The Head-Up Display (HUD) system is now widely recognized, and most cars are equipped with this feature. Its core function is to project key driving information into the driver's field of vision, allowing for easy access without having to lower the head. The Augmented Reality Head-Up Display (AR-HUD), which evolved from HUD, is gradually gaining attention due to its more technologically advanced interactive forms and functional experiences. This article will explore the development history of automotive HUD from the perspective of technological evolution.
Tracing back to the technological origins of HUD, its initial application scenario was not in the automotive field, but rather in the cockpit of fighter jets in the aerospace industry. By projecting flight parameters onto the windshield, it helps pilots obtain key information while maintaining visual focus, thereby enhancing flight safety and operational efficiency. With technological iterations and the escalation of civilian demand, HUD technology has gradually shifted from the military to the civilian sector, and ultimately become an important component of automotive intelligent cockpits.
In fact, in the development history of automotive configurations, cases similar to "HUD transitioning from military to civilian use" are not uncommon. Besides HUD, what other automotive configurations have you learned about that originated from military technology?
The core subject of this article is the Head-Up Display (HUD). The display form of a conventional HUD resembles a green projection, with its core function being to project dynamic driving data. The technical principle is based on optical reflection - the light source refracts the information on the underlying Thin Film Transistor (TFT) screen through two spherical mirrors and projects it onto the car windshield. Based on this principle, even if the vehicle is not originally equipped with an HUD, it is possible to project and display mobile navigation information through a dedicated windshield, achieving a simple HUD function. The aftermarket HUD products currently available on e-commerce platforms (such as Taobao and JD.com) also rely on this principle to function.
From a technical classification perspective, conventional HUDs are mainly divided into two types: Windshield Head-Up Display (WHUD) and Combined Head-Up Display (CHUD). Among them, WHUD is more widely used, featuring the direct projection of information onto the original windshield of the vehicle, which is often pre-installed at the factory. On the other hand, CHUD requires an additional independent transparent panel, with information projected onto it, and was once more common in the automotive aftermarket. However, due to the overall low attention to HUDs in the market in previous years, CHUD products in the aftermarket have gradually faded from the mainstream.
However, technological development follows the principle of "if you don't advance, you'll fall behind." If WHUD remains stagnant in its current form for a long time without seeking breakthroughs, it will also face the risk of being eliminated by the market. According to research report data released by Orient Securities, the market size of the global automotive HUD industry was only 1.332 billion yuan in 2020, but it is expected to exceed 19 billion yuan by 2025, representing a nearly 17-fold increase in five years.
The core driving force behind the explosive growth of the HUD market is the emergence of Augmented Reality Head-Up Display (AR-HUD) technology. Augmented Reality (AR) technology, which has become widely known through products such as AR glasses, is centered around overlaying virtual data information on real-world spatial scenes to create an immersive interactive experience. This technical characteristic also provides direction for the upgrading of HUDs.
The core difference between AR-HUD and conventional HUD lies primarily in the dimension and practicality of the displayed content. Traditional HUDs display relatively limited content, mostly confined to basic driving data such as speed, RPM, and time. Even high-end HUDs that support navigation information display can only provide directional indicators such as left and right turns, as well as distance prompts. AR-HUD, on the other hand, achieves the "integration of real-world scenes and virtual data" - it presents dynamic distance information in real-time through virtual markers (for example, the remaining distance to the next ramp will jump in real-time as the vehicle moves, similar to the real-time distance update effect of the mini-map in the game "GTA5"). It can also project dynamic distance data, lane guide lines, and turning trajectory lines along the current driving lane, allowing drivers to completely eliminate their dependence on in-vehicle central control screen navigation during driving.
In addition, AR-HUD can be deeply integrated with Advanced Driver Assistance Systems (ADAS), directly displaying information such as following distance to the vehicle ahead, lane departure warning, lane crossing reminder, traffic light monitoring information, road speed limit sign recognition results, and even integrating driver state monitoring functions. Some brands' AR-HUDs have also expanded their ability to display life service information, presenting nearby dining, shopping, charging, refueling, parking, car wash, and other service points in real time. At the same time, in nighttime driving scenarios, the system can also identify and display pedestrians, enhancing the safety of nighttime driving.
Although from the perspective of functional appearance, AR-HUD seems to merely add an information display dimension to the traditional HUD, in reality, there are essential differences between the two in terms of core technical parameters and hardware configuration. These differences can be specifically explored from the following three aspects:
Firstly, Virtual Image Distance (VID). VID refers to the visual distance from the virtual image to the driver's eyes. Due to the focal length adjustment characteristic of the human eye, if VID is too short, the virtual information displayed by AR-HUD will appear blurred due to a mismatch in focal length when the driver observes road conditions at a distance. The VID of traditional HUD is usually only around 2.5 meters, while the VID of AR-HUD generally reaches over 10 meters; if cross-lane information display is required, the projection distance needs to be further increased to 20 meters.
Secondly, Field of View (FOV). The FOV is centered around the driver's eyes and is divided into horizontal and vertical FOVs, which directly determine the range of virtual information that the driver can observe. The FOV of traditional HUDs is relatively small, typically only 5 degrees; whereas the horizontal FOV of AR-HUDs needs to be above 10 degrees. For example, the horizontal FOV of the Ideal ONE's AR-HUD can reach up to 20 degrees, and the horizontal FOV of the AITO M5's AR-HUD can also reach 13 degrees.
Thirdly, projection area. The projection area of traditional HUD is usually between 15-20 inches, while the projection area of AR-HUD can be more than twice that of traditional HUD. Taking the Great Wall Mocha model as an example, the high-end version is equipped with an AR-HUD with a projection area of 70 inches. On the supply chain side, the 1.0 version of AR-HUD launched by Hansitong not only achieves a virtual image distance of 10 meters, but also has a display frame size of 74 inches.
In addition to breakthroughs in core parameters, the technological upgrading of AR-HUD is also reflected in the iteration of display panels. Early HUDs mostly used TFT displays, while some high-end models introduced digital light processing (DLP) displays; however, due to the dependence of DLP technology on Texas Instruments' digital micromirror device (DMD) chips and the involvement of multiple patent barriers, currently only a few brands such as Mercedes-Benz and Trumpchi have models equipped with this type of display. Currently, most technology companies have shifted their research and development focus to liquid crystal on silicon (LCOS) display solutions. Compared to DLP displays, LCOS displays perform better in terms of clarity and resolution, and the core chips can be localized, providing higher cost-effectiveness in cost control and supply chain stability.
It should be noted that the current AR-HUD is still in the early stages of technological development and has not yet fully matured. There are still multiple technical bottlenecks that need to be overcome. For example, in lane-level navigation functions, when the driver adjusts the seat position, changes in the viewing angle may cause the virtual navigation markers to shift in position. In terms of device size, due to the increased projection area, the device size of AR-HUD is more than double that of traditional HUD, with even the smallest size reaching around 9 liters (traditional HUD typically has a volume of 6-7 liters, and aftermarket HUD has an even smaller volume). This makes the aftermarket for AR-HUD almost infeasible. In terms of power consumption and heat dissipation, the larger the field of view and the higher the display clarity of AR-HUD, the higher the corresponding power consumption. Currently, its power consumption is generally around 15 watts, and some products even reach 20 watts (traditional HUD has a power consumption of about 12 watts), which will have a certain impact on the endurance of pure electric vehicles. In addition, AR-HUD has extremely high requirements for algorithms and data processing capabilities - it needs to integrate multi-dimensional data such as navigation signals, real-time positioning data, traffic information, vehicle speed, and driving direction. How to achieve efficient fusion of multi-source data and rapid processing of data obtained from sensors is the core issue in the research and development of AR-HUD chips and algorithms. The data processing capacity of traditional HUD is only about 10% of that of AR-HUD.
Despite facing numerous technical challenges, AR-HUD has begun to accelerate its penetration and popularization in mass-produced vehicle models. Currently, full LCD instrument panels have become standard equipment for an increasing number of vehicle models; and from a long-term development perspective, AR-HUD is expected to gradually replace traditional instrument panels and undertake more information display functions - some car companies have defined AR-HUD as the "third screen" in the car, and even plan to integrate the core functions of the car's system with AR-HUD.
In the future, the information display dimension of AR-HUD will be further enriched, potentially enabling drivers to obtain all necessary information without having to lower their heads to check the dashboard and central control screen, thereby alleviating drivers' dependence on mobile phones.
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