Diffraction optical waveguide structure, preparation method thereof and augmented reality glasses

Abstract

The preparation method of the diffraction optical waveguide structure comprises the following steps: forming a first adhesive layer on a first protective layer, and enabling the first adhesive layer to form a first grating structure by adopting imprinting; forming a second adhesive layer on the second protective layer, and enabling the second adhesive layer to form a second grating structure through imprinting; providing a substrate comprising a first surface and a second surface opposite to each other; a first imprint glue layer is formed on the first surface, a composite body of the first protection layer and the first glue layer is stacked on the side, provided with the first imprint glue layer, of the substrate, pressing is conducted to enable the first imprint glue layer to form a third grating structure, and the first grating structure and the third grating structure are meshed with each other; and forming a second imprint glue layer on the second surface, laminating a composite body of the second protection layer and the second glue layer on one side of the substrate with the second imprint glue layer, pressing to enable the second imprint glue layer to form a fourth grating structure, and meshing the second grating structure with the fourth grating structure. The preparation method can save cost. The invention further provides the diffraction optical waveguide structure and augmented reality glasses.

Description

Technical Field

[0001] The present application relates to the field of optics, and in particular to a diffraction optical waveguide structure and a preparation method thereof, as well as augmented reality glasses including the diffraction optical waveguide structure. Background Art

[0002] Augmented reality (AR) near-eye displays typically consist of a light engine (or optical machine) and a diffractive waveguide element. The light engine generates image light, while the waveguide directs the image light from the light engine to a specific location (the human eye). As one of the most critical components of AR near-eye displays, two types of diffractive waveguide elements are commonly used: surface relief grating (SRG) and holographic grating (HG). SRG diffraction waveguides are fabricated by machining nanoscale grating structures (including spur gratings, cylindrical gratings, circular aperture gratings, diamond columnar gratings, square columnar gratings, blazed gratings, step gratings, tilted gratings, and topological gratings) onto the surface of a high-refractive-index glass substrate. SRGs are typically configured to expand the pupil in one dimension. After the light beam enters the waveguide from the incoupling region, it is dilated in two directions by the turning grating and the outcoupling grating, achieving the desired field of view. When the field of view (FOV) is designed to be larger, the area of the optical waveguide component will also be larger. Existing optical waveguide components with double-sided gratings can effectively reduce the waveguide area while maintaining the field of view (no turning zone).

[0003] However, existing methods for fabricating optical waveguide components with double-sided gratings typically involve applying a high-refractive-index imprinted adhesive material to both sides of a waveguide substrate and then forming the grating structure using nanoimprinting technology. However, high-refractive-index waveguide substrates are relatively expensive. If problems arise during the nanoimprinting process, requiring rework or product scrapping, the cost of fabricating the optical waveguide component increases. Summary of the Invention

[0004] In view of this, the present application provides a method for preparing a diffraction optical waveguide structure that can effectively reduce the preparation cost.

[0005] A method for preparing a diffractive optical waveguide structure, comprising: S1: providing a transparent first protective layer, forming a first adhesive layer on a surface of the first protective layer, and forming a first grating structure on a side of the first adhesive layer facing away from the first protective layer using an embossing technique; S2: providing a transparent second protective layer, and forming a second adhesive layer on a surface of the second protective layer, and forming a second grating structure on a side of the second adhesive layer facing away from the second protective layer by using an embossing technique; S3: providing a substrate, wherein the substrate comprises a first surface and a second surface opposite to each other, and a refractive index of the substrate is higher than a refractive index of the first adhesive layer and a refractive index of the second adhesive layer; S4: forming a first embossed adhesive layer on the first surface of the substrate, wherein the refractive index of the first embossed adhesive layer is higher than the refractive index of the first adhesive layer and the refractive index of the second adhesive layer; laminating a composite of the first protective layer and the first adhesive layer on a side of the substrate having the first embossed adhesive layer, wherein the first grating structure is in direct contact with the first embossed adhesive layer; and laminating the first embossed adhesive layer to form a third grating structure, wherein the first grating structure and the third grating structure are meshed with each other. S5: forming a second embossed adhesive layer on the second surface of the substrate, wherein the refractive index of the second embossed adhesive layer is higher than the refractive index of the first adhesive layer and the refractive index of the second adhesive layer; laminating a composite of the second protective layer and the second adhesive layer on a side of the substrate having the second embossed adhesive layer; the second grating structure is in direct contact with the second embossed adhesive layer; pressing the second embossed adhesive layer to form a fourth grating structure; the second grating structure and the fourth grating structure are meshed with each other.

[0006] The fabrication method for the diffractive waveguide structure of the present embodiment utilizes an embossing technique to preferentially form a low-refractive-index grating structure within a low-refractive-index material layer. This low-refractive-index grating structure is then used to emboss a high-refractive-index embossed adhesive layer, thereby forming a high-refractive-index grating structure within the high-refractive-index embossed adhesive layer. This effectively reduces the number of fabrication steps involving a high-refractive-index substrate, avoiding the risk of rework or damage to the high-refractive-index substrate. This also saves on expensive high-refractive-index substrates, reducing fabrication costs. Furthermore, the first adhesive layer is directly bonded to the first protective layer, and the second adhesive layer is directly bonded to the second protective layer. This eliminates the need for two layers of optical adhesive for the diffractive waveguide structure.

[0007] In some embodiments, the first protective layer and the second protective layer are hard layers; or the first protective layer and the second protective layer are flexible layers.

[0008] In some embodiments, the pressing in step S4 and the pressing in step S5 are performed simultaneously, and the steps S4 and S5 specifically include: forming a first embossed adhesive layer on the first surface of the substrate, and forming a second embossed adhesive layer on the second surface of the substrate; and then placing a composite of the first protective layer and the first adhesive layer, and a composite of the second protective layer and the second adhesive layer on both sides of the substrate, respectively, and pressing them.

[0009] In some embodiments, the refractive index of the first adhesive layer and the second adhesive layer is between 1 and 1.5.

[0010] In some embodiments, the refractive index of the first adhesive layer and the second adhesive layer is n1, the refractive index of the substrate is n2, and n2-n1≥0.3 is satisfied; the refractive index of the first embossed adhesive layer and the second embossed adhesive layer is n3, and n3-n1≥0.3 is satisfied.

[0011] In some embodiments, both the imprinting in step S2 and the imprinting in step S1 use an imprinting mold, and the imprinting mold used in step S2 and the imprinting mold used in step S1 are the same imprinting mold.

[0012] In some embodiments, step S1 and step S2 may be performed in the same step, and step S1 and step S2 specifically include: forming an adhesive layer on a surface of the same protective layer, imprinting the adhesive layer with an imprinting mold and curing the adhesive layer, wherein the imprinting mold is designed with a pattern defining the first grating structure and the second grating structure, and then cutting the protective layer and the adhesive layer to obtain a composite of the first protective layer and the first adhesive layer, and a composite of the second protective layer and the second adhesive layer, which are independent of each other.

[0013] A diffraction optical waveguide structure includes a first protective layer, a first adhesive layer, a first embossed adhesive layer, a substrate, a second embossed adhesive layer, a second adhesive layer, and a second protective layer, which are stacked in sequence. wherein the refractive index of the first embossed adhesive layer, the refractive index of the substrate, and the refractive index of the second embossed adhesive layer are all higher than the refractive index of the first adhesive layer and the refractive index of the second adhesive layer; A first grating structure with a low refractive index is formed on the side of the first adhesive layer facing away from the first protective layer, a second grating structure with a low refractive index is formed on the side of the second adhesive layer facing away from the second protective layer, a third grating structure is formed on the first embossed adhesive layer, the first grating structure and the third grating structure are meshed with each other, and a fourth grating structure is formed on the second embossed adhesive layer, the second grating structure and the fourth grating structure are meshed with each other.

[0014] In some embodiments, the refractive index of the first adhesive layer and the second adhesive layer is n1, and n1 is 1-1.5; the refractive index of the substrate is n2, which satisfies: n2-n1≥0.3; the refractive index of the first embossed adhesive layer and the second embossed adhesive layer is n3, which satisfies: n3-n1≥0.3.

[0015] The present application also provides an augmented reality glasses, comprising a light engine and the above-mentioned diffraction light waveguide structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the preparation process of the diffraction optical waveguide structure of the embodiment of the present application Figure 1 .

[0017] Figure 2 Schematic diagram of the preparation process of the diffraction optical waveguide structure of the embodiment of the present application Figure 2 .

[0018] Figure 3 Schematic diagram of the preparation process of the diffraction optical waveguide structure of the embodiment of the present application Figure 3 .

[0019] Figure 4 Schematic diagram of the preparation process of the diffraction optical waveguide structure of the embodiment of the present application Figure 4 .

[0020] Figure 5 Schematic diagram of the cutting of two complexes in the embodiment of this application Figure 1 .

[0021] Figure 6 Schematic diagram of the cutting of two complexes in the embodiment of this application Figure 2 .

[0022] Description of main component symbols: Diffraction optical waveguide structure 100, first protective layer 11, first adhesive layer 21, first embossed adhesive layer 41, substrate 30, Composite body 10, 20, second embossed adhesive layer 42, second adhesive layer 22, second protective layer 12, first grating structure 211, The second grating structure 221 , the third grating structure 411 , the fourth grating structure 421 , the first surface 301 , and the second surface 302 . DETAILED DESCRIPTION

[0023] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative efforts shall fall within the scope of protection of the present invention.

[0024] The present invention provides a diffractive optical waveguide structure with a double-sided grating and a method for fabricating the same. By employing an imprinting technique to form a low-refractive-index grating structure in a low-refractive-index material layer, and then transferring the low-refractive-index grating structure to a high-refractive-index imprinted adhesive layer to form a high-refractive-index grating structure, the structure can effectively reduce the need for a high-refractive-index substrate, avoiding the risk of rework or damage due to critical steps. This can also save on expensive high-refractive-index substrates and reduce fabrication costs.

[0025] The present invention provides a method for preparing a diffractive optical waveguide structure, comprising the following steps S1 to S5. The order in which steps S1 to S5 are performed is not particularly limited. For example, steps S1 and S2 can be performed simultaneously, or step S1 can be performed first and then step S2, or step S2 can be performed first and then step S1. For example, steps S4 and S5 can be performed simultaneously, or step S4 can be performed first and then step S5, or step S5 can be performed first and then step S4. The diffractive optical waveguide structure has a double-sided grating structure, wherein the grating structure on one side defines a light coupling-in region and a light coupling-out region, and the grating structure on the other side defines a light coupling-out region.

[0026] Step S1: Figure 1 As shown, a first protective layer 11 is provided, and a first adhesive layer 21 with a low refractive index is formed on one surface of the first protective layer 11. By using an embossing technique, a first grating structure 211 with a low refractive index is formed on the side of the first adhesive layer 21 facing away from the first protective layer 11.

[0027] The first protective layer 11 is transparent and can be a rigid layer or a flexible layer with a certain tension. If the first protective layer 11 is a rigid layer, the material of the first protective layer 11 can be optically transparent glass or plastic (such as PET, COP, PC, etc.). If the first protective layer 11 is a flexible layer with a certain tension, it can be made of, for example, thermoplastic polyurethane (TPU), polyether block amide (PEBA), or ethylene-tetrafluoroethylene copolymer. The first protective layer 11 serves as the base 30 for the imprinting of the low-refractive index first adhesive layer 21, providing support for the first adhesive layer 21 and ensuring stability during the imprinting process.

[0028] The first protective layer 11 is ultimately the outermost layer of the diffraction optical waveguide structure, which helps to ensure the structural strength of the diffraction optical waveguide structure and avoid damage to the diffraction optical waveguide structure during transportation and subsequent use.

[0029] In the embodiment of the present application, the low-refractive-index first adhesive layer 21 is a transparent adhesive layer with a low refractive index. This allows the low-refractive-index first adhesive layer 21 to adhere to the first protective layer 11 through its inherent adhesive properties, achieving a tight connection with the first protective layer 11 without gaps. In some embodiments, the refractive index n1 of the first adhesive layer 21 is between 1 and 1.5, for example, 1, 1.1, 1.2, 1.3, 1.4, or 1.5.

[0030] In the embodiment of the present application, the imprinting technology in S1 is nanoimprinting technology. Nanoimprinting technology transfers the nanostructure pattern on the imprinting mold 50 to the material layer by mechanical replication (micro-contact printing), which is essentially a "physical imprinting" process.

[0031] The first adhesive layer 21 with a low refractive index can be a UV-curable optically transparent adhesive or a heat-curable optically transparent adhesive. This configuration is conducive to achieving a stable grating morphology on the surface of the first adhesive layer 21 through nanoimprint technology.

[0032] Step S1 specifically includes: coating a low-refractive-index glue layer on a surface of the first protective layer 11, then using nanoimprint technology to press the imprint mold 50 into the glue layer, and curing the glue layer, such as ultraviolet light curing or heat curing. After curing is completed, the imprint mold 50 is removed to form a first glue layer 21 having a first grating structure 211.

[0033] The first grating structure 211 is used to define the light coupling-in and light coupling-out regions of the diffractive waveguide structure. Specifically, the first grating structure 211 includes one of a stepped grating, a blazed grating, a rectangular grating, and a skewed grating. This configuration allows the first grating structure 211 to be implemented using an imprinting process.

[0034] It is understandable that the preparation method may further include forming a metal coating layer in the area where the first grating structure 211 is located in step S1 .

[0035] S2: Provide a second protective layer 12, and form a second adhesive layer 22 with a low refractive index on one surface of the second protective layer 12, and use an embossing technique to form a second grating structure 221 with a low refractive index on the side of the second adhesive layer 22 facing away from the second protective layer 12. After step S2, the second grating structure 221 with a low refractive index is obtained. Figure 3 A composite body 20 of the second protective layer 12 and the second adhesive layer 22 is shown.

[0036] Step S2 can be regarded as a repetition of step S1.

[0037] The second protective layer 12 is transparent and can be a rigid layer or a flexible layer with a certain tension. If the second protective layer 12 is a rigid layer, it can be made of optically transparent glass or plastic (such as PET, COP, PC). If the second protective layer 12 is a flexible layer with a certain tension, it can be made of, for example, thermoplastic polyurethane (TPU), polyether block amide (PEBA), or ethylene-tetrafluoroethylene copolymer. The second protective layer 12 serves as the base 30 for the imprinting of the low-refractive-index second adhesive layer 22, providing support for the second adhesive layer 22 and ensuring stability during the imprinting process.

[0038] The second protective layer 12 is ultimately the outermost layer of the diffraction optical waveguide structure, which helps to ensure the structural strength of the diffraction optical waveguide structure and avoid damage to the diffraction optical waveguide structure during transportation and subsequent use.

[0039] In some embodiments, the refractive index of the second adhesive layer 22 is between 1 and 1.5, such as 1, 1.1, 1.2, 1.3, 1.4, or 1.5.

[0040] In the embodiment of the present application, the imprinting technology in S2 is nanoimprinting technology. In the embodiment of the present application, the low-refractive index second adhesive layer 22 is a low-refractive index glue layer. In this way, the low-refractive index second adhesive layer 22 can adhere to the second protective layer 12 by virtue of its inherent adhesiveness, and the second adhesive layer 22 and the second protective layer 12 can be tightly connected without gaps. The low-refractive index second adhesive layer 22 can be a UV-curable optically transparent glue or a heat-curable optically transparent glue. This configuration facilitates the realization of a stable grating morphology on the surface of the second adhesive layer 22 via nanoimprinting technology.

[0041] Step S2 specifically includes: coating a low-refractive-index glue layer on one surface of the second protective layer 12, then using nanoimprint technology to press the imprint mold 50 into the glue layer, and curing the glue layer, such as ultraviolet light curing or heat curing. After curing is completed, the imprint mold 50 is removed to form a second glue layer 22 having a second grating structure 221.

[0042] The first grating ultimately defines the light incoupling region and the light outcoupling region on one side of the diffractive waveguide structure, while the second grating ultimately defines the light outcoupling region on the other side of the diffractive waveguide structure. If the gratings in the outcoupling regions on both sides are mirror images with the same period, the imprint mold 50 used for nanoimprinting in step S2 can be the same as the imprint mold 50 used in step S1, thus saving the cost of manufacturing an imprint mold.

[0043] It can be understood that when the composite 10 and the composite 20 are embossed using the same embossing mold 50, as shown in FIG. Figure 5 As shown, after the embossing is completed, the composite body 10 of the first protective layer 11 and the first adhesive layer 21 and the composite body 20 of the second protective layer 12 and the second adhesive layer 22 can be trimmed to remove the excess area. Figure 5 The dotted lines in the figure indicate the parts that need to be retained after cutting. For example, the embossed grating (the area with a small circle) in the composite 20 for defining the light coupling-in area needs to be cut off. This will not significantly increase the cost and maintain the utilization rate of the original high refractive index substrate.

[0044] For the gratings in the double-sided outcoupling region, the grating angle and period are different. The imprint mold used for nanoimprinting in step S2 can be the same imprint mold as the imprint mold 50 used for nanoimprinting in step S1. The imprint mold 50 is designed with gratings on the front and back sides. This can produce both front and back gratings at the same time, and can produce twice the number of samples with the same number of imprints. In this case, step S1 and step S2 can be performed in the same step, that is, forming an adhesive layer on one surface of the same protective layer, and using the imprint mold 50 to imprint and solidify the adhesive layer, wherein the imprint mold 50 includes a pattern that defines the gratings on the front and back sides (the first grating and the second grating). Then, the composite of the protective layer and the adhesive layer is cut to obtain two independent parts. Figure 6 The dotted lines in the figure represent the parts to be retained after cutting, namely, the composite body 10 of the first protective layer 11 and the first adhesive layer 21 , and the composite body 20 of the second protective layer 12 and the second adhesive layer 22 .

[0045] Specifically, the second grating structure 221 includes one of a stepped grating, a blazed grating, a rectangular grating, and a skewed grating. This configuration enables the second grating structure 221 to be implemented using an embossing process.

[0046] The first grating structure 211 and the second grating structure 221 with a low refractive index function as an imprinting mold 50 for imprinting the subsequent imprinting glue, and do not serve as a functional layer for light modulation.

[0047] S3: Provide a substrate 30 with a high refractive index, such as Figure 2 As shown, the substrate 30 includes a first surface 301 and a second surface 302 that are opposite to each other.

[0048] In some embodiments, the refractive index of the low-refractive-index first adhesive layer 21 and the second adhesive layer 22 is n1, and the refractive index of the high-refractive-index substrate 30 is n2, satisfying the following equation: n2 - n1 ≥ 0.3. The substrate 30 can be made of high-refractive-index, transparent optical glass, plastic, or resin. Light propagates within the substrate 30 via total internal reflection (TIR). For example, the refractive index of high-refractive-index optical glass is greater than 1.8.

[0049] S4: See Figure 2 A first embossed adhesive layer 41 with a high refractive index is formed on the first surface 301 of the substrate 30, and a composite 10 of the first protective layer 11 and the first adhesive layer 21 is laminated on the side of the substrate 30 having the first embossed adhesive layer 41. The first grating structure 211 is in direct contact with the first embossed adhesive layer 41, and the first embossed adhesive layer 41 is pressed together to form a third grating structure 411 with a high refractive index. The first grating structure 211 and the third grating structure 411 are meshed with each other.

[0050] By virtue of the adhesiveness of the first embossed adhesive layer 41 , the composite 10 of the first protective layer 11 and the first adhesive layer 21 is fully adhered to one side of the substrate 30 .

[0051] In some embodiments, the refractive index of the first embossed adhesive layer 41 is n3, and n3-n1≥0.3. In some embodiments, the substrate 30 has the same refractive index as the first embossed adhesive layer 41. The first embossed adhesive layer 41 may be a UV-curable adhesive or a heat-curable adhesive. Step S4 is to use the first adhesive layer 21 as an imprinting mold 50 for imprinting the first embossed adhesive layer 41, press the first grating structure 211 into the first embossed adhesive layer 41, and cure the first embossed adhesive layer 41, such as UV-curing or heat-curing. The first grating structure 211 and the third grating structure 411 are meshed with each other. The first grating structure 211 and the third grating structure 411 fill each other and are reversely complementary, further making the first embossed adhesive layer 41 and the first adhesive layer 21 seamless and gap-free, which is conducive to ensuring the total reflection of light at the interface between the first embossed adhesive layer 41 with a high refractive index and the first adhesive layer 21 with a low refractive index, so as to ensure the efficient and stable transmission of light. The refractive index of the first adhesive layer 21 connected to the first embossed adhesive layer 41 is significantly different from that of the first embossed adhesive layer 41 , so that light can be totally reflected at the interface between the first embossed adhesive layer 41 with a high refractive index and the first adhesive layer 21 with a low refractive index.

[0052] S5: If Figure 3 As shown, a second embossed adhesive layer 42 with a high refractive index is formed on the second surface 302 of the substrate 30. The composite 20 of the second protective layer 12 and the second adhesive layer 22 is laminated on the side of the substrate 30 having the second embossed adhesive layer 42. The second grating structure 221 is in direct contact with the second embossed adhesive layer 42. The second embossed adhesive layer 42 is pressed together to form a fourth grating structure 421 with a high refractive index. The second grating structure 221 and the fourth grating structure 421 are meshed with each other. In this manner, a diffractive optical waveguide structure 100 is fabricated.

[0053] By virtue of the adhesiveness of the second embossed adhesive layer 42 , the composite 20 of the second protective layer 12 and the second adhesive layer 22 is fully adhered to one side of the substrate 30 .

[0054] In some embodiments, the refractive index of the second embossed adhesive layer 42 is the same as that of the first embossed adhesive layer 41, which is n3, and n3-n1 ≥ 0.3. The second embossed adhesive layer 42 with a high refractive index can be a UV-curable adhesive or a heat-curable adhesive. Step S4 is to use the second adhesive layer 22 as an imprinting mold 50 for imprinting the second embossed adhesive layer 42, press the second grating structure 221 into the second embossed adhesive layer 42, and then cure the second embossed adhesive layer 42, such as UV curing or heat curing. The second grating structure 221 is meshed with the fourth grating structure 421. The second grating structure 221 and the fourth grating structure 421 fill each other and are reversely complementary, further making the second embossed adhesive layer 42 and the second adhesive layer 22 seamless and gap-free, which is conducive to ensuring the total reflection of light at the interface between the second embossed adhesive layer 42 with a high refractive index and the second adhesive layer 22 with a low refractive index, so as to ensure the efficient and stable transmission of light.

[0055] In some embodiments, the third grating structure 411 is used for coupling light into and out of the diffraction waveguide structure, and the fourth grating structure 421 is used for coupling light out of the diffraction waveguide structure.

[0056] It is understood that in some embodiments, step S4 and step S5 are performed sequentially. In other embodiments, the pressing in step S4 and the pressing in step S5 are performed simultaneously. Figure 4 As shown, a first embossed adhesive layer 41 with a high refractive index is first formed on the first surface 301 of the substrate 30, and a second embossed adhesive layer 42 with a high refractive index is formed on the second surface 302 of the substrate 30. A composite 10 of a first protective layer 11 and a first adhesive layer 21 is laminated on the side of the substrate 30 having the first embossed adhesive layer 41, with the first grating structure 211 in direct contact with the first embossed adhesive layer 41. A composite 20 of a second protective layer 12 and a second adhesive layer 22 is laminated on the side of the substrate 30 having the second embossed adhesive layer 42, with the second grating structure 221 in direct contact with the second embossed adhesive layer 42. The laminated structures are then laminated together, so that the first grating structure 211 is transferred to the first embossed adhesive layer 41 to form a third grating structure 411 with a high refractive index, and the second grating structure 221 is transferred to the second embossed adhesive layer 42 to form a fourth grating structure 421 with a high refractive index. In this manner, a diffractive optical waveguide structure 100 is fabricated.

[0057] Compared to conventional techniques that involve nanoimprinting onto a high-refractive-index substrate 30, the method for fabricating a diffractive optical waveguide structure in the present embodiment utilizes an imprinting technique to preferentially form a low-refractive-index grating structure within a low-refractive-index material layer. This low-refractive-index grating structure is then used to imprint a high-refractive-index imprinted adhesive layer, thereby forming a high-refractive-index grating structure within the high-refractive-index imprinted adhesive layer. This effectively reduces the number of fabrication steps involving the high-refractive-index substrate 30, avoiding the risk of rework or damage to the high-refractive-index substrate 30. This also saves the high-refractive-index substrate 30, reducing fabrication costs. Furthermore, the first adhesive layer 21 is directly bonded to the first protective layer 11, and the second adhesive layer 22 is directly bonded to the second protective layer 12. This eliminates the need for two layers of optical adhesive for the diffractive optical waveguide structure.

[0058] like Figure 3 and Figure 4 As shown, the embodiment of the present application also provides a diffractive optical waveguide structure 100 produced by the above-mentioned preparation method, comprising a first protective layer 11, a first adhesive layer 21, a first embossed adhesive layer 41, a substrate 30, a second embossed adhesive layer 42, a second adhesive layer 22, and a second protective layer 12, which are sequentially stacked and bonded, wherein each adjacent two layers in the diffractive optical waveguide structure 100 are seamlessly and tightly connected. A first grating structure 211 is formed on the side of the first adhesive layer 21 facing away from the first protective layer 11, and a second grating structure 221 is formed on the side of the second adhesive layer 22 facing away from the second protective layer 12. A third grating structure 411 is formed on the first embossed adhesive layer 41, and the first grating structure 211 and the third grating structure 411 are intermeshed. A fourth grating structure 421 is formed on the second embossed adhesive layer 42, and the second grating structure 221 and the fourth grating structure 421 are intermeshed.

[0059] The refractive index of the first embossed adhesive layer 41 , the refractive index of the substrate 30 , and the refractive index of the second embossed adhesive layer 42 are all higher than the refractive index of the first adhesive layer 21 and the refractive index of the second adhesive layer 22 .

[0060] The first and second protective layers 11, 12 are transparent and can be either rigid or flexible layers with a certain tension. When the first and second protective layers 11, 12 are rigid layers, they can be made of optically transparent glass or plastic. When the first protective layer 11 is a flexible layer with a certain tension, it can be made of, for example, thermoplastic polyurethane (TPU), polyether block amide (PEBA), or ethylene-tetrafluoroethylene copolymer. The first and second protective layers 11, 12 are ultimately positioned on the outermost sides of the diffractive waveguide structure to ensure its structural strength and prevent damage during transportation and subsequent use.

[0061] In some embodiments, the first adhesive layer 21 and the second adhesive layer 22 have the same refractive index and are n1, and n1 is between 1 and 1.5, for example, 1, 1.1, 1.2, 1.3, 1.4, or 1.5. The refractive index of the high-refractive-index substrate 30 is n2, satisfying: n2-n1≥0.3. The material of the high-refractive-index substrate 30 can be glass or plastic. The first embossed adhesive layer 41 and the second embossed adhesive layer 42 have the same refractive index and are n3, and n3-n1≥0.3. For example, n3-n1 can be 0.3, 0.4, 0.5, 0.6, 0.7 or above. In some embodiments, the substrate 30, the first embossed adhesive layer 41, and the second embossed adhesive layer 42 have the same refractive index.

[0062] The low-refractive-index first and second adhesive layers 21 and 22 can be made of either UV-curable, optically clear adhesive or heat-curable, optically clear adhesive. The substrate 30 can be made of high-refractive-index, transparent optical glass, plastic, or resin. Light propagates within the substrate 30 via total internal reflection (TIR). The high-refractive-index first and second embossed adhesive layers 41 and 42 can be made of either UV-curable or heat-curable adhesive.

[0063] This embodiment of the present application also provides augmented reality glasses (not shown). These glasses can overlay virtual images on real scenes, allowing users to experience a blend of virtual and real worlds. The glasses include a light engine and the aforementioned diffractive optical waveguide structure 100. Light generated by the light engine is guided by the diffractive optical waveguide structure 100 and projected into the human eye.

[0064] The method for fabricating a diffractive optical waveguide structure according to an embodiment of the present application utilizes an embossing technique to preferentially form a low-refractive-index grating structure within a low-refractive-index material layer. This low-refractive-index grating structure is then used to emboss a high-refractive-index embossed adhesive layer, thereby forming a high-refractive-index grating structure within the high-refractive-index embossed adhesive layer. This effectively reduces the number of fabrication steps involving the high-refractive-index substrate 30, avoiding the risk of rework or damage to the high-refractive-index substrate 30. This also saves the high-refractive-index substrate 30, reducing fabrication costs. Furthermore, the first adhesive layer 21 is directly bonded to the first protective layer 11, and the second adhesive layer 22 is directly bonded to the second protective layer 12. This eliminates the need for two layers of optical adhesive.

[0065] It should be noted that the above are only specific embodiments of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by any person skilled in the art within the technical scope disclosed in the present application should be included in the scope of protection of the present application; the embodiments of the present application and the features of the embodiments can be combined with each other unless there is a conflict. Therefore, the scope of protection of the present application shall be based on the scope of protection of the claims.

Claims

1. A method for preparing a diffractive optical waveguide structure, characterized in that: include: S1: providing a transparent first protective layer, forming a first adhesive layer on a surface of the first protective layer, and forming a first grating structure on a side of the first adhesive layer facing away from the first protective layer using an embossing technique; S2: providing a transparent second protective layer, and forming a second adhesive layer on a surface of the second protective layer, and forming a second grating structure on a side of the second adhesive layer facing away from the second protective layer by using an embossing technique; S3: providing a substrate, wherein the substrate comprises a first surface and a second surface opposite to each other, and a refractive index of the substrate is higher than a refractive index of the first adhesive layer and a refractive index of the second adhesive layer; S4: forming a first embossed adhesive layer on the first surface of the substrate, wherein the refractive index of the first embossed adhesive layer is higher than the refractive index of the first adhesive layer and the refractive index of the second adhesive layer; laminating a composite of the first protective layer and the first adhesive layer on a side of the substrate having the first embossed adhesive layer, wherein the first grating structure is in direct contact with the first embossed adhesive layer; and laminating the first embossed adhesive layer to form a third grating structure, wherein the first grating structure and the third grating structure are meshed with each other. S5: forming a second embossed adhesive layer on the second surface of the substrate, wherein the refractive index of the second embossed adhesive layer is higher than the refractive index of the first adhesive layer and the refractive index of the second adhesive layer; laminating a composite of the second protective layer and the second adhesive layer on a side of the substrate having the second embossed adhesive layer; the second grating structure is in direct contact with the second embossed adhesive layer; pressing the second embossed adhesive layer to form a fourth grating structure; the second grating structure and the fourth grating structure are meshed with each other.

2. The method for preparing a diffractive optical waveguide structure according to claim 1, wherein: The first protective layer and the second protective layer are hard layers; or the first protective layer and the second protective layer are flexible layers.

3. The method for preparing a diffractive optical waveguide structure according to claim 1, wherein: The pressing in step S4 and the pressing in step S5 are performed simultaneously. Steps S4 and S5 specifically include: forming a first embossed adhesive layer on the first surface of the substrate, and forming a second embossed adhesive layer on the second surface of the substrate; and then placing a composite of the first protective layer and the first adhesive layer, and a composite of the second protective layer and the second adhesive layer on both sides of the substrate, respectively, and pressing them together.

4. The method for preparing a diffractive optical waveguide structure according to claim 1, wherein: The refractive index of the first adhesive layer and the second adhesive layer is between 1 and 1.

5.

5. The method for preparing a diffractive optical waveguide structure according to claim 1, wherein: The refractive index of the first adhesive layer and the second adhesive layer is n1, the refractive index of the substrate is n2, and n2-n1≥0.3 is satisfied; the refractive index of the first embossed adhesive layer and the second embossed adhesive layer is n3, and n3-n1≥0.3 is satisfied.

6. The method for preparing a diffractive optical waveguide structure according to claim 1, wherein: The imprinting in step S2 and the imprinting in step S1 both use an imprinting mold, and the imprinting mold used in step S2 is the same as the imprinting mold used in step S1.

7. The method for preparing a diffractive optical waveguide structure according to claim 1, wherein: Step S1 and step S2 can be performed in the same step, and specifically include: forming a glue layer on one surface of the same protective layer, using an imprinting mold to imprint and solidify the glue layer, wherein the imprinting mold is designed with a pattern defining the first grating structure and the second grating structure, and then cutting the protective layer and the glue layer to obtain a composite of the first protective layer and the first glue layer, and a composite of the second protective layer and the second glue layer, which are independent of each other.

8. A diffraction optical waveguide structure, characterized in that: It includes a first protective layer, a first adhesive layer, a first embossed adhesive layer, a substrate, a second embossed adhesive layer, a second adhesive layer, and a second protective layer, which are stacked in sequence. wherein the refractive index of the first embossed adhesive layer, the refractive index of the substrate, and the refractive index of the second embossed adhesive layer are all higher than the refractive index of the first adhesive layer and the refractive index of the second adhesive layer; A first grating structure with a low refractive index is formed on the side of the first adhesive layer facing away from the first protective layer, a second grating structure with a low refractive index is formed on the side of the second adhesive layer facing away from the second protective layer, a third grating structure is formed on the first embossed adhesive layer, the first grating structure and the third grating structure are meshed with each other, and a fourth grating structure is formed on the second embossed adhesive layer, the second grating structure and the fourth grating structure are meshed with each other.

9. The diffractive optical waveguide structure according to claim 8, wherein: The refractive index of the first adhesive layer and the second adhesive layer is n1, which is 1-1.5; the refractive index of the substrate is n2, which satisfies: n2-n1≥0.3; the refractive index of the first embossed adhesive layer and the second embossed adhesive layer is n3, which satisfies: n3-n1≥0.

3.

10. An augmented reality glasses, characterized in that: The optical waveguide structure comprises an optical engine and the diffraction optical waveguide structure as claimed in claim 9.

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