Coupling-out grating and manufacturing method thereof, diffraction optical waveguide and augmented reality equipment

Abstract

The invention relates to the technical field of augmented reality equipment, and provides a coupling-out grating and a manufacturing method thereof, a diffraction optical waveguide and augmented reality equipment. The coupling-out grating comprises a plurality of gratings, a light absorbing material and an antireflection film; the plurality of gratings are configured to be arranged in an array in a coupling-out area of the optical waveguide piece, and a grating groove is defined by any two adjacent gratings and the optical waveguide piece; the bottom of at least one grating groove is filled with the light absorption material, and an air cavity is formed between the notch of the grating groove and the light absorption material; the antireflection film is arranged on the top surfaces of the plurality of gratings, and the optical parameters of the antireflection film are changed in a gradient manner along the extension direction of the coupling-out area. According to the coupling-out grating disclosed by the invention, the inhibition effect of the coupling-out grating on rainbow lines can be improved based on the synergistic effect of the antireflection film, the light absorption material and the air cavity, and the brightness loss of the coupling-out grating on light rays is also reduced while the rainbow lines are effectively inhibited.

Description

Technical Field

[0001] This invention relates to the field of augmented reality device technology, and in particular to a coupling grating and its fabrication method, a diffractive waveguide, and an augmented reality device. Background Technology

[0002] Augmented reality (AR) is a technology that merges the real world with virtual information. An AR display system typically includes an optical engine and a diffractive waveguide. The optical engine provides virtual content for the AR display system. This virtual content is projected into the human eye through a coupling grating on the diffractive waveguide. The user can also see the real world through the coupling area where the coupling grating is located.

[0003] Due to the presence of strong light from the surrounding environment, such as sunlight and artificial light, diffraction occurs at the coupling region of the diffractive waveguide, causing rainbow patterns to appear in the human eye's field of vision, severely affecting the perception of the real world. To suppress rainbow patterns, current methods mostly involve coating the surface of the coupling grating with an anti-reflection film and adjusting the structure of the coupling grating. However, in practical applications, it has been found that existing solutions achieve a rainbow pattern suppression rate of less than 30%, and instead result in significant brightness loss of the coupled light rays through the coupling grating, making it difficult for products to meet the demands of consumer-grade mass production. Summary of the Invention

[0004] This invention provides a coupling grating and its fabrication method, a diffractive waveguide, and an augmented reality device, to at least solve or improve the problem that existing coupling gratings have poor suppression effects on rainbow patterns, and that suppressing rainbow patterns inevitably sacrifices the brightness of the coupled light.

[0005] This invention provides a coupling grating, comprising: Multiple gratings are configured to be arrayed in the coupling region of an optical waveguide, and a grating groove is formed between any two adjacent gratings and the optical waveguide. A light-absorbing material is filled into the bottom of at least one of the grating grooves, and an air cavity is formed between the groove opening of the grating groove and the light-absorbing material; An antireflective coating is disposed on the top surface of the plurality of gratings, and the optical parameters of the antireflective coating vary in a gradient along the extension direction of the coupling region.

[0006] According to the present invention, the antireflective film has a reflectivity of no more than 2.5% for ambient light and the brightness loss of the coupling grating does not exceed 5%.

[0007] According to the present invention, the antireflective coating has a reflectivity of 1.5% to 2.5% for ambient light of 400-450nm with an incident angle of not less than 40°.

[0008] According to a coupling grating provided by the present invention, the optical parameters of the antireflection film vary in a gradient along the extension direction of the coupling region, including: Along the direction from the center region to the edge region of the coupling region, the thickness of the antireflective film gradually increases and / or the refractive index of the antireflective film gradually decreases.

[0009] According to the present invention, when the thickness of the antireflection film gradually increases along the direction from the central region to the edge region, the thickness of the antireflection film in the central region corresponding to the coupling region is 100~120nm, and the thickness of the antireflection film in the edge region corresponding to the coupling region is 160~170nm.

[0010] According to the present invention, when the refractive index of the antireflective film gradually decreases along the direction from the central region to the edge region, the refractive index of the antireflective film in the central region corresponding to the coupling region is 1.66~1.73, and the refractive index of the antireflective film in the coupling region is 1.4~1.52.

[0011] According to the present invention, in a coupling grating, the light-absorbing material fills the grating groove to a depth of 40% to 65% of the groove depth. And / or, the light-absorbing material includes any one of carbon black, black photoresist, chromium metal, or chromium oxide.

[0012] According to the present invention, a coupling grating further includes a transparent protective film disposed on the surface of the antireflective film.

[0013] The present invention also provides a method for fabricating the coupling grating as described above, comprising: Multiple gratings arranged in an array are set in the coupling region of the optical waveguide; An antireflection coating is deposited on the top surface of the plurality of gratings such that the optical parameters of the antireflection coating vary in a gradient along the extension direction of the coupling region; A light-absorbing material is filled to the bottom of at least one of the grating slots, and an air cavity is formed between the slot opening of the grating slot and the light-absorbing material.

[0014] According to a coupling grating provided by the present invention, the step of depositing an antireflection film on the top surface of a plurality of gratings, such that the optical parameters of the antireflection film vary in a gradient along the extension direction of the coupling region, includes: The antireflection film is deposited using a tilted vapor deposition process or a mask magnetron sputtering process to achieve a gradual increase in the thickness of the antireflection film and / or a gradual decrease in the refractive index of the antireflection film along the direction from the center region to the edge region of the coupling region.

[0015] The present invention also provides a diffractive optical waveguide, comprising: an optical waveguide element, a coupling grating, and a coupling output grating as described above; The coupling grating is disposed in the coupling region of the optical waveguide, and the coupling grating is disposed in the coupling region of the optical waveguide.

[0016] The present invention also provides an augmented reality device, including the coupling grating as described above, or including the diffractive waveguide as described above.

[0017] The coupling grating and its fabrication method, diffractive waveguide, and augmented reality device provided by this invention, by setting an antireflective film with optical parameters that vary gradient along the extension direction of the coupling region on the top surface of each grating, filling the grating slots between adjacent gratings with light-absorbing material, and reserving an air cavity, can ensure that the antireflective film maintains a low reflectivity for ambient light incident at different angles at each position based on the gradient design of the antireflective film, reducing rainbow patterns caused by ambient light reflection. Furthermore, based on the selective absorption of zero-order light in the coupling grating by the light-absorbing material, rainbow patterns caused by zero-order light interference are reduced. At the same time, based on the design of the air cavity between the grating slot opening and the light-absorbing material, the grating structure reduces the obstruction of effective diffracted light, ensuring that a large amount of ambient light can pass through the coupling grating to reach the human eye. This synergistic effect of the antireflective film, light-absorbing material, and air cavity significantly improves the rainbow suppression effect of the coupling grating, effectively suppressing rainbow patterns while also reducing the brightness loss of light caused by the coupling grating. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the main view structure of the coupling grating provided by the present invention.

[0020] Figure 2 This is a three-dimensional structural schematic diagram of the coupling grating provided by the present invention.

[0021] Figure 3 This is a simulation diagram of the diffraction angle under different ambient light angles, obtained by simulating a coupled grating with a grating period of 300nm in the existing technology, which can be received by the human eye.

[0022] Figure 4 This is the second simulation diagram of a coupled grating with a grating period of 300nm in the existing technology, which can be received by the human eye under different ambient light angles.

[0023] Figure 5 This is the third simulation diagram of a coupled grating with a grating period of 300nm in the existing technology, which shows the diffraction angles under different ambient light angles that can be received by the human eye.

[0024] Figure 6 This is a simulation curve of the reflectance of the antireflective film with gradient variation provided by the present invention and the uniform coating in the prior art under different ambient light angles.

[0025] Figure 7 This is a simulation diagram of the three-dimensional thickness distribution of the antireflective film provided by the present invention, in which the thickness of the antireflective film gradually increases and the refractive index of the antireflective film gradually decreases along the direction from the center region to the edge region of the coupling region.

[0026] Figure 8 This is a simulation diagram of the three-dimensional thickness distribution of the antireflection membrane provided by the present invention, where the thickness of the antireflection membrane gradually increases along the direction from the center region to the edge region of the coupling region.

[0027] Figure 9 This is a schematic flowchart of the method for fabricating the coupling grating provided by the present invention.

[0028] Figure 10 This is a schematic diagram of the structure of the diffractive waveguide provided by the present invention.

[0029] Figure label: 1. Coupling grating; 101. Grating groove; 11. Grating; 12. Light-absorbing material; 13. Anti-reflection coating; 2. Optical waveguide; 201. Coupling-in region; 202. Coupling-out region; 3. Coupled-in grating; 4. Optical engine; 5. Human eye; 6. Protective film. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0031] The following is combined with Figures 1-10 The present invention provides a detailed description of the coupled grating and its fabrication method, as well as the diffractive waveguide and augmented reality device, through specific embodiments and application scenarios.

[0032] In the first aspect, such as Figure 1 and Figure 2 As shown, an embodiment of the present invention provides a coupling grating 1, comprising: a plurality of gratings 11, a light-absorbing material 12, and an anti-reflection film 13; Multiple gratings 11 are configured to be arrayed in the coupling region 202 of the optical waveguide 2, and a grating groove 101 is formed between any two adjacent gratings 11 and the optical waveguide 2. The light-absorbing material 12 is filled into the bottom of at least one grating groove 101, and an air cavity is formed between the groove opening of the grating groove 101 and the light-absorbing material 12. An antireflective coating 13 is disposed on the top surface of a plurality of gratings 11, and the optical parameters of the antireflective coating 13 vary in a gradient along the extension direction of the coupling region 202.

[0033] It is understood that multiple gratings 11 can be formed in the coupling region 202 of the optical waveguide 2 by imprinting or etching. The multiple gratings 11 can be configured to be arranged in an array along the first direction so that the coupling grating 1 is a one-dimensional grating. Of course, the multiple gratings 11 can be configured to be arranged in an array along the first direction and the second direction respectively so that the coupling grating 1 is a two-dimensional grating. The first direction and the second direction are set at an angle, for example, the angle between the first direction and the second direction can be 45° to 90°.

[0034] The top surface of the grating 11 can be considered as the surface of the grating 11 facing away from the optical waveguide 2. Since the gratings 11 are separated from each other, the antireflection film 13 can be considered as including multiple film regions, which are arranged one-to-one on the top surfaces of the multiple gratings 11. The optical parameters (e.g., thickness and refractive index) of the multiple film regions change in a gradient along the extension direction of the coupling region 202. The material of the antireflection film 13 can be selected from nanoporous SiO2, MgF2 or CaF2.

[0035] The extension direction of the coupling region 202 can be from one side of the coupling region 202 to the other side of the coupling region 202, or from the central region of the coupling region 202 to the edge region; wherein, the central region of the coupling region 202 is schematically shown as Figure 1 and Figure 2 The region where coordinate point o is located is the region where the boundary line of the coupling region 202 is located.

[0036] In practical applications, by setting the optical parameters of the antireflection film 13 to vary in a gradient along the extension direction of the coupling region 202, it can be ensured that the reflectivity of ambient light incident at different angles at each position of the antireflection film 13 remains low (e.g., reflectivity not higher than 2.5%). This ensures that most of the ambient light incident at different angles at different positions of the antireflection film 13 passes directly through the antireflection film 13, rather than being reflected back into the environment for secondary incident. Based on the destructive principle of optical thin film interference (the reflected light undergoes interference with opposite phases and destructive amplitudes), it can be known that this antireflection film 13 can effectively suppress rainbow patterns caused by ambient light reflection.

[0037] Meanwhile, when ambient light is incident on the coupling grating 1, it undergoes multiple reflections / scatterings within the grating groove 101 of the coupling grating 1, forming non-zero-order diffraction (e.g., m=-1), causing rainbow patterns to be observed by the human eye. This invention fills the bottom of the grating groove 101 with light-absorbing material 12 and sets an air cavity between the groove opening of the grating groove 101 and the light-absorbing material 12. The light-absorbing material 12 can selectively absorb the zero-order light in the coupling grating 1, reducing light interference caused by the zero-order light, thereby effectively reducing rainbow patterns. Furthermore, based on the air cavity design, it ensures that the transmitted ambient light can pass through at least two gratings 11 in sequence before entering the coupling region 202 of the optical waveguide 2 and reaching the human eye. This design helps to reduce the obstruction of the effective diffracted light by the grating structure (e.g., the light-absorbing material 12), thereby suppressing rainbow patterns while also reducing the loss of brightness of the coupled light by the coupling grating 1.

[0038] The coupling grating 1 of this invention, by setting an antireflective film 13 with optical parameters gradient-varying along the extension direction of the coupling region 202 on the top surface of each grating 11, filling the grating groove 101 between adjacent gratings 11 with light-absorbing material 12, and reserving an air cavity, can ensure that the antireflective film 13 maintains a low reflectivity at each position for ambient light incident at different angles based on the gradient design of the antireflective film 13, reducing rainbow patterns caused by ambient light reflection. Furthermore, based on the light-absorbing material 12, the zero-order... Selective absorption of light reduces rainbow patterns caused by zero-order light interference. At the same time, the design of the air cavity between the slot of the grating groove 101 and the light-absorbing material 12 reduces the obstruction of the effective diffracted light by the grating structure, ensuring that a large amount of ambient light can pass through the coupling grating 1 to reach the human eye. This synergistic effect of the anti-reflection film 13, the light-absorbing material 12 and the air cavity significantly improves the rainbow suppression effect of the coupling grating 1. While effectively suppressing rainbow patterns, it also reduces the brightness loss of the imaging diffracted light caused by the coupling grating 1.

[0039] In some embodiments, the antireflective film of the present invention has a reflectivity of no more than 2.5% for ambient light and a brightness loss of no more than 5% for the coupled grating.

[0040] It is understandable that, such as Figure 1 and Figure 6 As shown, Figure 6 The diagram illustrates simulated reflectance curves of the antireflective coating with gradient variation provided by this invention and the uniform coating in the prior art under different ambient light angles. According to... Figure 6 It is known that for uniform coatings in the prior art, the reflectivity of the uniform coating to ambient light varies when ambient light is incident on it at different incident angles (e.g., 0°, 30°, or 60°), and the larger the incident angle of the ambient light, the greater the reflectivity of the uniform coating. For example, when the incident angle of the ambient light is 60°, the reflectivity of the uniform coating to ambient light reaches 4% to 4.5%.

[0041] On the contrary, according to Figure 6 It can be seen that by setting the optical parameters of the antireflective film to vary in a gradient along the extension direction of the coupling region, it can be ensured that the reflectivity of the antireflective film at each position is maintained at no more than 2.5% for ambient light incident at different angles. Furthermore, the reflectivity of the antireflective film to ambient light is less affected by the incident angle of the ambient light. For example, the reflectivity of the antireflective film to ambient light at different incident angles can be maintained between 1.5% and 2.5%.

[0042] Meanwhile, in this embodiment, light-absorbing material can be filled at the bottom of each grating groove. By setting an air cavity between the groove opening of each grating groove and the light-absorbing material, it is possible to ensure that the light-absorbing material selectively absorbs the zero-order light in the coupled grating to effectively suppress rainbow patterns. At the same time, based on the design of the air cavity, it is also possible to ensure that the light path between two adjacent gratings is not completely blocked by the light-absorbing material, so that the brightness loss of the coupled grating to the coupled light does not exceed 5%.

[0043] In some embodiments, the antireflective film of the present invention has a reflectivity of 1.5% to 2.5% for ambient light of 400-450 nm with an incident angle of not less than 40°.

[0044] Understandably, coupling gratings (such as surface relief gratings, SRGs) need to be optimized for high-efficiency first-order diffraction display effects. However, coupling gratings also work for ambient light of all wavelengths. When natural light or white light is incident on the area where the coupling grating is located at various angles, multi-order colored diffraction fringes, or rainbow patterns, are produced. Among these, the strongest and most easily detected by the human eye are often the -1st or +1st order blue-violet light.

[0045] like Figure 3 , Figure 4 and Figure 5As shown, in the prior art, the grating period of the coupling grating is set to 300nm, and the waveguide refractive index of the optical waveguide is 1.8. Simulation analysis is then performed, and different wavelengths of ambient light (e.g., wavelengths of 400nm, 520nm, and 617nm) are used to control the ambient light to be incident on the coupling grating at different angles, thus obtaining the diffraction angle received by the human eye after passing through the coupling grating. According to... Figure 3 , Figure 4 and Figure 5 As shown in the simulation diagram, the -1st order diffracted light in the short wavelength band is more easily received by the human eye, and at a larger incident angle, it will produce more severe blue rainbow patterns.

[0046] Based on this, the optical parameters of the antireflective coating are optimized in this embodiment of the invention, and simulation analysis is performed accordingly. Figure 6 It is known that when ambient light is incident at a large angle (e.g., 60°) onto an antireflective film of uniform thickness, the reflectivity of the antireflective film to ambient light will surge to 3%-5%. However, this invention sets the optical parameters of the antireflective film to vary in a gradient along the extension direction of the coupling region. For example, the thickness of the antireflective film gradually increases along the extension direction of the coupling region, and the refractive index of the antireflective film gradually decreases along the extension direction of the coupling region. When ambient light of different wavelengths (400-450nm) is incident onto the antireflective film of this invention at different incident angles, the reflectivity of the antireflective film to ambient light of 400-450nm with an incident angle of not less than 40° can be stably maintained between 1.5% and 2.5%, which can effectively suppress the rainbow pattern generated by blue-violet light when incident at a large angle.

[0047] Optionally, the antireflective coating has a reflectivity of 1.8% to 2.3% for ambient light of 400-450 nm with an incident angle of not less than 40°, for example, a reflectivity of 1.8%, 2%, 2.3% and other suitable values.

[0048] In some embodiments, such as Figure 1 and Figure 2 It is understood that the optical parameters of the antireflective coating shown in this invention exhibit a gradient change along the extension direction of the coupling region, including: Along the direction from the center region to the edge region of the coupling region, the thickness of the antireflection film gradually increases and / or the refractive index of the antireflection film gradually decreases.

[0049] In practical applications, for the gradient design of the optical parameters of antireflective coatings, the thickness of the antireflective coating can be gradually increased while the refractive index of the antireflective coating is gradually decreased.

[0050] For example, when the thickness of the antireflective film gradually increases along the direction from the central region to the edge region, the thickness of the antireflective film in the central region corresponding to the coupling region is 100~120nm, for example, the thickness of the antireflective film in the central region corresponding to the coupling region is specifically 100nm, 110nm, 120nm or other suitable values, and the thickness of the antireflective film in the edge region corresponding to the coupling region is 160~170nm, for example, the thickness of the antireflective film in the edge region corresponding to the coupling region is specifically 160nm, 165nm, 170nm or other suitable values.

[0051] For example, when the refractive index of the antireflective film gradually decreases along the direction from the central region to the edge region, the refractive index of the antireflective film in the central region corresponding to the coupling region is 1.66 to 1.73, for example, the refractive index of the antireflective film in the central region corresponding to the coupling region is specifically 1.66, 1.70, 1.73 and other suitable values, and the refractive index of the antireflective film in the coupling region is 1.4 to 1.52, for example, the refractive index of the antireflective film in the coupling region is specifically 1.4, 1.45, 1.52 and other suitable values.

[0052] In some examples, based on the coupling grating provided by this invention, a grating structure with a size of 20*12mm is used. With both the thickness and refractive index of the antireflection coating exhibiting gradient changes, the refractive index of the antireflection coating is set to a five-layer gradient n=[1.45, 1.52, 1.59, 1.66, 1.73]. The wavelength of the incident light is based on 425nm. Based on thin-film interference and TMM simulations, the following results are obtained: Figure 7 The diagram shows the membrane system design of the antireflective membrane. Among them, according to... Figure 7 It can be seen that along the direction from the center region to the edge region of the coupling region, the thickness of the antireflection film gradually increases from 120 nm to 160 nm.

[0053] At the same time, through simulation analysis, and by adopting methods such as Figure 7 Based on the structure of the antireflective film shown, it can also be concluded that under ambient light incident at angles greater than 50°, the antireflective film with gradient design of the present invention has a 40%-50% better effect on suppressing rainbow patterns than the existing antireflective film obtained by uniform coating.

[0054] In some examples, based on feasibility considerations, only the thickness of the antireflective coating is set to have a gradual gradient, without adjusting the refractive index of the antireflective coating. When simulation analysis is performed in the same manner as described above, the results are as follows: Figure 8 The diagram shows the membrane system design of the antireflective membrane. Based on... Figure 8 It can be seen that along the direction from the center region to the edge region of the coupling region, the thickness of the antireflection film gradually increases from 90 nm to 170 nm. That is, compared to... Figure 7The membrane structure shown, due to Figure 8 The antireflective coating shown does not have its refractive index gradient adjusted. Figure 8 The thickness of the antireflective coating shown has a relatively large increasing gradient to ensure a similar rainbow-like suppression effect.

[0055] At the same time, through simulation analysis, and by adopting methods such as Figure 8 Based on the structure of the antireflective film shown, it can also be concluded that under ambient light incident at angles greater than 50°, the gradient-designed antireflective film of this invention has an antireflective effect on suppressing rainbow patterns that is about 30% better than that of existing antireflective films obtained by uniform coating.

[0056] In some embodiments, such as Figure 1 and Figure 2 As shown, the filling depth of the light-absorbing material in the grating groove is 40% to 65% of the groove depth.

[0057] It is understandable that the filling depth of the light-absorbing material in the grating groove refers to the vertical distance between the top surface of the light-absorbing material and the bottom of the grating groove.

[0058] For example, the filling depth of the light-absorbing material in the grating groove can be specifically set to 40%, 50%, 60%, 65% or other suitable proportions of the groove depth of the grating groove, without being specifically limited thereto.

[0059] By setting the filling depth of the light-absorbing material in the grating groove, the zero-order transmitted light reaching the lower half of the grating groove can be absorbed by the light-absorbing material. For example, it can reduce the zero-order transmitted light in the coupled grating by more than 40%. This design not only effectively suppresses the rainbow effect caused by the interference of the zero-order transmitted light, but also allows the air cavity to account for 35%-60% of the grating groove. The air cavity can reduce the obstruction of the effective diffracted light between two adjacent gratings, ensuring that the impact on the brightness of the imaging diffracted light of the coupled grating does not exceed 5%.

[0060] In some embodiments, the light-absorbing material includes any one of carbon black, black photoresist, chromium metal, or chromium oxide.

[0061] In some embodiments, the coupling grating further includes a transparent protective film disposed on the surface of the antireflective film, which serves to protect the antireflective film.

[0062] Specifically, the transparent protective film can be made of SiO2 or Al2O3 film, and the thickness of the transparent protective film can be 300-600 nm.

[0063] In the second aspect, such as Figure 9 As shown, this embodiment of the invention also provides a method for fabricating the coupling grating as described above, comprising the following steps: Step S910: Multiple gratings arranged in an array are set in the coupling region of the optical waveguide.

[0064] Understandably, an optical waveguide component is a type of micro-nano optical element made based on the principle of optical waveguides. An optical waveguide component can be a waveguide plate, and its core function is to guide light waves to transmit with low loss within a limited space. For example, an optical waveguide component is used to enable light coupled from the input grating to propagate through the optical waveguide component to the output grating in the manner of total internal reflection.

[0065] Each grating, as a key structure of the coupling grating, can be formed in the coupling region of the optical waveguide by imprinting or etching. The shape of the grating can be rectangular, parallelogram, rhombus, etc., without specific limitations.

[0066] In step S920, an antireflection coating is deposited on the top surface of multiple gratings so that the optical parameters of the antireflection coating change in a gradient along the extension direction of the coupling region.

[0067] It is understandable that the antireflective coating is located on the side of each grating away from the optical waveguide. When depositing the antireflective coating, it is necessary to strictly control the optical parameters such as the thickness and refractive index of the antireflective coating to ensure that these optical parameters change in a gradient along the extension direction of the coupling region, so that the reflectivity of the antireflective coating at each position to ambient light incident at different angles is maintained at no more than 2.5%.

[0068] Step S930: Fill the bottom of at least one grating groove with light-absorbing material and form an air cavity between the groove opening and the light-absorbing material.

[0069] Understandably, in practical applications, light-absorbing material can be filled at the bottom of each grating groove. For example, the filling depth of the light-absorbing material in the grating groove can be 40% to 65% of the groove depth, ensuring that an air cavity is formed between the groove opening and the light-absorbing material. This design can utilize the light-absorbing material filled in the lower half of the grating groove to absorb part of the zero-order transmitted light, and combined with the air cavity retained in the upper half, reduce the obstruction of effective diffraction light, thereby suppressing rainbow patterns while reducing the impact on the brightness of the imaging diffraction light.

[0070] It should be noted that the order of steps S920 and S930 in this embodiment can be interchanged without affecting the performance of the prepared coupling grating.

[0071] As can be seen from the above, the coupling grating of the present invention, by setting an antireflective film with optical parameters that vary in gradient along the extension direction of the coupling region on the top surface of each grating, filling the grating slots between adjacent gratings with light-absorbing material, and reserving an air cavity, can ensure that the antireflective film maintains a low reflectivity for ambient light incident at different angles at each position based on the gradient design of the antireflective film, reducing rainbow patterns caused by ambient light reflection. Furthermore, based on the selective absorption of zero-order light in the coupling grating by the light-absorbing material, rainbow patterns caused by zero-order light interference are reduced. At the same time, based on the design of the air cavity between the slot opening of the grating and the light-absorbing material, the grating structure reduces the obstruction of effective diffracted light, ensuring that a large amount of ambient light can pass through the coupling grating and reach the human eye. This synergistic effect of the antireflective film, the light-absorbing material, and the air cavity significantly improves the rainbow suppression effect of the coupling grating, effectively suppressing rainbow patterns while also reducing the brightness loss of light caused by the coupling grating.

[0072] In some embodiments, the present invention involves depositing an antireflection coating on the top surface of a plurality of gratings such that the optical parameters of the antireflection coating vary in a gradient along the extension direction of the coupling region, including: Antireflective coatings are deposited using tilted vapor deposition or mask magnetron sputtering processes to achieve a gradual increase in the thickness of the antireflective coating and / or a gradual decrease in the refractive index of the antireflective coating along the direction from the center region to the edge region of the coupling region.

[0073] In the third aspect, such as Figure 10 As shown, this embodiment of the invention also provides a diffractive optical waveguide, including: an optical waveguide 2, a coupling grating 3, and a coupling output grating 1 as described above; The coupling grating 3 is disposed in the coupling region 201 of the optical waveguide 2, and the coupling grating 1 is disposed in the coupling region 202 of the optical waveguide 2.

[0074] It is understandable that, such as Figure 10 As shown, the input grating 3 and the optomechanical system 4 are arranged opposite each other, and the output grating 1 and the human eye 5 are arranged opposite each other. A protective sheet 6 is provided on the side of the optical waveguide 2 away from the human eye 5. The protective sheet 6 is transparent. A vacuum cavity is formed between the protective sheet 6 and the optical waveguide 2. Both the input grating 3 and the output grating 1 are arranged in the vacuum cavity.

[0075] In practical applications, a beam of light containing virtual content from the optical engine 4 enters the optical waveguide 2 under the coupling of the coupling grating 3. The beam is transmitted within the waveguide 2 via total internal reflection, then exits the waveguide 2 via the output grating 1, and finally reaches the human eye 5, allowing the user to receive the information output by the optical engine 4. Simultaneously, the user can also see the external environment through the output region 202 where the output grating 1 is located. This allows the user to see the real world while simultaneously observing the virtual image projected by the optical engine 4 superimposed on the real world.

[0076] In a fourth aspect, embodiments of the present invention also provide an augmented reality device, including the coupling grating as described above, or including the diffractive waveguide as described above.

[0077] Understandably, augmented reality devices can be AR glasses, which are well-known in the field.

[0078] Since the augmented reality device includes a coupling grating or a diffractive waveguide, and the specific structure of the coupling grating or diffractive waveguide is as described in the above embodiments, the augmented reality device of this embodiment includes all the technical solutions of the above embodiments. Therefore, it has at least all the beneficial effects achieved by all the technical solutions of the above embodiments, which will not be described in detail here.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A coupling grating, characterized in that, include: Multiple gratings are configured to be arrayed in the coupling region of an optical waveguide, and a grating groove is formed between any two adjacent gratings and the optical waveguide. A light-absorbing material is filled into the bottom of at least one of the grating grooves, and an air cavity is formed between the groove opening of the grating groove and the light-absorbing material; An antireflective coating is disposed on the top surface of the plurality of gratings, and the optical parameters of the antireflective coating vary in a gradient along the extension direction of the coupling region.

2. The coupling grating according to claim 1, characterized in that, The antireflective coating has a reflectivity of no more than 2.5% to ambient light, and the brightness loss of the coupled grating does not exceed 5%.

3. The coupling grating according to claim 2, characterized in that, The antireflective coating has a reflectivity of 1.5% to 2.5% for ambient light of 400-450nm with an incident angle of not less than 40°.

4. The coupling grating according to claim 1, characterized in that, The optical parameters of the antireflective film vary in a gradient along the extension direction of the coupling region, including: Along the direction from the center region to the edge region of the coupling region, the thickness of the antireflective film gradually increases and / or the refractive index of the antireflective film gradually decreases.

5. The coupling grating according to claim 4, characterized in that, As the thickness of the antireflective film gradually increases along the direction from the central region to the edge region, the thickness of the antireflective film in the central region corresponding to the coupling region is 100~120nm, and the thickness of the antireflective film in the edge region corresponding to the coupling region is 160~170nm.

6. The coupling grating according to claim 4, characterized in that, As the refractive index of the antireflective coating gradually decreases along the direction from the central region to the edge region, the refractive index of the antireflective coating in the central region corresponding to the coupling region is 1.66~1.73, and the refractive index of the antireflective coating in the coupling region is 1.4~1.

52.

7. The coupling grating according to any one of claims 1 to 6, characterized in that, The light-absorbing material fills the grating groove to a depth of 40% to 65% of the groove depth. And / or, the light-absorbing material includes any one of carbon black, black photoresist, chromium metal, or chromium oxide.

8. The coupling grating according to any one of claims 1 to 6, characterized in that, Also includes: A transparent protective film is disposed on the surface of the antireflective film.

9. A method for fabricating a coupling grating as described in any one of claims 1 to 8, characterized in that, include: Multiple gratings arranged in an array are set in the coupling region of the optical waveguide; An antireflection coating is deposited on the top surface of the plurality of gratings such that the optical parameters of the antireflection coating vary in a gradient along the extension direction of the coupling region; A light-absorbing material is filled to the bottom of at least one of the grating slots, and an air cavity is formed between the slot opening of the grating slot and the light-absorbing material.

10. The manufacturing method according to claim 9, characterized in that, The step of depositing an antireflective coating on the top surface of the plurality of gratings, such that the optical parameters of the antireflective coating vary in a gradient along the extension direction of the coupling region, includes: The antireflection film is deposited using a tilted vapor deposition process or a mask magnetron sputtering process to achieve a gradual increase in the thickness of the antireflection film and / or a gradual decrease in the refractive index of the antireflection film along the direction from the center region to the edge region of the coupling region.

11. A diffractive optical waveguide, characterized in that, include: Optical waveguide, coupling grating and output grating as described in any one of claims 1 to 8; The coupling grating is disposed in the coupling region of the optical waveguide, and the coupling grating is disposed in the coupling region of the optical waveguide.

12. An augmented reality device, characterized in that, It includes the coupling grating as described in any one of claims 1 to 8, or the diffractive waveguide as described in claim 11.

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