Car2X Communication as a segment of autonomous driving
Communication between vehicles still takes place 'reactively', i.e. via headlights, horn or hand signals by the driver (m/f/d). For example, you give way to another road user, warn another or signal to a pedestrian that you are stopping to let them cross.
This will change in the future: such light signals for communication will be triggered 'proactively' by the vehicle computer or come as a signal from the cloud. Matrix headlights with 1.3 million pixels can project signals or even text and symbols onto the road. A light crosswalk projected from the main headlights signals to a pedestrian that they have been detected by the sensor system and the vehicle clears the way.
Such interaction also has the effect of building trust in self-driving vehicles(Fig. 1). The same applies to rear lights, which use different patterns or flashing frequencies to signal emergency braking, for example. Technically speaking, a matrix headlight as a front light source is a projector and the rear lights become a display.
Future light types
The following future types of light have been defined and some are already being implemented:
- 'Advanced Coming Home Light' illuminates the path to the front door after leaving the vehicle. The 'Leaving Home Light' illuminates the path to the vehicle when you approach it or open it using the key remote control.
- Glarefree High Beam' refers to glare-free high beam, in which vehicles in front or oncoming vehicles are masked by dimming the corresponding pixels. This prevents glare.
- Lane light' illuminates your own lane.
- Orientation light' refers to the additional light markings within the illuminated lane exactly in the width of your own vehicle, including mirrors. This is particularly useful for very narrow passages or roadworks on highways.
- 'Marking Light' illuminates e.g. pedestrians without glare or cyclists to increase the driver's attention.
Texas Instrument DLP chip
The well-known Texas Instrument DMD chip(Fig. 2) controls the matrix headlights. These chips have been used for years in digital prepress and also in the PCB industry for digital imagesetters without film. However, significantly higher requirements had to be achieved for the requirements of the automotive industry, particularly with regard to the permissible temperature range and vibration resistance.
Fig. 2: Technology from the video projector: the heart of the high-tech headlight is a small chip with around one million micromirrors
Behind the matrix headlights(Fig. 3) is a technology with the abbreviation DMD (Digital Micro-Mirror Device). At its heart is a small chip with around one million micromirrors, each of which has an edge length of just a few hundredths of a millimeter. With the help of electrostatic fields, the mirrors can be tilted up to 5000 times every second.
Fig. 3: Structure of a digital matrix LED headlamp based on the DMD chip
Their position determines what happens to the light generated by three high-performance LEDs. The majority of it reaches the road via a lens system; if certain areas are to be blanked out, the corresponding light is directed into an absorber that swallows it. Figure 3 also clearly shows how complex such headlight systems are. They include a separate Peltier cooling element, the control electronics for the DMD chip and a combined LED dipped beam and matrix LED module.
This technology is not entirely new, as Mercedes installed these matrix headlights in the 2018 Mercedes-Maybach models.
Rear lights with digital OLED technology
Organic light-emitting diodes (OLEDs) in the rear lights were first used in 2016. Digitalization now promises greater safety on the road and allows the tail light signature to be personalized for the first time. Audi has started series production with this technology and plans to produce around 100,000 vehicles this year and around 200,000 vehicles in 2021.
Advantages of OLED technology
Fig. 4: Organic Light Emitting Diodes (OLED) rear lights with individualized design on the new AUDI Q5OLED light sourcesare surface emitters - in contrast to point light sources such as LEDs made of semiconductor crystals. The advantages of OLEDs: the light is extremely homogeneous. It can be dimmed continuously and achieves a very high contrast. It can be divided into segments. These segments can be controlled individually and can develop different levels of brightness. The segment spacing is minimal. The lighting unit does not require reflectors, light guides or similar optics. This makes the OLED units very efficient, light and flat. This considerably increases design freedom.
An OLED light element is only one millimeter thin, whereas conventional LED solutions require much greater depths of 20 to 30 millimeters. The energy requirement of an OLED is once again significantly lower compared to an LED optic if it is to achieve similar homogeneity.
The larger number of individually controllable segments can now be activated as required and their brightness can be continuously adjusted. In the Q5, there are currently three tiles of six units each, i.e. 18 segments per luminaire. The high precision and great variability offer lighting designers many possibilities. This works with a single piece of hardware that enables three desired signatures in the rear lights. In 'dynamic' drive select mode, the lights also switch to a further signature. Animation effects such as coming home/leaving home lighting scenarios can also be implemented.
Difference to the familiar OLED technology
A pure medium for signal functions now also becomes a display medium for different content.
Digital OLED lights also improve road safety through proximity detection. If another road user approaches a stationary vehicle from behind at a distance of less than two meters, all OLED segments are activated.
In future, significantly more segments per combination rearlight are conceivable. This will allow even more customizable light signatures.
Fig. 5: Status overview of the various display technologies
The view ahead
The aforementioned matrix headlamp technology is very expensive and is currently only suitable for expensive luxury class vehicles. For this reason, further development is moving in the direction of Digital Grid Light. The development of Micro LED is used here. 25,000 individually controllable MicroLEDs corresponding to 25,000 pixels. The properties such as high-resolution light, compact packaging and high efficiency are essentially comparable with the DMD chip solution.
In a nutshell:
- With the new developments in electromobility, new lighting concepts and designs are also being used. Along with Car2X communication, essential safety concepts for autonomous vehicles that will soon be ready for the market are being made ready for series production.
- The resolution of the headlights is achieved by a chip with 1.3 million highly reflective aluminum micromirrors called a micromirror array (DMD). A DMD is an electromechanical microsystem (MEMS) for efficient and reliable spatial light modulation at high speed.
- With matrix headlights constructed in this way, more than 5 basic light types can be used and communication with other road users can be facilitated.
- In the tail light area, multi-part Organic Light Emitting Diodes (OLED) tail lights with individualized design will be used in the future, which can also communicate.
An unusual year full of special challenges is drawing to a close.
The global dimension of the pandemic is unsettling. Many familiar things have suddenly disappeared, such as regular personal contact with customers, suppliers and fellow human beings or even evening conversations with industry colleagues at electronica and other trade fairs.
We are learning more humility again!
The pursuit of bigger, faster, higher has found an opponent and the belief that we are invulnerable is proving to be deceptive.
Let's look positively to the future and hope that we will soon get the pandemic and its health and economic consequences under control.
The good news from the vaccine developers is at least a light at the end of the tunnel.
Despite the unusual and difficult situation, I wish you an atmospheric and reflective Advent and Christmas season.
Stay healthy and stay tuned to PLUS in 2021
Yours
Hans-Joachim Friedrichkeit
