Diffractive optical structure and optical display device

Abstract

The embodiment of the present application discloses a diffractive optical structure and an optical display device; wherein the diffractive optical structure comprises a substrate and a grating structure arranged on the substrate, wherein the grating structure comprises a plurality of grating units periodically arranged on the surface of the substrate along a first direction and a second direction; the grating structure has a first grating modulation direction and a second grating modulation direction, wherein the first grating modulation direction is perpendicular to the first direction, and the grating modulation amount in the first grating modulation direction is △E, △E=1 / (P3*sin i ), wherein P3 is the period of the grating structure in the second direction, i is the angle between the first direction and the second direction; the light incident on the grating structure generates diffraction behavior only in the first grating modulation direction, and does not generate diffraction behavior in the second grating modulation direction.

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 an optical display device. Background Art

[0002] As an emerging human-computer interaction method, augmented reality (AR) technology has shown great application potential in education, entertainment, industry and other fields. As one of the mainstream technical solutions for realizing AR technology, diffractive optical structure transmits images losslessly to the wearer's eyes through the total reflection of the transparent substrate, realizing the superposition and fusion of the real world and virtual images. In the diffractive optical structure, the grating plays a vital role in controlling the coupling, propagation and decoupling process of light. Traditional one-dimensional gratings modulate the diffraction efficiency of the grating by adjusting parameters such as line width, depth, and side wall angle. However, due to the difficulty and maturity of existing processes, this modulation method is often costly and has limited effect, and it is difficult to meet the high requirements of diffractive optical structures for overall efficiency and uniformity. Summary of the invention

[0003] The purpose of this application is to provide a technical solution for a diffractive optical structure and an optical display device.

[0004] According to a first aspect of the present application, the present application provides a diffractive optical structure, the diffractive optical structure comprising a substrate and a grating structure arranged on the substrate, the grating structure comprising a plurality of grating units periodically arranged on a surface of the substrate along a first direction and a second direction;

[0005] The grating structure has a first grating modulation direction and a second grating modulation direction, the first grating modulation direction is perpendicular to the first direction, and the grating modulation amount in the first grating modulation direction is △E, △E=1 / (P3*sin θ ), wherein P3 is the period of the grating structure in the second direction, θ is the angle between the first direction and the second direction;

[0006] The light incident on the grating structure generates diffraction behavior only in the first grating modulation direction, and does not generate diffraction behavior in the second grating modulation direction.

[0007] Optionally, a period of the grating structure in the first direction is P2, and P2<P3.

[0008] Optionally, the angle between the first direction and the second direction is θ 0< θ ≤90°.

[0009] Optionally, the diffractive optical structure includes an in-coupling grating, an out-coupling grating and a turning grating;

[0010] At least a partial region of at least one of the coupling-in grating, the coupling-out grating and the turning grating includes the grating structure.

[0011] Optionally, at least a portion of the turning grating is the grating structure; or,

[0012] The coupling-in grating and the turning grating are the grating structure; or,

[0013] The coupling-in grating, a partial region of the coupling-out grating and the turning grating constitute the grating structure.

[0014] Optionally, the period P2 of the grating structure in the first direction is less than 300 nm, and after the light is diffracted by the grating structure, the light only generates first-order diffraction behavior in the first grating modulation direction, and does not generate diffraction behavior in the second grating modulation direction.

[0015] Optionally, the coupling grating adopts the grating structure, and when the grating structure satisfies the following conditions, light in at least some directions within the incident FOV does not generate diffraction behavior in the second grating modulation direction after being modulated by the grating structure;

[0016]

[0017] in, is the grating modulation amount of any point within the FOV of the grating structure;

[0018] n2 is the refractive index of the substrate;

[0019] is the second grating modulation direction.

[0020] Optionally, the coupling grating adopts the grating structure, and when the grating structure satisfies the following conditions, light in at least some directions within the incident FOV generates first-order diffraction only in the first grating modulation direction after being modulated by the grating structure;

[0021]

[0022] in, is the grating modulation amount of any point within the FOV of the grating structure;

[0023] n2 is the refractive index of the substrate;

[0024] is the first grating modulation direction;

[0025] is the second grating modulation direction.

[0026] Optionally, the turning grating or the outcoupling grating adopts the grating structure, and when the grating structure satisfies the following conditions, light within the incident FOV or at least in a partial direction does not generate diffraction behavior in the second grating modulation direction after being modulated by the grating structure;

[0027]

[0028] in, is the grating modulation amount of any point within the FOV of the grating structure;

[0029] is the grating modulation amount of the coupled-in grating;

[0030] n2 is the refractive index of the substrate;

[0031] is the second grating modulation direction.

[0032] Optionally, the turning grating or the outcoupling grating adopts the grating structure, and when the grating structure satisfies the following conditions, light in at least some directions within the incident FOV generates first-order diffraction only in the first grating modulation direction after being modulated by the grating structure;

[0033]

[0034] in, is the grating modulation amount of any point within the FOV of the grating structure;

[0035] is the grating modulation amount of the coupled-in grating;

[0036] n2 is the refractive index of the substrate;

[0037] is the first grating modulation direction;

[0038] is the second grating modulation direction.

[0039] Optionally, the outcoupling grating adopts the grating structure, and when the grating structure satisfies at least one of the following conditions, light in at least part of the directions within the incident FOV does not generate diffraction behavior in the second grating modulation direction after being modulated by the grating structure;

[0040]

[0041] in, is the grating modulation amount of any point within the FOV of the grating structure;

[0042] is the grating modulation amount of the coupled-in grating;

[0043] is the grating modulation amount of the turning grating;

[0044] is the grating modulation amount of the outcoupling grating;

[0045] n2 is the refractive index of the substrate;

[0046] is the first grating modulation direction;

[0047] is the second grating modulation direction.

[0048] Optionally, the outcoupling grating adopts the grating structure, and when the grating structure satisfies at least one of the following conditions, light rays in at least some directions within the incident FOV range, after being modulated by the grating structure, only generate first-order diffraction in the first grating modulation direction;

[0049]

[0050] in, is the grating modulation amount of any point within the FOV of the grating structure;

[0051] is the grating modulation amount of the coupled-in grating;

[0052] is the grating modulation amount of the turning grating;

[0053] is the grating modulation amount of the outcoupling grating;

[0054] n2 is the refractive index of the substrate;

[0055] is the first grating modulation direction;

[0056] is the second grating modulation direction.

[0057] Optionally, the grating unit is a columnar structure arranged on the surface of the substrate, and a line width ratio of the grating unit in the first direction is DC, 0<DC<1.

[0058] Optionally, the grating unit is a hole-shaped structure arranged on the surface of the substrate, and a line width ratio of the grating unit in the first direction is DC, 0<DC<1.

[0059] Optionally, the grating unit includes one or more sub-gratings.

[0060] Optionally, the diffractive optical structure is an optical waveguide device.

[0061] According to a second aspect of the present application, an embodiment of the present application provides an optical display device, the optical display device comprising:

[0062] the image source; and

[0063] A diffractive optical structure as described in the first aspect.

[0064] One beneficial effect of the embodiments of the present application is:

[0065] This application aims to solve the problem of low modulation efficiency, high process cost and difficulty in comprehensively optimizing the overall efficiency and uniformity of one-dimensional grating in existing diffraction optical technology. The grating structure design in this application abandons the complex modulation requirements for grating depth or side wall angle on the basis of keeping the diffraction pattern of one-dimensional grating unchanged, and instead relies on the existing low-cost and mature mass production process to flexibly adjust the key parameters of two-dimensional grating in one dimension, thereby realizing free modulation of grating diffraction efficiency in a wide range. The technical solution provided by this application greatly improves the overall optical efficiency and uniformity of the diffraction optical structure, including brightness, color and eye box uniformity, and provides a better optical design solution for augmented reality display technology.

[0066] 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

[0067] 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.

[0068] Figure 1 One of the structural schematic diagrams of the diffractive optical structure provided in the embodiment of the present application;

[0069] Figure 2 The second structural schematic diagram of the diffractive optical structure provided in the embodiment of the present application;

[0070] Figure 3 The third structural schematic diagram of the diffractive optical structure provided in the embodiment of the present application;

[0071] Figure 4A fourth structural schematic diagram of a diffractive optical structure provided in an embodiment of the present application;

[0072] Figure 5 is a schematic diagram of the structure of a conventional one-dimensional grating;

[0073] Figure 6 It is a schematic diagram of the structure of a conventional two-dimensional grating;

[0074] Figure 7 One of the structural schematic diagrams of the grating structure provided in the embodiment of the present application;

[0075] Figure 8 It is the K-vector diagram of the traditional one-dimensional grating;

[0076] Fig. 9 One of the K-vector diagrams of the grating structure provided in the embodiment of the present application;

[0077] Fig.10 The second K-vector diagram of the grating structure provided in the embodiment of the present application;

[0078] Fig.11 The second structural schematic diagram of the grating structure provided in the embodiment of the present application;

[0079] Fig.12 The third structural schematic diagram of the grating structure provided in the embodiment of the present application;

[0080] Fig.13 A fourth structural schematic diagram of the grating structure provided in an embodiment of the present application;

[0081] Fig.14 One of the side views of the grating structure provided in the embodiment of the present application;

[0082] Fig.15 A second side view of the grating structure provided in an embodiment of the present application;

[0083] Fig.16 The third side view of the grating structure provided in the embodiment of the present application;

[0084] Fig.17 A fourth side view of the grating structure provided in an embodiment of the present application;

[0085] Fig.18 for Fig.15 A top view of the grating structure is shown;

[0086] Fig.19 The second structural schematic diagram of the grating structure provided in the embodiment of the present application;

[0087] Fig. 20 The third structural schematic diagram of the grating structure provided in the embodiment of the present application;

[0088] Fig.21 for Fig. 20 Diffraction efficiency diagram of the grating structure shown;

[0089] Fig. 22 A fourth structural schematic diagram of the grating structure provided in an embodiment of the present application;

[0090] Fig.23 for Fig. 22 Diffraction efficiency diagram of the grating structure shown;

[0091] Fig.24 This is the diffraction efficiency diagram within the FOV of a traditional one-dimensional grating;

[0092] Fig.25 A diffraction efficiency diagram within the FOV of a grating structure provided in this application;

[0093] Fig.26 This is a diffraction efficiency diagram within the FOV of another grating structure provided in this application.

[0094] Description of reference numerals:

[0095] 1. Substrate; 2. In-coupling grating; 3. Out-coupling grating; 4. Turning grating; 5. Grating structure; 51. Grating unit. DETAILED DESCRIPTION

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] The diffractive optical structure and the optical display device provided in the embodiments of the present application are described in detail below in conjunction with the accompanying drawings.

[0102] According to one embodiment of the present application, a diffractive optical structure is provided. Figures 1 to 4 , the diffractive optical structure comprises a substrate 1 and a grating structure 5 arranged on the substrate 1; see Figure 7 The grating structure 5 includes a plurality of grating units 51 periodically arranged on the surface of the substrate 1 along a first direction and a second direction; the grating structure 5 has a first grating modulation direction and a second grating modulation direction, the first grating modulation direction is perpendicular to the first direction, and the grating modulation amount in the first grating modulation direction is △E, △E=1 / (P3*sin θ ), wherein P3 is the period of the grating structure 5 in the second direction, θ is the angle between the first direction and the second direction; the light incident on the grating structure generates diffraction behavior only in the first grating modulation direction, and does not generate diffraction behavior in the second grating modulation direction.

[0103] It should be noted that, the fact that no diffraction behavior occurs in the second grating modulation direction mentioned in the above embodiment means that the diffraction behavior in the second grating modulation direction is suppressed or minimized.

[0104] The diffractive optical structure provided in the embodiment of the present application is, for example, a diffractive optical waveguide device, wherein the grating structure 5 can be used for any one or at least one of the coupling-in grating 2, the coupling-out grating 3 and the turning grating 4 on the diffractive optical waveguide device, see Figures 1 to 4 , which is not limited in this application.

[0105] In augmented reality (AR) technology, diffraction waveguide devices are key optical components for image transmission and display. Currently, one-dimensional gratings are widely used in diffraction waveguide devices, and the diffraction efficiency is modulated by adjusting its parameters such as line width, depth, sidewall angle, etc. However, this modulation method is limited by process difficulty and cost, especially in the adjustment of depth and sidewall angle, which is often difficult to achieve or costly. In addition, the improvement of diffraction efficiency by line width adjustment alone is limited, which affects the overall efficiency and uniformity of optical waveguide devices.

[0106] In order to overcome the above defects, an embodiment of the present application provides a specially designed grating structure 5. Specifically, the grating structure 5 is similar to a two-dimensional grating in optical structure design, but the diffraction performance of the grating structure 5 is similar to a one-dimensional grating.

[0107] See also Figure 5 , Figure 5 shows the structure of a conventional one-dimensional grating. Figure 5 It can be seen from the figure that the multiple grating units are arranged in a period P1 in the same direction.

[0108] See also Figure 6 , Figure 6 shows the structure of a conventional two-dimensional grating. Figure 6 It can be seen that multiple grating units are arranged periodically along two different directions, with a period of P2 in one direction and a period of P3 in the other direction. Figure 5 The direction of the period P1 of the one-dimensional grating is vertical, and a repetition period P3 is introduced in any other direction, which is a conventional two-dimensional grating structure.

[0109] See also Figure 7 The grating structure in this application introduces a periodic tiling arrangement in the second direction on the basis of maintaining the one-dimensional grating diffraction pattern, see Figure 7 , forming a new type of grating unit layout design. The grating design provided by the present application does not require complex modulation of the depth or sidewall angle of the grating unit, but achieves more flexible and effective modulation of the grating diffraction efficiency of the grating structure by adjusting the parameters in the second direction (such as period, line width).

[0110] The grating structure provided in this application is shown in Figure 7 , while maintaining the one-dimensional diffraction characteristics, the grating diffraction efficiency can be modulated by adjusting the parameters in the second direction, such as period P3, line width, etc. This modulation method does not rely on the depth or sidewall angle adjustment, which is more difficult to process, but uses mature low-cost processes, thereby significantly improving the overall efficiency of the diffraction optical structure and the uniformity of brightness, color, and eye box.

[0111] Compared with the high cost of depth and sidewall angle adjustment of traditional one-dimensional gratings, see Figure 7 The present application reduces the process difficulty and cost by adjusting the more easily controllable parameters such as the period P3 in the second direction, making this high-performance grating structure easier to achieve large-scale production and application.

[0112] According to the description in the above embodiments of the present application, the light incident on the grating structure generates effective diffraction behavior only in the first grating modulation direction, while the diffraction behavior in the second grating modulation direction is suppressed or minimized. This characteristic helps to reduce stray light and unnecessary diffraction effects, and improve the quality and clarity of the image.

[0113] In summary, the grating structure proposed in the embodiment of the present application demonstrates significant technical advantages in improving the overall efficiency and uniformity of the diffraction optical structure, while reducing process costs, enhancing design flexibility and practicality, and providing a new solution for the development of optical display technologies such as augmented reality.

[0114] See also Figures 8 to 10 , Figure 8 The K-vector diagram of a conventional one-dimensional grating is shown. Fig. 9 and Fig.10 are all K-vector diagrams of the grating structure 5 provided in the embodiments of the present application. Figure 8 compared to, Fig. 9 λ / P3·sin θ The length and Figure 8 λ / P1 is basically the same, which indicates that the grating structure of the present application is grating modulated in the P2 direction, resulting in diffraction behavior. Fig. 9 Also shown in FIG. 5 are four oblique lines extending from the four vertices of the rectangular dotted frame in the figure. These four oblique lines are all moved out of the outermost circle, which indicates that there is no diffraction behavior in another dimension of the grating structure 5. Fig.10 and Fig. 9 The difference is that the grating structure 5 does not directly modulate the incident light, that is, the grating structure 5 is not applied to the coupling grating of the diffraction optical structure, and the light is modulated before being incident on the grating structure 5 for modulation. It can be seen that Fig.10 Eight oblique lines in FIG. 5 also move out of the outermost circle, which indicates that there is no diffraction in another dimension of the grating structure 5 .

[0115] In some examples of this application, see Figure 7 , the period of the grating structure 5 in the first direction is P2, and P2<P3.

[0116] According to the diffraction optical structure provided by the embodiment of the present application, the grating structure 5 therein has period differences in two directions.

[0117] In grating design, period is a key parameter that directly affects the diffraction characteristics of the grating.

[0118] In the diffraction optical structure provided in the embodiment of the present application, the grating structure has two grating modulation directions: a first grating modulation direction and a second grating modulation direction; wherein the first grating modulation direction is the grating modulation direction in which normal diffraction is desired, and the second grating modulation direction is an invalid direction, and the light will not diffract. It should be noted that the first grating modulation direction is affected by the period P2 in the first direction, and the second grating modulation direction is affected by the period P3 in the second direction.

[0119] The grating structure of the present application, in which the period P2 in the first direction is smaller than the period P3 in the second direction, can result in a stronger diffraction or interference effect in the first direction, because a denser period means more grating lines interacting with light.

[0120] Regarding the diffraction performance of the grating structure of this application, the specific analysis is as follows:

[0121] The light incident on the grating structure only produces significant diffraction behavior in the first grating modulation direction (related to P2), while the diffraction in the second grating modulation direction (related to P3) is suppressed or minimized. This design helps to achieve more precise and efficient optical control.

[0122] Specifically, the grating structure provided in the embodiment of the present application can enhance the diffraction efficiency, which is specifically manifested in that the period P2 in the first direction makes the diffraction of light in this direction more intense and effective, which is beneficial to the light energy transmission efficiency of the optical waveguide device during coupling, coupling or turning. The grating structure provided in the embodiment of the present application can also optimize the optical performance, which is specifically manifested in that the period P3 in the second direction effectively suppresses the diffraction in the unintended direction, reduces the stray light and energy loss, and improves the clarity and contrast of the image. By optimizing the period in two directions, the scheme of the present application achieves fine control of the grating diffraction efficiency on the basis of maintaining the basic diffraction characteristics of the one-dimensional grating, thereby improving the uniformity of the diffraction optical structure in terms of brightness, color and eye box.

[0123] In some examples of this application, see Figure 7 and Fig. 20 , the angle between the first direction and the second direction θ 0< θ ≤90°.

[0124] The grating structure 5 has a period P2 in the first direction and a period P3 in the second direction, and a certain angle is formed between the first direction and the second direction. θ , the angle θ The design allows the grating structure to be flexibly arranged in a plane to meet different optical system requirements. θ The value can also control the diffraction intensity of the grating structure 5 in different directions to a certain extent, and optimize the propagation path of the light.

[0125] When the angle θ When the diffraction of the grating structure is within the above range, the diffraction in two directions will show different characteristics. The first direction (the direction of the period P2) will dominate the main diffraction effect, while the second direction (the direction of the period P3) may be used for subtle diffraction adjustment or suppression.

[0126] In addition, the angle θ The setting increases the design freedom of the grating structure. The layout and parameters of the grating can be flexibly adjusted according to specific application scenarios and performance requirements to achieve the best optical effect.

[0127] According to the angle between the first direction and the second direction mentioned in this example of the present application θ The diffraction direction can be precisely controlled within this range. θ The diffraction direction of the grating can be precisely controlled so that the light propagates along the predetermined path. θ The design helps balance the diffraction effects in two directions, reduce unnecessary diffraction losses, and improve image clarity. θ The optimization enables the grating structure to more effectively couple light into or out of the diffractive optical structure, improving the overall efficiency of the diffractive optical structure.

[0128] In summary, the setting range of the angle θ between the first direction and the second direction in the present application example (0< θ ≤90°) is a design option with high flexibility and optimized space. It can achieve fine control of optical performance by adjusting the angle θ while ensuring the basic diffraction characteristics of the grating, thereby improving the overall efficiency and optical performance of the diffractive optical structure.

[0129] In some examples of this application, see Figures 1 to 4 The diffraction optical structure includes a coupling-in grating 2, a coupling-out grating 3 and a turning grating 4; at least a partial area of ​​at least one of the coupling-in grating 2, the coupling-out grating 3 and the turning grating 4 includes the grating structure.

[0130] The diffractive optical structure provided in the embodiments of the present application is shown in FIG. Figures 1 to 4 , a coupling-in grating 2, a coupling-out grating 3 and a turning grating 4 are integrated on the substrate 1, and these functional gratings play a key role in the diffraction optical structure.

[0131] Specifically, the coupling-in grating 2 is responsible for effectively coupling the light projected by the external light source into the interior of the substrate 1, the coupling-out grating 3 couples the light out of the substrate 1 into the eyes of the wearer / user, and the turning grating 4 is located on the optical path between the coupling-in grating 2 and the coupling-out grating 3, and is used to change the propagation direction of the light to achieve pupil expansion or redirection of the image.

[0132] In this example of the present application, the grating structure 5 is adopted in part or all of the area of ​​at least one functional grating (such as the coupling-in grating 2, the coupling-out grating 3 or the turning grating 4) on the substrate 1. This structure can significantly improve the diffraction efficiency of the grating and optimize the overall efficiency and uniformity of the diffraction optical structure without increasing the complexity of the process by adjusting parameters such as the line width, groove width, and period in one dimension.

[0133] Due to the optimization of the grating structure 5, the entire diffractive optical structure can more effectively utilize light energy during the coupling-in, coupling-out and turning process of light, reduce energy loss, and improve image brightness, color uniformity and eye box uniformity.

[0134] The optimized grating structure significantly improves the diffraction efficiency of light during coupling-in, coupling-out and turning processes, thereby improving the overall utilization of light energy and making the diffractive optical structure brighter and clearer when displayed.

[0135] The diffraction optical structure provided in the embodiment of the present application, wherein at least a portion of at least one of the coupling-in grating 2, the coupling-out grating 3 and the turning grating 4 adopts the grating structure provided in the present application, can enhance the imaging quality. This is because, by optimizing the grating structure, stray light and unnecessary diffraction loss are reduced, the clarity and contrast of the image are improved, and the fusion of the virtual image and the real world is made more natural and realistic.

[0136] The efficient diffractive optical structure enables the optical waveguide device to have better uniformity in brightness, color and eye box, reducing visual fatigue and discomfort, and improving the user's overall experience when using augmented reality devices.

[0137] The design of the diffractive optical structure in the example of this application achieves a significant improvement in the overall performance and user experience of the diffractive optical structure by integrating the optimized grating structure 5. This design not only improves the light energy utilization and image quality, but also reduces the production cost and process difficulty, providing support for the development of augmented reality technology.

[0138] In some examples of this application, see Figure 1 and Figure 2 , at least a portion of the turning grating 4 is the grating structure 5; or, see Figure 3 , the coupling grating 2 and the turning grating 4 are the grating structure 5; or, see Figure 4 The coupling-in grating 2 , a partial area of ​​the coupling-out grating 3 , and the turning grating 4 constitute the grating structure 5 .

[0139] In one example, see Figure 1 The turning grating 4 includes a first region 41 and a second region 42 , wherein the first region 41 is set as the grating structure 5 .

[0140] In one example, see Figure 2 , the turning grating 4 is configured as the grating structure 5 as a whole.

[0141] In both of the above methods, see Figure 1 and Figure 2The grating structure 5 is used in part or all of the turning grating 4. This design makes it possible to more effectively utilize the diffraction characteristics of the grating structure when the light is turned inside the diffractive optical structure, and control the turning angle and intensity distribution of the light.

[0142] The optimized grating structure 5 can reduce the energy loss of light during the turning process, improve the turning efficiency, and keep the image clear and bright in a wider field of view. By precisely controlling the diffraction behavior of the turning grating 4, the uniformity of the eye box of the diffractive optical structure can be improved to ensure consistent image quality at different viewing angles.

[0143] In one example, see Figure 3 The coupling grating 2 and the turning grating 4 both adopt the grating structure 5. This design not only optimizes the coupling efficiency of light, but also improves the turning performance of light inside the diffractive optical structure.

[0144] By optimizing the coupling grating 2 and the turning grating 4, the diffractive optical structure can maintain a high overall efficiency during the light transmission and turning process, and improve the brightness and color uniformity of the image. By optimizing the turning grating 4, the viewing angle range of the diffractive optical structure can be expanded.

[0145] In one example, see Figure 4 , the coupling-in grating 2, a partial area of ​​the coupling-out grating 3 and the turning grating 4 are the grating structure 5, wherein the coupling-out grating 3 includes a first area 31, a second area 32 and a third area 33, and the second area 32 is located between the first area 31 and the third area 33, and the second area 32 is the grating structure 5. This comprehensive optimization design ensures that the diffraction optical structure can perform optimally in the coupling-in, transmission, turning and outcoupling processes of light.

[0146] Due to the all-round optimization of the coupling-in grating 2, the coupling-out grating 3 and the turning grating 4, the diffractive optical structure has been significantly improved in terms of brightness, color uniformity, eye box uniformity and field of view. The efficient diffractive optical structure makes the augmented reality device clearer, more natural and more comfortable when displaying, greatly improving the user's visual experience.

[0147] According to the above examples, the present application improves the performance of the diffractive optical structure by flexibly applying the grating structure 5 to different functional grating parts of the diffractive optical structure. Whether optimizing the turning grating alone, optimizing the coupling-in grating and the turning grating at the same time, or comprehensively optimizing the coupling-in, coupling-out and turning grating, the efficiency, uniformity and user experience of the diffractive optical structure can be improved to varying degrees.

[0148] In some examples of the present application, the period P2 of the grating structure 5 in the first direction is less than 300 nm, and after the light is diffracted by the grating structure 5, it only generates first-order diffraction behavior in the first grating modulation direction, and does not generate diffraction behavior in the second grating modulation direction.

[0149] The diffraction optical structure provided in the present application, wherein the grating structure 5 satisfies a specific optical relationship: the first grating modulation direction is perpendicular to the first direction, and the grating modulation amount in the first grating modulation direction is △E, △E=1 / (P3*sin θ ), the conditions in this example of the present application are also met, that is, the constraint on the period P2 of the grating structure 5 in the first direction. Only in this way can it be fully ensured that the grating structure 5 is a grating modulation direction for normal diffraction work in only one direction, and the other direction is an invalid direction.

[0150] Furthermore, a period P2 of the grating structure 5 in the first direction is less than 250 nm.

[0151] Furthermore, a period P2 of the grating structure 5 in the first direction is less than 200 nm.

[0152] In a specific example of the present application, the coupling grating 2 adopts the grating structure 5. When the grating structure 5 satisfies the following conditions, light in at least part of the directions within the incident FOV does not generate diffraction behavior in the second grating modulation direction after being modulated by the grating structure 5;

[0153]

[0154] in, is the grating modulation amount of any point within the FOV of the grating structure 5;

[0155] n2 is the refractive index of the substrate 1;

[0156] is the second grating modulation direction.

[0157] In a specific example of the present application, the coupling grating 2 adopts the grating structure 5. When the grating structure 5 satisfies the following conditions, the light in at least some directions within the incident FOV generates first-order diffraction only in the first grating modulation direction after being modulated by the grating structure 5;

[0158]

[0159] in, is the grating modulation amount of any point within the FOV of the grating structure 5;

[0160] n2 is the refractive index of the substrate 1;

[0161] is the first grating modulation direction;

[0162] is the second grating modulation direction.

[0163] In a specific example of the present application, the turning grating 4 or the outcoupling grating 3 adopts the grating structure 5. When the grating structure 5 satisfies the following conditions, the light in at least part of the directions within the incident FOV does not generate diffraction behavior in the second grating modulation direction after being modulated by the grating structure 5;

[0164]

[0165] in, is the grating modulation amount of any point within the FOV of the grating structure 5;

[0166] is the grating modulation amount of the coupled-in grating 2;

[0167] n2 is the refractive index of the substrate 1;

[0168] is the second grating modulation direction.

[0169] In a specific example of the present application, the turning grating 4 or the outcoupling grating 3 adopts the grating structure 5. When the grating structure 5 satisfies the following conditions, light in at least some directions within the incident FOV generates first-order diffraction only in the first grating modulation direction after being modulated by the grating structure 5;

[0170]

[0171] in, is the grating modulation amount of any point within the FOV of the grating structure 5;

[0172] is the grating modulation amount of the coupled-in grating 2;

[0173] n2 is the refractive index of the substrate 1;

[0174] is the first grating modulation direction;

[0175] is the second grating modulation direction.

[0176] In a specific example of the present application, the outcoupling grating 3 adopts the grating structure, and when the grating structure 5 satisfies at least one of the following conditions, light in at least part of the directions within the incident FOV does not generate diffraction behavior in the second grating modulation direction after being modulated by the grating structure 5;

[0177]

[0178] in, is the grating modulation amount of any point within the FOV of the grating structure 5;

[0179] is the grating modulation amount of the coupled-in grating 2;

[0180] is the grating modulation amount of the turning grating 4;

[0181] is the grating modulation amount of the outcoupling grating 3;

[0182] n2 is the refractive index of the substrate 1;

[0183] is the first grating modulation direction;

[0184] is the second grating modulation direction.

[0185] In a specific example of the present application, the outcoupling grating 3 adopts the grating structure, and when the grating structure 5 satisfies at least one of the following conditions, light rays in all directions or at least part of the directions within the incident FOV range, after being modulated by the grating structure 5, only generate first-order diffraction in the first grating modulation direction;

[0186]

[0187] in, is the grating modulation amount of any point within the FOV of the grating structure 5;

[0188] is the grating modulation amount of the coupled-in grating 2;

[0189] is the grating modulation amount of the turning grating 4;

[0190] is the grating modulation amount of the outcoupling grating 3;

[0191] n2 is the refractive index of the substrate 1;

[0192] is the first grating modulation direction;

[0193] is the second grating modulation direction.

[0194] It should be noted that when any of the conditions in the above six specific examples are not fully met, the diffraction efficiency perpendicular to the second direction (period P3 direction) of the grating structure can also be suppressed by optimization means to achieve the modulation effect of optical efficiency and uniformity. Among them, this method can achieve a lower k4 diffraction efficiency.

[0195] The grating structure 5 of the present application has no limitation on the shape of the repeated grating units 51 therein, and the grating units 51 may be of any shape.

[0196] For example, see Figures 11 to 13 The grating unit 51 can be a polygon with any rotation angle, a curved edge, or a combination and connection of multiple units.

[0197] In some examples of this application, see Figures 14 to 17 , the grating unit 51 is a columnar structure arranged on the surface of the substrate 1, and the line width ratio of the grating unit 51 in the first direction (the direction of the period P2) is DC, 0<DC<1, see Fig. 20 and Fig. 22 .

[0198] See also Figures 14 to 17 In the side view, the shape of the grating unit 51 is not limited, and it can be a vertical column, an inclined column, a column with a cone angle, or a curved column. In addition, these columnar structures can also be rotated around the z axis at any angle φ in the xy plane (see Fig.17 ), providing extremely high design flexibility.

[0199] Regarding the line width ratio DC: this is an important parameter, which determines the ratio of the width of the grating unit 51 in the first direction to the entire period.

[0200] See also Fig. 20 By adjusting the line width ratio DC of the grating unit 51 in the first direction (the direction of the period P2), its diffraction efficiency can be effectively adjusted, see Fig.21 This is because changes in the line width ratio directly affect the way the grating diffracts the light waves, allowing for finer control of light in specific directions.

[0201] According to this example of the present application, the value range of DC is between 0 and 1, so that the multiple grating units 51 can be arranged periodically along two different directions. Fig. 20If DC=1, the grating units 51 in the first direction (the direction of period P2) are connected into strips, and a one-dimensional grating is finally formed.

[0202] In this example of the present application, by precisely controlling the shape of the grating unit 51 and setting the line width ratio in the periodic direction, the efficiency and uniformity of the waveguide can be further improved, which is particularly important for applications requiring high efficiency and uniform light distribution.

[0203] Since the line width ratio of the grating unit 51 in the first direction is adjustable, an asymmetric grating structure can be realized. Fig.25 and Fig.26 This asymmetry is very useful for certain applications (such as when the light intensity needs to be increased or decreased in a specific direction).

[0204] In general, the design of the grating unit 51 in this example of the present application provides fine control over the diffraction efficiency by adjusting the line width ratio DC in the first direction (the direction of period P2), increases the design flexibility, can improve the efficiency and uniformity of the diffraction optical structure, and realize an asymmetric grating structure.

[0205] In some examples of this application, see Fig.19 The grating unit 51 is a hole-shaped structure arranged on the surface of the substrate 1, see Fig. 22 , the line width ratio of the grating unit 51 in the first direction is DC, 0<DC<1.

[0206] Likewise, on the substrate 1 , the grating unit 51 is not limited to a columnar structure, and can be replaced by a two-dimensionally arranged hole structure.

[0207] Specifically, see Fig.18 and Fig.19 , Fig.18 FIG. 4 shows a top view of a columnar grating unit 51. Fig.19 Lieutenant General Fig.18 The columnar grating unit 51 in the embodiment is replaced with a hole-shaped structure corresponding to the cross-sectional shape. The grating unit 51 with a hole-shaped structure further expands the design possibilities. Such design freedom enables the grating unit 51 to meet the needs of various complex optical applications.

[0208] See also Fig.23 , when DC is between 0 and 0.7, the diffraction efficiency of the grating structure 5 basically shows a trend of gradually increasing, and when DC is between 0.7 and 1, the diffraction efficiency of the grating structure 5 slightly decreases.

[0209] In some examples of the present application, the grating unit 51 includes one or more sub-gratings.

[0210] In this example of the present application, see Figure 7 , Figures 11 to 13 , the grating unit 51 is designed to include one or more sub-gratings. This indicates that each grating unit 51 is not limited to a single shape, but can be composed of two or more sub-gratings of different shapes, see Fig.12 .

[0211] In which, by combining sub-gratings of different shapes and sizes, see Fig.12 , a variety of different optical effects can be designed. This makes the grating structure 5 more flexible and changeable in dealing with various application scenarios, and the performance of the grating can be adjusted and optimized according to actual needs.

[0212] When the grating unit 51 includes a plurality of different sub-gratings, since the sub-gratings have their own independent diffraction characteristics, by combining them, the diffraction efficiency of the grating in different directions can also be precisely controlled, which helps to achieve more complex diffraction patterns and meet specific optical requirements.

[0213] In some cases, manufacturing a single large grating unit with a complex shape may face great technical challenges. By decomposing a large grating unit into multiple simple sub-gratings, the manufacturing difficulty can be reduced and the production efficiency and yield rate can be improved.

[0214] Different sub-gratings may have different response characteristics for light of different wavelengths or polarization states. By combining multiple sub-gratings, a grating with good adaptability to a variety of light conditions can be designed, thus broadening the application range of gratings.

[0215] See also Fig.24 , Fig.24 The conventional one-dimensional grating is shown (see Figure 5 The structure shown) provides symmetrical adjustment capability within its field of view FOV.

[0216] The grating structure 5 provided in the embodiment of the present application is intended to further optimize the performance of a conventional one-dimensional grating. This solution can significantly improve the diffraction efficiency within the field of view FOV of the grating structure 5. Fig.25 and Fig.26 The grating structure 5 of the present application provides the ability to finely adjust the asymmetry within the FOV, which can achieve higher waveguide efficiency and uniformity.

[0217] Specifically, compared to conventional one-dimensional grating designs, see Fig.24 , which shows a nearly vertically symmetrical characteristic in the image, and the improved grating structure 5, see Fig.25 and Fig.26, achieving an asymmetric effect up and down, and the diffraction efficiency of the upper right corner area is significantly improved, which appears as a deeper black, indicating that the optical performance of this area has been significantly enhanced.

[0218] According to another embodiment of the present application, an optical display device is provided, wherein the optical display device comprises an image source and the diffractive optical structure as described above.

[0219] The light emitted by the image source can be incident on the coupling-in grating 2 on the diffractive optical structure.

[0220] The image source is, for example, a projection light machine.

[0221] The diffractive optical structure is, for example, a diffractive optical waveguide.

[0222] The optical display device provided in the embodiment of the present application is, for example, an AR smart head-mounted device. Further, the AR smart head-mounted device is, for example, AR smart glasses or an AR smart helmet.

[0223] The specific implementation of the optical 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.

[0224] 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.

[0225] 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: Comprising a substrate (1) and a grating structure (5) arranged on the substrate (1), the grating structure (5) comprising a plurality of grating units (51) periodically arranged in a tiled manner on the surface of the substrate (1) along a first direction and a second direction; The grating structure (5) has a first grating modulation direction and a second grating modulation direction, the first grating modulation direction is perpendicular to the first direction, and the grating modulation amount in the first grating modulation direction is △E, △E=1 / (P3*sin θ ), wherein P3 is the period of the grating structure (5) in the second direction, θ is the angle between the first direction and the second direction; The light incident on the grating structure generates diffraction behavior only in the first grating modulation direction, and does not generate diffraction behavior in the second grating modulation direction; The diffraction optical structure comprises an in-coupling grating (2), an out-coupling grating (3) and a turning grating (4); At least a partial area of ​​at least one of the coupling-in grating (2), the coupling-out grating (3) and the turning grating (4) includes the grating structure (5); The coupling grating (2) adopts the grating structure (5), and when the grating structure (5) satisfies the following conditions, light rays in at least some directions within the incident FOV do not generate diffraction behavior in the second grating modulation direction after being modulated by the grating structure (5); in, is the grating modulation amount at any point within the FOV of the grating structure (5); n2 is the refractive index of the substrate (1); is the second grating modulation direction.

2. The diffractive optical structure according to claim 1, characterized in that: The period of the grating structure (5) in the first direction is P2, and P2<P3.

3. The diffractive optical structure according to claim 2, characterized in that: The angle between the first direction and the second direction θ 0< θ ≤90°.

4. The diffractive optical structure according to claim 1, characterized in that: At least a part of the region of the turning grating (4) is the grating structure (5); or, The coupling-in grating (2) and the turning grating (4) are the grating structure (5); or, The coupling-in grating (2), a partial region of the coupling-out grating (3) and the turning grating (4) constitute the grating structure (5).

5. The diffractive optical structure according to claim 4, characterized in that: The period P2 of the grating structure (5) in the first direction is less than 300 nm, and after the light is diffracted by the grating structure (5), the light only generates first-order diffraction behavior in the first grating modulation direction, and does not generate diffraction behavior in the second grating modulation direction.

6. The diffractive optical structure according to claim 5, characterized in that: The coupling grating (2) adopts the grating structure (5), and when the grating structure (5) satisfies the following conditions, light rays in at least some directions within the incident FOV, after being modulated by the grating structure (5), only generate first-order diffraction in the first grating modulation direction; in, is the grating modulation amount at any point within the FOV of the grating structure (5); n2 is the refractive index of the substrate (1); is the first grating modulation direction; is the second grating modulation direction.

7. The diffractive optical structure according to claim 5, characterized in that: The turning grating (4) or the outcoupling grating (3) adopts the grating structure (5), and when the grating structure (5) satisfies the following conditions, light rays in at least some directions within the incident FOV do not generate diffraction behavior in the second grating modulation direction after being modulated by the grating structure (5); in, is the grating modulation amount at any point within the FOV of the grating structure (5); is the grating modulation amount of the coupling grating (2); n2 is the refractive index of the substrate (1); is the second grating modulation direction.

8. The diffractive optical structure according to claim 5, characterized in that: The turning grating (4) or the outcoupling grating (3) adopts the grating structure (5), and when the grating structure (5) satisfies the following conditions, light rays in at least some directions within the incident FOV, after being modulated by the grating structure (5), only generate first-order diffraction in the first grating modulation direction; in, is the grating modulation amount at any point within the FOV of the grating structure (5); is the grating modulation amount of the coupling grating (2); n2 is the refractive index of the substrate (1); is the first grating modulation direction; is the second grating modulation direction.

9. The diffractive optical structure according to claim 5, characterized in that: The outcoupling grating (3) adopts the grating structure, and when the grating structure (5) satisfies at least one of the following conditions, light rays in at least some directions within the incident FOV do not generate diffraction behavior in the second grating modulation direction after being modulated by the grating structure (5); in, is the grating modulation amount at any point within the FOV of the grating structure (5); is the grating modulation amount of the coupling grating (2); is the grating modulation amount of the turning grating (4); is the grating modulation amount of the outcoupling grating (3); n2 is the refractive index of the substrate (1); is the first grating modulation direction; is the second grating modulation direction.

10. The diffractive optical structure according to claim 5, characterized in that: The outcoupling grating (3) adopts the grating structure, and when the grating structure (5) satisfies at least one of the following conditions, light rays in at least some directions within the incident FOV range, after being modulated by the grating structure (5), only generate first-order diffraction in the first grating modulation direction; in, is the grating modulation amount at any point within the FOV of the grating structure (5); is the grating modulation amount of the coupling grating (2); is the grating modulation amount of the turning grating (4); is the grating modulation amount of the outcoupling grating (3); n2 is the refractive index of the substrate (1); is the first grating modulation direction; is the second grating modulation direction.

11. The diffractive optical structure according to claim 1, characterized in that: The grating unit (51) is a columnar structure arranged on the surface of the substrate (1); the line width of the grating unit (51) in the first direction accounts for DC, 0<DC<1.

12. The diffractive optical structure according to claim 1, characterized in that: The grating unit (51) is a hole-shaped structure arranged on the surface of the substrate (1); the line width ratio of the grating unit (51) in the first direction is DC, 0<DC<1.

13. The diffractive optical structure according to claim 1, characterized in that: The grating unit (51) comprises one or more sub-gratings.

14. The diffractive optical structure according to claim 5, characterized in that: The diffractive optical structure is an optical waveguide device.

15. An optical display device, characterized in that: include: Image source; and A diffractive optical structure as claimed in any one of claims 1 to 14.

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