Light and thin optical waveguide lens

Abstract

The utility model relates to a light and thin optical waveguide lens, which comprises a waveguide sheet made of wide bandgap semiconductor materials and a protective film made of optical resin materials, and at least one surface of the waveguide sheet is provided with a grating structure. The protection film is arranged on the surface of the waveguide sheet and embedded in the grating gap of the grating structure, the protection film and the outer side surface of the grating structure are approximately located on the same plane, and / or the protection film covers the outer side surface of the grating structure. According to the optical waveguide lens of the utility model, a high-refractive-index glass waveguide sheet with a refractive index of 1.7-1.9 is replaced by a wide bandgap semiconductor material waveguide sheet, and cover glass is replaced by an optical resin material protective film, so that the waveguide sheet is protected on both sides, the overall thickness of the optical waveguide lens is reduced, the optical performance is improved, and hardening, scratch prevention, fog prevention, skid prevention and fouling prevention can be carried out; and functions of high transparency and the like are compounded.

Description

Technical Field

[0001] The utility model relates to the technical field of near-eye display devices, in particular to a light and thin optical waveguide lens and a preparation method and application thereof. Background Art

[0002] Augmented reality technology, or AR technology, provides users with virtual information through images, videos, 3D models and other technologies while displaying real scenes, achieving a clever integration of virtual information and the real world. It is the next detonation point of information technology, and augmented reality glasses may replace mobile phones as the next generation of collaborative computing platform. Augmented reality technology represented by augmented reality glasses is currently beginning to rise in various industries, especially in the security and industrial fields. Augmented reality technology has demonstrated unparalleled advantages and greatly improved the way of information interaction. At present, the more mature optical display solutions in augmented reality technology are mainly divided into prism solutions, birdbath solutions, free-form surface solutions, off-axis holographic lens solutions and waveguide solutions.

[0003] Among many optical display solutions, the embossed grating waveguide uses a embossed grating (SRG) instead of the traditional reflective optical device (ROE) as the coupling-in, coupling-out and exit pupil expansion device in the waveguide solution. Due to its excellent performance, it is considered to be the most promising solution for consumer-grade AR glasses products. Existing optical waveguide lenses mainly use high-refractive glass as the optical waveguide sheet and stack cover glass to protect the grating structure to reduce the impact of external factors on the grating structure, thereby extending the service life of the optical waveguide lens. However, this method of stacking multiple layers of high-refractive glass and attaching optical mechanical circuits makes AR glasses bulky, affecting the user's experience when wearing them for a long time. Therefore, in order to reduce the size and weight of AR glasses, the current main method is to reduce the thickness of the optical waveguide lens or change the cover glass to a resin material to achieve the purpose of weight reduction and thinning.

[0004] A Chinese patent with publication number CN116626800A discloses an optical waveguide lens, comprising an optical waveguide sheet and a cover plate; the number of the optical waveguide sheets is at least two, and the optical waveguide sheets are stacked along the thickness direction of the optical waveguide lens, and adjacent optical waveguide sheets are fixedly connected; the cover plate is fixedly connected to the optical waveguide sheet, and along the thickness direction of the optical waveguide lens, the cover plate is located on one side or both sides of the optical waveguide sheet, and the cover plate is a light-transmitting resin or a light-transmitting glass; along the thickness direction of the optical waveguide lens, there is a first air gap between adjacent optical waveguide sheets, and there is a second air gap between the cover plate and the optical waveguide sheet; a filling piece is arranged in the first and second air gaps to fill at least part of the first and second air gaps, the filling piece is a light-transmitting piece, and the refractive index of the filling piece is 1.2~1.3.

[0005] The above-mentioned prior art solutions have the following defects: the above-mentioned optical waveguide lens is a composite structure of at least two optical waveguide sheets superimposed on a cover plate (cover glass). If two 1mm optical waveguide sheets are superimposed on a 0.5mm cover plate, and the thickness of the first and second air gaps is 50µm, the overall thickness of the optical waveguide lens is 2.60mm, which is relatively thick as a whole; if the thickness of the optical waveguide sheet and the cover plate is too thin, the mechanical strength of the optical waveguide sheet is reduced, and it is easy to break when a collision occurs when the human eye is worn, posing a safety hazard; (2) The working principle of the surface relief grating is that the information of the optical machine is coupled out to the human eye through the incident grating through total reflection inside the optical lens. The critical angle formula of total reflection is: sinC=n2 / n1, where n1 and n2 are the refractive indices inside and outside the waveguide sheet respectively; and when the cover plate and the filler are made of optical resin material, the refractive index difference of the optical waveguide sheet interface is too small, the total reflection angle is larger, and it is difficult to provide total reflection conditions, so the composite of the optical waveguide sheet and the cover plate that has been reported must be separated by an air layer.

[0006] A Chinese patent with publication number CN117590511A discloses an optical waveguide lens, comprising: a waveguide plate, the waveguide plate is provided with a diffraction microstructure; a protective plate, the protective plate is used to protect the diffraction microstructure on the surface of the waveguide plate; an annular adhesive layer, arranged along the edge area of ​​the waveguide plate or the protective plate, the annular adhesive layer is used to connect the waveguide plate and the waveguide plate; an air valve assembly, arranged on the waveguide plate or the protective plate or the annular adhesive layer, the air valve assembly is used to block the discharge of gas in the cavity between the waveguide plate and the protective plate, so that the air pressure in the cavity between the waveguide plate and the protective plate is greater than or equal to the air pressure of the environment in which the optical waveguide lens is located.

[0007] The above-mentioned prior art solutions have the following defects: the protective sheet and waveguide sheet in the above-mentioned optical waveguide lens are generally made of resin material, or a mixture of resin material and glass material, so that the optical waveguide lens has the characteristics of thin thickness and light weight. However, since the optical waveguide lens is too thin, it is easy to undergo large deformation under stress or assembly conditions such as frames, which leads to a significant deterioration of optical properties such as MTF and affects the use effect; although the above-mentioned optical waveguide lens is provided with an annular adhesive layer to form an air layer, and an air valve assembly is attached to cope with the influence of deformation, thereby avoiding light energy loss and stray light caused by the contact between the protective sheet and the waveguide sheet, this will undoubtedly increase the overall weight of the optical waveguide lens. Summary of the invention

[0008] In view of the shortcomings of the prior art, the first object of the utility model is to provide a light and thin optical waveguide lens, which has the advantages of light weight, thin thickness and good optical performance.

[0009] The second object of the utility model is to provide a method for preparing a light and thin optical waveguide lens, which has the advantages of simple process and high yield.

[0010] The third object of the utility model is to provide an application of a light and thin optical waveguide lens, which has the advantages of being suitable for the industrial production and popularization of AR glasses.

[0011] In order to achieve the above first purpose, the utility model provides the following technical solutions:

[0012] A thin and light optical waveguide lens comprises a waveguide sheet composed of a wide bandgap semiconductor material and a protective film composed of an optical resin material, wherein at least one surface of the waveguide sheet has a grating structure, the protective film is arranged on the surface of the waveguide sheet and embedded in the grating gap of the grating structure, and the protective film and the outer surface of the grating structure are approximately on the same plane, and / or the protective film covers the outer surface of the grating structure.

[0013] Specifically, in the optical waveguide lens of the present invention, the specific meaning of the "wide bandgap semiconductor material" refers to a semiconductor material with a bandgap width of 2.3 eV or above, and can be, for example, non-limitingly, one or a combination of silicon carbide (4H-SiC, 6H-SiC, 3C-SiC), gallium nitride (GaN), zinc oxide (ZnO), aluminum nitride (AlN), zinc selenide (ZnSe), indium gallium zinc oxide (IGZO), and diamond;

[0014] The specific meaning of the "grating structure" refers to an optical device composed of a large number of parallel slits (grating gaps) of equal width and equal spacing, and can be, for example, a transmission grating and / or a reflection grating without limitation;

[0015] The specific meaning of the "optical resin material" refers to a high-transmittance polymer optical material that can replace inorganic glass and is widely used in the optical field. For example, it can be one or a combination of several of propylene glycol carbonate (CR-39), polymethyl methacrylate (PMMA), and polycarbonate (PC), for example, without limitation.

[0016] By adopting the above technical scheme, the high-refractive glass waveguide sheet with a refractive index of 1.7~1.9 is replaced by a wide-bandgap semiconductor material waveguide sheet, preferably a silicon carbide material with a refractive index of 2.6, and the optical resin material is directly attached to the grating tooth surface of the grating structure without an air layer. In addition, a functional composite film layer composed of an anti-reflection film, a waterproof film, an anti-radiation film and an anti-fog film can be attached to the waveguide sheet, thereby forming a single-layer optical waveguide lens; wherein the thickness of each layer of the functional composite film layer is nanometer level, the thickest protective film is 3~5μm, and the optical waveguide lens is approximately 0.5mm when calculated based on the waveguide sheet thickness of 0.5mm, and has the properties of being light, thin, and scratch-resistant.

[0017] Furthermore, the waveguide plate is made of silicon carbide material.

[0018] Furthermore, the refractive index of the protective film is 1.50-1.60.

[0019] Furthermore, at least two protective films are provided and are respectively provided on the surface of the waveguide plate close to and away from the grating structure.

[0020] Furthermore, the optical waveguide lens further comprises a functional composite film layer, and the functional composite film layer is arranged on the surface of the protective film.

[0021] Furthermore, the functional composite film layer includes one or more composite films of an anti-reflection film, a waterproof film, an anti-radiation film and an anti-fog film.

[0022] Furthermore, the functional composite film layer includes an anti-reflection film arranged between the grating structure and the protective film, and a waterproof film, an anti-radiation film and an anti-fog film arranged in sequence on the surface of the protective film away from the grating structure.

[0023] Specifically, in the functional composite film layer of the utility model, the specific meaning of "anti-reflection film" refers to an optical film that reduces or eliminates the reflected light of optical surfaces such as lenses, prisms, and plane mirrors, thereby increasing the light transmittance of these components and reducing or eliminating the stray light of the system, also known as an anti-reflection film, such as non-limiting anti-reflection films such as magnesium fluoride, silicon oxide, aluminum oxide, silicon nitride, titanium oxide, tantalum oxide, and zinc sulfide;

[0024] The specific meaning of "waterproof film" refers to a top film that is resistant to oil and water, thin and does not change the optical properties of the anti-reflection film, such as, but not limited to, silicone, polyester, cellulose acetate coating, zirconium oxide coating, fluoride, etc.;

[0025] The specific meaning of "anti-radiation film" refers to the use of special coating technology based on the principle of electromagnetic interference shielding, and the use of special conductive film treatment to make the lens have the function of anti-electromagnetic radiation, such as non-limiting metal compounds such as silver oxide;

[0026] The specific meaning of "anti-fog film" refers to a film with anti-fog properties, such as, but not limited to, silicone, polyester, cellulose acetate coating, zirconium oxide coating, fluoride, etc.

[0027] In order to achieve the above second purpose, the utility model provides the following technical solutions:

[0028] A method for preparing a thin and light waveguide lens comprises the following steps:

[0029] S1, coating the surface of the optical waveguide sheet close to the grating structure to obtain an anti-reflection film;

[0030] S2 coating the surface of the anti-reflection film, or the surface of the anti-reflection film and the surface of the optical waveguide plate close to the grating structure to obtain a protective film;

[0031] S3 coating the surface of the protective film close to the grating structure, or the surfaces of these protective films in sequence, to obtain a waterproof film, an anti-radiation film, and / or an anti-fog film;

[0032] S4 cutting, ink coating, and obtaining the optical waveguide lens.

[0033] By adopting the above technical solution, the traditional method requires coating the waveguide sheet with an anti-reflection film and cutting it, coating the cover glass with a functional film and cutting it, and cutting the PSA into lens contour strips, and then stacking and coating it to obtain a multi-layer waveguide lens. This leads to the following problems: (1) Each step of coating and cutting may scratch or contaminate the optical glass with structure, and even damage the structure area (the structure area is a grating of hundreds of nanometers, which is relatively fragile), causing irreparable damage, affecting the yield and increasing costs. (2) Parameters such as stacking alignment, parallelism, and warping have a great influence on the optical parameters of the waveguide lens. The waveguide lens processed in this way can only protect the single side containing the structure, and the other side of the optical glass cannot be protected. This has a certain impact on the life and performance of the waveguide lens. It is not worthwhile to sacrifice the thinness of the lens itself and add a layer of cover glass to protect the back of the lens.

[0034] Based on the improved single-layer optical waveguide lens, the preparation method of the utility model directly matches the anti-reflection film on the surface of the silicon carbide waveguide plate, and then wraps the optical resin material on both sides of the silicon carbide waveguide plate by the dipping method, and then selectively adds other functional films according to actual needs, and finally cuts and inks to obtain the optical waveguide lens. It has the following advantages: (1) fewer overall steps, no need for overlapping, and double-sided protection of the optical waveguide lens (silicon carbide waveguide plate), (2) the silicon carbide waveguide plate is protected after the anti-reflection film is applied, the protective film is not easy to be scratched, and the lens contaminated during the processing process can also be solved by cleaning without damaging the optical structure.

[0035] Furthermore, in S1 to S3, the coating method is spin coating, dipping, and / or evaporation. The dipping method can directly coat the surface of the anti-reflection film and the surface of the optical waveguide sheet close to the grating structure to obtain a protective film.

[0036] In order to achieve the third purpose above, the utility model provides the following technical solutions:

[0037] The invention discloses an application of a light and thin optical waveguide lens in a display device.

[0038] By adopting the above technical solution, optical waveguide lenses can be industrially applied to display devices, which is suitable for the industrial production and popularization of AR glasses.

[0039] Furthermore, the display device includes a mobile phone, a tablet computer, a laptop computer, a desktop computer display, a smart watch, a naked-eye 3D display screen, VR glasses, AR glasses, a smart bracelet, a smart ring, a camera, smart glasses, a smart checkout counter display, a shelf electronic tag, a smart shopping cart display, an access control display, a vehicle-mounted central console, a makeup mirror, a projector, a refrigerator display, a head-up display, a vehicle-mounted display, a projection screen, or a TV display.

[0040] In summary, the beneficial technical effects of the utility model are:

[0041] 1. The optical waveguide lens of the utility model replaces the high-refractive glass waveguide sheet with a refractive index of 1.7-1.9 with a wide-bandgap semiconductor material waveguide sheet, and replaces the cover glass with an optical resin material protective film. While protecting the waveguide sheet on both sides, reducing the overall thickness of the optical waveguide lens, and improving the optical performance, it can also be hardened, anti-scratch, anti-fog, anti-slip, anti-fouling, and high-transmittance composite;

[0042] 2. The preparation method of the utility model has the advantages of simple process and high yield rate;

[0043] 3. The utility model can industrially apply optical waveguide lenses to display devices, and is suitable for the industrial production and popularization of AR glasses. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a structural schematic diagram of a light and thin optical waveguide lens according to Embodiment 1 of the present utility model.

[0045] Figure 2 It is a schematic structural diagram of a light and thin optical waveguide lens according to Embodiment 10 of the present utility model.

[0046] Figure 3 It is a schematic structural diagram of a thin and light waveguide lens according to Example 11 of the utility model.

[0047] Figure 4 It is a schematic structural diagram of a thin and light waveguide lens according to Example 12 of the utility model.

[0048] Figure 5 It is a schematic structural diagram of a thin and light waveguide lens according to Embodiment 13 of the present utility model.

[0049] Figure 6 It is a schematic structural diagram of a thin and light waveguide lens according to Embodiment 14 of the present utility model.

[0050] In the figure, 1. waveguide; 11. grating structure; 2. protective film; 3. functional composite film layer; 31. anti-reflection film; 32. waterproof film; 33. anti-radiation film; 34. anti-fog film. DETAILED DESCRIPTION

[0051] In order to make the technical means, creative features, objectives and functions achieved by the present invention clearer and easier to understand, the present invention is further described below in conjunction with the accompanying drawings and specific implementation methods. Example

[0052] Example 1: Reference Figure 1 , is a light and thin optical waveguide lens disclosed in the utility model, comprising a waveguide sheet 1, two protective films 2, and a functional composite film layer 3. In order to make the optical waveguide lens have the advantages of light weight, thin thickness and good optical performance:

[0053] The waveguide plate 1 is made of silicon carbide material, and the front surface of the waveguide plate 1 has a grating structure 11;

[0054] The protective film 2 is made of HASUNCAST 3010 optical resin material. The protective film 2 is respectively arranged on the front and back sides of the waveguide plate 1 and embedded in the grating gap of the grating structure 11. The protective film 2 located on the front side of the waveguide plate 1 covers the outer surface of the grating structure 11.

[0055] The functional composite film layer 3 is arranged on the protective film 2 located on the front side of the waveguide plate 1, and the functional composite film layer 3 includes an anti-reflection film 31 (coating, titanium oxide / silicon oxide composite film) arranged between the grating structure 11 and the protective film 2, and a waterproof film 32 (commercially available, COATMAX AFG95L), an anti-radiation film 33 (coating, silver oxide film) and an anti-fog film 34 (commercially available, COATMAX AFG95L) which are sequentially arranged on the surface of the protective film 2 away from the grating structure 11.

[0056] Embodiments 2 to 7 are thin and light waveguide lenses disclosed in the present invention. The difference from Embodiment 1 is that the waveguide sheet 1 is composed of gallium nitride, zinc oxide, aluminum nitride, zinc selenide, indium gallium zinc oxide, and diamond materials in sequence.

[0057] Embodiment 8 is a light and thin optical waveguide lens disclosed by the present invention. The difference from Embodiment 1 is that the refractive index of the protective film 2 is 1.56.

[0058] Embodiment 9 is a thin and light waveguide lens disclosed by the present invention. The difference from Embodiment 1 is that the refractive index of the protective film 2 is 1.60.

[0059] Example 10: Reference Figure 2 , is a light and thin optical waveguide lens disclosed by the utility model, which is different from Example 1 in that the protective film 2 located on the front side of the waveguide sheet 1 and the outer surface of the grating structure 11 are approximately on the same plane.

[0060] Example 11: Reference Figure 3 , is a light and thin optical waveguide lens disclosed by the utility model, which is different from embodiment 1 in that a protective film 2 is provided and is arranged on the front side of the waveguide sheet 1.

[0061] Example 12: Reference Figure 4 , is a light and thin optical waveguide lens disclosed in the utility model, which is different from Example 1 in that the functional composite film layer 3 does not include a waterproof film 32.

[0062] Example 13: Reference Figure 5 , is a light and thin optical waveguide lens disclosed in the utility model, which is different from Example 1 in that the functional composite film layer 3 does not include the anti-radiation film 33.

[0063] Example 14: Reference Figure 6 , is a light and thin optical waveguide lens disclosed in the present utility model, which is different from Example 1 in that the functional composite film layer 3 does not include the anti-fog film 34 .

[0064] Embodiment 15 is a method for preparing a thin and light waveguide lens disclosed in the present invention, which is different from Embodiment 1 in that it comprises the following steps:

[0065] S1 uses evaporation method to coat the surface of the optical waveguide plate 1 close to the grating structure 11, the temperature is controlled to be 25°C, the carrier gas is Ar, the chamber pressure is 10-5Pa, the ion beam evaporation power is 500W, the TiO2 coating time is 200s, the SiO2 coating time is 60s, and the coating is alternately performed 3 times to obtain an anti-reflection film 31;

[0066] S2 uses a dip coating method to coat the surface of the anti-reflection film 31 and the surface of the optical waveguide plate 1 close to the grating structure 11, and controls the dip coating method to coat the protective film 2 (hard film) stock solution with a pulling speed of 50 mm·min-1 under 40kHz ultrasonic oscillation, and heat-treats at 80°C for 1h to cure, thereby obtaining a protective film 2;

[0067] S3 uses a spin coating method to coat the surface of the protective film 2 close to the grating structure 11, controls the initial rotation speed to be 500 rpm, maintains it for 5 seconds, then changes to 3000 rpm, spins for 60 seconds, and bakes the excess solvent on a hot plate at 130° C. to obtain a waterproof film 32;

[0068] Spin coating is performed on the surface of the protective film 2 close to the grating structure 11, with a DC target position, a working current of 35 mA, a carrier gas of Ar, and a coating time of 30 seconds to obtain an anti-radiation film 33;

[0069] The protective film 2 near the grating structure 11 is coated by spin coating, the initial rotation speed is controlled to be 500 rpm, after maintaining for 5 seconds, it is turned to 3000 rpm, and the spin coating is carried out for 60 seconds. The excess solvent is baked on a hot plate at 130°C to obtain an anti-fog film 34.

[0070] S4 cutting, ink coating, and obtaining the optical waveguide lens.

[0071] Example 16: This is an application of a thin and light optical waveguide lens disclosed in the present invention in a display device. The difference from Example 1 is that the display device is AR glasses. Comparative Example

[0072] Comparative Example 1 is a light and thin optical waveguide lens disclosed in the present invention. The difference from Example 1 is that the waveguide sheet 1 is made of high-refractive glass, and the refractive index is 1.7, 1.8, and 1.9 respectively.

[0073] Comparative Example 2 is a thin and light waveguide lens disclosed by the present invention, which is different from Example 1 in that the protective film 2 is made of light-transmitting glass.

[0074] Comparative Example 3 is a thin and light optical waveguide lens disclosed in the present invention. The difference from Example 1 is that an air gap layer (not shown in the figure) is reserved between the protective film 2 located on the front side of the waveguide sheet 1 and the outer surface of the grating structure 11.

[0075] Performance testing

[0076] 1. Hardness test: The hardness of the optical waveguide lenses of Examples 1 to 14 was tested using a Shore hardness tester. The results showed that the hardness of the optical waveguide lenses exceeded 80D.

[0077] 2. Transmittance test: The transmittance of the optical waveguide lenses of Examples 1 to 14 was tested using an ultraviolet spectrophotometer, with the test range of 400 to 800 nm. The results showed that the transmittance of the optical waveguide lenses exceeded 98%. Among them, the transmittance of the optical waveguide lens of Example 13 was the highest, and it was speculated that the anti-radiation film would reduce the visible light transmittance a little.

[0078] 3. Weight test: The optical waveguide lenses (35*50*0.4 mm, length*width*thickness) of Examples 1 to 14 were tested for weight using an analytical balance. The results showed that after being modified with the protective film 2, the anti-fog film 34, and / or the anti-radiation film, the weight of the optical waveguide lenses was about 0.5 g, which was much lower than the weight of Comparative Examples 1 to 2.

[0079] 4. Total reflection critical angle test: The total reflection critical angle test was performed on the optical waveguide lenses of Example 1 and Comparative Example 1, and the results are shown in Table 1. As can be seen from Table 1, the smaller the total reflection critical angle, the higher the light transmission efficiency in the waveguide lens. The optical waveguide lens of the utility model is far superior to Comparative Examples 1 to 3 in terms of optical properties such as total reflection critical angle, spherical aberration and chromatic aberration, and physical properties such as appearance, thickness, wear resistance, impact resistance, and temperature change resistance.

[0080] Table 1

[0081]

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model rather than to limit it. Although the utility model has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the technical solution of the utility model can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the utility model, which should be included in the scope of the claims of the utility model.

Claims

1. A thin and light waveguide lens, characterized in that: The invention comprises a waveguide plate (1) composed of a wide bandgap semiconductor material, and a protective film (2) composed of an optical resin material, wherein at least one surface of the waveguide plate (1) has a grating structure (11), the protective film (2) is arranged on the surface of the waveguide plate (1) and embedded in the grating gap of the grating structure (11), and the outer surfaces of the protective film (2) and the grating structure (11) are approximately on the same plane, and / or the protective film (2) covers the outer surface of the grating structure (11).

2. The thin and light waveguide lens according to claim 1, characterized in that: The waveguide plate (1) is made of silicon carbide material.

3. The thin and light waveguide lens according to claim 1, characterized in that: The refractive index of the protective film (2) is 1.50-1.

60.

4. The thin and light waveguide lens according to claim 1, characterized in that: At least two protective films (2) are provided and are respectively provided on the surface of the waveguide plate (1) close to and away from the grating structure (11).

5. The thin and light waveguide lens according to claim 1, characterized in that: The optical waveguide lens further comprises a functional composite film layer (3), wherein the functional composite film layer (3) is arranged on the surface of the protective film (2).

6. The thin and light waveguide lens according to claim 5, characterized in that: The functional composite film layer (3) comprises one or more composite films of an anti-reflection film (31), a waterproof film (32), an anti-radiation film (33) and an anti-fog film (34).

7. The thin and light waveguide lens according to claim 6, characterized in that: The functional composite film layer (3) comprises an anti-reflection film (31) arranged between the grating structure (11) and the protective film (2), and a waterproof film (32), an anti-radiation film (33) and an anti-fog film (34) arranged in sequence on a surface of the protective film (2) facing away from the grating structure (11).

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