Three-section zoom head-up display light path system, vehicle-mounted head-up display device, motor vehicle, light path regulation and control method and application

Abstract

The invention discloses a three-section zoom head-up display light path system. The light path system comprises an image generation unit, a free-form surface reflector and a zoom path optimization module, the image generation unit is used for generating an image light beam, and the image light beam is reflected by the free-form surface reflector and then is reflected to the eye position of a driver through a windshield to form a virtual image; the free-form surface reflector supports imaging of different virtual image distances according to preset multi-section surface type parameters; the zoom path optimization module controls the distance change between the image generation unit and the free-form surface reflector according to the vehicle speed information, adjusts the virtual image distance, and achieves three-section zoom display. The invention further discloses a vehicle-mounted head-up display device and / or a motor vehicle comprising the light path system. The invention further discloses a three-section type zooming head-up display light path regulation and control method which has wide application value.

Description

Technical Field

[0001] This invention belongs to the field of vehicle head-up display technology, and relates to a three-segment zoom head-up display optical path system, vehicle head-up display device, motor vehicle, optical path control method and application. Background Technology

[0002] Head-up display (HUD) systems have been widely used in smart cockpits in recent years, improving driving safety by projecting key information in front of the driver. However, traditional HUDs primarily use fixed-focal-length optical systems with a fixed virtual image distance, making it difficult to adapt to different driving environments. For example, at high speeds, a greater virtual image distance is more beneficial for reducing visual accommodation and integrating with the vehicle's autonomous driving assistance functions, while at low speeds in urban areas or when parked, a closer virtual image distance provides clearer auxiliary information. However, existing technologies have the following problems in multi-focal-length switching:

[0003] 1. Limited distance of a single virtual image: Traditional HUDs use a single focal plane design, which results in a fixed distance of the virtual image for information display. This cannot be flexibly adjusted according to the driving environment, affecting the visual experience and information acquisition efficiency.

[0004] 2. High cost of multi-focal surface solutions: Existing HUD solutions that break through the distance limitation of a single virtual image mainly rely on dual image sources or multiple freeform surface mirror optical elements to achieve dual focal surface display. However, these solutions require the design of two different optical paths and may also require two image display units or 3 to 4 freeform surface mirrors. This not only results in high costs but also problems such as complex optical systems and insufficient mechanical structure reliability.

[0005] 3. Inability to achieve zoom: Existing dual-focal-plane solutions cannot achieve zoom. They are all two sets of optical paths with fixed magnification to achieve a fixed virtual image distance, which lacks flexibility in terms of information display functionality. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a three-segment zoom head-up display optical path system, an in-vehicle head-up display device, a motor vehicle optical path control method and application, which utilizes geometric optical properties and freeform surface optical design to achieve switchable display across three focal segments, adapting to more driving environments and improving the efficiency of driver information acquisition.

[0007] This invention provides a three-segment zoom head-up display optical path system, the optical path system comprising: an image generation unit, a freeform surface mirror, and a zoom path optimization module;

[0008] The image generation unit is used to generate an image beam, which is reflected by the freeform surface mirror and then reflected by the windshield to the driver's eye position to form a virtual image;

[0009] The freeform surface mirror supports imaging at different virtual image distances based on preset multi-segment surface parameters; it can be used to reflect light paths and correct aberrations caused by windshield glass.

[0010] The zoom path optimization module controls the distance between the image generation unit and the freeform surface mirror based on the vehicle speed information, adjusts the virtual image distance, and realizes three-segment zoom display.

[0011] The three-stage zoom creates different virtual image distances: a close focal plane at 3m, a medium focal plane at 5.5m, and a distant focal plane at 8m.

[0012] The image generation unit further includes: a backlight assembly and a TFT screen; the backlight assembly is used to illuminate the TFT screen, and the TFT screen is used to generate an image to be displayed.

[0013] The image generation unit displays that the size of the image automatically adjusts as the distance to the virtual image changes, compensating for the influence of changes in the field of view on the field of view.

[0014] In one specific implementation, the field of view remains constant, with a size of 9°*3°;

[0015] To maintain a constant field of view, the size of the image generated by the image generation unit is adjusted through rendering by the driver chip or the upper-level system.

[0016] The freeform surface mirror adopts an XY polynomial surface shape with the highest order coefficient of 7, which meets the imaging requirements of three virtual image distances and optimizes indicators including MTF, astigmatism, parallax and distortion control.

[0017] Furthermore, the following optimizations were made to the freeform surface reflector in this invention:

[0018] 1) Multi-field asymmetric control optimization: By setting multi-field asymmetric control points on the mirror and forcibly constraining the imaging differences of the left, right and center fields in the optimization function, the phenomenon of a single field of view being clear while other fields of view are blurry is suppressed, ensuring the optical consistency between the lower edge and the center region of the large field of view (9°×3°).

[0019] 2) Dynamic compensation of principal ray tilt angle: Based on the change of principal ray incident angle under different virtual image distances (VID), a local slope self-adjustment mechanism of the mirror is established so that the reflected light is accurately focused on the target virtual image surface at each focal length, effectively eliminating focal drift and image skew problems.

[0020] 3) Manufacturability slope constraint: Limit the extreme values ​​of the first derivative (surface slope) in the X / Y direction during surface optimization to avoid abrupt curvature changes, ensure the feasibility of mirror processing (such as polishing and turning) and the stability of the surface after assembly.

[0021] In the specific implementation process, a zoom curve is constructed to achieve a coordinated match between imaging quality and display consistency at multiple virtual image distances;

[0022] The construction of the zoom curve includes the following steps:

[0023] Step a. Build an optical simulation system, fix the field of view, set the virtual image distance range and sampling step size, and record the object distance and image source display size at each virtual image distance;

[0024] Step b. Model and fit the data sampled in step a, and construct an interpolation function, as shown below:

[0025]

[0026] Where L(x): represents the interpolation calculation result of variables such as target virtual image distance (VID) or PGU position obtained according to the interpolation algorithm; y i : Represents the ordinate of the i-th sample point, i.e., the target value for interpolation, such as the virtual image distance or PGU position corresponding to a specific sample point; x i : Represents the x-coordinate of the i-th sample point, i.e., the input value for interpolation, such as the vehicle speed, scene mode, or other driving parameters corresponding to a specific sample point; x: Represents the input value in the current real-time state (such as the current vehicle speed or other driving parameters), which needs to be calculated using the interpolation algorithm; n: Represents the number of sample points participating in the interpolation; j: Represents the inner loop variable of the multiplication symbol Π in the interpolation process, used to traverse all sample points to calculate the multiplication result of each term in the interpolation function;

[0027] The construction of the optical simulation system includes the following steps: A basic model containing the object plane, eyepiece aperture, windshield, XY polynomial freeform surface mirror, and image plane is established in the lens data editor. Multiple configuration systems with different virtual image distances are set up, and zoom control is achieved by sharing the freeform surface mirror polynomial parameters. An optimization function containing multiple configuration constraints is constructed, with the RMS radius of the light spot, MTF≥0.4, principal ray alignment accuracy, and distortion<5% at each virtual image distance as core indicators. Local and / or global optimization is performed in conjunction with the physical constraints of the freeform surface coefficients. After optimization, the consistency of the virtual image size is verified through cross-configuration analysis, and optimized data including freeform surface polynomial coefficients, key VID parameter tables, and three-dimensional surface data is output.

[0028] The optical path system adopts a multi-configuration joint optimization design of a single freeform surface mirror. Multiple focal length configurations are established in CODE V and the mirror XY polynomial parameters are shared. Through global optimization, a single mirror is compatible with a virtual image distance of 3000-8000mm, eliminating the focal plane offset distortion of traditional multi-mirror structures.

[0029] And / or,

[0030] Construct an optimization function with cross-focal length constraints to simultaneously control the Spot RMS radius, MTF, and image center drift constraints of each focal length, thereby suppressing image jumps caused by optimization of a single focal length.

[0031] And / or,

[0032] An image size-object distance synchronous zoom model is introduced. By adjusting the PGU display size, the virtual image distance is compensated for, maintaining a constant field of view of 9°×3° from the driver's perspective, thus avoiding edge distortion and field of view compression.

[0033] Using the three-segment zoom head-up display optical path system described in this invention, near, medium, and far virtual image distances can be dynamically and automatically or manually selected based on vehicle speed, navigation information, and ADAS system output.

[0034] When in automatic switching mode, if the vehicle speed is less than 30km / h, it will automatically switch to the close focal plane.

[0035] If the vehicle speed is between 30km / h and 80km / h, it will automatically switch to the medium focal length.

[0036] If the vehicle speed is higher than 80km / h, switch to the distant focal plane.

[0037] When in manual switching mode, you can manually control and adjust the near, medium and far distance of the display focal plane according to your actual observation while driving, and select the focal plane that best suits your current observation.

[0038] In this invention, based on real-time data collected from the vehicle bus, including vehicle speed, ADAS status, navigation prompts, gear position, braking signals, and / or driver monitoring system data, the driving state integrated decision unit analyzes the driving scenario and driver focus, makes zoom control decisions, and dynamically calculates and adjusts the target value of the HUD virtual image distance.

[0039] During zoom control, a hysteresis threshold control mechanism is set up, which sets the minimum time interval threshold between two consecutive switching of virtual image distance, in order to suppress the visual burden on the driver caused by frequent changes in focal length.

[0040] And / or,

[0041] A focal length inertial integral weight evaluation mechanism is set up. When the system determines that the current virtual image distance does not meet the driving state requirements, the necessity of switching is evaluated by integral method. Virtual image distance switching is only performed when the integral value reaches the preset threshold.

[0042] The integration threshold or integration time is dynamically increased when the system determines that the driving behavior is in a stable state, thereby further avoiding frequent visual adjustments by the driver.

[0043] And / or,

[0044] During the virtual image distance switching process, the system executes a gradual animation to smoothly transition the image, thereby reducing the visual impact and fatigue during the focus switching process.

[0045] In one specific embodiment, the optical path system may further include: a dustproof plate and a HUD housing, wherein the dustproof plate is disposed above the image generation unit and the freeform surface mirror for dust and water protection; and the HUD housing is used to install and fix the aforementioned internal components and provide protection.

[0046] The present invention also provides a vehicle head-up display device, including the above-mentioned optical path system, and a vehicle mounting bracket for mounting the optical path system.

[0047] The present invention also provides a motor vehicle, including a vehicle body and the above-mentioned vehicle head-up display device, wherein the vehicle head-up display device is integrated in the space between the vehicle dashboard and the windshield.

[0048] This invention also provides a three-stage zoom head-up display optical path control method, comprising the following steps:

[0049] Step 1: Obtain real-time vehicle driving status information, including vehicle speed, navigation prompts, driver assistance system status, gear status, braking signals and / or driver monitoring system data;

[0050] Step 2: Based on the driving status information, determine the target virtual image distance through the driving status integrated decision unit;

[0051] Step 3: Based on the distance to the target virtual image, control the change in object distance between the image generation unit and the freeform surface mirror, and simultaneously adjust the display size of the image generation unit to compensate for changes in the field of view and maintain a preset constant field of view.

[0052] Step 4: Based on the image size adjustment and object distance change, the image beam is reflected by a freeform surface mirror and then reflected through the windshield to the driver's eye position to form a virtual image of the target;

[0053] Step 5: During the virtual image distance switching process, a hysteresis threshold control mechanism and a focal length inertial integral evaluation mechanism are applied to perform a smooth transition switching of the virtual image.

[0054] The hysteresis threshold control mechanism sets a minimum time interval threshold between two consecutive switching of the virtual image distance;

[0055] And / or,

[0056] The focal length inertial integral weight evaluation mechanism evaluates the necessity of switching by integral method when the system determines that the current virtual image distance does not meet the driving state requirements. Virtual image distance switching is only performed when the integral value reaches a preset threshold.

[0057] The integration threshold or integration time is dynamically increased when the system determines that the driving behavior is in a stable state.

[0058] And / or,

[0059] During the virtual image distance switching process, the system executes a gradual animation for a smooth transition.

[0060] The present invention also provides the application of the above-mentioned optical path system, the above-mentioned vehicle head-up display device, the above-mentioned motor vehicle, or the above-mentioned control method in vehicle driving information prompts, driving assistance information display, and augmented reality navigation guidance.

[0061] The beneficial effects of this invention include: By introducing a three-segment zoom head-up display optical path system, combined with a freeform surface reflector design, dynamic object distance adjustment, and synchronous image size compensation, this invention achieves flexible switching and continuous transition of virtual image distance in the vehicle head-up display system. This not only effectively overcomes the limitations of the fixed virtual image focal plane in traditional HUD systems, significantly improving the driver's perception efficiency of key information in different driving scenarios, but also avoids visual fatigue caused by frequent focal length switching through multi-configuration joint optimization design and the introduction of hysteresis threshold and inertial integration mechanism, enhancing the comfort and safety of the driving experience. In addition, this invention adopts a structural design of a single freeform surface reflector combined with a single image generation unit, which takes into account the optimization of imaging quality, system size, and manufacturing cost, and has good engineering feasibility and large-scale industrial application prospects. It can be widely used in vehicle head-up display devices in urban roads, highways, and complex driving environments, and has significant technological progress and practical application value. Attached Figure Description

[0062] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0063] Figure 1 This is a schematic diagram of the overall optical path of the three-segment zoom head-up display optical path system of the present invention.

[0064] Figure 2 This is a projection diagram of the overall optical path of the present invention.

[0065] Figure 3 This is a side view of the internal optical path of the present invention.

[0066] Figure 4 This is the object distance & VID variation curve of the present invention.

[0067] Figure 5 This is the curve showing the variation of the horizontal dimension and VID of the PGU in this invention.

[0068] Figure 6 This is a block diagram of the zoom decision logic of the three-segment zoom head-up display optical path system of the present invention.

[0069] In the diagram, 1-backlight assembly, 2-TFT screen, 3-farthest focal plane optical path, 4-nearest focal plane optical path, 5-freeform surface reflector, 6-dustproof plate, 7-HUD housing, 8-farthest virtual image plane, 9-nearest virtual image plane, 10-windshield, 11-eye position. Detailed Implementation

[0070] The present invention will be further described in detail below with reference to the specific embodiments and accompanying drawings. Except for the contents specifically mentioned below, the processes, conditions, and experimental methods for implementing the present invention are all common knowledge and general knowledge in the art, and the present invention does not have any particular limitations.

[0071] The following are explanations of some of the terms used in this invention:

[0072] MCU (Micro Controller Unit): A microcontroller unit is a control chip that integrates a microprocessor and peripheral devices, typically used in real-time control systems.

[0073] ECU (Electronic Control Unit): One of the main control modules of an automotive electronic system, used to manage the operation of various vehicle subsystems in real time.

[0074] VID (Virtual Image Distance): The distance between the virtual image position displayed in a head-up display (HUD) system and the human eye.

[0075] PGU (Picture Generation Unit): The image generation unit is a module in a HUD system used to generate and display images. It typically includes a display screen, a backlight, and driving circuitry.

[0076] CODE V (Optical Design Software): A professional optical design software used for the design, modeling, simulation, and optimization of optical systems.

[0077] LDE (Lens Data Editor): The lens data editor, an interface in CODE V software used to define and edit the various optical surfaces of an optical system.

[0078] Surface type:XY polynomial: A method for defining the shape of a freeform surface, expressing the optical surface shape through XY coordinate polynomial coefficients.

[0079] Multiple Configuration Setup: One of the features of the CODE V software, which can be used to simultaneously simulate and optimize optical system configurations at multiple different focal lengths.

[0080] FOV (Field of View): The field of view refers to the maximum range of angles that an optical system can display or capture.

[0081] Field size: The size of the field of view.

[0082] Chief Ray: The main ray.

[0083] Vary (Variable Setting Command): A command in the CODE V software used to specify optical parameters as variable parameters for automatic optimization and adjustment.

[0084] Merit Function: An optimization function used to define and evaluate the performance of an optical system, enabling precise control of the system's optimization objectives.

[0085] Automatic Default Merit Function Generator: A built-in feature of the CODE V software, which automatically generates an initial target function for users to further modify and improve.

[0086] RMS SPOT Radius (Root Mean Square SPOT Radius / MTF): The root mean square radius of the light spot is used to describe the size of the dot spread in an image and is an important indicator of the imaging sharpness of an optical system.

[0087] Local Optimization (Damped Least Squares): A fast, locally convergent optimization algorithm suitable for local fine-tuning and optimization of optical system parameters.

[0088] Global Synthesis: A more comprehensive optimization algorithm in CODE V that explores the global parameter space to find better optical design solutions.

[0089] Spot Diagram: A diagram used to visually display the focusing effect and image quality of an optical system on the image plane.

[0090] Chief Ray Direction: Describes the direction in which the chief ray propagates within the optical system, used to confirm the accuracy of the arrangement of optical elements and the alignment precision of the optical system.

[0091] STEP / IGES (Standard for The Exchange of Product model data / InitialGraphics Exchange Specification): Two commonly used industrial 3D geometric model data exchange formats, used to export optical design results to 3D modeling software.

[0092] Surface Sag / Normal data: Data describing the specific surface shape of a freeform mirror, used for subsequent manufacturing and processing.

[0093] Multi-Configuration: A feature in CODE V that allows simultaneous optimization of multiple optical conditions, such as optical systems at different virtual image distances.

[0094] This invention provides a three-segment zoom head-up display (HUD) optical path system. This system utilizes the optical design software CODE V to calculate and optimize the zoom of a single-focal-plane AR-HUD system. Through geometric optics analysis, it calculates the object distance, image generation unit size, and freeform surface optical parameters adapted to different focal lengths, achieving zoom display with three virtual image distances. The HUD system designed in this invention supports three different virtual image distances and can be dynamically adjusted using software algorithms to achieve a transition from near to far views, enhancing the depth and immersive experience of the display. This invention is applicable to intelligent cockpit systems, improving the readability of driving information and the driving experience.

[0095] Based on this, the present invention addresses the deficiencies in the prior art and effectively solves the following technical problems:

[0096] 1. Breaking through the limitations of a single focal plane: By using a three-segment focal plane, the distance of the displayed virtual image can be flexibly adjusted according to the driving environment, thereby improving the adaptability of the HUD display content to the driving environment and the readability of the information obtained by the driver.

[0097] 2. High cost of dual-focal surface solution: The solution of this invention uses only a single image source + a single freeform surface reflector, which is significantly cheaper than dual-focal surface HUD products with dual image sources or multiple freeform surface reflectors on the market.

[0098] 3. Poor scalability of traditional single-focal-plane optical paths: With the existing three-focal-plane optical path architecture, without changing the freeform surface shape, the zoom curve (which includes the relationship between the virtual image distance and the object distance, as well as the relationship between the object distance and the UI size) can be obtained through optical calculations. Combined with software algorithms, continuous zooming of different focal plane distances at near, medium and far distances can be achieved within a certain range, producing a sense of depth and enhancing the user experience. This is something that traditional single-virtual-image-distance HUDs cannot achieve.

[0099] By solving the above problems, this invention can not only significantly improve the visual experience and realistic effect of HUD, but also provide a new method and new idea for the development of vehicle HUD technology without significantly increasing costs.

[0100] Specifically, this invention provides a three-segment zoom head-up display (HUD) optical path system, an in-vehicle head-up display device, and a motor vehicle. This optical path system utilizes geometric optics characteristics and freeform surface optical design, combined with CODE V optical design software, to achieve multi-focal-segment switching of virtual image distance and continuous zoom functionality. In this invention, the overall optical path projection diagram and the internal optical path side view are respectively as shown below. Figure 2 and Figure 3 As shown.

[0101] The innovative technical solution of this invention will be described in detail below, taking into account its specific structure and optical principles:

[0102] I. Overall Architecture of the Optical System

[0103] The three-segment zoom HUD optical path system of the present invention includes the following core components:

[0104] • Image generation unit (PGU) (including backlight assembly 1 and TFT screen 2): A single image generation unit is used. The image size output by the image generation unit can be adjusted according to the calculation results of the optical path to meet the imaging requirements of different focal lengths. In one specific embodiment of the present invention, a 4.1-inch TFT-LCD is used as the component of the image generation unit.

[0105] • Freeform surface mirror 5: As the core optical component of this invention, the surface shape of the freeform surface mirror 5 is designed based on the multi-segment focal plane parameters calculated by CODE V, taking into account the imaging quality at different focal lengths.

[0106] • Zoom path optimization module: Utilizes optical optimization algorithms to calculate the parameters of three focal planes, and combines the changes in virtual image distance, object distance, and UI size with their interrelationships to achieve zoom functionality.

[0107] Two- and three-stage zoom principle

[0108] The three-segment focal plane zoom scheme of the present invention is based on the imaging principle of geometric optics and freeform surface mirror 5, and adopts the following technical measures:

[0109] 1. Calculation of virtual image plane position and object distance

[0110] By changing the display size of the image generation unit (PGU) and the distance between the image generation unit (PGU) and the freeform mirror 5, the projection distance, or VID (virtual image distance), can be altered. This is because, in the off-axis reflection system of the HUD, the image seen by the driver is a virtual image formed after reflection by the freeform mirror 5 and then by reflection by the windshield 10. A characteristic of the virtual image is that the greater the object distance, the farther away the virtual image. Therefore, if it is desired to reduce the virtual image distance, the object distance must be reduced. In the HUD system of this invention, the object distance is the optical path between the PGU and the freeform mirror 5. Therefore, reducing the object distance can be achieved by adjusting the position of the moving PGU. However, while reducing the projection distance, the distance between the PGU and the freeform surface mirror 5 also decreases. Since the area of ​​the light cone tail of the light emitted by the PGU continuously increases during propagation (non-parallel light emission), the closer the PGU is to the freeform surface mirror 5, the smaller the image area reflected by the freeform surface mirror 5 becomes. As the projection distance decreases, the angle subtended by the virtual image relative to the human eye decreases. Therefore, to compensate for the loss of field of view, the image size displayed by the PGU needs to be increased as the projection distance decreases. This is because in existing head-up display products, the field of view is usually a fixed parameter that does not change during use. Therefore, this invention also utilizes CODE V optical design software to calculate the object distance, image generation unit display size, and freeform surface coefficient corresponding to three different virtual image distances based on geometric optics principles, thereby realizing the three-segment zoom HUD system of this invention.

[0111] In one specific embodiment of the present invention, the virtual image distance, object distance, and image generation unit size are shown in Table 1 (data unit is mm):

[0112] Table 1 Relationship between virtual image distance, object distance, and image generation unit size

[0113] Virtual image distance Object distance (PGU to mirror) Image generation unit size (X direction) 3000 310.23 85.68 5500 362.54 74.68 8000 374.68 72.08

[0114] In this invention, the freeform surface coefficient of the freeform surface mirror used is calculated by the following formula:

[0115]

[0116] Where z represents the coordinate value of the surface shape of the freeform mirror in the z-axis direction; c represents the curvature of the reference surface of the freeform mirror, i.e., the reciprocal of the radius of curvature of the reference sphere; k represents the conic coefficient, describing the quadratic curvature characteristic of the reference surface of the freeform surface; and r represents the radial distance from any point on the reference surface of the freeform surface to the optical axis. A i E represents the surface type coefficient of the i-th XY polynomial, which is used to further describe the higher-order aberration characteristics of the freeform surface; i (x,y) represents the coefficient A. i The functional expression of the specific terms of the XY polynomial, specifically x m y n , where m and n are integers.

[0117] The representation of the specific terms of the XY polynomial corresponding to the XY polynomial surface shape coefficients of the freeform surface mirror, and the numerical coefficients of each specific term of the XY polynomial are shown in Table 2 below:

[0118] Table 2. Specific Terms and Numerical Coefficients of the XY Polynomial

[0119] Y curvature 0.0011563 quadric surface constant 1.0424094 Normalized radius 1 X2Y0 1.0625410E-04 X1Y1 2.7381419E-05 X0Y2 -1.2128007E-04 X3Y0 -5.0085496E-08 X2Y1 8.5322359E-08 X1Y2 -1.1323464E-07 X0Y3 6.9599301E-08 X4Y0 -1.4625635E-10 X3Y1 52400836E-11 X2Y2 -8.5409400E-10 X1Y3 -1.4799035E-10 X0Y4 -5.6237895E-10 X5Y0 -5.8311565E-13 X4Y1 3.2857468E-12 X3Y2 -6.6088270E-15 X2Y3 -3.6170043E-13 X1Y4 -8.0994844E-12 X0Y5 -1.5769846E-12

[0120] The left column shows the representation of the specific terms of the XY polynomial corresponding to the XY polynomial surface shape coefficients of the freeform mirror. For example, "X2Y0" indicates that the expression for this term is x. 2 y 0 That is, x 2 Item; similarly, "X1Y2" represents x 1 y 2 =xy 2 .

[0121] The right column corresponds to the numerical coefficients (i.e., A) of each specific term in the XY polynomial. i ), used to define the specific surface shape of a freeform mirror in order to precisely control aberrations and optical performance.

[0122] This invention uses a fixed-size image source (such as a 4.1-inch TFT-LCD display) and a corresponding backlight assembly 1 as the image generation unit. When the virtual image distance (VID) changes, if the effective display area of ​​the image source is not adjusted accordingly, the projected virtual image will cause the angle of the image observed by the human eye to shrink or enlarge due to the change in the light cone divergence angle, resulting in inconsistent information visibility range.

[0123] To this end, the present invention dynamically controls the size of the optically output image by adjusting the effective display area (i.e., the UI area) of the image source, thereby maintaining a constant field of view (FOV) of the HUD projection screen. For example:

[0124] In one specific implementation, when the virtual image distance is reduced from 8000mm to 3000mm, in order to maintain a 9°×3° field of view, the horizontal display area of ​​the PGU needs to be increased from approximately 72mm to 85mm; this change is achieved through internal driver chips or upper-level system rendering adjustments.

[0125] Outputting image content of different sizes through graphics rendering software or middleware, typical implementations include:

[0126] The upper-layer application switches the output of UI images with display sizes of 85mm, 74mm, or 72mm based on vehicle speed and / or scene;

[0127] Transmitted to PGU via interfaces such as MIPI, LVDS, and HDMI;

[0128] The output image from the optical path displays a dynamic zoom effect.

[0129] In the specific implementation of this invention, the virtual image distances of the three focal planes are as follows:

[0130] • Close-range focal plane (3m): Suitable for low-speed driving or parking scenarios in the city, providing clear lane departure warnings and parking assistance information.

[0131] • Mid-range focal plane (5.5m): Suitable for general urban or national highway driving scenarios, providing key information such as navigation, vehicle speed, and speed limit signs.

[0132] • Long-range focal plane (8m): Suitable for high-speed driving scenarios on closed roads, providing long-distance road information and navigation assistance display to improve driving safety.

[0133] In the specific implementation of this invention, for focal plane displays at different distances, the field of view is always kept at 9°*3°.

[0134] 2. Zoom curve generation

[0135] Based on the three virtual image distances, a zoom curve is further optimized using CODE V to describe the relationship between the object distance (distance from PGU to the mirror), the virtual image distance, and the UI size.

[0136] • This zoom curve ensures that, without replacing the optical freeform surface mirror 5 and the image generation unit, a continuous transition of three virtual image distances can be achieved by adjusting the object distance and UI size, meeting the usage needs of different driving scenarios.

[0137] This method breaks the limitations of traditional off-axis dual-focal-surface HUDs and achieves the function of coaxial "dynamic zoom", bringing a stronger sense of immersion and depth while ensuring that the driver's line of sight remains unchanged.

[0138] Specifically, in the three-segment zoom head-up display (HUD) optical path system described in this invention, to achieve coordinated matching between imaging quality and display consistency at multiple virtual image distances, it is necessary to construct a nonlinear zoom control curve to control the relative position (object distance) between the image source and the optical system, and the relationship between the image size (UI size) and the virtual image distance (VID). This zoom curve is one of the core technical points of this invention, and its construction method is as follows:

[0139] First, based on the model of the HUD off-axis imaging optical system, a complete optical simulation system was built using the optical design software CODE V. With a fixed field of view (e.g., 9° × 3°), the virtual image distance was set to a range of 3000mm to 8000mm. Sampling was performed in 100mm increments, and the following parameters were recorded for each virtual image distance:

[0140] i. The optimal object distance between the image generation unit (PGU) and the freeform mirror 5;

[0141] ii. Ensure the image source display size (UI width, in mm) required for a fixed field of view.

[0142] This process ultimately resulted in a two-dimensional data table, which served as the basis for fitting subsequent zoom control logic.

[0143] To ensure continuous zoom and stable imaging at different virtual image distances, this invention performs mathematical modeling and fitting on the aforementioned sampled data. Specifically, a cubic Lagrange interpolation algorithm is used, which is suitable for HUD systems with high image accuracy requirements and sensitivity to the smoothness of focal plane changes. Multiple sample points (i.e., the aforementioned two-dimensional data table) are used to fit the target value to generate a zoom curve. The interpolation function is as follows:

[0144]

[0145] Where L(x): represents the interpolation calculation result of variables such as target virtual image distance (VID) or PGU position obtained according to the interpolation algorithm; y i : Represents the ordinate of the i-th sample point, i.e., the target value for interpolation, such as the virtual image distance or PGU position corresponding to a specific sample point; x i: Represents the x-coordinate of the i-th sample point, i.e., the input value for interpolation, such as the vehicle speed, scene mode, or other driving parameters corresponding to a specific sample point; x: Represents the input value in the current real-time state (such as the current vehicle speed or other driving parameters), which needs to be calculated using the interpolation algorithm; n: Represents the number of sample points participating in the interpolation; j: Represents the inner loop variable of the multiplication symbol Π in the interpolation process, used to traverse all sample points to calculate the multiplication result of each term in the interpolation function.

[0146] In practical engineering implementation, the above interpolation algorithm can be pre-installed in the HUD control system (such as MCU, ECU) and run as a lookup table or built-in function module. Its execution logic is as follows:

[0147] 1. The controller determines the distance to the target virtual image based on the vehicle's operating status (vehicle speed / scene);

[0148] 2. The interpolation module finds neighboring sample points based on the target VID and performs interpolation calculations;

[0149] 3. Output the corresponding PGU object distance position (can be used with motorized track) and PGU display area size (electronic zoom UI);

[0150] 4. Multi-focal length zoom function is achieved through dynamic adjustment.

[0151] This invention utilizes the optical design software CODE V to construct a complete optical simulation system. The specific steps include the following:

[0152] a. System Modeling Preparation Stage

[0153] 1. Open CODE V and build a basic optical system.

[0154] Define the following key surfaces in LDE (Lens Data Editor):

[0155] Object plane (actual virtual image plane), eye box (aperture), windshield, freeform surface mirror (Surface type: XYpolynomial), image plane (image source plane, location of PGU);

[0156] 2. Image quality optimization is performed using the CODE V custom optimization function, where VID = 8000mm;

[0157] 3. Set the zoom system virtual image distance (VID)

[0158] Zoom settings:

[0159] VID1 = 3000mm

[0160] VID2 = 3100mm

[0161] …

[0162] VID51 = 8000mm

[0163] For each VID, configure it using CODE V's Multiple Configuration Setup.

[0164] b. Multi-Configuration System Settings

[0165] 1. Use the Configurations feature to set 51 configuration groups (Config 1 / 2 / 3… / 51)

[0166] Configure each configuration as follows:

[0167] Different object distances (Z coordinate) from PGU to the reflector

[0168] PGU image size (FOV / Field size)

[0169] Virtual image imaging target point (setting the distance of the Chief Ray)

[0170] Use the Vary command to set all XY polynomial parameters of the freeform mirror as universal variables, which are shared across all configurations.

[0171] c. Optimization Constraints and Objective Setting (Merit Function)

[0172] 1. Set the Merit Function (MF) target.

[0173] Use the Automatic Default Merit Function Generator, then manually modify it by adding the following key items:

[0174] Virtual image sharpness (far-field Spot RMS or MTF) under various configurations: RMS SPOT Radius at Virtual Image Plane (all configs)

[0175] MTF 6cy / mm target ≥ 0.4 (for center & edge fields)

[0176] Minimize the height and direction errors of the Chief Ray under each configuration.

[0177] 2. Set constraints for the freeform surface mirror shape (Optional)

[0178] Set the surface coefficient within a reasonable physical range, for example:

[0179] The maximum number of times this item can be used is 7.

[0180] d. Startup optimization (Global / Local)

[0181] 1. Select optimization mode

[0182] Initially, Local Optimization (Damped Least Squares) was used for rapid adjustment;

[0183] If the surface convergence is poor, Global Synthesis can be attempted to find the global optimum.

[0184] 2. Check the optimization results for each round.

[0185] Check each configuration:

[0186] Is the size of the Spot Diagram within the tolerance range?

[0187] Does the MTF reach ≥0.4?

[0188] Is the Chief Ray Direction aligned with the virtual image?

[0189] Image distortion is controlled to be less than 5%.

[0190] e. Verify zoom transition consistency (cross-configuration performance verification)

[0191] 1. Compare the image quality consistency of Config 1 to 51:

[0192] The difference in projection size of the same image source content at different virtual image distances;

[0193] The edge blurring and distortion changes of each field angle are controlled consistently.

[0194] 2. If further precision is required, add intermediate transition configurations (e.g., Config 1.5, 2.5…51.5) to verify the transition points.

[0195] f. Output optimized data

[0196] Output the XY polynomial coefficients of the final freeform mirror (for modeling and fabrication);

[0197] Output the object distance, FOV, image size, etc. for three configurations (VID=3000 / 5500 / 8000), and provide a zoom curve table;

[0198] Optional output:

[0199] CODE V Export→STEP / IGES Surface Model;

[0200] Export Surface Sag / Normal data and import it into Catia / SolidWorks.

[0201] In the process of optical optimization design of the three-segment zoom head-up display (HUD) optical path system, this invention adopts several innovative modeling and optimization strategies, breaking through the technical bottleneck that traditional HUDs can only be designed based on a single focal plane, and realizing the continuous zoom effect of using a single optical element at multiple virtual image distances. The specific innovations are as follows:

[0202] I. A Joint Optimization Method for Freeform Surfaces Based on Multi-Configuration Systems

[0203] Traditional HUD optical systems optimize imaging for only a single focal plane, failing to maintain consistent image quality across multiple virtual image distances. This invention utilizes CODE V's Multi-Configuration function, achieving for the first time in a HUD system:

[0204] 1) Multiple virtual images share the same freeform mirror shape at distances of 3m, 5.5m, and 8m;

[0205] 2) The surface shape is uniformly optimized under all configurations to ensure performance across multiple focal lengths;

[0206] 3) During optimization, a unified Merit Function is established to simultaneously evaluate indicators such as parallax, distortion, and MTF across multiple focal planes.

[0207] The optimization in this invention breaks the limitation of "one lens, one focal length" and realizes the structural integration innovation of "single lens, multiple focal lengths" co-forming imaging.

[0208] II. Introduce a nonlinear image size and object distance compensation model to achieve constant field-of-view zoom design.

[0209] Because changes in the virtual image distance will naturally cause changes in the field of view, traditional HUD designs do not consider an "image size compensation" mechanism, resulting in severe inconsistencies in the image angle across multiple focal lengths. This invention, for the first time:

[0210] 1) A nonlinear zoom curve model was constructed to dynamically scale and control the size of the PGU image;

[0211] 2) Use simulation data (object distance / image size) in CODE V combined with exponential interpolation or spline fitting;

[0212] 3) Ensure that the image angle is consistent across all focal planes (e.g., 9° × 3°) to avoid visual jumps for the driver.

[0213] The optimization in this invention introduces an equal field-of-view control mechanism into the zoom HUD system, realizing a coupled design of optical-display collaborative compensation.

[0214] III. Establish cross-focal length image consistency constraints and optimize the Merit Function construction method.

[0215] In the Merit Function construction of this invention, not only are conventional aberrations (such as RMS spot and MTF) controlled, but the following constraint objectives are also added:

[0216] 1) Cross-configuration image center offset limitation: Ensures that the virtual image maintains a relatively stable position within the human eye's field of view at different focal lengths, reducing parallax.

[0217] 2) Cross-configuration image quality consistency target: such as controlling the MTF difference within ±0.05 to avoid blurring at a certain focal length.

[0218] This invention penalizes the "bias" of freeform mirrors in image quality under different configurations by setting a surface shape shared error term, thereby encouraging global surface shape balance optimization. It also introduces a multi-objective collaborative optimization mechanism into a HUD zoom system for the first time, constructing a Merit Function system with balanced performance across configurations.

[0219] IV. Limiting the range of high-order freeform surface coefficients to achieve integrated optical design and manufacturing.

[0220] To ensure the manufacturability of the optimized surface and its integration with the vehicle, this invention incorporates the following in the XY polynomial design of the freeform mirror:

[0221] 1) Limit the highest order of aspherical surfaces to no more than 7, balancing imaging quality and manufacturing complexity;

[0222] 2) Constrain the coefficients of each order within ±1e-7 to avoid abrupt changes in surface shape;

[0223] 3) Export the surface file for CAD modeling, ensuring consistency with the data in the Catia / Solidworks system.

[0224] The optimization in this invention achieves manufacturing-friendly constraints on optical optimization parameters, thereby improving the system's ability to be mass-produced.

[0225] III. Design of Freeform Surface Reflectors

[0226] The design of the freeform surface mirror plays a crucial role in this invention. Through CODE V optimization calculations, its surface parameters satisfy the following conditions:

[0227] a) Multi-focal length optimization:

[0228] • The surface coefficient of the freeform mirror is rigorously calculated to simultaneously meet the imaging requirements of three focal planes.

[0229] • The optimization range of surface parameters includes higher-order coefficients of the XY polynomial up to the 7th order, in order to control various indicators (distortion, field curvature, parallax, MTF) and improve image quality.

[0230] The present invention ensures good image quality at different focal lengths through the following scheme:

[0231] ① Freeform surface mirror shared structure + multi-configuration joint optimization

[0232] This invention uses a single freeform surface mirror to achieve zooming at three virtual image distances. All configurations share the same optical reflective surface type, avoiding imaging deviations caused by focal length switching in traditional multi-mirror structures.

[0233] Specific steps:

[0234] In CODE V, a Multi-Configuration system is established to represent different focal lengths;

[0235] All focal lengths share a single freeform mirror, whose XY polynomial coefficients are globally shared variable parameters;

[0236] Each configuration segment has its own set of field of view, image size, and object distance parameters, serving as an independent target.

[0237] Through joint optimization, we ensure that the surface shape can achieve good image quality at all three focal lengths.

[0238] Technical effects:

[0239] Ensure good focus at all three focal lengths;

[0240] To avoid localized optimization and global distortion caused by the mirror's "biased focus on a certain focal plane".

[0241] ② Construct an imaging consistency-oriented Merit Function (optimization function)

[0242] To prevent "bias optimization" where images are sharp at one focal length but blurry at other focal lengths, this invention incorporates the following cross-focal length imaging consistency control term into the Merit Function:

[0243] 1. Spot RMS limits (image focusing quality) for each focal length;

[0244] 2. MTF control (image resolution) for each focal length;

[0245] 3. Image center drift constraint (to avoid image jitter).

[0246] Technical effects:

[0247] The image resolution is consistent across all focal planes;

[0248] The image position is stable and does not change abruptly;

[0249] The driver will not perceive the frame skipping effect of the image "focal length switching".

[0250] ③ Image size compensation matching mechanism (maintaining equal field of view)

[0251] As the distance to the virtual image changes, the field of view (FOV) of the HUD image in the driver's eyes will naturally shrink or expand, resulting in changes in the area of ​​visual clarity.

[0252] This invention employs an "image size-object distance synchronous zoom model," which dynamically adjusts the image display area size (UI width) to maintain a constant field of view, thereby preserving image clarity and consistent boundaries.

[0253] Near focus (3m) → UI size increased to approximately 85mm;

[0254] Telephoto (8m) → UI size reduced to approximately 72mm;

[0255] The field of view remains unchanged at 9° × 3° for all focal lengths.

[0256] Technical effects:

[0257] Ensure that the driver sees a consistent range of images at different focal lengths;

[0258] The image edges are not distorted or compressed, resulting in clear and stable imaging.

[0259] In summary, this invention effectively ensures imaging clarity, stability, and consistency at multiple virtual image distances through various technical means such as multi-configuration joint optimization, image size compensation control, unified freeform surface design, and optimization function construction. It overcomes the technical bottlenecks of image blurring, defocusing, or abrupt changes during zooming in traditional HUD systems and has strong engineering application and feasibility.

[0260] b) Optical optimization criteria:

[0261] • By optimizing optical parameters such as field curvature, static distortion, dynamic distortion, parallax, and MTF, clear imaging is ensured at all three virtual image distances.

[0262] • CODE V uses a Merit Function to control the image size, object distance, and light transmission efficiency generated by the image generation unit, thereby optimizing the surface shape of the freeform mirror.

[0263] IV. Dynamic zoom control algorithm

[0264] 1. Algorithm Principle:

[0265] • By combining information from vehicle speed sensors, ADAS data, and navigation systems, the virtual image distance of the HUD is dynamically adjusted.

[0266] For example, when the vehicle is moving at low speed or parked, the system automatically switches to the "near focal plane" and at high speeds it switches to the "far focal plane", seamlessly meeting the driver's visual needs.

[0267] 2. Human-computer interaction optimization:

[0268] It offers two modes: "manual adjustment" and "automatic adjustment," ensuring that drivers can flexibly choose the optimal virtual image distance in different driving scenarios, thus improving the user experience.

[0269] This invention fully utilizes geometric optical characteristics and freeform surface optical design to realize an innovative solution for a three-segment zoom HUD, which has significant technical advantages and market competitiveness.

[0270] Example 1: Optical System Design of a Three-Segment Zoom HUD Optical Path System

[0271] This invention provides a three-segment zoom head-up display (HUD) optical path system. Through optical structure optimization, image generation unit size adjustment, and innovative design of freeform surface mirrors, it meets the imaging requirements of multiple focal lengths and achieves dynamic zoom of virtual image distance and clear imaging.

[0272] I. Optical System Structure and Parameter Setting

[0273] like Figure 1 As shown, the optical system of the present invention includes the following core components:

[0274] • Image Generation Unit (PGU): A 4.1-inch TFT-LCD is used as the image display component, and its horizontal size is dynamically adjusted according to the change of virtual image distance.

[0275] • Freeform surface mirror: As a reflective optical element, the optimized design of the freeform surface mirror meets the imaging quality requirements of the three focal planes.

[0276] Regarding the freeform surface mirror 5 in this invention, in the three-segment zoom HUD system of this invention, in order to achieve the sharing of the freeform surface mirror 5 across multiple focal lengths while maintaining consistent imaging quality, in addition to using the highest 7th order XY polynomial for surface shape optimization, this invention also conducts in-depth structural and performance improvement design for the freeform surface mirror in the following aspects:

[0277] 1. Employing asymmetric control point constraints to improve parallax consistency.

[0278] In HUD systems, freeform mirrors must simultaneously control the imaging paths in multiple fields of view. Their mirror asymmetry severely impacts the imaging consistency across different field points. Therefore:

[0279] ●This invention sets multiple asymmetric control points for the mirror surface in CODE V;

[0280] ● Add multiple field-of-view (e.g., left, right, center) imaging quality difference control items to the Merit Function;

[0281] ● The optimization process automatically suppresses the phenomenon of "clear in one direction but blurry in others".

[0282] Technical advantages: Maintains clear and consistent image edges even in a large field of view (9°×3°) HUD system.

[0283] 2. Introduce a tilted incident angle self-compensation design (non-zero principal ray tilt angle compensation).

[0284] The HUD system uses an off-axis optical path, and the principal rays received by the freeform mirror exhibit different tilt angles at different focal lengths. Without compensation, this can easily lead to focus drift or skew.

[0285] ●This invention introduces the Chief Ray Angle Compensation mechanism:

[0286] 1. Record the changes in the incident angle of the principal ray under different VIDs during ray tracing;

[0287] 2. Automatically optimize the local slope of the mirror surface so that the principal rays at each focal length are still focused on the virtual image surface of the target after reflection.

[0288] Technical advantages: Improves focal plane drift and image skew, enhancing imaging stability.

[0289] 3. Slope Control in Surface Shape Optimization

[0290] In actual manufacturing, the surface of a freeform mirror cannot have too rapid surface undulations, otherwise it will be difficult to polish or turn.

[0291] This invention introduces a slope limit during the optimization process:

[0292] The first derivative of the mirror in the X / Y direction is limited to a set value;

[0293] Technical advantages: Ensures that the optimized surface shape has good machinability and assembly consistency.

[0294] • Anti-sparkling and dustproof film: Installed in the HUD optical path, it is used to block external sunlight and ambient stray light to ensure the clarity and contrast of the virtual image.

[0295] • Windshield 10: As an optical reflective element in the imaging system, it combines with the reflection of the freeform mirror 5 to achieve the final image.

[0296] II. Calculation of Virtual Image Distance and PUG Size

[0297] In the HUD system of this invention, the virtual image distance (VID) is varied by adjusting the image size generated by the PGU image generation unit and the object distance from the PGU to the freeform surface mirror 5. Its core principle is as follows:

[0298] • When the PGU is far from the freeform surface mirror 5, the virtual image distance becomes farther; when the PGU is close to the freeform surface mirror 5, the virtual image distance becomes closer.

[0299] • The size of the PGU needs to be matched with the changes in VID to ensure that the driver can stably obtain a complete display image within the field of view.

[0300] Based on optical calculations and optimization using CODE V software, the following results were obtained: Figure 4 , Figure 5 Correspondence.

[0301] III. Design and Optimization of Freeform Surface Reflectors

[0302] The freeform surface mirror 5, as a key imaging element of the HUD system, has its surface shape optimized as follows:

[0303] 1. Parameter optimization

[0304] • The XY polynomial freeform surface model of CODE V is adopted, and the coefficient terms are optimized up to the 7th order to control key indicators such as image distortion, field curvature, and parallax.

[0305] • The goals of surface optimization include improving MTF (modulation transfer function), improving image sharpness, and reducing image distortion.

[0306] IV. Dynamic zoom control algorithm

[0307] The HUD system of this invention employs a dynamic zoom control algorithm to automatically adjust the virtual image distance based on the driving scenario and vehicle driving status. The specific algorithm is described below:

[0308] 1. Data Input

[0309] The system receives data from the vehicle speed sensor, ADAS (Advanced Driver Assistance Systems), and navigation system.

[0310] • Based on the vehicle's speed and driving scenario, the appropriate virtual image distance is automatically selected, as shown in Table 3:

[0311] Table 3. Relationship between formal patterns and virtual image distance

[0312] Driving modes Virtual image distance (mm) urban low speed 3000 ordinary roads 5500 high speed 8000

[0313] 2. Zoom control logic

[0314] • If the vehicle speed is less than 30km / h, it will automatically switch to a close focal length (3m) to facilitate the display of parking assistance information.

[0315] • If the vehicle speed is between 30km / h and 80km / h, it will automatically switch to the medium focal length (5.5m) to display navigation and driving-related information.

[0316] • If the vehicle speed is higher than 80km / h, switch to the far focal plane (8m) to avoid the driver frequently adjusting the focus.

[0317] 3. User Interaction

[0318] The HUD system also offers a "manual mode," allowing drivers to select the virtual image distance according to their personal preferences, further enhancing the user experience.

[0319] V. Beneficial Effects

[0320] The three-segment zoom HUD system of this invention achieves the following through optical system optimization, freeform surface mirror design, and dynamic zoom algorithm:

[0321] Seamless switching between three focal planes improves adaptability to driving information;

[0322] A single image generation unit plus a single freeform surface mirror significantly reduces system costs;

[0323] The dynamic zoom control algorithm enables a smooth transition in virtual image distance;

[0324] This invention effectively breaks through the limitations of traditional HUDs with single focal plane and off-axis dual focal plane, providing an innovative solution for the development of automotive HUD technology and having significant engineering application value.

[0325] In one specific embodiment, for the variable focal plane HUD system of the present invention, in addition to vehicle speed, the dynamic switching of HUD virtual image distance can also be combined with various driving status data to achieve more precise and intelligent virtual image focal plane switching control.

[0326] Below are typical parameters and logic that can be used to trigger or assist in controlling the switching of the three virtual image distances:

[0327] 1. Vehicle Speed ​​[Main Control Dimension]

[0328] ●Low speed (0–30km / h) → Switch to near focus (3m) for parking assistance and lane departure warning;

[0329] ● Medium speed (30–80 km / h) → Medium focal length (5.5m), suitable for urban navigation and speed information;

[0330] ●High speed (>80km / h) →Long focal length (8m), suitable for long-range early warning such as navigation assistance on high-grade highways.

[0331] 2. Status of driver assistance systems (ADAS / ACC / LKA, etc.)

[0332] ●When ACC (Adaptive Cruise Control) is activated, it is recommended to use a medium-to-long focal length to highlight information related to the distance to the vehicle in front.

[0333] ●When LKA (Lane Keeping Assist) is in intervention mode → use the near-mid focal plane to enhance image guidance;

[0334] ●When AEB (Automatic Emergency Braking) is triggered, it quickly switches to the near focus plane to clearly display the risk icon or warning.

[0335] 3. Navigation system prompts (TBT / Turn Prompt)

[0336] ● Approaching an intersection (e.g., turning within 100m) → Switch to the near focus plane, with the icon close to the driver's line of sight for quick response;

[0337] ● Long distance straight travel → Automatically switches to medium to far focal plane to avoid focus disturbance caused by frequent switching.

[0338] 4. Gear and Braking Status

[0339] ● Engage reverse / park (R / P) gear → Automatically switch to near focus to display parking assist information;

[0340] ● Lightly apply the brakes to enter a "temporary stop" state → maintain the current focal plane;

[0341] ● Press and hold the brake (e.g., while waiting at a red light) → This will return you to the center view to display more vehicle / map information.

[0342] 5. Driver's line of sight / gaze area (DMS linked) [Enhanced experience]

[0343] If the system integrates a DMS (Driver Monitoring System), it can determine the most suitable focal length based on the direction of the driver's gaze.

[0344] ● Focus on the central control area → The HUD will automatically switch to the central focus area;

[0345] ● Focus on the distant view ahead → Automatically switch to the focal plane to display information related to the vehicle / road ahead.

[0346] The dynamic zoom control algorithm of this invention not only automatically switches between three focal planes based on the vehicle's real-time speed, but also combines multiple parameters in the vehicle's driving state for composite judgment, including but not limited to: ADAS system status (ACC, AEB, LKA, etc.), navigation system prompt distance, current gear and braking status, and driver's gaze direction (if a DMS module is available), to achieve more precise and intelligent adjustment of the virtual image distance. Through a multi-parameter fusion decision-making strategy, the HUD virtual image can be smoothly switched in different scenarios, maximizing the readability and adaptability of image information.

[0347] The "three-segment zoom head-up display (HUD) optical path system, vehicle-mounted head-up display device, and motor vehicle" proposed in this invention overcomes the limitations of traditional HUD systems, achieving dynamic zoom of the virtual image distance, enhanced depth perception of displayed information, and a significant reduction in system cost. Compared with existing technologies, this invention has the following significant advantages:

[0348] I. Breaking through the traditional HUD's single virtual image distance limitation, improving the adaptability and readability of driving information.

[0349] Existing technological shortcomings:

[0350] Traditional HUD systems use a single fixed focal plane optical structure with a fixed virtual image distance, which cannot meet the needs of switching between multiple scenarios such as high-speed driving, low-speed urban driving, and parking.

[0351] • When driving at high speeds, a longer virtual image distance is more suitable for quickly browsing navigation and road information; while when driving and parking in the city, a shorter virtual image distance is more suitable for displaying information such as lane departure warnings and parking assistance.

[0352] Advantages of this invention:

[0353] This invention optimizes the design of three virtual image focal planes (3m, 5.5m, and 8m) using CODE V software, enabling the switching of different virtual image distances according to the driving environment, thereby achieving dynamic information switching and enhanced adaptability.

[0354] • These three focal planes, combined with a dynamic zoom algorithm, can adjust the position of the virtual image in real time without changing the driver's line of sight, thus avoiding discomfort caused by the driver's inability to adapt to the viewing distance.

[0355] • By optimizing the optical path design, we ensure that clear imaging results can be obtained under each focal plane, thereby meeting the needs of various scenarios such as low-speed driving in cities, congested roads, national highways, and high-speed driving.

[0356] Comparison of effects:

[0357] Compared to traditional HUD systems, this invention significantly improves the readability and adaptability of driving information, reduces the burden on drivers to frequently move their eyes in different scenarios, and enhances driving safety and comfort.

[0358] II. Reduce system costs and achieve more economical and efficient optical structures

[0359] Existing technological shortcomings:

[0360] Currently, most HUD systems that break through the distance limitation of a single virtual image adopt the "dual image source + dual optical path" or "multiple freeform surface reflectors" scheme. This design requires an additional image display unit or as many as 3-4 freeform surface reflectors, which is complex in structure, expensive to manufacture, and increases the system size, affecting the integration of the whole vehicle.

[0361] Advantages of this invention:

[0362] The present invention adopts a design of "single image generation unit + single freeform surface mirror". Combined with the precise calculation of zoom curve, by adjusting the size of the image generation unit and the position of PGU (image generation unit), the three-segment focal plane switching and continuous zoom function can be realized.

[0363] This method avoids the increased cost and assembly complexity caused by hardware stacking in dual-image-source or multi-freeform surface reflector schemes.

[0364] Cost comparison:

[0365] According to calculations, the optical system structure of this invention reduces material and manufacturing costs by approximately 60% compared to the "dual image source + dual optical path" solution. It achieves effective cost control without affecting performance, providing an economical and feasible solution for the large-scale application of HUD systems.

[0366] Third, breaking through the fixed focal length limitation of traditional HUD systems to achieve dynamic zoom.

[0367] Existing technological shortcomings:

[0368] Traditional dual-focal-plane HUD systems only have two fixed focal planes and lack zoom functionality, making it difficult to provide a smooth sense of continuous information switching in complex driving environments.

[0369] • In a dual-focal-length HUD system, the display content for different focal lengths requires separate design of image generation units and optical systems, which lacks flexibility.

[0370] • In off-axis dual-focal-plane HUD systems, the downward viewing angles of the near and far focal planes are usually quite different. This requires the driver to adjust their line of sight to focus clearly on one of the virtual image planes, which is inconvenient and poses a risk of fatigue during long-distance driving.

[0371] Advantages of this invention:

[0372] This invention calculates a zoom curve using CODE V, which describes the relationship between the object distance (distance from PGU to the mirror), the virtual image distance, and the UI (image generation unit) size.

[0373] This method allows the HUD system to achieve a continuous transition between three focal planes, realizing the "dynamic zoom" function and making the information display more three-dimensional.

[0374] • By combining vehicle speed sensors, ADAS data, and navigation systems, the virtual image distance of the HUD can be automatically adjusted according to the driving scenario, thereby enhancing the driver's visual experience.

[0375] Comparison of effects:

[0376] Compared to traditional fixed-focal-area HUDs, this invention enables seamless transition of image content when switching virtual image distances, eliminating abruptness during information switching and enhancing the immersive experience of the HUD system and the driving experience.

[0377] Summarize

[0378] The three-segment zoom HUD optical path system of the present invention has the following outstanding advantages:

[0379] Multi-focal length switching: Breaking through the limitations of a single focal plane, it meets the driving needs of multiple scenarios such as urban areas, national highways, and expressways;

[0380] Continuous zoom function: By optimizing the zoom curve, a seamless transition is achieved when switching focal planes, significantly enhancing the immersiveness and depth of the HUD;

[0381] More cost-effective: It adopts a "single image generation unit + single freeform surface reflector" design, avoiding the high cost problem caused by dual optical path solutions;

[0382] Image quality improvement: The optimized design of the freeform surface mirror significantly improves imaging clarity and reduces distortion and astigmatism;

[0383] This invention represents a significant improvement in performance, cost, and applicability, providing new solutions and methods for the innovation and popularization of vehicle HUD technology.

[0384] Example 2

[0385] I. Detailed Explanation of Zoom Control Decision Point Path Based on System Block Diagram:

[0386] The HUD virtual image distance zoom control system of this invention receives real-time information such as vehicle speed, ADAS status, navigation prompts, gear status, braking status, and / or driver monitoring system (DMS) (optional) via vehicle bus (CAN or Ethernet), and then inputs this information into the driving state integrated decision unit to calculate the real-time target virtual image distance. Figure 6 As shown, the specific control decision path is as follows:

[0387] ●Step 1:

[0388] Real-time vehicle information input (CAN bus / Ethernet)

[0389] This includes: vehicle speed, ADAS status, navigation prompts, gear status, braking status, and DMS status.

[0390] ●Step 2:

[0391] Driving Status Integrated Decision Unit

[0392] By integrating various real-time vehicle status information, the most suitable target virtual image distance is calculated.

[0393] ●Step 3:

[0394] Determine if the current virtual image distance of the HUD system meets the requirements of the current driving state:

[0395] ◆If “Yes”, the system will directly maintain the current virtual image distance and return the real-time status of the monitored vehicle.

[0396] ◆If “No”, proceed to the next decision-making level.

[0397] ●Step 4 (Key Decision Point 1):

[0398] Determine whether the current driving behavior is in a stable state (such as cruising, constant speed, or long-term parking / waiting):

[0399] ◆If “stable”, the system will increase the focal length switching integration threshold or extend the integration evaluation time;

[0400] ◆If “unstable”, the system will use the normal integration threshold for subsequent focal length integration evaluation.

[0401] ●Step 5 (Key Decision Point 2):

[0402] Based on the integral evaluation criteria in step 4, perform "focal length inertia integral evaluation" to determine whether the focal length integral has reached the switching threshold:

[0403] ◆If the integral "does not reach the threshold", then maintain the current virtual image distance;

[0404] ◆If the score "reaches the threshold", proceed to the next step.

[0405] ●Step 6 (Key Decision Point 3):

[0406] After the focal length integration is satisfied, it is determined whether the interval since the last virtual image distance switching exceeds a preset delay threshold:

[0407] ◆If the threshold is not exceeded, the system will continue to maintain the current virtual image distance;

[0408] ◆If the threshold is exceeded, virtual image distance switching will be performed.

[0409] ●Step 7:

[0410] When switching virtual image distances, a smooth transition mechanism using image animation is employed to reduce the driver's visual adjustment burden.

[0411] ●Step 8:

[0412] Update the current virtual image distance status of the HUD system and continue to monitor vehicle driving information in real time for iterative decision-making.

[0413] Furthermore, to avoid visual fatigue caused by frequent adjustments during dynamic zooming, this invention designs a focal length switching suppression mechanism that integrates "hysteresis threshold" and "inertial integral weight":

[0414] ●Hysteresis threshold mechanism:

[0415] Set a minimum time interval threshold (e.g., 2-5 seconds) between two consecutive switching of the virtual image distance to avoid frequent fluctuations in the HUD virtual image distance due to short-term fluctuations or transient changes in vehicle status, thereby effectively reducing visual fatigue.

[0416] ●Inertial integral weighting mechanism:

[0417] When the distance to the HUD target virtual image changes, the focus is not changed immediately. Instead, the "focal length integration" is continuously evaluated. Only when the accumulated condition is met (the integration value exceeds a preset threshold) is the zoom switching operation officially triggered.

[0418] Further reduce the sensitivity to changes in virtual image distance.

[0419] ●Special handling when driving behavior is stable:

[0420] When the system determines that the driving behavior is stable (such as high-speed cruising, long-term constant speed driving, long-term waiting), it automatically increases the integration threshold or extends the integration accumulation time to further enhance the suppression effect of frequent zooming.

[0421] ● Smooth animation transition mechanism:

[0422] When switching focal lengths, the HUD image display uses a gradual animation effect (such as gradually zooming in / out) to avoid the impact of sudden visual changes on the driver's vision.

[0423] Example 3

[0424] The driving state integrated decision unit is a logic control module that dynamically determines the distance to the HUD target virtual image based on various real-time vehicle state data. Its function is to intelligently determine the most suitable HUD virtual image distance during vehicle operation, based on information such as current vehicle speed, driver assistance system (ADAS) status, navigation prompts, gear position, braking status, and driver gaze direction (DMS).

[0425] The specific functions of the integrated decision-making unit for driving status are as follows:

[0426] Input information includes:

[0427] ●Vehicle speed information (CAN bus)

[0428] ◆Low speed (≤30km / h), medium speed (30-80km / h), high speed (≥80km / h)

[0429] ●ADAS System Status

[0430] ◆ACC (Adaptive Cruise Control)

[0431] ◆LKA (Lane Keeping Assist)

[0432] ◆AEB (Automatic Emergency Braking)

[0433] ●Navigation Information

[0434] ◆ Distance from the turning point (far, medium, near)

[0435] ◆Current navigation prompt type (straight ahead, turn left, turn right, U-turn)

[0436] ● Gear Status

[0437] ◆Park (P), Reverse (R), Neutral (N), Drive (D)

[0438] ● Braking status

[0439] ◆No braking, light application of the brakes, complete stop

[0440] ● Driver Monitoring System (DMS)

[0441] ◆ Driver's line of sight area (distant view, instrument panel, center console)

[0442] Methods for calculating and deciding the distance to the virtual image of the target:

[0443] The driving state integrated decision unit typically calculates the target virtual image distance using a rule-based judgment + weighted integration method:

[0444] First, a suggested virtual image distance is defined based on each input information, as shown in Table 4:

[0445] Table 4. Correspondence between Input Status and Suggested Focal Length

[0446]

[0447] Then these inputs are combined and integrated or prioritized in the form of weights:

[0448] For example:

[0449] Focal length score = W 车速 *Recommended focal length + W ADAS *Recommended focal length + W 导航 *Recommended focal length + W 档位 *Recommended focal length + W 制动 *Recommended focal length + W DMS *Recommended focal length

[0450] in:

[0451] Wx represents the weight of each state (e.g., vehicle speed may have a higher weight, navigation has a lower weight, and DMS has a lower weight).

[0452] The final focal length score is as follows: the highest score is for the near focal length → near focal plane (3m); the highest score is for the medium focal length → medium focal plane (5.5m); the highest score is for the telephoto focal length → telephoto focal plane (8m).

[0453] In the actual implementation process, the specific weight allocation and decision-making need to be determined in combination with the actual situation, laws and regulations, customer requirements, and market research.

[0454] The role of the integrated decision-making unit for driving status:

[0455] ● Improve the compatibility of HUD images with actual driving scenarios and avoid information interference;

[0456] ● Intelligent decision-making regarding the timing and necessity of focal length switching reduces frequent switching and avoids visual fatigue;

[0457] ● Optimize the driver's human-machine experience, improving overall driving safety and comfort. Example 4

[0458] Focal length inertia integral refers to a "stabilization control strategy" designed in HUD dynamic zoom control to avoid visual fatigue caused by frequent focal length switching. In simpler terms, its function is:

[0459] ●When the initial conditions for switching focal lengths are met (such as changes in vehicle speed or ADAS status), the virtual image distance switching is not performed immediately.

[0460] ● Instead, it uses an integrated or cumulative mechanism to continuously assess the gap in importance or necessity between the current focal length and the target focal length.

[0461] ●Focus switching is only officially triggered when the cumulative value (integrated value) of this gap exceeds a preset threshold.

[0462] Simple example explanation:

[0463] Assuming the current focal length is "mid focal length (5.5 meters)," the vehicle status suddenly prompts a switch to "telephoto focal length (8 meters)":

[0464] ●The system begins accumulating points and records the duration or degree to which the switching conditions are met consecutively;

[0465] ●The telephoto switching will only officially begin if the conditions for continuous telephoto switching are met and a certain threshold is reached (e.g., the integral value exceeds the set threshold).

[0466] ●If the state returns to a state that does not require switching during the process, the score is reset to zero and no switching is performed.

[0467] Advantages of using focal length inertial integration:

[0468] ●Prevent the HUD from frequently zooming due to transient or brief fluctuations in vehicle speed;

[0469] ● Improves visual stability and reduces driver visual strain and fatigue;

[0470] ● Ensure that the zoom control logic is more rational and ergonomic.

[0471] In the process, when "the current virtual image distance does not meet the requirements," regardless of whether the driving behavior is stable, it will enter the "evaluation of focal length inertial integral" stage. The main purpose of this design is:

[0472] 1. Prevent frequent focal length switching:

[0473] Even if the driving state changes, in order to avoid the system frequently responding to short-term, small fluctuations (such as slight speed changes), an inertial integral mechanism is needed to ensure that the switching decision is more stable and meaningful.

[0474] 2. Special considerations for stable driving behavior:

[0475] If the driving state is stable (such as constant speed cruising or long-term parking), although the system logic detects that the current virtual image distance no longer matches the instantaneous state, it is still necessary to confirm whether this deviation lasts for a long enough time or is significant enough before it is worthwhile to switch the virtual image.

[0476] For example, during high-speed cruising, occasional brief and slight deceleration or changes in navigation prompts are not enough to immediately trigger a change in focus.

[0477] 3. Handling unstable driving behavior:

[0478] If driving behavior is unstable (such as frequent acceleration and deceleration, or drastic changes in navigation prompts), the system needs an inertial integration mechanism to suppress frequent focal length jumps. In this case, the focal length integration mechanism plays a key role in stabilizing system behavior and preventing visual fatigue.

[0479] This method is similar to "hysteresis" or "hysteresis control" in control systems. By introducing an integral buffer, it ensures that focal length switching decisions are more stable and reliable.

[0480] When the current virtual image distance does not meet the requirements, prioritize determining whether the driving behavior is stable:

[0481] ●If driving behavior is stable, the points threshold can be increased or the points time can be extended to avoid overly sensitive switching.

[0482] ●If driving behavior is unstable, normal score evaluation will be performed to prevent frequent focus switching.

[0483] This logical design more clearly reflects the impact of driving behavior stability on focus switching sensitivity.

[0484] Example 5

[0485] Traditional car head-up displays (HUDs) typically have only a fixed virtual image focal length (e.g., fixed at approximately 2-3 meters). This means that drivers need to frequently adjust their eye focus between viewing HUD information and looking at distant road targets. Repeatedly switching between vertical and horizontal vision and changing focus increases eye strain, potentially leading to eye fatigue and reduced driving performance. In fact, one of the original intentions of introducing HUDs was to reduce the frequency with which drivers' eyes leave the road: compared to looking down at the instrument panel, HUDs project key information in front of the driver's line of sight, reducing the number of times the driver needs to look down at the instrument panel and shortening eye movement time. However, in traditional HUDs with only a single focal length, although the eyes do not need to shift their gaze vertically, they still need to adjust their focus back and forth between "distant road scenery" and "near-field HUD display." This frequent adjustment increases visual fatigue.

[0486] Multi-focal-length or variable-focus HUDs were developed to address these issues. These HUDs project different types of information onto different depth positions using multiple virtual image distances (or continuously variable virtual image distances), allowing virtual images to blend more accurately with the real environment. This reduces the adjustment range required by the driver's eyes, resulting in more natural focus adaptation and a relatively lower frequency of gaze switching. For example, research reports indicate that compared to fixed single-focal-length HUDs, AR-HUDs can dynamically adjust the imaging distance according to vehicle speed, conforming to the physiological laws of human eye focus switching during driving. Researchers at Cambridge University also emphasize that achieving multi-focal-length display is one of the important challenges facing automotive AR-HUDs, in order to project AR cues at the correct distance without sacrificing the field of view, thereby reducing eye strain caused by viewing distance mismatch. [5] Overall, both theoretical analysis and design schemes anticipate that increasing the imaging depth dimension of the HUD (such as dual-focal, trifocal, or even continuous zoom) will help reduce the number of times the driver's eyes need to refocus, thereby improving visual comfort.

[0487] In recent years, a series of comparative experiments in simulated and real-vehicle environments have been conducted to address the differences in human factors between fixed-focus HUDs and multi-focus HUDs. Among these, dual-focus HUDs (two virtual imaging distances) are the most studied and have provided validation for "three-segment zoom HUDs." Chen et al. (2023) used HoloLens 2 to simulate a "dual-depth HUD," allowing drivers to alternate between single-depth and dual-depth HUDs during a 90-minute driving task. They used physiological indicators such as electroencephalography (EEG) and electrooculography (EOG, blink frequency) combined with the NASA-TLX subjective workload questionnaire to assess fatigue during long-distance driving. Key experimental findings include:

[0488] Blink frequency (visual fatigue index): In the first 5 minutes of driving, the blink frequency of drivers under single-focus HUD conditions was significantly higher than that under dual-focus HUD conditions (p = 0.037), indicating a stronger trend of visual fatigue. During the first half of the driving process (the first 45 minutes), the average blink frequency of the single-focus HUD group was consistently higher than that of the dual-focus HUD group, meaning that the early visual fatigue accumulation caused by single-focus HUD was more significant. This is consistent with the expectation that the human eye is more prone to fatigue when it needs to frequently refocus.

[0489] Subjective workload: NASA-TLX questionnaire results showed that the subjective workload score for single-focus HUDs was significantly higher than that for dual-focus HUDs (significantly higher mean score, p = 0.048). In other words, drivers generally felt that using a single-focus HUD was more "laborious" than using a dual-focus HUD, requiring more attention and mental resources. Researchers pointed out that this result is consistent with conclusions obtained from EEG physiological signals, proving that dual-focus HUDs do indeed have an advantage in reducing driving workload.

[0490] EEG cognitive load: By analyzing EEG indicators across various frequency bands, the study found that single-focus HUDs induced significantly higher levels of driver fatigue than dual-focus HUDs for most of the time periods, while dual-focus HUDs required relatively less mental effort from the driver. Combining physiological and subjective data, this study clearly concludes that dual-focus HUDs can effectively reduce the driver's visual perception burden and overall workload. This provides direct experimental evidence for the ergonomic advantages of multi-focus HUDs compared to traditional HUDs. [1] .

[0491] Furthermore, other studies have reported similar trends. A driving simulation experiment compared the effects of augmented reality head-up displays (AR-HUDs) with traditional displays, showing that AR-HUDs significantly improve drivers' attention to dangerous targets, reduce the difficulty of processing complex road information, and thus alleviate cognitive load. In dangerous nighttime scenarios, drivers using AR-HUDs perceived risks more quickly and reacted faster, enabling them to respond to high-risk situations more effectively. This suggests that when HUD content is integrated with the actual environment and may appear at a greater actual distance (AR-HUDs typically project a distant, virtual image), drivers perceive and make decisions more easily and efficiently. [2] Other researchers have designed multifocal plane AR-HUD interfaces and conducted user tests, verifying that multifocal solutions help improve driver reaction time and target acquisition capabilities, thereby enhancing driving safety. These studies all point to the fact that, compared to fixed single-focal-length displays, increasing the number of virtual image distances in the HUD (or dynamically adjusting the focal length) can reduce the driver's visual / cognitive burden and improve reaction efficiency in real-world driving situations.

[0492] The advantages of multi-focal length HUDs in reducing visual fatigue and improving comfort are also reflected in subjective feedback and long-term effects. Chen [1] In bifocal HUD experiments conducted by researchers, the subjective reports of eye fatigue varied significantly over time: with a monofocal HUD, the subjective fatigue scores from prolonged driving were higher, while with a bifocal HUD, the subjective fatigue was lower. Reduced subjective workload often means greater visual comfort and easier information acquisition for the driver. A review from Cambridge University indicated that holographic AR-HUDs with 3D depth rendering capabilities can shorten the time it takes for drivers to acquire information about road obstacles, reducing eye strain and driving stress levels. In other words, the correct virtual image distance allows drivers to see and understand road conditions more quickly, without the need to strain to focus, thus feeling more relaxed. [5] .

[0493] From the perspectives of optical principles and human eye physiology, reports also support the comfort advantages of multifocal HUDs. For example, Liu et al. (2023), in designing a compact bifocal AR-HUD, emphasized that multiple virtual image distances can avoid visual fatigue and cognitive performance decline caused by the mismatch between virtual and real distances in traditional HUDs. Another example is the development of light field AR-HUDs (which can be seen as continuous multifocal HUDs), where Chinese manufacturers generate a true depth-of-field effect through multiple layers of images at physically different distances. Compared to single-plane models that simulate distance by scaling near objects to larger ones and far objects to smaller ones, multifocal imaging provides a more realistic sense of distance. Drivers feel that the virtual UI matches the real intersection better in turning scenarios, resulting in a better experience. These subjective descriptions echo experimental data: multifocal HUDs make the position and size of virtual information more consistent with reality, reducing visual conflict and focusing discomfort, and drivers generally report a more natural viewing experience. [3][4] .

[0494] In summary, the three-stage zoom HUD, by displaying different information at three typical distances (near, medium, and far), can best match the physiological accommodation characteristics of the human eye. It has significant advantages in reducing eye movement and focusing fatigue, and the resulting improvement in visual comfort and fatigue relief has been strongly supported by the aforementioned human factors research and industry tests.

[0495] References

[0496] [1]Chen,C.-Y.,Chou,T.-A.,Chuang,C.-H.,Hsu,C.-C.,Chen,Y.-S.,&Huang,S.-H.(2024).Impact of Dual-Depth Head-Up Displays on Vehicle DriverPerformance.Applied Sciences,14(15),6441.https: / / doi.org / 10.3390 / app14156441

[0497] [2] Gabbard, JL, Mehra, DG, & Swan, JE (2019). Effects of AR DisplayContext Switching and Focal Distance Switching on Human Performance. IEEE transactions on visualization and computer graphics, 25(6), 2228–2241. https: / / doi.org / 10.1109 / TVCG.2018.2832633

[0498] [3] Hunan University, Huizhou Desay SV Automotive Electronics Co., Ltd. The Development Trend Report of AR HUD. Changsha: Hunan University; Huizhou: Huizhou Desay SV Automotive Electronics Co., Ltd; 2023.

[0499] [4]Wu,H.(2025).Revolutionizing EVs:A comprehensive analysis ofautomotive HUD technologies.Proceedings of the 3rd International Conference on Mechatronics and Smart Systems,125,20954.https: / / doi.org / 10.54254 / 2755-2721 / 125 / 2025.20954

[0500] [5]University of Cambridge.(2022).Augmented reality head-up displays–navigating the next-gen driving experience.https: / / www.eng.cam.ac.uk / news / augmented-reality-head-displays-navigating-next-gen-driving-experience

[0501] The scope of protection of this invention is not limited to the above embodiments. Any variations and advantages that can be conceived by those skilled in the art without departing from the spirit and scope of this invention are included in this invention and are protected by the appended claims.

Claims

1. A three-segment zoom head-up display optical path system, characterized in that, The optical path system includes: an image generation unit, a freeform surface mirror (5), and a zoom path optimization module; The image generation unit is used to generate an image beam, which is reflected by the freeform surface mirror (5) and then reflected by the windshield (10) to the driver's eye position to form a virtual image; The freeform surface mirror (5) supports imaging at different virtual image distances based on preset multi-segment surface parameters; The zoom path optimization module controls the distance between the image generation unit and the freeform surface mirror (5) according to the vehicle speed information, adjusts the virtual image distance, and realizes three-segment zoom display.

2. The optical path system as described in claim 1, characterized in that, Based on vehicle speed, navigation information, and ADAS system output, the system dynamically and automatically or manually selects three virtual image distances: near, medium, and far. And / or, The three-stage zoom creates different virtual image distances: a close focal plane at 3m, a medium focal plane at 5.5m, and a distant focal plane at 8m. And / or, When in automatic switching mode, if the vehicle speed is less than 30km / h, it will automatically switch to the close focal plane. If the vehicle speed is between 30km / h and 80km / h, it will automatically switch to the medium focal length. If the vehicle speed is higher than 80km / h, switch to the long focal plane; And / or, When in manual switching mode, you can manually control and adjust the near, medium and far distance of the display focal plane based on your actual observation while driving, and select the focal plane that best suits your current observation.

3. The optical path system as described in claim 1, characterized in that, The image generation unit includes: a backlight assembly (1) and a TFT screen (2); The image generation unit displays that the size of the image automatically adjusts as the distance to the virtual image changes, compensating for the influence of changes in the field of view on the field of view. And / or, The field of view remains constant, with a size of 9°*3°.

4. The optical path system as described in claim 1, characterized in that, The freeform surface mirror (5) adopts an XY polynomial surface shape with the highest order coefficient being 7th. Through optimization including multi-field asymmetric control, dynamic compensation of the principal ray tilt angle, and manufacturability slope constraint, it meets the imaging requirements of three virtual image distances. The optimization includes MTF, astigmatism, parallax, and distortion control indicators. And / or, A zoom curve is constructed to achieve a coordinated match between imaging quality and display consistency at multiple virtual image distances.

5. The optical path system as described in claim 4, characterized in that, The construction of the zoom curve includes the following steps: Step a. Build an optical simulation system, fix the field of view, set the virtual image distance range and sampling step size, and record the object distance and image source display size at each virtual image distance; Step b. Model and fit the data sampled in step a, and construct an interpolation function, as shown below: Among them, y i Let x represent the interpolation target value for the i-th sample point. i Let represent the interpolation input value of the i-th sample point, x represent the input value in the current real-time state, n represent the number of sample points participating in the interpolation, and j represent the inner loop variable of the multiplication symbol Π in the interpolation process, which is used to traverse all sample points to calculate the multiplication result of each term in the interpolation function.

6. The optical path system as described in claim 5, characterized in that, The construction of the optical simulation system includes the following steps: A basic model containing the object plane, eyepiece aperture, windshield, XY polynomial freeform surface mirror, and image plane is established in the lens data editor. Multiple configuration systems with different virtual image distances are set up, and zoom control is achieved by sharing the freeform surface mirror polynomial parameters. An optimization function containing multiple configuration constraints is constructed, with the RMS radius of the light spot, MTF≥0.4, principal ray alignment accuracy, and distortion<5% at each virtual image distance as core indicators. Local and / or global optimization is performed in conjunction with the physical constraints of the freeform surface coefficients. After optimization, the consistency of the virtual image size is verified through cross-configuration analysis, and optimized data including freeform surface polynomial coefficients, key VID parameter tables, and three-dimensional surface data is output.

7. The optical path system as described in claim 1, characterized in that, The optical path system adopts a multi-configuration joint optimization design of a single freeform surface mirror. Multiple focal length configurations are established in CODE V and the mirror XY polynomial parameters are shared. Through global optimization, a single mirror is compatible with a virtual image distance of 3000-8000mm, eliminating the focal plane offset distortion of traditional multi-mirror structures. And / or, Construct an optimization function with cross-focal length constraints to simultaneously control the Spot RMS radius, MTF, and image center drift constraints of each focal length, thereby suppressing image jumps caused by optimization of a single focal length. And / or, An image size-object distance synchronous zoom model is introduced. By adjusting the PGU display size, the virtual image distance is compensated for, maintaining a constant field of view of 9°×3° from the driver's perspective, thus avoiding edge distortion and field of view compression.

8. The optical path system as described in claim 1, characterized in that, Based on real-time data collected from the vehicle bus, including vehicle speed, ADAS status, navigation prompts, gear position, braking signals, and / or driver monitoring system data, the driving state integrated decision unit analyzes the driving scenario and driver focus to make zoom control decisions and dynamically calculates and adjusts the HUD virtual image distance target value.

9. The optical path system as described in claim 8, characterized in that, During zoom control, a hysteresis threshold control mechanism is set, which sets the minimum time interval threshold between two consecutive switching of virtual image distance; And / or, During zoom control, a focal length inertial integral weight evaluation mechanism is set up. When the system determines that the current virtual image distance does not meet the driving state requirements, the necessity of switching is evaluated by integral method. Virtual image distance switching is only performed when the integral value reaches the preset threshold.

10. The method as described in claim 9, characterized in that, The integration threshold or integration time is dynamically increased when the system determines that the driving behavior is in a stable state. And / or, During the virtual image distance switching process, the system executes a gradual animation for a smooth transition.

11. The optical path system as described in claim 1, characterized in that, The optical path system also includes a dustproof plate (6) and a HUD housing (7). The dustproof plate (6) is positioned above the image generation unit and the freeform surface mirror (5) for dust and water protection. The HUD housing (7) is used to install, fix, and protect the internal components.

12. A vehicle-mounted head-up display device, characterized in that, Includes the optical path system according to any one of claims 1-11, and a vehicle mounting bracket for mounting the optical path system.

13. A motor vehicle, characterized in that, Includes the vehicle body and the in-vehicle head-up display as described in claim 12, the in-vehicle head-up display being integrated into the space between the vehicle dashboard and the windshield (10).

14. A method for adjusting the optical path of a head-up display with three-segment zoom, characterized in that, Includes the following steps: Step 1: Obtain real-time vehicle driving status information, including vehicle speed, navigation prompts, driver assistance system status, gear status, braking signals and / or driver monitoring system data; Step 2: Based on the driving status information, determine the target virtual image distance through the driving status integrated decision unit; Step 3: Based on the distance to the target virtual image, control the change in object distance between the image generation unit and the freeform surface mirror, and simultaneously adjust the display size of the image generation unit to compensate for changes in the field of view and maintain a preset constant field of view. Step 4: Based on the image size adjustment and object distance change, the image beam is reflected by a freeform surface mirror and then reflected through the windshield to the driver's eye position to form a virtual image of the target; Step 5: During the virtual image distance switching process, a hysteresis threshold control mechanism and a focal length inertial integral evaluation mechanism are applied to perform a smooth transition switching of the virtual image.

15. The method as described in claim 14, characterized in that, The hysteresis threshold control mechanism sets a minimum time interval threshold between two consecutive switching of the virtual image distance; And / or, The focal length inertial integral weight evaluation mechanism evaluates the necessity of switching by integral method when the system determines that the current virtual image distance does not meet the driving state requirements. Virtual image distance switching is only performed when the integral value reaches a preset threshold.

16. The method as described in claim 15, characterized in that, The integration threshold or integration time is dynamically increased when the system determines that the driving behavior is in a stable state. And / or, During the virtual image distance switching process, the system executes a gradual animation for a smooth transition.

17. The application of the optical path system as described in any one of claims 1-11, the vehicle head-up display device as described in claim 12, the motor vehicle as described in claim 13, or the control method as described in any one of claims 14-16 in vehicle driving information prompts, driving assistance information displays, and augmented reality navigation guidance.

Images