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Looking at the continuing discussion of the world climate change and the CO2-Emissions the individual traffic also still stands in the center of the public interest. The drastically rising of energy costs points out additionally the economic requirement for the development and transfer of resources-protective systems in the motor vehicle. Therefore there is no doubt, that the increase of the energy efficiency has today priority for the advancement of automobile technology. As vehicle power units can be evaluated only in the context with secondary consumers, the influence of these subsystems and components must be calculated too. Relating to the analysis of the vehicle lighting systems, it can be derived that their power consumption must be adapted at least in the same scale, as the primary energy consumption of the vehicle is reduced.

Since several years no other technology than LED (Light Emitting Diode) has more attraction for lighting innovations. After the introduction of this technology for CHMSL in the past decade today various LED lamps for several signal functions are already on the road. Meanwhile all exterior and interior lighting functions can be realized with semiconductor light. As LED technology is being introduced in more and more lighting functions, the basic conditions play a decisive role. The semiconductor light sources stand out, thanks to their service freedom, space-saving integration possibilities and low power consumption. But a main deciding factor in favor of this technology, which is still extremely cost-intensive in comparison with conventional systems, is the possibility of realizing headlamp and rear combination lamp shapes and appearances which have never been possible before.

The discussions of lighting experts in recent years formed the vision of an intelligent headlamp concept for the next decade: An intelligent headlamp system that will illuminate the road according to the driving conditions and, most importantly, that will react to oncoming and preceding traffic. The final stage of this scenario will be an “Active Headlamp” that will, similar to the current high beam, illuminate the complete road scene but exclude other road-users in front and on the opposite side of the road from glare, but not from signal information of the lamp. It is obvious that configurations having such a precise performance can be realized only with complex systems with highly sophisticated sensors, processors and actuators. With respect to the maturity of the available technology, the necessary development will take several years.

When defining the demand for an increased safety level of lighting systems for motor vehicles today, the main task will surely be found in the intelligent adaptation of the technical parameters and characteristics of lighting systems to different conditions of traffic, driving, use and environment. The implementation of advanced sensor technology for the detection of environmental factors combined with lighting systems with adaptive control will create unrivaled performance levels. This paper will attempt to provide some insight into the requirements, the development status in the fields of application and their functional possibilities.

When it comes to innovations for lighting in the front of motor vehicles, mostly the road illuminating systems are mentioned. However, in addition to the progress in the “real beam tasks” with swiveling headlamps, AFS etc, new potential for the “pure” signal functions has also arisen in recent years. Looking at the safety requirements for front lighting of the vehicle with the task “to be seen”, it becomes obvious that the mandatory signals Direction Indicator and Position Light should be complemented during the day via the Daytime Running Light (DRL). By displaying the position of a car (by day and night) and indicating a change of direction with the Turn Signal, complete and intuitive recognition of the vehicle-front will be realized.

In addition to the integration of new light sources, the main task for the creation of innovative competitive systems in the area of motor vehicle lighting will be found in the intelligent adaptation of the technical parameters and characteristics of lighting to different conditions of use and environment. In the frontlighting sector, cornering light that switches on automatically and dynamic bend lighting are already being used in series applications. Probably as soon as next year, variable beam patterns will allow adaptation of the frontlighting to different types of roads. In the case of combination rear lamps, a system has been developed that allows adaptation to environmental brightness and visibility conditions. An improved signalling effect is also guaranteed by the dynamic stop signal, which is already being used in series applications. As far as interior lighting is concerned, adaptive controls can contribute to more relaxed and safer driving by adapting brightness.

Today's requests from automotive manufacturers for innovative designs for signal and interior lamps are driven by three typical tasks: Saving space and depth in the lamp for easier and cost saving integration in the body construction. Lamp thickness should be reduced to a technically achievable minimum. A homogeneous illumination needs to be realized with a minimum number of emitters (particular with LED). Line design should be supported by reliable technologies, enabling stylists to develop contour-driven designs. All these demands can be supported by “Solid Light Guide Optics”. In this optical concept a solid light guide with the basic geometry of a tube receives the light from a light source (bulb or LED) directly, or via an additional flexible light guide. The rays are transmitted in the circular solid light guide by total internal reflection and will be also coupled out partly with the aid of prisms or structures on the rear side of the longitudinal axis of the guide.

Light Emitting Diodes (LED) in the field of automotive signal lighting have been well known for around a decade. The first step was the introduction of Central High Mounted Stop Lamps (CHMSL), containing 5 mm LED types with an emitter-flux of less than 1 lm. Improved designs offering more than 2 lm have made new CHMSL designs, side-markers, and the first rear combination lamp functions possible. The development of the next LED generation, supplying more than 10 lm, will extend LED technology into new fields of application. Concentrated in one LED package, this offers two new areas of application: Signal functions requiring a high amount of flux to reach the photometrical requirements. Designs working with indirect lighting in order to create new styling variations. This paper will attempt to show the wide field of possibilities that can be opened up with new LED types, in combination with innovative optical systems.

The most important changes in signal lamps took place in the '90s, with the introduction of new, alternative light sources. Light-emitting diodes and neon tube systems were able, for the first time, to concomitantly achieve freedom from maintenance and new design via their use in Center High Mounted Stop Lamps (CHMSL), side-marker lamps and rear panels. This paper presents a comparison of the technological and economic performance of contemporary signal lamp light sources, and attempts to provide a perspective of developments over the forthcoming years.

Of all the light sources for automotive applications, only the LED increased its efficiency by a factor of more than 100 within the last quarter of a century. The use of new chip materials and new LED packages raised the emitted flux in the latest “TS-AllnGaP” process to more than two lumens per LED. Offering an extremely high service life, low power consumption, little mounting depth and quick response time the first LED application for signal lights was the Central High Mounted Stop Lamp (CHMSL). In order to continue this success for other signal functions further technical problems have to be solved: Highly efficient secondary optics have to collect the light and to form it into an adequate beam pattern. - New methods of electrical connection are needed to enable LED's to follow the 3D-shape of the car.

HELLA has developed a new interior-lighting system under the name of “CELIS”, which stands for CEntral LIghting Systems. It is a modular concept, and makes use of decentralised light sources. These lighting modules enable interior lighting to be created with light-guides, and integrates important elements in addition to the usual functions of comfort and safety. A prototype vehicle has been adapted to demonstrate that it is thus possible to achieve an improvement in the light quality in the interior and to offer the features of convenience and safety.