Search Results

Today, vehicle manufacturers are continually looking for lighting improvement and styling flexibility. Therefore, headlamp systems manufacturers have to conceive and develop new designs that improve the performance and reduce volume with no significant cost increase. To reach these objectives, one of the most interesting new technologies is the Compact Lighting System. The aim of this concept is to develop a headlamp system for the two functions, Low and High beams, with only one reflector and one light source. The Compact Lighting concept provides significant volume savings and improves overall lighting performance. Moreover, the Compact Lighting concept provides HID bulb optimization by using this high performance component for both functions, High and Low beams.

Since the advent of high power white LEDs some years ago, a lot of proposals for a full LED headlamp have been shown on demo cars and motor shows (1, 2). Meanwhile the performance is sufficient not only for show cars, but also for real serial application. Today, there are various concepts of LED headlamps under discussion for this purpose. Most of them consist of several single or multichip modules aligned in the headlamp to fulfill the lighting functions. We present a novel approach for a full LED headlamp, which combines compactness and styling flexibility with HID performance, as well as integrated thermal management and the possibility to add AFS (Adaptive Frontlighting System) functions. As light sources of the module, several multichip LEDs have been employed. Using a module approach, we achieve a very compact size, which offers unrivaled styling differentiation and additionally gives the advantage to scale the headlamp output according to the LED performance.

Considering their future characteristics, building a headlamp with white LEDs only might be soon possible. The cost of LEDs' lumens, their low luminance and their huge difference with traditional bulbs as light sources make new optical designs necessary. Projector modules appear to be the best basis for these new systems. Efficient versions, especially fitted to LEDs, which were recently designed and tested, are described.

Future AFS regulation will allow change of the low beam light distribution pattern. In order to propose AFS functions inside the headlamp, several approaches can be taken: combining multisource reflectors, or changing shields within a projector system. The first possibility requires many bulbs and dedicated reflectors that have a strong impact on cost and size. The second is a more compact solution with a projector system, using a rotating horizontal drum holding specific shields. Such a design allows easy integration into the elliptical module, but generates constraints regarding accuracy of the positioning of optical components. Also, glare can be generated during transitory phases in between function changes.

Halogen low beam market is divided between Complex Shape reflector and elliptic projector technologies. The former allows high flux but requires a large front surface - typically 120 × 140 mm. The latter, despite a reduced front surface, suffers from a large depth and from a flux significantly smaller, due to beam occlusion by the shield. The solution described in this paper takes advantages of both technologies. By combining a lens to a Complex Shape reflector, a high value of flux can be obtained: more than 40% higher than elliptic projector, with a depth 30% smaller. The overall performance is at the level of Best-in-Class Complex Shape reflector with a standard size of 100 × 120 mm. Range can even be improved by a slight increase of the reflector size.

When one considers designing full AFS headlamps today he may use either Xenon projector modules with electromechanical devices able to change the beam's shape or “standard” dynamic bending light projector systems with additional modules for motorway, adverse weather or town lighting. For the time being, regulation only allows using bulbs for this purpose, but LEDs will soon be a better choice: several cars with AFS headlamps using Xenon projectors and LED modules with thick plastic lenses have already been publicly shown. In this paper, we describe reflectors only solutions for LEDs providing the same benefits, an alternative styling, different integration options, and a significantly greater ease of manufacture. With full LEDs headlamps in view using only mirrors, these modules will allow AFS implementations with a fully coherent styling.

Recent developments in the automobile market have led to a demand for new vertically elongated headlamps. In current headlamps using parabola or complex shapes, the minimal horizontal aperture for the low beam is limited by performance requirements regarding flux and range. This limitation (5 inch or 120 mm) involves restrictions in vehicle styling. Thanks to the new Complex Shape called “SCV” (“Surfaces Complexes Verticalisées” in French) presented in this paper, it is now possible to reduce headlamp width to a significant extent, without having to use Ellipsoid technology. The average dimensions developed in this project are 80 mm wide × 150 mm high for the low beam (instead of 150 × 80 in current complex shape reflectors) and 80 mm wide × 120 mm high for the high beam. New specific complex shapes have been developed incorporating special solutions for range (ECE and US beam pattern) and other solutions giving increased width.