Vehicle head-up display and control method thereof

Abstract

The present application relates to the technical field of display, especially to a vehicle-mounted head-up display and a control method thereof.The vehicle-mounted head-up display comprises a main frame, a light source assembly and an optical assembly.The main frame comprises a heat conduction member, a middle frame and a glue shell.The middle frame is connected with the heat conduction member, and the glue shell is connected with the middle frame.The middle frame is located between the heat conduction member and the glue shell.The light source assembly is arranged at the bottom of the main frame.The light source assembly comprises a circuit board, and a light emitting unit is arranged on the circuit board.The light emitting unit is located on the side of the circuit board which is away from the bottom of the heat conduction member.The optical assembly is located above the light source assembly.The optical assembly comprises a diffusion plate and a light scattering film which are arranged in a stacking manner along the light emitting direction.A heat conduction glue layer is arranged between the circuit board and the heat conduction member.The present application can improve the visual comfort and the heat dissipation effect of the display.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of display, in particular to a vehicle head-up display and a control method thereof. BACKGROUND

[0002] With the development of intelligent cockpit and driving assistance system, the vehicle head-up display (HUD) has become an important component to improve driving safety and human-computer interaction experience. The HUD in the prior art usually includes a light source module, an optical module and a shell structure, and the main shell structure is usually a single plastic or metal integrated part, which bears multiple functions such as support, positioning and heat dissipation. However, the LED light source and control circuit in the existing HUD are directly installed on the plastic or sheet metal shell, and there is a lack of specially designed heat conduction path and heat conduction interface, which leads to high LED operating temperature, affecting the service life and stability of the light source. The current HUD usually only uses a single diffusion plate or a light diffusing film for light diffusion, which cannot fully eliminate local bright spots and light spot distortion, resulting in uneven brightness in the display area and reducing visual comfort. SUMMARY

[0003] Therefore, the embodiments of the present application provide a vehicle head-up display to solve the technical problems of poor heat dissipation effect and low visual comfort of the existing vehicle head-up display.

[0004] In a first aspect, the present application provides a vehicle head-up display, comprising:

[0005] A main body frame comprising a heat conduction member, a middle frame and a glue shell, the middle frame is connected with the heat conduction member, the glue shell is connected with the middle frame, and the middle frame is located between the heat conduction member and the glue shell;

[0006] A light source assembly is arranged at the bottom of the main body frame, the light source assembly comprises a circuit board, the circuit board is provided with a light emitting unit, and the light emitting unit is located on the side of the circuit board away from the bottom of the heat conduction member;

[0007] An optical assembly is located above the light source assembly, the optical assembly comprises a diffusion plate and a light diffusing film which are stacked along the light emitting direction;

[0008] A heat conduction glue layer is arranged between the circuit board and the heat conduction member.

[0009] In a second aspect, the present application further provides a vehicle head-up display control method, the method comprising:

[0010] According to the average brightness and the proportion of bright area of the image to be displayed, a target virtual image brightness value after projection is obtained;

[0011] According to the target virtual image brightness, a corresponding target current value is determined;

[0012] According to the night anti-dazzling upper limit curve and the daytime visible lower limit curve in the vehicle, the target current value is clipped to obtain a limited target current value;

[0013] According to the light source assembly temperature information collected by the temperature sensor, the limited target current value is dynamically temperature-compensated and adjusted.

[0014] In summary, the beneficial effects of the present application are as follows:

[0015] The vehicle-mounted head-up display and the control method thereof provided by the present application adopt a heat-conducting piece, a middle frame and a glue shell to constitute a main frame, the middle frame is connected with the heat-conducting piece and the glue shell at the same time, the light source assembly and the optical assembly are supported and fixed by the main frame, the support, positioning and fixing functions of each assembly are integrated, the relative position accuracy between each component is ensured, and the assembly process is simplified, and the production efficiency is improved. The present application sets a heat-conducting glue layer between the circuit board and the heat-conducting piece, so that the heat generated by the light-emitting unit can be quickly and uniformly conducted to the heat-conducting piece, the working temperature of the LED is significantly reduced, the heat dissipation efficiency is improved, and the service life of the light source and the driving circuit is prolonged. The present application adopts a diffusion plate and a light dispersing film arranged in layers to constitute the optical assembly, the diffusion plate realizes large-range primary light guiding, the light dispersing film further disperses the light spot, and the two work together to effectively eliminate local bright spots and ensure the brightness uniformity and visual comfort of the head-up display picture. The present application uses the middle frame as an inner support to rigidly connect the light source assembly and the optical assembly between the heat-conducting piece and the glue shell, forms a firm sandwich structure, enhances the anti-vibration ability of the whole machine, and ensures that the components in each layer will not be dislocated or loose during the operation of the vehicle. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments of the present application. For those skilled in the art, other drawings can also be obtained on the premise of not creating labor, and these are within the protection scope of the present application.

[0017] Figure 1 is the exploded structure schematic diagram of the vehicle-mounted head-up display of the present application.

[0018] Figure 2 is the structure schematic diagram of the reflector of the present application.

[0019] Figure 3 is the structure schematic diagram of the diffusion plate lug of the present application.

[0020] Figure 4 is the interface circuit diagram of the vehicle-mounted head-up display of the present application.

[0021] Figure 5 is the temperature detection circuit diagram in the present application.

[0022] Figure 6 The circuit diagram of the Schmidt trigger buffer circuit in the present application.

[0023] Figure 7 The circuit diagram of the LED driver in the present application.

[0024] Figure 8 The flowchart of the vehicle-mounted head-up display control method of the present application. DETAILED DESCRIPTION

[0025] The features and exemplary embodiments of various aspects of the present application will be described below in detail, in order to make the purposes, technical solutions and advantages of the present application more clear and apparent, the present application will be further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only configured to explain the present application, and are not configured to limit the present application. The present application can be implemented without some of these specific details for those skilled in the art. The following description of the embodiments is only to provide a better understanding of the present application by showing examples of the present application.

[0026] It should be noted that, in this paper, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment. Without more limitations, the elements defined by the statement "include" do not exclude the presence of other identical elements in the process, method, article or equipment including the elements.

[0027] It should be noted that all the actions of obtaining signals, information or data in the present application are carried out in accordance with the corresponding data protection regulations and policies of the place, and with the authorization given by the owner of the corresponding device.

[0028] Embodiment 1

[0029] Please see Figure 1 The present embodiment provides a vehicle-mounted head-up display, which comprises a main frame light source assembly and an optical assembly:

[0030] The main frame comprises a heat-conducting member, a middle frame and a glue shell, the middle frame is connected with the heat-conducting member, the glue shell is connected with the middle frame, and the middle frame is located between the heat-conducting member and the glue shell.

[0031] The heat conduction member is usually a metal die casting for bearing the circuit board and quickly dissipating heat; the middle frame is a plastic or light alloy member as an internal support member for connecting and positioning the heat conduction member with the glue shell; and the glue shell is an external plastic shell for providing dustproof, moistureproof and appearance protection for the whole display.

[0032] The light source assembly is arranged at the bottom of the main frame, and the light source assembly comprises a circuit board, and a light emitting unit is arranged on the circuit board and located on the side of the circuit board away from the bottom of the heat conduction member;

[0033] The light emitting unit usually adopts a surface-mounted LED or Micro-LED chip, is welded on the circuit board, faces the optical assembly, and is the core of the light source assembly. The technical scheme uniformly supports and positions the light source assembly and the optical assembly through the main frame, ensures accurate superposition of each component along the light emitting direction, and forms a stable mechanical and optical channel.

[0034] The optical assembly is located above the light source assembly, and the optical assembly comprises a diffusion plate and a light dispersing film arranged in layers along the light emitting direction;

[0035] A heat conduction glue layer is arranged between the circuit board and the heat conduction member.

[0036] The implementation of the present application firstly installs the heat conduction member on a production tooling and pastes a heat conduction glue layer on the heat conduction member; then pastes the circuit board provided with the light emitting unit on the heat conduction member, fills the gap between the two with the heat conduction glue; then sleeves the middle frame on the periphery of the heat conduction member and the circuit board, and fixes the two through preset clamping or screws; then inserts the diffusion plate and the light dispersing film in the middle frame in sequence, with the diffusion plate facing the circuit board, the multi-point positioning lugs being firmly matched with the middle frame, and the light dispersing film being tightly attached to the diffusion plate; and finally buckles the middle frame assembly that has been assembled into the glue shell, and the glue shell is sealingly overlapped with the periphery of the middle frame, to complete the overall assembly.

[0037] The foregoing scheme can realize modular production and assembly, significantly improve positioning accuracy and yield, the efficient heat conduction path of the heat conduction glue layer and the metal heat conduction member can greatly reduce performance degradation caused by LED heating, the synergistic effect of the diffusion plate and the light dispersing film can effectively eliminate local bright spots and improve light emitting uniformity, and the sandwich structure of the metal heat conduction member, the middle frame and the glue shell enhances mechanical strength and vibration resistance, while ensuring compact size and reliable environmental sealing of the product.

[0038] In the embodiment, the optical assembly further comprises a reflector cup, which is arranged on the side of the diffusion plate facing the light source assembly.

[0039] The light-reflecting cover can be a plastic part integrally injection molded, and the inner surface thereof is polished or vacuum-coated with aluminum to have a high-reflectivity mirror surface for receiving and reflecting light rays emitted from the diffuser plate toward the light source assembly. The light-reflecting cover is arranged on the side of the diffuser plate facing the light source assembly to form a closed reflection cavity between the diffuser plate and the light source, so that light rays originally scattered backward and laterally are redirected back to the diffuser plate and subsequent optical layers, thereby achieving secondary utilization of the light path and improving the overall light extraction efficiency.

[0040] The light-reflecting cover can be fixed by a buckle at a reserved clamping position of the middle frame or the glue shell. A microporous foam or sealant can also be laid on the contact surface between the light-reflecting cover and the middle frame to improve the air tightness of the light-reflecting cavity and the integrity of the reflection surface.

[0041] In combination with the close fit between the light-reflecting cover and the diffuser plate, the present application can effectively recover scattered light at the edge and in the backward direction, reduce light loss, and significantly improve the light extraction brightness. At the same time, due to the accurate direction of light rays by the light-reflecting cover, the present application can reduce stray light and glare, improve display contrast and picture clarity, and reduce system power consumption and dependence on higher-power light sources.

[0042] As shown in Figure 2 The light-reflecting cover is provided with a light-reflecting unit corresponding to each light-emitting unit, and at least a part of the light-emitting unit is located in the corresponding light-reflecting unit.

[0043] The light-reflecting unit refers to a reflection groove or cylindrical mirror surface structure reserved on the inner surface of the light-reflecting cover for a single light-emitting unit, such as a rectangular or circular cup-shaped cavity, the inner wall of which is mirror-polished or vacuum-coated with aluminum for concentrating and directionally reflecting light rays emitted by the light-emitting unit (such as a part of a SMD LED chip or a hemispherical lens) placed therein. This technical solution realizes accurate positioning of the light-emitting unit and the reflection cavity by one-to-one setting of the corresponding light-reflecting unit on the light-reflecting cover according to the LED arrangement position and embedding at least a part of each light-emitting unit in the corresponding light-reflecting unit, thereby minimizing the thickness of the device while ensuring efficient utilization of the light path.

[0044] In specific implementation, the light-reflecting groove corresponding to the LED position on the PCB can be prefabricated in the light-reflecting cover mold through a precision injection molding process, and then the assembled LED SMD board is fixed on the heat-conducting member and the middle frame. The positioning tool can ensure that the center of the groove coincides with the optical center of the LED chip. After that, the light-reflecting cover is covered in the reserved clamping position of the middle frame and fixed by a buckle. Before the upper optical components such as the diffusing film and the light-enhancing film are stacked, the entire reflection cavity can be used as a high-efficiency light path recovery unit.

[0045] In combination with the above structural features, the application can effectively collect and reflect the side and back scattering light emitted by the light emitting unit to the light emitting direction, greatly improving the light flux utilization rate; since each light emitting unit is surrounded by an independent reflecting unit, the light spot superposition phenomenon is reduced, thereby significantly improving the imaging uniformity and contrast; at the same time, through accurate alignment and modular assembly, the consistency and reliability in batch production are ensured.

[0046] In the embodiment, the reflecting unit is a rectangular frame with open ends, and the light emitted by the light emitting unit is reflected by the inner wall of the rectangular frame and then emitted through the opening towards the side of the diffusion plate.

[0047] The rectangular frame with open ends refers to a cylindrical cavity with a rectangular cross-section shape opened for each light emitting unit on the reflecting cover, and the end faces of the two length directions are both transparent; the inner wall of the rectangular frame is a mirror surface for receiving and guiding the light emitted by the light emitting unit. In this way, the light emitting unit (such as a chip or an integrated lens) is partially or entirely located in the frame, and the light is reflected multiple times by the surrounding inner wall after being emitted, and finally emitted through the opening facing the diffusion plate, forming directional output.

[0048] In combination with the above structure, the application can effectively collect and reflect the side and back scattering light emitted by the light emitting unit to the light emitting direction, greatly improving the light flux utilization rate; at the same time, the frame structure avoids the light spot overflow and light superposition phenomenon, and improves the uniformity and contrast of the emitted light; in addition, the multi-end opening design simplifies the light path arrangement, making the assembly more efficient and easy to mass produce.

[0049] The embodiment further provides a light enhancement assembly above the diffusion plate.

[0050] The light enhancement assembly refers to a collection of optical films or optical sheets arranged to improve the brightness of the emitted light, such as a double polarization brightness enhancement film (DBEF), a reflective polarization brightness enhancement film, or a micro-prism light enhancement sheet, which can be stacked in sequence according to the light emitting direction above the diffusion plate. This technical solution increases one or more light enhancement film layers above the diffusion plate, so that the diffuse light passing through the diffusion plate is selectively reflected and collimated again, thereby significantly improving the light flux.

[0051] In the specific implementation process, the diffusion plate and the light dispersion film can be assembled and the position can be calibrated first, then the surface on the side of the diffusion plate facing away from the optical assembly is cleaned, and the first light enhancement film and the second light enhancement film and other components are sequentially attached, so that the optical axis or polarization axis of each light enhancement film is aligned with the direction of the microstructure of the diffusion plate. Bubble-proof attachment technology or vacuum suction tooling can be used during attachment to ensure that the film is flat and wrinkle-free, and micro-porous foam adhesive or ring-shaped positioning tape is used at the edge of the film to prevent displacement and optical leakage.

[0052] In combination with the above technical features, the light enhancement assembly is capable of directing and converging the light scattered by the light guide plate to the light emitting direction, improving the overall brightness by more than 20%, maintaining the same picture brightness under the condition of reducing the LED light emitting power, and saving energy consumption.

[0053] In the embodiment, the light enhancement assembly comprises a first light enhancement film, a second light enhancement film and a reflective polarized light enhancement film which are sequentially stacked along the light emitting direction.

[0054] Through the above-mentioned stacked light enhancement assembly, the polarized light and backscattered light which are scattered in the diffusion plate and not utilized can be recycled and collimated, and the overall brightness can be significantly improved. Due to the multi-stage polarization selection and reflection mechanism, the lateral and backscattered stray light can be effectively suppressed, and the image contrast and uniformity can be significantly improved. Meanwhile, the picture brightness can be maintained or improved under the condition of reducing the LED driving current, saving energy consumption and reducing the heat dissipation burden.

[0055] The first light enhancement film, the second light enhancement film and the reflective polarized light enhancement film are arranged in parallel. Through the parallel arrangement of the three light enhancement films, the polarized light and the lateral and backscattered light which are scattered in the diffusion plate and not utilized can be recycled and collimated multiple times. The parallel alignment of the polarization and the optical axis design can effectively suppress the interlayer light leakage, achieve higher picture contrast and uniformity. Meanwhile, the three-layer parallel structure can maintain the same brightness under the condition of reducing the driving power, save energy consumption and reduce the system heat dissipation pressure.

[0056] It also comprises a surface protection film which covers the surface of the side of the light enhancement assembly away from the light source assembly.

[0057] The surface protection film refers to a transparent film attached to the outermost layer to prevent damage to the upper optical film structure, which can be attached by single-sided or double-sided adhesive. The protection film covers the surface of the side of the light enhancement assembly (including the first light enhancement film, the second light enhancement film and the reflective polarized light enhancement film) away from the light source assembly, which is located on the side closest to the observer or the external environment, and is used to isolate external mechanical impact and pollutants from entering the optical stack.

[0058] The technical solution stacks the protection film on the back of the light enhancement assembly, realizes the physical isolation of the polarized film, the micro-prism surface and the reflection layer, does not change the optical path and the polarization characteristics, and ensures the alignment of the film layer structure through the parallel attachment to the optical axis of the light enhancement assembly.

[0059] In combination with the structural features, the surface protection film can effectively prevent scratches, scratches and dust adhesion on the surface of the light enhancement assembly during daily use or maintenance, while having certain moisture-proof and ultraviolet-resistant functions, ensuring stable optical performance during long-term use; The modular design also facilitates later replacement or cleaning, reducing maintenance costs and prolonging the life of the entire machine.

[0060] As shown in the drawings, Figure 3 In this embodiment, the edge of the diffusion plate is provided with a lug, and the surface of the lug is provided with an anti-cutting glue.

[0061] The anti-cutting glue can generally be a flexible silicone or thermoplastic elastomer strip, which is attached to the outer side or upper surface of the lug to eliminate sharp edges and provide soft cushioning. This scheme combines positioning and safety protection functions by providing a lug on the edge of the diffusion plate and covering it with anti-cutting glue.

[0062] The control circuit of the heads-up display in this embodiment is as shown in the drawings, Figures 4 to 7 As shown in the drawings, Figure 4 is an interface circuit diagram, in which CN1 is a high-speed connector between the mainboard and the LED drive board, which functions to provide power supply, data signal transmission and feedback loop. Among them, VCC is the power supply for the logic circuit, and VLED is the power supply for the LED lamp bead. SIN / CLKIN inputs data, SOUT / CLKOUT transmits downward, realizing multi-chip series driving. FB returns the real-time state of the drive board to the main control for current adjustment and abnormal protection. Through this design, the HUD system can realize precise control of high-brightness LED backlight, and protect by the main control when the current or temperature is abnormal, ensuring stable virtual image display and longer service life. In Figure 5 NTC1~NTC5 are 10kΩ thermistors distributed at different positions of the LED board for temperature monitoring. They are connected with GND, and the resistance value changes with temperature, which is sampled by the main control to judge the heat dissipation state and realize temperature control protection.

[0063] As shown in the drawings, Figure 6As shown, the control circuit further comprises a signal buffering and protection circuit subcircuit, which comprises a dual Schmidt trigger buffer, an external clock signal CLKIN input end is connected with a 1A pin of the dual Schmidt trigger buffer, a GND pin of the dual Schmidt trigger buffer is connected with a ground GND, a 2A pin of the dual Schmidt trigger buffer is connected with an external data SIN signal input end, a 2Y output end of the dual Schmidt trigger buffer is connected with a signal SIN_I through a resistor R4, a 1Y output end of the dual Schmidt trigger buffer is connected with a signal CLK_I through a resistor R3, one end of a resistor R1 is connected with the CLKIN input end, and the other end is connected with the 1Y output end of the dual Schmidt trigger buffer, one end of a capacitor C1 and one end of a capacitor C4 are connected with a VCC power supply, and the other ends are connected with a GND, an external data signal SIN input end is connected with a 2A pin of a U20 chip, a 2Y output end of the U20 chip is connected with a signal SIN_I through a resistor R4, one end of a resistor R2 is connected with the SIN input end, and the other end is connected with a GND, one end of a capacitor C2 is connected with a SIN_I signal line, and the other end is connected with a GND, one end of a capacitor C3 is connected with the SIN_I signal line, and the other end is connected with a GND, one end of a diode D8 is connected with the SIN_I signal line, and the other end is connected with a GND, one end of a diode D is connected with the SIN_I signal line, and the other end is connected with a VCC.

[0064] In Figure 6 which, U20 is a Schmidt trigger buffer, which shapes and buffers input signals such as SIN and CLKIN to improve anti-interference performance. The foregoing signal buffering and protection circuit shapes external clock and data signals through a dual Schmidt trigger buffer, cooperates with a series resistor to achieve impedance matching and current limiting, sets a large-capacity and a small-capacity capacitor in parallel for decoupling at a power supply end, increases a filter capacitor on a data signal line, and clamps protection of diodes to a ground and to a power supply, thereby effectively suppressing high-frequency interference and surge impact, ensuring clear edges and stable amplitude of output signals, not only improving integrity and anti-interference performance of clock and data transmission, but also enhancing reliability and safety of the circuit in a complex electromagnetic environment of a vehicle.

[0065] As Figure 7 shown, the control circuit comprises an LED driving subcircuit, which comprises a driving chip, a VCC pin of the driving chip is connected with a mainboard VCC power supply output end, the mainboard VCC power supply output end is connected with a positive electrode end of a capacitor C11 and a positive electrode end of a capacitor C12, a negative electrode end of the capacitor C11 is connected with a ground GND, a negative electrode end of the capacitor C12 is connected with the ground GND, a serial clock output end is connected with a CLK_I pin of the driving chip, a serial data signal output end is connected with a SIN pin of the driving chip, an FB pin of the driving chip is connected with an input end of a feedback detection circuit, and an output end pin of the driving chip is connected with a cathode end of an external LED load.

[0066] Cascade transmission to multiple drive chips through serial input (SIN / CLK_IN). Each chip has 16 OUTx output channels, which can independently control the corresponding LED. The FB pin is used for current feedback regulation to ensure brightness consistency. The VCC and GND of the chip are surrounded by 0.1uF+2.2uF decoupling capacitors arranged closely to reduce power supply ripple.

[0067] Embodiment 2

[0068] At present, the backlight drive of the vehicle-mounted head-up display usually adopts fixed frequency constant current or fixed duty PWM mode. Such mode is prone to three problems in vehicle application: first, the current spectrum energy is concentrated, strong peaks appear at specific frequency points and harmonics, resulting in electromagnetic compatibility test exceeding the standard; second, when the low gray scale or frequency selection is improper, the driver can perceive flicker with naked eyes, and the vehicle-mounted camera is also prone to stripe interference; third, under long-term single frequency excitation, the inductance, capacitance and LED devices bear concentrated stress, which has the hidden danger of heating and whistling.

[0069] To this end, the embodiment also provides a vehicle-mounted head-up display control method for controlling the vehicle-mounted head-up display described in embodiment 1, the method comprising:

[0070] S1: obtaining a target virtual image brightness value after projection according to the average brightness and the bright area ratio of the image to be displayed;

[0071] Wherein the average brightness refers to the average value of the brightness of the whole frame of pixels; the bright area ratio refers to the proportion of pixels higher than a certain brightness threshold, for example, the navigation arrow, warning symbol and other images to be displayed have the characteristics of small area high brightness, i.e. low bright area ratio but high peak value. The target virtual image brightness value is the brightness target that the driver should perceive at the windshield projection plane. In specific implementation, the input frame can be statistically averaged and the bright area ratio is obtained.

[0072] S2: determining a corresponding target current value according to the target virtual image brightness;

[0073] The target current value is the average driving current required by the driving light emitting unit, which is used to form the required virtual image brightness after the optical system. The current-light-virtual image brightness correspondence relationship can be calibrated by experimental method to form a multi-point calibration curve or lookup table, and the target current can be directly obtained according to the target virtual image brightness in operation; if necessary, a temperature aging micro compensation coefficient is introduced to improve consistency.

[0074] S3: clipping the target current value to obtain a limited target current value according to the upper limit curve of night anti-dazzle in the vehicle and the lower limit curve of daytime visibility;

[0075] The night anti-glare upper limit curve defines the maximum allowed brightness for night safety and comfort, corresponding to the maximum current; the daytime visibility lower limit curve defines the minimum brightness that still needs to be guaranteed under strong ambient light, corresponding to the minimum current; the limited target current value is the result of clipping the target current by the upper and lower boundaries. The purpose is to not exceed the safe and readable boundaries of too bright and dazzling or too dark and unclear under any content and environmental strategy. In the specific implementation, the target current and the upper and lower limits corresponding to the two curves are interval clipped; hysteresis and retention time can also be added to avoid back and forth jitter; the parameters of the night anti-glare upper limit curve and the daytime visibility lower limit curve are preset through experimental tests, and can be selected according to time period, mode or strategy table during running. Through the clipping of the foregoing target current value, night glare complaints can be significantly reduced, daytime readability contrast can be improved, and a compliant and stable current baseline can be provided for subsequent superimposed disturbance spreading.

[0076] The light-emitting device in the vehicle-mounted head-up display usually adopts an LED light source module, and the light-emitting efficiency and stability of the LED light source module are significantly affected by temperature. In a high-temperature environment, the junction temperature of the LED rises, which causes the light-emitting efficiency to decrease, and if the current is maintained unchanged, the brightness will be insufficient, and meanwhile, the overheating of the device can shorten the service life and even cause failure. In a low-temperature environment, the efficiency of the LED increases, and if no control is performed, the brightness of the virtual image is likely to be too high and glare problems are likely to occur, which affects driving safety. Since the working environment of the vehicle-mounted HUD is complex, it can be exposed to the sun for a long time in a hot environment, or it can be started in a low-temperature environment in winter, and therefore it is difficult to balance the brightness consistency and device reliability by simply relying on a fixed current setting.

[0077] To this end, a plurality of temperature sensors can be arranged in the display, and the limited target current value is dynamically temperature-compensated and adjusted according to the light source component temperature information collected by the temperature sensors.

[0078] In the embodiment, the dynamic temperature compensation adjustment of the limited target current value according to the light source component temperature information collected by the temperature sensors comprises:

[0079] The temperature change rate is obtained according to the light source component temperature information;

[0080] The temperature change rate refers to the speed of temperature change with time, and the temperature can be read at a fixed sampling period, and the change rate can be calculated by using the temperatures of multiple points in adjacent or short windows;

[0081] When it is detected that the temperature change rate is greater than a preset rate threshold, a current increase compensation coefficient is obtained according to the temperature change rate, and the current update period is shortened; the preset rate threshold is used to distinguish between rapid temperature rise and normal fluctuation, and can be set according to experience. The current update period refers to the time interval for performing one current target update.

[0082] The rate is compared with a threshold value first, and after the temperature change rate is greater than a preset rate threshold value, a compensation coefficient is selected in a continuous mapping table calibrated through experiments according to the rate size, the higher the temperature change rate is, the greater the compensation coefficient is, and the greater the reduction of the current on the original basis is;

[0083] When the temperature change rate is detected to be less than the rate threshold value, the compensation coefficient is reduced according to the temperature change rate, and the current update period is extended, and a smooth transition section is introduced between adjacent two update periods; the lower the temperature change rate is, the smaller the compensation coefficient is, and the smaller the reduction of the current on the original basis is, so that the current is stable. In this embodiment, the target current is compensated and adjusted by real-time acquisition of temperature information, so that stable, comfortable and safe display effects are realized under different temperature conditions.

[0084] In this embodiment, the method further comprises:

[0085] The temperature interval is divided into a low temperature zone, a normal temperature zone and a high temperature zone, and a hysteresis interval is set at the interval boundary;

[0086] The temperature interval is a temperature section set according to the working characteristics of the light source and the safety boundary of the whole machine. Usually, the full temperature domain is divided into three sections by two boundaries: a low temperature zone (such as a cold machine stage), a normal temperature zone (normal operation for most of the time), and a high temperature zone (exposure or long time high load). In order to avoid jumping back and forth at the boundary, a hysteresis band is set outside each of the two boundaries in actual engineering, and a minimum holding time is configured. If there are multiple temperature sensors, the highest value priority or weighted average can be used to obtain the representative temperature.

[0087] When the temperature is in the low temperature zone, the output current is reduced according to the current temperature and the low temperature current upper limit; the low temperature current upper limit is the maximum allowed current set to suppress the high luminous efficiency at low temperature, to prevent over-brightness and glare in the cold machine stage. Specifically, the current upper limit at the corresponding temperature can be found according to the corresponding relationship between the temperature and the current upper limit calibrated through experiments; the target current obtained based on the content is compared with the upper limit, and if it exceeds, it is clipped according to the upper limit; the maximum change slope and the smooth transition trajectory are set for the clipped target current, and the minimum holding time is maintained, and the brightness limit is gradually released after the temperature rises and crosses the hysteresis band.

[0088] When the temperature is in the normal temperature zone, the output current is controlled according to the ideal output brightness; the ideal output brightness is the target brightness obtained according to the average brightness and the proportion of bright area of the image to be displayed, combined with the upper limit of night anti-glare and the lower limit of daytime visibility in the vehicle; it is mapped into the target current through photoelectric calibration. After image statistics are performed on the current frame, the ideal brightness is converted into the target current;

[0089] When the temperature is in the high temperature zone, the output current is gradually reduced according to the current temperature.

[0090] After entering the high temperature zone, first according to the current temperature to the corresponding de-rating level, according to the level table to the target current to apply a proportion or fixed step down; To prevent sharp changes, set the maximum change slope and minimum holding time for each down; If the temperature continues to rise and exceeds the higher threshold, then reduce one level; When reaching the emergency threshold, start the protection mode (such as quickly pulling down to a safe bottom current or short-time off), and then according to the reverse multi-level strategy step by step recovery when the temperature falls and leaves the hysteresis band.

[0091] S4: According to the disturbance configuration parameters, the instantaneous set current sequence is obtained by superimposing zero-mean disturbance on the limited target current value;

[0092] Wherein the disturbance configuration parameters at least include the dither frequency, amplitude upper limit, sequence type and time window length; The zero-mean disturbance refers to the total amount of positive and negative dithering in a short window canceling each other out; The instantaneous set current sequence is a small time sequence around the limited target current, which is used to reduce flicker without changing the average brightness. By superimposing zero-mean disturbance, the fixed frequency radiation peak can be reduced, the flicker or stripe perceived by the naked eye can be suppressed, and the device stress can be dispersed while maintaining the ideal brightness of the virtual image.

[0093] S5: According to the synchronous clock, the instantaneous set current sequence is converted into driving code and output according to the latching point.

[0094] The synchronous clock is the time reference for communication with the driver and updating; The driving code is the quantized code word corresponding to the set current or duty cycle; The latching point output refers to updating all channels or registers at the same timing edge, so that the instantaneous current trajectory obtained by the algorithm is reliably and synchronously delivered to the hardware for execution, avoiding tearing, phase error and occasional peaks. Specifically, the instantaneous sequence can be quantized and packaged according to the driving protocol, and updated at a uniform latching edge; In the start-stop phase, the black field can be flushed first and then the table can be stopped, and when recovering, the black field can be latched first and then the work can be entered according to the ramp table, so that the data link is stable, the whole screen is updated uniformly, and the brightness jump caused by sudden bright flashes and phase misalignment is avoided, providing a stable and reliable final output for vehicle use scenarios. Through the analysis of the average brightness and the proportion of bright areas of the image to be displayed, combined with the night anti-glare upper limit and the daytime visible lower limit curve, the adaptive mapping and clipping control of the target virtual image brightness to the target current are realized, ensuring that the virtual image is neither dazzling nor clear and visible in different environments. On this basis, by superimposing zero-mean disturbance on the limited target current value, the instantaneous set current sequence is generated, so that the driving frequency spectrum energy is expanded, effectively reducing the fixed frequency flicker and electromagnetic interference, while keeping the average value of the virtual image brightness stable. Finally, through the synchronous clock conversion output, the current modulation and image refresh are strictly consistent, so as to realize the accuracy, safety and comfort of brightness control without relying on additional hardware, significantly improving the display effect and use reliability of the vehicle head-up display.

[0095] In the embodiment, the S4 includes:

[0096] S401: Obtain image statistical features of the image to be displayed, the image statistical features including at least a bright surface proportion and an average brightness.

[0097] The image statistical features refer to representative indexes obtained by overall quantification of the whole frame of the image to be displayed. The bright surface proportion refers to a proportion of pixels in the image that are higher than a set brightness threshold value, and the average brightness is an average value of brightness of all pixels, used to measure an overall light and dark level of the image. This step can simplify complex two-dimensional image data into a few key features.

[0098] The average brightness can be obtained by a gray scale histogram or a fast integration operation, and the proportion of pixels with brightness higher than the threshold value can be obtained by threshold comparison. The image data required in this step can be collected in real time when the image frame buffer is output. This embodiment can obtain representative features without complex pixel-by-pixel processing, and can support real-time dynamic driving adjustment with a small amount of operation, and is universal for different picture types.

[0099] S402: Divide the display scene into a first display scene with relatively high brightness and concentrated distribution and a second display scene with relatively low brightness and uniform distribution according to the size and uniformity of the brightness when the image is displayed.

[0100] If the bright surface proportion is lower than a preset proportion value (a first preset proportion value), but the average brightness is higher than a preset brightness value (a first preset brightness value), the first scene is determined; if the bright surface proportion is higher than a preset proportion value (a second preset proportion value) and the average brightness is lower than a preset brightness value (a second preset brightness value), the second scene is determined; in addition, a threshold interval and a hysteresis can be set to avoid frequent switching. The preset values in this step can be calibrated by test data.

[0101] S403: The image statistical features determine the display scene to which the image to be displayed belongs.

[0102] When the combination of the bright surface proportion and the average brightness falls within a preset first scene interval, a first scene label is output; when it falls within a second scene interval, a second scene label is output.

[0103] S404: If the image to be displayed belongs to the first display scene, the disturbance frequency is increased and the disturbance amplitude is reduced according to the image statistical features.

[0104] The disturbance frequency refers to the change speed of the current jitter, and the disturbance amplitude refers to the size of single positive and negative offset. When it is determined that the first scene, the parameter set of 'high frequency and low amplitude' is loaded in the disturbance configuration module, for example, the frequency is doubled, and the amplitude is halved; and a more uniform distribution is adopted when the window sequence is generated, so as to avoid local flicker.

[0105] This step reduces the risk of glare for the highlight concentration scene: fast disturbance helps to expand the frequency spectrum and reduce the perceived flicker; small amplitude jitter ensures that the local bright spot is not further amplified, so that the virtual image is still smooth when the local highlight is high, avoids the driver being disturbed by the sudden flashing, and improves the night safety.

[0106] S405: If the image to be displayed belongs to the second display scene, the disturbance frequency is reduced and the disturbance amplitude is increased according to the image statistical characteristics.

[0107] In the second scene, the overall picture brightness is low and uniformly distributed. At this time, reducing the frequency and increasing the amplitude can make the jitter slower but more significant.

[0108] This step makes full use of the tolerance of the uniform low-brightness picture to moderately amplify the current disturbance amplitude, so that the picture is uniform, and the human eye is not easy to perceive such slow-amplitude disturbance.

[0109] After determining the second scene, the low-frequency high-amplitude disturbance configuration is loaded, for example, the frequency is reduced by half, and the amplitude is increased by 20-30%; and when the sequence is generated, larger fluctuations are allowed but the mean value is kept, so as to ensure that the brightness mean value is unchanged. This embodiment utilizes the visual redundancy of the static uniform scene to improve the system anti-interference performance.

[0110] In this embodiment, the S404: If the image to be displayed belongs to the first display scene, the disturbance frequency is increased and the disturbance amplitude is reduced according to the image statistical characteristics, comprising:

[0111] S4041: When the bright surface ratio is lower than the first preset ratio and the average brightness is higher than the first brightness value, a highlight concentration risk value is obtained;

[0112] The bright area ratio refers to the proportion of pixel points in the image with a brightness higher than a preset threshold. The first preset ratio is a threshold for judging whether the image is sparse in bright spots, which can be set according to experience, for example, it can be set to 20%. When the value is lower than this value, it is considered that the bright area distribution is sparse. The average brightness is the average value of the brightness of all pixels in the entire image, which is used to indicate the overall brightness. The first brightness value is a threshold of the average brightness, which is used to determine whether the overall picture is bright, which can be set according to experience. The high light concentration risk value is an index obtained by combining the bright area ratio and the average brightness, which is used to quantify whether there are local bright spots in the picture that can cause eye strain. In specific implementation, a histogram of the input frame is counted to calculate the bright area ratio and the average brightness; if the ratio is lower than the preset value and the average brightness is higher than the threshold, a high light concentration risk value is generated, which can be divided into grades or continuous.

[0113] S4042: According to the risk value, increase the disturbance frequency and shorten the disturbance period to below the human eye flicker sensitivity threshold; wherein the human eye flicker sensitivity threshold is the highest frequency at which the human eye can perceive brightness flicker.

[0114] Specifically, a graded mapping method can be used: when the risk value increases, a higher disturbance frequency interval is selected; frequency switching uses a slow start or step-up to prevent other disturbances caused by instantaneous jumps. The selected frequency needs to avoid the prohibited frequency band and resonance point of the system, and maintain an integer relationship with the clock reference to avoid beat frequency. To maintain stability, the minimum holding time and different hysteresis of uplink and downlink can be set for frequency change. In this way, without changing the average brightness, the disturbance energy can be far away from the human eye sensitivity band, improving the viewing experience and passability.

[0115] S4043: According to the risk value, reduce the disturbance amplitude synchronously, and maintain zero mean constraint;

[0116] The zero mean constraint means that within a time window, the sum of positive and negative disturbances is zero, ensuring that the average current does not change.

[0117] Map the risk value to the amplitude upper limit, the higher the risk, the smaller the upper limit; on this basis, superimpose safety constraints such as low gray drop amplitude and high temperature drop. After generating the sequence, zero mean calibration and front-back balance calibration must be performed to ensure that the window is offset by addition and subtraction, and the front and back distributions are balanced; the amplitude limiting can use hard clipping or soft limiting, and the soft limiting is smoother. After this processing, the spread spectrum can be maintained, and the local bright area can be avoided from being enlarged by disturbance, and the average brightness is strictly maintained, so as to balance comfort and stability.

[0118] S4044: Increase the distribution uniformity constraint when generating the disturbance sequence;

[0119] The uniform distribution constraint refers to limiting the distribution of the disturbance on the time axis to prevent concentration in a certain period of time. The uniform distribution constraint can be generated by superimposing multiple rules: using a sliding sub-window constraint, the positive and negative number and intensity difference in any fixed length interval should not exceed the threshold; set the upper limit of the same direction continuous number, if necessary, insert a zero amplitude or reverse small disturbance to break; perform mirror move on the side of obvious strong to make both sides symmetrical; during sequence generation, select a more uniformly distributed mode as the basis, and then perform zero mean and equalization calibration. Through the above-mentioned ways, the disturbance energy can be spread in time, the peak and stripe can be reduced, and the virtual image perception is smoother.

[0120] S4045: Correcting the disturbance amplitude lower limit according to the short-time fluctuation of the actual output current.

[0121] The short-time fluctuation of the feedback current can be evaluated in the window, such as the statistical range, the standard deviation, or the rapid change amount of several sampling points, and compared with the preset effect threshold: if the fluctuation is obviously lower than the threshold, it means that the disturbance is too weak, then the amplitude lower limit is raised in proportion; if the fluctuation is sufficient or the peak risk is increased, the lower limit is maintained or lowered. For the sake of stability, hysteresis and holding time are set to avoid frequent up and down jumps; together with the amplitude upper limit mentioned above, the upper and lower limits are formed, and finally the disturbance intensity that can not be perceived and can be truly spread is obtained through zero mean and equalization calibration.

[0122] In the embodiment, the S4: obtaining an instantaneous set current sequence by superimposing a zero mean disturbance on the limited target current value according to the disturbance configuration parameters comprises:

[0123] S41: generating an initial disturbance sequence with fixed length and including positive and negative values according to the limited target current value, the disturbance frequency, the amplitude limit, and the time window length;

[0124] The initial disturbance sequence refers to a series of small offset values generated according to the configuration parameters in a given window length, which are positive and negative alternately.

[0125] The initial disturbance sequence refers to a series of positive and negative current offset values generated around the target current in a preset time window. The existence of these disturbance values will not change the average brightness, but will make the current no longer fixed at a certain constant value. For example, in a 100-point window, a sequence such as [+1, -1, +2, -2…] can be obtained. The initial disturbance sequence can be generated by using a pseudo-random number generator, a low-dispersion sequence, a regular alternation, etc. The amplitude can be preliminarily determined according to the hardware current capacity and the human eye perception threshold, and is usually less than a few percentage points of the target current. The length of the generated sequence is determined by the time window length to ensure that it can cover a complete modulation period in the time domain. The specific generation process includes:

[0126] Set reference: take the limited target current as the reference level of the whole window, ensuring that the disturbance fluctuates around it.

[0127] Generate disturbance pattern: determine the interval between disturbance points according to the frequency parameter. For example, if the window length is 100 points and the frequency is set to half the window period, switch positive and negative at 50 points; switch more frequently when the frequency is higher. The polarity of the disturbance (positive or negative) can be alternated regularly or generated by a pseudo-random method.

[0128] Limit disturbance amplitude: assign an amplitude value to each disturbance, but not exceeding the set amplitude limit; it can be a fixed amplitude or randomly assigned within the limit range. Finally, a sequence with fixed length, alternating positive and negative, and controlled amplitude is formed.

[0129] S42: Obtain the overall deviation index of the initial disturbance sequence according to the total amount of positive and negative in the initial disturbance sequence;

[0130] The overall deviation index here refers to whether the sum of positive and negative values in a window cancels each other out. If the sum of positive values is greater than the sum of negative values, it means that the sequence as a whole is biased to the positive; otherwise, it is biased to the negative; if it is close to zero, it means that the initial sequence itself is relatively balanced. Specifically, a simple summation operation can be performed to add all disturbances in the sequence to obtain the total sum, and compare it with zero to obtain the direction and size of the overall deviation.

[0131] S43: Adjust the positive and negative and amplitude of the last few items of the initial disturbance sequence according to the overall deviation index to obtain a zero-mean sequence;

[0132] The zero-mean sequence refers to a disturbance sequence in which positive and negative cancel each other out completely and the overall average is zero. In this way, when superimposed on the target current, the average brightness will not change.

[0133] This step can eliminate the overall deviation by local adjustment and correct the initial sequence to a strictly zero-mean sequence. This can ensure that the average level of current output is stable and will not drift over time due to disturbance. This step adjusts the last few items of the sequence. If the overall deviation is positive, change the last few positive disturbances to smaller or negative disturbances; if the overall deviation is negative, change the last few positive disturbances to smaller or negative disturbances. In this way, the difference can be gradually smoothed out until the positive and negative cancel each other out completely.

[0134] S44: Obtain the front-back imbalance index according to the intensity difference between the front half and the back half of the zero-mean sequence;

[0135] The front-back imbalance index refers to whether the disturbance intensity of the first half and the second half in a window is equal. If the disturbance of the first half is larger and the disturbance of the second half is smaller, a trend of bright first and dark later will be formed, and vice versa. This step detects whether the disturbance is evenly distributed in time. Even if the average value is zero, if the positive and negative disturbances are mainly concentrated on one side of the window, a slow brightness drift will be visually generated. This step can first calculate the total intensity of the disturbance of the first half window, and then calculate the total intensity of the second half window, and the difference between the two is the imbalance index. If the difference exceeds the threshold, it needs to be corrected in the next step. This embodiment can timely find and quantify the imbalance in time distribution, and provide a basis for subsequent time equalization calibration, so as to avoid trend changes in the window.

[0136] S45: According to the front-back imbalance index, a part of the disturbance from the stronger side of the zero mean sequence is selected and mirrored to the corresponding position of the other side to obtain an instantaneous set current sequence.

[0137] The instantaneous set current sequence here is the time sequence finally sent to the driving circuit, which is obtained by adding the limited target current and the disturbance value. In this way, the current at each time point has a slight change, but the average value of the whole window remains unchanged.

[0138] This step truly lands the calibrated disturbance sequence to the current output to form the final executable control instruction. This step can take the limited target current as the reference current, and then add each disturbance value in the time equalization sequence to obtain the instantaneous current value. Subsequently, these values will be converted into driving codes and uniformly output at the latch point. In this way, the anti-flicker effect is retained, and the overall brightness is ensured to be unchanged and the time distribution is balanced, thereby improving the human eye observation.

[0139] The method further comprises:

[0140] S61: Obtain a peak value of the feedback current in a preset time window;

[0141] The feedback current is a current sampling value actually output by the driving circuit. The preset time window is a fixed length time interval, for example, 1 ms or a complete driving refresh period, for counting the current fluctuation. The peak value is the maximum current value in the window. However, the transient overshoot in a short time which may affect the human eye or the device is captured. These overshoots may cause a virtual image jitter feeling or increase the device stress. The system continuously samples the output current during the window, and records the maximum value internally, and outputs the maximum value as the peak value index when the window ends.

[0142] S62: According to the degree that the peak value exceeds the first threshold, the peak value is divided into a plurality of grades from low to high;

[0143] S63: Determine the grade to which the peak value in the preset time window belongs.

[0144] The first threshold is a safe boundary value of the peak value size, exceeding which may cause false image flicker or driving stress. In order to control more finely, this step divides the over-procedure degree into levels. For example: the peak value within 110% of the threshold is level one, 110%-130% is level two, and above 130% is level three. This step converts the peak value over-limit situation of different degrees into corresponding control intensity. The peak value can be compared with the threshold by table lookup or piecewise comparison to obtain the specific level number.

[0145] S64: Limit the amplitude of the subsequent single disturbance output in the current time window according to the level corresponding to the peak value.

[0146] The subsequent single disturbance output refers to those disturbance points that have not yet occurred in the current time window. The limiting processing is to set a hard upper limit to the amplitude of these disturbance points to ensure that they will not appear larger overshoot. For example, when the peak value reaches level two risk, the amplitude of the subsequent disturbance can be immediately compressed to 50% of the original. After detecting the peak value level, the controller immediately adjusts the subsequent disturbance generation module to reduce or forcibly limit the amplitude within a smaller range until the end of the window. The next window re-starts the evaluation. This embodiment can quickly suppress the peak, prevent the false image from producing a visible dithering feeling, and protect the light emitting device from the overshoot impact, improving the system reliability.

[0147] S65: Adjust the sequence distribution uniformity of the disturbance in the transient set current sequence according to the level corresponding to the peak value.

[0148] The sequence distribution uniformity of the disturbance refers to whether the positive and negative disturbances are uniformly distributed in time within a time window. For example: if the positive disturbance is mainly concentrated in the first half and the negative disturbance is concentrated in the second half, it will cause a trend of first bright and then dark. Adjusting according to the peak value level means that when the peak value risk is high, the sequence distribution needs to be further optimized to make the disturbance more dispersed and uniform, avoiding the concentration of energy in a local area.

[0149] This step can prevent the disturbance energy from being too concentrated in the case of peak value over-limit, forming a visible instantaneous brightness fluctuation or current impact. Through uniformization processing, the current fluctuation can be dispersed in time to weaken the transient peak value.

[0150] In specific implementation, firstly, the current peak level is detected. If it belongs to a low level, only slight adjustment is needed, for example, a few disturbances concentrated in the same section are reinserted into other positions. If it belongs to a high level, stronger equalization measures are taken, such as reordering or mirror allocation of the sequence, to ensure that positive and negative disturbances are more densely alternated. If necessary, a rule can also be introduced: within any fixed-length sub-interval, the difference in the number of positive and negative disturbances cannot exceed a preset value. After adjustment, even in a scene with a higher risk of peak, the instantaneous setting current sequence remains stable and will not cause brightness flicker or current overshoot due to too concentrated disturbances, thereby improving the comfort of the virtual image and the safety of the circuit.

[0151] S66: The level corresponding to the peak increases at least once in the adjacent two same-direction disturbances of the sequence.

[0152] The aforementioned adjacent two same-direction disturbances refer to two consecutive positive or two consecutive negative deviations in the sequence. When the peak risk is high, if these same-direction disturbances continue to accumulate, the current may be pushed to a higher peak. Increasing once the reverse disturbance is to insert a smaller amplitude opposite direction disturbance between the two same-direction disturbances to break and disperse the energy. This step uses the method of inserting a reverse disturbance to quickly clip the peak, avoid further expansion of the peak, and break the trend of same-direction superposition within the sequence. When the peak level is detected to exceed the middle level, the disturbance generation module will insert a smaller reverse disturbance in the same-direction continuous segment; if it belongs to a serious level, the inserted reverse disturbance can be more frequent or even doubled. For example, [+2, +1] is rewritten as [+2, -1, +1], so that the total sum is suppressed. This embodiment decomposes the continuous disturbance that can cause a large overshoot into an up-down-up pattern, so that the instantaneous current is flattened and the brightness change perceived by the human eye is more gentle.

[0153] In this embodiment, the method further comprises:

[0154] S71: Obtain the root mean square value of the feedback current within a preset time window;

[0155] The root mean square value is a comprehensive measure of the fluctuation intensity of the current within the window, which can better reflect the average energy level than the peak value.

[0156] The root mean square value is used to monitor the overall energy size of the current disturbance, so as to find out whether there is a long-term high fluctuation risk. In specific implementation, the actual output current is first sampled to obtain sampling data, and then the square of each sampling point is averaged within the window to obtain the root mean square value.

[0157] S72: According to the ratio of the root mean square value to the second threshold value, the root mean square value is divided into several levels from low to high;

[0158] The second threshold is a safety boundary set by the system for fluctuation energy. When the RMS value is more than 5% of the target current, it is considered to be too high. By ratio, the RMS value can be divided into several grades such as mild, moderate and severe, so as to convert the continuous RMS value into a graded label.

[0159] S73: Determine the grade to which the RMS value in the preset time window belongs.

[0160] For example, the RMS value can be compared with the threshold value by ratio operation, for example, RMS / threshold value = 1.1, which is judged as mild overrun; if it exceeds 1.3, it is judged as severe overrun.

[0161] S74: Adjust the limit amplitude of the single disturbance in the subsequent output in the preset time window according to the grade corresponding to the RMS;

[0162] The limit amplitude is the maximum allowed value of the offset amount of each disturbance. According to the aforementioned grade, the amplitude can be reduced step by step. For example, it is reduced by 10% in mild overrun, by 30% in moderate overrun, and by half in severe overrun. Thus, the overall energy is avoided to be too large, and the current energy is suppressed by reducing the amplitude of single disturbance. The amplitude boundary can be dynamically modified in the disturbance generation module, the upper limit of the originally allowed amplitude is reduced in proportion, and is immediately applied to the subsequent disturbance point.

[0163] The foregoing method can gradually suppress the RMS value of the actual output current in the next window period, the system is more stable as a whole, and the virtual image brightness change no longer appears excessively active.

[0164] S75: Adjust the density of the sequence according to the grade corresponding to the RMS;

[0165] The sequence density refers to the frequency of disturbance in the window. If the RMS value is too large, the overall energy is too high, and the disturbance density can be reduced to make the sequence sparse. For example, the original disturbance is once every 2 points, and it is adjusted to once every 4 points. This step further reduces the fluctuation energy from the frequency dimension and plays a dilution role.

[0166] Specifically, part of the disturbance points can be skipped when generating the disturbance sequence, and only part of the positions are retained, so that the number of effective disturbances is reduced. This step combines the reduction of amplitude and the reduction of density to adjust, so that the overall fluctuation energy is significantly suppressed.

[0167] S76: Set the holding time according to the density of the adjusted sequence and the limit amplitude.

[0168] The holding time refers to a period of time after the adjustment measure takes effect, so as to prevent instability caused by frequent switching of the system. The length of the holding time can be set according to the adjustment amplitude: the more drastic the amplitude and density adjustment, the longer the holding time. The slow adjustment characteristic of the root mean square control is used to avoid frequent triggering of adjustment due to instantaneous fluctuations. In this way, the system performs more smoothly and stably, and will not cause the disturbance amplitude and density to change constantly due to short-term jitter, thereby ensuring that the virtual image brightness is maintained stably and comfortably for a long time.

[0169] The energy budget closed-loop control in this embodiment is complementary to the previous peak closed loop, and the peak closed loop is used to quickly cut the peak, and the energy budget closed-loop control is used to slow down the overall energy. The combination of the two can realize the function of fast and accurate adjustment in the HUD current disturbance control.

[0170] In this embodiment, the method further comprises:

[0171] S81: According to the input virtual image frame sequence, the frame difference degree is calculated to obtain the virtual image change rate degree;

[0172] The virtual image frame sequence refers to the projection frame formed in each refresh period in the HUD, and the continuous frames form a frame sequence. The frame difference degree represents the content change between the two frames, such as brightness change, edge movement, texture update, etc. By calculating the difference between multiple frames, an index reflecting the virtual image change speed can be obtained. If the two frames are almost the same, the difference degree is low; if the brightness and content change rapidly, the difference degree is high. The virtual image change rate degree is calculated by comparing the pixel brightness value, edge feature or histogram difference frame by frame;

[0173] S82: According to the virtual image change rate index, the display scene type to which the virtual image belongs is judged, and the display scene type includes a dynamic scene and a static scene;

[0174] The display scene type refers to the classification of the overall state of the virtual image picture: if the frame difference degree is high, it is judged as a dynamic scene; if the difference degree is low, it is judged as a static scene such as constant digital display.

[0175] One or more difference degree thresholds can be set, when the index is lower than the low threshold, it is judged as static, when it is higher than the high threshold, it is judged as dynamic, and when it is in the threshold interval, it can be kept in hysteresis determination to avoid frequent switching.

[0176] This embodiment can adapt to the image characteristics, pay more attention to suppressing jitter when the picture changes fast, and pay more attention to reducing interference and stability when the picture is static.

[0177] S83: The type of the jitter sequence is determined according to the scene type to which the virtual image belongs;

[0178] The type of the dithering sequence refers to a generation manner of the dithering sequence, for example, a regular alternating type, a random type, a pseudo-random type, a spread spectrum type, and the like. Different types of sequences will bring different effects to the virtual image perception.

[0179] This step selects the most suitable dithering mode according to the scene dynamics: in a dynamic scene, a smooth transition type or a sequence with lower randomness is selected to avoid adding too much uncertainty to the existing rapid picture change; in a static scene, a sequence with stronger spread spectrum is selected to avoid flicker or interference concentration due to monotonous content. After the scene is judged, different dithering generation modules or different sequence tables can be called or switched. For example, a pseudo-random sequence is used in a static scene, and a regular alternating sequence is used in a dynamic scene. This embodiment can achieve optimal dithering in different picture states, taking into account the virtual image comfort and electromagnetic compatibility.

[0180] S84: determining a dithering frequency interval of the dithering sequence according to the scene type to which the virtual image belongs.

[0181] The dithering frequency interval is the working frequency band range of the dithering signal, for example, 1-3 kHz or 3-5 kHz. Different frequency intervals will affect human eye perception and interference distribution. This step further refines the scene adaptive adjustment to make the dithering not only different in type but also optimal in frequency distribution. Specifically, two intervals can be set: a lower frequency but stable interval is selected in a dynamic scene to avoid virtual image dithering; a higher frequency and dispersed interval is selected in a static scene to improve the anti-flicker and anti-interference ability. This step matches the dithering frequency with the scene state, so that the virtual image can maintain the best perception in dynamic and static scenes, and the overall robustness of the system is enhanced.

[0182] This embodiment identifies the dynamics of the virtual image through inter-frame difference detection, and then adaptively selects the type and frequency interval of the dithering sequence, achieving the adaptation of the dithering parameters to the display content.

[0183] In this embodiment, the S84: determining a dithering frequency interval of the dithering sequence according to the scene type to which the virtual image belongs includes:

[0184] When the scene type belongs to a dynamic scene, the dithering sequence is limited to a low-frequency stable interval;

[0185] The dynamic scene refers to a state with high inter-frame difference and rapid picture change. In a dynamic content, the human eye is already sensitive to picture change, and if a too high frequency dithering is added, it is easy to add a perceptible flicker or stripe. Therefore, the frequency is limited to a low-frequency stable interval (1.2-2.4 kHz), and the target frequency is directly selected through a table lookup or a rule mapping, the minimum holding time and the different hysteresis of uplink and downlink are set, the jump slope is controlled, and the phase continuity is maintained if necessary.

[0186] When the scene type is static, the dithering sequence is limited to the high-frequency diffusion range (3.0-5.0 kHz); static scene refers to a state where the frame difference is low and the picture is basically unchanged. In static content, it is easy to appear fixed-frequency energy aggregation and human eye flicker, and the spread spectrum capability needs to be improved. The target frequency is limited to the high-frequency diffusion range, and a small amplitude frequency walk is performed in the range; combined with the amplitude upper limit and the low gray drop strategy, it is ensured that the high-frequency disturbance does not excessively amplify the brightness fluctuation; at the same time, it avoids audible frequencies and known sensitive bands. It can effectively reduce the fixed-frequency peak and stripe risk and improve the electromagnetic compatibility margin; since the disturbance is in a higher frequency band, the human eye cannot detect it, and the static virtual image remains stable and clear.

[0187] In the frequency range, the disturbance frequency is selected in a random or pseudo-random manner; the random manner is to randomly select a frequency point in the range; the pseudo-random manner is to use a fixed seed sequence, so that the result is reproducible but appears to be random to the outside. A pseudo-random table, a low-difference sequence, or a pre-generated frequency hopping table can be used to extract from the allowed frequency point set in each time window;

[0188] When the display scene is in a transition state between dynamic and static, the overlapping section of the frequency range is selected; the transition state refers to the gray area where the frame difference is between the dynamic threshold and the static threshold; the overlapping section is the frequency band of the overlap or splicing transition of the low-frequency range and the high-frequency range. After detecting the transition state, only the values in the overlapping section are taken; the width of the overlapping section can be dynamically contracted or widened according to the content fluctuation, device temperature, and regulatory sensitive bands, and a hysteresis and holding time is set for entry and exit to avoid back and forth swinging.

[0189] According to the frame difference, the corresponding frequency value is assigned in the overlapping section.

[0190] The frame difference is an indicator that measures the change of two frames of content; assigning a frequency value in the overlapping section means selecting a more suitable specific frequency point from the low end or high end of the overlapping section according to the difference. The closer the difference is to the dynamic side, the closer the frequency is to the low end of the overlapping section; the closer the difference is to the static side, the closer the frequency is to the high end of the overlapping section. A lookup table mapping can be used and a maximum change slope can be set to gradually shift in small steps in a plurality of consecutive windows; if the difference repeatedly jumps back and forth for a short time, it is output stably with hysteresis and holding time, and the fine tuning near the current frequency point is preferentially maintained; if an external sensitive band prompt appears, it is bypassed nearby in the overlapping section. After using the foregoing method, the frequency smoothly follows the content changes, avoiding frequent switching and back and forth dithering, which can not only ensure the stability of the transition period, but also maintain the continuity and dispersion of the frequency spectrum.

[0191] The above merely describes specific implementation of the present application, and those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described system, module and unit can refer to the corresponding processes in the foregoing method embodiments, which will not be described herein again. It should be understood that the protection scope of the present application is not limited to this, and any person skilled in the art can easily think of various equivalent modifications or replacements within the technical range disclosed by the present application, and these modifications or replacements should be covered within the protection scope of the present application.

Claims

1. A head-up display for a vehicle, characterized by The utility model relates to a kind of LED lamp, including: Main body frame, including heat conduction piece, middle frame and glue shell, the middle frame is connected with the heat conduction piece, the glue shell is connected with the middle frame, the middle frame is located between the heat conduction piece and the glue shell; Light source assembly is arranged at the bottom of main body frame, and the light source assembly includes circuit board, and the circuit board is provided with light emitting unit, and the light emitting unit is located at the side of circuit board away from the bottom of heat conduction piece; Optical assembly is located above the light source assembly, and the optical assembly includes diffusion plate and light scattering film stacked along light emitting direction; Thermal conductive adhesive layer is arranged between the circuit board and the heat conduction piece, and the circuit board is provided with control circuit; The optical assembly further includes reflector, and the reflector is arranged at the side of diffusion plate towards the light source assembly, and fixing glue is arranged between the reflector and the circuit board; The reflector is provided with light reflecting unit corresponding to light emitting unit one by one, and at least part of the light emitting unit is located in the light reflecting unit corresponding thereto, and the light reflecting unit is rectangular frame with two open ends, and the light emitted by the light emitting unit is reflected by the inner wall of rectangular frame and then emitted through the opening towards the side of diffusion plate, and light enhancement assembly is further arranged above the diffusion plate, and the light enhancement assembly includes first light enhancement film, second light enhancement film and reflective polarized light enhancement film stacked in turn along light emitting direction; Surface protection film is further included, and the surface protection film covers the surface of light enhancement assembly away from the light source assembly, the edge of the diffusion plate is provided with lug, the lug surface is provided with anti-cutting glue, and the side of heat conduction piece towards the circuit board is provided with conductive foam.

2. The vehicle head-up display of claim 1, wherein, The control circuit includes LED drive subcircuit, and the LED drive subcircuit includes drive chip, VCC pin of drive chip is connected with VCC power output end, the VCC power output end is connected with positive electrode end of capacitor C11 and positive electrode end of capacitor C12, negative electrode end of capacitor C11 is connected with ground GND, negative electrode end of capacitor C12 is connected with ground GND, serial clock output end is connected with CLK_I pin of drive chip, serial data signal output end is connected with SIN pin of drive chip, FB pin of drive chip is connected with input end of feedback detection circuit, and output end pin of drive chip is connected with cathode end of external LED load.

3. The vehicle head-up display of claim 2, wherein, The control circuit further comprises a signal buffering and protection circuit sub-circuit, the signal buffering and protection circuit sub-circuit comprises a dual Schmidt trigger buffer, an external clock signal CLKIN input end is connected with a 1A pin of the dual Schmidt trigger buffer, a GND pin of the dual Schmidt trigger buffer is connected with a ground GND, a 2A pin of the dual Schmidt trigger buffer is connected with an external data SIN signal input end, a 2Y output end of the dual Schmidt trigger buffer is connected with a signal SIN_I through a resistor R4, a 1Y output end of the dual Schmidt trigger buffer is connected with a signal CLK_I through a resistor R3, one end of a resistor R1 is connected with the CLKIN input end, the other end is connected with the 1Y output end of the dual Schmidt trigger buffer, one end of a capacitor C1 and a capacitor C4 is connected with a VCC power supply, the other end is connected with a GND, an external data signal SIN input end is connected with a 2A pin of a U20 chip, a 2Y output end of the U20 chip is connected with a signal SIN_I through a resistor R4, the U20 chip is the dual Schmidt trigger buffer, one end of a resistor R2 is connected with the SIN input end, the other end is connected with a GND, one end of a capacitor C2 is connected with a SIN_I signal line, the other end is connected with a GND, one end of a capacitor C3 is connected with the SIN_I signal line, the other end is connected with a GND, one end of a diode D8 is connected with the SIN_I signal line, the other end is connected with a GND, one end of a diode D9 is connected with the SIN_I signal line, the other end is connected with a VCC.

4. A head-up display control method for a vehicle, characterized by The method for controlling the head-up display of any one of claims 1 to 3, the method comprising: obtaining a target virtual image brightness value after projection according to an average brightness and a brightness area proportion of an image to be displayed; determining a corresponding target current value according to the target virtual image brightness; clipping the target current value according to an upper limit curve of night-time anti-dazzle and a lower limit curve of daytime visibility to obtain a limited target current value; dynamically temperature-compensating and adjusting the limited target current value according to light source assembly temperature information collected by a temperature sensor.

5. The vehicle-mounted head-up display control method according to claim 4, characterized by, The dynamically temperature-compensating and adjusting the limited target current value according to the light source assembly temperature information collected by the temperature sensor comprises: obtaining a temperature change rate according to the light source assembly temperature information; when detecting that the temperature change rate is greater than a preset rate threshold, obtaining a current increase compensation coefficient according to the temperature change rate and shortening a current update period; when detecting that the temperature change rate is less than the rate threshold, obtaining a current decrease compensation coefficient according to the temperature change rate and lengthening the current update period.

6. The vehicle-mounted head-up display control method according to claim 5, characterized by, The method further comprises: dividing a temperature interval into a low-temperature zone, a normal-temperature zone and a high-temperature zone; when the temperature is in the low-temperature zone, reducing an output current according to a current temperature and a low-temperature current upper limit; when the temperature is in the normal-temperature zone, controlling the output current according to an ideal output brightness; when the temperature is in the high-temperature zone, gradually reducing the output current according to the current temperature.

7. The vehicle-mounted head-up display control method according to claim 4, characterized by, The method further comprises: according to a disturbance configuration parameter, superimposing a zero-mean disturbance on the limited target current value to obtain an instantaneous set current sequence; according to a synchronous clock, converting the instantaneous set current sequence into a driving code and outputting according to a latching point. The instantaneous setting current sequence obtained by superimposing zero-mean perturbation on the limited target current value according to the perturbation configuration parameter comprises: Obtaining image statistical features of the image to be displayed, the image statistical features at least including a bright surface proportion and an average brightness; According to the size and uniformity of the brightness of the image display, the display scene is divided into a first display scene with relatively high brightness and concentrated distribution and a second display scene with relatively low brightness and uniform distribution; According to the image statistical features of the image to be displayed, the display scene to which the image to be displayed belongs is judged; If the image to be displayed belongs to the first display scene, the perturbation frequency is increased and the perturbation amplitude is reduced according to the image statistical features; If the image to be displayed belongs to the second display scene, the perturbation frequency is reduced and the perturbation amplitude is increased according to the image statistical features.

8. The vehicle-mounted head-up display control method according to claim 7, characterized by, The method comprises: According to the input virtual image frame sequence, the inter-frame difference degree is counted to obtain the virtual image change rate degree; According to the virtual image change rate index, the display scene type to which the virtual image belongs is judged, the display scene type including a dynamic scene and a static scene; According to the scene type to which the virtual image belongs, the type of the dithering sequence is determined; According to the scene type to which the virtual image belongs, the dithering frequency interval of the dithering sequence is determined.

9. The vehicle-mounted head-up display control method according to claim 7, characterized by, The instantaneous setting current sequence obtained by superimposing zero-mean perturbation on the limited target current value according to the perturbation configuration parameter comprises: According to the limited target current value, the perturbation frequency, the amplitude limit and the time window length, an initial perturbation sequence with fixed length and including positive and negative values is generated; According to the positive and negative total amount of the initial perturbation sequence, the overall deviation index of the initial perturbation sequence is obtained; According to the overall deviation index, the positive and negative and amplitude of a number of items at the end of the initial perturbation sequence are adjusted to obtain a zero-mean sequence; According to the intensity difference between the front half window and the rear half window of the zero-mean sequence, a front-rear imbalance index is obtained; According to the front-rear imbalance index, a part of the perturbation from the stronger side of the zero-mean sequence is selected and mirrored to the corresponding position on the other side to obtain the instantaneous setting current sequence.

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