AR HUD – Carrying A Wider Vision
▉ Cutting Edge AR HUD TechnologyWith continuous advancements of various technologies in automotive electronics, breakthroughs have also been achieved in HUD (Head Up Display) technology, with an evolution from Windshield Reflection Type HUD to Combiner Type HUD to the latest AR HUD.
The emergence of AR HUD technology is expected to take the automotive HUD industry to greater heights. The core feature of HUD is to display information to the driver while driving. The display content of Windshield Reflection Type HUD is traditional and simple. Although the Combiner Type HUD is slightly improved, the display range is still very much limited. Compared with the previous two, AR HUD features a larger display field-of-view, longer display distance, more vibrant display colors, and greater resolution. However, the most important feature is that AR HUD realizes the integration of augmented reality (AR), elevating the core positioning of the HUD, which is displaying information to the driver, to a whole new dimension.
Before the advent of AR HUD, conventional HUD products may display information including driving speed, battery voltage, water tank temperature, engine speed, car fuel consumption, etc., which is essentially an extension of the existing onboard information such as dashboards and car navigation systems. With the introduction of augmented reality technology, HUD display information is now much more intuitive and also adds AR HUD-exclusive information, such as: lane turns, actual navigation paths, distance to front vehicle, etc.
The emergence of AR HUD has also advanced the level of human-machine interaction. The invention of HUD is to resolve safety problems caused by looking down at the dashboard while driving. Still, as vehicles are equipped with ever more automotive electronics, the amount of information on the dashboard has also exploded. However, with the limited display space on the HUD, it is difficult to satisfy the desired amount of projection information. Even if it is satisfied, the obscuration caused by the display of too many messages will cause additional doubts about driving safety. Augmented reality brought by AR HUD opens a new window of interaction between the vehicle and the outside world, extending the display of information and providing an unprecedented platform for human-machine interaction.
▉ The wide display advantage of AR HUDA key element that allows AR HUD devices to realize augmented reality is the wider field of view they possess over conventional HUDs. To achieve this, it is necessary to talk about the two technical indicators of HUD’s VID (Virtual Image Distance) and FOV (Field of Vision).
VID (Virtual Image Distance) indicates the distance between the human eye and the virtual image; FOV (Field of Vision) means the angle at which the virtual image can be viewed with the human eye.
According to research from Texas Instruments, in the illustration above, the red is the VID and FOV of the traditional HUD. It can be observed that compared to the AR HUD, not only is the virtual image distance of the conventional HUD closer, but the FOV is also much narrower.
This has two effects. First, the virtual image is too close to match the sight of the driver. When driving, the visual distance is usually more than 2.5 meters of the conventional HUDs. This means that when driving and reading the information on the HUD (with the virtual image distance of conventional HUD being 2.5 meters), the eyeball needs to continuously refocus between longer and shorter distances, casting additional doubts on the drive's safety. Prolonged driving times will also increase eye fatigue. Furthermore, with a narrow virtual image range, the amount of information that can be accommodated is limited, and drivers cannot interact with the surrounding scene for AR navigation.
Generally speaking, AR HUD hopes to achieve a VID distance of 10 meters and a FOV angle of 10 degrees, and ideally a VID distance of 20 meters and a FOV angle of 20 degrees.
▉ Technical issues of AR HUD - overlapping imagesBecause of light projecting and reflecting on windshields, HUD has the common problem of overlapping images. This problem reduces the user experience and easily induces eye fatigue and dizziness.
In a traditional Windshield Reflection Type HUD, this is resolved by attaching a black transparent film on the windshield. The Combiner Type HUD uses a curved combiner to solve the overlapping images. The disadvantage is that the virtual image range is also limited to the display screen.
AR HUD can resolve the problem of overlapping images through windshield and VID:
Let’s start by first exploring why the HUD message projected on the windshield will have overlapping images. As you can see on the left in the image below, when the virtual image of the HUD is projected on the windshield, because the windshield has a certain thickness and curvature, light reflections when entering the human eye will result in two overlapping images, causing problems such as blurring of the virtual image.
The solution is shown on the right side of the figure below. When the PVB film in the middle of the windshield is changed, the light can be effectively concentrated when reflected into the eyes, allowing the driver to see a clearer virtual image.
The windshield specially made for HUD is generally called wedge film glass. Although it can effectively solve the problem of overlapping images, it also incurs substantial costs.
When the VID distance is adequate because the virtual image's distance is far enough, the human eye can hardly experience image ghosting, so there is no need for wedge glass, which saves costs. However, longer VID distances will cause virtual image distortion and low resolution. More breakthrough applications on optical technologies are needed to solve this problem, which raises the technical thresholds and barriers.
▉ Technical issues of AR HUD - huge sizeIn order to achieve long-distance VID and wide-angle FOV, optical path design needed to be adjusted significantly. The overall design is as shown in the figure below. First, the light source with the display generates the image and projects it into the fold mirror for the first reflection. The second reflection is done in the rotating mirror, after which the light comes out from the glare trap, and the third reflection is done on the windshield and finally enters the driver’s eyes.
Because AR HUD needs to pass through layers of the light path and reflection design in order to achieve high-quality VID and FOV attributes, the size of AR HUD devices is also much larger than Windshield Reflection Type HUD and Combiner Type HUD.
Because of its large size, when AR HUD is installed in front of the dashboard, it will result in significant restrictions and be limited to a few car models. Medium and large-sized vehicles are easier to integrate than smaller ones. Otherwise, special designs and modifications are required for the installation area to have enough space. But if the installation area is too crowded, it will be a problem for heat dissipation.
Although most AR HUDs face technical hurdles in sizes due to their optical path design, the new generation of AR HUDs can achieve a lighter and thinner presence through improved optical path design.
(UniMax's Flat type AR HUD includes features such as small size, low power consumption, and no need to use wedge glass. )
Flat type AR HUD is a next-generation AR HUD that differs from the light path with multiple reflection design of the previous AR HUD products. Flat type AR HUD leverages cutting-edge MAVE technology so that the external light paths can penetrate and be reflected, such as with window blinds. Wide-format images can be projected without the need for a large panel. The size volume can be reduced by at least 30% compared with AR HUD, and it can be easily integrated into most vehicles. However, the new AR HUD technology has a high entry barrier, and few manufacturers possess this technology.
▉ AR HUD Cross-Domain IntegrationAs mentioned earlier, AR HUD has a longer virtual image distance and a wider virtual image range, which can accommodate more information and provide a new level of human-machine interaction. AR HUDs with this feature can interact with devices as small as personal electronics and as large as network connections with products from other partner manufacturers. Compared with other HUDs, AR HUD has the advantage of establishing its own distinct ecosystem.
When AR HUD is integrated with the onboard BSD system, when the vehicle is about to turn and BSD detects a vehicle nearby, AR HUD can simulate an incoming vehicle warning in the lane. When the AR HUD is connected to the internet, when the driver indicates intent to park, eat, travel and other needs, AR HUD can instantly suggest suitable locations, and at the same time paired with voice instructions.
With an expected wave of wide and innovative AR HUD application scenarios, it will also bring consumers a richer driving experience.
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