Diffractive waveguides and augmented reality display devices incorporating them.

Abstract

This application discloses a diffractive waveguide and an augmented reality display device. The diffractive waveguide includes a waveguide substrate and a first grating and a second grating disposed on the waveguide substrate. The first grating is configured to couple input light carrying image information into the waveguide substrate and propagate it through total internal reflection. The second grating includes a diffraction relief structure configured to at least dilate the pupil of light propagating therein. The diffractive waveguide also includes an optical film layer that at least covers the second grating and includes a filling structure. The filling structure fills the gaps in the diffraction relief structure of the second grating and forms an overflow layer that extends beyond the diffraction relief structure. The refractive index of the filling structure is greater than the refractive index of the ambient medium and less than the refractive index of the second grating. According to embodiments of the present invention, the transmittance of ambient light in the grating region can be effectively improved, and the difference between the grating region and the non-grating region can be reduced, thereby improving the overall visual experience.

Description

Technical Field

[0001] This invention relates to display technology based on diffractive waveguides; specifically, it relates to a diffractive waveguide device for augmented reality display and a display device having the same. Background Technology

[0002] Augmented reality (AR) display technology, as a highly intelligent and portable display technology, is gradually becoming more widely available. Diffractive waveguide-based display technology is currently one of the mainstream solutions for realizing AR displays. This technology involves placing a waveguide grating on a waveguide substrate, which includes an input grating and an output grating. The input grating receives input light carrying image information from an optomechanical source and couples it into the waveguide substrate. The output grating propagates and expands the light carrying image information while simultaneously coupling the light out of the waveguide substrate, forming an output light field. The eye receives the light from this output light field, allowing it to observe, for example, the image carried by the incident light.

[0003] Diffractive waveguides, with their advantages of being lightweight, thin, having strong pupil-expanding capabilities, and being easy to mass-produce, have become core components of augmented reality display devices. However, diffractive waveguides are not without their drawbacks. In particular, how to make diffractive waveguides even more suitable for the needs of augmented reality displays remains to be explored. Summary of the Invention

[0004] The purpose of this invention is to provide a diffractive waveguide device for augmented reality display and a display device having the same, which at least partially overcomes the problems in the prior art.

[0005] According to one aspect of the present invention, a diffractive waveguide for augmented reality display is provided, comprising a waveguide substrate and a first grating and a second grating disposed on the waveguide substrate. The first grating is configured to couple input light carrying image information into the waveguide substrate and propagate it through total internal reflection. The second grating includes a diffraction relief structure configured to at least dilate the pupil of light propagating thereto. The diffractive waveguide further includes an optical film layer that at least covers the second grating and includes a filling structure that fills the voids in the diffraction relief structure of the second grating and forms an overflow layer higher than the diffraction relief structure. The filling structure has a first refractive index n1, wherein n0 <n1<n g , where n o Let n be the refractive index of the ambient medium. g is the refractive index of the second grating.

[0006] In some embodiments, the second grating is a two-dimensional coupling grating configured to expand the pupil of light from the first grating and couple it outward from the waveguide substrate to achieve image display.

[0007] In some embodiments, the diffractive waveguide further includes a third grating disposed on the waveguide substrate. The third grating includes a diffraction relief structure configured to at least enlarge the pupil of light propagating therein. One of the second grating and the third grating is a deflection grating, and the other is a coupling grating. The deflection grating is used to deflect light from the first grating to propagate towards the coupling grating while simultaneously enlarging the pupil of light propagating therein. The coupling grating is used to enlarge the pupil of light propagating therein and couple it outward from the waveguide substrate to achieve image display.

[0008] Advantageously, the optical film layer also covers the third grating, the filling structure fills the gaps in the diffraction relief structure of the third grating and forms an overflow layer that protrudes from the diffraction relief structure, and wherein: n1 <n g ', where n g ' is the refractive index of the third grating.

[0009] Advantageously, the optical film layer does not cover the first grating.

[0010] In some embodiments, the optical film layer also covers the waveguide substrate surrounding the second grating.

[0011] Advantageously, the optical film layer is configured to satisfy: (n0+n g ) / 3 <n1<2(n0+n g ) / 3.

[0012] Advantageously, the optical film layer is configured to satisfy: 2(n0+n g ) / 5 <n1<3(n0+n g ) / 5.

[0013] Advantageously, the thickness of the overflow layer is d1, and 3.5 nm. <d1<400nm。

[0014] Advantageously, the thickness of the overflow layer satisfies 30 nm. <d1<200nm。

[0015] Advantageously, the optical film layer further includes at least one composite layer covering the filling structure, each composite layer including a lower film layer and an upper film layer covering the lower film layer, wherein the lower film layer has a refractive index greater than the refractive index of the material of the structure covered by the lower film layer, and the upper film layer has an upper refractive index less than the lower refractive index.

[0016] Advantageously, the thickness of the lower film layer is d 21 The thickness of the upper film layer is d. 22 And 3.5nm <d 21<400nm, 3.5nm <d 22 <400nm.

[0017] Advantageously, the composite layer satisfies at least one of the following conditions:

[0018] 20nm <d 21 <200nm; and

[0019] 30nm <d 22 <200nm.

[0020] According to another aspect of the invention, an augmented reality display device is also provided, the augmented reality display device including a lens, the lens including the diffractive waveguide as described above.

[0021] Advantageously, the augmented reality display device is a near-eye display device and also includes a frame for holding the lens close to the eye.

[0022] In the diffractive waveguide according to an embodiment of the present invention, by setting an optical film layer, the gaps in the relief structure of the grating are filled with a material having a refractive index within a predetermined range in at least part of the grating region to form an overflow layer, thereby improving the transmittance of ambient light in the grating region, reducing the difference between the grating region and the non-grating region, and thus improving the overall visual experience of the diffractive waveguide when used for augmented reality display. Attached Figure Description

[0023] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0024] Figure 1 A schematic cross-sectional view of a diffractive optical waveguide for augmented reality display according to an embodiment of the present invention;

[0025] Figure 2 An example of an optical film layer covering a second grating in a diffractive waveguide according to an embodiment of the present invention is shown schematically;

[0026] Figure 3 Another example of an optical film layer covering a second grating in a diffractive waveguide according to an embodiment of the present invention is illustrated schematically;

[0027] Figure 4 The schematic plane is for different examples of diffractive waveguides according to embodiments of the present invention, wherein the diffractive waveguides have different grating configurations;

[0028] Figure 5 The graph showing the transmittance as a function of wavelength in data example 1 is shown;

[0029] Figure 6 The graph showing the transmittance as a function of wavelength in data example 2 is shown.

[0030] Figure 7 The graph showing the transmittance versus wavelength in data example 3 is shown; and

[0031] Figure 8 The graph showing the transmittance as a function of wavelength in data example 4 is shown. Detailed Implementation

[0032] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. For ease of description, only the parts relevant to the invention are shown in the drawings. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0033] First, refer to Figure 1 The overall structure of a diffractive optical waveguide for augmented reality display according to an embodiment of the present invention is described. Figure 1 This is a schematic cross-sectional view of a diffractive optical waveguide according to an embodiment of the present invention. Figure 1 As shown, the diffractive waveguide 1 includes a waveguide substrate 1a and a first grating 10 and a second grating 20 disposed on the waveguide substrate 1a; according to an embodiment of the present invention, the diffractive waveguide 1 further includes an optical film layer C, which covers at least the second grating 20.

[0034] The first grating 10 is configured to direct the input light L carrying image information. in It is coupled into the waveguide substrate 1a and propagates in the waveguide substrate 1a through total internal reflection. The first grating 10 can also be called a coupling grating.

[0035] The second grating 20 includes a diffraction relief structure 20a (see...) Figure 2 and Figure 3 The second grating 20 is configured to expand the pupil of light propagating therein, for example, in one or two dimensions along the plane of the waveguide substrate 1a. The second grating 20 can also be referred to as a pupil expander. Both the coupling grating and the transition grating in a diffractive waveguide are pupil expanders. The second grating in the diffractive waveguide according to an embodiment of the present invention can be either a coupling grating or a transition grating. This will be described in more detail below.

[0036] Figure 2 An example of an optical film layer covering a second grating in a diffractive waveguide according to an embodiment of the present invention is shown schematically.

[0037] exist Figure 2In the diagram, the second grating 20 is shown as having a diffraction relief structure 20a with a simple rectangular cross-section. It should be understood that this is merely illustrative, and the invention is not limited in terms of the specific diffraction relief structure of the second grating.

[0038] exist Figure 2 In the example shown, the optical film layer C includes a filling structure C1 that fills the gaps in the diffraction relief structure 20a of the second grating 20 and forms an overflow layer C1 that extends beyond the diffraction relief structure 20a. In this application, "overflow layer" refers to the portion of the filling structure that extends beyond the diffraction relief structure in a direction perpendicular to the surface of the waveguide substrate, such as... Figure 2 As shown. Advantageously, the overflow layer is formed with a flat surface. However, in some cases, due to the optical film manufacturing process or the influence of the shape of the underlying diffraction relief structure, the surface of the overflow layer may exhibit minute undulations, for example, undulations of about ten nanometers. Such deviations do not deviate from the scope intended to be covered by the present invention. In other words, in the diffractive waveguide according to an embodiment of the present invention, the surface of the overflow layer may have undulations of about ten nanometers relative to a plane.

[0039] According to an embodiment of the present invention, the refractive index of the filling structure C1 is greater than the refractive index of the ambient medium and less than the refractive index of the diffraction relief structure 20a of the second grating 20. To enable the diffraction waveguide according to the embodiment of the present invention to achieve the same or similar effect for ambient light over the widest possible visible light wavelength range, this application selects the refractive index at a wavelength of 589 nm (yellow light) to examine whether various refractive index relationships are satisfied. That is, according to an embodiment of the present invention, the filling structure C1 has a first refractive index n1, wherein n0 <n1<n g , where n o The refractive index of the ambient medium surrounding the second grating 20 and the waveguide substrate 1a, n g is the refractive index of the diffraction relief structure 20a of the second grating 20.

[0040] It should be noted that the ambient medium is usually air; however, in some cases, materials with ultra-low refractive index (such as adhesives with a refractive index of around 1.2) can be used instead of air as the ambient medium surrounding the diffractive waveguide (or its waveguide substrate and second grating).

[0041] In the diffractive waveguide for augmented reality display according to an embodiment of the present invention, by providing an optical film layer, in at least a portion of the grating region (e.g., a second grating) of the grating (see... Figure 1 In region I shown, a refractive index within a predetermined range (first refractive index n1, satisfying n0) is used. <n1<n g) The voids in the relief structure of the material-filled grating are filled to form an overflow layer, which can advantageously improve the transmittance of ambient light in the grating region and reduce the difference in the transmittance of ambient light between the grating region and the non-grating region (see Figure 1 the region II shown), so that the user can obtain a more natural visual experience when observing the environment through the diffractive optical waveguide 1. In short, the diffractive optical waveguide according to the embodiment of the present invention is beneficial to improving the overall visual experience of the user in augmented reality display applications.

[0042] Currently, the image display optical solutions based on diffractive optical waveguides mainly focus on improving the performance and performance in terms of color and light utilization efficiency; while the present invention improves the diffractive optical waveguide in terms of providing a more natural and coordinated overall visual experience for augmented reality display applications, which provides a new research and improvement direction for diffractive optical waveguides used in augmented reality displays.

[0043] According to different embodiments of the present invention, the material of the filling structure C1 can be advantageously selected to satisfy (n0 + n g ) / 3 < n1 < 2(n0 + n g ).

[0044] According to a preferred embodiment of the present invention, the material of the filling structure C1 can be selected to satisfy 2(n0 + n g ) / 5 < n1 < 3(n0 + n g ).

[0045] More preferably, the material of the filling structure C1 can be selected such that n1 = (n0 + n g ) / 2 ± 0.1.

[0046] In addition, according to different embodiments of the present invention, the thickness d1 of the overflow layer C 11 can be selected to satisfy 3.5 nm < d1 < 400 nm. Preferably, the thickness d1 of the overflow layer C 11 can be selected to satisfy 30 nm < d1 < 200 nm. Different overflow layer thicknesses will change the transmittance of ambient light. By selecting the overflow layer thickness as above, the optical film layer C can effectively regulate the transmittance of ambient light in the grating region I.

[0047] The optical film layer in the diffractive optical waveguide according to the embodiment of the present invention is not limited to Figure 2 the structure shown. For example, the optical film layer may further include at least one composite layer covering the filling structure. See Figure 3 , which shows another example of the optical film layer C. In this example, the optical film layer C further includes a composite layer C2 covering the filling structure C1, and the composite layer C2 includes a first layer C 21 and a second layer C covering the first layer C 21 ).22 The first layer C 21 Having a refractive index n 21 Refractive index n 21 Greater than the first layer C 21 The refractive index of the material in the covering filling structure C1 is n1, and the second layer C 22 Having a refractive index n 22 And satisfy n 22 <n 21 .

[0048] In other examples not shown, the optical film layer C may also include more composite layers, each consisting of a lower film layer (first layer) with a relatively high refractive index and an upper film layer (second layer) with a lower refractive index, wherein the refractive index of the lower film layer is greater than the refractive index of the material of the structure it covers (e.g., a filling structure or the upper film layer of another composite layer).

[0049] The thickness of the lower film layer is d 21 The thickness of the upper film is d 22 According to different embodiments of the present invention, the thickness of the composite layer can be selected to satisfy: 3.5 nm. <d 21 <400nm, 3.5nm <d 22 <400nm. Preferably, the composite layer satisfies at least one of the following conditions: 20nm <d 21 <200nm; and 30nm <d 22 <200nm.

[0050] Next, refer to Figure 4 The present invention is described in conjunction with diffractive waveguides having different grating configurations. Figure 4 Different examples of diffractive waveguides with different grating configurations according to embodiments of the present invention are illustrated in schematic plan view.

[0051] Figure 4 Figure (a) illustrates a diffractive waveguide 100 according to an embodiment of the present invention. The diffractive waveguide 100 includes a waveguide substrate 100a and a coupling grating 110 and a coupling grating 120 disposed on the waveguide substrate 100a. The coupling grating 110 is configured to couple input light carrying image information into the waveguide substrate 100a and allow it to propagate through total internal reflection. The coupling grating 120 includes a diffraction relief structure configured to expand the pupil of the light propagating therein while coupling it outward from the waveguide to achieve image display. In the diffractive waveguide 100, an optical film layer C covers the coupling grating.

[0052] Figure 4Figure (b) illustrates a diffractive waveguide 200 according to an embodiment of the present invention, comprising a waveguide substrate 200a and a coupling grating 210, a coupling grating 220, and a deflection grating 230 disposed on the waveguide substrate 200a. The coupling grating 210 and the coupling grating 220 function similarly to the coupling grating 110 and the coupling grating 120 shown in Figure (a). The deflection grating is configured to deflect light from the coupling grating 210 towards the coupling grating 220 while simultaneously expanding the pupil of the light. The deflection grating 230 includes a diffraction relief structure for achieving the above-described function. In the diffractive waveguide 200, an optical film layer C covers both the coupling grating 220 and the deflection grating 230.

[0053] When the optical film layer C covers two gratings, according to an embodiment of the present invention, the optical film layer C satisfies the above reference with respect to one of the gratings (i.e., the second grating). Figure 2 The refractive indices n0, n1, and n are introduced. g The relationship between n1 and n2 is similar to that between n1 and n2, and also with respect to another grating (i.e., the third grating), namely: n1 <n g ', where n g ' is the refractive index of the third grating.

[0054] Figure 4 Figure (c) illustrates a diffractive waveguide 300 according to an embodiment of the present invention, which has the same grating configuration as the diffractive waveguide 200 shown in Figure (b) (i.e., the diffractive waveguide 300 includes a waveguide substrate 300a and a coupling grating 310, a coupling grating 320, and a transition grating 330 disposed on the waveguide substrate 300a), except that in the diffractive waveguide 300, the optical film layer C covers the transition grating 330 but does not cover the coupling grating 320. Although not shown in the figure, those skilled in the art can understand from the example shown in Figure (c) that the optical film layer C proposed according to the embodiment of the present invention can also cover the coupling grating 320 but not the transition grating 330.

[0055] According to a preferred embodiment of the present invention, such as Figure 4As shown in Figure (b), the optical film C also covers the waveguide substrate surrounding the coupling grating 220 and the transition grating 230. Preferably, the optical film C can advantageously cover the entire non-grating area. Diffractive waveguides typically use waveguide substrates with high refractive indices, which helps to expand the field of view of the image display, but also results in a higher reflectivity of the waveguide substrate surface to ambient light. By setting the optical film C in the non-grating area, it is possible to help improve the transmittance of ambient light in the non-grating area, thereby further improving the overall visual experience provided to the user by the diffractive waveguide. Moreover, since the optical film C covers almost the entire area of ​​the diffractive waveguide (in some cases not covering the coupling grating), it is easy to manufacture and helps to reduce manufacturing costs.

[0056] In some cases, because the coupling grating is encapsulated to better receive input light from the optomechanical system, the optical film C can advantageously cover all areas of the waveguide substrate 200a except for the coupling grating 210. In other cases, the coupling grating is covered with a light-shielding layer, such as metal, and the optical film C according to embodiments of the invention can be applied to the area of ​​the coupling grating during fabrication. This simplifies the manufacturing process without affecting the performance of the coupling grating.

[0057] The technical advantages of the diffractive waveguide according to embodiments of the present invention will be illustrated below with data examples. In the data examples of this application, the ambient medium is air (refractive index n). o =1), the refractive index of the waveguide substrate is 1.9, the diffraction relief structure of the grating region includes a two-dimensional array of upright columnar unit structures, and the refractive index n of the diffraction relief structure is... g =1.9.

[0058] (Data Example 1)

[0059] In Example 1, the ambient light transmittance of the diffraction relief structure was compared and analyzed through simulation calculations under the following different conditions when the unit structure was a raised structure:

[0060] (1) Grating region without optical coating;

[0061] (2) The grating region covered by the optical film layer C, wherein the optical film layer C includes a filling structure C1, and the refractive index of the filling structure C1 is n1 = (n0 + n g ) / 2 = 1.45, overflow layer C 11 The thickness d1 = 150 nm;

[0062] (3) The grating region covered by optical film C, wherein optical film C has the same structure and parameters as in item (2), the difference being: n1=2(n0+n g ) / 5 = 1.16;

[0063] (4) The grating region covered by optical film C, wherein optical film C has the same structure and parameters as in item (2), the difference being: n1=3(n0+n g ) / 5 = 1.74; and

[0064] (5) Non-grating regions without optical films.

[0065] Figure 5 The graphs showing the transmittance versus wavelength for the various cases described in Data Example 1 are shown.

[0066] like Figure 5 As shown, the ambient light transmittance of the grating region without an optical film layer (see Figure 1). Figure 5 The medium curve (without a film layer) varies greatly within the visible light wavelength range, indicating poor uniformity, with an average transmittance of approximately 80%. In contrast, the ambient light transmittance in the non-grating region without an optical film layer (see...) Figure 5 The uniformity of the curve ("no film layer in the non-grating area") is very good, with an average transmittance of about 88%. The transmittance difference between the grating area and the non-grating area is very large.

[0067] In contrast, the uniformity and average transmittance of ambient light transmittance in the grating region covered by optical film layer C are significantly improved, where: n1=2(n0+n g In the case where ) / 5 = 1.16 (see...) Figure 5 The average transmittance is increased to about 89% (medium curve "150nm 2 / 5"); n1 = 3(n0 + n g In the case where ) / 5 = 1.74 (see...) Figure 5 The average transmittance is increased to about 88% (medium curve "10nm 3 / 5"); n1 = (n0 + n g In the case where ) / 2 = 1.45 (see...) Figure 5 The average transmittance increased to approximately 92.7% (at the mid-curve "150nm 1 / 2"). It can be seen that n1 = (n0 + n g In the case of 1 / 2, the average transmittance of the grating region is optimal. Furthermore, from... Figure 5 As shown in the curve graph, n1 = (n0 + n g In the case of ) / 2, the uniformity of transmittance of the grating region in the visible light wavelength range is greatly improved.

[0068] (Data Example 2)

[0069] In Example 2, simulation calculations were used to compare and analyze the ambient light transmittance under the following different conditions when the unit structure of the diffraction relief structure is a raised structure:

[0070] (1) Grating region without optical coating;

[0071] (2) The grating region covered by the optical film layer C, wherein the optical film layer C includes a filling structure C1, and the refractive index of the filling structure C1 is n1 = (n0 + n g ) / 2 = 1.45, overflow layer C 11 The thickness d1 = 50 nm;

[0072] (3) The grating region covered by optical film C, wherein optical film C has the same structure and parameters as in item (2), the difference being: n1=2(n0+n g ) / 5 = 1.16;

[0073] (4) The grating region covered by optical film C, wherein optical film C has the same structure and parameters as in item (2), the difference being: n1=3(n0+n g ) / 5 = 1.74; and

[0074] (5) Non-grating regions without optical films.

[0075] Compared to Data Example 1, the thickness of the overflow layer was changed in Data Example 2.

[0076] Figure 6 The graphs showing the transmittance versus wavelength for the various cases mentioned above in Data Example 2 are shown.

[0077] Figure 6 The ambient light transmittance of the grating region without an optical film layer in Example 2 is shown in the data (see Example 2). Figure 6 Mid-curve (without film layer) and ambient light transmittance in non-grating regions (see Figure 6 The curve ("no film layer in non-grating areas") is the same as in data example 1, and will not be repeated here.

[0078] In contrast, the uniformity and average transmittance of ambient light transmittance in the grating region covered by optical film layer C are significantly improved, where: n1=2(n0+n g In the case where ) / 5 = 1.16 (see...) Figure 6 The average transmittance is increased to about 85% (intermediate curve "50nm 2 / 5"); n1 = 3(n0 + n g In the case where ) / 5 = 1.74 (see...) Figure 6 The average transmittance is increased to about 85% (intermediate curve "50nm 3 / 5"); n1 = (n0 + n g In the case where ) / 2 = 1.45 (see...) Figure 6 The average transmittance is increased to about 92% (in the mid-curve "50nm 1 / 2"). It can be seen that n1 = (n0 + n gIn the case of 1 / 2, the average transmittance of the grating region is optimal. Furthermore, from... Figure 6 As shown in the curve graph, n1 = (n0 + n g The uniformity of transmittance in the visible light wavelength range is greatly improved under the condition of ) / 2.

[0079] (Data Example 3)

[0080] In Example 3, simulation calculations were used to compare and analyze the ambient light transmittance under the following different conditions when the unit structure of the diffraction relief structure is a concave hole structure:

[0081] (1) The grating region without an optical coating; and

[0082] (2) The grating region covered by the optical film layer C, wherein the optical film layer C includes a filling structure C1, and the refractive index of the filling structure C1 is n1 = (n0 + n g ) / 2 = 1.45, overflow layer C 11 The thickness d1 = 50 nm.

[0083] Compared with items (1) and (2) in Data Example 2, Data Example 3 changes the unit structure of the diffraction relief structure in the grating from a raised structure to a concave hole structure.

[0084] Figure 7 The graph shows the transmittance versus wavelength for the above conditions in Data Example 3.

[0085] Figure 7 The ambient light transmittance of the grating region without an optical film layer in Example 3 is shown in the data (see Example 3). Figure 7 The curve with "no film layer" is the same as in data example 1, and will not be repeated here.

[0086] In contrast, the ambient light transmittance of the grating region covered by optical film layer C (see...) Figure 7 The uniformity and average transmittance of the "concave hole" in the middle curve are significantly improved, with the average transmittance increasing to about 94%, and the uniformity of transmittance in the visible light wavelength range is greatly improved.

[0087] (Data Example 4)

[0088] In Example 4, simulation calculations were used to compare and analyze the ambient light transmittance under the following different conditions when the unit structure of the diffraction relief structure is a raised structure:

[0089] (1) Grating region without optical coating;

[0090] (2) The grating region covered by the optical film layer C, wherein the optical film layer C is a multilayer structure, including a filling structure C1 and a composite layer C2, and the refractive index of the filling structure C1 is n1 = (n0 + n g ) / 2 = 1.45, overflow layer C 11 The thickness d1 = 36 nm, and the refractive index n of the lower film in composite layer C2 is... 21 =1.9, thickness d 21 =20, the refractive index n of the upper film layer 22 =1.45, thickness d 22 =30;

[0091] (3) The non-grating region covered by the optical film C, wherein the optical film C has the same structure and parameters as in item (2).

[0092] Figure 8 The graphs showing the transmittance versus wavelength for the various cases mentioned above in Data Example 4 are shown.

[0093] Figure 8 The ambient light transmittance of the grating region without an optical film layer in Example 4 is shown in the data (see Example 4). Figure 8 The curve with "no film layer" is the same as in data example 1, and will not be repeated here.

[0094] In contrast, the ambient light transmittance of the grating region covered by the multilayer optical film layer C (see...) Figure 8 The uniformity and average transmittance of the medium curve (multi-layer) are greatly improved, with the average transmittance increasing to about 97%, and the uniformity of transmittance in the visible light wavelength range is greatly improved.

[0095] Ambient light transmittance in the non-grating region covered by the multilayer optical film layer C (see...) Figure 8 The transmittance of the medium curve (multi-layer non-grating region) is further improved compared to the non-grating region without a film layer, with the average transmittance increasing to about 98%.

[0096] The diffractive waveguide according to embodiments of the present invention has been described above. According to embodiments of the present invention, an augmented reality display device is also provided, which includes a lens comprising the diffractive waveguide described above. Preferably, the augmented reality display device is a near-eye display device and further includes a frame for holding the lens close to the eye.

[0097] Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-mentioned technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-mentioned technical features or their equivalent features without departing from the inventive concept. For example, technical solutions formed by substituting the above-mentioned features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A diffractive waveguide for augmented reality displays, comprising a waveguide substrate and a first grating and a second grating disposed on the waveguide substrate, the first grating being configured to couple input light carrying image information into the waveguide substrate and propagate it through total internal reflection, the second grating comprising a diffraction relief structure configured to at least dilate the pupil of light propagating therein. in, The diffractive waveguide further includes an optical film layer that at least covers the second grating and includes a filling structure. This filling structure fills the gaps in the diffraction relief structure of the second grating and forms an overflow layer that extends beyond the diffraction relief structure. The filling structure has a first refractive index n1, where n0 satisfies... <n1<n g And (n0+n g ) / 3 <n1<2(n0+n g ) / 3, where n o Let n be the refractive index of the ambient medium. g The refractive index of the second grating is denoted by ; and The thickness of the overflow layer is d1, 3.5 nm. <d1<400nm。 2. The diffractive waveguide as described in claim 1, wherein, The second grating is a two-dimensional coupling grating, configured to expand the pupil of light from the first grating and couple it out of the waveguide substrate to achieve image display.

3. The diffractive waveguide of claim 1, further comprising a third grating disposed on the waveguide substrate, the third grating comprising a diffraction relief structure configured to at least dilate the pupil of light propagating therein, wherein: One of the second grating and the third grating is a deflection grating, and the other is a coupling grating. The deflection grating is used to dilate the light from the first grating while deflecting the light to propagate toward the coupling grating. The coupling grating is used to dilate the light propagating therein and couple it out of the waveguide substrate to achieve image display.

4. The diffractive waveguide as described in claim 3, wherein, The optical film layer also covers the third grating, and the filling structure fills the gaps in the diffraction relief structure of the third grating and forms an overflow layer that creates the diffraction relief structure, wherein: n1 <n g ', where n g ' is the refractive index of the third grating.

5. The diffractive waveguide as described in claim 1, wherein, The optical film layer does not cover the first grating.

6. The diffractive waveguide as described in claim 1, wherein, The optical film layer also covers the waveguide substrate surrounding the second grating.

7. The diffractive waveguide as described in any one of claims 1-6, wherein, 2(n0+n g ) / 5 <n1<3(n0+n g ) / 5.

8. The diffractive waveguide as described in any one of claims 1-6, wherein, 30nm <d1<200nm。 9. The diffractive waveguide as described in any one of claims 1-6, wherein, The optical film layer further includes at least one composite layer covering the filling structure. Each composite layer includes a lower film layer and an upper film layer covering the lower film layer. The lower film layer has a lower refractive index that is greater than the refractive index of the material of the structure covered by the lower film layer. The upper film layer has an upper refractive index that is less than the lower refractive index.

10. The diffractive waveguide as described in claim 9, wherein, The thickness of the lower film layer is d. 21 The thickness of the upper film layer is d. 22 And 3.5nm <d 21 <400nm, 3.5nm <d 22 <400nm.

11. The diffractive waveguide as described in claim 10, wherein, The composite layer satisfies at least one of the following conditions: 20nm <d 21 <200nm; and 30nm<d 22 <200nm。 12. An augmented reality display device, comprising a lens, the lens comprising a diffractive waveguide as claimed in any one of claims 1-11.

13. The augmented reality display device of claim 12, wherein, The augmented reality display device is a near-eye display device and also includes a frame for holding the lens close to the eye.

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