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DLS offers exciting new possibilities for design and performance of headlamps. The powerful HID source technology is ideally suited to serve as light source for such a DLS, combining the benefits of both technologies to a completely new headlighting concept. The intention of the paper is to give an impression of the efficiency and performance of the system and to point out the prerequisites and parameters for the light source that influence the performance. Starting from the performance of present HID headlamps and based on sound considerations of losses of the various components of a DLS, the beam requirements are traced back to the necessary properties of a HID light source and bulb driver dedicated for DLS. From both calculations and measurements an estimation of the overall performance for the system is derived, with focus on incoupling efficiency.

Coatings on automotive bulbs are becoming increasingly more important. Environmentally friendly amber and red filter layers can be used on bulbs for signaling functions. Infrared reflective layers enhance the efficiency of halogen bulbs. Styling needs can be addressed with bluish bulbs matching the color impression of Xenon headlamps or silver / neutral colored amber filters for turn signal applications. Aside from aesthetic reasons, there is evidence that the modified spectral output of coated bulbs may provide visual benefits over standard tungsten halogen lamps for example during nighttime driving. Experience has shown that poorly engineered color-coated bulbs may fade in color or cause glare for other road participants by light scattering and color separation. Additionally insufficient road illumination for the driver himself is another negative side effect that can be observed with poorly engineered coatings.

This report investigates the use of single and multi-layer coatings on replaceable headlamp bulbs and how such coatings can affect the performance of bulbs in terms of light scattering, which can contribute to glare, and spectral separation in headlamps. Tests were developed to investigate the effects of absorptive and interference (multi-layer) coatings on bulbs, and on bulbs in headlamp systems. These tests provide validation for a proposed bulb color separation test, which establishes limits for spectral separation within the boundaries of SAE J578 white color requirements. The bulb color separation test provides a definitive selection criterion to identify bulbs that cause excessive light scatter (glare) and/or spectral separation in an optical system.

The purpose of night vision systems is to provide drivers during night and adverse weather with visual information beyond the range of their headlamps and beyond the glare of an oncoming vehicle's headlamp. Thus the driver has more time to react in case of unexpected and dangerous situations. Basically, two different concepts can be followed up. Passive night vision systems visualize the thermal radiation emitted by the objects themselves [1] while active night vision systems image near-infrared radiation which is reflected by the objects in the scene. Unlike passive systems, active night vision systems need powerful near-infrared light sources and cameras which are considered especially with respect to automotive requirements. Halogen light sources are the most promising candidates because about 25 percent of the total radiated power of a 60 W lamp lies in the near-infrared wavelength range from 800nm to 1100nm.

Mercury containing Xenon HID bulbs are currently on the exemption list of the European End of Life (EoL) Directive for Vehicles [1]. Their usage is generally accepted due to their superior performance and energy efficiency. These lamps also find a wider application in the US, but environmentally cautious states start to require labeling in order to ease dismounting and safe disposal at end of life. The concern for the environment is also the driving force behind the intention of Japanese carmakers to switch over to mercury free alternatives. Under these global boundary conditions the innovation of mercury free Xenon HID headlighting started mid of 2001. This paper gives an overview on the technical background of this breakthrough. From a physical point of view, key elements of environmental-friendly design of HID bulbs and its application in car headlighting will be described. We will also address the merits of a global approach to come up with this new technology.

In recent years environmental-friendly Mercury free Xenon HID lamp - D3 and D4 respectively with and without integrated igniter - were introduced in the automotive headlighting market. This market introduction was primarily driven by an increased concern for the environment by all stakeholders in car industry including the end-users. Furthermore, ordered by public authorities world wide, via new environmental legislation rules, Mercury free Xenon HID lamps will take over an important part of the Xenon HID market in due time. Within this perspective this paper will give an overview about technical backgrounds of Mercury free Xenon HID lamp performance. Next to light technical aspects the electrical interfaces between lamp and electronic driver are included. Furthermore, new developments in terms of satisfying carmakers requests on environmental aspects, electromagnetic compatibility and application flexibility will be discussed.

In 2004 environmental-friendly mercury free xenon HID lamps - D3 and D4 respectively with and without integrated igniter - were introduced in the automotive headlighting market. Driven by an increased concern for the environment from all stake holders in the car industry mercury free xenon HID has started his successful replacement of mercury containing xenon HID lamps used for automotive head lighting all over the world. Of course, the elimination of mercury was a key factor in promoting the environmental friendliness of xenon HID. Furthermore the amount of radioactive thorium compounds could be reduced to 2% of the content of the D1/D2 bulbs. Since then mercury free bulb designs without any thorium content have been studied assessing the electrical and optical compatibility with existing mercury free system designs.

Recent studies [2, 3, 4] have shown that with increase of the blue spectral content in the peripheral part of a headlamp beam pattern the visibility during night is also increased, especially at low ambient illumination. On the other hand several studies [2, 5, 8] have shown that the blue spectral content of a headlamp, although having no significant influence on disability glare, nevertheless increases discomfort glare for the opposing traffic. It follows that the effect of color can positively be used to both increase visibility and reduce discomfort glare if (for right-hand traffic) it provides a maximum amount of blue spectral content in the right peripheral region and a minimum amount of blue spectral content in the left peripheral region, while still lying within SAE white. Special light sources, to be used in conventional headlamps, have been developed to form such optimized beam patterns.