No abstract

Innovations in photonics technology have the potential to revolutionize both the inside and the outside of the automobile, making driving, simpler, safer, and more economical. Some of the most interesting applications areas are: lighting, communications, night vision, display, entertainment, and controls. However, the commercialization of these technologies will depend on a number of factors: cost, proven improvements in safety, economy of operation, availability of mass-produced components with high uniformity and reliability, regulations, and standards. The automotive industry recognizes the utility of a roadmap to focus all players, from basic device manufacturing and component integrators, to set manufacturers and ultimately automotive assemblers. In this paper we report on progress on an important component of this roadmap concerning adaptive front-lighting systems (AFS).

The use of LEDs in advanced optical systems such as LED projectors or automotive headlamps is usually limited by the optical extend of the light source. The optical extend (or étendue) is defined as the product of the optical area and the divergence angle of the emission. In our paper, we discuss the consequences of such limitations on the design and performance of optical systems. The system optimization involves the chip technology, package design and the primary optics, producing an optical extend that has to match with the optical extend of the imager component. It will be shown how these optical laws put constraints on the LED light source and the design of suitable light engines. The benefits of LED light sources for the above mentioned applications will also be demonstrated. IntroductionLatest developments in LED technology have boosted the LED performance in regions, where new applications become possible. The features of long lifetime, dimmability, instant on, low voltage, highly saturated colors and mercury free operation bring LEDs major advantages. Using LEDs in the industry fields of projection and automotive headlamps boosts the luminance parameter as an equivalent to the lumen output. The source luminance limits the maximum illuminance by the optical system. This limitation is defined by the optical extend or étendue of the light source. In projection systems, the limiting factors are the imager size and the available space for the optics. In headlamps, the number and aperture size of the optics provide the limitation. To achieve maximum efficiency of the optical system, the mechanical tolerance requirements for the light source are relatively tight. For use in high precision optical projectors and lighting systems, currently available LEDs have reached their limit, however. By means of different application examples, this article describes the requirements for such an LED light source, and how these requirements can be fulfilled with optimized chip and packaging technologies. Vehicle headlights and projection systems serve as representative applications for high precision optical systems.