.8 to 2.

1.

36. An eyepiece, comprising: a substrate; an input coupling grating on a first side of the substrate; a stacked grating including 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 and the second refractive index are different; the stacked grating and an eyepiece.

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

38. The eyepiece according to claim 36, wherein the second refractive index is smaller than the first refractive index.

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

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

41. The shape of the primary grating is different from that 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 selected from the group consisting of binary, inclined, blaze sawtooth, multi-stage structure, meta-structure, cylinder, hole, inclined hole, inclined cylinder, trapezoidal cube, cube, and rectangular parallelepiped. The eyepiece according to claim 36.

42. The eyepiece according to claim 36, wherein at least one of the primary grating and the secondary grating has a stepped height profile.

43. The eyepiece according to claim 36, wherein the primary grating is at least partially present in one of an exit pupil expander, an orthogonal pupil expander, and a composite pupil expander.

44. The eyepiece according to claim 36, wherein the secondary grating is either a recycler grating or an anti-reflection grating.

45. The eyepiece according to claim 36, wherein at least one of the primary grating and the secondary grating is one-dimensional.

46. The eyepiece according to claim 36, wherein at least one of the primary grating and the secondary grating is two-dimensional.

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

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

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

50. The eyepiece according to claim 36, wherein the substrate has a refractive index in the range of 1.5 to 2.

7.

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

52. The eyepiece according to claim 51, wherein the first side of the substrate is proximal to the user, and the second side of the substrate is distal to the user.

53. The eyepiece according to claim 51, wherein the first side of the substrate is distal to the user, and the second side of the substrate is proximal to the user.

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

55. The eyepiece according to claim 36, wherein at least one of the primary grating and the secondary grating is etched in the substrate.

56. The eyepiece lens according to claim 36, wherein at least one of the primary grating and the secondary grating is etched in a coating on the substrate.

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

58. The eyepiece lens according to claim 57, wherein the coating has a refractive index in the range of 1.45 to 2.

7.

59. The coating is SiO ２ , Si ３ N ４ , ZrO ２ , TiO ２ , or at least one of SiC, the eyepiece according to claim 57.

60. The eyepiece lens according to claim 57, wherein the coating at least partially fills a trench opening in at least one of the primary grating and the secondary grating.

61. The eyepiece lens according to claim 60, wherein the coating has a refractive index in the range of 1.15 to 2.

1.

62. The eyepiece lens according to claim 60, wherein a maximum thickness of the coating is in the range of 500 nanometers to 10 microns.

63. The eyepiece lens according to claim 60, wherein at least the primary grating and the secondary grating include discontinuous portions.

64. The eyepiece lens according to claim 60, wherein the etching of at least one of the primary grating and the secondary grating is at least one of partial, complete, conformal, directional, or planarized.

65. The eyepiece lens according to claim 60, wherein the etching of at least one of the primary grating and the secondary grating is on a side proximal to the user of the substrate, on a side distal to the user of the substrate, or both.

66. The eyepiece lens according to claim 36, wherein at least one of the primary grating and the secondary grating is imprinted on the substrate by nanoimprint lithography.

67. The eyepiece lens according to claim 66, wherein the eyepiece lens includes a resist layer thickness of less than 50 nanometers.

68. The eyepiece lens according to claim 66, wherein at least one of the primary grating and the secondary grating includes an imprinted polymer made of a non-filler-based polymer having a refractive index of less than 1.

8.

69. The eyepiece lens according to claim 66, wherein at least one of the primary grating and the secondary grating includes an imprinted polymer made of a filler-based polymer having a refractive index in the range of 1.8 to 2.

1.

70. An eyepiece lens, comprising: a substrate; an input coupling grating on a first side of the substrate; The primary grating on the first side of the substrate, and the secondary grating on the second side of the substrate, which is opposite to the first side of the substrate, wherein the pitch of the secondary grating is smaller than the pitch of the primary grating. A eyepiece lens comprising the same.

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

72. 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 at least one part having a shape selected from the group consisting of binary, inclined, blaze sawtooth, multi-stage structure, meta-structure, cylinder, hole, inclined hole, inclined cylinder, trapezoidal cube, cube, and rectangular parallelepiped. The eyepiece lens according to claim 70.

73. The eyepiece lens according to claim 70, wherein at least one of the primary grating and the secondary grating has a stepped height profile.

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

75. The eyepiece lens according to claim 70, wherein the primary grating is at least partially present in one of an exit pupil expander, an orthogonal pupil expander, and a compound pupil expander.

76. The eyepiece lens according to claim 70, wherein the secondary grating is either a recycling grating or an anti-reflection grating.

77. The eyepiece lens according to claim 70, wherein at least one of the primary grating and the secondary grating is one-dimensional.

78. The eyepiece lens according to claim 70, wherein at least one of the primary grating and the secondary grating is two-dimensional.

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

80. The eyepiece lens according to claim 70, wherein the substrate has a refractive index in the range of 1.5 to 2.

7.

81. The eyepiece lens according to claim 70, wherein the primary grating includes a part on the second side of the substrate, which is opposite to the first side of the substrate.

82. The eyepiece lens according to claim 81, wherein the first side of the substrate is proximal to the user, and the second side of the substrate is distal to the user.

83. The eyepiece lens according to claim 81, wherein the first side of the substrate is distal to the user, and the second side of the substrate is proximal to the user.

84. The eyepiece according to claim 70, further comprising an antireflection grating on a second side of the substrate opposite to the first side of the substrate.

85. The eyepiece according to claim 70, wherein at least one of the primary grating and the secondary grating is etched in the substrate.

86. The eyepiece according to claim 70, wherein at least one of the primary grating and the secondary grating is etched in a coating on the substrate.

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

88. The eyepiece according to claim 87, wherein the coating has a refractive index in the range of 1.45 to 2.

7.

89. The coating is SiO ２ , Si ３ N ４ , ZrO ２ , TiO ２ , or at least one of SiC, the eyepiece according to claim 87.

90. The eyepiece according to claim 87, wherein the coating at least partially fills a trench opening in at least one of the primary grating and the secondary grating.

91. The eyepiece according to claim 90, wherein the coating has a refractive index in the range of 1.15 to 2.

1.

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

93. The eyepiece according to claim 90, wherein at least the primary grating and the secondary grating include discontinuous portions.

94. The eyepiece according to claim 90, wherein the etching of at least one of the primary grating and the secondary grating is at least one of partial, complete, conformal, directional, or planarized.

95. The eyepiece according to claim 70, wherein the etching of at least one of the primary grating and the secondary grating is on a side proximal to the user of the substrate, a side distal to the user of the substrate, or both.

96. The eyepiece according to claim 70, wherein at least one of the primary grating and the secondary grating is imprinted on the substrate by nanoimprint lithography.

97. The eyepiece according to claim 70, wherein the eyepiece includes a resist layer thickness of less than 50 nanometers.

98. The eyepiece according to claim 70, wherein at least one of the primary grating and the secondary grating includes an imprinted polymer made of a non-filler-based polymer having a refractive index of less than 1.

8.

99. The eyeglass lens according to claim 70, wherein at least one of the primary grating and the secondary grating includes an imprinted polymer made of a filler-based polymer having a refractive index in the range of 1.8 to 2.1.

Images