Coupling structure, diffractive optical structure and optical display device

Abstract

The embodiment of the invention provides a coupling structure, a diffractive optical structure and optical display equipment. The coupling-in structure comprises a substrate and a coupling-in part arranged on the substrate, and the coupling-in part is used for coupling light into the substrate and enabling the light to be transmitted in the substrate in a total reflection manner; wherein the coupling-in part comprises a coupling-in grating, a first film layer and a second film layer which are stacked; the transmittance of the first film layer is greater than 95% in a visible light wave band; the second film layer is a metal coating film layer; the difference between the refractive index n1 coupled into the grating and the refractive index n2 coupled into the first film layer is that n1-n2 is greater than or equal to 0.3; the average coupling efficiency R1 of the coupling grating to light rays is greater than 60%; after light is coupled into the substrate through the coupling-in grating, the average transmittance T0 is smaller than 0.1% when the light passes through the second film layer; when encountering the coupled grating again, the light which is coupled into the substrate and subjected to total reflection can continue to be propagated in the substrate in a total reflection mode, and the average efficiency R0 of total reflection propagation is larger than 50%.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of light diffraction optics technology. More specifically, the embodiments of the present application relate to a coupling structure, a diffraction optical structure and an optical display device. Background Art

[0002] Augmented reality technology is a technology that combines virtual information with the real world. It has gradually shown great application potential in various industries. In the field of AR optical display, the optical waveguide solution is regarded as one of the best optical display solutions. At present, the optical waveguide solutions mainly include geometric waveguide solutions, relief grating waveguide solutions and volume holographic waveguide solutions. Among them, the relief grating waveguide solution has become the most studied technical solution due to its process difficulty and the balance of optical effects.

[0003] However, although the existing surface relief grating waveguide has the advantages of small size and light weight, its optical transmission efficiency is not high, which limits its application scenarios. The working principle of the AR optical waveguide is to couple the light into the waveguide substrate through the coupling-in area, so that the light propagates by total reflection in the waveguide substrate, and then couple the light out from the coupling-out area, so that the human eye can see the virtual image projected by the AR optical machine. Therefore, the propagation efficiency of the AR optical waveguide is essentially determined by the coupling-in efficiency and the coupling-out efficiency. Since the out-coupling area requires pupil expansion, in order to ensure the uniformity of the pupil expansion, the coupling-out efficiency is difficult to significantly improve, so the efficiency of the AR optical waveguide is mainly affected by the coupling-in efficiency. Summary of the invention

[0004] The purpose of this application is to provide a new technical solution for a coupling structure, a diffractive optical structure and an optical display device.

[0005] In a first aspect, the present application provides a coupling structure. The coupling structure comprises a substrate and a coupling portion disposed on the substrate, wherein the coupling portion is used to couple light into the substrate and cause the light to be transmitted by total reflection within the substrate;

[0006] Wherein, the coupling part comprises a coupling grating, a first film layer and a second film layer which are stacked;

[0007] The transmittance of the first film layer in the visible light band is greater than 95%;

[0008] The second film layer is a metal coating layer;

[0009] The difference between the refractive index n1 of the coupling grating and the refractive index n2 of the first film layer is: n1-n2≥0.3;

[0010] The average coupling efficiency R1 of the coupling grating for light is greater than 60%; after the light is coupled into the interior of the substrate through the coupling grating, the average transmittance T0 of the light when passing through the second film layer is less than 0.1%; the light that has been coupled into the interior of the substrate and has undergone total reflection can continue to propagate through total reflection in the substrate when it encounters the coupling grating again, and the average efficiency of total reflection propagation R0 is greater than 50%.

[0011] Optionally, the refractive index n1 of the coupling-in grating is 1.7≤n1≤2.4.

[0012] Optionally, in the thickness direction of the substrate, a ratio of a thickness of the first film layer h2 to a grating depth h1 of the coupling-in grating satisfies: 0.2≤h2 / h1≤1.5.

[0013] Optionally, the thickness of the first film layer is h2, 1nm≤h2≤100nm.

[0014] Optionally, the grating period T of the coupling-in grating is 200nm≤T≤500, and the grating depth h1 of the coupling-in grating is 30nm≤h1≤400nm.

[0015] Optionally, the first film layer is a non-metallic coating layer, and a refractive index n2 of the first film layer is 1.4≤n2≤2.1.

[0016] Optionally, the material of the second film layer includes metal silver or metal aluminum.

[0017] Optionally, the thickness of the second film layer is h3, 60nm≤h3≤5um.

[0018] Optionally, the coupling-in part is a reflective coupling-in part, and the externally projected light is incident from one side of the substrate, and after being reflected by the coupling-in part, enters the substrate for total reflection transmission.

[0019] Optionally, the first film layer is stacked and arranged on a surface of the coupling-in grating facing away from the substrate;

[0020] The second film layer is stacked on the outer side of the first film layer.

[0021] In a second aspect, the present application provides a diffractive optical structure. The diffractive optical structure comprises:

[0022] The coupling structure as described in the first aspect; and

[0023] The outcoupling part is arranged on the substrate, and is used for coupling out the light from the incoupling part.

[0024] In a third aspect, the present application provides an optical display device. The optical display device comprises:

[0025] Optical machinery; and

[0026] The diffractive optical structure as described in the second aspect;

[0027] The optical engine and the coupling-in portion are respectively located on two opposite sides of the substrate.

[0028] The beneficial effects of this application are:

[0029] The embodiment of the present application provides a coupling structure for a diffractive optical structure. By combining the special design of the coupling grating, the first film layer, and the second film layer (metal coating), and rationally designing the refractive index difference between the first film layer and the coupling grating, compared with the traditional coupling structure, the coupling structure of the present application can significantly improve the coupling efficiency of the diffractive optical structure, such as the coupling efficiency at the green light wavelength is increased by 30% to 140%, thereby effectively improving the optical efficiency of the diffractive optical structure. Due to the improvement in the coupling efficiency, more light can be efficiently coupled into the substrate and propagated therein, which is conducive to enhancing the display effect of the diffractive optical structure, making the virtual image brighter and clearer, and improving the user's visual experience. In addition, the coupling structure of the present application adopts a simple stacked structure design, and achieves an efficient coupling effect by controlling the parameters such as the material and refractive index of each film layer.

[0030] Other features and advantages of the present specification will become apparent from the following detailed description of exemplary embodiments of the present specification with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the specification and, together with the description, serve to explain the principles of the specification.

[0032] Figure 1 A schematic diagram of the structure of a diffractive optical structure provided in an embodiment of the present application;

[0033] Figure 2 A comparison diagram of simulation results of the coupling-in part provided in the embodiment of the present application and the coupling-in part in the comparative example;

[0034] Figure 3 Schematic diagram of light coupling into a traditional diffractive waveguide device.

[0035] Description of reference numerals:

[0036] 1. Base;

[0037] 2. coupling part; 21. coupling grating; 22. first film layer; 23. second film layer;

[0038] 3. Coupling part;

[0039] 4. Optical machine. DETAILED DESCRIPTION

[0040] 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.

[0041] 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.

[0042] Techniques and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the techniques and equipment should be considered part of the specification.

[0043] 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.

[0044] 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.

[0045] The coupling structure, diffractive optical structure and optical display device provided in the embodiments of the present application are described in detail below in conjunction with the accompanying drawings.

[0046] According to one embodiment of the present application, a coupling structure is provided. Figure 1 , the coupling-in structure is applied to a diffractive optical structure.

[0047] The coupling structure of the embodiment of the present application, see Figure 1 , comprising a substrate 1 and a coupling part 2 arranged on the substrate 1, the coupling part 2 is used to couple light into the substrate 1; wherein the coupling part 2 comprises a coupling grating 21, a first film layer 22 and a second film layer 23 which are stacked; the first film layer 22 has a transmittance greater than 95% in the visible light band; the second film layer 23 is a metal coating layer; the difference between the refractive index n1 of the coupling grating 21 and the refractive index n2 of the first film layer 22 is: n1-n2≥0.3;

[0048] The average coupling efficiency R1 of the coupling grating 21 for light is greater than 60%; after the light is coupled into the interior of the substrate 1 through the coupling grating 21, the average transmittance T0 when passing through the second film layer 23 is less than 0.1%; the light that has been coupled into the interior of the substrate 1 and has undergone total reflection can continue to propagate through total reflection in the substrate 1 when it encounters the coupling grating 21 again, and the average efficiency of total reflection propagation R0 is greater than 50%.

[0049] The coupling structure provided in the embodiment of the present application is designed for the coupling part of the diffractive optical structure, and the diffractive optical structure is, for example, a diffractive optical waveguide device, which has wide applicability in the field of AR (augmented reality) optical display, and of course can also be used in optical display fields such as VR (virtual reality).

[0050] The coupling structure provided in the embodiment of the present application aims to solve the problem of low coupling efficiency of diffractive optical waveguide devices in the prior art. The coupling structure provided in the embodiment of the present application can significantly improve the coupling efficiency of the diffractive optical structure, thereby improving the overall optical efficiency of the diffractive optical structure.

[0051] See also Figure 1 The coupling structure provided in the embodiment of the present application includes a substrate 1 and a coupling part 2; wherein the substrate 1 is the basis of the entire coupling structure and is used to support the entire architecture.

[0052] For the substrate 1 provided in the present application, the material of the substrate 1 can be any one of glass, resin, lithium niobate, silicon carbide, etc. These materials have good optical properties and stability.

[0053] The coupling part 2 provided in the present application is responsible for coupling light into the interior of the substrate 1, and is a key component for realizing the display of a diffractive optical structure (such as a diffractive optical waveguide device). The coupling part 2 can couple light used for imaging display into the substrate 1 and allow the light to be transmitted by total reflection in the substrate 1.

[0054] The coupling-in part 2 provided in the present application comprises a coupling-in grating 21 . The coupling-in grating 21 is, for example, directly disposed on the substrate 1 , and is one of the core optical components of the coupling-in part 2 .

[0055] The coupling part 2 of the present application includes, in addition to the coupling grating 21 described above, a first film layer 22 and a second film layer 23; wherein the first film layer 22 can be used to adjust the light coupling process. It is worth noting that there is a certain difference in the refractive index n1 of the coupling grating 21 and the refractive index n2 of the first film layer 22, and this design can achieve effective coupling of light.

[0056] In the coupling structure provided in the embodiment of the present application, the refractive index difference (n1-n2) between the coupling grating 21 and the first film layer 22 is a key parameter, which directly affects the coupling efficiency of light from the coupling grating 21 to the first film layer 22.

[0057] The coupling-in part 2 provided in the embodiment of the present application also includes a second film layer 23, and the second film layer 23 is a metal coating layer. The metal coating layer introduced in the present application has good reflective properties, which can effectively prevent the incident light from generating unexpected diffraction or escape in the coupling-in part 2, thereby ensuring efficient conduction of light energy. Therefore, the addition of the second film layer 23 becomes one of the key factors in improving the coupling efficiency, which promotes the efficient coupling of light into the substrate 1. It can be seen that the introduction of the second film layer 23 can further enhance the coupling efficiency and ensure that the light is efficiently coupled into the substrate 1.

[0058] In addition, the second film layer 23, ie, the metal coating layer, can also protect the coupling grating 21 and effectively resist potential damage to the coupling grating 21 by the external environment, thereby facilitating prolonging the service life and stability of the entire coupling structure.

[0059] In the coupling structure of the present application, the refractive index difference (n1-n2) between the coupling grating 21 and the first film layer 22 is also a key parameter, which directly affects the coupling efficiency of light from the coupling grating 21 to the first film layer 22. In the present application, the refractive index of the coupling grating 21 is greater than the refractive index of the first film layer 22, and the difference in refractive index between the two is greater than 0.3.

[0060] More preferably, the difference in refractive index between the two is greater than 0.4.

[0061] If the refractive index difference between the coupling-in grating 21 and the first film layer 22 is less than 0.3, the following disadvantages may occur:

[0062] (1) The coupling efficiency will be relatively low:

[0063] If the refractive index difference (n1-n2) is small, such as less than 0.3, this means that when the light transitions from the coupling grating 21 to the first film layer 22, the direction change will not be significant enough, so that part of the light cannot be effectively coupled into the substrate 1. This will lead to a decrease in coupling efficiency, thereby affecting the optical performance of the diffractive optical structure.

[0064] (2) Unstable optical performance:

[0065] Smaller refractive index differences, such as less than 0.3, may increase the sensitivity of the diffractive optical structure to the incident angle of the light. When the incident angle of the light changes slightly, the coupling efficiency may fluctuate significantly, resulting in unstable optical performance.

[0066] In the present application, the refractive index difference (n1-n2) between the coupling grating 21 and the first film layer 22 is controlled to be greater than or equal to 0.3, which can well improve the coupling efficiency. This is because: when the light is incident from the coupling grating 21, the greater the refractive index difference, the more significant the change in direction of the light when entering the first film layer 22. This significant change in direction helps the light to be more effectively coupled into the substrate 1, reducing the reflection and scattering losses of the light, thereby improving the coupling efficiency.

[0067] In addition, the larger refractive index difference increases the tolerance of the coupling structure to the incident angle of light. Even if the incident angle of light changes slightly, the coupling efficiency can remain relatively stable, which has good adaptability to changes in the incident angle of light in practical applications.

[0068] In summary, it is very reasonable to control the refractive index difference to be greater than or equal to 0.3 in the present application. This choice helps to improve the coupling efficiency and enhance the stability of optical performance.

[0069] Regarding the design of the first film layer 22, it has a high transmittance characteristic in the visible light band, that is, the transmittance is greater than 95%. This design brings the following significant technical effects:

[0070] (1) Improving light utilization: The high transmittance of the first film layer 22 in the visible light band means that most of the incident light can pass through the first film layer 22 without hindrance, and then effectively interact with the coupling grating 21. This significantly improves the utilization of light, so that more light can be effectively coupled into the substrate 1 for total reflection propagation.

[0071] (2) Optimizing visual effects: Since light in the visible light band is the main component of human visual perception, the high transmittance of the first film layer 22 helps to ensure that the virtual image presented by the diffractive optical structure of the coupling structure of the present application has clear visual effects and bright colors. This is crucial to improving the user's viewing experience.

[0072] The present application not only improves the light utilization and visual effect, but also enhances the reliability and stability of the entire coupling structure by designing the first film layer 22 with high transmittance.

[0073] The coupling-in structure provided in the embodiment of the present application can significantly improve the coupling-in efficiency of the diffractive optical structure.

[0074] The coupling structure provided in the embodiment of the present application also satisfies the following relationship:

[0075] The average coupling efficiency R1 of the coupling grating 21 for light is greater than 60%; after the light is coupled into the interior of the substrate 1 through the coupling grating 21, the average transmittance T0 when passing through the second film layer 23 is less than 0.1%; the light that has been coupled into the interior of the substrate 1 and has undergone total reflection can continue to propagate through total reflection in the substrate 1 when it encounters the coupling grating 21 again, and the average efficiency of total reflection propagation R0 is greater than 50%.

[0076] See also Figure 3 , the average coupling efficiency R1 of the coupling grating 21 for light is greater than 60%. This parameter represents the efficiency of light being coupled into the interior of the substrate 1 through the coupling grating 21. The average coupling efficiency R1 represents the reflection order of the total reflection propagation range of the incident light being initially diffracted into the interior of the substrate 1, i.e., the first-order reflection. Coupling efficiency is one of the key indicators for measuring the performance of a diffractive optical structure. A higher coupling efficiency means that more light can be effectively guided into the diffractive optical structure, thereby improving the optical efficiency of the entire diffractive optical structure.

[0077] See also Figure 3 , after the incident light is coupled into the interior of the substrate 1 through the coupling grating 21, the average transmittance T0 when passing through the second film layer 23 is less than 0.1%. This parameter represents the transmittance of the light after it enters the substrate 1 through the coupling grating 21 and then passes through the second film layer 23 (metal coating layer). The average transmittance T0 represents the transmission efficiency of the light in this process. Since this is an undesirable light loss, it is expressed as a lower percentage. In the present application, the transmittance of the second film layer 23 has a direct impact on the loss of light. A lower transmittance means that the coupling structure can maintain a higher optical efficiency.

[0078] Please continue to see Figure 3 , the light that has been coupled into the interior of the substrate 1 and has undergone total reflection can continue to propagate by total reflection in the substrate 1 when it encounters the coupling-in grating 21 again, and the average efficiency of total reflection propagation R0>50%. This parameter indicates that after the light is totally reflected inside the substrate 1, when it encounters the coupling-in grating 21 again, it can continue to maintain the efficiency of total reflection propagation. R0 represents the efficiency of the light that undergoes zero-order reflection when it encounters the coupling-in grating 21 again and continues to propagate in the waveguide. The efficiency of total reflection propagation is an important indicator to measure the stability and durability of the diffractive optical structure. A higher total reflection propagation efficiency means that the light can propagate more stably inside the substrate, reducing losses and interference.

[0079] The above three parameters together reflect the optical performance and stability of the coupling structure of the present application. By optimizing these parameters, the optical efficiency and use effect of the entire coupling structure can be improved.

[0080] The embodiment of the present application provides a coupling structure for a diffractive optical structure. By combining the special design of the coupling grating 21, the first film layer 22, and the second film layer 23 (metal coating), and rationally designing the refractive index difference between the first film layer 22 and the coupling grating 21, compared with the traditional coupling structure, the coupling structure of the present application can significantly improve the coupling efficiency of the diffractive optical structure, such as the coupling efficiency at the green light wavelength is increased by 30% to 140%, thereby effectively improving the optical efficiency of the diffractive optical structure. Due to the improvement in the coupling efficiency, more light can be efficiently coupled into the substrate 1 and propagated therein, which is conducive to enhancing the display effect of the diffractive optical structure, making the virtual image brighter and clearer, and improving the user's visual experience. In addition, the coupling structure of the present application adopts a simple stacked structure design, and achieves an efficient coupling effect by controlling the parameters such as the material and refractive index of each film layer.

[0081] In some examples of the present application, the refractive index n1 of the coupling-in grating 21 is 1.7≤n1≤2.4.

[0082] In this example of the present application, it is described that the refractive index n1 of the coupling grating 21 is in the range of 1.7 to 2.4. Based on the aforementioned fact that the refractive index of the coupling grating 21 is greater than the refractive index of the first film layer 22, and the difference between the refractive indices of the two is greater than 0.3, this design choice in this example of the present application is not arbitrary, and the following is an analysis of the refractive index range selection of the coupling grating 21 and its technical effect.

[0083] Based on the refractive index difference range between the coupling grating 21 and the first film layer 22. By setting the refractive index of the coupling grating 21 within the range of this example of the present application, the diversity and availability of the materials used for the first film layer 22 can be ensured, providing convenience for production.

[0084] In some examples of the present application, in the thickness direction of the substrate 1 , the ratio of the thickness h2 of the first film layer 22 to the grating depth h1 of the coupling-in grating 21 satisfies: 0.2≤h2 / h1≤1.5.

[0085] By adjusting the ratio of the thickness h2 of the first film layer 22 to the grating depth h1 of the coupling grating 21, the diffraction behavior of light during the coupling process can be more effectively controlled. This helps to ensure that more light can be coupled into the substrate 1 for total reflection propagation as expected, thereby improving the coupling efficiency.

[0086] The appropriate thickness design of the first film layer 22 not only helps to improve the optical performance, but also provides better physical protection for the coupling grating 21 and enhances its structural stability. This helps to resist the negative impact of external environmental factors (such as temperature changes, mechanical stress, etc.) on the coupling grating 21 and prolong the service life of the entire coupling structure.

[0087] In this example of the present application, setting the thickness ratio range of the first film layer 22 and the coupling grating 21′ can provide more guidance for the manufacturing process of the coupling structure provided in the embodiment of the present application. This helps to ensure that each coupling structure produced can achieve the expected optical performance and improves the accuracy and repeatability of manufacturing.

[0088] In this example of the present application, by controlling the thickness dimension relationship between the first film layer 22 and the coupling grating 21, the coupling efficiency can be effectively improved, while the structural stability and manufacturing accuracy of the coupling structure are enhanced.

[0089] In some examples of the present application, the thickness of the first film layer 22 is h2, 1nm≤h2≤100nm.

[0090] In the range of 1 nm to 100 nm, the thickness of the first film layer 22 can appropriately affect the coupling process of light from the coupling-in grating 21 into the substrate 1 .

[0091] The thickness design of the first film layer 22 provided in this example of the present application helps to reduce reflection and scattering, allowing light to be more effectively guided into the substrate 1, thereby improving the coupling efficiency. The improvement in coupling efficiency directly leads to an improvement in image quality. Therefore, within the range of 1nm to 100nm, the thickness of the first film layer 22 can ensure the brightness and clarity of the virtual image. In addition, the thickness range of the first film layer 22 in this example of the present application will not increase the size of the entire coupling structure in the thickness direction too much.

[0092] If the thickness of the first film layer 22 is less than 1 nm, it may not provide sufficient physical strength and optical properties to support effective light coupling. In addition, a first film layer 22 that is too thin may be difficult to accurately control during the manufacturing process, resulting in unstable performance. In terms of optics, a first film layer 22 that is too thin may not produce sufficient phase delay to guide light into the waveguide, resulting in a significant reduction in coupling efficiency.

[0093] When the thickness of the first film layer 22 exceeds 100 nm, excessive absorption and scattering losses may be introduced, resulting in excessive attenuation of light during the coupling process. This will also reduce the coupling efficiency and affect the brightness and clarity of the AR image. In addition, an overly thick first film layer 22 may increase manufacturing costs and complexity because it requires longer coating time and more materials.

[0094] In some examples of the present application, the grating period T of the coupling-in grating 21 is 200nm≤T≤500nm, and the grating depth h1 of the coupling-in grating 21 is 30nm≤h1≤400nm.

[0095] In the coupling structure provided in the embodiment of the present application, the period of the coupling grating 21 is one of the key factors affecting the diffraction efficiency of light. In the range of 200nm to 500nm, the grating period of the coupling grating 21 can form a good match with the wavelength of the incident light, so that the light is effectively diffracted when passing through the coupling grating 21, and then efficiently coupled into the substrate 1.

[0096] The selection of the period range of the coupling grating 21 provided in this example of the present application also helps to broaden the spectral response range of the coupling structure. Light of different wavelengths can be diffracted to different degrees when passing through a coupling grating with an appropriate period, thereby achieving effective coupling in a wide spectral range.

[0097] By optimizing the grating period, the coupling efficiency can be improved, thereby enhancing the brightness and clarity of the AR image. This helps to improve the user's visual experience, especially in application scenarios with complex lighting conditions or requiring high-definition display.

[0098] The depth of the coupling grating 21 is an important factor affecting the ratio of light diffraction and reflection. In the range of 30nm to 400nm, the grating depth can properly balance diffraction and reflection, so that more light can be effectively coupled into the substrate 1.

[0099] In the present application, the coupling-in grating 21 is, for example, a one-dimensional grating.

[0100] One-dimensional gratings have the advantages of simple structure and easy manufacturing, and have efficient diffraction ability in a specific direction. By optimizing the period and depth of the one-dimensional grating, its one-dimensional diffraction characteristics can be further enhanced, thereby achieving more efficient light coupling.

[0101] In some examples of the present application, the first film layer 22 is a non-metallic coating layer, and the refractive index n2 of the first film layer 22 is 1.4≤n2≤2.1.

[0102] In this example of the present application, the first film layer 22 is a non-metallic coating layer. When its thickness is in the range of 1nm-100nm, the coating process of the first film layer 22 is relatively easy to control, which can ensure that the produced coupling structure has consistent performance.

[0103] In this example of the present application, the refractive index range of the first film layer 22 is designed. Within the refractive index range provided in this example, it can form a reasonable refractive index difference with the coupling grating 21, so that the coupling process of light between the coupling grating 21 and the first film layer 22 is optimized. Light can be more effectively guided into the substrate 1, reducing reflection and scattering losses, thereby improving coupling efficiency. The improvement in coupling efficiency directly leads to an improvement in image quality. This is because more light is effectively coupled into the substrate 1, making the virtual image brighter and clearer, and the user's visual experience is significantly improved.

[0104] Due to the improved coupling efficiency, the coupling structure provided in the embodiment of the present application can be applied to more application scenarios with complex light conditions. For example, it can provide a stable image display effect in outdoor strong light or indoor weak light environment.

[0105] In some examples of the present application, the material of the second film layer 23 includes metal silver or metal aluminum.

[0106] In this example of the present application, the material of the second film layer 23 is selected from metal silver or metal aluminum. Metal silver and metal aluminum have good reflective properties and can effectively reflect light from the coupling grating 21 back to the substrate 1, thereby reducing light loss and improving coupling efficiency. This helps to enhance the brightness and clarity of the AR image and improve the user's visual experience.

[0107] The metal material has high hardness and wear resistance, and can resist erosion and wear from the external environment, which enables the second film layer 23 to maintain stable performance during long-term use, thereby extending the service life of the diffractive optical structure.

[0108] In addition, metallic silver and metallic aluminum are both good conductors, which helps to achieve functions such as electromagnetic shielding and electrostatic protection in diffractive optical structures or AR optical display devices.

[0109] Silver and aluminum have good compatibility with a variety of materials and are easy to integrate with other film layers or structures. At the same time, these metal materials are also easy to process through physical vapor deposition (PVD), chemical vapor deposition (CVD) and other processes, which is conducive to large-scale production.

[0110] In some examples of the present application, the thickness of the second film layer 23 is h3, 60nm≤h3≤5um.

[0111] In the coupling structure provided in the present application, the second film layer 23 is used as a reflective layer, and its thickness directly affects the reflection efficiency of light. In the range of 60nm to 5um proposed in this example of the present application, the metal coating layer such as silver or aluminum can form a continuous and uniform film, thereby effectively reflecting light back to the substrate 1, reducing light loss and improving coupling efficiency.

[0112] In AR applications, the displayed image may contain light of multiple wavelengths. Within the thickness range of 60nm to 5μm, the metal coating layer (second film layer 23) can maintain relatively stable reflective performance for light of different wavelengths, thereby ensuring the color reproduction and clarity of the displayed image.

[0113] In the thickness range of 60nm to 5um, the second film layer 23 can be processed by a variety of thin film deposition techniques (such as physical vapor deposition, chemical vapor deposition, etc.) These techniques have high precision, high stability and high repeatability, and can ensure the uniformity and consistency of the metal coating thickness.

[0114] A sufficient thickness of the second film layer 23 can provide better structural support and enhance the overall stability and durability of the coupling structure, which helps to resist the influence of external environmental factors (such as temperature, humidity, etc.) on the film performance and prolong the service life of the diffractive optical structure.

[0115] It should be noted that the thickness of the second film layer 23 is directly related to the material consumption. An overly thick second film layer 23 will increase the material cost, especially when a precious metal (such as silver) is used as the film material. The deposition process of the film layer requires a certain amount of time and energy consumption. An overly thick second film layer 23 means a longer processing time and a higher energy cost. For diffractive optical structures, lightweighting and miniaturization are important development trends. An overly thick second film layer 23 will obviously increase the weight and volume of the equipment.

[0116] In some examples of the present application, the coupling-in portion 2 is a reflective coupling-in portion, and the externally projected light is incident from one side of the substrate 1, and after being reflected by the coupling-in portion 2, enters the substrate 1 for total reflection transmission.

[0117] In this example of the present application, a coupling structure for a diffractive optical structure is proposed, wherein the coupling part 2 is designed as a reflective coupling part. This design allows the externally projected light to be incident from one side of the substrate 1, and after being reflected by the coupling part 2, enter the interior of the substrate 1 for total reflection transmission. The design of the reflective coupling part in the present application can effectively reflect most of the incident light into the interior of the substrate 1, reducing the direct transmission or scattering loss of the light. This helps to improve the utilization rate of light, allowing more light to participate in the subsequent display process, thereby enhancing the brightness and contrast of the image.

[0118] In some examples of the present application, the coupling grating 21 includes a rectangular grating, a blazed grating, a trapezoidal grating or a step grating. A notable feature of the coupling structure provided by the present application is that it is suitable for a variety of grating types. The adaptability of a variety of grating types enables the coupling structure of the present application to flexibly respond to different application requirements. For example, in a scenario requiring high diffraction efficiency, a blazed grating or a step grating can be selected; and in a scenario with high requirements for manufacturing difficulty, a rectangular grating or a trapezoidal grating can be selected.

[0119] In some examples of this application, see Figure 1 The first film layer 22 is stacked on a surface of the coupling-in grating 21 facing away from the substrate 1 ; the second film layer 23 is stacked on the outer side of the first film layer 22 .

[0120] According to the description in this example of the present application, the first film layer 22 is stacked on the coupling grating 21, and the second film layer 23 is stacked on the outer side of the first film layer 22, that is, the side away from the substrate 1 and the coupling grating 21. Such a setting forms a multi-level coupling structure, and each layer has a specific function.

[0121] The coupling grating 21 is a key component for light to enter the substrate 1. The coupling grating 21 achieves effective diffraction and coupling of incident light through the design of its optical parameters such as periodicity and depth. The optimization of its material refractive index and structural parameters ensures that light can enter the substrate 1 with high efficiency.

[0122] The first film layer 22: Its main function is to further enhance the coupling efficiency and optimize the propagation of light in the substrate 1. By selecting appropriate materials (such as materials with a refractive index range of 1.4-2.1) and coating methods, the first film layer 22 can improve the transmittance of light and reduce the loss of light.

[0123] The second film layer 23: It is a metal coating layer (such as metal silver or metal aluminum), which mainly plays a reflective and protective role. It can effectively reflect the uncoupled light back to the substrate 1, further improving the utilization rate of the light. At the same time, the metal coating layer can also protect the first film layer 22 and the coupling grating 21 from damage by the external environment.

[0124] The coupling structure design in this example of the present application can significantly improve the light coupling efficiency through the synergistic effect of the coupling grating 21 and the first film layer 22. This design not only optimizes the diffraction and coupling process of light, but also reduces the loss and scattering of light.

[0125] The arrangement of the first film layer 22 and the second film layer 23, especially the reflection effect of the second film layer 23, can ensure the stable propagation of light in the substrate 1. This helps to reduce the fluctuation and attenuation of light during propagation and improve the stability and clarity of the displayed image.

[0126] The coupling architecture in this example of the present application achieves precise control of the light propagation path by optimizing the structure and material parameters of each layer, which not only improves the coupling efficiency, but also optimizes the propagation characteristics of the light in the substrate 1, thereby improving the overall performance of the diffraction optical waveguide device.

[0127] In some examples of the present application, the substrate 1 is any one of glass, resin, lithium niobate and silicon carbide.

[0128] Glass materials have good transparency and optical properties, high stability, and can withstand certain temperature changes. They are suitable for optical devices that require high transparency and optical properties.

[0129] The characteristics of resin materials are low cost, easy processing and light weight. They are suitable for occasions with strict requirements on weight and production cost.

[0130] Lithium niobate has excellent electro-optical effect and is suitable for optical devices that require high-speed electro-optical modulation.

[0131] Silicon carbide has high hardness, wear resistance, good thermal conductivity and electrical conductivity. It is suitable for optical devices with high requirements for durability and thermal stability.

[0132] Different substrate materials have different effects on the transmission and diffraction of light. According to actual needs, choosing the right substrate material can optimize the transmission efficiency of light, reduce light loss, and improve the overall optical performance of optical devices such as diffractive optical structures.

[0133] The design of the coupling structure of the present application achieves precise control of the light propagation path by optimizing the refractive index, period, depth and other parameters of the coupling grating 21, and reasonably configuring the first film layer 22 and the second film layer 23, thereby achieving the purpose of improving the coupling efficiency. This design idea and technical solution provide new ideas and methods for the development of diffractive optical structure technology.

[0134] See also Figure 2 , the performance of the coupling structure for the diffractive optical structure proposed in the embodiment of the present application is verified through simulation experiments. This section describes in detail the coupling efficiency of the four coupling structures for green light in the visible light, and conducts a comparative analysis, as follows:

[0135] 1. Simulation experiment settings:

[0136] Experimental purpose: To verify the improvement of green light coupling efficiency of the coupling structure proposed in this application (defined as coupling structure 1 in the experiment) compared with other comparative coupling structures.

[0137] Experimental architecture:

[0138] The coupling structure 1 includes a coupling grating 21 , a first film layer 22 disposed on the coupling grating 21 , and a second film layer 23 disposed on the first film layer 22 , that is, the coupling structure of the present application.

[0139] The coupling structure 2 includes a coupling grating 21 and a second film layer 23 disposed on the coupling grating 21 , ie, the comparison structure 1.

[0140] The coupling structure three includes a coupling grating 21 and a first film layer 22 disposed on the coupling grating 21 , ie, the comparison structure two.

[0141] Coupling structure four: only has coupling grating 21, ie, compared with structure three.

[0142] Experimental conditions: Use green light as the test light source, and simulate the light transmission and diffraction process under different coupling structures.

[0143] Second, the simulation results show:

[0144] Coupling efficiency:

[0145] Coupling structure 1 (coupling structure of the present application): the coupling efficiency of green light is 20.6%.

[0146] Coupling structure 2 (compared with structure 1): the coupling efficiency of green light is 15.8%.

[0147] Coupling structure three (compared with structure two): the coupling efficiency of green light is 8.6%.

[0148] Coupling structure 4 (comparative structure 3): the coupling efficiency of green light is 11%.

[0149] 3. Comparative analysis:

[0150] Efficiency improvement:

[0151] Compared with the coupling structure 2, the green light coupling efficiency of the coupling structure 1 is improved by (20.6%-15.8%) / 15.8%≈30%.

[0152] Compared with the coupling structure 3, the green light coupling efficiency of the coupling structure 1 is improved by (20.6%-8.6%) / 8.6%≈140%.

[0153] Compared with the coupling structure 4, the green light coupling efficiency of the coupling structure 1 is improved by (20.6%-11%) / 11%≈87%.

[0154] In summary, the coupling structure (coupling structure 1) provided in the embodiment of the present application significantly improves the coupling efficiency of green light by introducing the first film layer 22 and the second film layer 23. Compared with other comparative structures, the coupling structure provided in the present application has obvious advantages in optical efficiency, which is conducive to improving the overall performance of the AR diffractive optical structure.

[0155] In summary, the simulation experiment verifies that the coupling structure proposed in this application has a significant improvement in green light coupling efficiency compared to other comparative structures. This result shows that the coupling structure of this application can significantly improve the coupling efficiency of diffractive optical structures (such as diffractive optical waveguide devices), thereby improving the optical efficiency of the waveguide, providing strong technical support for the application and development of AR technology.

[0156] It should be noted that the coupling structure proposed in the present application has significantly improved red light coupling efficiency and blue light coupling efficiency compared to other comparative structures, and will not be described again here.

[0157] According to another embodiment of the present application, a diffractive optical structure is provided. Figure 1 The diffractive optical structure includes: the coupling-in structure and the coupling-out part 3 as described above, wherein the coupling-out part 3 is arranged on the substrate 1, and the coupling-out part 3 couples out the light from the coupling-in part 2.

[0158] The diffraction optical structure of the present application mainly consists of two parts: a coupling-in structure and a coupling-out part 3. The coupling-in structure part has been described above, including a substrate 1, a coupling-in grating 21, a first film layer 22 and a second film layer 23. The coupling-in part 2 is used to efficiently couple light into the substrate 1 for total reflection transmission. The coupling-out part 3 is arranged on the substrate 1, and its main function is to couple out the light from the coupling-in part 2 so that the human eye can see the virtual image projected by the optical machine 4.

[0159] The outcoupling part 3 may be an outcoupling grating, which may be a one-dimensional grating, a two-dimensional grating, etc. A one-dimensional grating has a simple structure and a low manufacturing cost, while a two-dimensional grating may provide a more complex diffraction effect in certain application scenarios.

[0160] According to another embodiment of the present application, an optical display device is provided, which includes an optical engine 4 and the diffractive optical structure as described above; the optical engine 4 and the coupling-in portion 2 are respectively located on two opposite sides of the substrate 1.

[0161] The optical engine 4 is one of the core components of the optical display device, and is responsible for generating and projecting the light required for the virtual image. In the embodiment of the present application, the optical engine 4 is arranged on one side of the substrate 1, opposite to the coupling part 2. In this way, the light emitted by the optical engine 4 can be directly irradiated onto the coupling part 2, achieving efficient light coupling.

[0162] The diffractive optical structure: As mentioned above, the diffractive optical structure includes a coupling structure and a coupling part 3. The coupling structure is responsible for efficiently coupling the light emitted by the optical machine 4 into the substrate 1, while the coupling part 3 is responsible for coupling the light out of the substrate 1 to form a virtual image visible to the human eye. These two parts work together to achieve efficient transmission and display of light.

[0163] The optical display device provided by the embodiment of the present application has a wide range of application prospects. For example, in the field of augmented reality (AR), it can be used as one of the core components of AR glasses or helmets to provide users with a more realistic and immersive virtual experience. In addition, in the fields of virtual reality (VR), mixed reality (MR), etc., the optical display device also has potential application value.

[0164] The specific implementation of the optical display device of the embodiment of the present application can refer to the various embodiments of the coupling structure and the diffraction optical structure mentioned above, so it at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be repeated here one by one.

[0165] 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.

[0166] 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 coupling structure, characterized in that: It comprises a substrate (1) and a coupling-in portion (2) arranged on the substrate (1), wherein the coupling-in portion (2) is used to couple light into the substrate (1) and to cause the light to be transmitted by total reflection within the substrate (1); Wherein, the coupling part (2) comprises a coupling grating (21), a first film layer (22) and a second film layer (23) which are stacked; The transmittance of the first film layer (22) in the visible light band is greater than 95%; The second film layer (23) is a metal coating layer; The difference between the refractive index n1 of the coupling grating (21) and the refractive index n2 of the first film layer (22) is: n1-n2≥0.3; The average coupling efficiency R1 of the coupling grating (21) for light is greater than 60%; after the light is coupled into the interior of the substrate (1) through the coupling grating (21), the average transmittance T0 when passing through the second film layer (23) is less than 0.1%; when the light that has been coupled into the interior of the substrate (1) and has undergone total reflection encounters the coupling grating (21) again, it can continue to propagate by total reflection in the substrate (1), and the average efficiency R0 of total reflection propagation is greater than 50%.

2. The coupling structure according to claim 1, characterized in that: The refractive index n1 of the coupling-in grating (21) is 1.7≤n1≤2.

4.

3. The coupling structure according to claim 1, characterized in that: In the thickness direction of the substrate (1), the ratio of the thickness h2 of the first film layer (22) to the grating depth h1 of the coupling grating (21) satisfies: 0.2≤h2 / h1≤1.

5.

4. The coupling structure according to claim 3, characterized in that: The thickness of the first film layer (22) is h2, 1nm≤h2≤100nm.

5. The coupling structure according to claim 3, characterized in that: The grating period T of the coupling grating (21) is 200nm≤T≤500nm, and the grating depth h1 of the coupling grating (21) is 30nm≤h1≤400nm.

6. The coupling structure according to claim 1, characterized in that: The first film layer (22) is a non-metallic coating layer, and the refractive index n2 of the first film layer (22) is 1.4≤n2≤2.

1.

7. The coupling structure according to claim 1, characterized in that: The material of the second film layer (23) includes metal silver or metal aluminum.

8. The coupling structure according to claim 7, characterized in that: The thickness of the second film layer (23) is h3, 60nm≤h3≤5um.

9. The coupling structure according to claim 1, characterized in that: The coupling-in part (2) is a reflective coupling-in part, and the externally projected light is incident from one side of the substrate (1), and after being reflected by the coupling-in part (2), enters the substrate (1) and is transmitted by total reflection.

10. The coupling structure according to claim 1, characterized in that: The first film layer (22) is stacked and arranged on a surface of the coupling-in grating (21) on a side facing away from the substrate (1); The second film layer (23) is stacked on the outer side of the first film layer (22).

11. A diffractive optical structure, characterized in that: include: The coupling structure according to any one of claims 1 to 10; and The outcoupling part (3) is arranged on the substrate (1), and the outcoupling part (3) is used to couple out the light from the coupling part (2).

12. An optical display device, characterized in that: include: Optical machinery (4); and The diffractive optical structure according to claim 11; The optical engine (4) and the coupling-in portion (2) are respectively located on two opposite sides of the substrate (1).

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