Head-up display system based on two-dimensional geometric array waveguide

Abstract

The invention relates to a two-dimensional geometric array waveguide-based head-up display system. The head-up display system based on the two-dimensional geometric array waveguide comprises an image generation unit and at least two one-dimensional array waveguides, each one-dimensional array waveguide is composed of a plurality of sub-prisms, and the inclined surfaces of the sub-prisms are provided with angle selective transmission reflecting films. The system further comprises a Fresnel lens component and a diffractive optical element. The Fresnel lens component is used for compensating aberration introduced by an automobile windshield, and the diffractive optical element is used for expanding the optical expansion amount. According to the technical scheme, a larger display range can be achieved on the premise that the size of the automobile head-up display system is not obviously increased.

Description

Technical Field

[0001] The present invention relates to the technical field of automobile head-up display, and in particular to a head-up display system based on a two-dimensional geometric array waveguide. Background Art

[0002] Driven by the modern automobile industry and intelligent driving technology, head-up display systems have gradually become an important means of visualizing vehicle information. By projecting key information such as vehicle speed, navigation instructions and warning prompts directly into the driver's field of vision, the driver's frequency of looking down at the dashboard is reduced, improving driving safety and driving comfort. Compared with traditional instruments or central control screens, head-up display systems can provide drivers with a more immersive driving environment and gain more reaction time in emergencies, which makes it have great application potential in high-end models and future unmanned driving fields.

[0003] The earliest Combiner Head-Up Display (Chinese name "synthetic mirror head-up display") in the prior art usually requires an additional independent imaging plate to be set in front of the windshield, which not only increases the system volume but also makes the vehicle structure more complicated; the subsequently developed Windshield Head-Up Display (Chinese name "windshield head-up display") uses the windshield as a reflective mirror, but it is still difficult to achieve a significantly expanded display range in a limited space, and when the windshield curvature is more complex, aberration correction is also more difficult. The augmented reality head-up display technology that has emerged in recent years superimposes real-time traffic instructions and auxiliary information on the basis of traditional head-up display, but there is still a trade-off between field of view coverage, system compactness and imaging quality. How to achieve a larger display range without significantly increasing the overall system volume, so that the driver can obtain a wider range of information projection in a relatively limited cockpit space, has become a technical problem that technicians in this field urgently need to solve. Summary of the invention

[0004] The main purpose of the present invention is to solve the technical problem that the existing automobile head-up display system is difficult to achieve a larger display range without significantly increasing the system volume.

[0005] A first aspect of the present invention provides a head-up display system based on a two-dimensional geometric array waveguide, the head-up display system based on a two-dimensional geometric array waveguide includes an image generation unit and an array waveguide; The arrayed waveguide comprises: A plurality of sub-prisms arranged along a first direction, each of the sub-prisms having a first inclined surface, a second inclined surface, an upper surface and a lower surface; The plurality of upper surfaces are sequentially connected to form an upper end surface of the arrayed waveguide, and the plurality of lower surfaces are sequentially connected to form a lower end surface of the arrayed waveguide; A first preset angle is formed between the first inclined surface and the lower end surface; A plurality of the first inclined surfaces and a plurality of the second inclined surfaces are alternately arranged along the first direction and are parallel to each other; The first inclined surface of the first sub-prism and the second inclined surface of the last sub-prism are both provided with total reflection films, and the first inclined surfaces of the other sub-prisms except the first sub-prism are all provided with angle selective transmission reflection films; The light coupling-in area of ​​the array waveguide is arranged on the lower surface of the first sub-prism, and the light coupling-out area is arranged on the upper end surface; wherein, The light generated by the image generating unit enters the array waveguide through the light coupling-in area, and is reflected back and forth between the upper end face and the lower end face at a total reflection critical angle not less than that of the upper end face and the lower end face under the reflection of the total reflection film of the first sub-prism; The angle selectively transparent reflective film is configured to transmit part of the incident light and reflect the remaining incident light, a part of the light reflected by the angle selectively transparent reflective film among all the angle selectively transparent reflective film is emitted toward the upper end surface and transmitted through at a total reflection critical angle smaller than the upper end surface, and another part of the light reflected by the angle selectively transparent reflective film is emitted toward the lower end surface, and after being reflected at the lower end surface, is emitted toward the upper end surface and transmitted through at a total reflection critical angle smaller than the upper end surface.

[0006] Optionally, in the first direction, the reflectivity of the angle selectively transparent reflective film is The following relationship is satisfied: ; in, is the serial number of the angle selective transmission reflective film, and its value range is from 1 to M, where M is the total number of first inclined surfaces on which the angle selective transmission reflective film is provided in the array waveguide.

[0007] Optionally, the first preset angle is ; The light generated by the image generation unit has a predetermined viewing angle, and the half angle of the predetermined viewing angle is ; and The following relations are satisfied: ; ; ; ; in, is the refractive index of the array waveguide.

[0008] Optionally, the number of the arrayed waveguides is at least two, and all of the arrayed waveguides include a first arrayed waveguide arranged along the first direction, and a second arrayed waveguide arranged along a second direction perpendicular to the first direction, wherein: The light coupling-in region of the first arrayed waveguide is connected to the image generating unit, and the light coupling-out region of the first arrayed waveguide is connected to the light coupling-in region of the second arrayed waveguide, so that light propagates and expands the pupil through the first arrayed waveguide and the second arrayed waveguide in sequence.

[0009] Optionally, a car windshield is arranged on the light emitting path of the second array waveguide, and a Fresnel lens component is arranged between the car windshield and the second array waveguide, and the Fresnel lens component is configured to compensate for the aberration introduced by the car windshield in different directions.

[0010] Optionally, the Fresnel lens component comprises a first cylindrical Fresnel lens and a second cylindrical Fresnel lens, and the first cylindrical Fresnel lens and the second cylindrical Fresnel lens are stacked; The first cylindrical Fresnel lens includes a first substrate and a first Fresnel structure disposed on the first substrate; The second cylindrical Fresnel lens includes a second substrate and a second Fresnel structure disposed on the second substrate; The first Fresnel structure extends along a third direction, and the second Fresnel structure extends along a fourth direction perpendicular to the third direction.

[0011] Optionally, the radial sections of the first Fresnel structure and the second Fresnel structure have the same sagittal height expression as the even-order aspheric surface, and the sagittal height expression is: ; in, is the base curvature coefficient, is the curvature, is the distance from the point on the aspherical surface to the optical axis, is the cone coefficient, is the aspheric coefficient; is the y coordinate of the point on the surface, The value of is 1 to 16.

[0012] Optionally, the head-up display system based on the two-dimensional geometric array waveguide also includes a diffractive optical element, which is arranged at the exit pupil of the image generating unit or the entrance pupil of the array waveguide, and the diffractive optical element is used to expand the optical extension, and the pixel size of the diffractive optical element is smaller than the pixel size of the spatial light modulator in the image generating unit.

[0013] Optionally, two adjacent sub-prisms in the arrayed waveguide are fixed by bonding.

[0014] The head-up display system based on the two-dimensional geometric array waveguide described in the present invention gradually expands the display range in a limited space by multiple reflections and partial transmissions of light in the waveguide, thereby obtaining a wider projection range without significantly increasing the volume of the system. The key lies in the reasonable design of the inclined surface of the sub-prism, and the arrangement of a total reflection film at the first and last sub-prisms to maintain the efficient propagation of light, while arranging an angle selective transmission reflection film at the middle sub-prism to couple out part of the light in batches. Since the sub-prisms are alternately arranged in the same waveguide structure, each time the light encounters an inclined surface, it can be guided to perform total reflection or transmission, thereby extending the light path and gradually expanding in the horizontal and vertical directions, and finally forming a large display range.

[0015] Unlike traditional technologies that rely on large-volume reflector groups or additional multi-layer lenses to expand the field of view, the present invention achieves efficient light coupling and expansion in the waveguide. Multiple reflections can avoid a large amount of scattering losses, and moderate transmission allows part of the light to be emitted at the best time, thereby significantly improving the visual range and imaging uniformity while keeping the overall system compact. Through the above arrangement, the technical bottleneck of the existing head-up display system that is difficult to achieve a larger display range due to volume limitations is effectively solved, laying a good foundation for providing a head-up display with a wide field of view and stable imaging quality in a limited cockpit space. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0017] Figure 1 It is a structural schematic diagram of an embodiment of a head-up display system based on a two-dimensional geometric array waveguide according to the present invention; Figure 2 It is a schematic structural diagram of another embodiment of the head-up display system based on a two-dimensional geometric array waveguide according to the present invention; Figure 3 is a schematic diagram of light propagating on the first array waveguide; Figure 4 It is a schematic diagram of the principle based on the first array waveguide; Figure 5 It is a structural schematic diagram of Fresnel lens components; Figure 6This is a display diagram of the car windshield aberration corrected and not corrected.

[0018] Description of Figure Numbers: 1. Image generating unit; 2. First array waveguide; 21. Sub-prism; 211. First inclined surface; 212. Second inclined surface; 213. Upper surface; 214. Lower surface; 22. Upper end surface; 23. Lower end surface; 3. Second array waveguide; 4. Fresnel lens component; 41. First cylindrical Fresnel lens; 42. Second cylindrical Fresnel lens; 5. Automobile windshield.

[0019] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back...), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0022] In addition, the descriptions of "first", "second", etc. in the present invention are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, "and / or" in the full text includes three solutions. Taking A and / or B as an example, it includes technical solution A, technical solution B, and technical solution that satisfies both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, which must be based on the ability of ordinary technicians in the field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0023] The present invention proposes a head-up display system based on a two-dimensional geometric array waveguide.

[0024] In the embodiment of the present invention, Figures 1 to 6 As shown, the head-up display system based on the two-dimensional geometric array waveguide type includes an image generation unit 1 and an array waveguide; The arrayed waveguide comprises: A plurality of sub-prisms 21 arranged along a first direction, each of the sub-prisms 21 having a first inclined surface 211, a second inclined surface 212, an upper surface 213 and a lower surface 214; The plurality of upper surfaces 213 are sequentially connected to form the upper end surface 22 of the arrayed waveguide, and the plurality of lower surfaces 214 are sequentially connected to form the lower end surface 23 of the arrayed waveguide; A first preset angle is formed between the first inclined surface 211 and the lower end surface 23; A plurality of the first inclined surfaces 211 and a plurality of the second inclined surfaces 212 are alternately arranged along the first direction and are parallel to each other; The first inclined surface 211 of the first sub-prism 21 and the second inclined surface 212 of the last sub-prism 21 are both provided with total reflection films, and the first inclined surfaces 211 of the other sub-prisms 21 except the first sub-prism 21 are all provided with angle selective transmission reflection films; The light coupling-in area of ​​the array waveguide is arranged on the lower surface 214 of the first sub-prism 21, and the light coupling-out area is arranged on the upper end surface 22; wherein, The light generated by the image generating unit 1 enters the array waveguide through the light coupling-in area, and is reflected back and forth between the upper end surface 22 and the lower end surface 23 at a total reflection critical angle not less than that of the upper end surface 22 and the lower end surface 23 under the reflection of the total reflection film of the first sub-prism 21; The angle selectively transparent reflective film is configured to transmit part of the incident light and reflect the remaining incident light, and a part of the light reflected by the angle selectively transparent reflective film among all the angle selectively transparent reflective film is emitted toward the upper end surface 22 and transmitted through at a total reflection critical angle smaller than the upper end surface 22, and another part of the light reflected by the angle selectively transparent reflective film is emitted toward the lower end surface 23, and after being reflected at the lower end surface 23, is emitted toward the upper end surface 22 and transmitted through at a total reflection critical angle smaller than the upper end surface 22.

[0025] Specifically, the image generation unit 1 can be a thin-film transistor-liquid crystal display (TFT-LCD), a digital light processing (DLP), a liquid crystal on silicon (LCOS), a micro-light emitting diode display (Micro-LED), a micro holographic light engine, etc., and no specific limitation is made here.

[0026] The array waveguide is composed of a plurality of sub-prisms 21, which can be made of polymethylmethacrylate (PMMA) or optical glass. The surface of the sub-prism 21 is precisely processed, and the surface roughness is controlled at the nanometer level to ensure efficient light transmission. The size of the sub-prism 21 can be adjusted according to application requirements.

[0027] Total reflection films can be prepared by vacuum evaporation or magnetron sputtering. Common materials include aluminum, silver or gold, and dielectric multilayer films can also be used to improve reflectivity and durability. The film thickness can be set between tens and hundreds of nanometers. The preparation of angle-selective transmission reflective films requires precise control of their transmittance and reflectivity, which can be achieved by adjusting the film thickness or using different material combinations, such as partially transparent silver films or dielectric multilayer films.

[0028] The sub-prisms 21 are connected with optical grade ultraviolet (UV) curing glue, whose refractive index matches the material of the sub-prisms 21. After bonding, heat treatment or UV curing is performed to enhance the structural strength.

[0029] It should be noted that when light is emitted from a denser medium (with a larger refractive index) to a rarer medium (with a smaller refractive index), if the angle of incidence is greater than a certain specific angle, the light will not be able to pass through the interface between the two media and will be completely reflected back to the denser medium. This specific angle is called the critical angle of total reflection.

[0030] It is not difficult to understand that the head-up display system based on the two-dimensional geometric array waveguide described in the present invention gradually expands the display range in a limited space by multiple reflections and partial transmissions of the light in the waveguide, thereby obtaining a wider projection range without significantly increasing the volume of the system. The key lies in the reasonable design of the inclined surface of the sub-prism 21, and the arrangement of a total reflection film at the first and last sub-prisms 21 to maintain the efficient propagation of light, while arranging an angle selectively transparent reflection film at the middle sub-prism 21 to couple out part of the light in batches. Since the sub-prisms 21 are alternately arranged with each other in the same waveguide structure, each time the light encounters an inclined surface, it can be guided to perform total reflection or transmission, thereby extending the light path and gradually expanding in the horizontal and vertical directions, and finally forming a large display range.

[0031] Unlike traditional technologies that rely on large-volume reflector groups or additional multi-layer lenses to expand the display range, the present invention achieves efficient light coupling and expansion in the waveguide. Multiple reflections can avoid a large amount of scattering losses, and moderate transmission allows part of the light to be emitted at the best time, thereby significantly improving the visual range and imaging uniformity while keeping the overall system compact. Through the above arrangement, the technical bottleneck of the existing head-up display system that is difficult to achieve a larger display range due to volume limitations is effectively solved, laying a good foundation for providing a head-up display with a wide field of view and stable imaging quality in a limited cockpit space.

[0032] like Figure 3 As shown, the array waveguide is composed of a plurality of sub-prisms 21 assembled in sequence. S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, and S14 in the figure are all surfaces of the sub-prisms 21. Specifically, the odd-numbered surfaces S1, S3, S5, S7, S9, S11, and S13 are first inclined surfaces 211, and the even-numbered surfaces S2, S4, S6, S8, S10, S12, and S14 are second inclined surfaces 212. The first inclined surface 211 (i.e., S1) of the first sub-prism 21 of the array waveguide and the second inclined surface 212 (i.e., S14) of the last sub-prism 21 are provided with a total reflection film. Subsequently, the first inclined surfaces 211 (i.e., S3, S5, S7, S9, S11, and S13) of the other sub-prisms 21 except the first sub-prism 21 are all provided with an angle selective transmission reflection film.

[0033] In order to ensure the uniformity of the output light distribution and the consistency of the imaging brightness, multiple angle selective transmission reflective films need to be designed with different reflectivities and transmittances, so that the light can be reflected or transmitted according to the preset ratio when passing through each prism. Specifically, in the first direction, the reflectivity of the angle selective transmission reflective films coated on the S3, S5, S7, S9, S11, and S13 surfaces calculated according to the light intensity is The following relationship is satisfied: ; in, is the serial number of the angle selective transmission reflective film, and its value range is from 1 to M, where M is the total number of first inclined surfaces on which the angle selective transmission reflective film is provided in the array waveguide.

[0034] In such a geometric array structure, after light is coupled into the array waveguide, it is first held inside the waveguide at the total reflection film of the first sub-prism 21, and then encounters angle-selective transmission reflection films of different reflectivity in turn. Each interaction is partially transmitted and partially reflected according to the film layer design, and the light is gradually coupled out of the waveguide. Through the above-mentioned different reflectivity designs of the angle-selective transmission reflection films, the attenuation of light between the sub-prisms 21 can be distributed more reasonably, so that it will not be overly attenuated in the initial stage, and sufficient brightness can be ensured in the final stage.

[0035] like Figure 4 The figure shows a schematic diagram of the principle of array waveguide, the basic principle of which is that the central field of view light, the edge field of view light and the light sandwiched between the two light rays satisfy the law of total reflection, and can be totally reflected and propagated with the wall of the sub-prism 21 in the array waveguide. Because angle selective transmission reflective films with different reflectivities are coated between the sub-prisms 21, such as angle selective transmission reflective films are coated between the S2 surface of the sub-prism 21 and the S3 surface of the sub-prism 21. When light rays of various angles are incident on the surface where the angle selective transmission reflective film is located, light rays of different incident angles are either transmitted or reflected, and finally transmission of light rays of fixed light intensity and reflection of light rays of fixed light intensity are realized. By using the angle selective transmission reflective films with different reflectivities of the array, reflection of multiple incident light rays is realized, thereby realizing pupil expansion of the coupled light rays. In order to reduce stray light and enable the incident light rays to be totally reflected in the array waveguide, specifically, the first preset angle is ; The light generated by the image generation unit 1 has a predetermined viewing angle, and the half angle of the predetermined viewing angle is ; and The following relations are satisfied: ; ; ; ; in, is the refractive index of the array waveguide.

[0036] The present invention can be based on the refractive index n of the waveguide material and the required field of view angle. To reasonably set the first preset angle , and then obtain the best design solution that takes into account both full reflection efficiency and large display range coverage. For the head-up display system, under the condition of limited installation space, it is necessary to ensure that the light is reflected multiple times as much as possible to improve the utilization rate of light energy, and to ensure that the imaging range is wide enough to meet the driver's visual needs.

[0037] Optionally, the number of the arrayed waveguides is at least two, and all of the arrayed waveguides include a first arrayed waveguide 2 arranged along the first direction, and a second arrayed waveguide 3 arranged along a second direction perpendicular to the first direction, wherein: The light coupling-in region of the first arrayed waveguide 2 is connected to the image generating unit 1, and the light coupling-out region of the first arrayed waveguide 2 is connected to the light coupling-in region of the second arrayed waveguide 3, so that the light propagates and expands the pupil through the first arrayed waveguide 2 and the second arrayed waveguide 3 in sequence.

[0038] Specifically, the number of arrayed waveguides can be two, three, four, etc., and the sizes of the sub-prisms 21 of each arrayed waveguide can be set to be different, which is not limited here.

[0039] The present application takes the number of two arrayed waveguides as an example. During assembly, the assembly can be performed in the following order: in the first step, the end faces corresponding to the sub-prisms 21 of the first arrayed waveguide 2 and the second arrayed waveguide 3 are plated with angle-selective transmittance reflective films of corresponding reflectivity; in the second step, the plated sub-prisms 21 are glued to form the first arrayed waveguide 2 and the second arrayed waveguide 3; in the third step, the out-coupling region of the first arrayed waveguide 2 is matched with the in-coupling region of the second arrayed waveguide 3 and glued, and finally a two-dimensional geometric arrayed waveguide is formed.

[0040] Compared to arranging the sub-prism 21 or waveguide structure only in a single direction, by adding an additional array waveguide in the second direction, the light can be coupled and expanded in two orthogonal axes, respectively, so that the waveguide system that can only achieve one-dimensional linear expansion can be changed to perform two-dimensional expansion. Specifically, if the first array waveguide 2 is responsible for multiple reflections and transmissions of light in the horizontal direction, then the second array waveguide 3 vertically connected to it can continue to repeat the same process in the vertical direction or another orthogonal direction, thereby completing the coupling, compensation and emission of light in a larger range. In this way, the head-up display system can not only provide a wide image coverage in the horizontal direction, but also further increase the visible area in the vertical direction to meet the diversified display requirements of different models and driving needs. Especially in a limited installation space, the combination of these two levels of array waveguides can obtain a higher light energy utilization rate and a wider display range than a single-stage waveguide, significantly enhancing the adaptability and clarity of the head-up display in real road scenes.

[0041] Optionally, a car windshield 5 is arranged on the light emitting path of the second array waveguide 3, and a Fresnel lens component 4 is provided between the car windshield 5 and the second array waveguide 3, and the Fresnel lens component 4 is configured to compensate for the aberration introduced by the car windshield 5 in different directions.

[0042] When the light is emitted from the second arrayed waveguide 3 and needs to pass through the car windshield 5 before being projected into the driver's field of vision, if the shape of the windshield is non-planar or has an irregular curvature, the light will be distorted or deformed when passing through its interface. Through the additional Fresnel lens component 4, the aberration in the light can be corrected or corrected before entering the windshield, thereby ensuring that the image finally projected to the driver is still clear and distortion-free.

[0043] It is not difficult to understand that the introduction of the Fresnel lens component 4 can achieve effective compensation for the complex aberrations caused by the windshield curvature without changing the existing structure of the windshield, thereby ensuring that the large field of view is not seriously damaged by the curved surface distortion when projected into the driver's field of vision.

[0044] Specifically, the Fresnel lens component 4 includes a first cylindrical Fresnel lens 41 and a second cylindrical Fresnel lens 42, and the first cylindrical Fresnel lens 41 and the second cylindrical Fresnel lens 42 are stacked; The first cylindrical Fresnel lens 41 includes a first substrate and a first Fresnel structure disposed on the first substrate; The second cylindrical Fresnel lens 42 includes a second substrate and a second Fresnel structure disposed on the second substrate; The first Fresnel structure extends along a third direction, and the second Fresnel structure extends along a fourth direction perpendicular to the third direction.

[0045] Specifically, see Figure 5 The "Fresnel structure" refers to the disassembly of the continuous curved surface of a traditional convex lens or concave lens into multiple steps in the shape of rings or strips, and the realization of an optical focusing or diverging effect similar to a complete curved surface through multiple approximations; this can not only effectively reduce the thickness and weight of the lens, but also refract and correct the light in different directions as needed. For example, the first cylindrical Fresnel lens 41 and the second cylindrical Fresnel lens 42 can be cut or engraved in different directions to obtain a concave tooth-shaped or sawtooth-shaped Fresnel structure with different refractive powers in the horizontal and vertical directions, thereby reducing the assembly difficulty and optical cost when the two-dimensional waveguide is matched with the windshield.

[0046] In this solution, when the first cylindrical Fresnel lens 41 and the second cylindrical Fresnel lens 42 are stacked or closely fitted, the Fresnel structures extending along the third direction and the fourth direction respectively can correct aberrations of different dimensions. Since the windshield is not strictly uniaxially symmetrical, it is often necessary to consider the double curvature or aspherical components in the transverse and longitudinal directions: the first cylindrical Fresnel lens 41 is mainly responsible for correcting part of the aberration in the third direction; the second cylindrical Fresnel lens 42 is used to correct the distortion in the fourth direction perpendicular to the third direction. By processing the corresponding step-shaped or annular tooth structures on the two cylindrical Fresnel lenses respectively, the propagation path of the light beam in two orthogonal directions can be optimized while ensuring that the overall thickness of the lens is not large. This reduces the difficulty of manufacturing.

[0047] Specifically, the radial sections of the first Fresnel structure and the second Fresnel structure have the same sagittal height expression as the even-order aspheric surface, and the sagittal height expression is: ; in, is the base curvature coefficient, is the curvature, is the distance from the point on the aspherical surface to the optical axis, is the cone coefficient, is the aspheric coefficient; is the y coordinate of the point on the surface, The value of is 1 to 16.

[0048] This vector height expression indicates the description method of the aspheric free-form surface that can be shared and realized by the first Fresnel structure and the second Fresnel structure, so that the present invention has sufficient flexibility and accuracy when dealing with windshields, waveguide bonding and image distortion correction. In other words, under the premise of ensuring that the overall thickness of the lens or reflective surface is not too large, relying on this high-order aspheric polynomial correction, the aberration caused by complex curvature can be effectively reduced, allowing the head-up display to achieve a balance between a large display range and high imaging quality.

[0049] Optionally, the head-up display system based on the two-dimensional geometric array waveguide also includes a diffractive optical element, which is arranged at the exit pupil of the image generating unit 1 or the entrance pupil of the array waveguide, and is used to expand the optical extension, and the pixel size of the diffractive optical element is smaller than the pixel size of the spatial light modulator in the image generating unit 1.

[0050] Specifically, the principle of the diffractive optical element is to etch or emboss a multi-level diffraction structure (such as fine annular diffraction lines or two-dimensional gratings) on its surface, so that the incident light beam undergoes diffraction distribution or phase modulation when passing through the element, thereby achieving a larger diffusion angle or focusing ability at a relatively small physical size. Since its pixel size is much smaller than the spatial light modulator pixel commonly used in PGU, and can be optimized by neural network algorithms or other design methods, it can greatly increase the optical expansion at the exit pupil without significantly increasing the system volume.

[0051] Optionally, two adjacent sub-prisms 21 in the arrayed waveguide are fixed by bonding.

[0052] Specifically, the butt joint surfaces of adjacent sub-prisms 21 often need to fit tightly to ensure seamless transmission and reflection of light between the two prisms. Adopting optical glue, UV glue or other transparent polymer materials for bonding can not only ensure sufficient mechanical strength and stability, but also effectively control the refractive index transition at the joint, so that the interface between the sub-prisms 21 does not produce additional scattering or deflection. Through this bonding and fixing method, a continuous and stable light channel can be formed inside the array waveguide, so that multiple total reflections and angle-selective transmission and reflection processes can be carried out smoothly at the joints of adjacent sub-prisms 21, thereby maintaining the predetermined imaging quality and optical uniformity, and laying a solid foundation for designs such as windshield compensation or Fresnel lens correction.

[0053] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A head-up display system based on a two-dimensional geometric array waveguide, characterized in that: It comprises an image generating unit (1) and an array waveguide; The arrayed waveguide comprises: A plurality of sub-prisms (21) arranged along a first direction, each of the sub-prisms (21) having a first inclined surface (211), a second inclined surface (212), an upper surface (213) and a lower surface (214); A plurality of the upper surfaces (213) are sequentially connected to form an upper end surface (22) of the arrayed waveguide, and a plurality of the lower surfaces (214) are sequentially connected to form a lower end surface (23) of the arrayed waveguide; A first preset angle is formed between the first inclined surface (211) and the lower end surface (23); A plurality of the first inclined surfaces (211) and a plurality of the second inclined surfaces (212) are alternately arranged along the first direction and are parallel to each other; The first inclined surface (211) of the first sub-prism (21) and the second inclined surface (212) of the last sub-prism (21) are both provided with total reflection films, and the first inclined surfaces (211) of the other sub-prisms (21) except the first sub-prism (21) are all provided with angle selective transmission reflection films; The light coupling-in area of ​​the array waveguide is arranged on the lower surface (214) of the first sub-prism (21), and the light coupling-out area is arranged on the upper end surface (22); wherein, The light generated by the image generation unit (1) enters the array waveguide through the light coupling-in area, and is reflected back and forth between the upper end surface (22) and the lower end surface (23) at a total reflection critical angle not less than that of the upper end surface (22) and the lower end surface (23) under the reflection of the total reflection film of the first sub-prism (21); The angle selectively transmissive reflective film is configured to transmit part of the incident light and reflect the remaining incident light, wherein a part of the light reflected by the angle selectively transmissive reflective film among all the angle selectively transmissive reflective film is emitted toward the upper end surface (22) at a total reflection critical angle smaller than the upper end surface (22) and is transmitted out, and another part of the light reflected by the angle selectively transmissive reflective film is emitted toward the lower end surface (23), and after being reflected at the lower end surface (23), is emitted toward the upper end surface (22) at a total reflection critical angle smaller than the upper end surface (22) and is transmitted out.

2. The head-up display system based on a two-dimensional geometric array waveguide according to claim 1, characterized in that: In the first direction, the reflectivity of the angle selective transmission reflective film is The following relationship is satisfied: ； in, is the serial number of the angle selective transmission reflective film, and has a value range of 1 to M, where M is the total number of first inclined surfaces (211) provided with the angle selective transmission reflective film in the array waveguide.

3. The head-up display system based on a two-dimensional geometric array waveguide according to claim 1, characterized in that: The first preset angle is ; The light generated by the image generation unit (1) has a predetermined viewing angle, and the half angle of the predetermined viewing angle is ; and The following relations are satisfied: ； ； ； ； in, is the refractive index of the array waveguide.

4. The head-up display system based on a two-dimensional geometric array waveguide according to claim 1, characterized in that: The number of the arrayed waveguides is at least two, and all of the arrayed waveguides include a first arrayed waveguide (2) arranged along the first direction, and a second arrayed waveguide (3) arranged along a second direction perpendicular to the first direction, wherein: The light coupling-in region of the first arrayed waveguide (2) is connected to the image generating unit (1), and the light coupling-out region of the first arrayed waveguide (2) is connected to the light coupling-in region of the second arrayed waveguide (3), so that light is propagated and pupil expanded through the first arrayed waveguide (2) and the second arrayed waveguide (3) in sequence.

5. The head-up display system based on a two-dimensional geometric array waveguide according to claim 4, characterized in that: The automobile windshield (5) is arranged on the light emission path of the second array waveguide (3), and a Fresnel lens component (4) is arranged between the automobile windshield (5) and the second array waveguide (3), wherein the Fresnel lens component (4) is configured to compensate for aberrations introduced by the automobile windshield (5) in different directions.

6. The head-up display system based on a two-dimensional geometric array waveguide according to claim 5, characterized in that: The Fresnel lens component (4) comprises a first cylindrical Fresnel lens (41) and a second cylindrical Fresnel lens (42), wherein the first cylindrical Fresnel lens (41) and the second cylindrical Fresnel lens (42) are stacked; The first cylindrical Fresnel lens (41) comprises a first substrate and a first Fresnel structure arranged on the first substrate; The second cylindrical Fresnel lens (42) comprises a second substrate and a second Fresnel structure arranged on the second substrate; The first Fresnel structure extends along a third direction, and the second Fresnel structure extends along a fourth direction perpendicular to the third direction.

7. The head-up display system based on a two-dimensional geometric array waveguide according to claim 6, characterized in that: The radial sections of the first Fresnel structure and the second Fresnel structure have the same sagittal height expression as the even-order aspheric surface, and the sagittal height expression is: ； in, is the base curvature coefficient, is the curvature, is the distance from the point on the aspherical surface to the optical axis, is the cone coefficient, is the aspheric coefficient; is the y coordinate of the point on the surface, The value of is 1 to 16.

8. The head-up display system based on a two-dimensional geometric array waveguide according to claim 1, characterized in that: The head-up display system based on a two-dimensional geometric array waveguide also includes a diffractive optical element, which is arranged at an exit pupil of the image generation unit (1) or an entrance pupil of the array waveguide, and is used to expand the optical extension, and the pixel size of the diffractive optical element is smaller than the pixel size of the spatial light modulator in the image generation unit (1).

9. The head-up display system based on a two-dimensional geometric array waveguide according to claim 1, characterized in that: Two adjacent sub-prisms (21) in the array waveguide are fixed by bonding.

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