Diffractive optical waveguide, display module and preparation method thereof

Abstract

The application discloses a kind of diffractive optical waveguide, display module and preparation method thereof, diffractive optical waveguide includes sequentially arranged in-coupling region and out-coupling region;In-coupling region and out-coupling region are configured as micro-nano structure with light diffraction function;Out-coupling region includes N adjacent partitions, the design parameters of micro-nano structure in each partition are different, the out-coupling efficiency and downward transmission rate of each partition are different, ensure that the out-coupling transmission efficiency of each partition is not less than the product of initial out-coupling efficiency and initial out-coupling efficiency threshold ε, to ensure the consistency of light out-coupling brightness.The display module of the application includes diffractive optical waveguide and light machine module, light machine module adopts horizontal design, can meet the design requirement of large pupil, design form is consistent with diffractive optical waveguide, realize super-compact module integration.The preparation method of diffractive optical waveguide is also disclosed, so that the light out-coupling brightness consistency of prepared diffractive optical waveguide is high.

Description

Technical Field

[0001] This invention belongs to the field of display device technology, specifically relating to a diffractive waveguide, a display module, and a method for fabricating the same. Background Technology

[0002] Head-up display (HUD) technology projects driving information, navigation data, and other information onto a display screen or windshield, presenting virtual driving and navigation information in real-world traffic scenarios, thus establishing an interactive feedback loop between the real world, the information world, and the user. Based on product form, HUDs can be mainly divided into CHUD (Combiner HUD), WHUD (Windshield HUD), and AR-HUD (Augmented Reality HUD) technologies.

[0003] Augmented Reality (AR) displays allow observers to view images or data superimposed on the real environment while viewing real objects, thus gaining widespread application across various fields. This is because AR displays offer seamless, real-time interaction with the real environment—a feature lacking in traditional displays—providing users with a completely new visual experience. However, a primary challenge in AR displays is reducing the size and weight of the display device while providing sufficient brightness and field of view to achieve both portability and a high spatial and angular resolution for a seamless blend of augmented and real-world visuals.

[0004] Augmented reality (AR) display optics technology has evolved to include several main solutions, such as coaxial side-view prisms, arrayed semi-permeable waveguides, freeform surfaces, and diffractive waveguides, each offering different display performance. Current automotive head-up displays primarily utilize freeform surface designs, resulting in bulky modules and insufficient virtual image viewing distance. Diffractive waveguide technology offers the advantages of small size and thinness, and AR modules based on diffractive waveguides maintain this ultra-small size advantage, making them more suitable for wearable display integration and pre-installation in automotive head-up displays. Summary of the Invention

[0005] To address the aforementioned issues, this invention proposes a diffractive waveguide, a display module, and a method for fabricating the same. By partitioning the diffractive waveguide and ensuring that the structural design parameters mapped within each partition are different, the efficiency of the emitted light is guaranteed to be balanced.

[0006] To achieve the above-mentioned technical objectives and effects, the present invention is implemented through the following technical solution: In a first aspect, the present invention provides a diffractive optical waveguide, comprising a coupling-in region and a coupling-out region arranged sequentially; Both the coupling-in region and the coupling-out region are configured as micro / nano structures with light diffraction capabilities. The coupling region includes Each of the three adjacent partitions has different micro / nano structure design parameters, different coupling efficiency, and different downward conduction efficiency. The coupling efficiency of each partition is not lower than the initial coupling efficiency and the initial coupling efficiency threshold. The product of these factors results in a high degree of consistency in the brightness of the emitted light.

[0007] Optionally, the partition of the coupling-out region closest to the coupling-in region is designated as the first partition, and the downward conduction rate of the first partition is... The coupling efficiency is The second partition is the next partition, and the downward conduction rate of the second partition is... The coupling efficiency is ;...;No. Partition, the first The downward propagation rate of the partition is The coupling efficiency is ...; until the Partition, the first The downward propagation rate of the partition is The coupling efficiency is ;in > >...> , < <...< .

[0008] Optionally, the length of each partition along the direction of light transmission It is obtained by calculation using the following formula:

[0009]

[0010] In the formula, The distance between points of total reflection. For waveguide thickness, For wavelength, For the grating period, The refractive index of the waveguide, In the first The maximum number of total internal reflections in the partition. , It is an integer.

[0011] Optionally, the first Maximum total internal reflection times of the partition The process of obtaining it is as follows: go through The coupling efficiency after subtotal reflection is not less than the product of the initial coupling efficiency and the initial coupling efficiency threshold; Maximum total reflection count in the first partition Satisfying the formula: When the number of total internal reflections in the first partition is greater than the maximum number of total internal reflections. If the coupling efficiency is lower than the initial coupling efficiency threshold, then the coupling efficiency is lower than the threshold value. ; Maximum total internal reflection count in the second partition Satisfying the formula: ; The maximum total reflection count in the third partition Satisfying the formula: ...and so on. No. The maximum total reflection count for each partition Satisfying the formula: ; in, For the initial coupling efficiency, This is the initial coupling efficiency threshold.

[0012] Optionally, the diffractive waveguide is made of a material with a visible light transmittance of more than 70%, including resin and glass.

[0013] Optionally, the coupling-in region is elongated, and each partition in the coupling-out region is elongated.

[0014] Optionally, the micro-nano structure design parameters within each partition include the micro-nano structure period, micro-nano structure depth, and micro-nano structure duty cycle; the micro-nano structure period remains the same for each partition of the coupling region.

[0015] In a second aspect, the present invention provides a display module, comprising: the diffractive waveguide and the optomechanical module as described in any one of the first aspects; The optomechanical module includes an image source and a lens group arranged in sequence; the lens group is matched with the coupling region to meet the exit pupil design requirements and is fitted to the coupling region.

[0016] Optionally, the lens group includes a spherical mirror, a spherical cemented mirror, a first aspherical mirror, a second aspherical mirror, and a reflector arranged in sequence; a gap is provided between the first aspherical mirror and the second aspherical mirror; the reflector is used to reflect light so that the light is incident on the coupling region.

[0017] Optionally, the optomechanical module is elongated, with its surface length being close to that of the diffractive waveguide.

[0018] Optionally, the maximum diameter of the exit pupil of the optical engine module is greater than or equal to 100 mm, satisfying a 1′ resolution angle.

[0019] Thirdly, the present invention provides a method for fabricating a diffractive optical waveguide, comprising: Determine the partition layout of the coupled area to form several partitions; The design parameters of the micro / nano structures mapped within each partition are determined. The design parameters of the micro / nano structures within each partition are different, and the coupling efficiency and downward conduction rate of each partition are different. The coupling conduction efficiency of each partition is not lower than the initial coupling efficiency and the initial coupling efficiency threshold. The product of these factors results in a high consistency in the brightness of the coupled light rays; The corresponding photolithography parameters are determined based on the micro / nano structure design parameters mapped within each partition. Stereolithography is performed on each partition according to the corresponding photolithography parameters, and stereolithography light field energy is deposited in the photoresist, so that the energy deposited in different partitions is different; Expose the substrate surface coated with photosensitive adhesive, accumulate the exposure energy, and superimpose a uniform interference energy surface across the entire coupling region; Developed in a special developing solution, regions with different energy deposits form different structural shapes during the same development time, thus obtaining a diffractive waveguide as described in any of the first aspects.

[0020] Fourthly, the present invention provides a method for fabricating a diffractive optical waveguide, comprising: Determine the partition layout of the coupled area to form several partitions; The design parameters of the micro / nano structures mapped within each partition are determined. The design parameters of the micro / nano structures within each partition are different, and the coupling efficiency and downward conduction rate of each partition are different. The coupling conduction efficiency of each partition is not lower than the initial coupling efficiency and the initial coupling efficiency threshold. The product of these factors results in a high consistency in the brightness of the coupled light rays; The corresponding interference exposure dose is determined based on the micro-nano structure design parameters mapped within each partition, and the exposure time corresponding to each partition is obtained based on the interference exposure dose. Expose the substrate surface coated with photosensitive adhesive, accumulate the exposure energy, and superimpose the interference energy surface in the coupling region; Developed in a special developing solution, different energy-accumulated partitions form different structural shapes during the same development time, thus obtaining a diffractive waveguide as described in any of the first aspects.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention employs a partitioned design for the diffractive waveguide, with each partition containing different micro / nano structure design parameters. Each partition exhibits varying coupling efficiency and downward conduction rate, ensuring that the coupling efficiency of each partition is not lower than the initial coupling efficiency and its threshold value. This ensures the consistency of the brightness of the coupled light.

[0022] The optomechanical module in the display module of this invention adopts a horizontal design, which can meet the requirements of large exit pupil design. The design shape fits the diffraction waveguide, realizing ultra-compact module integration. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein: Figure 1 This is a schematic diagram of the structure of a diffractive waveguide according to an embodiment of the present invention; Figure 2(a) shows the light emission intensity of the coupling region after partitioning design; Figure 2(b) shows the light emission intensity of the coupling region without partitioning design; Figure 3 This is a partitioning principle of the coupling region according to one embodiment of the present invention; Figure 4 The light intensity distribution of the coupling region is shown in Table 1. Figure 5 This is a schematic diagram of the structure of an optomechanical module according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the optical path of an optomechanical module according to an embodiment of the present invention; Figure 7 This is a schematic diagram showing the length and width of an optomechanical module according to an embodiment of the present invention; Figure 8 This is an MTF diagram of an optomechanical module according to an embodiment of the present invention; Figure 9 This is a dot diagram of an optomechanical module according to an embodiment of the present invention; Figure 10 This is a flowchart of the fabrication method of the diffractive waveguide in Example 3; Figure 11 This is a flowchart of the fabrication method of the diffractive waveguide in Example 4; Figure 12 This is a schematic diagram illustrating the application of the display module in the head-up display field according to an embodiment of the present invention; in: 1-Diffractive waveguide, 11-Coupled-in region, 12-Coupled-out region, 2-Optical-mechanical module, 21-Spherical mirror, 22-Spherical cemented mirror, 23-First aspherical mirror, 24-Second aspherical mirror, 25-Reflector, 26-Image source. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may include different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0026] In the description of this invention, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0027] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0028] The application principle of the present invention will be described in detail below with reference to the accompanying drawings.

[0029] Example 1

[0030] like Figure 1 The diagram shows the structure of diffractive waveguide 1, with coupling region 11 being... Figure 1 The leftmost strip shown is used to couple light rays incident from external devices (such as the optomechanical module 2). The coupling region 12 is the outgoing light region, used to achieve pupil-expanding light transmission, including... Figure 1 The diagram shows all regions except the leftmost long strip. Since both the coupling region 11 and the coupling region 12 of the diffractive waveguide 1 are configured as micro / nano structures with light diffraction capabilities (including relief gratings, holographic gratings, volume gratings, liquid crystal gratings, etc.), each time light comes into contact with the micro / nano structure, transmission diffraction and reflection diffraction will occur. If the structure of the coupling region 12 is designed as a single, monolithic structure, the emission efficiency will inevitably decrease rapidly with the increase of the transmission distance.

[0031] like Figure 1 As shown, a diffractive waveguide 1 provided in this embodiment of the invention includes a coupling-in region 11 and a coupling-out region 12 arranged sequentially. Both the coupling-in region 11 and the coupling-out region 12 are configured as micro-nano structures with light diffraction capabilities. The coupling region 12 includes Each of the three adjacent partitions has different micro / nano structure design parameters, different coupling efficiency, and different downward conduction efficiency. The coupling efficiency of each partition is not lower than the initial coupling efficiency and the initial coupling efficiency threshold. The product of these factors results in a high degree of consistency in the brightness of the emitted light.

[0032] As shown in Figures 2(a) and 2(b), Figure 2(a) shows the light emission intensity of the coupling region 12 after partitioning design, and Figure 2(b) shows the light emission intensity of the coupling region 12 without partitioning design. It can be seen that in this embodiment of the invention, by partitioning the diffractive waveguide 1, the micro / nano structure design parameters within each partition are different, resulting in different coupling efficiencies and downward conduction rates for each partition. The coupling conduction efficiency of each partition is not lower than the initial coupling efficiency and the initial coupling efficiency threshold. The product of these components results in high consistency in the brightness of the coupled light. In specific implementations, the diffractive waveguide 1 is made of a material with a visible light transmittance higher than 70%, such as resin or glass.

[0033] In one specific embodiment of the present invention, such as Figure 3 The diagram shows the partitioning principle of the coupling-out region 12. The partition of the coupling-out region 12 closest to the coupling-in region 11 is the first partition, and the downward conduction rate of the first partition is... The coupling efficiency is The second partition is the next partition, and the downward conduction rate of the second partition is... The coupling efficiency is ;...;No. Partition, the first The downward propagation rate of the partition is The coupling efficiency is ...; until the Partition, the first The downward propagation rate of the partition is The coupling efficiency is ;in > >...> , < <...< .

[0034] Based on the above design, the length of each partition along the light transmission direction is... It is obtained by calculation using the following formula:

[0035]

[0036] In the formula, The distance between points of total reflection. For waveguide thickness, For wavelength, For the grating period, The refractive index of the waveguide, In the first The maximum number of total internal reflections in the partition. , It is an integer.

[0037] Since the light rays coupled from the coupling region 11 undergo diffraction and reflection in multiple directions when they touch the coupling region 12, therefore, the first The maximum total reflection count for each partition The process of obtaining it is as follows: go through The coupling efficiency after subtotal reflection is not lower than the initial coupling efficiency and the initial coupling efficiency threshold. The product; The maximum total internal reflection count in the first zone Satisfying the formula: When the number of total internal reflections in the first zone is greater than the maximum number of total internal reflections. If the coupling efficiency is lower than the initial coupling efficiency threshold, then the coupling efficiency is lower than the threshold value. ; The maximum total internal reflection count in the second partition Satisfying the formula: ; The maximum number of total internal reflections in the third zone Satisfying the formula: ...and so on. No. Maximum total internal reflection times of the partition Satisfying the formula: ; in, For the initial coupling efficiency, This is the initial coupling efficiency threshold. The specific value can be adaptively designed according to actual needs, such as: The initial coupling efficiency threshold represents the efficiency relative to the initial coupling efficiency. The attenuation amount, when the coupling efficiency of a certain partition decreases to the initial coupling efficiency threshold, indicates that this partition is terminated, and the second partition is set; that is, when the formula is satisfied... At this point, the first partition ends, and the second partition begins. The horizontal length of the first coupled block in the horizontal arrangement is... (Length of each partition along the direction of light transmission) Then it is Of course, the specific horizontal length can be slightly greater or slightly less than 200 mm. The specific values ​​are as follows. Furthermore, the method for calculating the second partition and subsequent partitions is the same as the principle described above.

[0038] Table 1 shows a preferred coupling partitioning parameter table, which is divided into 9 partitions. The first partition has a grating period of 440nm, a depth of 50nm, and a duty cycle of 0.5; the second partition has a grating period of 440nm, a depth of 60nm, and a duty cycle of 0.5; the third partition has a grating period of 440nm, a depth of 70nm, and a duty cycle of 0.5; the fourth partition has a grating period of 440nm, a depth of 80nm, and a duty cycle of 0.5; the fifth partition has a grating period of 440nm, a depth of 90nm, and a duty cycle of 0.5; the sixth partition has a grating period of 440nm, a depth of 100nm, and a duty cycle of 0.5; the seventh partition has a grating period of 440nm, a depth of 130nm, and a duty cycle of 0.4; the eighth partition has a grating period of 440nm, a depth of 170nm, and a duty cycle of 0.4; and the ninth partition has a grating period of 440nm, a depth of 270nm, and a duty cycle of 0.5.

[0039] Table 1

[0040] Figure 4 The light intensity distribution of the coupling region 12 is shown in Table 1 under the parameter design. To characterize the uniformity of the entire coupling region 12, nine points are taken in the figure, and the intensity data is read and normalized to obtain the uniformity of each point. The uniformity of point 1 is 88.62%, point 2 is 82.49%, point 3 is 89.19%, point 4 is 110.83%, point 5 is 102.54%, point 6 is 111.35%, point 7 is 102.46%, point 8 is 101.12%, and point 9 is 111.40%.

[0041] In one specific embodiment of the present invention, the diffractive waveguide is made of a material with a visible light transmittance of more than 70%, and in the specific implementation process, it can be made of resin or glass.

[0042] In one specific embodiment of the present invention, the coupling-in region 11 is elongated, and each partition in the coupling-out region 12 is elongated.

[0043] In one specific embodiment of the present invention, the micro-nano structure design parameters in each partition include the micro-nano structure period, the micro-nano structure depth, and the micro-nano structure duty cycle; the micro-nano structure period of each partition in the coupling region remains the same.

[0044] Example 2

[0045] This invention provides a display module, such as Figure 5-6 As shown, it includes: the diffractive waveguide 1 and the optomechanical module 2 described in Example 1; The optomechanical module 2 includes an image source 26 and a lens group arranged sequentially; in specific implementation, the image source 26 mainly includes LCOS, DLP, LCD, MEMS, etc. The lens group is matched with the coupling region 11 to meet the exit pupil design requirements, and is closely fitted with the coupling region 11 to achieve ultra-compact integration.

[0046] like Figure 5-6 As shown, in a specific embodiment of the present invention, the lens group includes a spherical mirror 21, a spherical cemented mirror 22, a first aspherical mirror 23, a second aspherical mirror 24, and a reflector 25 arranged sequentially. A gap exists between the first aspherical mirror 23 and the second aspherical mirror 24, allowing air to be present. The reflector 25 is used to reflect light, allowing the light to enter the coupling region 11. In actual operation, the spherical mirror 21, the spherical cemented mirror 22, the first aspherical mirror 23, and the second aspherical mirror 24 are mainly used to achieve a large exit pupil projection optical design. The reflector is used to bend light and match the position with the coupling region 11, so that the maximum diameter of the exit pupil of the optical engine module 2 in this embodiment is greater than or equal to 100mm, satisfying the 1′ resolution angle.

[0047] In one specific embodiment of the present invention, the optomechanical module 2 is elongated, with its surface length being close to that of the diffractive waveguide 1 and its width accounting for a very small proportion. The light emitted from the optomechanical module 2 is reflected and deflected, which greatly saves the integration volume, makes efficient use of space, and can maximize the reduction of volume to achieve display module integration.

[0048] In a preferred simulation scenario of this invention, a 2.6-inch LCD is used. By designing the lens group size and surface parameters, a display module with a field of view of 10°*6° can be achieved, with a maximum exit pupil diameter of 180mm. The total length of the optical-mechanical module 2 is 345mm. See details below. Figure 7 . Figure 8 and Figure 9 The optical transfer function (MTF) plot and dot plot of the optical engine module 2 are shown respectively. It can be seen that the optical engine module 2 can meet the requirement that the MTF values ​​of the center field of view and the edge field of view are greater than 0.3 when there are 20 line pairs / mm. That is, it can distinguish one pixel on the LCD and meet the resolution requirements.

[0049] This invention, through a partitioned design of the coupling region, rationally distributes the diffraction energy per unit area, achieving balanced diffraction efficiency at different locations within the eyebox, thereby ensuring uniform pupil expansion of the diffracted waveguide. This design has broad applicability in many fields. Figure 12As an application demonstration of a head-up display based on the present invention, the light emitted by the diffracted light wave is reflected by the windshield and forms an eye-box area at a certain position, allowing the observer to view the complete image.

[0050] Example 3

[0051] This invention provides a method for fabricating a diffractive optical waveguide, such as... Figure 10 As shown, it includes: Determine the partition layout of the coupled area to form several partitions; The design parameters of the micro / nano structures mapped within each partition are determined. The design parameters of the micro / nano structures within each partition are different, and the coupling efficiency and downward conduction rate of each partition are different. The coupling conduction efficiency of each partition is not lower than the initial coupling efficiency and the initial coupling efficiency threshold. The product of these factors results in a high consistency in the brightness of the coupled light rays; The corresponding photolithography parameters are determined based on the micro / nano structure design parameters mapped within each partition. Stereolithography is performed on each partition according to the corresponding photolithography parameters, and stereolithography light field energy is deposited in the photoresist, so that the energy deposited in different partitions is different; Expose the substrate surface coated with photosensitive adhesive, accumulate the exposure energy, and superimpose a uniform interference energy surface across the entire coupling region; Developed in a special developing solution, regions with different energy accumulations form different structural shapes during the same development time, thus obtaining a diffractive waveguide as described in Example 1.

[0052] Example 4

[0053] This invention provides a method for fabricating a diffractive optical waveguide, such as... Figure 11 As shown, it includes: Determine the partition layout of the coupled area to form several partitions; The design parameters of the micro / nano structures mapped within each partition are determined. The design parameters of the micro / nano structures within each partition are different, and the coupling efficiency and downward conduction rate of each partition are different. The coupling conduction efficiency of each partition is not lower than the initial coupling efficiency and the initial coupling efficiency threshold. The product of these factors results in a high consistency in the brightness of the coupled light rays; The corresponding interference exposure dose is determined based on the micro-nano structure design parameters mapped within each partition, and the exposure time corresponding to each partition is obtained based on the interference exposure dose. Expose the substrate surface coated with photosensitive adhesive, accumulate the exposure energy, and superimpose the interference energy surface in the coupling region; Developed in a special developing solution, different energy-accumulated partitions form different structural shapes during the same development time, thus obtaining a diffractive waveguide as described in Example 1.

[0054] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only used to facilitate the description of the present invention and to simplify the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of the present invention.

[0055] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A diffractive optical waveguide, characterized in that: This includes sequentially set coupling-in and coupling-out regions; Both the coupling-in region and the coupling-out region are configured as micro / nano structures with light diffraction capabilities. The coupling region includes N adjacent partitions, each with different micro / nano structure design parameters, different coupling efficiency and downward conduction rate, and a coupling conduction efficiency of each partition that is not less than the product of the initial coupling efficiency and the initial coupling efficiency threshold ε, resulting in high consistency of light coupling brightness. The partition of the coupling-out region closest to the coupling-in region is designated as the first partition, and the downward conduction rate of the first partition is... The coupling efficiency is The second partition is the second partition, and the downward conduction rate of the second partition is... The coupling efficiency is ...; up to the Nth partition, the downward propagation rate of the Nth partition is The coupling efficiency is ;in , ; The length Li of each partition along the light transmission direction is calculated using the following formula: In the formula, d is the total internal reflection point spacing, t is the waveguide thickness, λ is the wavelength, p is the grating period, and n is the waveguide refractive index. To find the maximum number of total internal reflections in the i-th partition, where i is an integer; The maximum total internal reflection number of the i-th partition The process of obtaining it is as follows: go through The coupling efficiency after subtotal reflection is not less than the product of the initial coupling efficiency and the initial coupling efficiency threshold; The maximum total internal reflection count in the first zone Satisfying the formula: When the number of total internal reflections in the first zone is greater than the maximum number of total internal reflections. If the coupling efficiency is lower than the initial coupling efficiency threshold ε, then the coupling efficiency is lower than the initial coupling efficiency threshold ε. The maximum total internal reflection count in the second partition Satisfying the formula: ; The maximum number of total internal reflections in the third zone Satisfying the formula: ; ...and so on. Maximum total internal reflection count in the Nth partition Satisfying the formula: .

2. The diffractive waveguide according to claim 1, characterized in that: The diffractive waveguide is made of a material with a visible light transmittance of more than 70%, including resin and glass.

3. The diffractive waveguide according to claim 1, characterized in that: The coupling-in region is elongated, and each partition in the coupling-out region is elongated.

4. A diffractive optical waveguide according to claim 1, characterized in that: The micro-nano structure design parameters within each partition include the micro-nano structure period, micro-nano structure depth, and micro-nano structure duty cycle; the micro-nano structure period remains the same for each partition of the coupling region.

5. A display module, characterized in that, include: The diffractive waveguide and optomechanical module according to any one of claims 1-4; The optomechanical module includes an image source and a lens group arranged in sequence; The lens group is matched with the coupling region to meet the exit pupil design requirements and is in close contact with the coupling region.

6. A display module according to claim 5, characterized in that, The lens group includes a spherical mirror, a spherical cemented mirror, a first aspherical mirror, a second aspherical mirror, and a reflector arranged in sequence; a gap is provided between the first aspherical mirror and the second aspherical mirror; the reflector is used to reflect light so that the light is incident on the coupling region.

7. A display module according to claim 5, characterized in that: The optomechanical module is elongated, and its surface length is close to that of the diffractive waveguide.

8. A display module according to claim 5, characterized in that: The maximum diameter of the exit pupil of the optical engine module is greater than or equal to 100mm, satisfying a resolution angle of 1′.

9. A method for fabricating a diffractive optical waveguide, characterized in that, include: Determine the partition layout of the coupled area to form several partitions; The design parameters of the micro-nano structures mapped in each partition are determined. The design parameters of the micro-nano structures in each partition are different. The coupling efficiency and downward conduction rate of each partition are different. The coupling conduction efficiency of each partition is not less than the product of the initial coupling efficiency and the initial coupling efficiency threshold ε, so that the consistency of the light coupling brightness is high. The corresponding photolithography parameters are determined based on the micro / nano structure design parameters mapped within each partition. Stereolithography is performed on each partition according to the corresponding photolithography parameters, and stereolithography light field energy is deposited in the photoresist, so that the energy deposited in different partitions is different; Expose the substrate surface coated with photosensitive adhesive, accumulate the exposure energy, and superimpose a uniform interference energy surface across the entire coupling region; Developed in a special developing solution, regions with different energy deposits form different structural shapes during the same development time, thus obtaining a diffractive waveguide as described in any of claims 1-4.

10. A method for fabricating a diffractive optical waveguide, characterized in that, include: Determine the partition layout of the coupled area to form several partitions; The design parameters of the micro-nano structures mapped in each partition are determined. The design parameters of the micro-nano structures in each partition are different. The coupling efficiency and downward conduction rate of each partition are different. The coupling conduction efficiency of each partition is not less than the product of the initial coupling efficiency and the initial coupling efficiency threshold ε, so that the consistency of the light coupling brightness is high. The corresponding interference exposure dose is determined based on the micro-nano structure design parameters mapped within each partition, and the exposure time corresponding to each partition is obtained based on the interference exposure dose. Expose the substrate surface coated with photosensitive adhesive, accumulate the exposure energy, and superimpose the interference energy surface in the coupling region; Developed in a special developing solution, different energy-accumulated partitions form different structural shapes during the same development time, thus obtaining the diffractive waveguide as described in any of claims 1-4.

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