Arrayed Projector Technologies at Fraunhofer IOF

Increasing integration of automated functionalities and driver assistance systems in future cars requires continuous improvement of status indicators and user guidance. For in-car applications, consoles with displays are available but communication with persons outside the car remains a problem. A current popular approach is projection of symbols on the street in the vicinity of the car.

Using modern monochrome high power LEDs, improved collimators and advanced microlens arrays e.g. with high refractive index polymer lenslets, illuminance of 3000 lux at a distance of 45 cm from the car was achieved enabling operation in daylight conditions. A further improvement is projection of animated graphics by arranging arrayed projectors onto the same substrate in front of a multitude of individually switchable collimated LED light sources.

This requires hi-flux, efficient, miniaturized, and cost-saving projectors displaying a limited number of different images. Use of common LED-illuminated pico projectors with DLP microimagers fails because the projected flux is too small, the size too large, and because of the cost. Fraunhofer IOF's arrayed projector technology, which was commercially applied for the first time in the BMW 7 in 2015, enables the realization of strongly miniaturized luminaires for structured illumination near the car entrance area at night.

In a project with the company Brose Fahrzeugteile GmbH und Co. KG, such projectors were developed for automatically opening cars, as a welcome light for the driver, and a warning signal for cyclists. The assembled projector’s position in the car chassis ensures projection independent of the opening angle of the door. A second projector application guides the user for trunk opening by foot kick with a three channel projected graphics running light and a two channel animated graphic.

Authors: Peter Schreiber, Christoph Wächter, Stephanie Fischer, Chen Li, Ralf Rosenberger