Among the various types of automotive lighting technologies in use today, the technology that is gaining popularity in the mainstream industry is that of light-emitting diodes (LEDs). Much like halogen lamps, LEDs are witnessing rapid adoption within the automotive industry, including India. As a technology, LEDs aren’t new but with greater adoption of the technology, costs have come down making it affordable. While LED solutions have been seen in vehicles for over three decades, it used to be an expensive alternative to halogen lamps affordable only for top-end car models.
It was in 2008 when Audi became the first carmaker to offer LEDs across all lighting functions on its R8 high performance sports car, including low beam, high beam, turn signal, daytime running lights and parking lights. The company has since remained the pioneer of sorts in introducing lighting related technologies in its cars.
Over the past few years, the technology has become mainstream, even penetrating into smaller, more mass market vehicles. LEDs are used for tail lamps, side indicators, headlamps, parking lights, reverse lights, fog lights, daytime running lights (DRL) and interior cabin lights as well. In addition, two-wheelers are also being fitted with LED lamps for the headlight cluster, rear lighting cluster as well as for DRLs. Even commercial vehicles and off-highway equipment have leveraged this automotive lighting technology for the high levels of efficiency it offers.
This just goes to show that LED is emerging as a natural choice for the automotive industry, when it comes to selection of lighting technology. In India, we have seen the LED technology move from the rear of the vehicles towards the front, from tail lamps to side indicators, and then to the headlamp.
One of the biggest benefits LEDs offer is in terms of design flexibility. Lighting clusters with LEDs can be designed to a very compact size due to the low area requirement of these lights. This feature helps designers bring out new design languages that are unique to the market with sleek, yet powerful lighting systems.
Another important facet of LED is that they are energy-efficient in nature, allowing it to be used extensively when the engine is running, without any deteriorating effect on the battery. In certain cases, low-powered LEDs can be run for certain periods of time even when the vehicle is not running, making them apt for emergency situations and other related needs. DRLs for passenger vehicles and two-wheelers as well as beacon lights for emergency vehicles, construction and other slow-moving equipment use LEDs due to this energy-efficient characteristic. It is also imperative to note that LED systems would be the choice for electric and hybrid electric vehicles due to this very characteristic.
LED systems for headlamps generally consist of multiple numbers of LEDs that are packaged together to form a single module. This element is beneficial in enabling a feature called adaptive lighting, where the headlamp consists of sensors and controllers connected to a vision system in the vehicle. When the system identifies an oncoming vehicle, it turns off the LEDs corresponding only to the position of the other vehicles, thus avoiding glaring of other road users. Once the vehicle has passed or has been overtaken, the LEDs are turned on automatically to provide a high-level of illumination. This feature also acts as a safety function in the vehicle.
While traditional LED systems itself are relatively new, in terms of being adopted in vehicle models below the premium segment, there are already advances in this technology to provide much more improved lighting. Some of these innovations are in the form of Organic LEDs (OLED) and Surface-LEDs. OLED is a display technology based on the use of an organic substance such as polymer, as the emissive electroluminescent layer in LEDs. An OLED display is created by sandwiching organic thin films between two conductors, with one of these conductors being transparent. When an electrical current is applied to this structure, it emits a bright light, and because OLED displays don't require backlighting, they can be thinner and weigh less than other display technologies. The number of automakers using OLEDs is small and limited to the higher end of the market. In addition, OLEDs are currently considered too dim to be used for brake lights, headlights and indicators.
A new innovation that Varroc Lighting Systems has brought to the market is the Surface-LED technology for exterior vehicle lighting systems. This technology brings together the appearance of OLEDs with the benefits of LED light sources in a cost-effective and reliable manner. Surface-LED can be substituted for OLEDs, since the latter is quite expensive and has issues related to reliability and design, the company noted. Surface-LED is a patented technology that uses thin layers of micro-optic filters and conventional LED light sources to achieve the homogeneous appearance generally associated with OLEDs. Each homogenously lit element is claimed to be only 3.5 mm thick with a luminous intensity that can be scaled from 2,000 to 13,000 cd/m2. Surface-LEDs are said to offer the flexibility to be designed and produced in 3D and curved shapes, and also in different colours, which is unlike OLEDs in the market at present.
The other form of increasing the utilisation of LEDs could be through the process of retrofitting, especially in a market like India. This process would involve replacing a traditional bulb with the LED technology so that the customer can avail the benefits of the LED lamp without changing the headlamp. There is a general feeling among suppliers that there is an increased potential for LED retrofits in the replacement market, for which they have developed products to bring into the market in future. While there are LED retrofits for applications like fog lamps, which are not particularly interesting for the mass market, forward lighting solutions will be introduced.
In all, we can see that the transition in the automotive industry concerning lighting would largely be from halogen lamps to LED units, without any other technology gaining similar levels of prominence or adoption. In the Indian context, the mandatory requirement of Automatic Headlamp On (AHO) on two-wheelers will also further boost LED adoption as the technology offers benefits of low power utilisation.
LED systems also play an important role in digital lighting solutions, where the vehicle lighting is directly connected to active safety systems. Under digital lighting, the entire lighting system, especially headlamps, are connected to the other systems of the vehicle such as navigation, vision systems and emergency safety functions that enable a situation where there is a level of autonomy achieved while driving. The lighting technology will display information to the driver on the road itself as well as provide other users with information about the intended movements of the vehicle. While this technology is still a sizeable distance away, it will eventually be used for autonomous driving and connected transportation.
The only negative effect experienced from LEDs is the amount of heat dispelled by these systems. However, semiconductor companies have developed controllers to achieve higher power, with better reliability and thermal dissipation of LEDs. These firms are providing LED system manufacturers with tools to create improved modules that are free from any negative characteristics, thereby enabling them to deliver an impressive performance. However, the end objective would be to develop low-cost LED headlamps, and define the right level of performance and specifications in order to meet the requirements of the mass market.
(With inputs from Magneti Marelli, Varroc Lighting Systems, Osram, Hella, Lumax, Mercedes-Benz, Texas Instruments)
TEXT: Naveen Arul