Compact optical waveguide HUD system and oblique light emitting angle determination method thereof

Abstract

The invention discloses a compact optical waveguide HUD system and an inclined light emitting angle determination method thereof, and relates to the technical field of vehicle-mounted display optical systems.The compact optical waveguide HUD system comprises an optical waveguide assembly, a compensating mirror assembly and vehicle windshield glass, the left-right direction of a vehicle is the Y direction, the longitudinal direction of the vehicle is the Z direction, and the windshield glass has curvature in the Y direction; the optical waveguide assembly is configured to be of an inclined light emitting structure to emit light, and the inclined light emitting structure enables the light to leave the optical waveguide assembly in the direction inclined relative to the normal of the light emitting face of the optical waveguide assembly and to have a direction component in the Y direction. The emergent light has direction components in the left-right direction of the vehicle when leaving the optical waveguide, so that a posture inclination compensation mechanism of a system in the left-right direction of the vehicle is replaced, and light path turning is completed in cooperation with a compensation mirror so as to compress the longitudinal Z-direction packaging height of the vehicle.

Description

Technical Field

[0001] This invention relates to the field of automotive display optical system technology, specifically to a compact optical waveguide HUD system and a method for determining the oblique beam angle. Background Technology

[0002] Head-up display (HUD) systems are used to present image information as a virtual image in front of the driver's field of vision. Their optical systems typically include optical components related to optical path deflection and imaging, as well as the vehicle's windshield. Due to their thinness and compact structure, waveguide HUDs are gradually becoming one of the important implementation methods for automotive HUDs.

[0003] In some vehicle models, the windshield has curvature along the left and right directions of the vehicle. This curvature causes the HUD light to be deflected in the left and right directions of the vehicle. In the architecture that uses light waves to guide the light and then refracts it through a compensating mirror before it is incident on the windshield, in order to meet the incident and reflection conditions of the windshield, the system structure usually needs to introduce a certain attitude relationship in the left and right directions of the vehicle to complete the matching and refraction of the light direction.

[0004] Given that the windshield has curvature along the left and right directions of the vehicle, thus introducing HUD light that is equivalently deflected in the left and right directions of the vehicle, how can we meet the windshield incident conditions without causing the HUD system as a whole to tilt significantly in the left and right directions of the vehicle, and further achieve spatial compression of the HUD system in the longitudinal Z direction of the vehicle, so as to improve the layout adaptability and space utilization under the limited space conditions inside the vehicle?

[0005] Furthermore, in some vehicle models, the windshield exhibits an incident condition offset due to changes in mounting angle and / or curvature along the vehicle's vertical direction. Factors such as the driver's eye level and the vertical offset of the field of view further enhance the sensitivity of the HUD light incident on the vehicle's vertical direction. To meet the windshield's incident and reflection conditions in the vehicle's vertical direction, the system's engineering design may incorporate adjustments to the vehicle's vertical orientation, thus imposing further constraints on the system's compact packaging. Summary of the Invention

[0006] The purpose of this invention is to provide a compact optical waveguide HUD system and a method for determining the oblique beam output angle, so as to solve the problems mentioned in the background art.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a compact optical waveguide HUD system, comprising an optical waveguide assembly, a compensation mirror assembly, and a vehicle windshield, wherein the left-right direction of the vehicle is the Y direction and the longitudinal direction of the vehicle is the Z direction, and the windshield has curvature in the Y direction; characterized in that: the optical waveguide assembly is configured as an oblique light-emitting structure to emit light rays, the oblique light-emitting structure causing the light rays to leave the optical waveguide assembly in a direction inclined relative to the normal of the light-emitting surface of the optical waveguide assembly and having a directional component along the Y direction, the angle between the emission direction and the normal of the light-emitting surface is defined as the oblique light-emitting angle; The compensation mirror assembly is configured to receive light rays emitted obliquely through the optical waveguide assembly, refract the light path, and project the light rays onto the windshield, so that the light rays are reflected by the windshield and enter the human eye to form a virtual image. Wherein, under the condition that the windshield has curvature along the Y direction, causing the HUD light to have an equivalent deflection in the Y direction, the oblique light-emitting structure of the optical waveguide component enables the light to obtain the directional component along the Y direction before it is incident on the compensation mirror assembly and the windshield. Thus, under the premise of satisfying the incident condition of the windshield along the Y direction, it is not necessary for the compensation mirror assembly and / or the entire vehicle head-up display system to produce an attitude tilt along the Y direction to compensate for the curvature, and the packaging height of the system in the Z direction can be reduced.

[0008] According to the above technical solution, the oblique light emission angle is within a preset angle range, which is determined by the curvature parameter of the windshield in the Y direction, the structural dimensions between the optical waveguide assembly and the compensation mirror assembly, and the optical path deflection requirements. The lower limit of the preset angle range is determined by whether the windshield incident conditions can be met without the system or the compensation mirror assembly tilting along the Y direction. The upper limit of the preset angle range is limited by the system imaging quality and the emission efficiency of the optical waveguide assembly. The oblique light emission angle in the Y direction is no greater than 20°.

[0009] According to the above technical solution, the compensation mirror assembly is a folding optical assembly composed of one or more concave lenses, convex lenses or freeform mirrors, used to complete the optical path folding and make the light meet the incident conditions of the windshield glass without the need to tilt along the Y direction.

[0010] According to the above technical solution, the optical waveguide assembly and the compensation mirror assembly are arranged at intervals along the optical axis; and the tilt angle between the vehicle head-up display system and the IP reference plane is less than 10°.

[0011] According to the above technical solution, under the premise that the HUD light has a tilt angle relative to the vehicle Y direction due to the same left and right curvature of the windshield, by configuring the optical waveguide component as an oblique light output structure and making the light incident on the compensation mirror component at a predetermined angle, the space occupied by the system in the longitudinal Z direction of the vehicle is significantly reduced, and the Z-direction height of the system is reduced to 51.78mm.

[0012] A method for determining the oblique beam exit angle of a compact optical waveguide HUD includes the following steps: S1, under the premise that the windshield has curvature along the Y direction, set system design constraints, the system design constraints include at least: not allowing the windshield curvature to be compensated by the overall tilt of the vehicle head-up display system along the Y direction, minimizing the space occupation in the Z direction while meeting the windshield incident conditions, and system imaging quality requirements. S2, a preset oblique light emission angle range is determined based on the curvature parameter of the windshield in the Y direction, the structural dimensions between the optical waveguide assembly and the compensation mirror assembly, and the optical path deflection requirements. The lower limit of the preset oblique light emission angle range is determined by whether the windshield incident conditions can be met without the system or the compensation mirror assembly being tilted in the Y direction. The upper limit of the preset oblique light emission angle range is limited by the system imaging quality and the emission efficiency of the optical waveguide assembly. S3, select multiple candidate oblique light emission angles within the preset oblique light emission angle range and use them for oblique light emission of the optical waveguide component respectively. For each candidate oblique light emission angle, evaluate the system imaging quality based on the corresponding optical path structure. When the system imaging quality under a certain candidate oblique light emission angle does not meet the system design constraints, the candidate oblique light emission angle is determined to be infeasible and is eliminated. S4. Determine the target oblique emission angle for the optical waveguide assembly from the candidate oblique emission angles that have passed the imaging quality evaluation, so that the system can meet both the windshield incident conditions and the system imaging quality requirements without having to tilt along the Y direction.

[0013] According to the above technical solution, the system imaging quality evaluation includes parallelism evaluation and distortion evaluation. Parallelism is used to characterize the consistency of imaging direction at different eye points within the preset driver eye box range. Specifically, it calculates the outgoing direction of light at different eye points for the same field of view incident conditions, and uses the angle difference between the light directions corresponding to different eye points as the parallelism evaluation index. Distortion is used to characterize the degree of deviation between the actual virtual image obtained from the imaging process and the ideal virtual image. The distortion is defined as the relative deviation value between the actual virtual image and the ideal virtual image, where the ideal virtual image is the virtual image obtained under the design reference imaging plane or reference imaging state. When both parallelism and distortion meet the preset thresholds, the corresponding oblique light exit angle is considered to meet the imaging quality requirements. The preset thresholds include parallelism less than 0.2° and distortion less than 5%.

[0014] According to the above technical solution, the imaging quality evaluation is based on the worst eye point within the eyebox range. Specifically, multiple discrete eye points are selected in a grid pattern within the preset eyebox range, and sampling points are selected in the left-right direction and the up-down direction of the vehicle to form a two-dimensional distributed eye point set. For each eye point in the eye point set, its corresponding imaging quality index is calculated, including at least parallelism and distortion. The eye point in the eye point set whose imaging quality index deviates the most from the preset requirement is determined as the worst eye point, and the imaging quality at the worst eye point is used as the criterion for evaluating whether the corresponding oblique light emission angle is feasible, ensuring that the system has acceptable imaging quality throughout the entire eyebox range.

[0015] A compact optical waveguide vehicle head-up display system includes an optical waveguide assembly, a compensation mirror assembly, and a vehicle windshield, wherein the vehicle's left-right direction is the Y-axis, the vehicle's longitudinal direction is the Z-axis, and the vehicle's vertical direction is the X-axis; characterized in that: the local normal direction of the windshield is deflected relative to the vehicle coordinate system in the vehicle's vertical X-axis. The optical waveguide assembly is configured as an oblique light-emitting structure to emit light rays, such that the emitted light rays leave the optical waveguide assembly in a direction inclined relative to the normal of the light-emitting surface of the optical waveguide assembly and have a directional component along the X direction, and the angle between the emission direction and the normal of the light-emitting surface is defined as the oblique light-emitting angle in the X direction. The compensation mirror assembly is configured to receive light rays emitted obliquely through the optical waveguide assembly, refract the light path, and project the light rays onto the windshield, so that the light rays are reflected by the windshield and enter the human eye to form a virtual image. Wherein, under the condition that the incident condition of the windshield is biased, causing the HUD light to be effectively deflected in the X direction, the X-direction oblique light-ejection structure of the optical waveguide component enables the light to obtain the directional component along the X direction before it is incident on the compensation mirror assembly and the windshield. Thus, under the premise that the incident condition of the windshield along the X direction is satisfied, it is not necessary for the compensation mirror assembly and / or the entire vehicle head-up display system to generate an attitude tilt along the X direction to compensate for the curvature.

[0016] According to the above technical solution, the X-axis oblique light emission angle is no greater than 50°.

[0017] Compared with existing technologies, the beneficial effects achieved by this invention are as follows: This invention introduces the lateral component of the vehicle into the optical path front end through an oblique light emission method using an optical waveguide, achieving pre-compensation for the equivalent deflection caused by the windshield curvature. This allows the compensation mirror assembly to complete the optical path deflection and meet the windshield incident conditions without tilting along the lateral direction of the vehicle, thereby reducing the overall system packaging height in the longitudinal Z-direction of the vehicle. Simultaneously, a method for selecting and determining the oblique light emission angle is proposed, determining the target oblique light emission angle while meeting imaging quality constraints (e.g., parallelism and distortion threshold), enabling the system to possess both structural compactness and adaptability to different vehicle models / windshield curvatures. Furthermore, this invention can also configure the optical waveguide assembly as an oblique light emission structure in the vertical direction of the vehicle, so that the emitted light has a lateral component in the vertical direction of the vehicle when leaving the optical waveguide assembly. Therefore, even when the windshield has an incident condition offset along the vertical direction of the vehicle, the windshield incident conditions can be met without tilting the system along the vertical direction of the vehicle, improving the adaptability to different vehicle models and different driver eye point heights, and further enhancing the system's compact packaging capability. Attached Figure Description

[0018] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a diagram of a conventional vertical beam-emitting architecture; Figure 2 This is the main architecture diagram of the system structure of the present invention; Figure 3 This is an evaluation caliber diagram of the method for determining the oblique light emission angle of the present invention; Figure 4 , Figure 5 This is a diagram illustrating the differences in the Z-axis packaging height between the comparative embodiments and the embodiments of the present invention; Figure 6 This is a schematic diagram of the optical path of the X-axis oblique-out optical waveguide HUD system of the present invention in the X–Z section; Figure 7 This is a schematic diagram illustrating the definition of the X-axis oblique light output angle and its relationship with the system's principal ray reference direction. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] like Figure 1 As shown, in a conventional optical waveguide HUD architecture, the optical waveguide adopts a vertical light-emitting structure. The light rays are emitted vertically and incident on the compensation mirror, then projected onto the windshield and reflected to the human eye. Under this structure, the light rays do not have a directional component along the left and right directions of the vehicle when they leave the optical waveguide. In order to meet the windshield incident conditions, the system usually compensates by tilting the compensation mirror and the entire system along the left and right directions of the vehicle.

[0021] Under the aforementioned engineering constraints, if the vertical light output method is still adopted, the path of compensating by the attitude tilt of the entire system along the left and right directions of the vehicle will directly lead to an increase in the Z-direction packaging height, making it difficult for the traditional vertical light output waveguide structure to meet the overall system design requirements. Therefore, it is necessary to start from the source of the optical path and introduce the directional component along the left and right directions of the vehicle into the optical path before the light is incident on the compensation mirror and the windshield.

[0022] Please see Figures 1-5 The present invention provides a technical solution: a compact optical waveguide HUD system, comprising an optical waveguide assembly, a compensation mirror assembly, and a vehicle windshield, wherein the vehicle's left-right direction is the Y direction and the vehicle's longitudinal direction is the Z direction, and the windshield has curvature in the Y direction; characterized in that: the optical waveguide assembly is configured as an oblique light-emitting structure to emit light rays, the oblique light-emitting structure causing the light rays to leave the optical waveguide assembly in a direction inclined relative to the normal of the light-emitting surface of the optical waveguide assembly and having a directional component along the Y direction, the angle between the emission direction and the normal of the light-emitting surface is defined as the oblique light-emitting angle; The compensating mirror assembly is configured to receive light rays emitted obliquely from the optical waveguide assembly, refract the light path, and project the light rays onto the windshield, so that the light rays are reflected by the windshield and enter the human eye to form a virtual image. In this system, under the condition that the windshield has curvature along the Y direction, causing the HUD light to be effectively deflected in the Y direction, the oblique light-emitting structure of the optical waveguide component allows the light to obtain the Y-direction directional component before it is incident on the compensation mirror component and the windshield. Thus, under the premise of satisfying the incident condition of the windshield along the Y direction, it is not necessary to make the compensation mirror component and / or the entire vehicle head-up display system tilted in the Y direction to compensate for the curvature, and the packaging height of the system in the Z direction can be reduced. The angle of the oblique light output is within a preset angle range, which is determined by the curvature parameters of the windshield in the Y direction, the structural dimensions between the optical waveguide assembly and the compensation mirror assembly, and the optical path deflection requirements. The lower limit of the preset angle range is determined by whether the windshield incident conditions can be met without the system or compensation mirror assembly tilting along the Y direction. The upper limit of the preset angle range is limited by the system imaging quality and the output efficiency of the optical waveguide assembly; and the Y-direction oblique light output angle is no greater than 20°. The compensating mirror assembly is a folding optical assembly consisting of one or more concave lenses, convex lenses or freeform mirrors, used to complete the optical path folding and make the light meet the incident conditions of the windshield without the need for attitude tilting along the Y direction. The optical waveguide assembly and the compensation mirror assembly are arranged at intervals along the optical axis; and the tilt angle between the vehicle head-up display system and the IP reference plane is less than 10°. Under the premise that the HUD light has a tilt angle relative to the vehicle in the Y direction due to the same left and right curvature of the windshield, by configuring the optical waveguide component as an oblique light output structure and making the light incident on the compensation mirror component at a predetermined angle, the space occupied by the system in the longitudinal Z direction of the vehicle is significantly reduced, and the height of the system in the Z direction is reduced to 51.78mm. like Figure 2 As shown, the present invention configures the optical waveguide as an oblique light-emitting structure, so that the light rays leave the optical waveguide assembly in a direction that is inclined relative to the normal of the light-emitting surface of the optical waveguide assembly; the light rays that are obliquely emitted from the optical waveguide assembly are incident on the compensation mirror assembly, the compensation mirror assembly refracts the light path and projects it onto the windshield, and the light rays are reflected by the windshield and enter the human eye to form a virtual image.

[0023] The implementation logic of this invention is as follows: since the light has a directional component along the left and right direction of the vehicle when it leaves the optical waveguide component, the compensation mirror component can complete the optical path deflection and meet the incident conditions of the windshield without tilting its attitude along the left and right direction of the vehicle. As a result, the system as a whole does not need to tilt its attitude in the left and right direction of the vehicle, and its packaging height in the longitudinal Z direction of the vehicle is effectively reduced.

[0024] A method for determining the oblique beam exit angle of a compact optical waveguide HUD includes the following steps: S1. Under the premise that the windshield has curvature along the Y direction, set system design constraints. The system design constraints include at least: not allowing the windshield curvature to be compensated by the overall tilt of the vehicle head-up display system along the Y direction; minimizing the space occupation in the Z direction while meeting the windshield incident conditions; and system imaging quality requirements. S2, the preset oblique light emission angle range is determined based on the curvature parameters of the windshield in the Y direction, the structural dimensions between the optical waveguide assembly and the compensation mirror assembly, and the optical path folding requirements. The lower limit of the preset oblique light emission angle range is determined by whether the windshield incident conditions can be met without the system or compensation mirror assembly tilting in the Y direction. The upper limit of the preset oblique light emission angle range is limited by the system imaging quality and the emission efficiency of the optical waveguide assembly. S3. Select multiple candidate oblique light emission angles within the preset oblique light emission angle range and use them for oblique light emission of the optical waveguide component. Evaluate the system imaging quality based on the corresponding optical path structure for each candidate oblique light emission angle. If the system imaging quality under a certain candidate oblique light emission angle does not meet the system design constraints, the candidate oblique light emission angle is determined to be infeasible and is eliminated. S4. Determine the target oblique exit angle for the optical waveguide component from the candidate oblique exit angles that have passed the imaging quality evaluation, so that the system can meet both the windshield incident conditions and the system imaging quality requirements without needing to generate attitude tilt along the Y direction. The system imaging quality evaluation includes parallelism evaluation and distortion evaluation. Parallelism is used to characterize the consistency of the imaging direction at different eye points within the preset driver eye box range. Specifically, it calculates the exit direction of light at different eye points for the same field of view incident conditions, and uses the angle difference between the corresponding light directions at different eye points as the parallelism evaluation index. Distortion is used to characterize the degree of deviation between the actual virtual image obtained from the imaging process and the ideal virtual image. Distortion is defined as the relative deviation value between the actual virtual image and the ideal virtual image, where the ideal virtual image is the virtual image obtained under the design reference imaging plane or reference imaging state. When both parallelism and distortion meet the preset thresholds, the corresponding oblique light exit angle is considered to meet the imaging quality requirements. The preset thresholds include parallelism less than 0.2° and distortion less than 5%.

[0025] Imaging quality evaluation is based on the worst eye point within the eyebox range. Specifically, multiple discrete eye points are selected in a grid pattern within the preset eyebox range, and sampling points are selected in the left-right direction and the up-down direction of the vehicle to form a two-dimensional distribution set of eye points. For each eye point in the set of eye points, its corresponding imaging quality index is calculated, including at least parallelism and distortion. The eye point in the set of eye points with the largest deviation from the preset requirements is determined as the worst eye point, and the imaging quality at the worst eye point is used as the criterion for evaluating whether the corresponding oblique light emission angle is feasible, ensuring that the system has acceptable imaging quality throughout the entire eyebox range.

[0026] Based on the above device structure, in order to ensure that the system has good imaging quality while meeting the windshield incident conditions, it is necessary to reasonably determine the oblique light exit angle of the optical waveguide.

[0027] like Figure 3 As shown, firstly, multiple candidate oblique light emission angles are selected within a preset angle range for oblique light emission of the optical waveguide component; the preset angle range is determined based on the windshield curvature parameters, system structure dimensions, and optical path deflection requirements.

[0028] The lower limit of the oblique light emission angle is determined by whether the windshield incident conditions can be met without the system or compensation mirror tilting along the left and right directions of the vehicle. When the oblique light emission angle is too small, the left and right direction components of the light after leaving the optical waveguide are insufficient, and the system still needs to compensate by tilting the attitude.

[0029] The upper limit of the oblique light emission angle is limited by the system's imaging quality and light waveguide emission efficiency; when the oblique light emission angle is too large, it may lead to problems such as deterioration of imaging quality or decrease in light energy utilization.

[0030] In engineering practice, further examples of magnitude are given: For instance, when the radius of curvature of a car windshield in the left and right directions is at the minimum level commonly found in vehicles (such as about 3000), based on the engineering geometric relationship between the windshield curvature and the local normal deflection, it can be deduced that when light leaves the optical waveguide, it needs to have a certain magnitude of the left and right direction component of the vehicle, and the corresponding oblique light exit angle usually needs to reach about 10°; this value is only used to illustrate the relationship between the oblique light exit angle and engineering constraints, and does not constitute a limitation on the scope of protection.

[0031] For each candidate oblique exit angle, the system imaging quality is evaluated based on the corresponding optical path structure. When the system imaging quality at a certain candidate oblique exit angle does not meet the preset requirements, the candidate oblique exit angle is determined to be infeasible and eliminated. Among the candidate oblique exit angles that have passed the imaging quality evaluation, the target oblique exit angle for the optical waveguide component is determined so that the system can meet both the windshield incident conditions and the system imaging quality requirements without tilting the vehicle in the left and right directions.

[0032] In the process of selecting oblique light exit angles, the imaging quality evaluation indicators provided by this invention include parallelism and distortion: parallelism is used to characterize the consistency of imaging direction at different eye points within the eye box range. Specifically, within a preset driver eye box range (e.g., 130×50), the light exit direction at different eye points is calculated for the same field of view incident conditions, and the angle difference between the corresponding light directions at different eye points is used as the parallelism evaluation index; distortion is used to characterize the degree of deviation between the actual virtual image and the ideal virtual image. Distortion is defined as the relative deviation value between the actual virtual image and the ideal virtual image, where the ideal virtual image is the virtual image obtained under the design reference imaging plane or reference imaging state; when both parallelism and distortion meet the preset thresholds (e.g., parallelism less than 0.2°, distortion less than 5%), the corresponding oblique light exit angle is considered to meet the imaging quality requirements.

[0033] To ensure acceptable imaging quality throughout the entire eyebox area, this invention further specifies that the worst eye point is used as the evaluation criterion: multiple discrete eye points are selected in a grid pattern within the preset eyebox area, for example, multiple sampling points are selected in the left-right direction and the up-down direction of the vehicle to form a two-dimensional distributed eye point set; for each eye point in the eye point set, its imaging quality index (including parallelism and distortion) is calculated; in the eye point set, the eye point whose imaging quality index deviates the most from the preset requirement is determined as the worst eye point, and the imaging quality at the worst eye point is used as the criterion for evaluating whether the corresponding oblique light emission angle is feasible.

[0034] In specific embodiments, the present invention provides comparative verification: such as Figure 4 As shown, when the curvature of the windshield causes the light to tilt relative to the vehicle in the Y direction, when using a traditional optical waveguide vertical light output structure, the optical waveguide vertically outputs light into the compensation mirror. In order to meet the windshield incident conditions, the compensation mirror and the entire system are forced to be tilted in the Y direction, resulting in the system occupying a large space in the longitudinal Z direction of the vehicle. In this embodiment, the height of the system in the Z direction is 106.79mm.

[0035] like Figure 5 As shown, under the premise that the light rays are tilted relative to the vehicle in the Y direction due to the same curvature of the windshield, the present invention configures the optical waveguide as an oblique light-emitting structure so that the light rays are incident on the compensation mirror at a predetermined angle. The system can meet the windshield incident conditions while significantly reducing the space occupied by the system in the longitudinal Z direction of the vehicle. The Z-direction height of the system is reduced to 51.78mm.

[0036] As can be seen from the above comparison, under the condition that the curvature of the windshield causes the HUD light to be effectively deflected in the left and right directions of the vehicle, if the light output method of the optical waveguide is not changed, the overall system will inevitably tilt in the left and right directions of the vehicle, resulting in the system occupying a large space in the Z direction. The present invention, through the optical waveguide oblique light output structure and the method for determining the oblique light output angle, enables the system to achieve significant compression of the Z-direction space of the optical waveguide HUD system while meeting the system imaging quality requirements.

[0037] A compact optical waveguide vehicle head-up display system includes an optical waveguide assembly, a compensation mirror assembly, and a vehicle windshield, wherein the vehicle's left-right direction is the Y direction, the vehicle's longitudinal direction is the Z direction, and the vehicle's vertical direction is the X direction; the local normal direction of the windshield is deflected relative to the vehicle coordinate system in the vehicle's vertical X direction. The optical waveguide assembly is configured as an oblique light-emitting structure to emit light rays, such that the emitted light rays leave the optical waveguide assembly in a direction inclined relative to the normal of the light-emitting surface of the optical waveguide assembly and have a directional component along the X direction. The angle between the emission direction and the normal of the light-emitting surface is defined as the oblique light-emitting angle in the X direction. The compensation mirror assembly is configured to receive light rays emitted obliquely through the optical waveguide assembly, refract the light path, and project the light rays onto the windshield, so that the light rays are reflected by the windshield and enter the human eye to form a virtual image; Wherein, under the condition that the windshield has the aforementioned incident condition bias, causing the HUD light to have an equivalent deflection in the X direction, the X-direction oblique light output structure of the optical waveguide component allows the light to obtain the X-direction directional component before it is incident on the compensation mirror assembly and the windshield. Thus, under the premise of satisfying the incident condition of the windshield in the X direction, it is not necessary for the compensation mirror assembly and / or the entire vehicle head-up display system to produce an attitude tilt in the X direction for compensating curvature.

[0038] The X-axis oblique beam exit angle is no greater than 50°, and its upper limit is limited by the system imaging quality and the emission efficiency of the optical waveguide components.

[0039] In another embodiment, such as Figure 6 As shown, to adapt to the incident conditions of the windshield in the vertical direction of the vehicle (e.g., caused by the installation tilt angle and / or curvature) and meet the corresponding incident requirements, the optical waveguide assembly is configured as an X-axis oblique light-emitting structure under the packaging constraint that the entire system is not allowed to tilt in the vertical direction of the vehicle. Specifically, the light enters the optical waveguide assembly after being deflected by the compensation mirror assembly and propagates in the optical waveguide assembly, and then exits obliquely from the light-emitting surface of the optical waveguide assembly. The difference from the previous implementation is that the emitted light in this implementation has a directional component in the vertical direction of the vehicle when it leaves the optical waveguide assembly, thereby achieving directional pre-compensation in the vertical direction of the vehicle before it is incident on the windshield. This allows the light to meet the incident conditions of the windshield in the vertical direction of the vehicle without the system needing to tilt in the vertical direction of the vehicle, and then enters the human eye through reflection from the windshield to form a virtual image.

[0040] like Figure 7 As shown, the vertical direction of the vehicle is defined as the X-axis, and the longitudinal direction is defined as the Z-axis. Within the X-Z cross-section, an angular relationship can be established between the reference direction of the optical waveguide assembly (e.g., the mounting reference direction or the normal direction of the light-emitting surface) and the reference direction of the system's principal ray. The angle between the emitted ray direction and the reference direction in the X-Z plane represents the X-axis oblique light emission angle. Since the curvature parameters of the windshield in the vertical direction of the vehicle, the system structural dimensions, and the optical path reversal requirements differ from those in the horizontal direction of the vehicle, the preset candidate range for the X-axis oblique light emission angle is usually different from the candidate range for the Y-axis oblique light emission angle. In actual engineering design, the candidate range for the X-axis oblique light emission angle can be determined based on the curvature parameters of the windshield in the vertical direction of the vehicle, the structural dimensions between the optical waveguide and the compensation mirror, and the reversal requirements. The target angle that meets the imaging quality requirements can then be selected from the candidate angles.

[0041] During the selection process of the X-axis oblique light emission angle, the imaging quality evaluation criteria can be consistent with the aforementioned implementation method. Parallelism and distortion can still be used as evaluation indicators, and the worst eye point within the eye box range can be used as the criterion to ensure that the imaging quality is acceptable throughout the entire eye box range. The main difference between the X-axis scheme and the Y-axis scheme lies in the different meanings of the oblique light emission direction, the candidate range of the angle, and the upper and lower limits constrained by the windshield curvature parameters, while the evaluation indicators and their criteria remain consistent.

[0042] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "include," "contain," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0043] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A compact optical waveguide HUD system, comprising an optical waveguide assembly, a compensation mirror assembly, and a vehicle windshield, wherein the vehicle's left-right direction is the Y-axis and the vehicle's longitudinal direction is the Z-axis, and the windshield has curvature in the Y-axis; characterized in that: The optical waveguide assembly is configured as an oblique light-emitting structure to emit light rays. The oblique light-emitting structure causes the light rays to leave the optical waveguide assembly in a direction that is inclined relative to the normal of the light-emitting surface of the optical waveguide assembly and has a directional component along the Y direction. The angle between the emission direction and the normal of the light-emitting surface is defined as the oblique light-emitting angle. The compensation mirror assembly is configured to receive light rays emitted obliquely through the optical waveguide assembly, refract the light path, and project the light rays onto the windshield, so that the light rays are reflected by the windshield and enter the human eye to form a virtual image. Wherein, under the condition that the windshield has curvature along the Y direction, causing the HUD light to have an equivalent deflection in the Y direction, the oblique light-emitting structure of the optical waveguide component enables the light to obtain the directional component along the Y direction before it is incident on the compensation mirror assembly and the windshield. Thus, under the premise of satisfying the incident condition of the windshield along the Y direction, it is not necessary for the compensation mirror assembly and / or the entire vehicle head-up display system to produce an attitude tilt along the Y direction to compensate for the curvature, and the packaging height of the system in the Z direction can be reduced.

2. The compact optical waveguide HUD system according to claim 1, characterized in that: The angle of the oblique light emission is within a preset angle range, which is determined based on the curvature parameter of the windshield in the Y direction, the structural dimensions between the optical waveguide assembly and the compensation mirror assembly, and the optical path deflection requirements. The lower limit of the preset angle range is determined by whether the windshield incident conditions can be met without the system or the compensation mirror assembly tilting along the Y direction. The upper limit of the preset angle range is limited by the system imaging quality and the emission efficiency of the optical waveguide assembly. The oblique light emission angle in the Y direction is no greater than 20°.

3. A compact optical waveguide HUD system according to claim 2, characterized in that: The compensation mirror assembly is a folding optical assembly consisting of one or more concave lenses, convex lenses, or freeform mirrors, used to complete the optical path folding and ensure that the light meets the incident conditions of the windshield without requiring attitude tilting along the Y direction.

4. A compact optical waveguide HUD system according to claim 3, characterized in that: The optical waveguide assembly and the compensation mirror assembly are arranged at intervals along the optical axis; and the tilt angle between the vehicle head-up display system and the IP reference plane is less than 10°.

5. A compact optical waveguide HUD system according to claim 4, characterized in that: Given that the HUD light has a tilt angle relative to the vehicle's Y-axis due to the same left and right curvature of the windshield, by configuring the optical waveguide assembly as an oblique light-emitting structure and causing the light to be incident on the compensation mirror assembly at a predetermined angle, the space occupied by the system in the vehicle's longitudinal Z-axis direction is reduced.

6. The method for determining the oblique beam exit angle of a compact optical waveguide HUD according to any one of claims 1-5, characterized in that: Includes the following steps: S1, under the premise that the windshield has curvature along the Y direction, set system design constraints, the system design constraints include at least: not allowing the windshield curvature to be compensated by the overall tilt of the vehicle head-up display system along the Y direction, minimizing the space occupation in the Z direction while meeting the windshield incident conditions, and system imaging quality requirements. S2, a preset oblique light emission angle range is determined based on the curvature parameter of the windshield in the Y direction, the structural dimensions between the optical waveguide assembly and the compensation mirror assembly, and the optical path deflection requirements. The lower limit of the preset oblique light emission angle range is determined by whether the windshield incident conditions can be met without the system or the compensation mirror assembly being tilted in the Y direction. The upper limit of the preset oblique light emission angle range is limited by the system imaging quality and the emission efficiency of the optical waveguide assembly. S3, select multiple candidate oblique light emission angles within the preset oblique light emission angle range and use them for oblique light emission of the optical waveguide component respectively. For each candidate oblique light emission angle, evaluate the system imaging quality based on the corresponding optical path structure. When the system imaging quality under a certain candidate oblique light emission angle does not meet the system design constraints, the candidate oblique light emission angle is determined to be infeasible and is eliminated. S4. Determine the target oblique emission angle for the optical waveguide assembly from the candidate oblique emission angles that have passed the imaging quality evaluation, so that the system can meet both the windshield incident conditions and the system imaging quality requirements without having to tilt along the Y direction.

7. The method for determining the oblique beam exit angle of a compact optical waveguide HUD according to claim 6, characterized in that: The system imaging quality evaluation includes parallelism evaluation and distortion evaluation. Parallelism is used to characterize the consistency of imaging direction at different eye points within the preset driver eye box range. Specifically, it calculates the outgoing direction of light at different eye points for the same field of view incident conditions, and uses the angle difference between the light directions corresponding to different eye points as the parallelism evaluation index. Distortion is used to characterize the degree of deviation between the actual virtual image obtained from the imaging process and the ideal virtual image. The distortion is defined as the relative deviation value between the actual virtual image and the ideal virtual image, where the ideal virtual image is the virtual image obtained under the design reference imaging plane or reference imaging state. When both parallelism and distortion meet the preset thresholds, the corresponding oblique light exit angle is considered to meet the imaging quality requirements. The preset thresholds include parallelism less than 0.2° and distortion less than 5%.

8. The method for determining the oblique beam exit angle of a compact optical waveguide HUD according to claim 7, characterized in that: The imaging quality evaluation is based on the worst eye point within the eyebox range. Specifically, multiple discrete eye points are selected in a grid pattern within the preset eyebox range, and sampling points are selected in the left-right direction and the up-down direction of the vehicle to form a two-dimensional distribution set of eye points. For each eye point in the set of eye points, its corresponding imaging quality index is calculated, including at least parallelism and distortion. The eye point in the set of eye points with the largest deviation from the preset requirement is determined as the worst eye point, and the imaging quality at the worst eye point is used as the criterion for evaluating whether the corresponding oblique light emission angle is feasible, so as to ensure that the system has acceptable imaging quality throughout the entire eyebox range.

9. A compact optical waveguide vehicle head-up display system, comprising an optical waveguide assembly, a compensation mirror assembly, and a vehicle windshield, wherein the left-right direction of the vehicle is the Y-axis, the longitudinal direction of the vehicle is the Z-axis, and the vertical direction of the vehicle is the X-axis; characterized in that: The local normal direction of the windshield is deflected relative to the vehicle coordinate system in the vertical X direction of the vehicle. The optical waveguide assembly is configured as an oblique light-emitting structure to emit light rays, such that the emitted light rays leave the optical waveguide assembly in a direction inclined relative to the normal of the light-emitting surface of the optical waveguide assembly and have a directional component along the X direction, and the angle between the emission direction and the normal of the light-emitting surface is defined as the oblique light-emitting angle in the X direction. The compensation mirror assembly is configured to receive light rays emitted obliquely through the optical waveguide assembly, refract the light path, and project the light rays onto the windshield, so that the light rays are reflected by the windshield and enter the human eye to form a virtual image. Wherein, under the condition that the incident condition of the windshield is biased, causing the HUD light to be effectively deflected in the X direction, the X-direction oblique light-ejection structure of the optical waveguide component enables the light to obtain the directional component along the X direction before it is incident on the compensation mirror assembly and the windshield. Thus, under the premise that the incident condition of the windshield along the X direction is satisfied, it is not necessary for the compensation mirror assembly and / or the entire vehicle head-up display system to generate an attitude tilt along the X direction to compensate for the curvature.

10. A compact optical waveguide vehicle head-up display system according to claim 9, characterized in that: The X-axis oblique light emission angle is no greater than 50°.

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