Diffractive optical waveguide and display module

Abstract

The present invention relates to a diffractive optical waveguide and a display module. The diffractive optical waveguide comprises a waveguide substrate, the waveguide substrate comprising an in-coupling region and an out-coupling region. The direction from the in-coupling region to the out-coupling region is a first direction. The out-coupling region comprises a first sub-out-coupling region and a second sub-out-coupling region. The first sub-out-coupling region comprises at least two first out-coupling blocks which are sequentially arranged in the first direction, and efficiency modulation functions of the at least two first out-coupling blocks present a progressive trend in the first direction. In a direction perpendicular to the first direction, the second sub-out-coupling region comprises at least two second out-coupling blocks which are sequentially arranged in a direction away from the first sub-out-coupling region, and efficiency modulation functions of the at least two second out-coupling blocks present a progressive trend in the direction away from the first sub-out-coupling region. In the diffractive optical waveguide of the present invention, efficiency partitioning can be separately performed on the first sub-out-coupling region and the second sub-out-coupling region, thereby improving the uniformity of brightness among different observation images in the range of an eyebox.

Description

Diffractive optical waveguide and display module Technical Field

[0001] The present invention relates to the field of display technology, and in particular to a diffraction optical waveguide and a display module. Background Art

[0002] [Corrected 13 / 12 / 2023 in accordance with Regulation 26] Augmented reality (AR) displays enable viewers to view images or data superimposed on the real environment while simultaneously viewing external objects. Therefore, they are widely used in various fields, particularly in the military and consumer sectors. From Google's globally popular Google Glass in 2012, to Facebook's $2 billion acquisition of Oculus in 2014, to my experience trying out Microsoft's HoloLens during my 2016 visit to the US, Magic Leap, a Google-backed company, and Microsoft's HoloLens 2, OPPO's AR glasses, and the recently popular AR-HUD, all of these have demonstrated the enormous potential of AR displays. This is because AR displays offer seamless, real-time interaction with the real environment, a feature not available on traditional display devices, bringing users a completely new visual experience. However, the primary challenge in AR displays is how to reduce the size and weight of the display device while ensuring sufficient brightness and field of view, achieving lightweight devices and high spatial and angular resolution for a fusion of virtual and real presentation.

[0003] The development of augmented reality display optical technology has led to the development of various solutions, including coaxial side-view prism solutions, arrayed semi-transparent film waveguide solutions, free-form surface solutions, and diffraction waveguide solutions. Each solution offers different display performance. Currently, in-vehicle head-up displays primarily utilize free-form surface designs, resulting in large module sizes. Many giants in the near-eye display field, including Microsoft, Meta, Apple, Google, and Snap, have adopted the more mainstream diffraction waveguide technology solution. Diffraction waveguides utilize the diffraction properties of gratings to design an "optical path," allowing light to propagate along a designed path and directing light from the micro-projection system into the human eye. The main advantages of these solutions are their small size and thinness. Augmented reality display modules based on diffraction waveguides maintain this ultra-small size advantage, making them more suitable for wearable display integration and pre-installation of automotive head-up displays.

[0004] The traditional diffraction optical waveguide solution adopts a coupling-turning-outcoupling light transmission design, and realizes a large eye box display through the theoretical method of diffraction pupil expansion. As shown in Figure 1, a traditional diffraction optical waveguide 100' includes a waveguide substrate 110', and the waveguide substrate 110' includes a coupling region 120' and an outcoupling region 130'. Among them, the entire outcoupling region 130' of the diffraction optical waveguide 100' is a grating structure with the same parameters. When the incident light is coupled from the coupling region 120' into the waveguide substrate 110' along the direction of the arrow in Figure 1 and transmitted within the waveguide substrate 110', the light energy that passes through the outcoupling region 130' for the first time and is diffracted by the grating structure of the outcoupling region 120' is the strongest. After that, the energy of each outgoing light gradually decreases. This is because outcoupling region 130' is a single grating structure with uniform diffraction efficiency. After each diffraction event, the total energy that can be transmitted is inevitably attenuated. The same diffraction efficiency inevitably results in lower output energy the next time. This leads to noticeable image brightness variations within the eyebox when the human eye moves through the waveguide. Therefore, conventional diffraction waveguides often suffer from uneven image brightness across the eyebox due to uneven control of diffraction efficiency in the outcoupling region.

[0005] Summary of the Invention

[0006] Based on this, it is necessary to provide a diffraction light waveguide and display module to solve the problem of how to improve the brightness uniformity of different observation images within the eye box.

[0007] A diffraction light waveguide, comprising a waveguide substrate, the waveguide substrate including an incoupling region and an outcoupling region located on one side of the incoupling region, the incoupling region being used to couple image light into the waveguide substrate, and the outcoupling region being used to couple out image light conducted in the waveguide substrate;

[0008] The direction from the coupling-in region to the coupling-out region is a first direction, the coupling-out region includes a first sub-coupling region and a second sub-coupling region, the first sub-coupling region is arranged close to the coupling-in region, and the second sub-coupling region is arranged away from the coupling-in region along a direction perpendicular to the first direction;

[0009] The first sub-coupling region includes at least two first outcoupling blocks arranged in sequence along the first direction, and efficiency modulation functions of the at least two first outcoupling blocks present a progressive trend along the first direction;

[0010] In a direction perpendicular to the first direction, the second sub-coupling region includes at least two second outcoupling blocks arranged sequentially in a direction away from the first sub-coupling region, and the efficiency modulation functions of the at least two second outcoupling blocks show a progressive trend in the direction away from the first sub-coupling region.

[0011] The diffraction optical waveguide using the technical solution of the present invention can reasonably distribute the diffraction energy per unit area by zoning the efficiency of the first sub-coupling area and the second sub-coupling area respectively, and balance the diffraction efficiency at different positions in the outcoupling area, thereby improving the brightness uniformity of different observation images within the eye box range, which is conducive to wide application.

[0012] In a feasible implementation, the number of the second sub-outcoupling regions is two, and the two second sub-outcoupling regions are symmetrically distributed with respect to the first sub-outcoupling region.

[0013] In a feasible implementation, the width of the first outcoupling block along the first direction perpendicular to the first direction is not less than the width of the light spot entering the coupling-in region, and the length of the first outcoupling block along the first direction is obtained based on a preset cutoff efficiency threshold of the image light in the first outcoupling block.

[0014] In a feasible implementation, the lengths of at least two of the first outcoupling blocks along the first direction decrease gradually.

[0015] In a feasible implementation, the length of the first outcoupling block along the first direction is n*d, where n is the number of total reflections, and is obtained based on the following steps:

[0016] A plurality of grating structures are provided in the first outcoupling block, a transmission efficiency of an initial grating structure to an adjacent grating structure along a direction perpendicular to the first direction is defined as a, and a transmission efficiency of an initial grating structure to an adjacent grating structure along the first direction is defined as b; and

[0017] The transmission efficiency of the image light in the first outcoupling block at the nth total reflection along the first direction perpendicular to the first direction is a*b n-1 The transmission efficiency of the image light along the first direction during the nth total reflection in the first outcoupling block is b n , the cutoff efficiency threshold of the image light in the first coupling block is preset to ε, when the efficiency of the nth transmission is a*b n-1 <a*ε, the first outcoupling block is terminated, and at this time, the length of the first outcoupling block along the first direction is n*d;

[0018] Where d is the total reflection point spacing, which is calculated based on formula (I):

[0019] d=t*tan(arcsin(λ / p / n0))*2(I);

[0020] In formula (I), t is the thickness of the waveguide substrate, λ is the incident wavelength, p is the grating period, and n0 is the waveguide refractive index.

[0021] In a feasible implementation, the width of the second outcoupling block along the direction perpendicular to the first direction is obtained based on a preset cutoff efficiency threshold of the image light in the second outcoupling block, and the length of the second outcoupling block along the first direction is equal to the length of the first sub-outcoupling region along the first direction.

[0022] In a feasible implementation, in a direction perpendicular to the first direction, the widths of at least two of the second outcoupling blocks decrease gradually in a direction away from the first sub-outcoupling region.

[0023] In a feasible implementation, the width of the second outcoupling block along the direction perpendicular to the first direction is n*d, where n is the number of total reflections, and is obtained based on the following steps:

[0024] The second outcoupling block is provided with a plurality of grating structures, and a transmission efficiency of an initial grating structure to an adjacent grating structure along a direction perpendicular to the first direction is defined as a, and a transmission efficiency of an initial grating structure to an adjacent grating structure along the first direction is defined as c; and

[0025] The transmission efficiency of the image light in the second outcoupling block at the nth total reflection along the first direction perpendicular to the first direction is a*c n-1 The transmission efficiency of the image light along the first direction during the nth total reflection in the second outcoupling block is c n , the cutoff efficiency threshold of the image light in the second outcoupling block is preset to ε, when the efficiency of the nth transmission is a*b n-1 <a*ε, the second outcoupling block is terminated, and at this time, the width of the second outcoupling block along the direction perpendicular to the first direction is n*d;

[0026] Where d is the total reflection point spacing, and is calculated based on formula (II): d = t*tan(arcsin(λ / p / n0))*2*sin(60°) (II);

[0027] In formula (II), t is the thickness of the waveguide substrate, λ is the incident wavelength, p is the grating period, and n0 is the waveguide refractive index.

[0028] A display module comprises any one of the above-mentioned diffraction light waveguides.

[0029] The display module of the technical solution of the present invention includes any of the above-mentioned diffraction light waveguides, which can reasonably distribute the diffraction energy per unit area by performing efficiency partitioning on the first sub-coupling area and the second sub-coupling area respectively, and balance the diffraction efficiency at different positions in the out-coupling area, thereby improving the brightness uniformity of different observation images within the eye box range, which is conducive to wide application.

[0030] In a feasible implementation, the display module is a head-up display module or an augmented reality wearable display module. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIG1 is a schematic diagram of light transmission in a conventional diffraction waveguide;

[0032] FIG2 is a schematic structural diagram of a diffraction optical waveguide according to an embodiment of the present invention;

[0033] FIG3 is a diagram showing the definition principle of the first outcoupling block in the diffraction optical waveguide according to an embodiment of the present invention;

[0034] FIG4 is a diagram showing the definition principle of the second outcoupling block in the diffractive optical waveguide according to one embodiment of the present invention;

[0035] FIG5 is a schematic diagram of the preparation of a diffraction optical waveguide according to the first embodiment of the present invention;

[0036] FIG6 is a schematic diagram of the preparation of a diffractive optical waveguide according to a second embodiment of the present invention;

[0037] FIG7 is a schematic diagram of the preparation of a diffractive optical waveguide according to a third embodiment of the present invention;

[0038] FIG8 is a schematic diagram of the design of aperture exposure during the preparation of a diffraction optical waveguide according to the third embodiment of the present invention;

[0039] FIG9 is a schematic diagram of a head-up display module according to an embodiment of the present invention;

[0040] FIG10 is a schematic diagram of an augmented reality wearable display module according to an embodiment of the present invention;

[0041] FIG11 is a schematic structural diagram of a diffraction optical waveguide according to Example 1 of the present invention;

[0042] FIG12 is a simulation diagram of light emission from the outcoupling region of the diffraction optical waveguide according to Example 1 of the present invention;

[0043] FIG13 is a schematic structural diagram of a diffraction optical waveguide according to Example 2 of the present invention;

[0044] FIG14 is a simulation diagram of light emission from the outcoupling region of the diffraction light waveguide at 0-degree incidence according to Example 2 of the present invention;

[0045] FIG15 is a simulation diagram of light emission from the outcoupling region of the diffraction light waveguide according to Example 2 of the present invention at -5 degrees of incidence;

[0046] FIG16 is a simulation diagram of light emission from the outcoupling region of the diffraction light waveguide according to Example 2 of the present invention at an incident angle of 5 degrees;

[0047] FIG17 is a schematic structural diagram of a diffraction optical waveguide of Comparative Example 1;

[0048] FIG18 is a simulation diagram of light emission from the outcoupling region of the diffraction optical waveguide of Comparative Example 1;

[0049] FIG19 is a schematic structural diagram of a diffraction optical waveguide of Comparative Example 2;

[0050] FIG20 is a simulation diagram of light emission from the outcoupling area of ​​the diffraction optical waveguide of comparative example 2. DETAILED DESCRIPTION

[0051] To make the above-mentioned objects, features, and advantages of the present invention more readily apparent, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. The following description sets forth numerous specific details to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art may make similar modifications without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0052] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly attached to the other element or there may be an intermediate element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only.

[0053] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0054] 2 , a diffraction optical waveguide 100 according to an embodiment of the present invention includes a waveguide substrate 110 . The waveguide substrate 110 includes an incoupling region 120 and an outcoupling region 130 located on one side of the incoupling region 120 . The incoupling region 120 is used to couple image light into the waveguide substrate 110 , and the outcoupling region 130 is used to couple out image light conducted within the waveguide substrate 110 , specifically performing emission and conduction functions.

[0055] The waveguide substrate 110 can be made of glass or resin and has high visible light transmittance. The aperture of the coupling region 120 is not less than the incident beam width, which is limited by parameters such as the refractive index and thickness of the waveguide substrate 110 and the incident angle.

[0056] The direction from the incoupling region 120 toward the outcoupling region 130 is a first direction (i.e., the x-direction in FIG. 2 ). The outcoupling region 130 includes a first sub-outcoupling region 131 and a second sub-outcoupling region 133. The first sub-outcoupling region 131 is disposed proximate to the incoupling region 120, while the second sub-outcoupling region 133 is disposed perpendicularly to the first direction (i.e., the y-direction or the opposite direction of the y-direction in FIG. 2 ) and away from the incoupling region 120. Specifically, the first sub-outcoupling region 131 is disposed opposite the incoupling region 120, while the second sub-outcoupling region 133 is located to one side of the first sub-outcoupling region 131 perpendicularly to the first direction, as shown in FIG. Preferably, the length of the side of the first sub-outcoupling region 131 proximate to the incoupling region 120 can be slightly greater than the width of the incoupling region 120 along the y-direction to ensure that the image light, after being transmitted through the incoupling region 120, remains within the first sub-outcoupling region 131.

[0057] The first sub-outcoupling region 131 includes at least two first outcoupling blocks 132 sequentially arranged along a first direction, and the efficiency modulation functions of the at least two first outcoupling blocks 132 are progressively increased along the first direction. The efficiency modulation function of the first outcoupling blocks 132 refers to the function of the first outcoupling blocks 132 to modulate the diffraction efficiency of light. The progressive trend of the efficiency modulation functions of the at least two first outcoupling blocks 132 along the first direction means that the light diffraction efficiency modulation functions of the at least two first outcoupling blocks 132 become increasingly stronger.

[0058] In this embodiment, there are four first outcoupling blocks 132, and each first outcoupling block 132 has a different characteristic structure and optical coupling performance. It should be noted that in the diffraction optical waveguide of the present invention, the number of first outcoupling blocks 132 is not limited to this.

[0059] In a direction perpendicular to the first direction, the second outcoupling sub-region 133 includes at least two second outcoupling blocks 134 sequentially arranged in a direction away from the first outcoupling sub-region 131, and the efficiency modulation functions of the at least two second outcoupling blocks 134 are progressively increased in the direction away from the first outcoupling sub-region 131. The efficiency modulation function of the second outcoupling blocks 134 refers to the function of the second outcoupling blocks 134 in modulating the diffraction efficiency of light. The progressive trend of the efficiency modulation functions of the at least two second outcoupling blocks 134 in the direction away from the first outcoupling sub-region 131 means that the function of the at least two second outcoupling blocks 134 in modulating the diffraction efficiency of light is increasingly stronger.

[0060] In this embodiment, the second outcoupling sub-region 133 located on one side of the first outcoupling sub-region 131 includes six second outcoupling blocks 134, each of which has a different characteristic structure and optical coupling performance. It should be noted that the number of second outcoupling blocks 134 in the diffractive optical waveguide of the present invention is not limited to this.

[0061] The diffraction optical waveguide 100 of this embodiment can reasonably distribute the diffraction energy per unit area by performing efficiency partitioning on the first sub-coupling area 131 and the second sub-coupling area 133, thereby balancing the diffraction efficiency at different positions within the outcoupling area 130, thereby improving the brightness uniformity of different observation images within the eye box range.

[0062] Based on the aforementioned embodiment, there are two second outcoupling sub-regions 133, and the two second outcoupling sub-regions 133 are symmetrically distributed with respect to the first outcoupling sub-region 131. It should be noted that the two second outcoupling sub-regions 133 may also be asymmetrically distributed, and the specific structure may be set according to the position of the coupling-in region 120.

[0063] Based on the foregoing embodiment, the width of the first outcoupling block 132 along the first direction perpendicular to the first direction (i.e., the y direction or the opposite direction of the y direction in FIG. 2 ) is not less than the width of the light spot entering the incoupling region 120, and the length of the first outcoupling block 132 along the first direction is obtained based on a preset cutoff efficiency threshold of the image light within the first outcoupling block 132.

[0064] Based on the above embodiment, the lengths of the at least two first outcoupling blocks 132 along the first direction decrease gradually. Of course, in the diffractive optical waveguide of the present invention, the lengths of the at least two first outcoupling blocks 132 along the first direction can also be the same.

[0065] Based on the above embodiment, please also refer to FIG3 . The length of the first outcoupling block 132 along the first direction (i.e., the x direction in FIG3 ) is n*d, where n is the number of total reflections, and is obtained based on the following steps:

[0066] S10. A plurality of grating structures are provided in the first outcoupling block 132. A transmission efficiency of an initial grating structure to an adjacent grating structure along a direction perpendicular to the first direction is defined as a. A transmission efficiency of the initial grating structure to an adjacent grating structure along the first direction is defined as b.

[0067] S20, the transmission efficiency of the image light in the first outcoupling block 132 along the first direction perpendicular to the nth total reflection is a*b n-1 The transmission efficiency of the image light along the first direction during the nth total reflection in the first outcoupling block 132 is b n , the cutoff efficiency threshold of the image light in the first outcoupling block 132 is preset to ε, when the efficiency of the nth transmission is a*b n-1 <a*ε, the first decoupling block 132 is terminated. At this time, the length of the first decoupling block 132 along the first direction is n*d.

[0068] In step S20, d is the total reflection point spacing, which is calculated based on formula (I):

[0069] d=t*tan(arcsin(λ / p / n0))*2(I);

[0070] In formula (I), t is the thickness of the waveguide substrate 110, λ is the incident wavelength, p is the grating period, and n0 is the waveguide refractive index.

[0071] In the above steps, the first outcoupling block 132 refers to any first outcoupling block 132 in the first sub-outcoupling region 131. The actual length of the first outcoupling block 132 along the first direction can be slightly greater than or slightly less than the specific value of n*d. After the length of a first outcoupling block 132 along the first direction is obtained based on the above steps, the method for calculating the length of an adjacent first outcoupling block 132 along the first direction is equivalent to the above principle.

[0072] Based on the foregoing embodiment, the width of the second outcoupling block 134 along the direction perpendicular to the first direction is obtained based on a preset cutoff efficiency threshold of the image light in the second outcoupling block 134, and the length of the second outcoupling block 134 along the first direction is equal to the length of the first sub-outcoupling region 131 along the first direction.

[0073] Based on the aforementioned embodiment, in a direction perpendicular to the first direction, the widths of the at least two second outcoupling blocks 134 decrease gradually along a direction away from the first outcoupling sub-region 131. Of course, in the diffractive optical waveguide of the present invention, in a direction perpendicular to the first direction, the widths of the at least two second outcoupling blocks 134 along a direction away from the first outcoupling sub-region 131 may also be the same.

[0074] Based on the above embodiment, please refer to FIG4 . The width of the second outcoupling block 134 along the first direction perpendicular to the first direction (i.e., the y direction or the opposite direction of the y direction in FIG4 ) is n*d, where n is the number of total reflections, and is obtained based on the following steps:

[0075] S30, a plurality of grating structures are provided in the second outcoupling block 134, a transmission efficiency of an initial grating structure to an adjacent grating structure along a direction perpendicular to the first direction is defined as a, and a transmission efficiency of the initial grating structure to an adjacent grating structure along the first direction is defined as c;

[0076] S40, the transmission efficiency of the image light in the nth total reflection in the second outcoupling block 134 along the first direction perpendicular to the first direction is a*c n-1 The transmission efficiency of the image light along the first direction during the nth total reflection in the second outcoupling block 134 is c n , the cutoff efficiency threshold of the image light in the second outcoupling block 134 is preset to ε, when the efficiency of the nth transmission is a*b n-1 When ε<a*ε, the second outcoupling block 134 is terminated. At this time, the width of the second outcoupling block 134 along the direction perpendicular to the first direction is n*d.

[0077] In step S20, d is the total reflection point spacing, and is calculated based on formula (II): d = t*tan(arcsin(λ / p / n0))*2*sin(60°) (II);

[0078] In formula (II), t is the thickness of the waveguide substrate 110, λ is the incident wavelength, p is the grating period, and n0 is the waveguide refractive index.

[0079] In the above steps, the second outcoupling block 134 refers to any second outcoupling block 134 in the second sub-outcoupling region 133. The actual width of the second outcoupling block 134 along the direction perpendicular to the first direction may be slightly greater than or slightly less than the specific value of n*d. After the width of a particular second outcoupling block 134 along the direction perpendicular to the first direction is obtained based on the above steps, the method for calculating the width of an adjacent second outcoupling block 134 along the direction perpendicular to the first direction is equivalent to the above principle.

[0080] The diffraction optical waveguide using the technical solution of the present invention can reasonably distribute the diffraction energy per unit area by zoning the efficiency of the first sub-coupling area and the second sub-coupling area respectively, and balance the diffraction efficiency at different positions in the outcoupling area, thereby improving the brightness uniformity of different observation images within the eye box range, which is conducive to wide application.

[0081] Furthermore, the design of the diffraction optical waveguide of the present invention can perform efficiency partitioning on the entire outcoupling area, or can perform efficiency partitioning on only part of the outcoupling area, and the specific configuration can be made according to actual needs.

[0082] Furthermore, the diffractive optical waveguide of the present invention can be fabricated using several different fabrication methods.

[0083] Referring to FIG5 , the method for preparing a diffractive optical waveguide according to the first embodiment of the present invention includes the following steps:

[0084] Step 1: First, two beams of light (in the direction of the arrows in FIG5 ) are used to interfere with each other to expose the surface of the waveguide substrate 110 coated with the photosensitive adhesive 140 , accumulating the exposure energy to initially form a uniform interference energy surface on the entire outcoupling area.

[0085] Step 2: Set the layout of each partition of the coupling block based on theoretical calculations and simulations.

[0086] Step 3: Establish a mapping model between structural parameters and lithography parameters, and determine the stereolithography parameters corresponding to each region according to the distribution of the outcoupling block 150 (which may be the first outcoupling block or the second outcoupling block mentioned above).

[0087] Step 4: Perform regional stereolithography to superimpose stereolithography light field energy in the photosensitive resin 140 , with different outcoupling blocks depositing different energies.

[0088] Step 5: Develop in a special developer. Within the same developing time, areas with different energy accumulation form structural surface types with different parameters.

[0089] Referring to FIG6 , a method for preparing a diffractive optical waveguide according to a second embodiment of the present invention includes the following steps:

[0090] Step 1: Setting the layout of each partition of the outcoupling block 150 (which may be the first outcoupling block or the second outcoupling block mentioned above) according to theoretical calculations and simulations.

[0091] Step 2: Establish a mapping model between the decoupling block area layout and lithography parameters, and determine the corresponding stereolithography parameters for each area based on the decoupling block distribution.

[0092] Step 3: Perform regionalized stereolithography to accumulate stereolithography light field energy in the photosensitive resin 140 , with different outcoupling blocks having different accumulated energies.

[0093] Step 4: Expose the surface of the waveguide substrate 110 coated with the photosensitive adhesive 140 by means of interference of two beams of light, accumulate exposure energy, and superimpose a uniform interference energy surface on the entire outcoupling area.

[0094] Step 5: Develop in a special developer. Within the same developing time, areas with different energy accumulation form structural surface types with different parameters.

[0095] Referring to FIG. 7 , a method for preparing a diffractive optical waveguide according to a third embodiment of the present invention includes the following steps:

[0096] Step 1: Setting the layout of each partition of the outcoupling block 150 (which may be the first outcoupling block or the second outcoupling block mentioned above) according to theoretical calculations and simulations.

[0097] Step 2: Establish a mapping model between each partition and the interference exposure dose, that is, each partition has a corresponding exposure time.

[0098] Step 3: Expose the surface of the substrate coated with photosensitive adhesive by interfering two beams of light, accumulate exposure energy, and superimpose the interference energy surface in the outcoupling area.

[0099] However, it should be noted that according to the exposure time corresponding to different coupling blocks 150, aperture control is performed, and the aperture 160 can be hollow or have adjustable transmittance for the exposure light source; the exposure dose of different coupling blocks 150 is precisely controlled by controlling the position, size or transmittance of the aperture 160.

[0100] Please refer to Figure 8, which shows the design of an aperture-type exposure in one embodiment. The coupling blocks 151, 152, 153, and 154 in Figure 8 are different coupling blocks, which means that the exposure doses in these four areas are different. It can be seen that the hollow aperture 170 shown in Figure 7 is used for displacement control, or apertures 160 with different transmittances are used for full-frame precise exposure.

[0101] The preparation methods of the diffraction optical waveguides of the above-mentioned embodiments are simple, and the prepared diffraction optical waveguides can partition the outcoupling area into efficiency zones, thereby rationally distributing the diffraction energy per unit area and balancing the diffraction efficiency at different positions within the outcoupling area, thereby improving the brightness uniformity of different observation images within the eye box range, which is conducive to wide application.

[0102] A display module according to one embodiment includes any of the aforementioned diffractive optical waveguides. Furthermore, the display module is a heads-up display module or an augmented reality wearable display module. The augmented reality wearable display module may be an augmented reality near-eye display module, etc.

[0103] Referring to FIG9 , a head-up display module 200 according to one embodiment includes a diffractive optical waveguide 100 according to any of the aforementioned embodiments. A light source assembly emits light into the diffractive optical waveguide 100. The diffractive optical waveguide 100 couples the light along the direction of the arrow in FIG9 , transmits it through the pupil expansion, and then couples it outward onto the vehicle's windshield 220. The light is then reflected off the windshield 220 and enters the human eye, where it is imaged. Because the head-up display module 200 is installed in a vehicle, the imaging light from the head-up display module 200 is reflected off the vehicle's windshield 220. Since the windshield 220 is transparent, real-world information can be observed. By reflecting the imaging light off the windshield 220, the imaging surface of the head-up display module 200 overlaps with the real-world information, allowing users to view information on the dashboard without having to lower their heads, thus improving convenience. Furthermore, the head-up display module of the present invention offers the advantages of high transmission efficiency and excellent imaging quality, allowing users to more clearly perceive the information displayed on the head-up display module, significantly increasing user satisfaction.

[0104] Referring to FIG. 10 , an augmented reality wearable display module 300 according to one embodiment includes the diffractive optical waveguide 100 according to any of the aforementioned embodiments, and the diffractive optical waveguide 100 includes an outcoupling region 130. The augmented reality wearable display module 300 according to this embodiment is an augmented reality near-eye display module, specifically AR glasses. Of course, the augmented reality wearable display module 300 is not limited thereto and may also be in other forms, such as a helmet.

[0105] Using the augmented reality wearable display module 300 of this embodiment, image light is emitted in the direction of the arrow in Figure 10 through the outcoupling region 130 of the diffractive light waveguide 100 and is received by the human eye. Due to the transparent nature of the diffractive light waveguide, the human eye can observe the virtual image in real space and achieve fusion. The density-graded diffractive light waveguide of the present invention can achieve balanced energy emission within the eye box corresponding to the outcoupling region, thereby improving the display quality of the augmented reality wearable display module.

[0106] The display module of the technical solution of the present invention includes any of the above-mentioned diffraction light waveguides, which can reasonably distribute the diffraction energy per unit area by performing efficiency partitioning on the first sub-coupling area and the second sub-coupling area respectively, and balance the diffraction efficiency at different positions in the out-coupling area, thereby improving the brightness uniformity of different observation images within the eye box range, which is conducive to wide application.

[0107] With reference to the above implementation content, in order to make the technical solution of this application more specific, clear and easy to understand, the technical solution of this application is now given as an example. However, it should be noted that the content to be protected by this application is not limited to the following Example 1 and Example 2.

[0108] Example 1

[0109] Referring to FIG. 11 , the diffractive optical waveguide 400 of Example 1 includes a waveguide substrate 410, which includes an incoupling region 420 and an outcoupling region 430 located on one side of the incoupling region 420. The direction from the incoupling region 420 toward the outcoupling region 430 is a first direction (i.e., the x-direction in FIG. 11 ). The outcoupling region 430 includes a first outcoupling sub-region 440 and two second outcoupling sub-regions 450 located on either side of the first outcoupling sub-region 440, respectively. The two second outcoupling sub-regions 450 are symmetrically distributed about the first outcoupling sub-region 440.

[0110] The first sub-outcoupling region 440 includes three first outcoupling blocks 441, 442, and 443 arranged sequentially along a first direction. The width of the first outcoupling blocks 441, 442, and 443 along a direction perpendicular to the first direction (i.e., the y direction or the direction opposite to the y direction in FIG. 11 ) and the length along the first direction are both no less than the width of the light spot entering the incoupling region 420. The efficiency modulation functions of the three first outcoupling blocks 441, 442, and 443 show a progressive trend along the first direction, and the lengths of the three first outcoupling blocks 441, 442, and 443 along the first direction decrease.

[0111] In which, in a direction perpendicular to the first direction (i.e., the y direction or the opposite direction of the y direction in Figure 11), the second sub-coupling region 450 includes two second outcoupling blocks 451 and 452 arranged sequentially in a direction away from the first sub-coupling region 440. The efficiency modulation functions of the two second outcoupling blocks 451 and 452 show a progressive trend in the direction away from the first sub-coupling region 440, and in a direction perpendicular to the first direction, the widths of the two second outcoupling blocks 451 and 452 decrease in the direction away from the first sub-coupling region 440.

[0112] A simulation of the diffractive optical waveguide 400 of Example 1 was conducted, assuming an incident beam diameter of 9.5 mm. The first decoupling block 441 had a period of 440 nm, a depth of 50 nm, and a duty cycle of 0.5. The first decoupling block 442 had a period of 440 nm, a depth of 100 nm, and a duty cycle of 0.5. The first decoupling block 443 had a period of 440 nm, a depth of 200 nm, and a duty cycle of 0.5. The second decoupling block 451 had a period of 440 nm, a depth of 150 nm, and a duty cycle of 0.5. The second decoupling block 452 had a period of 440 nm, a depth of 200 nm, and a duty cycle of 0.5. The specific light intensity of the decoupling region 430 is shown in FIG12 . As can be seen from FIG12 , the diffractive optical waveguide 400 of Example 1 significantly improves the uniformity of the entire decoupling region, while also reducing the difference between the maximum and minimum values ​​to a certain extent.

[0113] Example 2

[0114] Referring to FIG. 13 , the diffractive optical waveguide 500 of Example 2 includes a waveguide substrate 510, which includes an incoupling region 520 and an outcoupling region 530 located on one side of the incoupling region 520. The direction from the incoupling region 520 toward the outcoupling region 530 is a first direction (i.e., the x-direction in FIG. 13 ). The outcoupling region 530 includes a first sub-outcoupling region 540 and two second sub-outcoupling regions 550 located on either side of the first sub-outcoupling region 540, respectively. The two second sub-outcoupling regions 550 are symmetrically distributed about the first sub-outcoupling region 540.

[0115] The first sub-outcoupling region 540 includes three first outcoupling blocks 541, 542, 543, and 544 arranged sequentially along a first direction. The width of the first outcoupling blocks 541, 542, 543, and 544 along the first direction perpendicular to the first direction (i.e., the y direction or the opposite direction of the y direction in FIG. 13 ) and the length along the first direction are both no less than the width of the light spot entering the incoupling region 520. The efficiency modulation functions of the three first outcoupling blocks 541, 542, 543, and 544 show a progressive trend along the first direction, and the lengths of the three first outcoupling blocks 541, 542, 543, and 544 along the first direction decrease.

[0116] In which, in a direction perpendicular to the first direction (i.e., the y direction in FIG. 13 or the opposite direction of the y direction), the second sub-coupling region 550 includes seven second outcoupling blocks 551, 552, 553, 554, 555, 556, and 557 sequentially arranged in a direction away from the first sub-coupling region 540. The efficiency modulation functions of the seven second outcoupling blocks 551, 552, 553, 554, 555, 556, and 557 show a progressive trend in the direction away from the first sub-coupling region 540, and in a direction perpendicular to the first direction, the widths of the seven second outcoupling blocks 551, 552, 553, 554, 555, 556, and 557 decrease in the direction away from the first sub-coupling region 540.

[0117] The diffraction optical waveguide 500 of Example 2 was simulated, with the incident beam diameter set to 9.5 mm and the incident angle set to 0 degrees. The parameters of each outcoupling block are shown in Table 1.

[0118] Table 1 Structural parameters of the diffraction waveguide of Example 2 at incident angles of 0 degrees, -5 degrees, and 5 degrees

[0119] Figures 14 to 16 show the light intensities of the diffractive optical waveguide of Example 2 at incident angles of 0, -5, and 5 degrees, respectively. As can be seen from Figures 14 to 16, when the incident angles are 0, -5, and 5 degrees, the output efficiency in the outcoupling region is relatively uniform, with no significant intensity variation from the end closest to the incoupling region to the end farthest from the incoupling region.

[0120] Comparative Example 1

[0121] Referring to FIG. 17 , the diffractive optical waveguide 200′ of Comparative Example 1 includes a waveguide substrate 210′, which includes an incoupling region 220′ and an outcoupling region 230′. Neither the incoupling region 220′ nor the outcoupling region 230′ is partitioned in the x- and y-directions. That is, the nanostructures within the entire outcoupling region 230′ are covered with structures having the same optical modulation characteristics. According to the structure shown in FIG. 17 , when the incoupling region 220′ receives incident light, the incident light is coupled into the waveguide substrate 210′ ​​due to the light coupling characteristics of the nanostructures in the incoupling region 220′. The light is then transmitted to the outcoupling region 230′, where it undergoes pupil expansion and is then emitted by the nanostructures in the outcoupling region 230′.

[0122] In the diffraction light waveguide 200' of comparative example 1, the coupling-in region 220' adopts a one-dimensional grating, and the coupling-out region 230' adopts a two-dimensional lattice structure. The period of the one-dimensional grating and the two-dimensional lattice are both set to 400nm, the depth is set to 200nm, and the duty cycle is set to 0.5. Based on the ray tracing algorithm, a light emission simulation diagram as shown in Figure 18 is obtained. It can be seen that in the process of light transmission in the coupling-out region 230', the number of outgoing light rays gradually decreases, the light energy representing the exit pupil gradually decreases, and the overall energy emission of the coupling-out region 230' is seriously uneven. The light intensity simulation shown in Figure 18 is the result of the coupling-out region 230' not being changed to adapt to the uniformity, and the result is not ideal. The light intensity distribution of the entire coupling-out region 230' is seriously uneven, which will inevitably bring a very poor display experience.

[0123] Comparative Example 2

[0124] Referring to FIG. 19 , a diffractive optical waveguide 300′ of Comparative Example 2 includes a waveguide substrate 310′, which includes an incoupling region 320′ and an outcoupling region 330′. The outcoupling region 330′ includes a first outcoupling block 331′, a second outcoupling block 332′, and a third outcoupling block 333′ arranged sequentially along the x-direction. The first outcoupling block 331′, the second outcoupling block 332′, and the third outcoupling block 333′ have different optical modulation efficiency characteristics, meaning that the light energy utilization rate of the first outcoupling block 331′ is lower than that of the second outcoupling block 332′, which is lower than that of the third outcoupling block 332′.

[0125] In the diffractive optical waveguide 300' of Comparative Example 2, the coupling-in region 320' employs a one-dimensional grating, and the coupling-out region 330' employs a two-dimensional lattice structure. The period of the nanostructure in the first coupling-out region 331' is set to 440 nm, the depth is set to 50 nm, and the duty cycle is set to 0.5. The nanostructure in the second coupling-out region 332' is set to 440 nm, the depth is set to 100 nm, and the duty cycle is set to 0.5. The nanostructure in the third coupling-out region 333' is set to 440 nm, the depth is set to 200 nm, and the duty cycle is set to 0.5. Based on a ray tracing algorithm, a light emission simulation diagram as shown in Figure 20 is obtained. As can be seen from Figure 20, the energy distribution of the outgoing light during the light transmission process in the coupling-out region 330' is significantly improved compared to the results of the diffractive optical waveguide of Comparative Example 1. The uniformity of the eyebox area corresponding to the coupling-out region 330' is improved, but due to the single distribution design, there is still a clear distinction between bright and dark areas, indicating that the uniformity of the entire image is still insufficient.

[0126] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0127] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A diffractive optical waveguide, characterized in that: The diffraction light waveguide comprises a waveguide substrate, wherein the waveguide substrate comprises an incoupling region and an outcoupling region located at one side of the incoupling region, wherein the incoupling region is used to couple image light into the waveguide substrate, and the outcoupling region is used to couple out the image light conducted in the waveguide substrate; The direction from the coupling-in region to the coupling-out region is a first direction, the coupling-out region includes a first sub-coupling region and a second sub-coupling region, the first sub-coupling region is arranged close to the coupling-in region, and the second sub-coupling region is arranged away from the coupling-in region along a direction perpendicular to the first direction; The first sub-coupling region includes at least two first coupling blocks arranged in sequence along the first direction, and the efficiency modulation functions of the at least two first coupling blocks are in a progressive trend along the first direction; In a direction perpendicular to the first direction, the second sub-coupling region includes at least two second outcoupling blocks arranged in sequence along a direction away from the first sub-coupling region, and the efficiency modulation functions of the at least two second outcoupling blocks show a progressive trend along the direction away from the first sub-coupling region.

2. The diffractive optical waveguide according to claim 1, characterized in that: The number of the second sub-coupling regions is two, and the two second sub-coupling regions are symmetrically distributed with respect to the first sub-coupling region.

3. The diffractive optical waveguide according to claim 1 or 2, characterized in that: The width of the first outcoupling block along the first direction perpendicular to the first direction is not less than the width of the light spot entering the coupling-in region, and the length of the first outcoupling block along the first direction is obtained based on a preset cutoff efficiency threshold of the image light in the first outcoupling block.

4. The diffractive optical waveguide according to claim 3, characterized in that: The lengths of at least two of the first outcoupling blocks along the first direction decrease gradually.

5. The diffractive optical waveguide according to claim 3, characterized in that: The length of the first outcoupling block along the first direction is n*d, where n is the number of total reflections, and is obtained based on the following steps: A plurality of grating structures are provided in the first outcoupling block, a transmission efficiency of an initial grating structure to an adjacent grating structure along a direction perpendicular to the first direction is defined as a, and a transmission efficiency of an initial grating structure to an adjacent grating structure along the first direction is defined as b; and The transmission efficiency of the image light in the first outcoupling block at the nth total reflection along the first direction perpendicular to the first direction is a*b n-1 The transmission efficiency of the image light along the first direction at the nth total reflection in the first outcoupling block is b n , the cutoff efficiency threshold of the image light in the first outcoupling block is preset to ε, when the efficiency of the nth transmission is a*b n-1 <a*ε, the first coupling-out block is terminated, and at this time, the length of the first coupling-out block along the first direction is n*d; Where d is the total reflection point spacing, and is calculated based on formula (I): d=t*tan(arcsin(λ / p / n0))*2 (I); In formula (I), t is the thickness of the waveguide substrate, λ is the incident wavelength, p is the grating period, and n0 is the waveguide refractive index.

6. The diffractive optical waveguide according to claim 1 or 2, characterized in that: The width of the second outcoupling block along the first direction perpendicular to the first direction is obtained based on a preset cutoff efficiency threshold of the image light in the second outcoupling block, and the length of the second outcoupling block along the first direction is equal to the length of the first sub-outcoupling region along the first direction.

7. The diffractive optical waveguide according to claim 6, characterized in that: In a direction perpendicular to the first direction, widths of at least two of the second outcoupling blocks decrease gradually in a direction away from the first sub-outcoupling region.

8. The diffractive optical waveguide according to claim 6, characterized in that: The width of the second outcoupling block along the direction perpendicular to the first direction is n*d, where n is the number of total reflections, and is obtained based on the following steps: A plurality of grating structures are provided in the second outcoupling block, a transmission efficiency of an initial grating structure to an adjacent grating structure along a direction perpendicular to the first direction is defined as a, and a transmission efficiency of an initial grating structure to an adjacent grating structure along the first direction is defined as c; and The transmission efficiency of the image light in the second outcoupling block at the nth total reflection along the first direction perpendicular to the first direction is a*c n-1 The transmission efficiency of the image light along the first direction at the nth total reflection in the second outcoupling block is c n , the cutoff efficiency threshold of the image light in the second outcoupling block is preset to ε, when the efficiency of the nth transmission is a*b n-1 When a*ε is less than, the second coupling block is terminated, and at this time, the width of the second coupling block along the direction perpendicular to the first direction is n*d; Where d is the total reflection point spacing, and is calculated based on formula (II): d=t*tan(arcsin(λ / p / n0))*2*sin(60°) (II); In formula (II), t is the thickness of the waveguide substrate, λ is the incident wavelength, p is the grating period, and n0 is the waveguide refractive index.

9. A display module, characterized in that: The diffractive optical waveguide comprises the diffractive optical waveguide according to any one of claims 1 to 8.

10. The display module according to claim 9, characterized in that: The display module is a head-up display module or an augmented reality wearable display module.

Images