In rear lamps, applications with red and yellow LEDs already are state of the art in lighting technology. White LEDs have already been used for signal functions like position or daytime running light in many projects.
With the development of the first Full-LED headlamp for Audi. For the first time, all light functions of a serial headlamp are being completely achieved in LED technology, these are low and high beam, daytime running light, turn indicator and position light.
LED technology offers new opportunities for the future concerning safety, technology, energy consumption and reduced carbon foot print.
LEDs especially stand out for the following characteristics:
- The light temperature of the LEDs achieve daylight quality
- Safety. Object recognition is easier under LED light of 6000K + and drivers tier less quickly
- An extremely high lifetime lasting more than a whole vehicle life
- A significantly lower energy consumption
- Solid State no filament so will withstand harsh vibration
LEDs are based on semiconductor technology. The light is emitted directly out of the semiconductor substrate when a forward voltage is applied. The colour depends on the band-gap energy of valence and conduction band for the materials forming the semiconductor. The amber colour is directly generated by the LED by Aluminium Indium Gallium Phosphide (AlInGaP) semiconductor material. Through the luminescence conversion process, white light is generated. A blue diode in combination with an applied converter material, the colour blue and yellow, the combination of which is perceived as white light.
To achieve the targeted light patterns with LED applications in headlamps, two conventional opportunities are available that are already implemented in filament and also in gas discharge lamps. Either the light of the LED is redirected through a reflector in order to achieve the light pattern on the road. Or, alternatively compact systems can be applied that project the light in the street using a lens.
Due to their small sizes, LEDs offer the opportunity to combine both light systems for the first time.
Reflector System Lens System
In contrast to Halogen or Xenon systems, LEDs emit "cold" light meaning that no infrared radiation is being produced. Due to the high efficiency, 20% of the input energy are transformed into visible light (for comparison a filament bulb only transforms 5%) - the rest of the energy generates heat within the semiconductor chip. Luminous flux, colour and forward voltage are dependant on the temperature. As soon as the allowed temperature is exceeded, the lifetime of the LED will be badly affected or in worst case will be destroyed.
To protect the hottest part, the chip, cooling elements with a controlled air transport system have been developed. The systematic direction of the warm air to the internal bezel and lens of the headlamp is being used for de-icing.
Micro filtration and convection ventilation of the headlamp is achieved by nav-comm's DOT Technology. Both dirt and moisture is cleared away keeping the optics clear and performing well.
The application of LED technology significantly contributes to the avoidance of CO2 emission and the reduction of fuel consumption.
This aspect especially gains importance with the implementation of daytime running light (DRL). DRL with LED needs 14W of energy, whereas the use of conventional vehicle lighting at day (low beam, rear lights, position lights) consumes 300W.
Whilst nav-comm have been producing LED warning lights since 1996. LED technology within the external vehicle lighting is still in its infancy. Vehicles found in OFF-Road situations with hazard awareness being critical will see fast implementation of LED lighting sources. Construction vehicles on building sites and demolition sites. LED Work lights will quickly be found on Tractors and construction machinery benefiting from increased productivity. Future fields of activity are to be found especially in the implementation of adaptive light systems and in the further optimisation of energy consumption.
