Diffraction optical waveguide and display module

Abstract

The invention relates to a diffraction optical waveguide and a display module. The diffractive optical waveguide comprises a waveguide substrate, and the waveguide substrate comprises a coupling-in area and a coupling-out area; the direction from the coupling-in area to the coupling-out area is a first direction, and the coupling-out area comprises a first sub-coupling-out area and a second sub-coupling-out area; the first sub coupling-out area comprises at least two first coupling-out blocks which are sequentially arranged along the first direction, and the efficiency modulation functions of the at least two first coupling-out blocks present a progressive trend along the first direction; in the direction perpendicular to the first direction, the second sub-coupling-out area comprises at least two second coupling-out blocks which are sequentially arranged in the direction away from the first sub-coupling-out area, and the efficiency modulation functions of the at least two second coupling-out blocks are in a progressive trend in the direction away from the first sub-coupling-out area. According to the diffraction optical waveguide provided by the invention, the first sub-coupling-out region and the second sub-coupling-out region can be efficiently partitioned, so that the brightness uniformity of different observation images in an eye box range is improved.

Description

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] Augmented reality (AR) display is a display in which the observer can view images or data superimposed on the real environment while viewing real objects in the outside world. Therefore, it is widely used in various fields, especially in the military and consumer fields. The reason is that augmented reality display provides the function of barrier-free real-time interaction with the real environment that traditional display devices do not have, bringing users a new visual experience. However, the primary problem in augmented reality display is how to reduce the size and weight of the display device, and provide sufficient brightness and field of view to achieve lightweight equipment and high spatial resolution and high angular resolution of augmented reality fusion presentation effect.

[0003] Since the development of augmented reality display optical technology, the main solutions are roughly divided into coaxial side-view prism solution, array semi-transparent film waveguide solution, free-form surface solution, diffraction optical waveguide solution, etc. Different solutions have different display performance. The current in-vehicle head-up display mainly adopts the design of free-form surface, and its module volume is huge; many giants in the field of near-eye display, including Microsoft, Meta, Apple, Google, Snap, etc., all adopt the more mainstream diffraction optical waveguide technology solution. The diffraction optical waveguide uses the diffraction characteristics of the grating to design the "optical path", allowing light to propagate on the designed path and guide the light emitted by the micro-projection system into the human eye. The main advantage of this type of solution is small size and thinness, and the augmented reality display module based on diffraction optical waveguide continues the advantage of ultra-small size, which is more conducive to the integration of wearable displays and the front installation of automotive head-up displays.

[0004] The traditional diffraction waveguide solution adopts the coupling-in-turn-out light transmission design and realizes the large eye box display through the theoretical method of diffraction pupil expansion. Figure 1 As shown, a conventional diffraction optical waveguide 100' comprises a waveguide substrate 110', wherein the waveguide substrate 110' comprises an incoupling region 120' and an outcoupling region 130'. The entire outcoupling region 130' of the diffraction optical waveguide 100' is a grating structure with the same parameters. Figure 1When the light is coupled from the coupling-in region 120' into the waveguide substrate 110' in the direction of the middle arrow and is conducted in the waveguide substrate 110', the light energy that passes through the coupling-out region 130' for the first time and is diffracted by the grating structure of the coupling-out region 120' is the strongest. After that, the energy of each outgoing light gradually weakens. This is because the coupling-out region 130' is only a grating structure with the same diffraction efficiency, and after each diffraction, the total energy that can continue to be conducted will inevitably decay, and the same diffraction efficiency will inevitably lead to a decrease in the next outgoing energy, which will cause obvious image brightness and darkness due to uneven energy within the eye box range when the human eye moves through the waveguide. Therefore, in the part of the conventional diffraction optical waveguide for the coupling-out region, due to the uneven control of the diffraction efficiency, it often leads to the problem of uneven brightness of different observed images within the eye box range. Summary of the invention

[0005] Based on this, it is necessary to provide a diffraction optical waveguide and display module to solve the problem of how to improve the brightness uniformity of different observation images within the eye box.

[0006] A diffractive optical waveguide, comprising a waveguide substrate, the waveguide substrate comprising 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 the image light conducted in the waveguide substrate;

[0007] 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;

[0008] 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;

[0009] 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.

[0010] The diffraction optical waveguide using the technical solution of the present invention 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 coupling area, thereby improving the brightness uniformity of different observation images within the eye box range, which is conducive to wide application.

[0011] In a feasible implementation manner, 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.

[0012] 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.

[0013] In a feasible implementation, lengths of at least two of the first outcoupling blocks along the first direction decrease gradually.

[0014] 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:

[0015] 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

[0016] 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;

[0017] Where d is the total reflection point spacing, and is calculated based on formula (I):

[0018] d = t*tan(arcsin(λ / p / n 0 ))*2(I);

[0019] In formula (I), t is the thickness of the waveguide substrate, λ is the incident wavelength, p is the grating period, and n is 0 is the waveguide refractive index.

[0020] 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.

[0021] 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.

[0022] 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:

[0023] 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

[0024] 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;

[0025] Where d is the total reflection point spacing, and is calculated based on formula (II):

[0026] d = t*tan(arcsin(λ / p / n 0 ))*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 n is 0 is the waveguide refractive index.

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

[0029] The display module of the technical solution of the present invention includes any of the above-mentioned diffraction optical waveguides, and 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 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] Figure 1A schematic diagram of light transmission of a traditional diffraction optical waveguide;

[0032] Figure 2 Schematic diagram of the structure of a diffractive optical waveguide according to one embodiment of the present invention;

[0033] Figure 3 A schematic diagram of the definition of a first outcoupling block in a diffractive optical waveguide according to an embodiment of the present invention;

[0034] Figure 4 A schematic diagram of the definition of a second outcoupling block in a diffractive optical waveguide according to an embodiment of the present invention;

[0035] Figure 5 Schematic diagram of preparation of a diffractive optical waveguide according to the first embodiment of the present invention;

[0036] Figure 6 Schematic diagram of preparation of a diffractive optical waveguide according to a second embodiment of the present invention;

[0037] Figure 7 Schematic diagram of preparation of a diffractive optical waveguide according to a third embodiment of the present invention;

[0038] Figure 8 Schematic diagram of the design of aperture exposure in the process of preparing the diffractive optical waveguide according to the third embodiment of the present invention;

[0039] Fig. 9 is a schematic diagram of a head-up display module according to an embodiment of the present invention;

[0040] Fig.10 A schematic diagram of an augmented reality wearable display module according to an embodiment of the present invention;

[0041] Fig.11 Schematic diagram of the structure of the diffraction optical waveguide according to Embodiment 1 of the present invention;

[0042] Fig.12 This is a simulation diagram of light emission in the outcoupling area of ​​the diffraction optical waveguide according to Example 1 of the present invention;

[0043] Fig.13 Schematic diagram of the structure of the diffraction optical waveguide according to Embodiment 2 of the present invention;

[0044] Fig.14 This is a simulation diagram of light emission from the outcoupling region of the diffraction light waveguide of Example 2 of the present invention at 0 degree incidence;

[0045] Fig.15 This is a simulation diagram of light emission from the outcoupling region of the diffraction light waveguide of Example 2 of the present invention at -5 degrees of incidence;

[0046] Fig.16 This is a simulation diagram of light emission from the outcoupling region of the diffraction light waveguide of Example 2 of the present invention at 5 degrees of incidence;

[0047] Fig.17 Schematic diagram of the structure of the diffraction optical waveguide of Comparative Example 1;

[0048] Fig.18 This is a simulation diagram of light emission from the outcoupling area of ​​the diffraction optical waveguide of Comparative Example 1;

[0049] Fig.19 Schematic diagram of the structure of the diffraction optical waveguide of Comparative Example 2;

[0050] Fig. 20 This is a simulation diagram of light emission from the outcoupling area of ​​the diffraction optical waveguide of comparative example 2. DETAILED DESCRIPTION

[0051] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by 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 on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. 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 those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0054] See also Figure 2 A diffraction optical waveguide 100 according to an embodiment of the present invention includes a waveguide substrate 110, and the waveguide substrate 110 includes a coupling-in region 120 and a coupling-out region 130 located on one side of the coupling-in region 120. The coupling-in region 120 is used to couple the image light into the waveguide substrate 110, and the coupling-out region 130 is used to couple out the image light conducted in the waveguide substrate 110, specifically, the emission and conduction functions.

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

[0056] The direction from the in-coupling region 120 to the out-coupling region 130 is the first direction (i.e. Figure 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 arranged close to the coupling region 120, and the second sub-outcoupling region 133 is arranged along a direction perpendicular to the first direction (i.e. Figure 2 Specifically, the first sub-coupling region 131 is arranged opposite to the coupling region 120, and the second sub-coupling region 133 is located on one side of the first sub-coupling region 131 perpendicular to the first direction, such as Figure 2 Preferably, the length of the side of the first outcoupling sub-region 131 close to the coupling-in region 120 may be slightly greater than the width of the coupling-in region 120 along the y direction, to ensure that the image light can remain in the first outcoupling sub-region 131 after being transmitted through the coupling-in region 120 .

[0057] The first sub-coupling area 131 includes at least two first coupling blocks 132 arranged in sequence along the first direction, and the efficiency modulation function of the at least two first coupling blocks 132 is progressive along the first direction. The efficiency modulation function of the first coupling block 132 refers to the function of modulating the diffraction efficiency of light possessed by the first coupling block 132, and the efficiency modulation function of the at least two first coupling blocks 132 is progressive along the first direction, which means that the function of modulating the diffraction efficiency of light possessed by the at least two first coupling blocks 132 is getting stronger and 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 diffractive optical waveguide of the present invention, the number of first outcoupling blocks 132 is not limited thereto.

[0059] In the 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 block 134 refers to the function of modulating the diffraction efficiency of light possessed by the second outcoupling block 134, 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, which means that the function of modulating the diffraction efficiency of light possessed by the at least two second outcoupling blocks 134 is increasingly stronger.

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

[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 respectively, and balance the diffraction efficiency at different positions in the out-coupling area 130, thereby improving the brightness uniformity of different observation images within the eye box range.

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

[0063] On the basis of the above-mentioned implementation, the first coupling block 132 is perpendicular to the first direction (ie Figure 2 The width of the first coupling block 132 along the first direction is obtained based on a preset cutoff efficiency threshold of the image light in the first coupling block 132.

[0064] Based on the above embodiment, the lengths of 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 at least two first outcoupling blocks 132 along the first direction may also be the same.

[0065] Based on the above implementation methods, please refer to Figure 3 , the first coupling block 132 is along the first direction (ie Figure 3 The length of the x direction 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, 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 b;

[0067] S20, the transmission efficiency of the image light in the first outcoupling block 132 along the direction perpendicular to the first direction is a*b n-1 The transmission efficiency of the image light along the first direction due to the nth total reflection in the first outcoupling block 132 is bn , the cutoff efficiency threshold of the image light in the first coupling block 132 is preset to be ε, when the efficiency of the nth transmission is a*b n-1 <a*ε, the first decoupling block 132 is terminated, and 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 / n 0 ))*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 n 0 is the waveguide refractive index.

[0071] In the above steps, the first coupling block 132 refers to any first coupling block 132 in the first sub-coupling region 131, and the actual length of the first coupling 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 certain first coupling block 132 along the first direction is obtained based on the above steps, the method for calculating the length of adjacent first coupling blocks 132 along the first direction is equivalent to the above principle.

[0072] Based on the foregoing implementation, 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] On the basis of the above-mentioned embodiment, in the direction perpendicular to the first direction, the widths of at least two second outcoupling blocks 134 in the direction away from the first outcoupling sub-region 131 decrease gradually. Of course, in the diffractive optical waveguide of the present invention, in the direction perpendicular to the first direction, the widths of at least two second outcoupling blocks 134 in the direction away from the first outcoupling sub-region 131 may also be the same.

[0074] Based on the above implementation methods, please refer to Figure 4 The second coupling block 134 is perpendicular to the first direction (ie Figure 4 The width of the y direction or the opposite direction of the y direction) 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 the initial grating structure to the adjacent grating structure along the direction perpendicular to the first direction is defined as a, and a transmission efficiency of the initial grating structure to the adjacent grating structure along the first direction is defined as c;

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

[0077] In step S20, d is the total reflection point spacing, which is calculated based on formula (II):

[0078] d = t*tan(arcsin(λ / p / n 0 ))*2*sin(60°)(II);

[0079] In formula (II), t is the thickness of the waveguide substrate 110, λ is the incident wavelength, p is the grating period, and n 0 is the waveguide refractive index.

[0080] In the above steps, the second coupling block 134 refers to any second coupling block 134 in the second sub-coupling region 133, and the actual width of the second coupling block 134 along the first direction perpendicular to the first direction can be slightly greater than or slightly less than the specific numerical value of n*d. After a certain second coupling block 134 along the width perpendicular to the first direction is obtained based on the above steps, the method for calculating the width of adjacent second coupling blocks 134 along the first direction perpendicular to the first direction is equal to the above principle.

[0081] The diffraction optical waveguide using the technical solution of the present invention 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 coupling area, thereby improving the brightness uniformity of different observation images within the eye box range, which is conducive to wide application.

[0082] Furthermore, the design of the diffractive optical waveguide of the present invention can partition the efficiency of the entire outcoupling area, or can partition the efficiency of only part of the outcoupling area, which can be specifically configured according to actual needs.

[0083] Furthermore, the diffractive optical waveguide of the present invention can be fabricated using several different fabrication methods.

[0084] See also Figure 5 The method for preparing the diffractive optical waveguide according to the first embodiment of the present invention comprises the following steps:

[0085] Step 1: First pass two beams of light ( Figure 5The surface of the waveguide substrate 110 coated with the photosensitive adhesive 140 is exposed in the manner of interference (in the direction of the light beam irradiated by the middle arrow), and the exposure energy is accumulated to initially form a uniform interference energy surface on the entire surface of the outcoupling area.

[0086] Step 2: Set the layout of each partition of the coupling block according to theoretical calculation and simulation.

[0087] Step three: 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).

[0088] Step 4: Perform regional stereolithography to superimpose stereolithography light field energy in the photosensitive resin 140, and the energy accumulated in different outcoupling blocks is different.

[0089] Step 5: Develop in a special developer. During the same development time, areas with different energy accumulation form structural surfaces with different parameters.

[0090] See also Figure 6 The method for preparing the diffractive optical waveguide according to the second embodiment of the present invention comprises the following steps:

[0091] Step 1: Setting the layout of each partition of the decoupling block 150 (which may be the first decoupling block or the second decoupling block mentioned above) according to theoretical calculation and simulation.

[0092] Step 2: Establish a mapping model between the decoupling block area division layout and lithography parameters, and determine the corresponding stereolithography parameters of each area according to the decoupling block distribution.

[0093] Step 3: Perform regionalized stereolithography to accumulate stereolithography light field energy in the photosensitive resin 140 , and different outcoupling blocks accumulate different energies.

[0094] 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.

[0095] Step 5: Develop in a special developer. During the same development time, areas with different energy accumulation form structural surfaces with different parameters.

[0096] See also Figure 7 The method for preparing a diffractive optical waveguide according to the third embodiment of the present invention comprises the following steps:

[0097] Step 1: Setting the layout of each partition of the decoupling block 150 (which may be the first decoupling block or the second decoupling block mentioned above) according to theoretical calculation and simulation.

[0098] Step 2: Establish a mapping model between each partition and the interference exposure dose, that is, each partition has a corresponding exposure time.

[0099] Step 3: Expose the surface of the substrate coated with photosensitive adhesive by means of interference of two beams of light, accumulate exposure energy, and superimpose the interference energy surface in the outcoupling area.

[0100] 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.

[0101] See also Figure 8 , a design of aperture exposure in one embodiment, Figure 8 The outcoupling blocks 151, 152, 153 and 154 are different outcoupling blocks, which means that the exposure doses in these four areas are different. Figure 7 The hollow aperture 170 shown is used for displacement control, or apertures 160 with different transmittances are used for full-frame precise exposure.

[0102] The preparation method of the diffraction optical waveguide of each of the above-mentioned embodiments is simple in process, and the prepared diffraction optical waveguide can partition the out-coupling area for efficiency, thereby reasonably distributing the diffraction energy per unit area and balancing 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.

[0103] A display module of an embodiment includes any of the above-mentioned diffractive optical waveguides. Further, the display module is a head-up display module or an augmented reality wearable display module. Among them, the augmented reality wearable display module can be an augmented reality near-eye display module, etc.

[0104] See also Fig. 9 A head-up display module 200 of one embodiment includes a diffractive optical waveguide 100 of any of the above embodiments. The light source assembly emits light to the diffractive optical waveguide 100, and the diffractive optical waveguide 100 transmits the light along the Fig. 9The light in the direction of the middle arrow is coupled into the pupil expansion transmission and then coupled out to the windshield 220 of the car, and then reflected by the windshield 220 into the human eye for imaging. Since the head-up display module 200 is arranged in the car, the imaging light of the head-up display module 200 is reflected to the human eye by the windshield 220 of the car, and the windshield 220 is transparent so that information in the real world can be observed. The imaging light is reflected to the windshield 220 by the head-up display module 200, so that the imaging surface of the head-up display module 200 is superimposed with the information in the real world, so that the user can observe the information on the dashboard without lowering his head, thereby improving convenience. At the same time, the head-up display module of the present invention has the advantages of high transmission efficiency and good imaging effect, so that the user can observe the information displayed by the head-up display module more clearly, greatly improving the user's satisfaction.

[0105] See also Fig.10 An augmented reality wearable display module 300 of an embodiment includes the diffractive optical waveguide 100 of any of the above embodiments, and the diffractive optical waveguide 100 includes an outcoupling region 130. The augmented reality wearable display module 300 of 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 can also be in other forms, such as a helmet.

[0106] Using the augmented reality wearable display module 300 of this embodiment, the image light is along Fig.10 The light in the middle arrow direction is emitted through the outcoupling region 130 of the diffractive light waveguide 100 and received by the human eye, and because of the transparent property of the diffractive light waveguide, the human eye can see the virtual image in the real space and achieve fusion. Due to the density gradient diffractive light waveguide of the present invention, the energy can be evenly emitted within the eye box range corresponding to the outcoupling region, thereby improving the display quality of the augmented reality wearable display module.

[0107] The display module of the technical solution of the present invention includes any of the above-mentioned diffraction optical waveguides, and 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 coupling area, thereby improving the brightness uniformity of different observation images within the eye box range, which is conducive to wide application.

[0108] With reference to the above implementation contents, in order to make the technical solution of the present application more specific, clear and easy to understand, the technical solution of the present application is now exemplified. However, it should be noted that the contents to be protected by the present application are not limited to the following Examples 1 and 2.

[0109] Example 1

[0110] See also Fig.11The diffractive optical waveguide 400 of Embodiment 1 includes a waveguide substrate 410, and the waveguide substrate 410 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 to the outcoupling region 430 is a first direction (i.e. Fig.11 The outcoupling region 430 includes a first sub-outcoupling region 440 and two second sub-outcoupling regions 450 located on both sides of the first sub-outcoupling region 440, and the two second sub-outcoupling regions 450 are symmetrically distributed about the first sub-outcoupling region 440.

[0111] The first sub-coupling region 440 includes three first coupling blocks 441, 442 and 443 arranged in sequence along the first direction. The first coupling blocks 441, 442 and 443 are arranged perpendicular to the first direction (i.e. Fig.11 The width of the first coupling block 441, 442 and 443 in the y direction or the opposite direction of the y direction) and the length along the first direction are not less than the width of the light spot entering the coupling region 420, the efficiency modulation functions of the three first coupling blocks 441, 442 and 443 are progressive along the first direction, and the lengths of the three first coupling blocks 441, 442 and 443 along the first direction decrease.

[0112] Among them, in the direction perpendicular to the first direction (i.e. Fig.11 In the y direction or the opposite direction of the y direction), the second sub-coupling region 450 includes two second coupling blocks 451 and 452 which are sequentially arranged in a direction away from the first sub-coupling region 440, and the efficiency modulation functions of the two second coupling blocks 451 and 452 are progressive in a direction away from the first sub-coupling region 440, and in a direction perpendicular to the first direction, the widths of the two second coupling blocks 451 and 452 decrease gradually in a direction away from the first sub-coupling region 440.

[0113] The diffraction optical waveguide 400 of Example 1 is simulated, and the incident light beam diameter is set to 9.5 mm; the period of the first coupling block 441 is 440 nm, the depth is 50 nm, and the duty cycle is 0.5; the period of the first coupling block 442 is 440 nm, the depth is 100 nm, and the duty cycle is 0.5; the period of the first coupling block 443 is 440 nm, the depth is 200 nm, and the duty cycle is 0.5; the period of the second coupling block 451 is 440 nm, the depth is 150 nm, and the duty cycle is 0.5; the period of the second coupling block 452 is 440 nm, the depth is 200 nm, and the duty cycle is 0.5. The specific light intensity of the coupling region 430 is as follows: Fig.12 As shown, from Fig.12 It can be seen that the diffractive optical waveguide 400 of Example 1 can significantly improve the uniformity of the entire out-coupling region, and the difference between the maximum and minimum values ​​is also reduced to a certain extent.

[0114] Example 2

[0115] See also Fig.13 The diffractive optical waveguide 500 of Embodiment 2 includes a waveguide substrate 510, and the waveguide substrate 510 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 to the outcoupling region 530 is a first direction (i.e. Fig.13 The outcoupling region 530 includes a first sub-outcoupling region 540 and two second sub-outcoupling regions 550 respectively located on both sides of the first sub-outcoupling region 540 , and the two second sub-outcoupling regions 550 are symmetrically distributed about the first sub-outcoupling region 540 .

[0116] The first sub-coupling region 540 includes three first coupling blocks 541, 542, 543 and 544 arranged in sequence along the first direction. The first coupling blocks 541, 542, 543 and 544 are arranged along a direction perpendicular to the first direction (i.e. Fig.13 The width of the first coupling block 541, 542, 543 and 544 in the y direction or the opposite direction of the y direction) and the length along the first direction are not less than the width of the light spot entering the coupling region 520, the efficiency modulation functions of the three first coupling blocks 541, 542, 543 and 544 are progressive along the first direction, and the lengths of the three first coupling blocks 541, 542, 543 and 544 along the first direction decrease.

[0117] Among them, in the direction perpendicular to the first direction (i.e. Fig.13 In the y direction or the opposite direction of the y direction), the second sub-coupling area 550 includes seven second coupling blocks 551, 552, 553, 554, 555, 556 and 557 which are sequentially arranged in a direction away from the first sub-coupling area 540, and the efficiency modulation functions of the seven second coupling blocks 551, 552, 553, 554, 555, 556 and 557 are progressive in a direction away from the first sub-coupling area 540, and in a direction perpendicular to the first direction, the widths of the seven second coupling blocks 551, 552, 553, 554, 555, 556 and 557 decrease gradually in a direction away from the first sub-coupling area 540.

[0118] The diffraction optical waveguide 500 of Example 2 is simulated, and the incident light beam diameter is set to 9.5 mm, the incident angle is set to 0 degree, and the parameters of each coupling block are shown in Table 1.

[0119] Table 1 Structural parameters of the diffraction optical waveguide of Example 2 at incident angles of 0 degrees, -5 degrees and 5 degrees

[0120] Coupling block number Period (nm) Depth(nm) Duty Cycle The first coupling block 541 440 30 0.65 The first coupling block 542 440 40 0.65 The first coupling block 543 440 50 0.65 The first coupling block 544 440 70 0.65 The second coupling block 551 440 100 0.4 The second coupling block 552 440 110 0.4 The second coupling block 553 440 130 0.4 The second coupling block 554 440 150 0.4 The second coupling block 555 440 210 0.4 The second coupling block 556 440 210 0.5 The second coupling block 557 440 270 0.6

[0121] The light intensities of the diffraction light waveguide of Example 2 at incident angles of 0 degrees, -5 degrees and 5 degrees are as follows: Figure 14 to Figure 16 As shown. Figure 14 to Figure 16It can be seen that when the incident angles are 0 degrees, -5 degrees and 5 degrees, the output efficiency of the out-coupling area is relatively uniform, and the intensity changes are not obvious from the end close to the coupling area to the end far from the coupling area.

[0122] Comparative Example 1

[0123] See also Fig.17 The diffractive optical waveguide 200' of comparative example 1 includes a waveguide substrate 210', and the waveguide substrate 210' includes an incoupling region 220' and an outcoupling region 230'. The incoupling region 220' and the outcoupling region 230' are not partitioned in the x direction and the y direction, that is, the nanostructures in the entire surface of the outcoupling region 230' are covered with structures with the same optical modulation characteristics. Fig.17 In the structure shown, when the coupling-in region 220' receives incident light, based on the light coupling characteristics of the nanostructure of the coupling-in region 220', the incident light is coupled into the waveguide substrate 210' and transmitted to the coupling-out region 230', where the pupil is expanded and the light is emitted through the nanostructure of the coupling-out region 230'.

[0124] In the diffraction optical 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 is set to 400nm, the depth is set to 200nm, and the duty cycle is set to 0.5. Based on the ray tracing algorithm, it is obtained as follows Fig.18 It can be seen from the light emission simulation diagram that during the light transmission process in the outcoupling area 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 outcoupling area 230' is seriously uneven. Fig.18 The light intensity simulation shown is the result of not changing the outcoupling area 230' to adapt to uniformity, and the result is not ideal. The light intensity distribution of the entire outcoupling area 230' is seriously uneven, which will inevitably bring a poor display experience.

[0125] Comparative Example 2

[0126] See also Fig.19 The diffraction optical waveguide 300' of comparative example 2 includes a waveguide substrate 310', the waveguide substrate 310' includes a coupling-in region 320' and a coupling-out region 330', and the coupling-out region 330' includes a first coupling-out block 331', a second coupling-out block 332' and a third coupling-out block 333' arranged in sequence along the x direction. The optical modulation efficiency characteristics of the first coupling-out block 331', the second coupling-out block 332' and the third coupling-out block 333' are different, which means that the light energy utilization rate of the first coupling-out block 331' is less than that of the second coupling-out block 332' and that of the third coupling-out block 332'.

[0127] In the diffraction optical waveguide 300' of comparative example 2, the coupling-in region 320' adopts a one-dimensional grating, and the coupling-out region 330' adopts a two-dimensional lattice structure; the period of the nanostructure in the first coupling-out block 331' is set to 440nm, the depth is set to 50nm, and the duty cycle is set to 0.5; the nanostructure in the second coupling-out block 332' is set to 440nm, the depth is set to 100nm, and the duty cycle is set to 0.5; the nanostructure in the third coupling-out block 333' is set to 440nm, the depth is set to 200nm, and the duty cycle is set to 0.5. Based on the ray tracing algorithm, it is obtained as follows Fig. 20 The light emission simulation diagram shown in Figure 1 is as follows. Fig. 20 It can be seen that in the light transmission process in the outcoupling area 330', the energy distribution of the outgoing light is significantly improved compared with the result of the diffraction light waveguide in comparative example 1, and the uniformity of the eye box range corresponding to the outcoupling area 330' is improved. However, due to the single distribution design, there is still an obvious difference in light and dark, which means that the uniformity of the entire surface is still not good enough.

[0128] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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.

[0129] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached 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.

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