The state of the art in lighting is an electric bulb. But these bulbs cannot be modulated, so they are of no use for communication. White LEDs do exist and could serve both purposes.
A standard incandescent bulb achieves 20 lumens per watt (lm/W) while automotive xenon lamp technology provides 90 lm/W. The solid-state technology currently achieves up to 40 lm/W in laboratory quantities and about 20 lm/W in series production. New records are established every three months. The theoretical limit of 200 lm/W means that the solid-state source achieves greater efficiency than the best existing light source. More efficient lighting systems would mean an enhanced brightness on the road while reducing fossil fuel emissions through lower power consumption.
This project aims to develop a new manufacturing technology to produce a new generation of headlamps for vehicles, which is the base for a future car-to-car or of car-to-infrastructure communication system.
The point is to define the ability of an LED system to provide communication modes for other vehicles or traffic safety devices - measured by the new ability to communicate during different driving conditions.
This is achieved by:
- validating the chip-on-board LED array with a primary optic moulded over the LED array, measured by an automotive qualification schedule;
- researching the best methods for converting multiple blue chip array into white chip array, measured by meeting colour temperature and rendering requirements;
- defining the best colour temperature and rendering for automotive driving;
- creating the most efficient optical system while understanding system trade-offs, measured by optical simulations and photometric measurements;
- defining the best method to electrically drive an LED system and integrate electronics in a vehicle format with respect to the modulation of the LED-array for communication;
- developing over-moulding technology for chip-on-board modules to produce a complete lamp within one injection-moulding shot;
- creating a system integration for the ISLE project in an automotive environment, measured by cost studies and automotive qualification schedule.
In the first phase, the consortium concentrates on finding convertible concepts, which meet both the individual excellence of each partner and the overall project goal. The central elements are:
- the LED architecture with respect to the requirements of the beam pattern forming optical elements;
- finding a suitable possibility to perform communication without any losses in light;
- definition of the required components;
- efforts in making LED headlamps legal.
The work is organised, the interfaces defined, and the best suitable concepts are selected and implemented accordingly. Starting from the first results optimisation loops will begin.
The following results have been achieved:
- Samples of white LED have been manufactured performing with a correlated colour temperature below 4300 K. On the way to this, a suitable submount for the LED-chip had to be designed. It had to perform optimal thermal conductance and provide a minimum of light absorption. Since monochromatic LED-chip radiation had to be transformed into white light, a unique converter material was also to be composed. All single components had then be brought together, always considering methods suitable for mass production.
- The communication concept has been implemented and its feasibility was approved in the laboratory and at the complete system. The concept was based on a frequency shift keying technology (FSK). The clou of this concept ensures together with the electronically driving concept no light loss either with or without sending data.
- An electronic driver circuit on lower scale integration (SMD-technology) with all necessary functionality was developed. From the experience made during the project development, an integrated circuit (ASIC) performing all functionality of the electronic driver circuit has been developed for automotive application and has now been introduced to the market.
- The integrated optical concept was turned into a complete headlamp including driving (high) and passing (low) beam. Also an alternative modular optical concept was designed and its performance simulated. Following the experience made within this project, the modular optical concept would have advantages for large scale mass production.
- A novel concept of laminating high reflective coating on plastic material was developed. It was found, that this concept has advantages compared to a metallisation layers normally used to make reflectors in terms of higher absolute reflectance.
- A high dynamic heating and cooling system operating with pressurised water for controlling the temperature in injection moulding tools was developed, which takes advantage of a new ultrasonic based water flow measurement.
- The developed converter material used for transforming the monochromatic light of the LED-chip is an alternative to the YAG-material (Yttrium Aluminium Garnet is a synthetic crystalline material of the garnet group) used by other LED manufacturers and will be applied in other projects.
- Based the experience made during the project an ASIC (Application Specific Integrated Circuit) has been developed for automotive application and has now been introduced to the market providing all the functionality as required in the project.
- The developed technology by over-moulding highly reflecting foils will used in lighting industry for reflectors as alternative for metallisation.
- The industry applying injection moulding for sophisticated products, such as optical devices, now has a further alternative in the injection moulding process with a new machinery for thermal controlling the injection moulding tool.
The experience made during this project could support international standardisation for automotive frontlighting in respect of using white LEDs, which can now legally be used for headlamps