Of course, in order to meet our massive information acquisition needs, "no screen" does not really have no screen, but makes the screen transparent so that you can't feel its existence.
At present, automobile glass seems to be the best carrier, because display technologies such as HUD, AR+HUD and smart window can make a fuss about window glass.
Apple, for example, has developed a patent to embed the display screen in the front windshield.
Will Apple lead another wave of technological innovation?
As an automotive engineer, I am well aware of the gap between patents and products, so I want to ask, can the display screen and the front windshield really be perfectly combined and bring us a brand-new experience?
The first step to embed the monitor in the windshield is to make it transparent.
It is nothing new to make the display screen transparent, especially in recent years, with the breakthrough of transparent organic light-emitting diode screen technology, various transparent electronic products have also come into view, such as Xiaomi transparent TV.
▲ As early as ten years ago, Ericsson launched the world's first mobile phone with a transparent screen, and LG also released a transparent and operable keyboard screen.
However, at present, transparent liquid crystal display is more showy and cool, and the actual experience is not ideal.
Xiaomi TV is great, but it still looks gloomy, and the picture effect is not as good as ordinary LCD TV.
This is because the transparency and resolution of OLED display screen will restrict each other.
Xiaomi transparent TV has to sacrifice the resolution (down to 1080P) in order to obtain the light transmittance of about 40%, and there is no way to compete with the display screens with 4K and 8K resolutions.
▲ The difference between transparent organic light-emitting diode screen and ordinary organic light-emitting diode screen lies in the increase of transparent area. Transparent areas exist to let light penetrate and achieve the effect of screen transparency. However, the more transparent the area, the smaller the imaging area and the lower the screen pixels.
Although we can increase the light transmittance by further reducing the resolution, according to the requirements of laws and regulations, the light transmittance of automobile windshield is not allowed to be lower than 70%, and the resolution is not enough.
In addition, embedding transparent OLED panel in the windshield interlayer will inevitably lead to uneven inner surface of the glass and local optical unevenness, which will eventually lead to optical distortion and visual fatigue.
▲ Optical distortion is to evaluate the degree of deformation and distortion of light after passing through the front windshield. When testing, it is necessary to place a diaphragm with a diameter of 8mm in front of the projector, measure the diameter change of the circle projected on the screen, and then calculate the limit value of optical distortion.
We used to say "deceleration glass".
One of the reasons is that some cars have poor glass mass ratio, and the scenery they see has optical distortion, which makes the moving objects feel trance because of deformation, which is easy to make drivers feel visual fatigue.
A word here reminds you that if you want to keep the window film from wind, you must pay more attention to light transmittance and optical distortion.
For example, as shown in the figure below, the transmittance has obvious performance.
▲ Now the window film market is relatively mature, so don't worry too much. But adding a transparent OLED panel on the windshield is a brand-new knowledge, so don't equate the two.
Let's go back to the topic of "making sandwich cookies for display windshield"
On the bright side, OLED panel does not need backlight, and its structure can be made very light and thin, and it can be bent at will to match the shape of windshield, so it is a very suitable sandwich material.
However, embedding the display screen in the front windshield is not as simple as making a sandwich biscuit "2+ 1".
First of all, the front windshield itself is a "2+ 1" sandwich structure, and the PVB film firmly bonds the inner and outer layers of glass together in the middle.
So what? The OLED panel has no choice but to embed PVB. In fact, the structure of "2+ 1+ 1" is more accurate.
▲ Why doesn't the car windshield fall off after being damaged? Actually, it's because there is a sandwich structure in the middle.
At present, the thickness of PVB film in automobile interlayer is less than 1mm, so the thickness of OLED panel must be very thin to be integrated into the current windshield structure.
An important "high pressure" process in the production of laminated glass is directly related to the strength of laminated glass.
In the process of high pressure, the front windshield needs to be placed in the pressure cooker like a pressure cooker.
The temperature in the autoclave is about 140℃, and the pressure is as high as 13bar, which is equivalent to 13 atmospheric pressure.
This will pose a very severe test for the high temperature and high pressure resistance of OLED panels.
▲ Two pieces of glass are sandwiched together with PVB film in the middle. The moisture content of PVB has an effect on the properties of laminated glass. High pressure is to completely exhaust the gas in the interlayer with a large uniform pressure and a suitable temperature, so that the glass and PVB film are completely bonded firmly.
In a word, I think it is still very difficult to make an embedded "screenless" windshield.
Although at this year's CES show, BMW introduced the self-driving concept car BMW? Me? Interaction? Ease, with AR windshield.
But the concept of this product is so strong that my generation may have to wait until later in life to enjoy a completely immersive experience.
Don't be discouraged. Although the windshield display technology with embedded structure is difficult, the "screenless" mode can also be projected, such as HUD.
Although HUD is a picture formed by reflected light, it can give people the illusion that the front windshield itself is a display screen.
Although the cost is relatively high, it is generally only assembled on high-end models such as BBA, but in recent years, there are also many independent brands of walking models, which is at least the product we can contact.
▲ Through specular reflection imaging, the LCD dashboard can be projected in front of the windshield, and you need to bow your head to see the information such as speed and navigation in real time.
HUD is essentially equivalent to a projector. The internal light source of the projection device is the headlight of the projector, and the front windshield is the curtain, but the front windshield is transparent.
However, I would like to remind you that due to the same thickness of ordinary front windshield, the reflected image will be offset, which will reduce the use effect of HUD display and cannot be directly used as the projection interface of HUD equipment.
This is also the reason why there is always a vague ghost in the rear HUD.
▲ When the light emitted by the projection light source of the head-up display system passes through the two surfaces of laminated glass in contact with the air, it will be reflected, and the reflected images of the two surfaces will shift to form two interfering ghosts.
In order to solve the ghosting problem of the projection picture, the front windshield needs to meet the special optical structure.
Specifically, the front windshield needs to be changed from the original structure with uniform thickness to the structure with thin top and thick bottom. The original glass plate is formed by float process, so the thickness will be more uniform.
▲ Only by using wedge-shaped PVB film with thin top and thick bottom instead of ordinary PVB film with uniform thickness can we realize the special optical structure of interlayer and improve the ghost problem of HUD projection. This is one of the secrets of the windshield of high-end cars.
In order to control the ghost in an unrecognizable degree, the HUD windshield requires very high outline of the projection area, and the outline deviation is only allowed within+/-0.5 mm. ..
At the same time, high brightness and high contrast projection light sources need to cooperate with each other to get perfect results.
Of course, according to the usual practice, it is still necessary to say that there are shortcomings and room for improvement.
I am afraid that the most annoying thing is that the current HUD function is relatively simple. Generally, it can only display driving data information such as speed, rotational speed and navigation, and its intelligence is not perfect. It only outputs information, has no input, and cannot interact with devices.
Although Porsche cooperated with WayRay to demonstrate HUD navigation technology on 20 18, several years have passed and mass production has not been completed yet, which shows that the technical difficulty is still great.
▲HUD dynamic display
If you want to be a car hipster, you must know what an intelligent cockpit is.
Today, I hope I can help you cut through an object you touch every day and feel the hidden difficulties behind the intelligent cockpit.
Good products will come eventually, and the idea is right, but the road ahead is not easy.
For example, M-Byte's * * * enjoys a full screen and even achieves an exaggerated 48 inches. Later, as we all know, this company failed to mass-produce until it went bankrupt.
So, more importantly, implant a "transparent OLED panel to the front windshield"?
In a short time, HUD, the "projection version" of windshield display screen, can not only meet the requirements of windshield display, but also has more mature technology and lower cost, which may be popularized to the public earlier.
But as an automobile engineer, I still dream sometimes.
The extremely simplified design pursued by human beings may eventually overcome the display problem of embedded intelligent windshield. Who can say for sure?
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This article comes from car home, the author of the car manufacturer, and does not represent car home's position.