Head-up display device

Abstract

The invention provides a head-up display device. The head-up display device comprises: an image device configured to emit light carrying image information; the diffractive optical waveguide is provided with a transparent waveguide substrate, a coupling-in structure and a coupling-out structure, wherein the coupling-in structure and the coupling-out structure are located on the surface of the transparent waveguide substrate or inside the transparent waveguide substrate; wherein the coupling-in structure is configured to receive light rays projected by the image device and enable the light rays to be totally reflected and conducted in the transparent waveguide substrate; the coupling-out structure is configured to couple the light transmitted in the transparent waveguide substrate out of the transparent waveguide substrate, and enable the coupled-out light to enter an eye movement area in a roughly parallel manner after being reflected by the windshield; wherein the coupled light rays are non-parallel light rays. The head-up display device is small in size, has high machining precision, has batch production capacity, and has considerable advantages in design, machining and cost control compared with a free-form surface technology.

Description

Technical Field

[0001] This invention relates to the field of display technology, and in particular to a head-up display device. Background Technology

[0002] Display technology, as a medium for human-computer interaction, is continuously expanding its applications across various industries. Among these, consumer electronics, commercial displays, and automotive displays have become the largest market share applications. As electric vehicles become increasingly accepted by the public, some emerging technologies are being promoted and applied in them. Augmented reality head-up displays (HUDs) have become standard equipment on electric vehicles. With the added computing power of AI chips, the human-computer voice interaction function of HUDs has become even more powerful. More virtual road information, speed information, building information, and warnings can be overlaid in real-world scenarios, bringing greater convenience and safety to drivers.

[0003] However, the mainstream technology for current in-vehicle augmented reality head-up displays (HUDs) is the reflective freeform surface solution. The main challenge with this technology is that the device size increases with the field of view, requiring sufficient space to be reserved in the central control area for installation, which reduces the installation space for other components. In addition, the increased size of the freeform surface reflector in the HUD also poses significant challenges to surface processing and precision control. Furthermore, the HUD and windshield need to be matched, and HUDs for different car models require separate project development, resulting in high development costs. Summary of the Invention

[0004] Therefore, the present invention aims to provide an improved head-up display device to solve at least one of the above-mentioned problems.

[0005] In a first aspect, this application provides a head-up display device, comprising: an image device configured to emit light carrying image information; and at least one diffractive waveguide having a transparent waveguide substrate and coupling-in and coupling-out structures located on or inside the transparent waveguide substrate.

[0006] The coupling structure is configured to receive light projected by the imaging device and conduct the light through total internal reflection within the transparent waveguide substrate; the coupling structure is configured to couple the light conducted in the transparent waveguide substrate out of the transparent waveguide substrate and to allow the coupled light to be reflected by the windshield and incident approximately parallel to the eye movement region.

[0007] The coupled light rays are non-parallel light rays.

[0008] The above-mentioned head-up display device has at least the following advantages:

[0009] 1. It is compact in size, and compared with the freeform surface solution, the field of view of the head-up display device can be increased by replacing the image device with one with a larger field of view. It is not limited by the spatial relationship between the reflectors and will not squeeze the installation space of other components in the central control area.

[0010] 2. Diffractive waveguides can be fabricated using industrial-grade photolithography machines, and then imprinted using the templates. Therefore, they have high processing precision and are not limited in size or travel. There are no bottlenecks in processing, and they have very efficient mass production capabilities.

[0011] 3. For different windshields, the same imaging device can be used, and the diffraction waveguide can be remade for adaptation. Compared with the freeform surface solution, there is no need to redesign the entire optical system, which increases the versatility of the imaging device, thus having a considerable advantage in design, processing and cost control.

[0012] 4. The light is coupled out through the coupling structure and reflected directly by the windshield, and can then be incident on the eye movement area in a roughly parallel manner, achieving eye-protection display without the need for an additional focusing device.

[0013] In one embodiment, the coupling structure includes a nanodiffraction grating having preset diffraction structure parameters configured such that the coupled light rays are converging or diverging rays; wherein the diffraction structure parameters include the period of the nanodiffraction grating; and, as the period of the nanodiffraction grating gradually decreases along a direction away from the coupling structure, the coupled light rays are converging rays and converge to a preset depth plane; as the period of the nanodiffraction grating gradually increases, the coupled light rays are diverging rays and the backward extensions of the diverging rays converge to the preset depth plane.

[0014] In one embodiment, the preset diffraction structure parameters include one or more of the following: grating constant, groove width, groove depth, duty cycle, and scribe line length.

[0015] In one embodiment, the windshield has a curved surface, and the reflected light formed by the reflection of the outgoing light rays from the diffraction waveguide by the windshield has an angle with the horizontal plane. The preset depth plane where the outgoing light rays from the diffraction waveguide or the backward extension of the outgoing light rays converge has a distance from the focal plane of the windshield, and the angle is positively correlated with the distance.

[0016] In one embodiment, the preset depth plane is parallel to or coincides with the focal plane of the windshield.

[0017] In one embodiment, the light emitted from the coupling structure is reflected by the windshield and then incident on the eye movement area at an angle of ±8.5° relative to the horizontal plane.

[0018] In one embodiment, the head-up display device includes a plurality of diffractive waveguides, wherein the outgoing rays or reverse extensions of the outgoing rays from at least two diffractive waveguides converge to different preset depth planes.

[0019] In one embodiment, the windshield has a curved surface, and the plane to which the coupled rays from at least one diffracted waveguide converge coincides with the focal plane of the windshield.

[0020] In one embodiment, the coupling-in and coupling-out structures of the plurality of diffractive waveguides are integrated on a transparent waveguide substrate.

[0021] In one embodiment, the imaging device is configured to emit light beams with different field of view angles, the imaging device comprising: an image source; an illumination optical system configured to project illumination light onto the image source; and a projection optical system configured to collimate the light emitted by the image source, the projection optical system including a telecentric projection lens with an external exit pupil. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this specification or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this specification. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the optical path for implementing a head-up display using freeform surface technology in existing technologies.

[0024] Figure 2 This is a schematic diagram of the composition of a head-up display device according to an embodiment of this application;

[0025] Figure 3 This is a schematic diagram of the composition of a diffractive optical waveguide according to an embodiment of this application;

[0026] Figure 4 This is a schematic diagram of the optical path of a head-up display device according to an embodiment of this application;

[0027] Figure 5 This is a schematic diagram of the convergence of the coupled rays from a diffractive waveguide according to an embodiment of this application;

[0028] Figure 6 This is a dot diagram of different wavelengths of light rays coupled out of a diffractive waveguide according to an embodiment of this application;

[0029] Figure 7This is a graph showing the MTF curves of different wavelengths of coupled light from a diffractive waveguide according to an embodiment of this application;

[0030] Figure 8 This is a schematic diagram illustrating the composition of a head-up display device according to another embodiment of this application;

[0031] Figure 9 This is a schematic diagram of the composition of a diffractive waveguide according to another embodiment of this application;

[0032] Figure 10 This is a schematic diagram of the optical path of a head-up display device according to a specific embodiment of this application.

[0033] Component designation explanation:

[0034] 1. Head-up display device; 2. Windshield; 10. Image device; 20. Diffractive waveguide; 210. Transparent waveguide substrate; 220. Coupled-in region; 230. Coupled-out region; 310. Transparent waveguide substrate; 320. Coupled-in region; 330. Coupled-out region; 340. Coupled-in region; 350. Coupled-out region; 360. Coupled-in region; 370. Coupled-out region. Detailed Implementation

[0035] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0036] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0037] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0038] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0039] like Figure 1 As shown, existing in-vehicle augmented reality head-up display technology uses a freeform surface technology solution. The light emitted from the image source passes through two reflectors and is then reflected by the windshield before entering the driver's eyes. The entire optical system is affected by the spatial position and shape of the two reflectors. To ensure the virtual image distance, the system is relatively large and requires sufficient space in the central control area for installation. In addition, the processing of the freeform surface reflectors involves using a diamond lathe to create molds (high-precision, long-stroke diamond lathes are very expensive). The reflectors are then processed by injection molding. The size of the reflectors is limited by the stroke of the diamond lathe and the injection shrinkage rate of large workpieces, making the processing of large freeform surfaces very difficult. Furthermore, different car models require a complete redesign of the entire optical system for the windshield, resulting in a long development cycle and high development costs, which is not conducive to product technology iteration.

[0040] To address the aforementioned issues, this application provides an improved head-up display device that employs a diffractive waveguide for image display. This results in a smaller installation volume. By replacing the image device with one that has a larger field of view, the viewing angle of the head-up display device can be increased without encroaching on the installation space of other components in the central control area. Furthermore, the diffractive waveguide can be fabricated using an industrial-grade photolithography machine, and then imprinted using the template. Therefore, it possesses high processing precision and is not limited in terms of width or travel, eliminating processing bottlenecks and enabling highly efficient mass production. Moreover, the same image device can be used for different windshields, and the diffractive waveguide can be remade for adaptation. Compared to freeform surface solutions, this eliminates the need to redesign the entire optical system, increasing the versatility of the image device and providing significant advantages in design, processing, and cost control. In addition, light emitted through the coupling structure and reflected directly by the windshield can be incident approximately parallel to the eye-tracking area, achieving eye-protection display without the need for an additional focusing device.

[0041] like Figure 2 and Figure 3 As shown, this application provides a head-up display device 1, including: an image device 10 configured to emit light carrying image information; and at least one diffractive waveguide 20, the diffractive waveguide 20 having a transparent waveguide substrate 210 and a coupling structure 220 and a coupling structure 230 located on or inside the transparent waveguide substrate 210; wherein, the coupling structure 220 is configured to receive light projected by the image device 10 and conduct the light through total internal reflection within the transparent waveguide substrate 210; the coupling structure 230 is configured to couple the light conducted in the transparent waveguide substrate 210 out of the transparent waveguide substrate 210, and to cause the coupled light to be reflected by a windshield 2 and incident approximately parallel to the eye movement region; wherein, the coupled light is non-parallel light.

[0042] For example, the image device 10 is configured to emit light beams with different field of view angles to provide image information. The image device 10 includes: an image source; an illumination optical system configured to project illumination light onto the image source; and a projection optical system configured to collimate the light emitted from the image source, the projection optical system including a telecentric projection lens with an external exit pupil. The illumination optical system is used to uniformly illuminate the image source and may include a light source, a condenser lens, a light homogenizing device, a color wheel device, and an integrating projection device; the light source may be a laser, a light-emitting diode (LED), an organic light-emitting diode (OLED), a miniLED, a microLED, or other light source types, but is not limited to these types; the image source may be a digital light processing (DLP), a liquid crystal display (LCD), a liquid crystal on silicon (LCOS), or other display methods, but is not limited to these display methods. In addition, setting a telecentric projection lens with an external exit pupil helps to eliminate distortion, improve image quality, expand the field of view, adapt to different eye distances, and reduce light attenuation, thus improving the performance, user experience, and security of the head-up display device 1.

[0043] For example, the diffractive waveguide 20 is used to receive the input light carrying image information projected by the imaging device 10, so that the input light is coupled and guided within the transparent waveguide substrate 210 and coupled out through the coupling structure 230. Optionally, the input light can be guided within the transparent waveguide substrate 210 by total internal reflection. Optionally, the diffractive waveguide 20 has a high transmittance in visible light, for example, its transmittance may not be less than 70%. Optionally, the number of diffractive waveguides 20 may be one or more. When the number of diffractive waveguides 20 is one, the coupled light from the diffractive waveguide 20 is reflected by the windshield 2 and received by the human eye, thereby allowing the observation of a virtual image located on the other side of the windshield 2 to display vehicle driving information.

[0044] For example, both the coupling-in structure 220 and the coupling-out structure 230 can be composed of structures or materials with diffraction properties, and can be distributed on the surface or inside of the transparent waveguide substrate 210. When distributed on the surface of the transparent waveguide substrate 210, the coupling-in structure 220 and the coupling-out structure 230 can be distributed on the same side of the transparent waveguide substrate 210 or on opposite sides of the transparent waveguide substrate 210. Optionally, the coupling-in structure 220 and the coupling-out structure 230 can be nano-diffraction gratings, thereby allowing incident light to exit at a certain diffraction angle to propagate along a designed path.

[0045] For example, such as Figure 4 As shown, the light rays coupled out of the diffractive waveguide 20 are non-parallel, and after being reflected by the windshield 2, they can be incident on the eye-tracking area in a roughly parallel manner. Typically, the windshield 2 is not a flat glass, but has a surface shape and focal point. The above arrangement helps to adapt to the surface shape of the windshield 2, achieving eye-friendly display of driving information. Optionally, the non-parallel light rays can be divergent or converging; the roughly parallel incident light rays on the eye-tracking area can mean that the reflected light rays are incident on the eye-tracking area within a certain angle range relative to the horizontal plane. Within this angle range, the driver usually will not feel visual discomfort. Optionally, this angle range can be ±10°, ±8.5°, or ±5° relative to the horizontal plane.

[0046] In some embodiments of this application, the coupling structure 230 has preset structural parameters, which are configured to make the coupled light rays either converging or diverging, and the coupling angle of the light rays meets the following requirements: when the coupled light rays are converging, the converging light rays converge to a preset depth plane; when the coupled light rays are diverging, the backward extensions of the diverging light rays converge to the preset depth plane. Optionally, when the coupling structure 230 includes a nanodiffraction grating, the preset structural parameters may be one or more of the following: grating constant (distance between two adjacent scribe lines), groove width (width of a scribe line in the grating), groove depth (depth of a scribe line in the grating), duty cycle (ratio of groove width to grating constant), and scribe line length.

[0047] Optionally, the windshield 2 is curved glass. The reflected light from the diffracted waveguide 20 forms an angle with the horizontal plane after reflection by the windshield 2. There is a gap between the preset depth plane where the diffracted waveguide 20 converges and the focal plane of the windshield 2, and the angle is positively correlated with the gap. That is, the closer the preset depth plane where the diffracted light converges is to the focal plane of the windshield 2, the more conducive it is to making the reflected light incident parallel to the eye movement region.

[0048] Optionally, the preset depth plane coincides with the focal plane of the windshield. Since windshields are typically curved, aligning the preset depth plane where the coupled rays converge with the focal plane of the windshield helps ensure that reflected rays enter the eye parallel to each other, thus making the virtual image distance of the image observed by the driver approach infinity. Optionally, based on the curved surface of the windshield 2, its focal plane is usually located below the windshield 2. Therefore, the coupling structure can be designed so that the coupled rays are divergent, and the backward extensions of these divergent rays converge to the focal plane below the windshield 2.

[0049] Optionally, the preset depth plane is parallel to the focal plane of the windshield 2. This helps to better converge the coupled light rays to the focal plane of the windshield 2, thereby ensuring that the virtual image distance of the image observed by the driver is close to infinity.

[0050] In some embodiments of the present application, as Figure 5 shown, the coupling-out structure 230 includes a nano-diffraction grating, the nano-diffraction grating has preset diffraction structure parameters, the diffraction structure parameters include the period of the nano-diffraction grating, and adjusting the period of the nano-diffraction grating can achieve the divergence or convergence of the coupled-out light; wherein, along the direction away from the coupling-in structure 220, when the period of the nano-diffraction grating gradually decreases (i.e., ΔP < 0, P1 > P2 >...), the coupled-out light is convergent light, and when the period of the nano-diffraction grating gradually increases (i.e., ΔP > 0, P1 < P2 <...), the coupled-out light is divergent light. When the coupled-out light is divergent light, the corresponding image pixels can be observed at the convergence position of the reverse extension line of the coupled-out light of the diffraction optical waveguide 20. On the other hand, the variable period setting is also beneficial for correcting the aberration caused by the surface shape of the windshield, that is, setting the parameters of the diffraction optical waveguide 20 according to the focal plane position of different surface shape windshields, without modifying the image device 10, which has great advantages in terms of design, processing, and cost control.

[0051] Figure 6 Shows the spot diagram of different wavelength lights on the rear convergence surface of the diffraction optical waveguide 20. It can be seen that almost all different wavelength lights fall within the Airy disk (black circle). It can be known that the convergence spot sizes of different wavelength lights are close to the Airy disk size, and further it can be known that the optical path from the diffraction optical waveguide 20 to the human eye is a good imaging relationship. Among them, different wavelength lights include blue light (455 nm, shown by blue cross lines), green light (530 nm, shown by red triangles), and red light (620 nm, shown by green squares).

[0052] Figure 7 Shows the modulation transfer function (MTF) curve graph of different wavelength lights on the rear convergence surface of the diffraction optical waveguide 20. MTF is an index used to measure the resolution and contrast transfer ability of an optical system, usually between 0 and 1. The larger the MTF, the better the imaging quality of the optical system, and it can transmit smaller details and higher contrast. In the MTF graph, the horizontal axis represents the spatial frequency (such as line pairs / mm, lp / mm), and the vertical axis represents the MTF value. From Figure 7 it can be known that the image quality of the head-up display device of the present application can meet the requirement that the MTF value of different wavelength lights at 1 lp / mm is greater than 0.3, so as to meet the image quality requirement of the human eye's limit resolution angle of 1'.

[0053] In some embodiments of the present application, as Figure 8As shown, the head-up display device 1 includes multiple diffractive waveguides 20, wherein the outgoing rays or the reverse extensions of the outgoing rays from at least two diffractive waveguides converge to different preset depth planes. This allows images to be displayed at multiple different virtual image distance positions on the other side of the windshield 2, thereby facilitating the display of stereoscopic information and enhancing the driver's viewing experience.

[0054] Optional, such as Figure 8 As shown, the convergence point of the rays coupled out of the first diffractive waveguide is closer than that of the rays coupled out of the second diffractive waveguide. Therefore, after reflection by the windshield 2, the virtual image projected by the image device corresponding to the first diffractive waveguide has a shallower depth than that projected by the image device corresponding to the second diffractive waveguide. The convergence point of the rays coupled out of the third diffractive waveguide is the furthest, and after reflection by the windshield 2, the virtual image projected by the image device corresponding to the third diffractive waveguide has the greatest depth. Optionally, different image information at each virtual image plane can be set to different types of information, such as speed, road signs, dashboard information, etc., depending on the actual application. It can also be set to form three-dimensional information. It is understood that in some other embodiments, the head-up display device 1 is not limited to three diffractive waveguides; for example, four or five waveguides can be used.

[0055] Optionally, the windshield 2 has a curved surface, so that the plane to which the coupled rays or the backward extensions of the coupled rays of at least one diffracting waveguide 20 converge coincide with the focal plane of the windshield 2. This facilitates the parallel incident light rays into the eye, thereby making the virtual image distance of the image observed by the driver approach infinity.

[0056] Optionally, the coupling and coupling structures of multiple diffractive waveguides are integrated and disposed on a single transparent waveguide substrate. For example... Figure 9 As shown, a transparent waveguide substrate 310 employs three coupling-in regions and three coupling-out regions. Image information entering from the coupling-in regions propagates within the transparent nanowaveguide substrate 310 and exits from the coupling-out regions, and so on. The coupling-in region 320 and the coupling-out region 330 constitute the first display optical path, the coupling-in region 340 and the coupling-out region 350 constitute the second display optical path, and the coupling-in region 360 and the coupling-out region 370 constitute the third display optical path. The coupling-out regions 330, 350, and 370 can be designed with different grating structures. The backward extensions of the light rays coupled out from the three coupling-out regions converge on different planes and, after reflection by the windshield 2, can be projected into different depths of space for image display.

[0057] The solution of this application will be further described below through a specific embodiment.

[0058] like Figure 10As shown, in this specific embodiment, the windshield has a radius of curvature of 3000mm in the xz plane and 4000mm in the yz plane. The eyebox (eye movement area) is 850mm away from the windshield, and the diffractive waveguide is 400mm away from the windshield. With the center of the eyebox as the origin of the global coordinate system, the global coordinates of the center of the diffractive waveguide are (-25.7, -209.8, 908), and the global coordinate angle of the normal of the diffractive waveguide (the angle between the normal and the xyz axes) is (98°, 162°, 63°). To enable the driver to observe a virtual image at infinity, the grating distribution in the coupling region of the diffractive waveguide needs to be adjusted so that the backward extensions of the light rays coupled from the coupling region converge to an image plane. The global coordinates of the center of this image plane are (-335, -2308, 1978.1), and the global coordinate angle of the normal of the image plane is the same as the global coordinate angle of the normal of the diffractive waveguide.

[0059] Furthermore, based on the positional relationship of the global coordinates of the intersection point of the diffracted waveguide and the image plane of the reverse extension line, the period P1 of the nano-diffraction grating in the coupling structure is 350 nm, the period P2 is 352 nm, and so on, gradually increasing to a period of 420 nm at the center of the waveguide. The nano-diffraction gratings on the left and right sides of the coupling structure are symmetrically distributed.

[0060] With the above settings, this specific embodiment allows the coupled light rays to be reflected by the windshield and then incident parallel to the driver's eye movement area, thereby enabling the driver to observe virtual image information at infinity.

[0061] It should be noted that the numbers used to describe and claim certain embodiments of this application, representing quantities or properties, should be understood to be modified in some cases by the terms "approximately," "about," "approximately," or "essentially." For example, unless otherwise stated, "approximately," "about," "approximately," or "essentially" can indicate a variation of ±20% of the value they describe. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may be changed according to the characteristics required by individual embodiments. In some embodiments, numerical parameters should take into account specified significant digits and employ a general method of digit reservation. Although the numerical ranges and parameters used to confirm their breadth of range in some embodiments of this application are approximate values, in specific embodiments, such numerical values ​​are set as precisely as feasible.

[0062] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above 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.

[0063] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A head-up display device, characterized in that, include: An image device is configured to emit light carrying image information; as well as, At least one diffractive waveguide, the diffractive waveguide having a transparent waveguide substrate and coupling-in and coupling-out structures located on or inside the transparent waveguide substrate; The coupling structure is configured to receive light projected by the imaging device and conduct the light through total internal reflection within the transparent waveguide substrate; The coupling structure is configured to couple light propagating in the transparent waveguide substrate out of the transparent waveguide substrate, and to allow the coupled light to be reflected by the windshield and incident approximately parallel to the eye movement region. The coupled light rays are non-parallel light rays.

2. The head-up display device according to claim 1, characterized in that, The coupling structure includes a nano-diffraction grating, which has preset diffraction structure parameters configured to make the coupled light rays converge or diverge. The diffraction structure parameters include the period of the nano-diffraction grating; and, when the period of the nano-diffraction grating gradually decreases along the direction away from the coupling structure, the coupled light rays are converging light rays and converge to a preset depth plane; when the period of the nano-diffraction grating gradually increases, the coupled light rays are diverging light rays and the backward extensions of the diverging light rays converge to the preset depth plane.

3. The head-up display device according to claim 2, characterized in that, The preset diffraction structure parameters include one or more of the following: grating constant, groove width, groove depth, duty cycle, and scribe line length.

4. The head-up display device according to claim 2, characterized in that, The windshield has a curved surface. The reflected light formed by the outgoing light rays of the diffraction waveguide after reflection by the windshield has an angle with the horizontal plane. The preset depth plane where the outgoing light rays of the diffraction waveguide or the backward extension of the outgoing light rays converge has a distance from the focal plane of the windshield. The angle is positively correlated with the distance.

5. The head-up display device according to claim 4, characterized in that, The preset depth plane is parallel to or coincides with the focal plane of the windshield.

6. The head-up display device according to claim 1, characterized in that, The light emitted from the coupling structure is reflected by the windshield and then incident on the eye movement area at an angle of ±8.5° relative to the horizontal plane.

7. The head-up display device according to claim 2, characterized in that, The head-up display device includes multiple diffractive waveguides, wherein the outgoing rays or reverse extensions of the outgoing rays from at least two diffractive waveguides converge to different preset depth planes.

8. The head-up display device according to claim 7, characterized in that, The windshield has a curved surface, and the plane at a preset depth to which the coupled rays from at least one diffractive waveguide converge coincides with the focal plane of the windshield.

9. The head-up display device according to claim 8, characterized in that, The coupling-in and coupling-out structures of the multiple diffractive waveguides are integrated on a transparent waveguide substrate.

10. The head-up display device according to any one of claims 1 to 9, characterized in that, The imaging device is configured to emit light beams with different field of view angles, and the imaging device includes: Image source; An illumination optical system is configured to project illumination light onto the image source; A projection optics system is configured to collimate the light emitted from the image source, the projection optics system including a telecentric projection lens with an external exit pupil.

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