A preparation method of uniform diffraction blazed grating and blazed grating

Abstract

The present invention discloses a method for preparing a uniform diffraction blazed grating and a blazed grating for use in the field of diffraction optical waveguide technology. The method comprises: providing a residual layer of a first thickness on a substrate surface based on an imprinting process to form a blazed grating structure on the surface of the residual layer; determining a range of values ​​for a second thickness of a surface coating based on the first thickness; providing a surface coating of a second thickness on the surface of the blazed grating structure to uniformize the diffraction efficiency of the blazed grating within a preset field of view angle range; and providing the second thickness within the range of values. By adjusting the thickness of the residual layer and the surface coating, the uniformity of the diffraction efficiency of the blazed grating within a certain field of view can be improved, thereby reducing the visual experience of uneven brightness and shading when displaying near the eye.

Description

Technical Field

[0001] The present invention relates to the technical field of diffraction optical waveguides, and in particular to a method for preparing a uniform diffraction blazed grating and a blazed grating. Background Art

[0002] Gratings, a common diffractive optical component, operate based on the combined effects of single-slit diffraction and multi-slit interference, and are widely used in diffractive waveguides. However, the diffraction efficiency of a grating is closely related to the diffraction order. Higher diffraction orders result in lower diffraction efficiency, resulting in a significant portion of the incident light energy being lost to ordinary refracted light (zeroth-order diffraction) that cannot be utilized by the waveguide. For an optical waveguide structure, if the input grating uses a conventional rectangular grating, most of the incident light energy is not transmitted along the waveguide to the output grating, which is detrimental for near-eye displays. To address this issue, researchers have employed blazed gratings. Blazed gratings are planar reflective gratings whose grooves are nonparallel to the grating plane, separated by an angle known as the blaze angle. When incident light strikes a blazed grating, its energy is concentrated in the direction of a specific diffraction order. This direction is related to the blaze angle, allowing for controlled control to focus the incident light energy on the desired propagation order.

[0003] Although the blazed grating can distribute the energy of the incident light in a relatively concentrated manner, for a bare grating (without a metal film layer or a high refractive index material film layer on the surface), most of the energy will still be directly transmitted out. Therefore, at this stage, a metal film is coated on the surface of the bare grating to reduce transmission and thus improve the efficiency of the reflected diffraction order (i.e., the propagation order). However, this method only improves the reflected diffraction efficiency when the incident light hits the blazed grating at a certain angle. When the angle of the incident light is changed within a certain range, the diffraction efficiency of the propagation order varies greatly, which will cause an uneven visual experience of light and dark for near-eye display devices. Therefore, how to reduce the uneven visual experience of light and dark is an urgent problem that those skilled in the art need to solve. Summary of the Invention

[0004] An object of the present invention is to provide a method for preparing a uniform diffraction blazed grating, which can reduce the visual experience of uneven brightness during near-eye display; another object of the present invention is to provide a blazed grating, which can reduce the visual experience of uneven brightness during near-eye display.

[0005] To solve the above technical problems, the present invention provides a method for preparing a uniform diffraction blazed grating, comprising:

[0006] Providing a residual layer of a first thickness on the surface of the substrate based on an imprinting process to form a blazed grating structure on the surface of the residual layer;

[0007] Determining a value range of a second thickness of the surface coating according to the first thickness;

[0008] The surface coating of the second thickness is provided on the surface of the blazed grating structure to uniformize the diffraction efficiency of the blazed grating within a preset field of view angle range; the second thickness is within the value range.

[0009] Optionally, after providing the surface coating of the second thickness on the surface of the blazed grating structure, the method further comprises:

[0010] A metal film is arranged on the surface of the surface plating layer.

[0011] Optionally, the surface coating comprises a plurality of surface sub-coatings stacked along a thickness direction;

[0012] The sum of the thicknesses of the plurality of surface sub-plating layers is equal to the second thickness.

[0013] Optionally, along a direction from the blazed grating structure toward a side facing away from the substrate, the refractive indices of the plurality of surface sub-coatings increase sequentially.

[0014] Optionally, the metal film is any one or more of a gold film, a silver film, and an aluminum film spliced ​​in a horizontal direction.

[0015] Optionally, the thickness of the residual layer ranges from 30 nm to 150 nm.

[0016] Optionally, the surface coating is any one or more of a TiO2 film layer, a Ta2O5 film layer, and a ZrO2 film layer stacked along the thickness direction.

[0017] Optionally, the surface coating is a TiO2 film layer;

[0018] The value range of determining the second thickness of the surface coating according to the first thickness includes:

[0019] When the second thickness of the surface coating is less than or equal to the first thickness, the difference between the second thickness and the first thickness is less than or equal to 20 nm;

[0020] When the second thickness of the surface coating is greater than the first thickness, a difference between the second thickness and the first thickness is less than or equal to 80 nm.

[0021] Optionally, providing a residual layer of a first thickness on the surface of the substrate based on an imprinting process to form a blazed grating structure on the surface of the residual layer includes:

[0022] Providing a residual layer on the surface of the substrate based on an imprinting process to form a blazed grating structure on the surface of the residual layer;

[0023] The thickness of the residual layer is measured and recorded as a first thickness.

[0024] The present invention also provides a blazed grating, comprising:

[0025] substrate;

[0026] a residual layer located on the surface of the substrate; the residual layer has a first thickness;

[0027] a blazed grating structure located on the surface of the residual layer;

[0028] A surface coating is located on the surface of the blazed grating structure, and the thickness of the surface coating is a second thickness. The value range of the second thickness is determined according to the first thickness, so that the diffraction efficiency of the blazed grating within a preset field of view angle range is uniform.

[0029] Optionally, also include:

[0030] A metal film is located on the surface of the surface coating facing away from the substrate.

[0031] Optionally, the surface coating includes a plurality of surface sub-coatings stacked along a thickness direction, and the sum of the thicknesses of the surface sub-coatings is equal to the second thickness.

[0032] Optionally, along a direction from the blazed grating structure toward a side facing away from the substrate, the refractive indices of the plurality of surface sub-coatings increase sequentially.

[0033] Optionally, the thickness of the residual layer ranges from 30 nm to 150 nm.

[0034] Optionally, the surface coating is a TiO2 film layer;

[0035] When the second thickness of the surface coating is less than or equal to the first thickness, the difference between the second thickness and the first thickness is less than or equal to 20 nm;

[0036] When the second thickness of the surface coating is greater than the first thickness, a difference between the second thickness and the first thickness is less than or equal to 80 nm.

[0037] The present invention provides a method for fabricating a uniform diffraction blazed grating, comprising: depositing a residual layer of a first thickness on a substrate surface using an imprinting process to form a blazed grating structure on the surface of the residual layer; determining a range of values ​​for a second thickness of a surface coating based on the first thickness; and depositing a surface coating of a second thickness on the surface of the blazed grating structure to uniformize the diffraction efficiency of the blazed grating within a predetermined field of view angle range; wherein the second thickness falls within the range. By adjusting the thickness of the residual layer and the surface coating, the uniformity of the diffraction efficiency of the blazed grating within a predetermined field of view can be improved, thereby reducing the uneven visual experience of near-eye display.

[0038] The present invention also provides a blazed grating, which also has the above-mentioned beneficial effects and will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0040] Figure 1 A flow chart of a method for preparing a uniform diffraction blazed grating provided in an embodiment of the present invention;

[0041] Figure 2 Schematic diagram of the optical waveguide structure model;

[0042] Figure 3 A flowchart of a specific method for preparing a uniform diffraction blazed grating provided in an embodiment of the present invention;

[0043] Figure 4 A schematic structural diagram of a blazed grating provided in an embodiment of the present invention;

[0044] Figure 5 A flowchart of another specific method for preparing a uniform diffraction blazed grating provided by an embodiment of the present invention;

[0045] Figure 6 A flowchart of another specific method for preparing a uniform diffraction blazed grating provided in an embodiment of the present invention;

[0046] Figures 7 to 14 The graph shows the change curve of +1 order reflection diffraction efficiency of blazed grating in the range of -10° to +10° under 8 conditions.

[0047] In the figure: 1. Substrate, 2. Residual layer, 3. Blazed grating structure, 4. Surface coating, 5. Metal film. DETAILED DESCRIPTION

[0048] The core of this invention is to provide a method for preparing a uniformly diffractive blazed grating. In the prior art, a thin metal film is deposited on the surface of the bare grating to reduce transmission and thereby improve the efficiency of the reflected diffraction order (i.e., the propagation order). However, this method only improves the reflected diffraction efficiency when the incident light strikes the blazed grating at a certain angle. Changing the angle of the incident light within a certain range results in significant variations in the diffraction efficiency of the propagation order, resulting in an uneven visual experience for near-eye display devices.

[0049] The present invention provides a method for fabricating a uniform diffraction blazed grating, comprising: depositing a residual layer of a first thickness on a substrate surface using an imprinting process to form a blazed grating structure on the surface of the residual layer; determining a range of values ​​for a second thickness of a surface coating based on the first thickness; and depositing a surface coating of a second thickness on the surface of the blazed grating structure to uniformize the diffraction efficiency of the blazed grating within a predetermined field of view angle range; wherein the second thickness falls within the range. By adjusting the thickness of the residual layer and the surface coating, the uniformity of the diffraction efficiency of the blazed grating within a predetermined field of view can be improved, thereby reducing the uneven visual experience of near-eye display.

[0050] In order to enable those skilled in the art to better understand the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0051] Please refer to Figure 1 as well as Figure 2 , Figure 1 A flow chart of a method for preparing a uniform diffraction blazed grating provided in an embodiment of the present invention; Figure 2 Schematic diagram of the optical waveguide structure model.

[0052] See also Figure 1 In an embodiment of the present invention, a method for preparing a uniform diffraction blazed grating includes:

[0053] S101: providing a residual layer of a first thickness on a surface of a substrate based on an imprinting process to form a blazed grating structure on the surface of the residual layer.

[0054] The substrate 1 is usually a wafer, and is also the channel medium for light propagation in the optical waveguide. Figure 2 The above-mentioned substrate 1 is usually provided with a coupling-in region and a coupling-out region, wherein the coupling-in region is provided with a blazed grating provided in an embodiment of the present invention, and its function is to couple the incident light into the waveguide; and the specific structure of the coupling-out region is not limited in the embodiment of the present invention, and its function is to couple the propagated light out of the waveguide into the human eye.

[0055] In this step, a blazed grating structure 3 is formed on the surface of substrate 1 using an imprinting process using an imprinting adhesive. This process forms a residual layer 2, with the blazed grating structure 3 formed on the surface of the residual layer 2. In this step, the thickness of the residual layer 2, i.e., the first thickness, must be determined to facilitate the determination of the thickness of the surface coating 4 in subsequent steps. It should be noted that in this embodiment of the present invention, the refractive index of the residual layer 2, i.e., the refractive index of the imprinting adhesive used in the imprinting process, must be slightly greater than that of substrate 1 to facilitate the blazed grating function.

[0056] In the embodiment of the present invention, the above-mentioned embossing process can specifically be selected from roller-type UV embossing. The specific details of the embossing process can be referred to the existing art and will not be described in detail here. Specifically, this step generally includes: providing a residual layer 2 on the surface of the substrate 1 based on the embossing process to form a blazed grating structure 3 on the surface of the residual layer 2; and measuring the thickness of the residual layer 2, which is recorded as a first thickness.

[0057] That is, in the embodiment of the present invention, the residual layer 2 and the blazed grating structure 3 can be first set based on the imprinting process, and then the first thickness of the residual layer 2 is measured based on the residual layer 2, so as to determine the second thickness of the surface coating 4 in the subsequent step.

[0058] S102: Determine a value range of a second thickness of the surface coating according to the first thickness.

[0059] In the embodiment of the present invention, the thickness of the residual layer 2 and the surface coating 4 is specifically adjusted to make the diffraction efficiency of the blazed grating uniform within a preset field of view angle range. The specific content of the corresponding relationship will be described in detail in the following invention embodiments and will not be repeated here. In the embodiment of the present invention, the value range corresponding to the above-mentioned first thickness is specifically the second thickness. When the thickness of the surface coating 4 is set within this value range, the diffraction efficiency of the blazed grating has high uniformity. In the embodiment of the present invention, the surface coating 4 is generally required to have a larger refractive index, and the refractive index of the surface coating 4 is at least required to be greater than the refractive index of the above-mentioned residual layer 2, so as to facilitate the realization of the blazed grating function.

[0060] S103: Disposing a surface coating of a second thickness on the surface of the blazed grating structure to uniformize the diffraction efficiency of the blazed grating within a preset viewing angle range.

[0061] In the embodiment of the present invention, the second thickness is within the value range. In this step, a surface coating 4 having a thickness within the value range is provided on the surface of the blazed grating structure 3 based on the value range of the second thickness determined above. The thickness of the surface coating 4 falls within the value range corresponding to the second thickness, thereby achieving uniform diffraction efficiency of the blazed grating within a preset field of view angle range. The resulting blazed grating has relatively uniform diffraction efficiency within the field of view angle range.

[0062] An embodiment of the present invention provides a method for preparing a uniform diffraction blazed grating. By adjusting the thickness of the residual layer 2 and the surface coating 4, the uniformity of the diffraction efficiency of the blazed grating within a certain field of view can be improved, thereby reducing the uneven visual experience of brightness and darkness during near-eye display.

[0063] The specific content of the preparation method of the uniform diffraction blazed grating provided by the present invention will be described in detail in the following invention embodiments.

[0064] Please refer to Figure 3 as well as Figure 4 , Figure 3 A flowchart of a specific method for preparing a uniform diffraction blazed grating provided in an embodiment of the present invention; Figure 4 A schematic structural diagram of a blazed grating provided in an embodiment of the present invention.

[0065] See also Figure 3 In an embodiment of the present invention, a method for preparing a uniform diffraction blazed grating includes:

[0066] S201: providing a residual layer of a first thickness on a surface of a substrate based on an imprinting process to form a blazed grating structure on the surface of the residual layer.

[0067] In this step, the blazed grating structure 3 formed based on the imprinting process has a certain angle between its groove surface and the grating surface. This angle is determined by the grating period and the groove height. The above-mentioned grating period is usually between 350nm and 550nm, and the groove height is usually between 50nm and 350nm. Normally, in an embodiment of the present invention, the thickness of the residual layer 2 ranges from 30nm to 150nm, including the endpoint values. That is, the value range of the above-mentioned first thickness is from 30nm to 150nm, including the endpoint values. It should be noted that in an embodiment of the present invention, it is usually necessary to control the thickness of the residual layer 2. By controlling the thickness of the residual layer 2, it is also possible to achieve uniform diffraction efficiency of the blazed grating within a preset field of view angle.

[0068] S202: Determine a value range of a second thickness of the surface coating according to the first thickness.

[0069] S203: Disposing a surface coating of a second thickness on the surface of the blazed grating structure to uniformize the diffraction efficiency of the blazed grating within a preset viewing angle range.

[0070] Above-mentioned S202 to S203 is basically identical with S102 to S103 in the above-mentioned invention embodiment. For details, please refer to the above-mentioned invention embodiment and will not go into details here. In an embodiment of the present invention, it is necessary to select a high-refractive-index material as the surface coating 4. This surface coating 4 can be any one or more of the TiO2 film, Ta2O5 film, or ZrO2 film, stacked along the thickness direction. That is, the above-mentioned surface coating 4 can be the film of the above-mentioned single material, or multiple materials can be stacked along the thickness direction. The thickness of the above-mentioned surface coating 4 is usually 50nm~200nm, including endpoint values.

[0071] S204: Disposing a metal film on the surface of the surface coating to form a blazed grating.

[0072] In this step, a metal film 5 can be further applied to the surface of the surface coating 4. This can further enhance the performance of the blazed grating based on the light reflective properties of metal materials. Specifically, the metal film 5 is any one or more of a gold film, a silver film, or an aluminum film, spliced ​​together horizontally. Specifically, the metal film 5 can be composed of a single, highly reflective film layer of gold, silver, or aluminum, typically with a thickness of approximately 1 μm. Alternatively, the metal film 5 can be composed of multiple layers of these materials spliced ​​together horizontally. The specific splicing order is not specifically defined in the embodiments of the present invention. In actual use, the medium outside the metal film 5 is typically air.

[0073] The method for preparing a uniform diffraction blazed grating provided by an embodiment of the present invention can further improve the performance of the blazed grating by further disposing a metal film 5 outside the surface coating 4.

[0074] The specific content of the preparation method of the uniform diffraction blazed grating provided by the present invention will be described in detail in the following invention embodiments.

[0075] Please refer to Figure 5 , Figure 5 A flowchart of another specific method for preparing a uniform diffraction blazed grating provided in an embodiment of the present invention.

[0076] See also Figure 5 In an embodiment of the present invention, a method for preparing a uniform diffraction blazed grating includes:

[0077] S301: providing a residual layer of a first thickness on a surface of a substrate based on an imprinting process to form a blazed grating structure on the surface of the residual layer.

[0078] This step is basically the same as S201 in the above-mentioned embodiment of the invention. Please refer to the above-mentioned embodiment of the invention for details, and will not be described again here.

[0079] S302: Determine a value range of a second thickness of the surface coating according to the first thickness; the surface coating 4 includes a plurality of surface sub-coatings stacked along a thickness direction; the sum of the thicknesses of the plurality of surface sub-coatings is equal to the second thickness.

[0080] When arranging the surface coating 4 in this step, a total of multiple surface sub-coatings will be arranged, and multiple surface sub-coatings need to be stacked in the thickness direction. The above-mentioned different surface sub-coatings usually correspond to different materials, which usually have different refractive indices. That is, the surface coating 4 formed by stacking multiple surface sub-coatings is usually a composite film layer, and the thickness of the composite film layer is the second thickness. And in this step, it is necessary to determine the thickness of the above-mentioned composite film layer based on the above-mentioned corresponding relationship and the first thickness of the residual layer 2, and finally determine the thickness of each surface sub-coating. It should be noted that each of the above-mentioned surface sub-coatings usually has a corresponding thickness, that is, the third thickness corresponding to each surface sub-coating can be equal or unequal, and is not specifically limited here.

[0081] S303: Disposing a surface coating of a second thickness on the surface of the blazed grating structure to uniformize the diffraction efficiency of the blazed grating within a preset viewing angle range.

[0082] In this step, based on the thickness of the surface sub-coatings, the surface sub-coatings are sequentially applied to the surface of the blazed grating structure 3, ensuring that the thickness of each surface sub-coating reaches its corresponding thickness, thereby uniformizing the diffraction efficiency of the blazed grating within a predetermined field of view. Specifically, the refractive index of the surface sub-coatings generally increases sequentially from the blazed grating structure 3 toward the side facing away from the substrate 1. That is, the refractive index of the surface sub-gratings sequentially stacked from the surface of the blazed grating structure 3 gradually increases.

[0083] S304: Disposing a metal film on the surface of the surface coating to form a blazed grating.

[0084] This step is basically the same as S204 in the above-mentioned embodiment of the invention. Please refer to the above-mentioned embodiment of the invention for details, and will not be described again here.

[0085] The specific content of the preparation method of the uniform diffraction blazed grating provided by the present invention will be described in detail in the following invention embodiments.

[0086] Please refer to Figure 6 , Figure 6 A flowchart of another specific method for preparing a uniform diffraction blazed grating provided in an embodiment of the present invention.

[0087] See also Figure 6In an embodiment of the present invention, a method for preparing a uniform diffraction blazed grating includes:

[0088] S401: providing a residual layer of a first thickness on a surface of a substrate based on an imprinting process to form a blazed grating structure on the surface of the residual layer.

[0089] This step is basically the same as S201 in the above-mentioned embodiment of the invention. Please refer to the above-mentioned embodiment of the invention for details, and will not be described again here.

[0090] In the embodiment of the present invention, the surface coating layer 4 is a TiO 2 film layer, that is, TiO 2 is specifically selected as the material of the surface coating layer 4 .

[0091] S402: When the second thickness of the surface coating is less than or equal to the first thickness, the difference between the second thickness and the first thickness is less than or equal to 20 nm.

[0092] When the specific value of the first thickness is determined, in this step, when it is determined that the second thickness corresponding to the surface coating 4 is less than or equal to the first thickness of the residual layer 2, the difference between the second thickness and the first thickness will be controlled to be less than or equal to 20nm, that is, the thickness of the surface coating 4 is limited to be less than the thickness of the residual layer 2 by no more than 20nm. By controlling the thickness of the surface coating 4, the diffraction efficiency of the uniformly blazed grating within the preset field of view angle range is improved.

[0093] S403: When the second thickness of the surface coating is greater than the first thickness, the difference between the second thickness and the first thickness is less than or equal to 80 nm.

[0094] On the premise that the specific value of the first thickness is determined, in this step, when it is determined that the second thickness corresponding to the surface coating 4 is greater than the first thickness of the residual layer 2, the difference between the second thickness and the first thickness will be controlled to be no more than 80nm, that is, the thickness of the surface coating 4 is limited to be no more than 80nm greater than the thickness of the residual layer 2. By controlling the thickness of the surface coating 4, the diffraction efficiency of the uniformly blazed grating within the preset field of view angle range is improved.

[0095] At this time, it can be determined that the value range of the second thickness is based on the first thickness corresponding to the residual layer 2, and the floating range is no more than 20 nm downward and no more than 80 nm upward.

[0096] S404: Disposing a surface coating of a second thickness on the surface of the blazed grating structure to uniformize the diffraction efficiency of the blazed grating within a preset viewing angle range.

[0097] This step is basically the same as S203 in the above-mentioned embodiment of the invention. In this step, the thickness of the TiO2 film layer is specifically limited to be within the range of the first thickness corresponding to the residual layer 2, with a downward floating range of no more than 20nm and an upward floating range of no more than 80nm, so as to uniformize the diffraction efficiency of the blazed grating within the preset field of view angle range.

[0098] S405: Disposing a metal film on the surface of the surface coating to form a blazed grating.

[0099] This step is basically the same as S204 in the above-mentioned embodiment of the invention, and will not be described in detail here.

[0100] An embodiment of the present invention provides a method for preparing a uniform diffraction blazed grating. When a TiO2 film layer is used as the surface coating 4, the thickness of the TiO2 film layer is controlled, which can improve the uniformity of the diffraction efficiency of the blazed grating within a certain field of view, thereby reducing the uneven visual experience of light and dark during near-eye display.

[0101] Please refer to Figures 7 to 14 , Figures 7 to 14 The graph shows the change curve of +1 order reflection diffraction efficiency of blazed grating in the range of -10° to +10° under 8 conditions.

[0102] The specific effects of the solution provided by the embodiment of the present invention will be described below with specific experimental data.

[0103] See also Figure 7 For a bare blazed grating without the above-mentioned surface coating 4 and aluminum film as the metal film 5, assuming that the preset field of view angle range is -10° to +10°, that is, for incident light in the range of -10° to +10°, the efficiency of the +1 order reflection diffraction (propagation order) is uneven, and the overall efficiency is relatively low.

[0104] See also Figure 8 When a metal film 5, specifically a 1 μm thick aluminum film, is directly coated on the surface of the bare blazed grating without providing the above-mentioned surface coating 4, the overall efficiency of the blazed grating is improved, but the +1 order reflection efficiency of the incident light in the range of -10° to +10° is still uneven.

[0105] See also Figure 9 A 130nm thick TiO2 film is first deposited on the surface of the blazed grating structure 3 as the surface coating 4, and then a 1μm thick aluminum film is deposited as the metal film 5. At this time, the overall reflection efficiency of the blazed grating is improved, and the +1 level reflection efficiency of the incident light in the range of -10° to +10° becomes more uniform, with an efficiency difference of about 20%.

[0106] See also Figure 10In an embodiment of the present invention, the thickness of the residual layer 2 is controlled to be 80 nm, and a 1 μm thick aluminum film is directly plated on the outside of the blazed grating as the metal film 5, without providing the above-mentioned surface coating 4. At this time, the overall reflection efficiency of the blazed grating is improved, and the +1-level reflection efficiency of the incident light in the range of -10° to +10° becomes more uniform, with an efficiency difference of about 10%.

[0107] From the above, it can be seen that the present invention can achieve uniformity and high efficiency within a certain viewing angle range by simultaneously controlling the thickness of the residual layer 2 and the thickness of the surface coating 4.

[0108] Specifically, in this embodiment of the present invention, a 1mm thick wafer with a refractive index of 1.5 can be used as substrate 1. A right-angle blazed grating is fabricated in the coupling region through a series of process steps. The refractive index of the imprint adhesive used in the nanoimprint process is 1.675, that is, the refractive index of the residual layer 2 is 1.675, which is slightly greater than the refractive index of the wafer. The grating period of the blazed grating is 500nm, and the groove height is 200nm. During the nanoimprint process of the blazed grating, the thickness of the residual layer 2 is specifically controlled to 70nm.

[0109] After the blazed grating structure 3 is fabricated, a TiO2 film is deposited on its surface as a surface coating 4, with a thickness of 110 nm. The combined effect of the 70 nm thick residual layer 2 and the 110 nm thick TiO2 film ensures that the diffraction efficiency of the propagation order of the blazed grating is extremely uniform across all viewing angles. A 1 μm thick aluminum film is then deposited on the TiO2 film as a metal thin film 5 to further enhance reflection.

[0110] For the incident light of TE light with a wavelength of 532nm, when its incident angle is in the range of -10° to +10°, Figure 11 As shown, the diffraction efficiency of the +1 transmission order becomes extremely uniform, with an efficiency difference of about 2%, and the light efficiency is greatly improved, which is about 85%.

[0111] When the thickness of the residual layer 2 is controlled at 80nm and the thickness of the TiO2 film is controlled at 50nm, the thickness of the residual layer 2 and the thickness of the TiO2 film do not match each other. In this case, the overall reflection efficiency of the blazed grating cannot be guaranteed to be high, and the +1 level reflection efficiency of the incident light in the range of -10° to +10° cannot be made more uniform. Figure 12 As shown, when the thickness of the residual layer 2 is 80nm and the thickness of the TiO2 film is 50nm, the reflection efficiency of light incident at a positive angle is lower than that of light incident at a negative angle, and the +1 level reflection efficiency of the incident light in the range of -10° to +10° is uneven.

[0112] When the 110nm thick TiO2 film is replaced by a double-layer film consisting of a 70nm thick TiO2 film and a 40nm thick Ta2O5 film, as shown in FIG. Figure 13 As shown, it can be seen that the overall reflection efficiency of the blazed grating is high, and the uniformity of the +1-order reflection efficiency of the incident light in the range of -10° to +10° is not much different from that of the single TiO2 film.

[0113] like Figure 14 As shown in the figure, when the 110nm thick TiO2 film is replaced by a multilayer film consisting of a 70nm thick TiO2 film, a 20nm thick Ta2O5 film and a 20nm thick ZrO2 film, it can be seen that the overall reflection efficiency of the grating is higher, and the uniformity of the +1 order reflection efficiency of the incident light in the range of -10° to +10° is not much different from that of the single TiO2 film.

[0114] The present invention further provides a blazed grating, which is specifically prepared by the method for preparing a uniform diffraction blazed grating provided by any of the above-mentioned embodiments of the invention. The remaining structures of the blazed grating can be specifically referred to in the prior art and will not be described in detail here.

[0115] Because the method for preparing a uniform diffraction blazed grating provided by the above-described embodiment of the invention can improve the uniformity of the blazed grating's diffraction efficiency within a certain field of view by adjusting the thickness of the residual layer 2 and the surface coating 4, thereby reducing the visual experience of uneven brightness during near-eye display. Accordingly, the blazed grating provided by the embodiment of the invention has a high uniformity of diffraction efficiency within its field of view, enabling uniform brightness during near-eye display.

[0116] Specifically, in an embodiment of the present invention, the blazed grating includes a substrate 1; a residual layer 2 located on the surface of the substrate 1; the thickness of the residual layer 2 is a first thickness, and a blazed grating structure 3 is located on the surface of the residual layer 2; a surface coating 4 located on the surface of the blazed grating structure 3, the thickness of the surface coating 4 is a second thickness, and the value range of the second thickness is a range determined according to the first thickness, so that the diffraction efficiency of the blazed grating is uniformed within a preset field of view angle range.

[0117] The substrate 1, typically a wafer, also serves as the channel medium for light propagation in the optical waveguide. It typically comprises an incoupling region and an outcoupling region. The incoupling region, equipped with a blazed grating according to an embodiment of the present invention, couples incident light into the waveguide. The outcoupling region, while not specifically structured in the present embodiment, couples the propagating light out of the waveguide and into the human eye.

[0118] There is a certain angle between the groove surface and the grating surface of the above-mentioned blazed grating structure 3. This angle is determined by the grating period and the groove height. The above-mentioned grating period is usually between 350nm and 550nm, and the groove height is usually between 50nm and 350nm. Normally, in an embodiment of the present invention, the thickness of the residual layer 2 ranges from 30nm to 150nm, including the endpoint values. That is, the value range of the above-mentioned first thickness is from 30nm to 150nm, including the endpoint values. It should be noted that in an embodiment of the present invention, it is usually necessary to control the thickness of the residual layer 2. By controlling the thickness of the residual layer 2, it is also possible to achieve uniform diffraction efficiency of the blazed grating within a preset field of view angle.

[0119] In an embodiment of the present invention, the surface coating 4 is usually required to have a relatively large refractive index, and the refractive index of the surface coating 4 is at least required to be greater than the refractive index of the residual layer 2, so as to facilitate the realization of the blazed grating function. The thickness of the surface coating 4 is required to fall within the value range corresponding to the second thickness, so as to achieve uniform diffraction efficiency of the blazed grating within the preset field angle range, and the blazed grating prepared thereby has a relatively uniform diffraction efficiency within the field angle range. In an embodiment of the present invention, a high refractive index material is required to be selected as the surface coating 4, and the surface coating 4 can be any one or more of a TiO2 film layer, a Ta2O5 film layer, and a ZrO2 film layer stacked in the thickness direction. That is, the surface coating 4 can be a film layer of the above-mentioned single material, or a plurality of materials stacked in the thickness direction. The thickness of the surface coating 4 is usually between 50nm and 200nm, including the end value.

[0120] Specifically, in an embodiment of the present invention, it further includes: a metal film 5 located on the surface of the surface coating 4 facing away from the substrate 1. Based on the reflective properties of metal materials to light, the performance of the blazed grating can be further enhanced. The metal film 5 includes a gold film, a silver film, and an aluminum film. That is, the material of the above-mentioned metal film 5 can be any one or more of a gold film, a silver film, and an aluminum film spliced ​​in the horizontal direction. That is, the material of the above-mentioned metal film 5 can be a single high-reflective film layer of gold, silver, aluminum, etc., and its thickness is generally about 1μm; it can also be formed by splicing a plurality of film layers of the above-mentioned materials in the horizontal direction, and its thickness is generally about 1μm. In actual use, the medium outside the above-mentioned metal film 5 is usually air.

[0121] Specifically, in an embodiment of the present invention, the surface coating 4 includes a plurality of surface sub-coatings stacked along a thickness direction, and the sum of the thicknesses of the plurality of surface sub-coatings is equal to the second thickness.

[0122] The surface coating 4 comprises a plurality of surface sub-coating layers stacked along the thickness direction. Different surface sub-coating layers typically correspond to different materials and typically have different refractive indices. The surface coating 4 formed by stacking multiple surface sub-coating layers is typically a composite film layer, and the thickness of the composite film layer is equal to the second thickness. It should be noted that each of the surface sub-coating layers typically has a corresponding thickness, that is, the thicknesses of the surface sub-coating layers can be equal or different, and this is not specifically limited here.

[0123] Specifically, in the embodiment of the present invention, the refractive index of the surface sub-layer increases sequentially along the direction from the blazed grating structure 3 toward the side facing away from the substrate 1. That is, the refractive index of the surface sub-gratings stacked sequentially from the surface of the blazed grating structure 3 gradually increases.

[0124] Specifically, in an embodiment of the present invention, the surface coating 4 is a TiO2 film layer; when the second thickness of the surface coating 4 is less than or equal to the first thickness, the difference between the second thickness and the first thickness is less than or equal to 20nm; when the second thickness of the surface coating 4 is greater than the first thickness, the difference between the second thickness and the first thickness is less than or equal to 80nm.

[0125] In the embodiment of the present invention, the thickness of the surface coating 4 is limited to be less than the thickness of the residual layer 2 by no more than 20nm, and the difference between the second thickness and the first thickness is controlled to be no more than 80nm, that is, the thickness of the surface coating 4 is limited to be greater than the thickness of the residual layer 2 by no more than 80nm. The thickness of the surface coating 4 is controlled to improve the diffraction efficiency of the uniform blazed grating within the preset field of view angle range. At this time, it can be determined that the value range of the second thickness is based on the first thickness corresponding to the residual layer 2, and the floating range is no more than 20nm downward and no more than 80nm upward. It can be seen from the above-mentioned invention embodiment that by selecting each film layer of the above-mentioned material, the second thickness of the surface coating 4 is based on the first thickness corresponding to the residual layer 2, and the floating range is no more than 20nm downward and no more than 80nm upward, which can greatly uniformize the diffraction efficiency of the blazed grating within the preset field of view angle range, and reduce the visual experience of uneven brightness when displaying near the eye.

[0126] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from the other embodiments. Reference can be made to the descriptions of the identical or similar parts between the various embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple, and the relevant parts can be referred to the descriptions of the methods.

[0127] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the above description has generally described the components and steps of each example according to their functions. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present invention.

[0128] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein may be implemented directly using hardware, a software module executed by a processor, or a combination of the two. The software module may be placed in a random access memory (RAM), internal memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

[0129] Finally, it should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or device comprising the element.

[0130] The above describes in detail the method for preparing a uniform diffraction blazed grating and the blazed grating provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is intended only to facilitate understanding of the method and core concept of the present invention. It should be noted that those skilled in the art may make various improvements and modifications to the present invention without departing from the principles of the present invention, and such improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a uniform diffraction blazed grating, characterized in that: include: Providing a residual layer (2) of a first thickness on the surface of a substrate (1) based on an imprinting process, so as to form a blazed grating structure (3) on the surface of the residual layer (2); Determining a value range of a second thickness of the surface coating (4) based on the first thickness; Providing the surface coating (4) of the second thickness on the surface of the blazed grating structure (3) to uniformize the diffraction efficiency of the blazed grating within a preset viewing angle range; The second thickness is within the value range; The surface coating (4) comprises a plurality of surface sub-coatings stacked along a thickness direction; The sum of the thicknesses of the plurality of surface sub-plating layers is equal to the second thickness; When the second thickness of the surface coating (4) is less than or equal to the first thickness, the difference between the second thickness and the first thickness is less than or equal to 20 nm; When the second thickness of the surface coating (4) is greater than the first thickness, the difference between the second thickness and the first thickness is less than or equal to 80 nm.

2. The method for preparing a uniform diffraction blazed grating according to claim 1, wherein: After the surface coating (4) of the second thickness is provided on the surface of the blazed grating structure (3), the method further comprises: A metal film (5) is provided on the surface of the surface plating layer (4).

3. The method for preparing a uniform diffraction blazed grating according to claim 1, wherein: Along a direction from the blazed grating structure (3) toward the side facing away from the substrate (1), the refractive indices of the plurality of surface sub-coatings increase sequentially.

4. The method for preparing a uniform diffraction blazed grating according to claim 2, wherein: The metal film (5) is any one or more of a gold film, a silver film, and an aluminum film spliced ​​in a horizontal direction.

5. The method for preparing a uniform diffraction blazed grating according to claim 1, wherein: The thickness of the residual layer (2) ranges from 30 nm to 150 nm.

6. The method for preparing a uniform diffraction blazed grating according to claim 5, wherein: The surface coating (4) is any one or more of a TiO2 film layer, a Ta2O5 film layer, and a ZrO2 film layer stacked along the thickness direction.

7. The method for preparing a uniform diffraction blazed grating according to claim 1, wherein: The method of providing a residual layer (2) of a first thickness on the surface of a substrate (1) based on an imprinting process to form a blazed grating structure (3) on the surface of the residual layer (2) comprises: Providing a residual layer (2) on the surface of a substrate (1) based on an imprinting process to form a blazed grating structure (3) on the surface of the residual layer (2); The thickness of the residual layer (2) is measured and recorded as the first thickness.

8. A blazed grating, characterized in that: include: Base (1); a residual layer (2) located on the surface of the substrate (1); the thickness of the residual layer (2) is a first thickness; a blazed grating structure (3) located on the surface of the residual layer (2); a surface coating (4) located on the surface of the blazed grating structure (3), wherein the thickness of the surface coating (4) is a second thickness, and the value range of the second thickness is a range determined according to the first thickness, so that the diffraction efficiency of the blazed grating within a preset field angle range is uniform; The surface coating (4) comprises a plurality of surface sub-coatings stacked along a thickness direction, and the sum of the thicknesses of the surface sub-coatings is equal to the second thickness; When the second thickness of the surface coating (4) is less than or equal to the first thickness, the difference between the second thickness and the first thickness is less than or equal to 20 nm; When the second thickness of the surface coating (4) is greater than the first thickness, the difference between the second thickness and the first thickness is less than or equal to 80 nm.

9. The blazed grating according to claim 8, wherein: Also includes: A metal film (5) located on the surface of the surface coating (4) facing away from the substrate (1).

10. The blazed grating according to claim 8, wherein Along a direction from the blazed grating structure (3) toward the side facing away from the substrate (1), the refractive indices of the plurality of surface sub-coatings increase sequentially.

11. The blazed grating according to claim 8, wherein The thickness of the residual layer (2) ranges from 30 nm to 150 nm.

Images