Lightening the mood
At Audi, lighting drives innovation in both design and technology. And when paired with conditionally automated driving, it opens the door to exciting future functions and applications. In the coming years, suitably equipped vehicles will allow drivers to let go of the steering wheel and lean back as passengers. The upshot is that all users will enjoy greater freedoms. This means interior lighting design will assume an ever more important role. After all, pleasant mood lighting can contribute to a sense of well-being. Plus, light modulates human circadian rhythms.
The importance of blue light
This raises an interesting question: How can we make selective use of these properties? That’s precisely what Arvid Niemeyer, a doctoral student at Audi, is working on. “Human Centric Lighting is the answer because this concept prioritizes human needs,” he says, adding, “Audi is innovation-driven and willing to draw inspiration also from nature. We know that bright, cool daylight—like what we get at noon—energizes, stimulates and improves alertness. This effect can also be cultivated with artificial light.”
In the context of tomorrow’s mobility, when conditionally automated vehicles will already be on the road, imagine the following scenario playing out: Someone is en route from one place to another and must use the time to prepare for an important meeting. Concentration is key. “As a passenger in the vehicle, the individual can adjust the interior lighting by increasing the light’s blue component to enhance focus. Studies have shown it’s important that the light source has a large area and is positioned directly overhead—just as the midday sun is at its zenith.” If there is a decrease in the blue component, the effect also diminishes. This is why warm light with a high red and low blue component is seen to induce relaxation. “Both have their uses, but the energizing effect is currently the more relevant application for us."
Timekeeper behind our daily routines
In order to better understand how light affects us, we need to take a closer look at our acquired behavior patterns and biological processes. As Arvid Niemeyer explains, “We have simply internalized the rhythm of day and night. This is what we call our circadian rhythm—a sleep-wake cycle completed once roughly every 24 hours.” Our bodies have adapted to this rhythm and function differently during the day than at night. Not just body temperature and hormone levels but even breathing and circulation adhere to the cycle. All these processes take their cue from our biological clock, which keeps time by the light. As sensory organs that respond to light, our eyes facilitate the cyclical shift.
“In 2002, research on the topic revealed that in addition to rod and cone photoreceptors, which are responsible for seeing at night and in color respectively, there is also a third type of receptor in the retina for detecting incident light. What makes this kind so special is that it does not contribute to sight, but instead regulates certain hormones in the body. These ganglion cells contain melanopsin proteins and are found in the uppermost layer of the retina.”
After completing a Bachelor of Engineering in Mechatronics at the Munich University of Applied Sciences, specializing in medical technology, Arvid Niemeyer earned a Master of Science in Mechanical Engineering specializing in technical optics and precision engineering at the University of Stuttgart. Arvid Niemeyer is now working on his doctorate at Audi in the interior lighting development unit. His work is facilitated by a cooperation with the Light Technology Institute (LTI) at the Karlsruhe Institute of Technology.
A scientific milestone
When stimulated by a burst of light, they trigger a nerve impulse. Rather than following the same pathway as impulses sent via the rods and cones, the signal is relayed to the suprachiasmaticus nucleus. Comprising two nuclei, which are about the size of a grain of rice, they act as the main circadian clock in humans, regulating pituitary gland activity. This in turn releases hormones that synchronize biological rhythms, adjusting metabolic rates according to the time of day.
Other nerve pathways run to activation centers in the brain as well as to relay points in the spinal cord. In this way, sensory stimuli and hormones quietly modulate many autonomic processes without us being consciously aware of them. Among other things, these include our biological clock. Insight into this mechanism marks a scientific milestone, at the same time paving the way for the concept of Human Centric Lighting.
Audi conducts three studies
Arvid Niemeyer is not the only one investigating Human Centric Lighting—it’s also Michael Weng’s specialty. Michael is a doctoral student at Volkswagen Group Innovation. Drawing on the initial findings from previous field research with the Audi A8 as a point of departure, the pair have conducted follow-up studies. The field research made use of a specially adapted makeup mirror lamp to support the occupants’ circadian rhythms. Two out of three participants confirmed that the light made them feel more alert in the morning. Two further laboratory studies in which 32 participants sat in a darkened box with different light sources also lent credence to the theory that a high blue component in lighting counteracts fatigue.
Arvid Niemeyer focused on the morning hours, while his colleague from Volkswagen Group Innovation examined the effects in the evening hours. “In his laboratory study, Michael Weng also looked at rising levels of sleep hormone melatonin at the end of the day. The results corroborated the participants’ subjective perceptions. Light with a high blue component was able to significantly suppress melatonin levels until late in the evening. As a result, people feel more alert.”
The third Audi study on light’s effects on people was conducted using a driving simulator. The study was able to not only probe situations where participants acted as drivers but also where they were occupants in conditionally automated cars—i.e. without having to operate the vehicle. Even under these conditions, the initial results are positive. This is an exciting line of research. Clearly, light is more than just illumination.