Diffractive optical waveguide and augmented reality display device having same

Abstract

The invention discloses a diffractive optical waveguide and augmented reality display equipment. The diffractive optical waveguide comprises a waveguide substrate and a first grating and a second grating which are arranged on the waveguide substrate, the first grating is configured to couple input light carrying image information into the waveguide substrate and enable the input light to be propagated through total reflection, and the second grating comprises a diffractive relief structure and is configured to at least carry out pupil expansion on the light propagated to the second grating; the diffraction optical waveguide further comprises an optical film layer, the optical film layer at least covers the second grating and comprises a filling structure, and the filling structure fills gaps in the diffraction relief structure of the second grating and forms an overflow layer higher than the diffraction relief structure. The refractive index of the filling structure is larger than that of the environment medium and smaller than that of the second grating. According to the embodiment of the invention, the transmittance of ambient light in the grating area can be effectively improved, and the difference between the grating area and the non-grating area is reduced, so that the overall visual experience is improved.

Description

Technical Field

[0001] The present invention relates to a display technology based on a diffraction optical waveguide; in particular, to a diffraction optical waveguide device for augmented reality display and a display device having the same. Background Art

[0002] Augmented reality (AR) display technology is slowly becoming popular as a very smart and portable display technology. Display technology based on diffraction optical waveguides is one of the mainstream solutions for realizing augmented reality display. A waveguide grating is arranged on a waveguide substrate, and the waveguide grating includes an in-coupling grating and an out-coupling grating. The in-coupling grating receives input light carrying image information from an optical machine and couples it into the waveguide substrate; the out-coupling grating propagates and expands the light carrying image information while coupling the light out of the waveguide substrate to form an out-coupling light field. The eyes receive the light from the out-coupling light field, so that, for example, the image carried by the incident light can be observed.

[0003] Diffractive waveguides have the advantages of being thin, light, capable of expanding pupils, and easy to mass produce, and have become the core components of augmented reality display devices. However, diffractive waveguides are not without disadvantages. In particular, how to make diffractive waveguides more suitable for the needs of augmented reality display remains to be explored. Summary of the invention

[0004] An object of the present invention is to provide a diffractive optical waveguide device for augmented reality display and a display device having the same, which at least partially overcome the problems in the prior art.

[0005] According to one aspect of the present invention, a diffractive optical waveguide for augmented reality display is provided, comprising a waveguide substrate and a first grating and a second grating arranged on the waveguide substrate, wherein the first grating is configured to couple input light carrying image information into the waveguide substrate and propagate it through total reflection, and the second grating comprises a diffractive relief structure configured to at least expand the pupil of the light propagated therein. The diffractive optical waveguide also comprises an optical film layer, which at least covers the second grating and comprises a filling structure, which fills the gap in the diffractive relief structure of the second grating and forms an overflow layer higher than the diffractive relief structure, and the filling structure has a first refractive index n1, wherein: n0 satisfies: <n1<n g , where n o is the refractive index of the ambient medium, n g is the refractive index of the second grating.

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

[0007] In some embodiments, the diffraction optical waveguide also includes a third grating disposed on the waveguide substrate, the third grating including a diffraction relief structure, configured to at least expand the pupil of light propagating therein, wherein: one of the second grating and the third grating is a turning grating, and the other is a coupling-out grating, the turning grating is used to deflect the light from the first grating while expanding the pupil to propagate toward the coupling-out grating, and the coupling-out grating is used to expand the pupil of the light propagating therein and couple it out of 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 out of 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 around 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 overflow layer has a thickness of d1 and is 3.5 nm. <d1<400nm。

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

[0015] Advantageously, the optical film layer also 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 material refractive index 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 present invention, an augmented reality display device is provided. The augmented reality display device includes a lens, and the lens includes the diffractive optical waveguide as described above.

[0021] Advantageously, the augmented reality display device is a near-eye display device and further comprises a frame for holding the lenses close to the eyes.

[0022] In the diffraction light waveguide according to the embodiment of the present invention, an optical film layer is provided, and in the grating area of ​​at least part of the grating, a material having a refractive index within a predetermined range is used to fill the gaps in the relief structure of the grating and form an overflow layer, so as to improve the transmittance of ambient light in the grating area and reduce the difference between the grating area and the non-grating area, thereby improving the overall visual experience of the diffraction light waveguide when used for augmented reality display. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0024] Figure 1 is 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 covered on a second grating in a diffractive optical waveguide according to an embodiment of the present invention is schematically shown;

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

[0027] Figure 4 Schematic planes of different examples of diffractive optical waveguides according to embodiments of the present invention, wherein the diffractive optical waveguides have different grating configurations;

[0028] Figure 5 A graph showing the variation of transmittance with wavelength in Data Example 1 is shown;

[0029] Figure 6 A graph showing the variation of transmittance with wavelength in Data Example 2 is shown;

[0030] Figure 7 A graph showing the variation of transmittance with wavelength in Data Example 3; and

[0031] Figure 8 A graph showing the variation of transmittance with wavelength in Data Example 4 is shown. DETAILED DESCRIPTION

[0032] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It will be appreciated that the specific embodiments described herein are only used to explain the relevant inventions, rather than to limit the invention. For ease of description, only the parts related to the invention are shown in the accompanying drawings. It should be noted that, in the absence of conflict, the embodiments in this application and the features in the embodiments may 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 introduced. Figure 1 FIG. 1 is a schematic cross-sectional view of a diffractive optical waveguide according to an embodiment of the present invention. Figure 1 As shown, the diffraction optical waveguide 1 includes a waveguide substrate 1a and a first grating 10 and a second grating 20 arranged on the waveguide substrate 1a; according to an embodiment of the present invention, the diffraction optical waveguide 1 also includes an optical film layer C, which at least covers the second grating 20.

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

[0035] The second grating 20 comprises a diffractive relief structure 20a (see Figure 2 and Figure 3 ), and is configured to at least expand the pupil of the light propagating therein, for example, to expand the pupil of the light in one dimension or two dimensions along the plane of the waveguide substrate 1a. The second grating 20 can also be called a pupil expander. Both the outcoupling grating and the turning grating in the diffraction light waveguide belong to the pupil expander. The second grating in the diffraction light waveguide according to the embodiment of the present invention can be an outcoupling grating or a turning grating. This will be described in more detail below.

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

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

[0038] exist Figure 2 In the example shown, the optical film layer C includes a filling structure C1, which fills the gaps in the diffraction relief structure 20a of the second grating 20 and forms an overflow layer C1 higher than the diffraction relief structure 20a. In the present application, the "overflow layer" refers to a portion of the filling structure that exceeds 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 to have a flat surface. However, in some cases, due to the optical film manufacturing process, or due to the influence of the shape of the diffractive relief structure of the underlying layer, the surface of the overflow layer may have slight undulations, such as 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 optical waveguide according to the 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 the 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 diffractive relief structure 20a of the second grating 20. In order to enable the diffractive optical waveguide according to the embodiment of the present invention to achieve the same or similar effect for ambient light in a visible light wavelength range as wide as possible, the refractive index at a wavelength of 589nm (yellow light) is selected in the present application to examine whether various refractive index relationships are satisfied. That is, according to the embodiment of the present invention, the filling structure C1 has a first refractive index n1, which satisfies: n0 <n1<n g , where n o is the refractive index of the environment medium surrounding the second grating 20 and the waveguide substrate 1a, n g is the refractive index of the diffractive relief structure 20 a of the second grating 20 .

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

[0041] In the diffractive optical waveguide for augmented reality display according to the embodiment of the present invention, by providing an optical film layer, in the grating area (see Figure 1 The area I shown in the figure uses a refractive index within a predetermined range (a first refractive index n1, satisfying n0 <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 area II shown), enabling the user to obtain a more natural visual experience when observing the environment through the diffractive optical waveguide 1. In summary, the diffractive optical waveguide according to the embodiments 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 embodiments 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 , where the first layer C 21 With a refractive index of n 21 , refractive index n 21 Greater than the first layer C 21 The material refractive index n1 of the covered filling structure C1, the second layer C 22 With a refractive index of 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 composite layer being composed of a lower film layer (first layer) having a relatively high refractive index and an upper film layer (second layer) having 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 (such as a filling structure or an upper film layer of another composite layer).

[0049] The thickness of the lower film layer is d 21 , the thickness of the upper film layer is d 22 According to different embodiments of the present invention, the thickness of the composite layer may 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 invention is described in connection with diffractive optical waveguides having different grating configurations. Figure 4 Different examples of diffractive optical waveguides with different grating configurations according to embodiments of the present invention are shown in schematic plan views.

[0051] Figure 4 Figure (a) shows a diffraction optical waveguide 100 according to an embodiment of the present invention, wherein the diffraction optical waveguide 100 comprises a waveguide substrate 100a and an in-coupling grating 110 and an out-coupling grating 120 disposed on the waveguide substrate 100a, wherein the in-coupling grating 110 is configured to couple input light carrying image information into the waveguide substrate 100a and propagate it through total reflection, and the out-coupling grating 120 comprises a diffraction relief structure, configured to expand the pupil of the light propagated therein while coupling it out of the waveguide to realize image display. In the diffraction optical waveguide 100, an optical film layer C covers the out-coupling grating.

[0052] Figure 4Figure (b) shows a diffraction optical waveguide 200 according to an embodiment of the present invention, which includes a waveguide substrate 200a and an in-coupling grating 210, an out-coupling grating 220 and a turning grating 230 disposed on the waveguide substrate 200a, wherein the functions of the in-coupling grating 210 and the out-coupling grating 220 are similar to the in-coupling grating 110 and the out-coupling grating 120 shown in Figure (a), and the turning grating is configured to dilate the pupil of the light from the in-coupling grating 210 while deflecting the light to propagate toward the out-coupling grating 220. The turning grating 230 includes a diffraction relief structure for realizing the above functions. In the diffraction optical waveguide 200, an optical film layer C covers both the out-coupling grating 220 and the turning grating 230.

[0053] In the case where 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 relative to one of the gratings (i.e., the second grating). Figure 2 Introduction to refractive index n0, n1, n g The relationship between the two gratings also satisfies a similar relationship with respect to the other 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) shows a diffraction optical waveguide 300 according to an embodiment of the present invention, which has the same grating configuration as the diffraction optical waveguide 200 shown in Figure (b) (i.e., the diffraction optical waveguide 300 includes a waveguide substrate 300a and an in-coupling grating 310, an out-coupling grating 320 and a turning grating 330 disposed on the waveguide substrate 300a), except that: in the diffraction optical waveguide 300, the optical film layer C covers the turning grating 330, but not the out-coupling grating 320. Although not shown in the figure, those skilled in the art can understand based on 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 out-coupling grating 320, but not the turning grating 330.

[0055] According to a preferred embodiment of the present invention, Figure 4As shown in the middle figure (b), the optical film layer C also covers the waveguide substrate around the out-coupling grating 220 and the turning grating 230. Preferably, the optical film layer C can advantageously cover the entire non-grating area. Diffraction light waveguides usually use waveguide substrates with high refractive indexes, which is beneficial to expand the field of view of the image display, but it also causes the surface of the waveguide substrate to have a high reflectivity for ambient light. By providing the optical film layer C in the non-grating area, it can help improve the transmittance of ambient light in the non-grating area, thereby further improving the overall visual experience of the diffraction light waveguide for the user. In addition, since the optical film layer C covers almost the entire area of ​​the diffraction light waveguide (in some cases, the in-coupling grating is not covered), it is easy to manufacture and helps to reduce manufacturing costs.

[0056] In some cases, since the coupling grating is packaged to better receive input light from the optical machine, the optical film layer C can advantageously cover all regions of the waveguide substrate 200a except the coupling grating 210. In other cases, the coupling grating is covered with a light shielding layer such as a metal, and the optical film layer C proposed according to the embodiment of the present invention can also be applied to the region of the coupling grating during the manufacturing process. This can simplify the manufacturing process without affecting the performance of the coupling grating.

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

[0058] (Data Example 1)

[0059] In Data Example 1, the ambient light transmittance under the following different situations is compared and analyzed by simulation calculation when the unit structure in the diffraction relief structure is a convex structure:

[0060] (1) Grating area without optical film layer;

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

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

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

[0064] (5) Non-grating area without optical film layer.

[0065] Figure 5 A graph showing the variation of transmittance with wavelength in the above various situations in Data Example 1 is shown.

[0066] like Figure 5 As shown in Figure , the ambient light transmittance of the grating area without optical coating (see Figure 5 The middle curve "no film layer" varies greatly in the visible light wavelength range, that is, the uniformity is poor, the average transmittance is about 80%, and the ambient light transmittance of the non-grating area without an optical film layer (see Figure 5 The middle curve ("no film layer in non-grating area") has very good uniformity, 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 in the grating area covered by the optical film layer C are significantly improved, where: n1 = 2 (n0 + n g ) / 5=1.16 (see Figure 5 The middle curve "150nm 2 / 5"), the average transmittance is increased to about 89%; n1 = 3 (n0 + n g ) / 5=1.74(see Figure 5 The middle curve "10nm 3 / 5"), the average transmittance is increased to about 88%; n1 = (n0 + n g ) / 2=1.45(see Figure 5 The middle curve "150nm 1 / 2"), the average transmittance is increased to about 92.7%. It can be seen that n1 = (n0 + n g ) / 2, the average transmittance of the grating area is optimal. Figure 5 As can be seen from the curve shown in the figure, n1=(n0+n g ) / 2, the uniformity of the transmittance of the grating area in the visible light wavelength range is greatly improved.

[0068] (Data Example 2)

[0069] In Data Example 2, the ambient light transmittance under the following different situations is compared and analyzed by simulation calculation when the unit structure in the diffraction relief structure is a convex structure:

[0070] (1) Grating area without optical film layer;

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

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

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

[0074] (5) Non-grating area without optical film layer.

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

[0076] Figure 6 A curve chart showing the variation of transmittance with wavelength in the above various situations in Data Example 2 is shown.

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

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

[0079] (Data Example 3)

[0080] In Data Example 3, the ambient light transmittance under the following different situations is compared and analyzed by simulation calculation when the unit structure in the diffraction relief structure is a concave hole structure:

[0081] (1) a 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, wherein the refractive index of the filling structure C1 is n1=(n0+n g ) / 2=1.45, overflow layer C 11 The thickness d1 = 50nm.

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

[0084] Figure 7 A graph showing changes in transmittance with wavelength in the above case in Data Example 3 is shown.

[0085] Figure 7 The ambient light transmittance of the grating area without an optical film layer in the data example 3 is shown (see Figure 7 The middle curve ("without film layer") is the same as that in Data Example 1 and will not be described again here.

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

[0087] (Data Example 4)

[0088] In Data Example 4, the ambient light transmittance under the following different situations is compared and analyzed by simulation calculation when the unit structure in the diffraction relief structure is a convex structure:

[0089] (1) Grating area without optical film layer;

[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 + n2 g ) / 2=1.45, overflow layer C 11 The thickness d1 = 36nm, the refractive index n of the lower film layer in the composite layer C2 21 =1.9, thickness d 21 =20, the refractive index of the upper film layer n 22 =1.45, thickness d 22 =30;

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

[0092] Figure 8 A graph showing the variation of transmittance with wavelength in the above various situations in Data Example 4 is shown.

[0093] Figure 8 The ambient light transmittance of the grating area without an optical film layer in the data example 4 is shown (see Figure 8 The middle curve ("without film layer") is the same as that in Data Example 1 and will not be described again here.

[0094] In contrast, the ambient light transmittance of the grating area covered by the optical film layer C of the multilayer structure (see Figure 8 The uniformity and average transmittance of the middle curve "multilayer" are greatly improved, with the average transmittance increased to about 97%, and the uniformity of the transmittance in the visible light wavelength range is greatly improved.

[0095] The ambient light transmittance of the non-grating area covered by the optical film layer C of the multi-layer structure (see Figure 8 The transmittance of the middle curve "multilayer non-grating area" is also further improved compared to the non-grating area without a film layer, with the average transmittance increased to about 98%.

[0096] The above describes a diffractive optical waveguide according to an embodiment of the present invention. According to an embodiment of the present invention, an augmented reality display device is also provided, which includes a lens, and the lens includes the diffractive optical waveguide as described above. Preferably, the augmented reality display device is a near-eye display device and also 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 the technical solutions formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A diffractive optical waveguide for augmented reality display, comprising a waveguide substrate and a first grating and a second grating disposed on the waveguide substrate, wherein the first grating is configured to couple input light carrying image information into the waveguide substrate and propagate it through total reflection, and the second grating comprises a diffractive relief structure configured to at least expand the pupil of the light propagating therein, in, The diffractive optical waveguide further comprises an optical film layer, which at least covers the second grating and comprises a filling structure, which fills the gaps in the diffractive relief structure of the second grating and forms an overflow layer higher than the diffractive relief structure, and the filling structure has a first refractive index n1, wherein: n0 <n1<n g , where n o is the refractive index of the ambient medium, n g is the refractive index of the second grating.

2. The diffractive optical waveguide according to claim 1, wherein: The second grating is a two-dimensional outcoupling grating, which is configured to expand the pupil of the light from the first grating and couple it out of the waveguide substrate to achieve image display.

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

4. The diffractive optical waveguide according to claim 3, wherein: 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 of the diffraction relief structure, and wherein: n1 <n g ', where n g ' is the refractive index of the third grating.

5. The diffractive optical waveguide according to claim 1, wherein: The optical film layer does not cover the first grating.

6. The diffractive optical waveguide according to claim 1, wherein: The optical film layer also covers the waveguide substrate around the second grating.

7. The diffractive optical waveguide according to any one of claims 1 to 6, wherein: (n0+n g ) / 3 <n1<2(n0+n g ) / 3.

8. The diffractive optical waveguide according to claim 7, wherein: 2(n0+n g ) / 5 <n1<3(n0+n g ) / 5.

9. The diffractive optical waveguide according to any one of claims 1 to 6, wherein: The thickness of the overflow layer is d1,3.5nm <d1<400nm。 10. The diffractive optical waveguide according to claim 9, wherein: 30nm <d1<200nm。 11. The diffractive optical waveguide according to any one of claims 1 to 6, wherein: The optical film layer also 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 lower refractive index, which is greater than the material refractive index of the structure covered by the lower film layer, and the upper film layer has an upper refractive index, which is less than the lower refractive index.

12. The diffractive optical waveguide according to claim 10, 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.

13. The diffractive optical waveguide according to claim 12, wherein: The composite layer satisfies at least one of the following conditions: 20nm <d 21 <200nm; and 30nm<d 22 <200nm。 14. An augmented reality display device, comprising a lens, wherein the lens comprises the diffractive optical waveguide according to any one of claims 1 to 13.

15. The augmented reality display device according to claim 14, 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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