Interference fringe optimization structure in diffraction optical waveguide and augmented reality equipment

Abstract

The utility model discloses an interference fringe optimization structure in a diffraction optical waveguide and augmented reality equipment, the diffraction optical waveguide comprises a waveguide substrate, and the waveguide substrate is provided with a grating area and a non-grating area; the non-grating area is provided with an antireflection film; the included angle between the plane where the side wall of the anti-reflection film is located and the plane where the waveguide substrate is located is a first preset angle, the first preset angle alpha is an acute angle, and # imgabs0 # L is smaller than 20 microns; wherein lambda is the wavelength of the coherent light, L is the distance between two adjacent interference fringes, and n is the medium refractive index between the plane where the side wall of the antireflection film is located and the plane where the waveguide substrate is located. By means of the structure, interference fringes caused by wedge interference formed between the plane where the side wall of the antireflection film is located and the plane where the waveguide substrate is located are effectively optimized, normal transmission of ambient light is guaranteed, and user experience is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of diffractive optical waveguides, in particular to an optimized structure of interference fringes in a diffractive optical waveguide and an augmented reality device. Background Art

[0002] A diffractive optical waveguide is a transparent display based on optical waveguide technology, which realizes the transmission and display of images by using the diffraction principle of light. When common diffractive optical waveguides are antireflection-coated, in order not to affect the diffraction efficiency of the grating area, an antireflection film is deposited in the non-grating area to increase the transmission of external ambient light without affecting the optical efficiency of the grating area.

[0003] Generally, there is an included angle between the antireflection film deposited in the non-grating area and the waveguide substrate of the diffractive optical waveguide, so that a wedge structure is formed between the plane where the side wall of the antireflection film is located and the plane where the waveguide substrate is located. When light passes through this wedge structure, wedge interference will occur, generating bright and dark interference fringes. The generation of these interference fringes will affect the human eye's observation of external ambient light, reduce the display performance of the augmented reality device, and degrade the user experience. Summary of the Utility Model

[0004] The utility model provides an optimized structure of interference fringes in a diffractive optical waveguide and an augmented reality device. By setting the spacing of the interference fringes according to the human eye's resolution ability of the interference fringe spacing, the edge of the antireflection film coating area is optimized, effectively eliminating the interference fringes caused by the wedge interference formed between the plane where the side wall of the antireflection film is located and the plane where the waveguide substrate is located, ensuring the normal transmission of ambient light, and improving the user experience.

[0005] In a first aspect, the utility model provides an optimized structure of interference fringes in a diffractive optical waveguide, including a waveguide substrate, on which a grating area and a non-grating area are provided; an antireflection film is provided in the non-grating area;

[0006] The included angle between the plane where the side wall of the antireflection film is located and the plane where the waveguide substrate is located is a first preset angle. The first preset angle α is an acute angle and satisfies: L < 20um;

[0007] where λ is the wavelength of coherent light, L is the spacing between adjacent two interference fringes, and n is the refractive index of the medium between the plane where the side wall of the antireflection film is located and the plane where the waveguide substrate is located.

[0008] Optionally, α > 80°.

[0009] Optionally, the antireflection film partially covers the grating area, and the distance D1 between the point on the side wall of the antireflection film closest to the grating area and the grating area satisfies: D1 < 10um.

[0010] Optionally, there is a gap between the antireflection film and the grating region, and the gap D2 between the closest point of the side wall of the antireflection film to the grating region and the grating region satisfies: D2 < 0.4um.

[0011] Optionally, there is a gap between the antireflection film and the grating region, and a filling material is disposed in the gap, and the refractive index of the filling material is between the refractive index of the antireflection film and the refractive index of the grating region.

[0012] Optionally, the refractive index of the antireflection film is less than the refractive index of the grating region.

[0013] Optionally, the grating region includes at least an input region and an output region, and grating structures are provided in both the input region and the output region.

[0014] Optionally, the plane where the side wall of the antireflection film is located faces at least the output region, and the included angle between the plane where the side wall of the antireflection film is located and the plane where the waveguide substrate is located is a first preset angle.

[0015] Optionally, the grating structure in the input region is one of a straight grating, an inclined grating, a blazed grating or a two-dimensional grating; the grating structure in the output region is one of a straight grating, an inclined grating, a blazed grating or a two-dimensional grating.

[0016] In a second aspect, the present utility model provides an augmented reality device, including an optical engine and the interference fringe optimization structure in the diffraction optical waveguide described above.

[0017] According to the technical solution of the present utility model, by setting that there is a first preset angle between the plane where the side wall of the antireflection film is located and the plane where the waveguide substrate is located, and the first preset angle is an acute angle, when the first preset angle satisfies L < 20um, the interference fringes caused by the wedge interference formed between the plane where the side wall of the antireflection film is located and the plane where the waveguide substrate is located can be effectively eliminated, enabling the human eye to recognize the interference fringes as bright bands with uniform color, while ensuring the normal transmission of external environmental light and improving the user experience.

[0018] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present utility model, nor is it used to limit the scope of the present utility model. Other features of the present utility model will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0020] Figure 1Schematic structural diagram of a diffractive optical waveguide provided for the background art;

[0021] Figure 2 Process flow chart of coating an anti-reflection film on a diffractive optical waveguide provided for the background art;

[0022] Figure 3 Optical path diagram of light transmission on the anti-reflection film provided for the background art;

[0023] Figure 4 Schematic structural diagram of the relationship between the second grating region and the anti-reflection film provided for the background art;

[0024] Figure 5 For Figure 4 Partial enlarged view of the dashed box in

[0025] Figure 6 Optical path diagram of the second light transmission on the anti-reflection film provided for the background art;

[0026] Figure 7 Schematic structural diagram of an optimized interference fringe structure in a diffractive optical waveguide provided by an embodiment of the present invention;

[0027] Figure 8 Schematic structural diagram of the second optimized interference fringe structure in a diffractive optical waveguide provided by an embodiment of the present invention;

[0028] Figure 9 Schematic structural diagram of the third optimized interference fringe structure in a diffractive optical waveguide provided by an embodiment of the present invention;

[0029] Figure 10 Schematic structural diagram of the fourth optimized interference fringe structure in a diffractive optical waveguide provided by an embodiment of the present invention. Detailed implementation manners

[0030] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0031] It should be noted that the terms "first", "second", etc. in the description, claims and above-mentioned drawings of the present utility model are used to distinguish similar objects, and do not necessarily have to be used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present utility model described herein can be implemented in an order other than those illustrated or described herein.

[0032] Before introducing the content of the present utility model, according to the background art, the principle of coating an anti-reflection film on a diffractive optical waveguide will be briefly described.

[0033] Figure 1 FIG. is a schematic structural diagram of a diffractive optical waveguide provided by the background art. Figure 2 FIG. is a process flow chart of coating an anti-reflection film on a diffractive optical waveguide provided by the background art. Figure 3 FIG. is an optical path diagram of light transmission on the anti-reflection film provided by the background art. Figure 4 FIG. is a schematic structural diagram of the relationship between the second grating region and the anti-reflection film provided by the background art. Figure 5 For Figure 4 the partial enlarged view of the dashed box in Figure 6 FIG. is an optical path diagram of the second light transmission on the anti-reflection film provided by the background art. Refer to Figures 1 to 6 shown. After the diffractive optical waveguide is fabricated, taking the grating structure formed by the cross-section ab of the grating region as an example, refer to Figure 2 , chemical masking or physical masking is performed on the grating region of the diffractive optical waveguide. The masking region is shown in the figure. Among them, chemical masking can be realized by processes such as photolithography. After the masking of the grating region is completed, an anti-reflection film is deposited on the diffractive optical waveguide by physical vapor deposition, chemical vapor deposition or magnetron sputtering, etc., and after the deposition of the anti-reflection film is completed, the anti-reflection film in the masking region is removed, and the obtained structure is the anti-reflection film structure provided in the non-grating region.

[0034] When physical masking or chemical masking is performed on the grating region, chemical masking will cause the sidewalls to tilt when masking the photolithography region. When depositing the anti-reflection film, the anti-reflection film will fill the peripheral region of the chemical masking under the molecular movement, so that the sidewalls of the anti-reflection film are closely attached to the sidewalls of the chemical masking. Therefore, the sidewalls of the anti-reflection film are also inclined, that is, they are inclined planes at a certain angle. In addition, under physical masking, the masking component does not contact the grating structure in the grating region, that is, there is a gap between the masking component and the grating structure. At this time, when depositing the anti-reflection film, the anti-reflection film will deposit under the molecular movement through the gap to the under-plated region of the masking component, but it is difficult to deposit to the deep region of the gap, and it will not deposit on the surface of the grating structure, but it is easy to make the sidewalls of the formed anti-reflection film similar to those of chemical masking and present inclined planes at different angles.

[0035] Refer to Figure 3, a diffraction optical waveguide will paste a protective film on one side of the grating area of the waveguide substrate to protect the grating structure in the grating area. The space between the protective film and the waveguide substrate is air, and an anti-reflection film is deposited on the non-grating area between the protective film and the waveguide substrate. Since the side wall of the anti-reflection film presents an inclined plane and the inclined plane is very smooth in the case of deposition coating, there is a certain angle between the side wall of the anti-reflection film and the waveguide substrate, actually forming a wedge structure. When external light passes through this wedge structure, wedge interference will occur, generating bright and dark interference fringes, which affects the normal observation of external ambient light. Refer to Figures 4 to 6 , when the angle between the side wall of the anti-reflection film and the waveguide substrate is greater than 80°, an air region with a width of D will appear between the side wall of the anti-reflection film and the grating area. The refractive index nA of air is less than the refractive index nT of the anti-reflection film and the refractive index nG of the grating area. Therefore, a single slit with a small refractive index in the middle and high refractive indices on both sides is formed. When light passes through the single slit, single-slit diffraction will occur, and unequal-spacing bright and dark interference fringes can be seen during viewing, which affects the normal observation of external ambient light.

[0036] Therefore, in order to avoid the interference fringes affecting the external ambient light, it is necessary to optimize the interference fringes. Figure 7 FIG. is a schematic structural diagram of an interference fringe optimization structure in a diffraction optical waveguide provided by an embodiment of the present invention. Figure 8 FIG. is a schematic structural diagram of a second interference fringe optimization structure in a diffraction optical waveguide provided by an embodiment of the present invention. This embodiment can be applied to eliminate the interference fringes generated by wedge interference formed between the anti-reflection film and the waveguide substrate, so as to improve the transmitted light of the external environment. For example, Figure 1 、 Figure 7 and Figure 8 As shown, the diffraction optical waveguide includes a waveguide substrate 1, and a grating area 2 and a non-grating area 3 are provided on the waveguide substrate 1; an anti-reflection film 31 is provided in the non-grating area 3; the included angle between the plane where the side wall of the anti-reflection film 31 is located and the plane where the waveguide substrate is located is a first preset angle, and the first preset angle α is an acute angle and satisfies: L < 20um; where λ is the wavelength of the coherent light, L is the spacing between adjacent two interference fringes, and n is the refractive index of the medium between the plane where the side wall of the anti-reflection film 31 is located and the plane where the waveguide substrate 1 is located.

[0037] Among them, the waveguide substrate 1 is a support structure or a substrate material in the diffraction optical waveguide, which affects the transmission performance of the diffraction optical waveguide; usually, the waveguide substrate 1 is a glass substrate. The grating area 2 at least includes an input area and an output area, and grating structures are provided in both the input area and the output area. The grating area 2 is used to transmit the light emitted by the optical engine into the diffraction optical waveguide, and transmit it in the diffraction optical waveguide in a total reflection manner, generating a diffraction image and finally exiting to the human eye from the output area. The anti-reflection film 31 is provided in the non-grating area 3 to increase the transmission of external ambient light so that the external ambient light enters the human eye.

[0038] Specifically, since there is an angle between the plane where the side wall of the anti-reflection film 31 is located and the plane where the waveguide substrate 1 is located, this angle can be an interior angle or an exterior angle. Figure 7 Exemplarily shows that the angle is an interior angle. Figure 8 Exemplarily shows that the angle is an exterior angle. In this embodiment, this angle is the first preset angle α, and the first preset angle α is an acute angle. At this time, the plane where the side wall of the anti-reflection film 31 is located and the plane where the waveguide substrate 1 is located form a wedge structure. When light is incident on this wedge structure, interference fringes of light and dark will be generated, and the interference fringes will affect the normal transmission of ambient light, making it impossible for the human eye to observe the true situation of the external ambient light. Therefore, it is necessary to optimize the interference fringes. In this embodiment, the formula for wedge interference is: Since the human eye has limited resolution ability for length, through multiple experimental verifications or theoretical derivations, etc., it can be known that when the distance between two adjacent fringes in the interference fringes of light and dark is less than 20 μm, that is, L < 20 μm, the human eye will recognize the interference fringes of light and dark as a uniformly bright band. Therefore, when optimizing the interference fringes, only by ensuring that L < 20 μm can the human eye normally view the true situation of the external ambient light.

[0039] It should be noted that when ensuring L < 20 μm, the corresponding first preset angle α, the wavelength λ of the coherent light, and the refractive index n of the medium between the plane where the side wall of the anti-reflection film 31 is located and the plane where the waveguide substrate is located can be determined according to the actual situation, and the size of the first preset angle α can be determined according to the determined refractive index n of the medium and the wavelength λ of the coherent light, which is not limited here.

[0040] The technical solution of the embodiment of the present invention, by setting that there is a first preset angle between the plane where the side wall of the anti-reflection film is located and the plane where the waveguide substrate is located, and the first preset angle is an acute angle, when the first preset angle satisfies L < 20 μm, the interference fringes caused by the wedge interference formed between the plane where the side wall of the anti-reflection film is located and the plane where the waveguide substrate is located can be effectively eliminated, making the human eye recognize the interference fringes as a uniformly bright band, while ensuring the normal transmission of the external ambient light and improving the user experience.

[0041] Optionally, α > 1°.

[0042] Specifically, continue to refer to Figure 7 and Figure 8 , usually, the medium between the plane where the side wall of the anti-reflection film 31 is located and the plane where the waveguide substrate 1 is located is air, and the refractive index n of air = 1. The wavelength λ of the coherent light is based on the upper limit of the visible light band, 700 nm. Combining L < 20 μm and substituting it into the above wedge interference formula The magnitude of the first preset angle α can be calculated, that is It can be known that the first preset angle α > 1°. Therefore, when depositing the antireflection film 31, the first preset angle α between the plane where the side wall of the antireflection film 31 is located and the plane where the waveguide substrate 1 is located can be made greater than 1°. In this way, when light is incident on the wedge structure, the interference fringes generated will not be perceived by the human eye, so the human eye can still normally observe the true situation of the external environmental light.

[0043] Optionally, Figure 9 FIG. is a schematic structural diagram of an optimized structure of interference fringes in a third diffractive optical waveguide provided by an embodiment of the present invention. Refer to Figures 7 to 9 As shown, there is a gap between the antireflection film 31 and the grating region 2, and the gap D1 between the point on the side wall of the antireflection film 31 closest to the grating region 2 and the grating region 2 satisfies: D1 < 0.4 um.

[0044] Among them, when the first preset angle α is an interior angle, refer to Figure 7 , the point on the side wall of the antireflection film 31 closest to the grating region 2 is point A in contact with the surface of the waveguide substrate 1. When the first preset angle α is an exterior angle, refer to Figure 8 , the point on the side wall of the antireflection film 31 closest to the grating region 2 is point B far from the surface of the waveguide substrate 1 and not in contact with the waveguide substrate 1.

[0045] Specifically, based on the background technology, when the first preset angle α > 80°, single-slit diffraction will occur. Therefore, to ensure that the human eye can normally observe the true situation of the external environmental light, it is necessary to optimize the interference fringes. According to the theoretical knowledge of single-slit diffraction, the condition for single-slit diffraction to occur is that the single slit needs to satisfy a certain slit width. When the slit width is less than the light wavelength, single-slit diffraction will not occur, and no bright and dark interference fringes will be generated. That is to say, when the distance D1 between the point on the side wall of the antireflection film 31 closest to the grating region 2 and the grating region 2 is less than the light wavelength, single-slit diffraction will not occur. In this embodiment, taking the lower limit of the visible light band of 400 nm as the boundary, when D1 < 0.4 um, visible light will not undergo single-slit diffraction when incident on the single slit, and the interference fringes generated during the transmission of the non-visible light band are invisible to the human eye. Thus, the optimization of the interference fringes is achieved, ensuring that the human eye can normally observe the true situation of the external environmental light.

[0046] Optionally, continue to refer to Figure 9 , the antireflection film 31 partially covers the grating region 2, and the distance D1 between the point on the side wall of the antireflection film 31 closest to the grating region 2 and the grating region 2 satisfies: D1 < 10 um.

[0047] Among them, the determination of the point on the side wall of the antireflection film 31 closest to the grating region 2 can refer to the above embodiment and will not be elaborated here.

[0048] Specifically, according to the above theoretical knowledge of single-slit diffraction, single-slit diffraction will not occur if the single slit meets a certain slit width. Therefore, in this embodiment, when depositing the anti-reflection film 31, the anti-reflection film 31 partially covers the grating region 2, so there is no single slit between the side wall of the anti-reflection film 31 and the grating region 2, and single-slit diffraction will not occur. In addition, it should be noted that when the anti-reflection film 31 partially covers the grating region 2, in order to ensure that the human eye cannot observe the anti-reflection film 31 in the grating region 2, it is necessary to set the distance D1 between the closest point of the side wall of the anti-reflection film 31 to the grating region 2 and the grating region 2 to be less than 10 um. Within this range, the coverage of the anti-reflection film 31 and the grating region 2 will not affect the rotation range of the human eye, and the human eye cannot perceive that the grating region 2 covers the anti-reflection film 31, so it will not affect the light transmittance of the grating region 31, ensuring that the human eye can normally observe the diffraction image generated when light travels in the grating region 2, and at the same time achieving the elimination of interference fringes.

[0049] Optionally, Figure 10 is a schematic structural diagram of the fourth interference fringe optimization structure in the diffractive optical waveguide provided by the embodiment of the present invention. Refer to Figure 10 As shown, there is a gap between the anti-reflection film 31 and the grating region 2, and the filling material 4 is disposed in the gap. The refractive index of the filling material 4 is between the refractive index nT of the anti-reflection film 31 and the refractive index nG of the grating region 2.

[0050] Optionally, the refractive index nT of the anti-reflection film 31 is less than the refractive index nG of the grating region 2.

[0051] Specifically, based on the background technology, the condition for single-slit diffraction to occur is that the refractive index nA of the intermediate medium is less than the refractive index nT of the anti-reflection film and the refractive index nG of the grating region, that is, the intermediate refractive index is low and the refractive indices on both sides are high. When this condition is met, interference fringes will be generated when light passes through the single slit. Therefore, to optimize the interference fringes, in this embodiment, a filling material 4 is disposed between the anti-reflection film 31 and the grating region 2, and the refractive index nM of the filling material 4 is between the refractive index nT of the anti-reflection film 31 and the refractive index nG of the grating region 2, and the refractive index nT of the anti-reflection film 31 is less than the refractive index nG of the grating region 2. In this way, the refractive index shows an increasing state when the side wall of the anti-reflection film 31 transitions to the grating region 2, that is, nT < nM < nG, which destroys the condition for single-slit diffraction to occur. The single slit does not exist and no diffraction phenomenon occurs, ensuring that the human eye can normally observe the true situation of the external environmental light.

[0052] Optionally, the grating region 2 at least includes an input region and an output region, and grating structures are disposed in both the input region and the output region.

[0053] Optionally, the plane where the side wall of the anti-reflection film 31 is located at least faces the output region, and the included angle with the plane where the waveguide substrate 1 is located is the first preset angle α.

[0054] Optionally, the grating structure in the coupling-in region is one of a straight grating, an inclined grating, a blazed grating, or a two-dimensional grating; the grating structure in the coupling-out region is one of a straight grating, an inclined grating, a blazed grating, or a two-dimensional grating.

[0055] Among them, a straight grating is an optical device composed of a large number of parallel slits with equal width and equal spacing; the inclined grating and the blazed grating are similar, both representing gratings with a specific diffraction structure having a certain inclination angle in their grating planes, and can produce a high diffraction efficiency in specific diffraction orders.

[0056] Specifically, when the grating region 2 includes a coupling-in region and a coupling-out region, the distance D1 between the anti-reflection film 31 and the grating region 2 in the above embodiment can be expressed as the distance between the anti-reflection film 31 and the grating structure in the coupling-in region, or the distance between the anti-reflection film 31 and the grating structure in the coupling-out region. Similarly, in the above embodiment, the filling material 4 is located in the gap between the anti-reflection film 31 and the grating region 2, which can also be expressed as the filling material 4 is located in the gap between the anti-reflection film 31 and the grating structure in the coupling-in region, or the filling material 4 is located in the gap between the anti-reflection film 31 and the grating structure in the coupling-out region, and can be specifically determined according to the actual situation, and is not limited herein.

[0057] It can be understood that the grating structure may further include a turning region, and a grating structure is provided in the turning region. At this time, the distance D1 between the anti-reflection film 31 and the grating region 2 can be expressed as the distance between the anti-reflection film 31 and the grating structure in the turning region. The filling material 4 is located in the gap between the anti-reflection film 31 and the grating region 2, which can also be expressed as the filling material 4 is located in the gap between the anti-reflection film 31 and the grating structure in the turning region.

[0058] Based on the same inventive concept, the present invention also provides an augmented reality device, including an optical engine and the interference fringe optimization structure in the above diffraction optical waveguide. It has corresponding functional modules and beneficial effects of the structure.

[0059] It should be understood that the various forms of the processes shown above can be used, steps can be reordered, added, or deleted. For example, the steps recorded in the present invention can be executed in parallel, sequentially, or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and are not limited herein.

[0060] The above specific embodiments do not constitute a limitation to the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An optimized structure of interference fringes in a diffractive optical waveguide, characterized in that, It includes a waveguide substrate, on which a grating region and a non-grating region are provided; an antireflection film is provided on the non-grating region; The included angle between the plane where the side wall of the antireflection film is located and the plane where the waveguide substrate is located is a first preset angle. The first preset angle α is an acute angle and satisfies: L < 20um; where λ is the wavelength of the coherent light, L is the spacing between two adjacent interference fringes, and n is the refractive index of the medium between the plane where the side wall of the antireflection film is located and the plane where the waveguide substrate is located.

2. The structure according to claim 1, characterized in that, α＞1°。 3. The structure according to claim 2, wherein The antireflection film partially covers the grating region, and the distance D1 between the point on the side wall of the antireflection film closest to the grating region and the grating region satisfies: D1 < 10 μm.

4. The structure according to claim 2, characterized in that, There is a gap between the antireflection film and the grating region, and the gap D2 between the point on the side wall of the antireflection film closest to the grating region and the grating region satisfies: D2 < 0.4 μm.

5. The structure according to claim 2, wherein, There is a gap between the antireflection film and the grating region, a filling material is provided in the gap, and the refractive index of the filling material is between the refractive index of the antireflection film and the refractive index of the grating region.

6. The structure according to claim 2, wherein, The refractive index of the antireflection film is less than the refractive index of the grating region.

7. The structure according to claim 1, characterized in that, The grating region at least includes a coupling-in region and a coupling-out region, and grating structures are provided in both the coupling-in region and the coupling-out region.

8. The structure according to claim 7, wherein, The plane where the side wall of the antireflection film is located at least faces the coupling-out region, and the angle between it and the plane where the waveguide substrate is located is the first preset angle.

9. The structure according to claim 7, characterized in that, The grating structure in the coupling-in region is one of a straight grating, an inclined grating, a blazed grating or a two-dimensional grating; the grating structure in the coupling-out region is one of a straight grating, an inclined grating, a blazed grating or a two-dimensional grating.

10. An augmented reality device, characterized in that, It includes an optical machine and an optimized structure of interference fringes in a diffractive optical waveguide according to any one of claims 1-9.

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