A diffractive optical structure and near-eye display device

Abstract

The embodiment of the present application discloses a diffractive optical structure and a near-eye display device; the diffractive optical structure includes a substrate and an in-coupling region and an out-coupling region arranged on the substrate; the out-coupling region includes a grating structure, the grating structure includes a plurality of periodically arranged grating ridges and grating grooves between adjacent grating ridges, and the grating grooves are made of at least two materials with different refractive indices; the average refractive index of different materials within a grating unit period of the grating structure is #imgabs0#, 1.1<#imgabs1#≤2.4, #imgabs2#, wherein, V 1~ V m Respectively 1 Materials to m The volume or area of ​​a material, n 1~ n m Respectively 1 Materials to m The refractive index of a material, V unitcell is the volume or area per unit period of the grating.

Description

Technical Field

[0001] The present application belongs to the field of augmented reality (AR) technology. Specifically, the present application relates to a diffractive optical structure and a near-eye display device. Background Art

[0002] With the rapid development of augmented reality (AR) technology, AR optical solutions based on diffractive optical waveguides have gradually become a key way to achieve efficient, lightweight display systems. In this technical field, the overall optical efficiency of the waveguide is one of the important indicators for evaluating its performance. In the existing technology, the ability to control the diffraction efficiency in the non-coupling area has become a key factor restricting the further improvement of the waveguide efficiency.

[0003] Therefore, how to effectively improve the diffraction efficiency control capability in the non-coupling area and realize the flexible movement and control of the grating diffraction efficiency curve has become an urgent problem to be solved in the current AR optical solution. Summary of the invention

[0004] The purpose of this application is to provide a new technical solution for a diffractive optical structure and a near-eye display device.

[0005] According to a first aspect of the present application, an embodiment of the present application provides a diffractive optical structure, the diffractive optical structure comprising a substrate and an in-coupling region and an out-coupling region disposed on the substrate;

[0006] Wherein, the outcoupling region comprises a grating structure, the grating structure comprises a plurality of periodically arranged grating ridges and grating grooves between adjacent grating ridges, and the grating grooves are filled with at least two materials with different refractive indices;

[0007] The average refractive index of different materials within the grating unit period of the grating structure is: , and 1.1< ≤2.4, ,in, V 1~ V m Respectively 1 Materials to m The volume or area of ​​a material, n 1~ n m Respectively 1 Materials to m The refractive index of a material, V unitcell is the volume or area per unit period of the grating.

[0008] Optionally, the average refractive index of different materials within a grating unit period of the grating structure is 1.35≤ ≤2.15.

[0009] Optionally, the substrate includes two opposite surfaces, and the coupling-in region and the coupling-out region are arranged on at least one surface of the substrate;

[0010] The coupling-in region is used to couple external light into the interior of the substrate;

[0011] The outcoupling region is used to expand the pupil of the light and couple it out.

[0012] Optionally, the grating structure includes a first periodicity along the first direction. P 1, a plurality of grating ridges arranged in an array, wherein the grating grooves are located between any two adjacent grating ridges, wherein at least a portion of the grating grooves are air grooves;

[0013] The average refractive index of different materials in the grating unit period of the grating structure as follows:

[0014] ;

[0015] in, = + +……+ , is the longitudinal cross-sectional area of ​​the grating ridge, is the refractive index of the grating ridge, is the longitudinal cross-sectional area of ​​the air slot, is the refractive index of air, is the first 1 The longitudinal cross-sectional area of ​​the filling material, is the first 1 The refractive index of the filling material, is the first m The longitudinal cross-sectional area of ​​the filling material, is the first m The refractive index of the filling material; = P 1* H , H is the height of the grating ridges.

[0016] Optionally, the grating structure comprises a plurality of grating ridges, wherein the plurality of grating ridges are spaced apart by a second period along the second direction. P 2 arrangement, and the third period interval along the third direction P 3, a grating groove is formed between any two adjacent grating ridges, and at least a part of the grating groove is an air groove;

[0017] The average refractive index of different materials in the grating unit period of the grating structure as follows:

[0018] ;

[0019] = + +……+ , is the volume of the grating ridge, is the refractive index of the grating ridge, is the volume of the air tank, is the refractive index of air, is the first 1 The volume of the filling material, is the first 1 The refractive index of the filling material, is the first m The volume of the filling material, is the first m The refractive index of the filling material; =( P 2* P 3) * H , H is the height of the grating ridges.

[0020] Optionally, the grating structure is covered with at least one layer of filling material, and the refractive index of the filling material is different from the refractive index of the grating ridge.

[0021] Optionally, the at least one layer of filling material comprises a 1 A filling material, the 1 A filling material is covered on the surface of the grating ridge and the groove wall and groove bottom of the grating groove, wherein the grating groove includes an air groove and the first 1 A filling material.

[0022] Optionally, the at least one layer of filling material further comprises a 2 A filling material, the 2 A filling material covers the first 1 The grating groove further comprises the first filling material. 2 A filling material is provided, and an air groove is retained at the same time, wherein the first 1 The filling material and the 2 The refractive indices of the two filling materials are different.

[0023] Optionally, the at least one layer of filling material further comprises a 3A filling material, the 3 A filling material covers the first 2 The filling material deviates from the first 1 On the surface of the filling material, the grating groove also includes the first 3 a filling material, and the 3 A filling material fills the air groove;

[0024] Among them, the 1 a filling material, 2 A filling material and the 3 The refractive index of the filling materials is different.

[0025] According to a second aspect of the present application, an embodiment of the present application provides a near-eye display device, the near-eye display device comprising:

[0026] the image source; and

[0027] As in the diffractive optical structure described in the first aspect, the light emitted by the image source can be incident on the coupling-in region on the diffractive optical structure.

[0028] One beneficial effect of the embodiments of the present application is:

[0029] The diffractive optical structure provided in the embodiment of the present application adjusts the average refractive index of different materials in the grating unit period of the grating structure in the out-coupling area (i.e., the non-in-coupling area). The range of the grating structure diffraction efficiency curve is precisely controlled, and the design can significantly improve the overall outcoupling efficiency of the diffraction optical structure. Specifically, during the process of total reflection of the light along the substrate and gradually transmitting to the back end, the reflection angle of the light will naturally decrease. This application has been carefully designed to timely reduce the average refractive index of different materials in the grating unit period of the grating structure in the outcoupling area. , ensuring that the peak of the outcoupling efficiency curve can be flexibly shifted toward the small angle direction, and can accurately match the outcoupling requirements of small-angle light.

[0030] The technical solution provided in the embodiment of the present application not only overcomes the difficulty of accurately controlling the shape and peak position of the out-coupling efficiency curve at different positions in the traditional method, but also realizes the precise positioning of the peak of the out-coupling efficiency curve at the position of the minimum reflection angle of the light, thereby greatly optimizing the transmission path and out-coupling efficiency of the light in the diffractive optical structure.

[0031] Other features and advantages of the present application will become apparent from the following detailed description of exemplary embodiments of the present application with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the application and, together with the description, serve to explain the principles of the application.

[0033] Figure 1 A schematic diagram of the structure of a diffractive optical structure provided in an embodiment of the present application;

[0034] Figure 2 One of the schematic diagrams of the grating structure of the out-coupling region provided in the embodiment of the present application;

[0035] Figure 3 One of the outcoupling efficiency curves of the diffractive optical structure provided in the embodiment of the present application;

[0036] Figure 4 The second outcoupling efficiency curve of the diffractive optical structure provided in the embodiment of the present application;

[0037] Figure 5 The third outcoupling efficiency curve of the diffractive optical structure provided in the embodiment of the present application;

[0038] Figure 6 A second schematic diagram of the grating structure of the out-coupling region provided in an embodiment of the present application;

[0039] Figure 7 The fourth outcoupling efficiency curve of the diffractive optical structure provided in the embodiment of the present application;

[0040] Figure 8 A third schematic diagram of the grating structure of the out-coupling region provided in an embodiment of the present application;

[0041] Fig. 9 A fourth schematic diagram of the grating structure of the out-coupling region provided in an embodiment of the present application;

[0042] Fig.10 A fifth schematic diagram of the grating structure of the out-coupling region provided in an embodiment of the present application;

[0043] Fig.11 A sixth schematic diagram of the grating structure in the outcoupling region provided in an embodiment of the present application;

[0044] Fig.12 A seventh schematic diagram of the grating structure of the out-coupling region provided in an embodiment of the present application;

[0045] Fig.13 The eighth schematic diagram of the grating structure of the out-coupling region provided in an embodiment of the present application.

[0046] Description of reference numerals:

[0047] 1. Incoupling region; 2. Outcoupling region; 3. Substrate;

[0048] 201, grating ridge; 202, grating groove; 203, air groove; 204, 1 Filling material; 205, 2 Filling material; 206, 3 A filling material. DETAILED DESCRIPTION

[0049] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that unless otherwise specifically stated, the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present application.

[0050] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the present application, its application, or uses.

[0051] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered as part of the specification.

[0052] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0053] It should be noted that like reference numerals and letters refer to similar items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0054] The following is a detailed description of the diffractive optical structure and near-eye display device provided in the embodiments of the present application in conjunction with the accompanying drawings.

[0055] Among diffractive optical structures, diffractive optical waveguides are a common form, and diffractive optical waveguides are hereinafter referred to as optical waveguides.

[0056] The overall optical efficiency of the optical waveguide is mainly composed of two parts: coupling efficiency and pupil expansion coupling efficiency. The coupling efficiency mainly focuses on how to efficiently couple external light into the optical waveguide, while the pupil expansion coupling efficiency is more complicated, which requires precise coupling regulation for light at different angles at different positions. Different from the principle that the higher the coupling efficiency, the better, the pupil expansion coupling efficiency needs to achieve effective coupling of light at different angles at different positions according to actual needs. For example, at the front end of the coupling area, since the light transmission path is short and the light with a larger total reflection angle is dominant, the peak of the coupling efficiency curve in this area is usually located at a large angle position. However, as the light is transmitted to the rear end of the optical waveguide, its transmission path increases and the total reflection angle gradually decreases, which requires the coupling efficiency curve to be able to adjust its peak position accordingly to meet the coupling requirements of small-angle light. However, the existing pupil expansion coupling regulation method faces many challenges in achieving this regulation, and it is difficult to accurately control the shape and peak position of the coupling efficiency curve at different positions. To this end, the present application proposes a new diffraction optical structure design, which is described in detail below.

[0057] According to one embodiment of the present application, a diffractive optical structure is provided. Figure 1 The diffractive optical structure comprises a substrate 3 and an incoupling region 1 and an outcoupling region 2 arranged on the substrate 3, wherein the outcoupling region 2 comprises a grating structure, the grating structure comprises a plurality of periodically arranged grating ridges 201 and grating grooves 202 between adjacent grating ridges 201, and the grating grooves 202 are filled with at least two materials with different refractive indices; the average refractive index of different materials within a grating unit period of the grating structure is , and 1.1< ≤2.4, ,in, V 1~ V m Respectively 1 Materials to m The volume or area of ​​a material, n 1~ n m Respectively 1 Materials to m The refractive index of a material, V unitcell is the volume or area per unit period of the grating.

[0058] The diffraction optical structure design provided in the embodiments of the present application is shown in FIG. Figure 1 The diffractive optical structure is composed of a substrate 3 and an in-coupling region 1 and an out-coupling region 2 arranged thereon. In the present application, the average refractive index of different materials in the grating unit period of the grating structure arranged in the out-coupling region 2 is adjusted. To achieve efficient light outcoupling. ≤2.4.

[0059] The diffraction optical structure provided in the embodiment of the present application includes the following parts, which are described in detail below.

[0060] Substrate 3: As the basic support layer of the entire diffractive optical structure, it provides a stable platform for the coupling-in region 1 and the coupling-out region 2. The substrate 3 should have good optical transparency and mechanical stability to ensure the effective transmission of light and the stability of the overall structure.

[0061] Coupling region 1: The main function of this region is to effectively couple external light into the substrate 3, which is equivalent to the entrance for light to enter the diffractive optical structure.

[0062] Outcoupling region 2: This region contains a specially designed grating structure, which is used to expand the pupil (i.e., expand the beam diameter) of light within the diffractive optical structure and couple it out to the external space. In this application, it is a key part to achieve efficient light utilization.

[0063] In the diffractive optical structure provided in the embodiment of the present application, see Figure 1 and Figure 2 The outcoupling region 2 comprises a specially designed grating structure, which is composed of a plurality of periodically arranged grating ridges 201 and grating grooves 202 between adjacent grating ridges; wherein, by calculating the average refractive index of different materials within the grating unit period of the grating structure Design (for example, design for 1.1 < ≤2.4), which can affect the diffraction efficiency curve of the grating structure and thus achieve efficient light outcoupling.

[0064] The grating grooves 202 may be filled with at least two materials, such as air and at least one low refractive index material. When the grating grooves 202 are completely filled with air, the average refractive index of different materials in the grating unit period of the grating structure is is 1.1.

[0065] In order to achieve an average refractive index of the grating structure The present application proposes a variety of methods, see Figure 2 and Figure 6 , including introducing air and / or other low refractive index materials into the grating groove 202.

[0066] For example, various process methods such as spin coating filling glue, inkjet filling glue, ALD deposition, PVD deposition, CVD deposition, etc. can be used. By using these methods alone or in combination, the average refractive index of the grating structure can be adjusted at different positions. , to adapt to the outcoupling requirements of light at different angles, thereby improving the outcoupling efficiency and light uniformity of the entire optical diffraction structure.

[0067] The core of the diffraction optical structure provided in the embodiment of the present application lies in the special design of the grating structure in the outcoupling region 2, and the average refractive index of different materials in the grating unit period is It is set in the range of 1.1 to 2.4 mentioned in the above embodiment. This design utilizes the physical parameter adjustment capability of the grating structure to achieve the average refractive index of different materials within the grating unit period. Fine control of.

[0068] Specifically, by adjusting the size (such as area or volume) and refractive index of the grating ridge 201 and the grating groove 202, and introducing air or other low refractive index materials, the average refractive index of different materials within the grating unit period of the grating structure can be flexibly changed. This design not only broadens the control range, but also allows the shape and position of the grating diffraction efficiency curve to be flexibly adjusted according to demand, thereby optimizing the light outcoupling efficiency and uniformity.

[0069] The diffractive optical structure designed in this way not only improves the efficiency of light utilization, but also enhances the overall performance of the diffractive optical structure, thereby providing a clearer and more uniform visual experience for near-eye display devices.

[0070] The diffractive optical structure provided in the embodiment of the present application can at least bring the following technical effects by newly designing the grating structure of the outcoupling region 2 thereon:

[0071] First, by optimizing the average refractive index of different materials in the grating unit period of the grating structure in the outcoupling region 2 1.1< ≤2.4, the diffractive optical structure provided in the embodiment of the present application can significantly improve the light outcoupling efficiency. This is because, in the process of light being coupled from the coupling-in region 1 into the substrate 3 and transmitted to the coupling-out region 2 (i.e., the rear end), as the light reflection angle naturally decreases, by appropriately reducing the The value of can ensure that the peak of the outcoupling efficiency curve moves toward the small angle direction, thereby meeting the high-efficiency outcoupling requirements of light at different positions and angles.

[0072] Secondly, by realizing the average refractive index of different materials in the grating unit period of the grating structure in the entire outcoupling region 2 Through reasonable regulation, the diffraction optical structure of the present application can improve the uniformity of light distribution and reduce light loss or distortion caused by uneven grating structure.

[0073] It can be seen that the diffraction optical structure provided in the embodiment of the present application not only improves the out-coupling efficiency but also enhances the uniformity of light by designing new optical parameters of the grating structure in the out-coupling region 2, thereby significantly improving the optical performance of the entire diffraction optical structure.

[0074] The diffractive optical structure provided in the embodiment of the present application adjusts the average refractive index of different materials in the grating unit period of the grating structure in the out-coupling region (non-in-coupling region) , achieving precise movement and control of the diffraction efficiency curve of the grating structure, and this design can improve the overall outcoupling efficiency of the optical structure. Specifically, during the process of total reflection of light along the inside of the substrate and gradually transmitting to the back end, the reflection angle of the light will naturally decrease. This application has been carefully designed to timely reduce the average refractive index of different materials in the grating unit period of the grating structure in the outcoupling area. , ensuring that the peak of the outcoupling efficiency curve can be flexibly shifted toward the small angle direction, and can accurately match the outcoupling requirements of small-angle light.

[0075] The technical solution provided in the embodiment of the present application not only overcomes the difficulty of accurately controlling the shape and peak position of the outcoupling efficiency curve at different positions in the traditional method, but also realizes the precise positioning of the peak of the outcoupling efficiency curve at the position of the minimum reflection angle of the light, thereby greatly optimizing the transmission path and outcoupling efficiency of the light in the diffractive optical structure.

[0076] In some examples of the present application, the average refractive index of different materials within the grating unit period of the grating structure is 1.35< ≤2.15.

[0077] In this example of the present application, in the outcoupling region 2, the average refractive index of different materials in the grating unit period of the grating structure is Limited to 1.35≤ ≤2.15. The design of this range is based on the adjustment of the grating ridge 201 when using a low refractive index material on the one hand, and the optimization of the optical performance of the grating structure on the other hand.

[0078] Specifically, the average refractive index of different materials in the grating unit period of the grating structure is The range is designed to be between 1.35 and 2.15 (including the two end points of 1.35 and 2.15), which means that the average refractive index can be used when designing the grating structure. For more precise control, the average refractive index in this range It can more effectively match the transmission characteristics of light and the coupling requirements, thereby ensuring that light can be efficiently coupled out at different positions and angles.

[0079] Within the scope of the example of the present application, by adjusting the physical parameters of the grating structure, such as the size of the grating ridge 201 and the grating groove 202 and the refractive index of the filling material, the shape and peak position of the grating diffraction efficiency curve can be more accurately controlled. In particular, in the process of light transmission from the coupling-in region 1 to the rear end, it can be ensured that the peak of the coupling-out efficiency curve can reach the optimal position at different angles, thereby significantly improving the coupling-out efficiency.

[0080] This range proposed in this example of the present application not only helps to improve the outcoupling efficiency, but also improves the uniformity of light distribution and reduces light loss. The light transmission path in the substrate 3 of the diffractive optical structure is more stable, and the light scattering and reflection caused by the change of the refractive index are reduced. This not only improves the utilization rate of light, but also makes the optical performance of the diffractive optical structure more stable and reliable.

[0081] In some examples of this application, see Figure 1 The substrate 3 includes two opposite surfaces, and the coupling-in region 1 and the coupling-out region 2 are arranged on at least one surface of the substrate 3; the coupling-in region 1 is used to couple external light into the interior of the substrate 3; the coupling-out region 2 is used to expand the pupil of light and couple it out.

[0082] In a specific example, see Figure 1 The coupling-in region 1 and the coupling-out region 2 are arranged together on one of the two opposite surfaces of the substrate 3, and the coupling-in region 1 and the coupling-out region 2 are adjacent and spaced apart; in the coupling-out region 2, the grating structure is arranged such that, in a direction away from the coupling-in region 1, the average refractive index of different materials in the grating unit period is For example, it shows a gradually decreasing trend.

[0083] For the design in the above specific example, the specific analysis is as follows:

[0084] (1) Efficient transmission in the initial stage:

[0085] For the grating structure arranged in the outcoupling region 2, the grating structure close to the incoupling region 1 can be set to have a higher average refractive index. This design takes into account the optical characteristics and requirements of light when it first enters the diffractive optical structure. This helps to enhance the stability and transmission efficiency of the light in the initial stage, and ensures that the light can smoothly enter the inside of the substrate 3 from the coupling-in area 1 and propagate along a predetermined path.

[0086] (2) In the outcoupling area 2, matching the outcoupling requirements of different locations:

[0087] As the light is transmitted toward the rear end in the substrate 3, the reflection angle gradually decreases. In order to optimize the outcoupling efficiency, the grating structure in the outcoupling region 2 can adopt a gradually decreasing average refractive index. Designed to achieve more precise and efficient light outcoupling at different positions and angles. Especially at locations far from the coupling-in region 1, the lower average refractive index Ensure that light can still be efficiently coupled out at a smaller reflection angle.

[0088] (3) Able to optimize light transmission and outcoupling efficiency:

[0089] In the entire outcoupling region 2, the average refractive index of the grating structure is The gradient change design not only improves the transmission stability of light in the diffractive optical structure, but also significantly optimizes the overall outcoupling efficiency. By precisely controlling the physical parameters and refractive index distribution of the grating structure, the diffractive optical structure of the present application achieves precise control of the light transmission path and outcoupling angle, so that the light can maintain high transmission efficiency and outcoupling efficiency throughout the length of the substrate 3.

[0090] In general, in the outcoupling region 2, the average refractive index of the grating structure close to the coupling-in region 1 is is set to a higher value to ensure that light can be transmitted efficiently and stably in the initial stage. Gradually reduce to match the light outcoupling requirements at different locations and optimize the overall light transmission and outcoupling efficiency.

[0091] In some examples of this application, see Figure 2 and Figure 6 The grating structure includes a first periodic P 1, a plurality of grating ridges 201 arranged in an array, a grating groove 202 is provided between any two adjacent grating ridges 201, wherein at least a portion of the grating groove 202 is an air groove 203;

[0092] The average refractive index of different materials in the grating unit period of the grating structure as follows:

[0093] ;

[0094] in, = + +……+ , is the longitudinal cross-sectional area of ​​the grating ridge 201, is the refractive index of the grating ridge 201, is the longitudinal cross-sectional area of ​​the air slot 203, is the refractive index of air, The first 1 The longitudinal cross-sectional area of ​​the filling material, The first 1 The refractive index of the filling material, The first m The longitudinal cross-sectional area of ​​the filling material, The first m The refractive index of the filling material; = P 1* H , H is the height of the grating ridge 201 .

[0095] The grating structure provided in this example of the present application is a one-dimensional grating having a first period in only one direction. P 1.

[0096] In this example of the present application, the design of the grating structure aims to achieve the average refractive index of different materials within the grating unit period of the grating structure by filling at least one filling material and introducing the air groove 203. regulation.

[0097] As the light propagates in the optical waveguide, its reflection angle gradually changes. The grating structure design of the present application allows the average refractive index of different materials in the grating unit period of the grating structure to be adjusted according to the specific position and angle of light transmission. (Sometimes referred to as the average refractive index in this article ), so that the peak of the grating diffraction efficiency curve moves to the optimal position, thereby achieving efficient light outcoupling.

[0098] By precisely controlling the average refractive index of the grating structure The distribution of light makes the transmission path of light in the optical waveguide more stable, which improves the utilization rate and uniform distribution of light and reduces the light loss.

[0099] In general, the grating structure design provided by this application not only improves the light outcoupling efficiency, but also enhances the optical stability of the diffractive optical structure. It provides a clearer and more uniform visual experience for near-eye display devices such as augmented reality, and meets the complex and changeable light transmission and outcoupling requirements.

[0100] For a specific example, see Figure 2 When the longitudinal sections of the grating ridge 201 and the grating groove 202 are both rectangular, and the grating groove 202 is an air groove 203, the average refractive index of different materials in the grating unit period of the grating structure is for: =(K1*n1+K2*n2) / P 1, wherein K1 is the width of the grating ridge 201, n1 is the refractive index of the grating ridge 201, K2 is the width of the grating groove 202 (ie, the air groove 203), and n2 is the refractive index of air.

[0101] The longitudinal sections of the grating ridge 201 and the grating groove 202 are designed to be rectangular, and air is used entirely as the filling material of the grating groove 202, which simplifies the manufacturing process of the grating structure and the average refractive index. Calculation.

[0102] Although the design is simplified, the average refractive index of different materials within the grating unit period of the grating structure can still be effectively controlled by adjusting the width ratio of the grating ridge 201 and the air groove 203 (i.e., the value of K1 and K2). This control capability enables the grating structure to better match different light transmission and outcoupling requirements, improving the overall optical efficiency.

[0103] It is worth noting that due to the introduction of the air slot 203, the average refractive index of different materials within the grating unit period of the grating structure is The angular displacement of the diffraction efficiency curve can be reduced, allowing the peak of the diffraction efficiency curve to be moved to a more suitable angle position. This helps to achieve more efficient light outcoupling during light transmission, especially in the transmission and outcoupling of small-angle light.

[0104] In another specific example, see Figure 6 When the longitudinal sections of the grating ridge 201 and the grating groove 202 are both rectangular, the grating groove 202 includes at least one filling material (such as Figure 6 The 1 When the filling material 204 and the air slot 203 are both rectangular in longitudinal cross-section, the average refractive index of different materials in the grating unit period of the grating structure is for: =(K1*n1+K2*n2+K3*n3+……+K m *n m ) / P 1, wherein K1 is the width of the grating ridge 201, n1 is the refractive index of the grating ridge 201, K2 is the width of the air groove 203 in the grating groove 202 excluding the filling material, n2 is the refractive index of air, K3~K m are the widths of different filling materials filled in the grating groove 202, n3~n m are respectively the refractive indices of different filling materials filled in the grating groove 202 .

[0105] Please continue to see Figure 6 This design allows for flexible combination of one or more filling materials and air slots 203 in the grating slots 202. By adjusting the width ratio of various materials, the average refractive index of different materials in the grating unit period of the grating structure can be adjusted. This facilitates the optimization of light outcoupling in different application scenarios. At the same time, this precise control capability helps to move the peak of the grating diffraction efficiency curve to the optimal position, thereby achieving more efficient and uniform light outcoupling.

[0106] Optionally, the refractive index of the filling material in the grating groove 202 may be the same as the refractive index of the grating ridge 201. This design is equivalent to widening the width of the grating ridge 201 without changing the overall layout of the grating structure. This provides a new idea to adjust the average refractive index of different materials within the grating unit period of the grating structure. .

[0107] Of course, the refractive index of the filling material in the grating groove 202 may be different from the refractive index of the grating ridge 201. In this case, a material with a low refractive index may be used to partially fill the grating groove 202, and the air groove 203 needs to be retained, which is conducive to reducing the average refractive index of different materials in the grating unit period of the grating structure. .

[0108] In order to more flexibly adjust the average refractive index of different materials within the grating unit period of the grating structure , the refractive index of the grating ridge 201 and the grating groove 202 can be selected to be different. In this case, by filling the grating groove 202 with a material of low refractive index, the average refractive index of different materials in the grating unit period of the grating structure can be significantly reduced. This differentiated refractive index design not only broadens the average refractive index The wide control range also enables more precise control of the light outcoupling efficiency at different positions and angles.

[0109] In view of the fact that the front end of the outcoupling area has a higher outcoupling requirement for light with a larger total reflection angle, this application proposes a method of adjusting the average refractive index of the grating structure. The method to move the peak position of the efficiency curve. Figures 3 to 5 and Figure 7 The grating structure of the present application is analyzed.

[0110] 1. Initial stage:

[0111] At the front end of the outcoupling region 2, since only the light with a large total reflection angle is required to be outcoupled, the peak position of the outcoupling efficiency curve needs to be set at a large angle position. Figure 3 , by increasing the average refractive index of the grating structure The peak of the outcoupling efficiency curve is moved to a large angle position to meet the outcoupling requirements of the front end.

[0112] In a specific example, the refractive index n1 of the grating ridge 201 of the grating structure is 2.4, the refractive index n2 of the grating groove 202 is 1.4, and the duty cycle is 0.75. The calculation formula for the refractive index is is 2.15. Please continue to refer to Figure 3 At this time, the peak position of the coupling efficiency curve is around 59°.

[0113] 2. Intermediate stage:

[0114] As the light propagates away from the rear end of the coupling-in region 1, the reflection angle of the light gradually decreases, and the coupling-out requirement changes accordingly. In order to match this change, it is necessary to gradually reduce the average refractive index of the grating structure of the coupling-out region 2. , in order to move the peak of the outcoupling efficiency curve to a smaller angle. At this time, the average refractive index of the grating structure can be reduced. , see Figure 4 By adjusting the duty cycle to adjust the area ratio of the two materials in the grating structure, the size of the grating ridge 201 can be reduced or the refractive index of the grating ridge 201 or the grating groove 202 can be reduced. When the duty cycle is adjusted to 0.5, the average refractive index can be obtained. is 1.9.

[0115] Please continue to see Figure 4 , the peak position of the outcoupling efficiency curve is located at around 57°.

[0116] 3. Backend stage:

[0117] When the light reaches the end of the diffractive optical structure, the light reflection angle has been reduced to the minimum. At this time, the peak of the coupling efficiency curve should move to the minimum angle position to maximize the coupling efficiency of small-angle light. At this time, the duty cycle is adjusted to 0.25 to further reduce the average refractive index of the grating structure. is 1.65. Figure 5 , the peak position of the outcoupling efficiency curve is located at 54°.

[0118] It should be noted that in order to further reduce the average refractive index of different materials in the grating unit period of the grating structure of the outcoupling region 2 , the application also proposes a method of introducing air grooves.

[0119] Since the refractive index of air (the refractive index of air is 1) is much lower than that of other dielectric materials, introducing air as a filling material can significantly reduce the average refractive index of different materials within the grating unit period of the grating structure. , the average refractive index It can be further reduced to 1.35, so that the peak of the outcoupling efficiency curve moves further toward the small angle direction, ensuring efficient outcoupling of the last light. Figure 7 , the peak position of the coupling efficiency curve is located at 44°~45°.

[0120] In some examples of this application, see Fig.12 and Fig.13 The grating structure includes a plurality of grating ridges 201, wherein the plurality of grating ridges 201 are spaced apart from each other by a second period along a second direction. P 2 arrangement, and the third period interval along the third direction P 3, a grating groove 202 is formed between any two adjacent grating ridges 201, and at least a part of the grating groove 202 is an air groove 203;

[0121] The average refractive index of different materials in the grating unit period of the grating structure as follows:

[0122] ;

[0123] = + +……+ , is the volume of the grating ridge 201, is the refractive index of the grating ridge 201, is the volume of the air slot 203, is the refractive index of air, The first 1The volume of the filling material, The first 1 The refractive index of the filling material, The first m The volume of the filling material, The first m The refractive index of the filling material; =( P 2* P 3) * H , H is the height of the grating ridge 201 .

[0124] This example of the present application relates to a two-dimensional grating structure, which achieves the average refractive index of different materials in the grating unit period of the grating structure by precisely controlling the material composition and volume in the grating ridge 201 and the grating groove 202. Reasonable design.

[0125] The grating grooves 202 are located between adjacent grating ridges 201, and at least a portion of the grating grooves 202 are air grooves 203. Of course, the grating grooves 202 may also be filled with one or more different materials.

[0126] By precisely adjusting the material composition and volume of the grating ridges 201 and the grating grooves 202, the average refractive index of different materials within the grating unit period of the grating structure can be controlled. , thus achieving mobile control of the diffraction efficiency curve. This helps to improve the light outcoupling efficiency at a specific angle, especially in augmented reality (AR) optical schemes, which is crucial to improving the overall optical efficiency of the diffractive optical structure.

[0127] The two-dimensional grating structure in this example of the present application achieves fine control of the average refractive index of the grating structure by precisely controlling the material composition and volume distribution, thereby improving the diffraction efficiency and the overall optical performance of the diffraction optical structure.

[0128] In some examples of this application, see Figures 8 to 10 The grating structure further includes at least one layer of filling material, and the refractive index of the filling material is different from that of the grating ridge 201.

[0129] See also Figures 8 to 10 The grating structure may further include at least one layer of filling material having a different refractive index from the grating ridge 201 (the filling material may form a filling material layer covering the grating structure). This design introduces an additional degree of freedom for adjusting the refractive index.

[0130] The design of introducing the filling material can adopt a variety of manufacturing processes, such as ALD deposition, PVD deposition, CVD deposition, etc. These processes can accurately control the thickness of the formed filling material, thereby ensuring that the optical performance of the grating structure meets expectations.

[0131] In some examples of this application, see Figure 8 , the at least one layer of filling material comprises a 1 A filling material 204, the first 1 A filling material 204 covers the surface of the grating ridge 201 and the groove wall and groove bottom of the grating groove 202, wherein the grating groove 202 includes an air groove 203 and the first 1 A filling material 204 is provided.

[0132] In this example of the present application, the grating structure further comprises a 1 A filling material 204, the first 1 The first filling material 204 covers the surface of the grating ridge 201 and the groove wall and groove bottom of the grating groove 202, and a part of the space in the grating groove 202 is still reserved as an air groove 203. 1 The first filling material 204 may be a low refractive index material. 1 The introduction of the filling material 204 is the average refractive index of different materials in the grating unit period of the grating structure. Provides more control means. 1 The refractive index of the filling material can be precisely adjusted to adjust the average refractive index of different materials within the grating unit period of the grating structure. , thereby affecting the outcoupling efficiency curve of the grating structure.

[0133] Retaining the air grooves 203 makes it possible to further reduce the refractive index of the grating grooves 202 while ensuring structural stability.

[0134] In some examples of this application, see Fig. 9 , the at least one layer of filling material comprises a 2 A filling material 205, the first 2 The first filling material 205 is disposed on the first filling material 204, and the grating groove 202 includes the first filling material 205. 2 A filling material 205 is provided, while retaining an air slot 203, wherein the first 1 The filling material 204 and the 2 The refractive indexes of the filling materials 205 are different.

[0135] See also Fig. 9 , this example is in the 1On the basis of the filling material 204, the 2 A filling material 205 is formed, and at the same time, a part of the space is reserved in the grating groove 202 as an air groove 203. 1 The first filling material 204 and the second 2 The refractive indexes of the filling materials 205 are different.

[0136] By adding another layer 1 The first filling material 204 has a different refractive index. 2 The filling material 205 can further broaden the average refractive index of different materials within the grating unit period of the grating structure. This helps to precisely control the outcoupling efficiency over a wider angle range. The design introduced by the multi-layer filling material allows the peak position and shape of the efficiency curve to be more finely regulated to meet the specific needs of different application scenarios.

[0137] In some examples of this application, see Fig.10 The at least one layer of filling material also includes a 3 A filling material 206, the first 3 The first filling material 206 covers the 2 The first filling material 205 is away from the first 1 On the surface of the first filling material 204, the grating groove 202 also includes the first 3 A filling material 206, and the first 3 A filling material 206 fills the air groove 203; wherein the first 1 The filling material 204, the 2 The filling material 205 and the 3 The refractive indexes of the filling materials 206 are different.

[0138] In this example, see Fig.10 The grating structure also includes a 1 Filling material 204, 2 The filling material 205 and the 3 The three layers of filling materials 206 have different refractive indices. The combination of the three layers of filling materials with different refractive indices makes the average refractive index of different materials in the grating unit period of the grating structure The regulation has achieved higher precision, which provides strong support for the precise control of the diffraction efficiency curve of the grating.

[0139] In addition, filling materials with different refractive indices may bring different optical properties, such as different transmittance, scattering properties, etc. The combination of these properties can make the grating structure show diverse optical performance under different conditions.

[0140] In summary, see Figures 8 to 10 The three examples achieve the average refractive index of different materials in the grating unit period of the grating structure of the outcoupling region 2 by introducing filling materials of different quantities and different refractive indices and retaining the air slot 203 and other design means. These designs not only help to improve the overall optical efficiency of diffractive optical structures, but also provide more reliable and flexible technical support for applications in fields such as augmented reality.

[0141] According to another embodiment of the present application, a near-eye display device is provided, which includes an image source and the diffractive optical structure as described above, wherein light emitted by the image source can be incident on an incoupling region 1 on the diffractive optical structure.

[0142] The image source is, for example, a projection light machine.

[0143] The diffractive optical structure is, for example, a diffractive optical waveguide.

[0144] The near-eye display device provided in the embodiment of the present application is, for example, an AR optical display device. Further, the AR optical display device is, for example, AR smart glasses or an AR smart helmet.

[0145] The specific implementation of the near-eye display device of the embodiment of the present application can refer to the above-mentioned embodiments of the diffraction optical structure, so it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here one by one.

[0146] The above embodiments focus on the differences between the various embodiments. As long as the different optimization features between the various embodiments are not contradictory, they can be combined to form a better embodiment. Considering the simplicity of the text, they will not be repeated here.

[0147] Although some specific embodiments of the present application have been described in detail by way of example, it should be understood by those skilled in the art that the above examples are only for illustration, not for limiting the scope of the present application. It should be understood by those skilled in the art that the above embodiments may be modified without departing from the scope and spirit of the present application. The scope of the present application is defined by the appended claims.

Claims

1. A diffractive optical structure, characterized in that: It comprises a substrate (3) and a coupling-in region (1) and a coupling-out region (2) arranged on the substrate (3); The outcoupling region (2) comprises a grating structure, the grating structure comprises a plurality of periodically arranged grating ridges (201) and grating grooves (202) between adjacent grating ridges (201), and the grating grooves (202) are filled with at least two materials with different refractive indices; The average refractive index of different materials within the grating unit period of the grating structure is: , and 1.1< ≤2.4, ,in, V 1~ V m Respectively 1 Materials to m The volume or area of ​​a material, n 1~ n m Respectively 1 Materials to m The refractive index of a material, V unitcell is the volume or area per unit period of the grating.

2. The diffractive optical structure according to claim 1, characterized in that: The average refractive index of different materials in the grating unit period of the grating structure 1.35≤ ≤2.

15.

3. The diffractive optical structure according to claim 1, characterized in that: The substrate (3) comprises two opposite surfaces, and the coupling-in region (1) and the coupling-out region (2) are arranged on at least one surface of the substrate (3); The coupling-in region (1) is used to couple external light into the interior of the substrate (3); The outcoupling area (2) is used to expand the pupil of light and couple it out.

4. The diffractive optical structure according to any one of claims 1 to 3, characterized in that: The grating structure includes a first period along a first direction P 1, a plurality of grating ridges (201) arranged in an array, the grating grooves (202) being between any two adjacent grating ridges (201), wherein at least a portion of the grating grooves (202) are air grooves (203); The average refractive index of different materials in the grating unit period of the grating structure as follows: ； in, = + +……+ , is the longitudinal cross-sectional area of ​​the grating ridge (201), is the refractive index of the grating ridge (201), is the longitudinal cross-sectional area of ​​the air groove (203), is the refractive index of air, is the first 1 The longitudinal cross-sectional area of ​​the filling material, is the first 1 The refractive index of the filling material, is the first m The longitudinal cross-sectional area of ​​the filling material, is the first m The refractive index of the filling material; = P 1* H , H is the height of the grating ridge (201).

5. The diffractive optical structure according to any one of claims 1 to 3, characterized in that: The grating structure comprises a plurality of grating ridges (201), wherein the plurality of grating ridges (201) are spaced at a second period along a second direction. P 2 arrangement, and the third period interval along the third direction P 3, a grating groove (202) is provided between any two adjacent grating ridges (201), and at least a portion of the grating groove (202) is an air groove (203); The average refractive index of different materials in the grating unit period of the grating structure as follows: ； = + +……+ , is the volume of the grating ridge (201), is the refractive index of the grating ridge (201), is the volume of the air slot (203), is the refractive index of air, is the first 1 The volume of the filling material, is the first 1 The refractive index of the filling material, is the first m The volume of the filling material, is the first m The refractive index of the filling material; =( P 2* P 3) * H , H is the height of the grating ridge (201).

6. The diffractive optical structure according to any one of claims 1 to 3, characterized in that: The grating structure is covered with at least one layer of filling material, and the refractive index of the filling material is different from the refractive index of the grating ridge (201).

7. The diffractive optical structure according to claim 6, characterized in that: The at least one layer of filling material includes 1 a filling material (204), the 1 A filling material (204) covers the surface of the grating ridge (201) and the groove wall and groove bottom of the grating groove (202), wherein the grating groove (202) includes an air groove (203) and the first 1 A filling material (204).

8. The diffractive optical structure according to claim 7, characterized in that: The at least one layer of filling material further comprises a 2 a filling material (205), the 2 A filling material (205) covers the first 1 The grating groove (202) further comprises the first filling material (204). 2 a filling material (205) and retaining an air groove (203), wherein the first 1 The filling material (204) and the 2 The refractive indices of the two filling materials (205) are different.

9. The diffractive optical structure according to claim 8, characterized in that: The at least one layer of filling material further comprises a 3 a filling material (206), the 3 A filling material (206) covers the first 2 The first filling material (205) is away from the first 1 On the surface of the first filling material (204), the grating groove (202) also includes the first 3 a filling material (206), and the 3 A filling material (206) fills the air groove (203); Among them, the 1 a filling material (204), the 2 A filling material (205) and the 3 The refractive indices of the filling materials (206) are different.

10. A near-eye display device, characterized in that: include: Image source; and According to the diffractive optical structure as claimed in any one of claims 1 to 9, the light emitted by the image source can be incident on the coupling-in region (1) on the diffractive optical structure.

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