Gone are the days when vehicle headlights came in the form of 7” diameter filament lamps mounted on stalks either side of the car bonnet. They were added almost as an afterthought to the vehicle design; nowadays headlights can be just about any shape to blend seamlessly with the vehicle’s front end. At the cutting edge of lighting tech is the new segmented main-beam unit from Fraunhofer IOF which minimizes light-scatter and is a design based on the continuous development of a multi-aperture projector.
200,000 micro-optic bundlesThe lamp unit consists of 200,000 micro-optic bundles containing 24 switchable LEDs and 8,000 microlenses to produce an optimal beam pattern. Segments of the light can be controlled as required by vehicle sensors to reduce the chance of dazzling oncoming road users including cyclists and pedestrians. The compactness of the design and shallow profile means it occupies significantly smaller volume in the vehicle compared to more conventional lighting solutions.
The new system also has a higher light output and better efficiency so that even when dipped, only 35% of the light is lost. This is a good figure for LED headlights and will go some way to boost the range when fitted to electric vehicles.
New headlightsThe headlamp consists of two modules, each with seven individually controllable LED clusters. Their light is directed by a total of four collimating lenses on two tandem lens arrays. These micro-optical elements take over the distribution of the light of the individual LEDs. Thousands of microlenses precisely guide the light into one lighting segment. This can be switched on or off by the individual control of the total of 24 LEDs in fractions of a second. The unit uses a relatively small number of LEDs so costs are kept down.
Rectangular polymer lenses of various dimensions have been used to achieve more precise light modelling. The smallest lens is just 0.045 mm x 0.180 mm. To produce the lenses Fraunhofer IOF developed its own production method using the ‘High Five’ grayscale lithography system. High Five is not only capable of producing extremely fine microstructures, it can also create the relatively large profile depth (up to 100 μm) needed to optimally direct the available LED luminance.
Fraunhofer IOF will be showcasing the design prototype at the upcoming LASER World of PHOTONICS trade fair held in Munich from June 24—27.