Incoupling structure, diffractive optical structure and optical display device

Abstract

Embodiments of the present application provide a coupling structure, a diffractive optical structure, and an optical display device. The coupling structure includes a substrate and a coupling portion disposed on the substrate, the coupling portion being configured to couple light into the substrate and cause the light to propagate by total reflection within the substrate. The coupling portion includes a stacked coupling grating, a first film layer, and a second film layer. The first film layer has a transmittance greater than 95% in the visible light band. The second film layer is a metal-plated film layer. 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. The average coupling efficiency R1 of the coupling grating for light is greater than 60%. After 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%. Light that has been coupled into the interior of the substrate and is totally reflected can continue to propagate by total reflection within the substrate when it encounters the coupling grating again, and the average efficiency of total reflection propagation R0 is greater 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 (AR) technology, which combines virtual information with the real world, is increasingly showing enormous potential for application across various industries. In the field of AR optical displays, optical waveguides are considered one of the best optical display solutions. Currently, optical waveguide solutions primarily include geometric waveguides, relief grating waveguides, and volume holographic waveguides. Among these, relief grating waveguides have become the most researched technology due to their balance between process difficulty and optical performance.

[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: the light is coupled into the waveguide substrate through the coupling-in area, so that the light is fully reflected and propagated in the waveguide substrate, and then the light is coupled 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 outcoupling area requires pupil expansion, in order to ensure the uniformity of the pupil expansion, the coupling-out efficiency is difficult to significantly improve. Therefore, 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 includes a substrate and a coupling portion disposed on the substrate, wherein the coupling portion is configured to couple light into the substrate and cause the light to be transmitted by total reflection within the substrate;

[0006] Wherein, the coupling part includes 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-in 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 when passing through the second film layer is less than 0.1%; when the light that has been coupled into the interior of the substrate and has undergone total reflection encounters the coupling grating again, it can continue to propagate through total reflection in the substrate, and the average efficiency R0 of total reflection propagation 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 h2 of the first film layer 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 200 nm ≤ T ≤ 500, and the grating depth h1 of the coupling-in grating is 30 nm ≤ h1 ≤ 400 nm.

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

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

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

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

[0019] Optionally, the first film layer is stacked 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 includes:

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

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

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

[0025] optical machinery; and

[0026] The diffractive optical structure according to the second aspect;

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

[0028] The beneficial effects of this application are:

[0029] The embodiments of the present application provide a coupling structure for a diffractive optical structure. By combining the special design of a coupling grating, a first film layer, and a second film layer (metal coating), and rationally designing the refractive index difference between the first film layer and the coupling grating, the coupling structure of the present application can significantly improve the coupling efficiency of the diffractive optical structure compared to traditional coupling structures. For example, 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 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 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 this specification, illustrate embodiments of the specification and, together with the description, serve to explain the principles of the specification.

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

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

[0034] Figure 3 Schematic diagram of light coupling into a traditional diffraction 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 arrangements 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 disclosure, 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 like 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, diffraction optical structure and optical display device provided in the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0046] According to one embodiment of the present application, a coupling structure is provided, see 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 portion 2 disposed on the substrate 1, the coupling portion 2 being used to couple light into the substrate 1; wherein the coupling portion 2 comprises a stacked coupling grating 21, a first film layer 22, and a second film layer 23; 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%; 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 through total reflection in the substrate 1, and the average efficiency R0 of total reflection propagation 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 embodiments of the present application aims to address the low coupling efficiency problem of existing technologies, such as diffractive optical waveguide devices. The coupling structure provided in the embodiments 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 foundation 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 element 2 provided herein is responsible for coupling light into the interior of the substrate 1 and is a key component for realizing displays using diffractive optical structures (such as diffractive optical waveguide devices). The coupling element 2 can couple light used for imaging and display into the substrate 1, allowing the light to be transmitted through total internal reflection within the substrate 1.

[0054] The coupling-in part 2 provided in the present application includes 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] In addition to the aforementioned coupling grating 21, the coupling element 2 of the present application also includes a first film layer 22 and a second film layer 23. The first film layer 22 can be used to regulate the light coupling process. It is worth noting that the refractive index n1 of the coupling grating 21 and the refractive index n2 of the first film layer 22 are designed to differ slightly, which enables effective light coupling.

[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 portion 2 provided in the embodiment of the present application further includes a second film layer 23, which 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 unintended diffraction or escaping within the coupling portion 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 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 from the external environment, thereby helping to extend 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 between the two refractive indices 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 the direction of light will not change significantly when it transitions from the coupling grating 21 to the first film layer 22, resulting in some light not being 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, can increase the sensitivity of diffractive optical structures to the incident angle of light. When the incident angle of light changes slightly, the coupling efficiency may fluctuate significantly, leading to unstable optical performance.

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

[0067] Furthermore, the larger refractive index difference increases the coupling structure's tolerance to light incident angles. Even with slight changes in the light incident angle, the coupling efficiency remains relatively stable, which provides better adaptability to changes in light incident angles 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] The design of the first film layer 22 has a high transmittance in the visible light band, i.e., a transmittance greater than 95%. This design brings the following significant technical effects:

[0070] (1) Improved light utilization: The high transmittance of the first film layer 22 in the visible light band means that most incident light can pass through the first film layer 22 unimpeded, and then effectively interact with the coupling grating 21. This significantly improves the light utilization, allowing more light to be effectively coupled into the substrate 1 for total internal reflection propagation.

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

[0072] The present application designs the first film layer 22 with high transmittance, thereby not only improving the light utilization and visual effect, but also enhancing the reliability and stability of the entire coupling structure.

[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%; 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 through total reflection in the substrate 1, and the average efficiency R0 of total reflection propagation 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 coupling into the interior of the substrate 1 through the coupling grating 21. The average coupling efficiency R1 represents the reflection order of the total internal reflection propagation range of the incident light after being initially diffracted into the interior of the substrate 1, i.e., 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 passing through the coupling grating 21 and entering the substrate 1, and then passing 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 is greater than 50%. This parameter indicates that after the light has undergone total reflection 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 for measuring the stability and durability of diffraction optical structures. 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, the coupling structure of the present application can significantly improve the coupling efficiency of the diffractive optical structure compared to the traditional coupling structure. For example, 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 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 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, the refractive index n1 of the coupling-in grating 21 is described as being within the range of 1.7 to 2.4. Given that the refractive index of the coupling-in grating 21 is greater than that of the first film layer 22, and the difference between the two refractive indices is greater than 0.3, this design choice in this example of the present application is not arbitrary. The following is an analysis of the refractive index range selected for the coupling-in grating 21 and its technical effects.

[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 materials for the first film layer 22 can be ensured, facilitating production and manufacturing.

[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 regulating 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 ensure that more light can be coupled into the substrate 1 for total internal reflection propagation as expected, thereby improving coupling efficiency.

[0086] Properly designing the thickness of the first film layer 22 not only improves optical performance but also provides better physical protection for the coupling grating 21 and enhances its structural stability. This helps to mitigate the negative impact of external environmental factors (such as temperature fluctuations and mechanical stress) on the coupling grating 21, thereby extending the service life of the entire coupling structure.

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

[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 enhancing the structural stability and manufacturing accuracy of the coupling structure.

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

[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 reduce reflection and scattering, allowing light to be more effectively guided into the substrate 1, thereby improving coupling efficiency. This improved coupling efficiency directly leads to improved 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. Furthermore, the thickness range of the first film layer 22 in this example of the present application does not excessively increase the thickness dimension of the entire coupling structure.

[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. Furthermore, an overly thin first film layer 22 may be difficult to precisely control during the manufacturing process, resulting in unstable performance. Optically, an overly thin first film layer 22 may not produce sufficient phase delay to guide light into the waveguide, significantly reducing coupling efficiency.

[0093] If the thickness of the first film layer 22 exceeds 100 nm, it may introduce excessive absorption and scattering losses, resulting in excessive attenuation of light during the coupling process. This also reduces coupling efficiency and affects the brightness and clarity of the AR image. Furthermore, an excessively thick first film layer 22 may increase manufacturing cost and complexity due to the need for longer coating time and more material.

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

[0095] In the coupling structure provided in the present embodiment, the period of the coupling grating 21 is a key factor affecting light diffraction efficiency. Within the range of 200 nm to 500 nm, the grating period of the coupling grating 21 is well matched to the wavelength of the incident light, enabling effective diffraction of the light as it passes through the coupling grating 21, thereby efficiently coupling the light 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 undergo different degrees of diffraction when passing through the coupling grating with an appropriate period, thereby achieving effective coupling over 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 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 diffraction and reflection of light. In the range of 30nm to 400nm, the grating depth can properly balance diffraction and reflection, so that more light is 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 offer advantages such as simple structure and ease of fabrication, as well as efficient diffraction in specific directions. By optimizing the period and depth of a one-dimensional grating, its one-dimensional diffraction properties can be further enhanced, enabling even 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, thereby optimizing the coupling process of light between the coupling grating 21 and the first film layer 22. 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 improved image quality. This is because more light is effectively coupled into the substrate 1, making the virtual image brighter and clearer, and significantly improving the user's visual experience.

[0104] Due to the improved coupling efficiency, the coupling structure provided by the embodiment of the present application can be applied to more application scenarios with complex lighting conditions. For example, it can provide stable image display effects in both strong outdoor light and weak indoor light environments.

[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, the second film layer 23 is made of metallic silver or aluminum. Silver and aluminum have excellent reflective properties, effectively reflecting light from the coupling grating 21 back into the substrate 1, thereby reducing light loss and improving coupling efficiency. This helps enhance the brightness and clarity of the AR image, improving 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. This 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, making them easy to integrate with other film layers or structures. Furthermore, these metal materials are easily processed through processes such as physical vapor deposition (PVD) and chemical vapor deposition (CVD), facilitating 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 herein, the second film layer 23 acts as a reflective layer, and its thickness directly affects the light reflection efficiency. Within the 60nm to 5um range proposed in this example, a metal coating layer such as silver or aluminum can form a continuous and uniform thin film, effectively reflecting light back into the substrate 1, reducing light loss and improving coupling efficiency.

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

[0113] The second film layer 23 can be processed in a thickness range of 60 nm to 5 μm using 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 uniformity and consistency in the thickness of the metal coating.

[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. This helps to resist the effects of external environmental factors (such as temperature and humidity) 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 longer processing time and higher energy consumption costs. 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 and is transmitted by total reflection.

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

[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 its compatibility with a variety of grating types. This adaptability to a variety of grating types enables the coupling structure of the present application to flexibly address diverse application requirements. For example, in scenarios requiring high diffraction efficiency, a blazed grating or a step grating can be selected; in scenarios requiring higher 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 the 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 outside of the first film layer 22, that is, on the side away from the substrate 1 and the coupling grating 21. This arrangement forms a multi-layered coupling structure, with each layer performing a specific function.

[0121] The coupling grating 21 is a key component for light to enter the substrate 1. By designing optical parameters such as its periodicity and depth, the coupling grating 21 effectively diffracts and couples incident light. Optimizing its material refractive index and structural parameters ensures that light enters the substrate 1 with high efficiency.

[0122] The first film layer 22 further enhances the coupling efficiency and optimizes light propagation within the substrate 1. By selecting appropriate materials (e.g., materials with a refractive index between 1.4 and 2.1) and coating methods, the first film layer 22 can improve light transmittance and reduce light loss.

[0123] The second film layer 23, a metal coating (such as silver or aluminum), primarily serves a reflective and protective function. It effectively reflects uncoupled light back into the substrate 1, further improving light utilization. Furthermore, the metal coating protects the first film layer 22 and the coupling grating 21 from external damage.

[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 light loss and scattering.

[0125] The arrangement of the first film layer 22 and the second film layer 23, especially the reflective 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 over the light propagation path by optimizing the structure and material parameters of each layer. This not only improves coupling efficiency but also optimizes the propagation characteristics of light within substrate 1, thereby enhancing the overall performance of the diffractive 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 has excellent transparency and optical properties, is highly stable, and can withstand certain temperature changes. It is suitable for optical devices that require high transparency and optical properties.

[0129] Resin materials are characterized by low cost, ease of processing and molding, and light weight. They are suitable for applications where weight and production costs are strictly controlled.

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

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

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

[0133] The design of the coupling structure in this application achieves precise control of the light propagation path by optimizing the refractive index, period, depth, and other parameters of the coupling grating 21, as well as the rational configuration of the first film layer 22 and the second film layer 23, thereby achieving the goal of improving coupling efficiency. This design concept 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 this application was 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 , ie, the coupling structure of the present application.

[0139] The coupling-in structure 2 includes a coupling-in grating 21 and a second film layer 23 disposed on the coupling-in grating 21 , ie, the comparative 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 comparative structure two.

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

[0142] Experimental conditions: Green light was used as the test light source, and the light transmission and diffraction processes under different coupling structures were simulated.

[0143] 2. Simulation results show:

[0144] Incoupling 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 3 (compared with structure 2): the coupling efficiency of green light is 8.6%.

[0148] Coupling structure 4 (compared with 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] Overall, the coupling structure (coupling structure 1) provided in this embodiment significantly improves the coupling efficiency of green light by introducing the first film layer 22 and the second film layer 23. Compared to other comparative structures, the coupling structure provided in this application has a significant advantage in optical efficiency, which helps improve the overall performance of the AR diffractive optical structure.

[0155] In summary, simulation experiments have verified 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 proposed in 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 this application has significantly improved red light coupling efficiency and blue light coupling efficiency compared to other comparative structures, and the description will not be repeated here.

[0157] According to another embodiment of the present application, a diffractive optical structure is provided. Figure 1 The diffraction optical structure includes: the coupling-in structure and the coupling-out part 3 as described above, 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 diffractive optical structure of this application primarily consists of two components: an incoupling structure and an outcoupling portion 3. As previously described, the incoupling structure comprises a substrate 1, an incoupling grating 21, a first film layer 22, and a second film layer 23. The incoupling portion 2 is used to efficiently couple light into the substrate 1 for total internal reflection transmission. The outcoupling portion 3, disposed on the substrate 1, primarily couples light from the incoupling portion 2, allowing the human eye to perceive the virtual image projected by the optical engine 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 diffraction 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 a core component of the optical display device, responsible for generating and projecting the light required for virtual images. In the embodiment of the present application, the optical engine 4 is positioned on one side of the substrate 1, opposite the coupling element 2. This allows light emitted by the optical engine 4 to directly impinge on the coupling element 2, achieving efficient light coupling.

[0162] As previously mentioned, the diffractive optical structure comprises an incoupling structure and an outcoupling portion 3. The incoupling structure efficiently couples light emitted by the optical engine 4 into the substrate 1, while the outcoupling portion 3 couples light out of the substrate 1, forming a virtual image visible to the human eye. These two components work together to achieve efficient light transmission and display.

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

[0164] The specific implementation of the optical display device of the embodiment of the present application can refer to the various embodiments of the above-mentioned coupling structure and 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.

[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 for illustration only and are not intended to limit the scope of the present application. It should be understood by those skilled in the art that the above examples 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 portion (2) arranged on the substrate (1), wherein the coupling portion (2) is used to couple light into the substrate (1) and cause the light to be transmitted by total reflection within the substrate (1); The coupling portion (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%; 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 grating (21) again, and the average efficiency R0 of the total reflection propagation is greater than 50%.

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

4.

3. The coupling structure according to claim 1, wherein: 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-in grating (21) is 200nm≤T≤500nm, and the grating depth h1 of the coupling-in grating (21) is 30nm≤h1≤400nm. The coupling structure according to claim 1 , wherein: 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, wherein: The material of the second film layer (23) includes metallic silver or metallic 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, wherein: 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), reflected by the coupling-in part (2), and then enters the substrate (1) for total reflection transmission.

10. The coupling structure according to claim 1, wherein: The first film layer (22) is stacked and arranged on a surface of the coupling-in grating (21) facing away from the substrate (1); The second film layer (23) is stacked on the outside 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) couples out the light from the coupling part (2).

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

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