The Display Formula

The automotive lighting community is facing a new product category: Exterior Displays: The non-existent product history for this category is leading to an individual understanding of what an exterior display should look like, what performance it should have and how we can use it. There are no best practice requirements such as those established for headlamps or signal functions. This paper shows the impact of parameters like luminous intensity, luminance, beam angle, pixel pitch, size, use-case definition and others to system and component requirements based on a single formula. The possible combinations of light emitting diodes (LEDs), driver integrated circuits (ICs), traditional optics, optical foils, switchable foils and decorative foils are infinite. Applying the formula on existing prototypes explains the wide range of resulting specifications for an exterior display which can differ by factor 100 or more targeting the same luminous intensity in HV0 to fulfill e.g. a legal function like daytime running light. Compared to traditional information displays, the new category of automotive exterior displays exhibits a higher degree of complexity. This paper helps to structure the complex development based on lighting parameters that are well known in the automotive lighting community.