At the end of last year, the much-talked-about Huawei M9 was officially launched, an SUV equipped with many high-end technologies that completely subverted the public's perception of smart cars.
Among these technologies, one of them has attracted special attention from Lao Hu, which is known as the "first screen of intelligent driving".
Huawei's AR-HUD enables augmented navigation to project 3D arrows, stereo maps, and other information in front of the driver in real time, allowing the driver to obtain the most realistic road information.
Are today's smart cars so awesome? What the hell is going on with this AR-HUD?
From airplanes to cars
AR-HUD is a type of HUD, HUD (Head-Up Display), also known as head-up display, is a display technology that projects key driving information in front of the driver's line of sight.
This information includes vehicle speed, navigation instructions, etc., and the driver can quickly obtain information without looking down at the instrument and central control screen, and the driving safety is significantly improved.
HUD is not really a new technology, it was first used in aviation and military, and was first used in 1960 by the U.S. Navy A-5 carrier-based aircraft.
This technology can project the flight parameters, attitude, navigation and other information of the aircraft onto the perspective mirror directly in front of the pilot's field of vision.
Without looking down, pilots can understand the parameters of the aircraft and the external environment, reduce the frequency of looking down at the instruments, and improve flight safety.
In the '80s, General Motors applied HUD technology to automobiles after acquiring Hughes Aircraft, an aerospace and defense manufacturing company.
In 1988, General Motors introduced the Oldsmobile Cutlass Supreme Indy 500 Pace Car, the world's first car to feature a HUD.
The HUD can only display simple information such as the car's speed and steering, but it is a milestone because it is the first time it has been used in a car.
HUDs made their way into sports cars and luxury cars, and in 1997 color HUDs appeared, displaying more information.
In 2003, BMW became the first car company in Europe to use HUD technology, followed by Mercedes-Benz and Audi.
Although there were quite a few models using HUDs, there was little interest from the public, and then the HUDs began to cool down, after a gap of more than a decade.
In 2020, the AR-HUD of the Mercedes-Benz S-Class was released, which brought the HUD back to the attention of major manufacturers.
Now, Huawei has launched AR-HUD, which has pushed this technology to a new climax.
Classification of HUDs
The HUD displays a variety of information on the front windshield, including vehicle information and exterior information.
Vehicle information includes speed, rpm, mileage, steering, interior temperature, fuel consumption, etc., as well as additional information such as driving mode, sunroof open status, etc.
External information includes vehicle positioning, maps, navigation, pedestrian/obstacle detection, lane keeping assist, as well as road safety warnings, remote fault diagnosis, and more.
Some HUDs can also display audio and video media playback and control, as well as some simple smart office information.
According to the technology category, HUDs can be divided into C-HUD, W-HUD, and AR-HUD.
The C-HUD is a combination HUD in which a piece of clear plexiglas is placed above the instrument cluster to act as a projection board for information.
This type of HUD is less expensive, but due to the area of the projection panel, the imaging area is small, and it has now been phased out of the market.
The W-HUD is a windshield HUD, and as the name suggests, it is the windshield that projects information in front of the driver.
This type of HUD is the norm these days, but because the front windshield is usually free-form, it is prone to ghosting.
To eliminate ghosting, the shape of the PVB film of the front windshield laminate had to be changed and the thickness of the glass had to be adjusted, which required a certain cost.
AR-HUD is a combination of AR technology and HUD, which uses intelligent driving sensors to analytically model the road conditions ahead, so as to obtain various information about the road surface, and then accurately project the information to the corresponding position.
With the continuous advancement of technology, with the blessing of intelligent driving, AR-HUD will become the mainstream of HUD in the future.
HUD projection method
The HUD works by generating various numbers, images, and other information through the PGU, and then projecting this information onto the medium in front of the driver.
PGU is the image generation unit, which can generate images according to different projection methods, and is the core component of the HUD.
There are four main types of projection on the HUD:
The first is LCD projection, in which the transistors of an LCD panel drive liquid crystal molecules to rotate, change the polarization state of the light source, and then image it onto the glass through an RGB color filter.
LCD projection is the most mainstream HUD technology due to its low cost, but the image quality is poor, and the temperature in the car is slightly higher and it will not work.
The second is laser projection, which uses red, green and blue lasers as the light source, which is projected onto glass after the integration and scanning of optical components and processing chips.
The display effect of laser projection is better than that of LCD, but it also has the disadvantage of not working if the temperature is too high.
The third is DLP projection, which uses a digital micromirror device as an imaging device to project an image after digital processing.
DLP projection can achieve full-plane projection, and the resolution is far better than the first two, but the cost is higher, and most luxury brands choose DLP projection.
The fourth is LCOS projection, that is, silicon-based liquid crystal projection technology, the projection principle is similar to LCD projection, but the LCD material is replaced with a silicon wafer.
LCOS projection display is the best, but it is also the most costly, and it is not used much at present.
In addition, because the HUD requires the windshield in front of the driver to generate an image, the windshield of these vehicles is not the same as that of a normal car.
The image projected on the windshield is prone to ghosting, so it is necessary to minimize ghosting as much as possible to ensure the user experience and driving safety.
Most of the inside of the windshield has two layers of glass, inside and outside, with a layer of PVB film sandwiched in the middle, and the windshield of an ordinary car, these layers are parallel.
When using HUD glass, the PVB film layer should be wedge-shaped, thick at the top and thin at the bottom, which can effectively reduce ghosting.
It is also possible to add a reflective coating layer to the surface of the outer or inner glass to correct ghosting.
How to judge a HUD
What kind of HUD is a good one?
If the glass imaged by the HUD is compared to a screen, the virtual image distance is the distance between the driver and the screen, and the field of view is the viewing angle of the screen.
The farther away from the virtual image is the value, the less the driver's eye focus needs to be switched frequently, and the less likely it is to produce fatigue, so the larger the parameter, the better.
The larger the market angle, the driver's eyes do not need to move up and down, left and right, and visual fatigue can also be reduced, so the larger this parameter is also the better.
A qualified HUD must have a virtual image distance of more than 7.5 meters and a market angle of more than 10 degrees to have a good user experience.
Through these two parameters, together with the projection method, you can preliminarily judge the quality of a HUD imaging.
With the continuous improvement and popularization of intelligent driving and intelligent cockpit solutions, the application of HUD will become more and more extensive.
In the near future, HUDs will become a must-have for all cars.