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, a turning area and a coupling-out area. The direction from the coupling-in area to the turning area is a first direction, the turning area comprises at least two turning blocks which are sequentially arranged along the first direction, and the efficiency modulation functions of the at least two turning blocks present a progressive trend along the first direction; the direction from the turning area to the out-coupling area is a second direction, and the second direction is perpendicular to the first direction; the coupling-out area comprises at least two coupling-out blocks which are sequentially arranged in the second direction, and the efficiency modulation functions of the at least two coupling-out blocks are in a progressive trend in the second direction. By applying the diffraction optical waveguide, efficiency partitioning can be performed on the turning area and the coupling-out area, so that diffraction energy of a unit area is reasonably distributed, diffraction efficiency of different positions in the coupling-out area is balanced, brightness uniformity of different observation images in an eye box range is improved, and wide application is facilitated.

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 function 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. From the release of Google Glass, which swept the world in 2012, to Oculus, which was acquired by Facebook for US$2 billion in 2014, to Microsoft's Hololens in 2016, Magic Leap led by Google, Hololens2 released by Microsoft, AR glasses released by OPPO, and the recently popular AR-HUD, all of them have shown the world the huge application prospects of augmented reality display. 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 a large eye box display through the theoretical method of diffraction pupil expansion. However, in the out-coupling area, due to the uneven control of diffraction efficiency, it often leads to uneven brightness of different observation 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, wherein the waveguide substrate comprises:

[0007] A coupling region, used for coupling image light into the waveguide substrate;

[0008] A turning area, located at one side of the coupling-in area, and used to receive the image light of the coupling-in area and couple and conduct it;

[0009] An outcoupling region, located at one side of the turning region, and used to receive the image light of the turning region and couple the image light out;

[0010] The direction from the coupling region to the turning region is a first direction, the turning region includes at least two turning blocks arranged in sequence along the first direction, and the efficiency modulation functions of at least two turning blocks present a progressive trend along the first direction;

[0011] The direction from the turning area to the coupling-out area is a second direction, and the second direction is perpendicular to the first direction; the coupling-out area includes at least two coupling-out blocks arranged in sequence along the second direction, and the efficiency modulation functions of at least two coupling-out blocks show a progressive trend along the second direction.

[0012] 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 turning area and the out-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.

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

[0014] In a feasible implementation, the lengths of at least two turning blocks along the first direction decrease or are the same.

[0015] In a feasible implementation, the length of the turning 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 arranged in the turning block, and a turning efficiency of an initial grating structure to an adjacent grating structure along the second 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 turning efficiency of the image light along the second direction at the nth total reflection in the turning block is a*b n-1 The transmission efficiency of the image light along the first direction during the nth total reflection in the turning block is b n , the cutoff efficiency threshold of the image light in the turning block is preset to be ε, when the efficiency of the nth transmission is a*b n-1 <a*ε, the turning block is terminated, and at this time, the length of the turning block along the first direction is n*d;

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

[0019] d = t*tan(arcsin(λ / p / n 0 ))*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 n is 0 is the waveguide refractive index.

[0021] In a feasible implementation, the width of the outcoupling block along the second direction is obtained based on a preset cutoff efficiency threshold of the image light in the outcoupling block.

[0022] In a feasible implementation manner, widths of at least two of the decoupling blocks along the second direction decrease or are the same.

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

[0024] A plurality of grating structures are provided in the outcoupling block, a transmission efficiency of an initial grating structure to an adjacent grating structure along the second direction is defined as A, and an outcoupling efficiency of the initial grating structure is defined as B; and

[0025] The transmission efficiency of the image light along the second direction during the nth total reflection in the outcoupling block is A. n , the coupling efficiency is A n-1 *B, the cutoff efficiency threshold of the image light in the coupling block is preset to be ε, when the efficiency A of the nth transmission n *B<ε*B, the coupling-out block is terminated, and at this time, the width of the coupling-out block along the second direction is n*d;

[0026] Where d is the total reflection point spacing, and is calculated based on formula (I):

[0027] d = t*tan(arcsin(λ / p / n 0 ))*2(I);

[0028] 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.

[0029] In a feasible implementation, at least one of the grating period, grating depth and duty cycle of two adjacent turning blocks is different; or

[0030] At least one of the grating period, grating depth and duty cycle of two adjacent outcoupling blocks is different.

[0031] A display module comprises any of the above diffraction light waveguides.

[0032] 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 turning area and the out-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.

[0033] 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

[0034] Figure 1 is a schematic diagram of a diffractive optical waveguide according to an embodiment of the present invention;

[0035] Figure 2 A diagram showing the definition principle of a turning block in a diffractive optical waveguide according to an embodiment of the present invention;

[0036] Figure 3 A diagram showing the definition principle of an outcoupling block in a diffractive optical waveguide according to an embodiment of the present invention;

[0037] Figure 4 is a schematic diagram of a diffractive optical waveguide according to another embodiment of the present invention;

[0038] Figure 5 is a schematic diagram of a diffractive optical waveguide according to another embodiment of the present invention;

[0039] Figure 6 is an intensity diagram of an outgoing light beam of a diffraction light waveguide in the prior art;

[0040] Figure 7 is an intensity diagram of an outgoing light beam of a diffractive light waveguide according to another embodiment of the present invention;

[0041] Figure 8 Schematic diagram of preparation of a diffractive optical waveguide according to the first embodiment of the present invention;

[0042] Fig. 9Schematic diagram of preparing a diffractive optical waveguide according to a second embodiment of the present invention;

[0043] Fig.10 Schematic diagram of preparation of a diffractive optical waveguide according to a third embodiment of the present invention;

[0044] Fig.11 is a schematic diagram of the design of aperture exposure in the process of preparing a diffractive optical waveguide according to the third embodiment of the present invention;

[0045] Fig.12 is a schematic diagram of a head-up display module according to an embodiment of the present invention;

[0046] Fig.13 A schematic diagram of an augmented reality wearable display module according to an embodiment of the present invention;

[0047] Fig.14 Schematic diagram of light transmission of the diffractive light waveguide according to Example 1 of the present invention;

[0048] Fig.15 Schematic diagram of light transmission of the diffraction light waveguide of Comparative Example 1;

[0049] Fig.16 is a light intensity simulation diagram of the diffraction light waveguide of comparative example 1;

[0050] Fig.17 is a light intensity simulation diagram of the diffraction light waveguide of Example 1;

[0051] Fig.18 Schematic diagram of the eye box of the diffractive optical waveguide of Example 1;

[0052] Fig.19 Graph showing light intensity at different angles at the eye box of the diffractive light waveguide of Example 1. DETAILED DESCRIPTION

[0053] 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.

[0054] 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.

[0055] 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.

[0056] See also Figure 1 The diffractive optical waveguide 100 of one embodiment of the present invention includes a waveguide substrate 110, and the waveguide substrate 110 includes an incoupling region 120, a turning region 130, and an outcoupling region 140. The waveguide substrate 110 can be glass or resin, and has a high visible light transmittance property.

[0057] The coupling region 120 is used to couple the image light into the waveguide substrate 110. Specifically, the coupling region 120 can receive the incident light and couple it. The diameter of the coupling region 120 is not less than the width of the incident light beam, and the width of the incident light beam is limited by the material refractive index, thickness and incident angle of the waveguide substrate 110.

[0058] The turning area 130 is located at one side of the coupling-in area 120, and is used to receive and couple the image light from the coupling-in area 120. Specifically, the turning area 130 has the functions of pupil expansion and light bending, and can also couple and conduct.

[0059] The outcoupling region 140 is located at one side of the turning region 130, and is used to receive the image light from the turning region 130 and couple the image light out. The outcoupling region 140 has the function of emitting and conducting the image light.

[0060] The direction from the coupling region 120 to the turning region 130 is the first direction (ie Figure 1The turning area 130 includes at least two turning blocks 131 arranged in sequence along the first direction, and the efficiency modulation function of the at least two turning blocks 131 is progressive along the first direction. In this embodiment, the angle between the extension direction of the turning block 131 and the first direction is an acute angle. The efficiency modulation function of the turning block 131 refers to the function of the turning block 131 to modulate the diffraction efficiency of light, and the efficiency modulation function of the at least two turning blocks 131 is progressive along the first direction, which means that the function of the at least two turning blocks 131 to modulate the diffraction efficiency of light is increasingly stronger along the first direction.

[0061] The direction from the turning region 130 to the outcoupling region 140 is the second direction (i.e. Figure 1 The coupling region 140 includes at least two coupling blocks 141 arranged in sequence along the second direction, and the efficiency modulation functions of the at least two coupling blocks 141 are progressive along the second direction. The efficiency modulation function of the coupling block 141 refers to the function of modulating the diffraction efficiency of light possessed by the coupling block 141, and the efficiency modulation function of the at least two coupling blocks 141 is progressive along the second direction, which means that the function of modulating the diffraction efficiency of light possessed by the at least two second coupling blocks 141 is increasingly stronger along the second direction.

[0062] In the diffraction optical waveguide 100 of this embodiment, each turning block 131 and coupling-out block 141 has different characteristic structures and optical coupling performances, and can reasonably distribute the diffraction energy per unit area by performing efficiency partitioning on the turning area 130 and the coupling-out area 140 respectively, and balance the diffraction efficiency at different positions in the coupling-out area 140, thereby improving the brightness uniformity of different observation images within the eye box range.

[0063] On the basis of the above-mentioned embodiment, the width of the turning block 131 along the second direction is not less than the width of the light spot entering the coupling-in region 120, and the length of the turning block 131 along the first direction is obtained based on a preset cutoff efficiency threshold of the image light in the turning block 131. Furthermore, the width of the turning block 131 along the second direction increases with the transmission distance and incident angle of the image light, so that the transmission of image light at all angles can be satisfied.

[0064] On the basis of the foregoing embodiment, the lengths of at least two turning blocks 131 along the first direction decrease or are the same.

[0065] Based on the above implementation methods, please refer to Figure 2 , the length of the turning block 131 along the first direction is n*d, 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 turning block 131, and a turning efficiency of an initial grating structure to an adjacent grating structure along the second 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 turning efficiency of the image light in the turning block 131 along the second direction after the nth total reflection is a*b n-1 The transmission efficiency of the image light along the first direction at the nth total reflection in the turning block 131 is b n The cutoff efficiency threshold of the image light in the turning block 131 is preset to be ε. When the efficiency of the nth transmission is a*b n-1 When < a*ε, the turning block ends, and the length of the turning block along the first direction is n*d;

[0068] Where d is the total reflection point spacing, and 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, λ is the incident wavelength, p is the grating period, and n is 0 is the waveguide refractive index.

[0071] In the above steps, the turning block 131 refers to any turning block 131 in the turning area 130, and the actual length of the turning block 131 along the first direction may be slightly greater than or slightly less than the specific value of n*d. After the length of a certain turning block 131 along the first direction is obtained based on the above steps, the method for calculating the length of an adjacent turning block 131 along the first direction is equivalent to the above principle.

[0072] On the basis of the foregoing implementation, the width of the outcoupling block 141 along the second direction is obtained based on a preset cutoff efficiency threshold of the image light in the outcoupling block 141 .

[0073] On the basis of the foregoing implementation, the widths of at least two decoupling blocks 141 along the second direction decrease or are the same.

[0074] Based on the above implementation methods, please refer to Figure 3 , the width of the outcoupling block 141 along the second direction is n*d, 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 decoupling block 141, a transmission efficiency of an initial grating structure to an adjacent grating structure along the second direction is defined as A, and a decoupling efficiency of the initial grating structure is defined as B;

[0076] S40, the transmission efficiency of the image light along the second direction after the nth total reflection in the outcoupling block 141 is A n , the coupling efficiency is A n-1 *B, the cutoff efficiency threshold of the image light in the coupling-out block 141 is preset to be ε, when the efficiency A of the nth transmission n *B<ε*B, the coupling-out block is terminated, and at this time, the width of the coupling-out block 141 along the second direction is n*d;

[0077] Where d is the total reflection point spacing, and is calculated based on formula (I):

[0078] d = t*tan(arcsin(λ / p / n 0 ))*2(I);

[0079] 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.

[0080] In the above steps, coupling block 141 refers to any coupling block 141 in coupling region 140, and the actual width of coupling block 141 along the second direction can be slightly larger than or slightly smaller than the specific numerical value of n*d. After the width of a certain coupling block 141 along the second direction is obtained based on the above steps, the method for calculating the width of adjacent coupling blocks 141 along the second direction is equal to the above principle. For example, finish the first coupling block 141, carry out the second coupling block 141, the conduction efficiency of the grating structure of the second coupling block 141 along the second direction is: An*A1, the coupling efficiency is An*B1, A1 is the efficiency of the conduction of the coupling block 141 along the second direction, and B1 is the efficiency of the coupling out of the second coupling block 141.

[0081] On the basis of the above-mentioned implementation, at least one of the grating period, grating depth and duty cycle of two adjacent turning blocks 131 is different; or at least one of the grating period, grating depth and duty cycle of two adjacent outcoupling blocks 141 is different. Specifically, one, two or three of the grating period, grating depth and duty cycle of two adjacent turning blocks 131 are different; one, two or three of the grating period, grating depth and duty cycle of two adjacent outcoupling blocks 141 are different.

[0082] It should be noted that, in the diffractive optical waveguide of the present invention, the positions of the coupling-in region, the turning region and the coupling-out region of the waveguide substrate are not limited to the above-mentioned embodiments.

[0083] See also Figure 4A diffractive optical waveguide 200 according to another embodiment of the present invention includes a waveguide substrate 210, and the waveguide substrate 210 includes an incoupling region 220, a turning region 230, and an outcoupling region 240. In this embodiment, the turning region 230 is designed longitudinally, and the outcoupling region 240 is designed transversely.

[0084] The direction from the coupling region 220 to the turning region 230 is the first direction (ie Figure 4 The turning area 230 includes at least two turning blocks 231 arranged in sequence along the first direction, and the efficiency modulation functions of the at least two turning blocks 231 are progressive along the first direction.

[0085] The direction from the turning region 230 to the outcoupling region 240 is the second direction (ie Figure 4 the outcoupling region 240 includes at least two outcoupling blocks 241 sequentially arranged along the second direction, and the efficiency modulation function of at least two outcoupling blocks 241 is progressive along the second direction.

[0086] In the diffraction optical waveguide 200 of this embodiment, each turning block 231 and coupling-out block 241 has different characteristic structures and optical coupling performances, and can reasonably distribute the diffraction energy per unit area by performing efficiency partitioning on the turning area 230 and the coupling-out area 240 respectively, and balance the diffraction efficiency at different positions in the coupling-out area 240, thereby improving the brightness uniformity of different observation images within the eye box range.

[0087] 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 turning area and the out-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.

[0088] 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.

[0089] See also Figure 5 In another embodiment of the diffractive optical waveguide of the present invention, only a part of the outcoupling region 140 is partitioned for efficiency, that is, Figure 5 The sub-coupling region 142 in the middle of the outcoupling region 140. The optical efficiency modulation capability in the sub-coupling region 142 is different from that in the rest of the outcoupling region 140. Figure 5 When the efficiency partition design is performed for the sub-coupling area 142, the intensity of the outgoing light in the entire outcoupling area is as follows: Figure 6 As shown in the figure, it can be found that there is obvious uneven brightness in the middle area. Figure 5 When designing the efficiency partition of the sub-coupling area 142, Figure 6 There is a bright column in the middle, and due to the efficiency modulation of the middle sub-coupling area 142, the uniformity of the overall outgoing light is balanced, such as Figure 7 shown.

[0090] Furthermore, the diffractive optical waveguide of the present invention can be fabricated using several different fabrication methods.

[0091] See also Figure 8 The method for preparing the diffractive optical waveguide according to the first embodiment of the present invention comprises the following steps:

[0092] Step 1: First pass two beams of light ( Figure 8 The surface of the waveguide substrate 110 coated with the photosensitive adhesive 150 is exposed in the form 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 structure area.

[0093] Step 2: Set the layout of each partition block based on theoretical calculation and simulation.

[0094] Step 3: Establish a mapping model between structural parameters and lithography parameters, and determine the corresponding stereolithography parameters of each area according to the partition distribution.

[0095] Step 4: Perform regionalized stereolithography to superimpose stereolithography light field energy in the photosensitive resin 150 , and different partition blocks have different accumulated energies.

[0096] Step 5: Develop in a special developer. During the same development time, areas with different energy accumulation form structural surfaces with different parameters.

[0097] See also Fig. 9 The method for preparing the diffractive optical waveguide according to the second embodiment of the present invention comprises the following steps:

[0098] Step 1: Set the layout of each partition based on theoretical calculation and simulation.

[0099] Step 2: Establish a mapping model between the structural area division layout and the lithography parameters, and determine the corresponding stereolithography parameters of each area according to the partition distribution.

[0100] Step 3: Perform regionalized stereolithography to accumulate stereolithography light field energy in the photosensitive resin 150, and different outcoupling blocks accumulate different energies.

[0101] Step 4: Expose the surface of the waveguide substrate 110 coated with the photosensitive adhesive 150 by means of interference of two beams of light, accumulate exposure energy, and superimpose a uniform interference energy surface on the entire outcoupling area.

[0102] Step 5: Develop in a special developer. During the same development time, areas with different energy accumulation form structural surfaces with different parameters.

[0103] See also Fig.10 The method for preparing a diffractive optical waveguide according to the third embodiment of the present invention comprises the following steps:

[0104] Step 1: Set the layout of each partition based on theoretical calculation and simulation.

[0105] Step 2: Establish a mapping model between each partition and the interference exposure dose, that is, each partition has a corresponding exposure time.

[0106] 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.

[0107] However, it should be noted that according to the exposure time corresponding to different partition blocks 160, aperture control is performed, and the aperture 170 can be hollow or have adjustable transmittance of the exposure light source; the exposure dose of different partition blocks 160 is precisely controlled by controlling the position, size or transmittance of the aperture 170.

[0108] See also Fig.11 , a design of aperture exposure in one embodiment, Fig.11 The middle block 161, the block 162, the block 163 and the block 164 are different blocks, which means that the exposure doses in these four areas are different. Fig.10 The hollow aperture 170 shown is used for displacement control, or apertures 170 with different transmittances are used for full-frame precise exposure.

[0109] 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.

[0110] 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.

[0111] See also Fig.12 A head-up display module 300 of an 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 Fig.12The light in the direction of the middle arrow passes through the coupling area and the turning area for pupil expansion transmission and then couples out to the windshield 320 of the car, and then enters the human eye through reflection from the windshield 320 for imaging. Since the head-up display module 300 is arranged in the car, the imaging light of the head-up display module 300 is reflected to the human eye through the windshield 320 of the car. The windshield 320 is transparent and information in the real world can be observed. The imaging light is reflected to the windshield 320 by the head-up display module 300, so that the imaging surface of the head-up display module 300 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.

[0112] See also Fig.13 An augmented reality wearable display module 400 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 140. The augmented reality wearable display module 400 of this embodiment is an augmented reality near-eye display module, specifically AR glasses. Of course, the augmented reality wearable display module 400 is not limited thereto, and can also be in other forms, such as a helmet.

[0113] Using the augmented reality wearable display module 400 of this embodiment, the image light is along Fig.13 The light in the direction of the middle arrow is emitted through the outcoupling area 140 of the diffractive light waveguide 100 and received by the human eye. Due to 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 area, thereby improving the display quality of the augmented reality wearable display module.

[0114] 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 turning area and the out-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.

[0115] 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 embodiments.

[0116] Example 1

[0117] The structure of the diffractive optical waveguide 100 of this embodiment is as follows: Figure 1As shown, the waveguide substrate 110 includes a coupling-in region 120, a turning region 130 and a coupling-out region 140. In this embodiment, the turning region 130 includes a Figure 1 The nine turning blocks 131 are sequentially arranged in the x direction, and the efficiency modulation functions of the nine turning blocks 131 are progressive along the first direction; the outcoupling region 140 includes Figure 1 The eight coupling blocks 141 are sequentially arranged in the y direction, and the efficiency modulation functions of the eight coupling blocks 141 are progressive along the second direction. The pupil expansion light of the diffraction light waveguide 100 of this embodiment is shown as follows Fig.14 As shown, from Fig.14 It can be seen that the structural area of ​​the diffractive optical waveguide 100 adopts Figure 1 When arranged as shown, any area can modulate the light utilization rate in the area individually, the purpose of which is to change the reduction of the output energy caused by the reduction of the total energy base transmitted in sequence.

[0118] In this embodiment, the nine turning blocks 131 are Figure 1 The eight coupling blocks 141 are numbered 1 to 9 in the x direction. Figure 1 The y direction is numbered 10 to 17 in sequence, and specific structural parameters of the turning block 131 and the coupling-out block 141 are shown in Table 1.

[0119] Table 1 Structural parameters of the turning block and the coupling-out block of the diffraction optical waveguide of Example 1

[0120] Coupling block number Period (nm) Depth(nm) Duty Cycle 1 440 60 0.2 2 440 60 0.25 3 440 70 0.25 4 440 80 0.25 5 440 90 0.25 6 440 100 0.25 7 440 100 0.3 8 440 120 0.35 9 440 170 0.5 10 440 50 0.45 11 440 60 0.45 12 440 70 0.45 13 440 80 0.45 14 440 90 0.45 15 440 100 0.45 16 440 120 0.45 17 440 160 0.45

[0121] Comparative Example 1

[0122] The structure of the diffractive optical waveguide 100' of comparative example 1 is the same as that of the diffractive optical waveguide 100 of embodiment 1, including a waveguide substrate 110', and the waveguide substrate 110' includes an outcoupling region 140'. The difference is that the turning region and the outcoupling region of the diffractive optical waveguide 100' of comparative example 1 are not partitioned, that is, the nanostructures in the entire surface of the structural region are covered with a structure with the same optical modulation characteristics. The pupil expansion light of the diffractive optical waveguide 100' of comparative example 1 is shown in FIG. Fig.16 As shown, from Fig.16It can be seen that if the turning area and the out-coupling area are respectively a whole nanostructure with the same optical and conduction properties, according to the light efficiency modulation characteristics of the nanostructure, when the light first contacts the regional nanostructure, the light energy that can be emitted is the highest; and the remaining light except the light emitted for the first time will continue to be transmitted according to the optical waveguide characteristics. When it contacts the regional nanostructure for the second time, since the nanostructure has the same characteristics, that is, the utilization rate of the light emission caused by the nanostructure is consistent, but the total amount of light is reduced, so the light energy emitted for the second time is reduced; and so on, if the optical waveguide supports a larger out-coupling area, it will cause the light energy to gradually decrease in the emission amplitude (i.e., the eye box area) corresponding to the out-coupling area.

[0123] Performance Testing:

[0124] (1) The diffraction waveguides of Comparative Example 1 and Example 1 were simulated, and the incident beam diameter was set to 9.5 mm and the incident angle was 0 degrees. Fig.16 and Fig.17 The optical emission simulation diagram is shown.

[0125] from Fig.16 It can be seen that for the diffractive optical waveguide 100' of comparative example 1, during the transmission process of light in the outcoupling region 140', the number of outgoing light rays gradually decreases, the light energy representing the exit pupil gradually decreases, and the overall energy output of the outcoupling region 140' is seriously uneven. Fig.16 The light intensity simulation shown is the result of not changing the outcoupling area 140 ′ to adapt to uniformity, and the result is not ideal. The light intensity distribution of the entire outcoupling area 140 ′ is seriously uneven, which will inevitably lead to a poor display experience.

[0126] from Fig.17 It can be seen that for the diffractive optical waveguide 100 of Example 1, during the light transmission process in the outcoupling region 140, the energy distribution of the outgoing light is significantly improved compared with the non-partitioned result, and the uniformity of the eye box range corresponding to the outcoupling region 140 is improved.

[0127] (2) Fig.18 The schematic diagram of light receiving at the Eyebox of the diffractive optical waveguide 100 of Example 1 is shown. The light is coupled in from the coupling-in region 120, then transmitted in the waveguide substrate 110, turned at the turning region (not shown), and finally coupled out from the coupling-out region 140. In actual applications, the coupling-out region 140 emits light at various angles, and the observer will watch at a certain distance from the coupling-out region 140. At this time, the area covered by the light at all angles that the human eye can observe is the Eyebox. It can be seen that for a larger coupling-out region 140, the actual Eyebox is much smaller than the size corresponding to the coupling-out region.

[0128] The uniformity of each FOV at the Eyebox of the diffractive optical waveguide 100 of Example 1 is further analyzed. Fig.19 As shown. Read the light intensity at different angles at the Eyebox to characterize the uniformity of the FOV in the Eyebox. At this time, the angle light uniformity of (4°, 2°) is 41.49%, the angle light uniformity of (4°, 0°) is 41.41%, the angle light uniformity of (4°, -2°) is 42.89%, the angle light uniformity of (0°, 2°) is 48.6%, the angle light uniformity of (0°, 0°) is 45.48%, the angle light uniformity of (0°, -2°) is 47.03%, the angle light uniformity of (-4°, 2°) is 51.84%, the angle light uniformity of (-4°, 0°) is 50.28%, and the angle light uniformity of (-4°, -2°) is 50.82%.

[0129] 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.

[0130] 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 diffractive optical waveguide comprises a waveguide substrate, wherein the waveguide substrate comprises: A coupling region, used for coupling image light into the waveguide substrate; A turning area, located at one side of the coupling-in area, and used to receive the image light of the coupling-in area and couple and conduct it; An outcoupling region, located at one side of the turning region, and used to receive the image light of the turning region and couple the image light out; The direction from the coupling region to the turning region is a first direction, the turning region includes at least two turning blocks arranged in sequence along the first direction, and the efficiency modulation functions of at least two turning blocks present a progressive trend along the first direction; The direction from the turning area to the coupling-out area is a second direction, and the second direction is perpendicular to the first direction; the coupling-out area includes at least two coupling-out blocks arranged in sequence along the second direction, and the efficiency modulation functions of at least two coupling-out blocks show a progressive trend along the second direction.

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

3. The diffractive optical waveguide according to claim 2, characterized in that: The lengths of at least two turning blocks along the first direction decrease or are the same.

4. The diffractive optical waveguide according to claim 2, characterized in that: The length of the turning 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 arranged in the turning block, and a turning efficiency of an initial grating structure to an adjacent grating structure along the second 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 turning efficiency of the image light along the second direction at the nth total reflection in the turning block is a*b n-1 The transmission efficiency of the image light along the first direction during the nth total reflection in the turning block is b n , the cutoff efficiency threshold of the image light in the turning block is preset to be ε, when the efficiency of the nth transmission is a*b n-1 <a*ε, the turning block is terminated, and at this time, the length of the turning 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.

5. The diffractive optical waveguide according to claim 1, characterized in that: The width of the outcoupling block along the second direction is obtained based on a preset cutoff efficiency threshold of the image light in the outcoupling block.

6. The diffractive optical waveguide according to claim 5, characterized in that: The widths of at least two of the decoupling blocks along the second direction decrease gradually or are the same.

7. The diffractive optical waveguide according to claim 5, characterized in that: The width of the outcoupling block along the second 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 outcoupling block, a transmission efficiency of an initial grating structure to an adjacent grating structure along the second direction is defined as A, and an outcoupling efficiency of the initial grating structure is defined as B; and The transmission efficiency of the image light along the second direction during the nth total reflection in the outcoupling block is A. n , the coupling efficiency is A n-1 *B, the cutoff efficiency threshold of the image light in the coupling block is preset to be ε, when the efficiency A of the nth transmission n *B<ε*B, the coupling-out block is terminated, and at this time, the width of the coupling-out block along the second 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.

8. The diffractive optical waveguide according to claim 1, characterized in that: At least one of the grating period, grating depth and duty cycle of two adjacent turning blocks is different; or At least one of the grating period, grating depth and duty cycle of two adjacent outcoupling blocks is different.

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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