Outcoupling suppression in waveguide displays

Abstract

A pupil replicating waveguide for a projector display includes a slab of transparent material for propagating display light in the slab by total internal reflection. A diffraction grating is supported by the slab. The diffraction grating includes a plurality of tapered, tilted fringes in a substrate for out-coupling display light from the slab into blazed diffraction orders by diffraction. A larger portion of the display light is out-coupled into the blazed diffraction orders, while a smaller portion of the display light is out-coupled into non-blazed diffraction orders. The tapered fringes cause the duty cycle of the diffraction grating to vary along the thickness direction of the diffraction grating so as to suppress the portion of the display light that is out-coupled into the non-blazed diffraction orders.

Description

Technical Field

[0001] The present invention relates to wearable headsets, and more particularly to components and modules for wearable visual display headsets.

[0002] background

[0003] Head-mounted displays (HMDs), helmet-mounted displays, near-eye displays (NEDs), and the like are increasingly being used to display virtual reality (VR) content, augmented reality (AR) content, mixed reality (MR) content, and the like. Such displays are finding applications in a variety of fields, including entertainment, education, training, and biomedical sciences, to name a few. The VR / AR / MR content displayed can be three-dimensional (3D) to enhance the experience and match virtual objects with real objects observed by the user. The user's eye position and gaze direction and / or orientation can be tracked in real time, and the displayed image can be dynamically adjusted based on the user's head orientation and gaze direction to provide a better immersive experience in a simulated or augmented environment.

[0004] Head-mounted displays require compact display devices. Because the display of an HMD or NED is usually worn on the user's head, a large, bulky, unbalanced and / or heavy display device would be cumbersome and may be uncomfortable for the user to wear.

[0005] Projector-based displays provide images in an angular domain that can be viewed directly by the user's eye without an intermediate screen or display panel. Pupil replica waveguides are used to deliver the images in the angular domain to the user's eye. The lack of a screen or display panel in a scanning projector display allows the size and weight of the display to be reduced.

[0006] Ideally, the pupil replicating waveguide provides sufficient directionality to ensure that the displayed image can only be seen by the wearer of the display and not by external observers. However, in many current pupil replicating waveguides, a small but significant amount of display light leaks out of the display, allowing external observers to see some of the displayed image and obstructing eye contact with the wearer of the display. SUMMARY OF THE INVENTION

[0008] According to one aspect of the invention, there is provided a pupil replicating waveguide comprising a slab of transparent material for propagating display light therein by total internal reflection. A diffraction grating is supported by the slab. The diffraction grating comprises a plurality of stripes formed of a twisted nematic (TN) liquid crystal (LC) material in a polymer substrate. The stripes are tilted for out-coupling display light from the slab by diffraction into a blazed diffraction order. A larger portion of the display light is out-coupled into the blazed diffraction order, while a smaller portion of the display light is out-coupled into a non-blazed diffraction order. The TN LC material has an ordinary refractive index n for light polarized perpendicular to the molecules of the TN LC material. O , has an extraordinary refractive index for light polarized parallel to the molecules of the TN LC material E The refractive index contrast of the polarized display light incident on the diffraction grating has a refractive index contrast distribution along the thickness direction of the diffraction grating. The refractive index contrast is greater in the middle of the refractive index contrast distribution than on both sides of the refractive index contrast distribution, thereby reducing the portion of the incident polarized display light that is outcoupled into the non-blazed diffraction order.

[0009] In some embodiments, the refractive index of the polymer substrate material is closer to n O Rather than being closer to n E , whereby the refractive index contrast is greater in the middle of the refractive index contrast profile than on either side of the refractive index contrast profile. The refractive index contrast profile may be symmetrical along the thickness direction of the diffraction grating and may be substantially zero on either side. The refractive index contrast profile may be a smoothly varying function, such as a Gaussian function. The TN LC material may be polymer stabilized. In some embodiments, the pupil replica waveguide further comprises an input grating for in-coupling display light into the plate.

[0010] According to another aspect of the present invention, a method for manufacturing a pupil replicating waveguide is provided. The method includes forming a plurality of inclined stripes on a transparent material plate for coupling display light from the plate outwardly into a blazed diffraction order by diffraction, the inclined stripes having a first refractive index n1. A conforming layer may be formed on the plurality of inclined stripes and the plate. The conforming layer forms gaps between the inclined stripes covered by the conforming layer. The conforming layer has a second refractive index n2. An outer coating is formed on the conforming layer, the outer coating filling the gaps between the inclined stripes covered by the conforming layer and having a third refractive index n3, wherein n1>n2>n3 or n1>n2>n3 ... <n2<n3。

[0011] According to a further aspect of the present invention, there is also provided a pupil replication waveguide, which includes a flat plate of transparent material for propagating display light therein by total internal reflection. A diffraction grating is supported by the flat plate. The diffraction grating includes a plurality of tilted stripes for diffracting the display light from the flat plate outwards into a blazing diffraction order, and the tilted stripes have a first refractive index n1. A uniform layer is provided on the plurality of tilted stripes and the flat plate, and the uniform layer forms gaps between the tilted stripes covered by the uniform layer. The uniform layer has a second refractive index n2. An outer coating is formed on the uniform layer, and the outer coating is disposed in the gaps between the tilted stripes covered by the uniform layer and has a third refractive index n3, where n1 > n2 > n3 or n1 < n2 < n3. The effective refractive index contrast distribution of the diffraction grating along the thickness direction of the diffraction grating may be symmetric, and the refractive index contrast may be greater in the middle of the refractive index contrast distribution than on both sides of the refractive index contrast distribution.

[0012] In some embodiments of the method and apparatus, the plurality of tilted stripes are formed by imprinting or etching. The uniform layer may be formed by atomic layer deposition (ALD). The outer coating may be formed by spin coating.

[0013] It should be understood that any feature discussed as being suitable for inclusion in any aspect described herein is also suitable for inclusion in any other aspect in any combination. Brief Description of the Drawings

[0015] Exemplary embodiments will now be described in conjunction with the drawings, where:

[0016] Figure 1 is a side cross-sectional view of the pupil replication waveguide;

[0017] Figure 2 is Figure 1 an enlarged cross-sectional view of the pupil replication waveguide of

[0018] Figure 3A showing the diffraction of display light into the blazing diffraction order and the non-blazing diffraction order;

[0019] Figure 3B is Figure 3A a graph of the diffraction efficiency of display light relative to the incident angle into the blazing diffraction order at the diffraction grating of

[0020] Figure 3C is Figure 3A a graph of the diffraction efficiency of display light relative to the incident angle into the non-blazing diffraction order at the diffraction grating of

[0021] Figure 4Ais a dielectric constant plot of a diffraction grating of a pupil replica waveguide comprising a stack of three layers with different refractive index contrasts;

[0022] Figure 4B is Figure 4A A graph of diffraction efficiency of display light into blazed diffraction orders relative to incident angle at a diffraction grating of;

[0023] Figure 4C is Figure 4A A graph of diffraction efficiency of display light into non-blazed diffraction orders relative to the incident angle at a diffraction grating of;

[0024] Figure 5A is a dielectric constant plot of a diffraction grating of a pupil replica waveguide comprising a stack of three layers having different refractive index contrasts and variable refractive index tilted fringes extending through all three layers;

[0025] Figure 5B is Figure 5A A graph of diffraction efficiency of display light into blazed diffraction orders relative to incident angle at a diffraction grating of;

[0026] Figure 5C is Figure 5A A graph of diffraction efficiency of display light into non-blazed diffraction orders relative to the incident angle at a diffraction grating of;

[0027] Fig. 6A is a dielectric constant plot of a diffraction grating of a pupil replica waveguide comprising a stack of three layers having different refractive index contrasts and high refractive index slanted fringes extending through all three layers;

[0028] Figure 6B is Fig. 6A A graph of diffraction efficiency of display light into blazed diffraction orders relative to incident angle at a diffraction grating of;

[0029] Figure 6C is Fig. 6A A graph of diffraction efficiency of display light into non-blazed diffraction orders relative to the incident angle at a diffraction grating of;

[0030] Fig. 7A is a refractive index map of a diffraction grating of a pupil replica waveguide, the diffraction grating comprising inclined fringes with a gradient of refractive index;

[0031] Figure 7B is a refractive index map of a diffraction grating of a pupil replicating waveguide, the diffraction grating comprising a substrate having a graded refractive index;

[0032] Fig. 8A is the refractive index map of the Bragg grating of the pupil replica waveguide;

[0033] Figure 8B is Fig. 8A A graph of diffraction efficiency of display light into blazed diffraction orders relative to the incident angle at a Bragg grating of FIG.

[0034] Figure 8C is Fig. 8A A graph of diffraction efficiency of display light into non-blazed diffraction orders relative to the incident angle at a Bragg grating of FIG.

[0035] Fig. 9A is a dielectric constant diagram of a Bragg grating of a pupil replica waveguide, the Bragg grating having a plurality of areas with different refractive index contrasts;

[0036] Fig. 9B is Fig. 9A A graph of diffraction efficiency of display light into blazed diffraction orders relative to incident angle at a diffraction grating of;

[0037] Fig. 9C is Fig. 9A A graph of diffraction efficiency of display light into non-blazed diffraction orders relative to the incident angle at a diffraction grating of;

[0038] Fig.10 is a flow chart of a method of manufacturing a pupil replicating waveguide comprising several grating layers having different refractive index contrasts;

[0039] Fig.11 is a flow chart of a method of making a pupil replicating waveguide including a diffraction grating having a smoothly varying refractive index contrast;

[0040] Fig.12 is a cross-sectional view of a diffraction grating for a pupil replicating waveguide, the diffraction grating having a uniform layer;

[0041] Fig.13 Is manufacturing Fig.12 A flow chart of a method for producing a diffraction grating;

[0042] Fig.14 is a cross-sectional view of a diffraction grating for a pupil replicating waveguide, the diffraction grating comprising fringes formed of twisted nematic (TN) liquid crystal;

[0043] Fig.15 is a top cross-sectional view of a near-eye display having a glasses form factor;

[0044] Fig.16A is an isometric view of a head mounted display of the present invention; and

[0045] Fig. 16B Yes Fig.16A Block diagram of a virtual reality system with a head mounted device.

[0046] Detailed Description

[0047] Although this teaching is described in conjunction with various embodiments and examples, it is not intended that this teaching be limited to such embodiments. On the contrary, this teaching includes various substitutions and equivalents, as understood by those skilled in the art. All statements describing the principles, aspects and embodiments of the present invention and its specific examples herein are intended to include their structural and functional equivalents. In addition, it is intended that such equivalents include both currently known equivalents and equivalents developed in the future, that is, any element developed to perform the same function, without considering structure.

[0048] As used herein, unless explicitly stated, the terms "first", "second", etc. are not intended to imply a sequential order, but rather are intended to distinguish one element from another. Similarly, unless explicitly stated, the sequential order of method steps does not imply a sequential order in which they are performed.

[0049] Light leakage outside of a near-eye display based on a projector and a pupil replica waveguide may be caused by diffraction of the display light at the diffraction grating of the pupil replica waveguide in an undesired direction, i.e., outside the display toward the outside world, rather than inside the display toward the user's eyes. For blazed diffraction gratings, i.e., gratings with grooves or stripes that are tilted to more efficiently diffract incident light into one diffraction order (e.g., the first diffraction order) rather than into the opposite diffraction order (e.g., the negative first diffraction order), some light may still leak in the direction of the non-blazed diffraction order (i.e., outside the display). The leaked display light may be distracting to a person interacting with the wearer of the near-eye display, and may enable other observers to see the displayed content (text, images, etc.), potentially causing privacy issues.

[0050] According to the present invention, the diffraction grating of the pupil replica waveguide can be configured to reduce diffraction in unwanted directions, i.e., to reduce diffraction into non-blazed diffraction orders. To this end, the refractive index contrast distribution of the diffraction grating in the thickness direction of the diffraction grating (i.e., across the thickness of the diffraction grating) can be reduced at the ends of the diffraction grating, i.e.: the refractive index contrast at the top and bottom surfaces of the diffraction grating can be reduced compared to the refractive index contrast at the middle thickness of the diffraction grating. This apodization of the refractive index contrast can suppress the diffraction of light into unwanted or non-blazed diffraction orders. Herein, the refractive index contrast is defined as the difference between the refractive index of the diffraction grating fringes and the refractive index of the underlying substrate in which the fringes are suspended.

[0051] Refractive index contrast apodization can be achieved in a variety of ways. In some embodiments, the diffraction grating can be layered, with each layer having its own refractive index contrast. In some embodiments, smoother variations can be produced by treatment of the diffraction grating layer materials (i.e., controlled baking). In some embodiments, the duty cycle or fill factor of the diffraction grating can be varied through the thickness of the diffraction grating by tapering or otherwise shaping the diffraction grating grooves or stripes. These and other embodiments will be further considered in more detail below.

[0052] refer to Figure 1 , pupil replication waveguide 100 includes a slab 102 of transparent material for propagating display light 104 in the slab 102 by sequential total internal reflection (TIR) ​​from the top and bottom parallel surfaces of the slab 102. As used herein, the term "transparent" includes both fully transparent and partially transparent or translucent, i.e., somewhat absorbing or scattering, but transparent enough to transmit a sufficient amount of display light to the user's eyes so that the user can see the displayed image. The slab 102 is typically plano-parallel, although a slight curvature of the slab may be acceptable in some cases.

[0053] Diffraction grating 106 is supported by plate 102. Diffraction grating 106 includes a plurality of fringes 108 in substrate 110. The refractive index of fringes 108 is different from the refractive index of substrate 110. The refractive index of fringes 108 may be greater than or less than the refractive index of substrate 110. Refractive index contrast is defined herein as the modulus of the difference between the refractive index of fringes 108 and the refractive index of substrate 110. Figure 1 As shown, the stripes 108 are tilted for coupling a larger portion 114 of the display light 104 outwardly from the flat panel 102 so that the display light 104 is observed by the user's eye 112. Typically, the larger portion 114 is about 10% to 50% of the display light 104 in optical power level. A smaller portion 116 of the display light 104 is coupled outwardly in the "wrong" direction, i.e., coupled outside the near-eye display, and may be observed by others. As described above, it is desirable to reduce the smaller portion 116. In some embodiments, the smaller portion 116 can be reduced to at least 0.1% of the optical power level of the display light 104. An input coupler (e.g., an input diffraction grating) can be provided in the pupil replica waveguide 100 for coupling the display light 104 into the flat panel 102.

[0054] refer to Figure 2, showing in more detail the diffraction of display light 104 on diffraction grating 106. The fringes 108 of the diffraction grating 106 are angled or slanted toward the incident display light 104 to diffract a larger portion 114 of the display light 104 into a blazed diffraction order 124. A smaller portion 116 of the display light 104 is diffracted into a non-blazed diffraction order 126.

[0055] refer to Figure 3A , pupil replica waveguide (e.g. Figure 1 The relative dielectric constant ε of the diffraction grating 300 of the pupil replica waveguide 100 is plotted in microns according to the x-coordinate and the z-coordinate. The x-coordinate is the lateral coordinate of the specific position in the diffraction grating 300 along the surface of the diffraction grating 300, and the z-coordinate is the thickness coordinate of the specific position in the diffraction grating 300, that is, the coordinate in the thickness direction 340 of the diffraction grating 300. The diffraction grating 300 includes a plurality of inclined stripes 308 of a high dielectric constant (equal to 4.0 in this example) suspended in a substrate material 310 of a low dielectric constant of 3.24. In this article, the terms "high" and "low" are relative to each other, that is, the stripe dielectric constant is higher than the substrate dielectric constant. In some embodiments, the dielectric constant of the stripes 308 is lower than the dielectric constant of the substrate 310. For non-magnetic, non-absorbing media, the relative dielectric constant ε r The relationship between the refractive index n and r =n 2 Therefore, the inclined stripes 308 have a refractive index n F =2, and the base material 310 has a refractive index n S =1.8. In this case, the refractive index contrast Δn=|n F -n S | is equal to 0.2. The inclined stripes 308 may be photolithographically formed on a transparent plate (not shown), and the base material 310 may be applied onto the inclined stripes 308, for example, by spin coating.

[0056] Figure 3B Shows Figure 3A 300 with respect to the incident angle. Vertical line 302 represents the angle range over which the display light is guided by the waveguide slab (not shown) supporting the diffraction grating 300. In this example, the blazed diffraction order diffraction efficiency 314 reaches about 28%. In contrast, Figure 3C The calculated non-blazed diffraction order diffraction efficiency 316 shown only reaches about 0.6% ( Figure 3B and 3C). While this may not seem like much compared to the blazed diffraction order efficiency 314, 0.6% of the incident display light may become quite noticeable to an external observer of a near-eye display with such a waveguide, and may appear distracting or annoying to the external observer, and may hinder or even completely prevent eye contact with the display wearer.

[0057] Reference now Figure 4A , pupil replica waveguide (e.g. Figure 1 The relative dielectric constant of the diffraction grating 400 of the pupil replica waveguide 100 is plotted in micrometers based on the x-coordinate and the z-coordinate. The x-coordinate is the lateral coordinate of a specific position in the diffraction grating 400, and the z-coordinate is the thickness coordinate of the specific position in the diffraction grating 400. Figure 4A As shown, the diffraction grating 400 includes a stack of a first grating layer 421, a second grating layer 422, and a third grating layer 423. The second grating layer 422 is disposed in the middle, i.e., between the first grating layer 421 and the third grating layer 423. The first grating layer 421 and the third grating layer 423 have substantially the same thickness. In this document and throughout the rest of the specification, specifically, when applied to a parameter, the term "substantially" means within 10% of the median value of the parameter.

[0058] The second grating layer 422 is thicker than any of the first grating layer 421 and the third grating layer 423, specifically, about twice as thick in this example. In other words, the thickness of the second grating layer 422 is substantially equal to the total thickness of the first grating layer 421 and the third grating layer 423. For example, in some embodiments, the thickness of the first grating layer 421 and the third grating layer 423 may be between 75 nm and 85 nm, and the thickness of the second grating layer 422 may be between 150 nm and 170 nm.

[0059] A plurality of inclined fringes 408 extend through the first grating layer 421, the second grating layer 422, and the third grating layer 423. The relative permittivity of the inclined fringes 408 may vary from layer to layer. The inclined fringes 408 are suspended in a base material 410, the relative permittivity of the base material 410 also varies from layer to layer and is lower than the relative permittivity of the fringes 408. For each layer 421, 422, and 423 of the diffraction grating 400, the refractive index of the base material 410 is lower than the refractive index of the fringes 408.

[0060] The fringes 408 of the diffraction grating 400 have a refractive index n of 1.95 in the first grating layer 421 and the third grating layer 423. F , has a refractive index n of 2.0 in the second grating layer 422 FThe base material 410 has a refractive index n of 1.85 in the first grating layer 421 and the third grating layer 423. S , having a refractive index n of 1.8 in the second grating layer 422 S Therefore, the refractive index contrast Δn of each of the first grating layer 421, the second grating layer 422, and the third grating layer 423 is equal to |n F -n S Although constant on each grating layer 421, 422, 423, it varies from layer to layer: for the first grating layer 421 and the third grating layer 423, the refractive index contrast Δn is equal to 0.1, and for the second grating layer 422, the refractive index contrast Δn is equal to 0.2, that is, the refractive index contrast of the second grating layer 422 is higher than the refractive index contrast of the first grating layer 421 and the third grating layer 423. Along the thickness direction 440 (i.e., the z-axis) of the diffraction grating 400, the refractive index contrast distribution of the diffraction grating 400 is symmetrical, so that the refractive index contrast Δn is larger in the middle of the refractive index contrast distribution than on both sides of the refractive index contrast distribution. Note that the refractive index values ​​used herein are intended to be examples only; the refractive index values ​​and refractive index contrast values ​​may differ depending on the material used. It should also be understood that the statements of refractive index values ​​for the examples considered herein imply a certain tolerance range, for example a refractive index of 2.0 means a range from 1.95 to 2.05, a refractive index of 1.8 means a range from 1.75 to 1.85, and so on.

[0061] refer to Figure 4B , the calculated diffraction efficiency of the blazed diffraction order 414 reaches about 18%, which is slightly higher than that used as a reference Figure 3A The blazed diffraction order diffraction efficiency 314 of the diffraction grating 300 ( Figure 3B ). Figure 3B The lower value of the maximum diffraction efficiency may be caused by the lower total refractive index contrast Δn compared to the maximum diffraction efficiency of 400, because only the middle second layer 422 has a higher refractive index contrast Δn of 0.2, while the remaining first layer 421 and third layer 423 have a lower refractive index contrast Δn of 0.1. It is worth noting that in the angular range ( Figure 4B , 4C ), the maximum diffraction efficiency 416 diffracted into the non-blazed diffraction order is more significantly reduced to below 0.1%, i.e., reduced by about 5 / 6, and the angular range of the waveguide 400 represents the angular range of TIR guided light. Therefore, Figure 4A The apodization of the z-profile of the refractive index contrast Δn of the diffraction grating 400 will show the portion of light that is outcoupled into the non-blazed diffraction order 416 ( Figure 4C) is reduced to a higher degree than the refractive index contrast of the blazed portion 414. Herein and throughout the specification, the term "apodization" with respect to refractive index contrast refers to the reduction of the refractive index contrast at the top and bottom surfaces of the diffraction grating 400 so as to smoothly transition to zero refractive index contrast outside the diffraction grating 400 (i.e., above or below the diffraction grating 400), such as Figure 4A shown.

[0062] Go to Figure 5A , pupil replica waveguide (e.g. Figure 1 The relative dielectric constant of the diffraction grating 500 of the pupil replica waveguide 100 is plotted in micrometers according to the x-coordinate and the z-coordinate. The diffraction grating 500 includes a stack of a first grating layer 521, a second grating layer 522, and a third grating layer 523. The second grating layer 522 is disposed in the middle, i.e., between the first grating layer 521 and the second grating layer 523. The first grating layer 521 and the third grating layer 523 have substantially the same thickness, and the second grating layer 522 is thicker, for example, twice as thick as each of the first grating layer 521 and the third grating layer 523. As a non-limiting example, the thickness of the first grating layer 521 and the third grating layer 523 may be between 75 nm and 85 nm, and the thickness of the second grating layer 522 may be between 150 nm and 170 nm.

[0063] A plurality of inclined stripes 508 extend through the first grating layer 521, the second grating layer 522, and the third grating layer 523. The relative dielectric constant ε of the inclined stripes 508 is F and the corresponding refractive index n F The refractive index n of the substrate 510 varies from layer to layer and is larger in the second grating layer 522. The fringes 508 are suspended in or supported by the substrate 510. For the first grating layer 521, the second grating layer 522, and the third grating layer 523, the refractive index n of the substrate 510 is S is at the same constant value of 1.8. Because the refractive index n of the substrate 510 in the second grating layer 522 F Different from the refractive index of the fringes in the first grating layer 521 and the third grating layer 523, the refractive index contrast Δn of each of the first grating layer 521, the second grating layer 522 and the third grating layer 523 is equal to |n F -n S Although constant on each grating layer, it varies from layer to layer: for the first grating layer 521 and the third grating layer 523, the refractive index contrast Δn is equal to 0.1, and for the second grating layer, the refractive index contrast Δn is equal to 0.2. Along the thickness direction 540 of the diffraction grating (i.e., the z-axis), the refractive index contrast distribution of the diffraction grating 500 is approximately symmetrical, so that the refractive index contrast Δn is larger in the middle of the refractive index contrast distribution than on both sides of the refractive index contrast distribution. Note that although Figure 5A The diffraction grating 500 is structurally different from Figure 4A diffraction grating 400, but the refractive index contrast distributions of the two gratings are basically the same.

[0064] Figure 5B Shown by Figure 5A The calculated diffraction efficiency 514 of the display light diffracted by the diffraction grating 500 into the blazed diffraction order. The maximum diffraction efficiency is about 15%, which is about Figure 3A The diffraction efficiency 314 of the blazed diffraction order of the diffraction grating 300 is half. Figure 5C The calculated diffraction efficiency 516 of the display light diffracted into the non-blazed diffraction order is shown. The maximum diffraction efficiency 516 of the non-blazed diffraction order is within the angular range of the waveguide 500 outlined by the boundary line 502 ( Figure 5B , 5C ) is significantly reduced to a value below 0.1%, and the angular range of the waveguide 500 represents the angular range of the guided light. Therefore, similar to Figure 4A The diffraction grating 400, Figure 5A The apodization of the z-profile of the refractive index contrast Δn of the diffraction grating 500 also reduces the portion of the display light that is outcoupled into the non-blazed diffraction order 516 ( Figure 5C ).

[0065] Go to Fig. 6A , pupil replica waveguide (e.g. Figure 1 The relative dielectric constant of the diffraction grating 600 of the pupil replica waveguide 100 is plotted in micrometers according to the x-coordinate and the z-coordinate. The diffraction grating 600 includes a stack of a first grating layer 621, a second grating layer 622, and a third grating layer 623. The second grating layer 622 is disposed in the middle, i.e., between the first grating layer 621 and the second grating layer 623. The first grating layer 621 and the third grating layer 623 have substantially the same thickness, while the second grating layer 622 is thicker, for example, twice as thick as each of the first grating layer 621 and the third grating layer 623. For example, the thickness of the first grating layer 621 and the third grating layer 623 may be between 75 nm and 85 nm, while the thickness of the second grating layer 622 may be between 150 nm and 170 nm.

[0066] A plurality of inclined stripes 608 extend through the first grating layer 621, the second grating layer 622, and the third grating layer 623. For each grating layer 621, 622, and 623, the relative dielectric constant ε of the inclined stripes 608 is F and the corresponding refractive index n F is the same; in this example, for all three layers, the refractive index n of the inclined fringes 608 is F Equal to 1.9.

[0067] The inclined stripes 608 are suspended in a substrate 610. The refractive index of the substrate 610 material is n S In the first grating layer 621 and the third grating layer 623, the refractive index n of the substrate 610 is S =1.8; and in the second grating layer 622, the refractive index n of the substrate 610 is S is lower, equal to 1.7. Therefore, the refractive index contrast Δn of each of the first grating layer 621, the second grating layer 622 and the third grating layer 623 is equal to 1.7. F -n S | Varies by layer: The refractive index contrast Δn of the first grating layer 621 and the third grating layer 623 is equal to 0.1, while the refractive index contrast Δn of the second grating layer 622 is equal to 0.2. Along the thickness direction 640 of the diffraction grating (i.e., the z-axis), the refractive index contrast distribution of the diffraction grating 600 can be symmetrical, so that the refractive index contrast Δn is larger in the middle of the refractive index contrast distribution than on both sides of the refractive index contrast distribution. Note that the refractive index contrast distribution is different from Figure 4A The diffraction grating 400 and Figure 5A The diffraction grating 500 is the same.

[0068] Figure 6B Shown by Fig. 6A The calculated diffraction efficiency 614 of the display light diffracted by the diffraction grating 600 into the blazed diffraction order. The maximum diffraction efficiency is about 18%, which exceeds the reference used herein. Figure 3A The diffraction efficiency 314 of the blazed diffraction order of the diffraction grating 300 is half. Figure 6C , the maximum diffraction efficiency of the non-blazed diffraction order 616 is within the angular range of the waveguide 600 outlined by the boundary line 602 ( Figure 6B , 6C ) also significantly decreased to a value below 0.1%. Fig. 6A The apodization of the z-profile of the refractive index contrast Δn of the diffraction grating 600 will show the portion of light that is outcoupled into the non-blazed diffraction order 616 ( Figure 6C ) is reduced to a much greater extent than the portion of the display light that is outcoupled into the blazed diffraction order.

[0069] exist Figure 4A Diffraction grating 400, Figure 5A The diffraction grating 500 and Fig. 6AIn the example of the diffraction grating 600 of , the central (second) grating layer is twice as thick as the outer (first and third) grating layers, and the refractive index contrast of the central grating layer is twice as high. Other configurations are possible for the diffraction grating described above. As a non-limiting example, the thicknesses of all three grating layers can be made substantially equal to each other, and the refractive index contrast of the central grating layer can be high, for example, about three times as high as the refractive index contrast of the outer grating layers. Furthermore, the thicknesses of the outer grating layers need not be the same, and the number of layers can be greater than three. In some embodiments, the layer structure is symmetrical about the central thickness of the diffraction grating; in other embodiments, it is quasi-symmetrical or even asymmetrical. In general, the apodization can approximate a smoothly varying bell-shaped function, such as, for example, a Gaussian function.

[0070] refer to Fig. 7A , for pupil replication waveguides (e.g. Figure 1 The diffraction grating 700A of the pupil replica waveguide 100 of the present invention includes a plurality of high refractive index inclined stripes 708A suspended in a low refractive index substrate material 710A. In this article, the terms "high" and "low" are relative to each other, that is, the stripe refractive index is higher than the substrate refractive index. The stripe 708A has a refractive index that varies smoothly in the thickness direction 740. The refractive index at the midpoint 741 of the thickness is higher than the refractive index at the top and bottom surfaces of the diffraction grating 700A. As a non-limiting example, the maximum refractive index of the stripe 708A at the midpoint 741 is 2.0, while the refractive index at the top and bottom surfaces is 1.8. In this example, the refractive index of the substrate 710A is uniformly 1.8. Therefore, the refractive index contrast distribution of the diffraction grating 700A has a bell-shaped shape with a maximum value of 0.2 and a minimum value of 0. This configuration provides a smooth apodization of the refractive index contrast distribution, which can significantly reduce the portion of the display light that is outcoupled into undesired non-blazed diffraction orders.

[0071] refer to Figure 7B , for pupil replication waveguides (e.g. Figure 1 The diffraction grating 700B of the pupil replica waveguide 100) includes a plurality of high refractive index inclined stripes 708B suspended in a low refractive index base material 710B. As in the above example, the terms "high" and "low" are relative to each other, i.e., the stripe refractive index is higher than the base refractive index. In this example, the stripes 708B have a constant refractive index of 2.0. The refractive index of the base material 710B varies smoothly in the thickness direction 740. The refractive index of the base material 710B is lower at the midpoint 741 of the thickness than at the top and bottom surfaces of the diffraction grating 700B. The minimum refractive index at the midpoint 741 is 1.8, while the refractive index at the top and bottom surfaces is 2.0. Therefore, Figure 7B The refractive index contrast distribution of the diffraction grating 700B has Fig. 7AThe diffraction grating 700A has the same or similar bell shape, with a maximum value of 0.2 at the midpoint 741 and a minimum value of 0 at the outer surface of the diffraction grating 700B.

[0072] Reference now Fig. 8A , for pupil replication waveguides (e.g. Figure 1 The Bragg grating 800 of the pupil replication waveguide 100 includes a plurality of inclined sinusoidal fringes 808 with a refractive index varying from 1.8 to 2.0. As used herein, the term "sinusoidal fringes" refers to diffraction grating fringes whose refractive index varies sinusoidally along a fringing direction 850 perpendicular to the fringes 808, for example with an amplitude of 0.2 (1.8 to 2.0) in this example. The refractive index contrast across the entire Bragg grating 800 is the same.

[0073] In some embodiments, the Bragg grating 800 can be formed by providing a dual-beam optical interference pattern in a photosensitive material that changes its refractive index when illuminated. Ultraviolet (UV) light can be used to form a dual-beam optical interference pattern in a UV-sensitive polymer or another material. The dual-beam interference pattern can be formed by directing two recording UV beams to a photosensitive substrate. The orientation of the recording beams can be selected so that as much light as possible is diffracted in the direction of the eyebox of the near-eye display. In some embodiments, multiple such exposures can be performed at different angles; for this case, the resulting fringe pattern can be non-sinusoidal and / or irregularly shaped to efficiently diffract the display light at multiple incident angles corresponding to multiple exposure angles.

[0074] Figure 8B It shows that the calculation Fig. 8A The result of the blazed diffraction order diffraction efficiency 814 at the diffraction grating 800 with respect to the incident angle. The vertical line 802 represents the display light being transmitted by the waveguide slab (e.g. Figure 1 The angle range of the pupil replica waveguide 100 is guided by the plate 102). In this example, Figure 8B The blazed diffraction order diffraction efficiency 814 (ie, the diffraction efficiency to the viewing window of the near-eye display) reaches approximately 18%.

[0075] Figure 8C Shows the calculation Fig. 8A Result of the diffraction efficiency 816 of the non-blazed diffraction orders of the diffraction grating 800 with respect to the incident angle. Figure 8CAs shown, the calculated non-blazed diffraction order diffraction efficiency 816 only reaches about 0.4%. Although this does not seem to be much compared to the blazed diffraction order diffraction efficiency 814, 0.4% of the incident display light may become very noticeable to an external observer of a near-eye display using such a pupil replicating waveguide. Therefore, even in the case where the refractive index variation of the diffraction grating fringes is smooth (e.g., sinusoidal), the non-apodized refractive index contrast may cause significant leakage of display light outside the near-eye display.

[0076] Go to Fig. 9A , for pupil replication waveguides (e.g. Figure 1 The Bragg grating 900 of the pupil replica waveguide 100 of the present invention comprises a plurality of inclined sinusoidal fringes 908 extending through a stack of a first grating layer 921, a second grating layer 922, and a third grating layer 923. The relative dielectric constant of the diffraction grating 900 is plotted in micrometers as a function of the x-coordinate and the z-coordinate. The x-coordinate is the lateral coordinate of a particular position within the diffraction grating 900, and the z-coordinate is the thickness coordinate of a particular position within the diffraction grating 900. In other words, the z-coordinate is parallel to the thickness direction 940. The second grating layer 922 of the diffraction grating 900 is disposed in the middle, i.e., between the first grating layer 921 and the second grating layer 923 of the diffraction grating 900. The first grating layer 921 and the third grating layer 923 have the same thickness, while the second (middle) layer 922 is approximately twice as thick as each of the first grating layer 921 and the third grating layer 923. In this example, the thickness of the first grating layer 921 and the third grating layer 923 is between 75 nm and 85 nm, while the thickness of the second grating layer 922 is between 150 nm and 170 nm.

[0077] The amplitude of the sinusoidal variation of the refractive index in the fringe 908 (i.e., the refractive index contrast) is different in different grating layers. In the example shown, the refractive index contrast of the first grating layer 921 and the third grating layer 923 is 0.1, and its refractive index varies spatially from 1.85 to 1.95, while the refractive index contrast of the second grating layer 922 is 0.2, and its refractive index varies spatially from 1.8 to 2.00. Such a variation pattern can be obtained, for example, by stacking the first grating layer 921, the second grating layer 922, and the third grating layer 923 together (where the second grating layer 922 has a higher concentration of photosensitive material than the first grating layer 921 and the third grating layer 923), and irradiating the stack with two writing UV waves simultaneously to produce a writing UV interference pattern extending through all three grating layers. One can also use apodization to make the beam intensity strongest in the middle of the grating.

[0078] refer to Fig. 9B , the calculated diffraction efficiency of the blazed diffraction order 914 reaches about 17%, which is slightly lower than Fig. 8AThe blazed diffraction order diffraction efficiency 814 of the Bragg grating 800 ( Figure 8B ). The slightly lower value of the maximum diffraction efficiency may be caused by the lower total refractive index contrast Δn, because only the middle second layer 922 has a refractive index contrast Δn of 0.2, while the first grating layer 921 and the third grating layer 923 have a lower refractive index contrast Δn of 0.1. It is worth noting that the maximum diffraction efficiency 916 of the non-blazed diffraction order is within the angular range of the waveguide 900 outlined by the boundary line 902 ( Fig. 9B , 9C ) is even more significantly reduced to below 0.1%, i.e., reduced by at least 3 / 4, and the angular range of the waveguide 900 represents the angular range of the light guided by the pupil replica waveguide. Fig. 9A The apodization of the z-profile of the refractive index contrast Δn of the diffraction grating 900 will show the portion of light that is outcoupled into the non-blazed diffraction order 916 ( Fig. 9C ) is reduced to a higher degree than the refractive index contrast of the blazed portion 914. The behavior of the non-blazed diffraction efficiency 916 of the Bragg grating 900 is similar to Figure 4A The non-blazed diffraction efficiency 416 of the Bragg grating 400.

[0079] Reference now Fig.10 The method 1000 of manufacturing a pupil replicating waveguide includes forming a transparent material plate (e.g. Figure 1 A plurality of inclined stripes (e.g. Fig. 6A The inclined stripes 608 may be configured to couple display light from the flat panel outwardly into the blazed diffraction order by diffraction. For example, the inclined stripes may have an inclination angle selected to increase the amount of light diffracted into the blazed diffraction order, such as an inclination angle corresponding to specular reflection in the direction of the blazed diffraction order. A first substrate layer ( Fig.10 1004), for example, coating a portion of the stripe height on a flat plate between the inclined stripes to form a first grating layer 621 ( Fig. 6A ). The first substrate layer can then be coated, for example, between the inclined stripes ( Fig.10 1006) to a portion of the stripe height to form a second base layer, thereby forming a second grating layer 622 ( Fig. 6A ). Then, for example, a second substrate layer may be applied between the inclined stripes ( Fig.10 ; 1008) to at least the height of the stripes to form a third base layer, thereby forming a third grating layer 623 ( Fig. 6A). The first substrate layer, the second substrate layer and the third substrate layer together form a substrate 610. The refractive index contrast of the second grating layer 622 (i.e., the layer formed by the stripes 608 and the second substrate layer) is higher than the refractive index contrast of the first grating layer 621 (i.e., the layer formed by the stripes 608 and the first substrate layer). The refractive index contrast of the second grating layer is also higher than the refractive index contrast of the third grating layer (i.e., the layer formed by the inclined stripes and the third substrate layer).

[0080] A plurality of inclined stripes can be formed by a suitable deposition method, such as standard and / or selective atomic layer deposition (ALD), chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD) and / or physical vapor deposition (PVD) combined with plasma etching or vapor etching or wet etching or atomic layer etching (ALE). For example, mask directional etching can be performed after deposition. In some embodiments, the first substrate layer, the second substrate layer and the third substrate layer are formed by a spin coating process, in which a polymer material having a suitable refractive index is spin-coated onto each other to form a stack of different refractive indices. Intermediate etching or photolithographic exposure and development steps may be included to control the relative thickness in the z direction and the X and Y directions. Inkjet or flowable deposition processes may also be used for this purpose instead of spin coating.

[0081] refer to Fig.11 , a method 1100 of manufacturing a pupil replicating waveguide includes forming a transparent material plate (e.g. Figure 1 A plurality of inclined stripes are formed (1102) on the flat plate 102, for example Figure 7B The tilted stripes 708B may be configured to couple display light from the panel outwardly into the blaze diffraction order by diffraction. For example, the tilted stripes may have a tilt angle selected to increase the amount of light diffracted into the blaze diffraction order, such as a tilt angle corresponding to specular reflection in the direction of the blaze diffraction order. Figure 7B The base layer 710B) can then be formed on the plate between the stripes 708B ( Fig.11 The substrate layer 710B may then be baked (1106) to provide a spatial refractive index variation of the substrate layer 710B in a thickness direction 740 of the substrate layer, such that a refractive index contrast profile of the diffraction grating 700B formed by the stripes 708B and the substrate layer 710B is symmetrical along the thickness direction 740 of the diffraction grating 700B, and the refractive index contrast is greater in the middle 741 of the refractive index contrast profile than on the sides of the refractive index contrast profile.

[0082] Multiple inclined stripes can be formed by a suitable deposition method, such as atomic layer deposition (ALD), chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), and / or physical vapor deposition (PVD). For example, mask-directed etching can be performed after deposition. In some embodiments, the first substrate layer, the second substrate layer, and the third substrate layer are formed by a spin-coating process, where polymer materials with suitable refractive indices are spin-coated on top of each other. Inkjet or flowable deposition processes can also be used for this purpose.

[0083] Now turning to Fig.12 , the pupil replication waveguide 1200 includes a plurality of inclined stripes 1208 supported by a transparent material slab 1202, which is configured to guide display light in the slab 1202 by TIR. Similar to the pupil replication waveguide example considered above, the inclined stripes 1208 of the pupil replication waveguide 1200 are configured to diffractively couple the display light from the slab 102 out into the blazing diffraction order. The inclined stripes 1208 have a first refractive index n1.

[0084] The uniform layer 1209 covers the inclined stripes 1208 with a uniform thickness. In other words, the uniform layer 1209 replicates the shape of the inclined stripes 1208, encapsulating the individual inclined stripes 1208 while leaving gaps 1211 between the individual inclined stripes 1208, as shown. The uniform layer has a second refractive index n2.

[0085] The outer coating 1210 (e.g., a polymer layer) fills the gaps 1211 between the inclined stripes 1208 covered by the uniform layer 1209. The top surface of the outer coating 1210 can be flat. The outer coating 1210 has a third refractive index n3. In some embodiments, the first refractive index n1, the second refractive index n2, and the third refractive index n3 satisfy the condition n1 < n2 < n3. In Fig.12 the example shown, n1 = 1.7, n2 = 1.8, and n3 = 1.9.

[0086] In fact, the inclined stripes 1208, the uniform layer 1209, and the outer coating 1210 form three grating layers in the pupil replication waveguide 1200: the first grating layer 1221, the second grating layer 1222, and the third grating layer 1223 ( Fig.12). The first grating layer 1221 has a refractive index varying from n1 to n2 (i.e., from 1.7 to 1.8 in this example). Therefore, the effective refractive index contrast Δn of the first grating layer 1221 is equal to 0.1. The second grating layer 1222 has a refractive index varying from n1 to n2 to n3 (i.e., from 1.7 to 1.8 to 1.9 in this example). Therefore, the effective refractive index contrast Δn of the second grating layer 1222 is equal to 0.2. Finally, the third grating layer 1223 has a refractive index varying from n2 to n3 (i.e., from 1.8 to 1.9 in this example). Therefore, the effective refractive index contrast Δn of the third grating layer 1223 is equal to 0.1. Therefore, this configuration also provides apodization refractive index contrast similar to the diffraction grating considered above, i.e., 0.1–0.2–0.1.

[0087] Go to Fig.13 And further reference Fig.12 , fabricating pupil replica waveguides (such as Fig.12 A method 1300 for forming a pupil replica waveguide 1200 includes forming (1302) a plurality of tilted stripes 1208 on a plate 1202 for coupling display light from the plate 1202 outwardly into a blazed diffraction order by diffraction, the tilted stripes having a first refractive index n1. Then, a uniform layer 1209 having a refractive index n2 is formed (1304) on the plurality of tilted stripes 1208, leaving gaps 1211 between the tilted stripes 1208. Then, an outer coating 1210 having a refractive index n3 may be formed (1306) on the uniform layer 1209. Fig.12 As shown, the outer coating 1210 fills the gaps 1211 between the inclined stripes 1208 covered by the uniform layer 1209. The refractive indices of the inclined stripes 1208, the uniform layer 1209 and the outer coating 1210 may satisfy the condition n1>n2>n3, or alternatively, n1 <n2<n3。

[0088] A variety of manufacturing methods can be used to manufacture the inclined stripes 1208, the uniform layer 1209 and the outer coating 1210. In some embodiments, the plurality of inclined stripes 1208 are formed by imprinting using a mold and a suitable resin, or by anisotropic etching through a mask defined by photolithography. The uniform layer 1209 can be formed by atomic layer deposition, which enables the deposition of a conforming film with a well-defined uniform thickness. The outer coating 1210 can be formed, for example, by spin coating, which fills the gaps 1211 and results in good uniformity of the upper surface of the spin-coated outer coating.

[0089] refer to Fig.14, pupil replica waveguide 1400 includes a slab 1402 of transparent material for propagating display light in the slab 1402 by total internal reflection (TIR) ​​from the top and bottom surfaces of the slab 1402. A diffraction grating 1450 is supported by the slab 1402. The diffraction grating 1450 includes a plurality of fringes 1408 suspended in a base material 1410 (e.g., a polymer base). The fringes 1408 are formed of a twisted nematic (TN) liquid crystal (LC) material. In some embodiments, the LC molecules 1418 are stabilized by the polymer base material. The fringes 1408 are tilted for out-coupling display light 1404 from the slab 1402 into a blazed diffraction order 1424 by diffraction. Due to the tilt of the fringes 1408, a larger portion 1414 of the display light 1404 is out-coupled into the blazed diffraction order 1424, while a smaller portion 1416 of the display light 1404 is out-coupled into the non-blazed diffraction order 1426.

[0090] The TN LC material has an ordinary refractive index n for light polarized perpendicular to the elongated LC molecules 1418 of the TN LC material. O , while for light polarized parallel to the molecules 1418 of the TN LC material has an extraordinary refractive index n E In some embodiments, the refractive index of the polymer substrate material 1410 is closer to n O Rather than being closer to n E For these embodiments, in the incident plane (i.e., in Fig.14 The refractive index contrast of the incident display light 1404 polarized in the plane of the diffraction grating 1450 has a different refractive index contrast distribution along the thickness direction 1440 of the diffraction grating 1450. This happens because Fig.14 In the TN configuration of the LC material shown, the top and bottom LC molecules 1418A are arranged perpendicular to the polarization direction 1405 of the incident display light 1404, and thus have an ordinary refractive index n for the incident display light 1404. O , while the LC molecules 1418B of the intermediate thickness are at an acute angle relative to the polarization direction 1405, thus having n O and n E The refractive index is usually higher than the ordinary refractive index n O . Therefore, the refractive index contrast is greater in the middle of the refractive index contrast profile than on the sides of the refractive index contrast profile, which reduces the portion of polarized display light that is outcoupled into the non-blazed diffraction order 1426. The refractive index contrast profile is generally a smoothly varying function due to the smoothly varying twist angle of the TN LC molecules 1418. By choosing an appropriate LC molecule orientation geometry, the smoothly varying function can be approximated to a Gaussian function.

[0091] refer to Fig.15, the near-eye display 1500 includes a frame 1501 having the form factor of a pair of glasses. For each eye, the frame 1501 supports: a light source subassembly 1502, an electronic driver 1504 (which is operably coupled to the light source subassembly 1502 for powering an emitter of the light source subassembly 1502 to provide a plurality of light beams), a collimator 1506 (which is optically coupled to the light source subassembly 1502 for collimating the plurality of light beams), a scanner 1508 (which is optically coupled to the collimator 1506 for scanning the plurality of light beams), and a pupil replicator 1510 optically coupled to the scanner 1508. The light source subassembly 1502 may include a substrate supporting an array of single-mode or multi-mode semiconductor light sources (e.g., side-emitting laser diodes, vertical-cavity surface-emitting laser diodes, SLEDs, or light-emitting diodes) for providing the plurality of light beams. The collimator 1506 may include a concave mirror, a bulk lens, a Fresnel lens, a holographic lens, etc., and may be integrated with the light source subassembly 1502. Scanner 1508 may include, for example, a 2D micro-electromechanical system (MEMS) scanner.

[0092] The function of pupil replicator 1510 is to provide multiple laterally offset copies of the light beam scanned by scanner 1508 to cover the entire area of ​​​​viewing window 1512. Viewing window 1512 represents the geometric area for placing the user's eyes when the user wears near-eye display 1500. When the user's eyes are located in the area outlined by viewing window 1512, an image of acceptable quality can be displayed to the user. Multiple laterally offset copies of the light beam are provided by pupil replicator 1510 to ensure that the area of ​​​​viewing window 1512 is wide enough for different users to observe the displayed image. Pupil replicator 1510 can include any pupil replica waveguide described herein (e.g., Figure 1 A pupil replica waveguide 100) comprising Figure 4A Diffraction grating 400, Figure 5A Diffraction grating 500, Fig. 6A Diffraction grating 600, Fig. 7A Diffraction grating 700A, Figure 7B Diffraction grating 700B, Fig. 9A The diffraction grating 900 and / or Fig.15 The pupil replicator 1510 may also include a diffraction grating 1550. Fig.12 Pupil replication waveguide 1200, Fig.14 Pupil replication waveguide 1400, etc.

[0093] Controller 1505( Fig.15) is operably coupled to the scanner 1508 and the electronic driver 1504. The controller 1505 can be configured to determine the X tilt angle and the Y tilt angle of the tiltable MEMS reflector of the scanner 1508. The controller 1505 then determines which pixel or pixels of the image to be displayed corresponds to the determined X tilt angle and Y tilt angle. The controller 1505 then determines the brightness and / or color of these pixels and operates the electronic driver 1504 accordingly to provide power electrical pulses to the light source subassembly 1502 to generate light pulses at a power level corresponding to the determined pixel brightness and color.

[0094] Embodiments of the present invention may include an artificial reality system or be implemented in conjunction with an artificial reality system. The artificial reality system adjusts the sensory information about the outside world obtained through the senses in some way before the sensory information is presented to the user (e.g., visual information, audio, tactile (somatic) information, acceleration, balance, etc.). As a non-limiting example, artificial reality may include virtual reality (VR), augmented reality (AR), mixed reality (MR), mixed reality, or some combination and / or derivative thereof. Artificial reality content may include fully generated content or generated content combined with captured (e.g., real-world) content. Artificial reality content may include video, audio, physical or tactile feedback, or some combination thereof. Any of these contents may be presented in a single channel or multiple channels, such as in a stereoscopic video that produces a three-dimensional effect for the audience. In addition, in some embodiments, artificial reality may also be associated with applications, products, accessories, services, or some combination thereof, which are used, for example, to create content in artificial reality and / or otherwise used in artificial reality (e.g., performing activities in artificial reality). Artificial reality systems that provide artificial reality content can be implemented on a variety of platforms, including wearable displays such as HMDs connected to a host computer system, standalone HMDs, near-eye displays with eyeglass form factors, mobile devices or computing systems, or any other hardware platform capable of providing artificial reality content to one or more viewers.

[0095] refer to Fig.16A , HMD 1600 is an example of an AR / VR wearable display system that surrounds the user's face for greater immersion in an AR / VR environment. HMD 1600 is Fig.151600 is an embodiment of a near-eye display 1500 of the present invention and may include similar elements. The function of HMD 1600 is to enhance the view of the physical, real-world environment with computer-generated images, and / or to generate a completely virtual 3D image. HMD 1600 may include a front body 1602 and a band 1604. The front body 1602 is configured to be placed in front of the user's eyes in a secure and comfortable manner, and the band 1604 can be stretched to secure the front body 1602 on the user's head. A display system 1680 can be disposed in the front body 1602 for presenting AR / VR images to the user. The display system 1680 may include any pupil replica waveguide and diffraction grating disclosed herein. The side 1606 of the front body 1602 may be opaque or transparent.

[0096] In some embodiments, the front body 1602 includes a locator 1608, an inertial measurement unit (IMU) 1610 for tracking the acceleration of the HMD 1600, and a position sensor 1612 for tracking the position of the HMD 1600. The IMU 1610 is an electronic device that generates data indicating the position of the HMD 1600 based on measurement signals received from one or more position sensors 1612, and the position sensor 1612 generates one or more measurement signals in response to the movement of the HMD 1600. Examples of the position sensor 1612 include: one or more accelerometers, one or more gyroscopes, one or more magnetometers, another suitable type of sensor that detects movement, a type of sensor used for error correction of the IMU 1610, or some combination thereof. The position sensor 1612 can be located outside the IMU 1610, inside the IMU 1610, or some combination of these two locations.

[0097] The localizer 1608 is tracked by an external imaging device of the virtual reality system so that the virtual reality system can track the position and orientation of the entire HMD 1600. The information generated by the IMU 1610 and the position sensor 1612 can be compared with the position and orientation obtained by tracking the localizer 1608 to improve the tracking accuracy of the position and orientation of the HMD 1600. When the user moves and turns in 3D space, accurate position and orientation are important for presenting an appropriate virtual scene to the user.

[0098] The HMD 1600 may also include a depth camera assembly (DCA) 1611 that captures data describing depth information of a local area surrounding part or all of the HMD 1600. To this end, the DCA 1611 may include a laser radar (LIDAR), a phase-sensitive depth camera, or a similar device. The depth information may be compared with information from the IMU 1610 to more accurately determine the position and orientation of the HMD 1600 in 3D space.

[0099] HMD 1600 may also include an eye tracking system 1614 for determining the orientation and position of the user's eyes in real time. The position and orientation of the eyes obtained also allow HMD 1600 to determine the gaze direction of the user and adjust the image generated by the display system 1680 accordingly. In one embodiment, vergence, i.e., the convergence angle of the user's eye gaze, is determined. Depending on the viewing angle and eye position, the determined gaze direction and visual convergence angle can also be used for real-time compensation of visual artifacts. In addition, the determined visual convergence angle and gaze angle can be used to interact with the user, highlight objects, bring objects to the foreground, create additional objects or pointers, etc. An audio system may also be provided, which includes, for example, a group of small speakers built into the front body 1602.

[0100] refer to Fig. 16B , the AR / VR system 1650 includes Fig.16A The HMD 1600, the external console 1690, and the input / output (I / O) interface 1615, the external console 1690 stores various AR / VR applications, settings and calibration programs, 3D videos, etc., and the input / output (I / O) interface 1615 is used to operate the console 1490 and / or interact with the AR / VR environment. The HMD 1600 can be "tethered" to the console 1690 with a physical cable, or via a communication interface such as A wireless communication link such as Wi-Fi is connected to the console 1690. There may be multiple HMDs 1600, each HMD 1600 having an associated I / O interface 1615, wherein each HMD 1600 and I / O interface 1615 communicate with the console 1690. In alternative configurations, different and / or additional components may be included in the AR / VR system 1650. Additionally, in combination Fig.16A and 16B The functionality described by one or more components shown in FIG. 1 may be combined with Fig.16A and 16B The described manner is distributed among the components in different ways. For example, some or all of the functions of the console 1615 may be provided by the HMD 1600, and vice versa. The HMD 1600 may be provided with a processing module capable of implementing such functions.

[0101] As referenced above Fig.16A As described, the HMD 1600 may include an eye tracking system 1614 ( Fig. 16B), an IMU 1610 for determining the position and orientation of the HMD 1600 in 3D space, a DCA 1611 for capturing the external environment, a position sensor 1612 for independently determining the position of the HMD 1600, and a display system 1680 for displaying AR / VR content to the user. The display system 1680 includes ( Fig. 16B ) electronic display 1625, such as, but not limited to, a scanning projector display. The display system 1680 also includes an optical block 1630, whose function is to transmit the image generated by the electronic display 1625 to the user's eyes. The optical block 1630 may include a pupil replica waveguide and a diffraction grating disclosed herein. The optical block 1630 may also include various lenses (e.g., refractive lenses, Fresnel lenses, diffractive lenses, active or passive Pancharatnam–Berry phase (PBP) lenses, liquid lenses, liquid crystal lenses, etc.), pupil replica waveguides, grating structures, coatings, etc. The display system 1680 may also include a zoom module 1635, which may be part of the optical block 1630. The function of the zoom module 1635 is to adjust the focus of the optical block 1630 to, for example, compensate for vergence-accommodation conflict, correct for visual defects of a specific user, offset aberrations of the optical block 1630, etc.

[0102] The I / O interface 1615 is a device that allows a user to send an action request and receive a response from the console 1690. An action request is a request to perform a specific action. For example, an action request may be an instruction to start or end the capture of an image or video data, or an instruction to perform a specific action within an application. The I / O interface 1615 may include one or more input devices, such as a keyboard, a mouse, a game controller, or any other suitable device for receiving an action request and transmitting the action request to the console 1690. The action request received by the I / O interface 1615 is transmitted to the console 1690, and the console 1690 performs the action corresponding to the action request. In some embodiments, the I / O interface 1615 includes an IMU that captures calibration data indicating an estimated position of the I / O interface 1615 relative to the initial position of the I / O interface 1615. In some embodiments, the I / O interface 1615 may provide tactile feedback to the user according to the instruction received from the console 1690. For example, tactile feedback may be provided when an action request is received, or when console 1690 transmits instructions to I / O interface 1615 that cause I / O interface 1615 to generate tactile feedback when console 1690 performs an action.

[0103] The console 1690 may provide content to the HMD 1600 for processing based on information received from one or more of the IMU 1610, the DCA 1611, the eye tracking system 1614, and the I / O interface 1615. Fig. 16B In the example shown, the console 1690 includes an application storage 1655, a tracking module 1660, and a processing module 1665. Some embodiments of the console 1690 may have different Fig. 16B Similarly, the functions described further below can be combined with Fig.16A and 16B The described methods are distributed among the components of the console 1690 in different ways.

[0104] The application storage 1655 may store one or more applications for execution by the console 1690. An application is a set of instructions that, when executed by a processor, generates content for presentation to a user. The content generated by the application may be responsive to input received from the user via the movement or I / O interface 1615 of the HMD 1600. Examples of applications include: gaming applications, presentation and conferencing applications, video playback applications, or other suitable applications.

[0105] Tracking module 1660 may calibrate AR / VR system 1650 using one or more calibration parameters, and may adjust one or more calibration parameters to reduce errors in the determination of the position of HMD 1600 or I / O interface 1615. The calibration performed by tracking module 1660 also takes into account information received from IMU 1610 in HMD 1600 and / or an IMU (if any) included in I / O interface 1615. In addition, if tracking of HMD 1600 is lost, tracking module 1660 may recalibrate part or all of AR / VR system 1650.

[0106] The tracking module 1660 may track the movement of the HMD 1600 or the I / O interface 1615, the IMU 1610, or some combination thereof. For example, the tracking module 1660 may determine the location of a reference point of the HMD 1600 in a map of the local area based on information from the HMD 1600. The tracking module 1660 may also determine the location of the reference point of the HMD 1600 or the reference point of the I / O interface 1615 using data from the IMU 1610 indicating the location of the HMD 1600 or using data from an IMU included in the I / O interface 1615 indicating the location of the I / O interface 1615, respectively. Furthermore, in some embodiments, the tracking module 1660 may use a portion of the data from the IMU 1610 indicating the location of the HMD 1600 and a representation of the local area from the DCA 1611 to predict the future location of the HMD 1600. The tracking module 1660 provides the estimated or predicted future position of the HMD 1600 or the I / O interface 1615 to the processing module 1665 .

[0107] The processing module 1665 may generate a 3D map of an area (“local area”) surrounding part or all of the HMD 1600 based on information received from the HMD 1600. In some embodiments, the processing module 1665 determines depth information for the 3D map of the local area based on information related to a technique used in calculating depth received from the DCA 1611. In various embodiments, the processing module 1665 may use the depth information to update a model of the local area and generate content based in part on the updated model.

[0108] The processing module 1665 executes an application within the AR / VR system 1650 and receives position information, acceleration information, velocity information, predicted future position, or some combination thereof of the HMD 1600 from the tracking module 1660. Based on the received information, the processing module 1665 determines the content to be provided to the HMD 1600 for presentation to the user. For example, if the received information indicates that the user has looked to the left, the processing module 1665 generates content for the HMD 1600 that reflects (mirror) the user's movement in a virtual environment or in an environment that enhances a local area with additional content. In addition, the processing module 1665 executes an action within an application executed on the console 1690 in response to an action request received from the I / O interface 1615, and provides feedback to the user that the action is performed. The feedback provided may be visual or auditory feedback via the HMD 1600 or tactile feedback via the I / O interface 1615.

[0109] In some embodiments, based on the eye tracking information (e.g., the orientation of the user's eyes) received from the eye tracking system 1614, the processing module 1665 determines the resolution of the content provided to the HMD 1600 for presentation to the user on the electronic display 1625. The processing module 1665 can provide content to the HMD 1600 that has a maximum pixel resolution in the foveal region of the electronic display 1625 where the user is gazing. The processing module 1665 can provide a lower pixel resolution in other areas of the electronic display 1625, thereby reducing the power consumption of the AR / VR system 1650 and saving computing resources of the console 1690 without compromising the user's visual experience. In some embodiments, the processing module 1665 can further use the eye tracking information to adjust the display position of objects on the electronic display 1625 to prevent visual convergence-accommodation conflicts and / or to counteract optical distortions and aberrations.

[0110] Hardware for implementing the various illustrative logics, logic blocks, modules, and circuits described in conjunction with the aspects disclosed herein may be implemented or executed with a general purpose processor, digital signal processor (DSP), application specific integrated circuit (ASIC), field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but alternatively, the processor may be any conventional processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors combined with a DSP core, or any other such configuration. Alternatively, some steps or methods may be performed by circuits specific to a given function.

[0111] The present invention is not limited in scope by the specific embodiments described herein. In fact, in addition to those embodiments and modifications described herein, various other embodiments and modifications will be apparent to those of ordinary skill in the art according to the foregoing description and accompanying drawings. Therefore, such other embodiments and modifications are intended to fall within the scope of the present invention. In addition, although the present invention is described herein in a specific environment for a specific purpose in the context of a specific implementation, a person of ordinary skill in the art will recognize that its usefulness is not limited thereto, and the present invention can be beneficially implemented in any number of environments for any number of purposes. Therefore, the claims set forth should be interpreted in light of the full breadth and spirit of the present invention as described herein.

Claims

1. A pupil replicating waveguide, comprising: a slab of transparent material for propagating display light therein by total internal reflection; a diffraction grating supported by the panel and comprising a plurality of fringes formed of a twisted nematic (TN) liquid crystal (LC) material in a polymer substrate, wherein the fringes are tilted to outcouple display light from the panel into blazed diffraction orders by diffraction, wherein a larger portion of the display light is outcoupled into the blazed diffraction orders and a smaller portion of the display light is outcoupled into non-blazed diffraction orders; The twisted nematic (TN) liquid crystal (LC) material has an ordinary refractive index n for light polarized perpendicular to the molecules of the twisted nematic (TN) liquid crystal (LC) material. O , while for light polarized parallel to the molecules of the twisted nematic (TN) liquid crystal (LC) material, it has an extraordinary refractive index n E , wherein the refractive index contrast of the polarized display light incident on the diffraction grating has a refractive index contrast distribution along the thickness direction of the diffraction grating; The refractive index contrast is greater in the middle of the refractive index contrast distribution than on both sides of the refractive index contrast distribution, thereby reducing the portion of incident polarized display light that is outcoupled into the non-blazed diffraction order.

2. The pupil replicating waveguide according to claim 1, wherein: The refractive index of the polymer substrate material is closer to n O Rather than being closer to n E , whereby the refractive index contrast is greater in the middle of the refractive index contrast distribution than on both sides of the refractive index contrast distribution.

3. A pupil replicating waveguide according to claim 1 or claim 2, wherein: The refractive index contrast distribution is symmetric along a thickness direction of the diffraction grating.

4. The pupil replicating waveguide according to any one of claims 1 to 3, wherein: The refractive index contrast distribution is substantially zero on both sides.

5. The pupil replicating waveguide according to any one of claims 1 to 4, wherein: The twisted nematic (TN) liquid crystal (LC) material is polymer-stabilized.

6. The pupil replicating waveguide according to any one of claims 1 to 5, wherein: The refractive index contrast profile is a smoothly varying function.

7. The pupil replicating waveguide of claim 6, wherein the smoothly varying function is a Gaussian function.

8. A pupil replicating waveguide according to any one of claims 1 to 7, further comprising an input grating for coupling display light inwardly into the slab.

9. A method of manufacturing a pupil replicating waveguide, the method comprising: forming a plurality of inclined fringes on a transparent material plate for outcoupling display light from the plate into a blazed diffraction order by diffraction, the inclined fringes having a first refractive index n1; forming a uniform layer on the plurality of inclined stripes and the flat plate, the uniform layer forming gaps between the inclined stripes covered by the uniform layer, the uniform layer having a second refractive index n2; and forming an outer coating layer on the uniform layer, the outer coating layer filling the gaps between the inclined stripes covered by the uniform layer and having a third refractive index n3; Among them, n1>n2>n3 or n1 <n2<n3; Wherein, the effective refractive index contrast distribution of the diffraction grating along the thickness direction of the diffraction grating is symmetrical; further, wherein the refractive index contrast is greater in the middle of the refractive index contrast distribution than on both sides of the refractive index contrast distribution.

10. The method according to claim 9, wherein: The plurality of inclined stripes are formed by embossing; or Wherein, the plurality of inclined stripes are formed by etching.

11. The method according to claim 9 or claim 10: in, The uniform layer is formed by atomic layer deposition (ALD); Wherein, the outer coating layer is formed by spin coating.

12. A pupil replicating waveguide comprising: a slab of transparent material for propagating display light therein by total internal reflection; a diffraction grating supported by the plate and comprising: a plurality of inclined fringes for outcoupling display light from the panel into blazed diffraction orders by diffraction, the inclined fringes having a first refractive index n1; a uniform layer on the plurality of inclined stripes and the flat plate, the uniform layer forming gaps between the inclined stripes covered by the uniform layer, the uniform layer having a second refractive index n2; and an outer coating on the uniform layer, the outer coating being disposed in the gaps between the inclined stripes covered by the uniform layer and having a third refractive index n3; Among them, n1>n2>n3 or n1 <n2<n3; Wherein, the effective refractive index contrast distribution of the diffraction grating along the thickness direction of the diffraction grating is symmetrical; further, wherein the refractive index contrast is greater in the middle of the refractive index contrast distribution than on both sides of the refractive index contrast distribution.

13. The pupil replicating waveguide of claim 12, wherein: The plurality of inclined stripes are formed by embossing, or Wherein, the plurality of inclined stripes are formed by etching.

14. A pupil replicating waveguide according to claim 12 or claim 13, wherein: The uniform layer is formed by atomic layer deposition (ALD).

15. A pupil replicating waveguide according to any one of claims 12 to 14, wherein: The outer coating layer is formed by spin coating.

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