The Future for LED and OLED Automotive Lighting
Automotive lighting, both exterior and interior, has seen sweeping changes over the last five to ten years with the introduction of LED and OLED technologies. The flexibility of the tech has created many new design possibilities, enabling functional and aesthetic improvements in a number of different ways.
New matrix LED headlight configurations in tandem with sensing technologies have seen the introduction of systems which manage the direction of the beam to avoid blinding oncoming drivers. Meanwhile, the redesign of the exterior lighting setup has enabled engineers to create new styles and shapes to add distinctive brand character to their vehicles. As for the interior, the ability to introduce lighting into panels and fabrics within the car has led to a boom in ambient and functional lighting. This creates a brand-specific feel to vehicles, but can also assist with safety functions by directing the driver’s attention to certain areas.
With so many new applications for lighting, there has been a continued evolution in this sector of the automotive market. The use of LED lights is becoming commonplace in replacing halogen and xenon lights for headlamps and daytime running lights, but the OLED revolution that many were predicting in the last few years has failed to materialise. There are challenges in using both LED and OLED lighting for OEMs to contend with, and it remains to be seen which technology will come to the fore, or if indeed there is a future for both types of lighting in automotive manufacturing.
LED and OLED Benefits and Challenges
The key difference between the two technologies is that OLEDs are surface lights, whereas LEDs are point light sources. Although LEDs were an innovative concept just 10 years ago, they have quickly become mainstream in the automotive industry, particularly in Europe where daytime running lights are mandatory in many countries.
Manufacturers have successfully adopted LED technology for rear lights, brake lights, indicators and daytime running lights, as costs have fallen and advances have provided more flexibility. Headlamps however, have proven to be more difficult. The main stumbling blocks had been thermal management and LED assembly at the light-engine level, but recent advances have enabled the latest generation of LED-based headlamps to enter production. They offer many advantages over traditional tungsten-halogen and xenon lamps. High brightness white LEDs emit light at a similar colour temperature to that of daylight thus improving visibility. The illumination pattern can be controlled to avoid dazzling other drivers, and they are capable of lasting the lifetime of a vehicle, given proper thermal management. LED headlamps can be much smaller than conventional lamps, therefore providing greater freedom in design, such as selectable illumination patterns to suit driving conditions. They also make it possible to produce all-in-one units that incorporate indicators, daytime running lights and high/low beams in a single unit, making assembly and repair easier.
OLEDs are surface lights made up of multiple, organic semi-conductive layers which light up when excited by a current. This makes it possible to produce a variety of curving and irregular shapes, which can be used for various functions. Some car-makers have already demonstrated the use of OLEDs on exterior panels to warn other road users and pedestrians of the driver’s intentions, while others have demonstrated their use for ‘flowing’ lights to draw the driver’s attention to specific areas within the vehicle. They also provide vast possibilities for ambient in-car lighting to accentuate brand and personality. Effectively ‘flat’ light sources, OLEDs do not need any reflectors, light guides or other optics, nor do they cast shadows, which makes them extremely efficient and lightweight. As they can be designed in any shape and fitted to a flexible carrier, they provide even greater flexibility than LEDs. Cost however, remains a key issue.
One of the largest suppliers of automotive lighting systems, Osram, took part in the R2D2 project supported by the German Federal Ministry of Education and Research to produce an innovative lighting technology in collaboration with Hella and Audi.
As part of the project research was carried out into flexible OLEDs, with the result a rear light prototype presented at CES 2016. Project partners predict that this technology could be available to the sector within just a few years. The new flexible OLEDs from Osram were shaped into three dimensional modules by Hella, and integrated into rear lights in accordance with a design from Audi. The partners ensured that the light emitted from the module complies with the relevant ECE standards for brightness and light colour. The 3D unit requires no additional reflectors or optics to ensure the light can be seen from any viewing angle, and has the potential to give car manufacturers a completely new approach to lighting design. These flexible OLEDs are an innovation for tomorrow, but rigid OLED systems are already beginning to enter production.
Another key supplier of lighting systems, Magneti Marelli, has introduced a variety of new LED and OLED systems for exterior lights in the past few months.
At the 2016 CES in Las Vegas the company’s automotive lighting section demonstrated its Full-LED Matrix Beam module, an LED full beam with adaptive system for the guidance of the light beam through the LED’s selective activation. Also on show were its OLED rear lamps that contain red and amber OLEDs which give a homogeneous appearance regardless of perspective. Even when the tail light is off, the OLED elements appear to be a ‘silvery mirror’. Other new technologies include signalling lamps with pedestrian notification of turning, and an app for iPad which enables the customer to set up the colours and luminous intensity of the headlamps and rear lamps.
HELLA won the prestigious Red Dot Design Award in 2016 for its MULTIBEAM LED Headlamp in the Mercedes-Benz E-Class, which debuted at the Detroit Auto Show.
The three-layered pixel light module developed with Daimler consists of 84 controllable LED lights per headlamp. These can be individually controlled to adjust light distribution depending on traffic, weather and road conditions. The integrated adaptive High Beam Assistant Plus also ensures that high beam is used more frequently, offering greater safety and comfort.
The MULTIBEAM LED assists and supports the driver with high beam when other vehicles are located in the field illuminated by the headlamps. The adaptive high beam function selectively masks the area occupied by the other vehicle from the light distribution within fractions of a second. This works even if several vehicles are in the vicinity of the vehicle, having the effect of masking the other cars while illuminating the areas in-between them with high beam. In this way the driver is under the impression that they are driving with full beam, but other road users are not dazzled. A newly-developed adverse weather light reduces reflection on the oncoming lane when it is raining by specifically dimming individual LEDs in the low beam. Glare from illuminated road signs is also reduced by the system as it reduces the brightness of specific LEDs.
The precision LED module has 84 LED lights arranged in three lines, and the ability to control each individually results in a system that can create an extremely precise and highly variable light distribution. This is possible both in low beam and high beam without the use of actuators. Dynamic bend lighting is controlled purely by electronics, where the variable dimming of individual pixels allows the light focus to be shifted so the driver’s attention is directed towards the course of the bend.
Manufacturers have been quick to take up LED and OLED technology, with Audi and BMW both providing examples of what we may see in future years.
Audi has been experimenting with LED, OLED and Laser lights to enhance lighting to convey an aesthetic brand message or become a means of communication. An innovative laser light system uses a chip fitted with hundreds of thousands of individually controlled micro-mirrors, which divide the light output into tiny pixels. This means it is possible to adapt the lighting pattern to any driving situation and even to project graphical information onto the road. One innovation is a system which allows a rear laser light to form the shape of a warning triangle to warn other road users in foggy or rainy conditions. It has also developed OLED systems which would be fitted to the side of cars to convey information to other road users. An OLED rear light has already been developed which appears to flow forward quickly to augment the brake lights.
Clearly at this time LED is the best option for headlamps, while interior and functional applications are well suited to OLED technology. LED provides great flexibility in design and enables car-makers to introduce electronically controlled safety and driver assist functions. OLED technology is slowly being introduced in the shape of rear lighting, ambient lighting, and functional lighting for safety, but the costs mean that it is likely only to be used for premium models in the next few years. Meanwhile the advances in laser lighting provide another avenue of innovation, and laser technology offers further opportunities for functional lighting as well as brand representation.