Volume 9, Issue 6 - Automotive Lighting / Guest Editor: Cornelius Neumann

High-resolution headlamp concepts, such as the SSL|HD system from HELLA [1], induce completely new requirements for the evaluation of headlamp light distributions. The subjective perception of image quality is becoming increasingly important compared to the fulfilment of legal lighting values. High-performance projectors allow a good compromise between rapid but theoretical simulations and real but expensive prototypes. These projectors can display different static or dynamic simulations in a realistic way with regard to image quality and light values [2]. This article first introduces the high-performance projectors used for this purpose at HELLA. The projectors can be used to visualize the headlamp light distribution early in the development process, long before prototypes or overall systems are implemented in the vehicle. Following this, two exemplary research questions for static situations are presented, which were answered on the basis of investigations with the high-performance projectors. The requirements for dynamic simulations of real traffic situations, which are described by the interaction of the individual sensors installed in the vehicle (e.g. vehicle dynamics, level sensors, camera), are much more complex. In the paper, a development tool consisting of high-performance projectors and the HELLA simulation software ALiSiA is presented. The aim is a dynamic visualization of the entire system to optimize the development process.

With advances in automated and connected driving, secure communication is increasingly becoming a safety-critical function. Injection of manipulated radio messages into traffic can cause severe accidents in the foreseeable future, and can currently be achieved without having to manipulate on-board vehicle systems directly, for example by hijacking cellphones instead and using these as senders. Thereby, large-scale attacks on vehicles can be executed remotely, and target relatively vulnerable devices. To mitigate remaining vulnerabilities in current automotive security architectures, this paper proposes a secondary communication channel using vehicle head and taillights. In contrast to existing approaches, this method allows both to achieve a sufficient data rate and to extract the angular position of the sender, by means of an imaging process which only requires close-to-market, cost-efficient technology. Through this, injecting false messages by masquerading as a different sender is considerably more challenging: The receiver can verify a message’s source position with the supposed position of the sender, e.g. by using on-board sensors or communicated information. Thereby, reliably faking both the communicated messages and the position of the sender will require direct manipulation of on-board vehicle systems, raising the security level of the function accordingly, and precluding low-threshold, wide-range attacks.

Holograms have found their use as optical elements in a variety of applications. Yet using them with incoherent and divergent lightsources like LEDs proves difficult, as their characteristics need to be simulated by lasers during manufacturing to get a correct reconstruction of the desired light distribution. We present a new setup to allow for a high flexibility during the manufacturing process, which is able to produce volume holographic cell arrays (VCAs) that can be illuminated directly with uncollimated LEDs. Results are presented for the case of reflection holograms.

In everyday traffic, pedestrians rely on informal communication with other road users. In case of automated vehicles, this communication can be replaced by light signals, which need to be learned beforehand. Prior to an extensive introduction of automated vehicles, a learning phase for these light signals can be set up in manual driving with help of a driver intention prediction. Therefore, a three-staged algorithm consisting of a neural network, a random forest and a conditional stage, is implemented. Using this algorithm, a true-positive rate (TPR) of 94.0% for a 5.0% false-positive rate (FPR) can be achieved. To improve this process, a personalization procedure is implemented, using driver-specific behaviours, resulting in TPRs ranging from 91.5 to 96.6% for a FPR of 5.0%. Transfer learning of neural networks improves the prediction accuracy of almost all drivers. In order to introduce the implemented algorithm in today’s traffic, especially the FPR has to be improved considerably.

Recent rapid progress in automotive lighting technology led to the emergence of headlamps featuring a large variety of light distributions that are highly adapted to provide best possible road illumination in particular traffic situations. Visual assistance systems which highlight relevant objects or project symbols to communicate with other traffic participants, further improve road safety. Implementing all these functions within a single headlamp usually requires the use of several additional modules with high and low resolution. This multitude of modules impacts the installation space, styling and cost of automotive headlamps. This paper presents a high-resolution red-green-blue (RGB) laser headlamp module which provides a good illumination of the road and can also be used for external communication purposes. A specially developed laser scanning unit, based on a bi-axial resonant micro-electro-mechanical systems (MEMS) scanner and a high-power RGB laser, serves as the technical basis. Three module concepts are designed using light simulation, constructed as computer-aided design (CAD) models and integrated into a serial headlamp package. The concepts are based on design, simulation and measurement data of the scanning unit.

In this work, an investigation of the temporal coherence properties of radiation which is emitted by laser modules integrated in headlamps is presented. The motivation for these measurements was difficulties concerning the field of classification for laser products which function as conventional headlamps. Based on an experimental setup including a Michelson interferometer, a goniophotometer and a spectrometer, coherence lengths of 92.5 and 147.0 μm are obtained for two different laser modules. The results show that the temporal coherence of the examined radiation is appreciably higher than the temporal coherence of conventionally produced white light. Therefore, at this point in time, laser modules used in headlamps cannot be considered as customary white light sources.

Light not only enables humans to perceive their surroundings, but also influences their sleep–wake cycle, mood, concentration and performance. Targeted use of these so called nonvisual effects could also have a positive contribution in automobiles by keeping passengers alert, minimizing error rates or bootsting attention in general. Since construction space in vehicle interios is scarce, this study compared the influence of differently-sized light panels and thus solid angles on nonvisual effects. In a counterbalanced order, 32 volunteers were exposed to three lighting conditions in the morning: baseline (12 lx, 2200 K), small (200 lx, 6500 K, 0.05 sr) and large (200 lx, 6500 K, 0.44 sr). During each session of 60 min, alertness, concentration and working memory were assessed before and during light exposure. After data analysis no significant main effects of light, measurement point or interaction between light and measurement point could be seen.