i3 | July 22, 2020

Intelligent Lighting Solutions

Robert E. Calem

Next year marks the 100th anniversary of the first car series with a full set of exterior lights — including headlamps, tail lamps, turn signals and side marker lights — according to the history of car illumination from Automotive Lighting, a subsidiary of the Italian auto industry technology supplier Magneti Marelli Group.

There is much more to car lighting today than what is visible to the human eye, however. Sophisticated lighting technology underlies advanced driver assistance systems (ADAS) as well as future self-driving car technologies and plays an important role in the vehicle’s passenger cabin. The evolution of lighting tech plays a role in vehicle styling, too.

In the early 1900s, the idea of a headlamp was to perform two tasks, says Stefan Toepfer, expert on exterior light at Mercedes-Benz AG’s car research and development unit in Sindelfingen, Germany. First providing illumination for the driver, and second to make the vehicle visible to other drivers. Today, there is also a need to inform others, and this is where high-beam flash and turn signals come into play. Toepfer adds, “Our headlamps are going into a digital world and we have the challenge to acquire new tasks for a headlamp.”

This includes using the lamps to project information onto the road surface, and leveraging their housings to host sensors used for both ADAS and autonomous driving. But such innovations are also extending to tail lamps and even interior lights are taking on new functions.

Mercedes-Benz’s Toepfer says, “The most significant safety benefit of these lighting solutions happens if we can rise up the percentage of the high beam usage.” The automaker adopted ADB in 2013, in its E-Class and S-Class cars, and since 2016 uses what it calls Multi-Beam LED headlamps across its vehicle range, down to the entry-level A-Class. In the S-Class, that feature encompasses a technology dubbed Ultra-Range Hi-Beam, which throws light as far as 650 meters (versus the typical 380 to 400 meters).

Toyota Avalon headlamps.

The Maybach line’s DLP headlamps today comprise 1.3 million pixels (“micromirrors”), which include special benefits. Toepfer says more precisely distributed light and brightness control for each pixel, based on real-time input from the vehicle’s sensors gives details about its surroundings, and the ability to project light traces or symbols onto the roadway ahead — for example, to show the driver the width of the vehicle while navigating between construction barriers. And these headlamps will be brought down market to Mercedes-Benz’s “series production” cars in the near future, he adds.

Lighting innovation does not stop at the front of the vehicle. Because they don’t have to illuminate the vehicle’s path, the tail lamps are more design driven. “The front of the vehicle is something that most of the time is passing [other vehicles] quite fast,” however, “the back of the vehicle is something very characteristic because you are driving behind” it, Toepfer explains.

Nevertheless, tail lamps have benefited from engineering innovation, such as adaptive functions that make their LEDs brighter in daylight and less intense at night, he points out.

Adding Sensors

Today, ADAS and self-driving car technology have generated industry buzz around integrating sensors in the headlamp and taillamp assemblies directly. This is technically easy, he says, since those already contain the necessary electronic control units. It poses a challenge for vehicle stylists, though, by necessitating headlamps and tail lamps to be made larger to accommodate the addition.

“The main exterior lighting trend for most of the 2010s revolved around styling,” says Chris Grant, senior engineering manager at Toyota Motor North America’s research and development unit in Saline, MI. “We saw the adoption of LED signature images as critical styling elements spread from a few luxury brands to virtually all brands — luxury and mainstream. These LED signatures were first realized through [front] daytime running lights (DRLs) and taillights, but with advances in LED efficiency and optical design, we started seeing uniquely-styled LED low and high beam units, as well, deviating from traditional round projector units or large bucket reflectors.” For example, Grant offers, the 2019 Toyota Avalon headlamp features low-profile rectangular LED low and high beam units complemented by a double chevron-shaped LED signature DRL. Meanwhile, Lexus vehicles are adorned with a “triple-eye” LED low-and-high beam unit and L-shaped DRLs and taillights “to enhance brand recognition,” he says.

“While styling is still a major focus for lighting, more recent lighting trends have revolved around safety and emotional connection,” Grant says. “The most impactful safety improvements” have come through ADB technologies. Those have followed an evolutionary path from “matrix beams” that fade individual LEDs on and off to prevent glare to oncoming and preceding vehicles while maximizing illumination for the driver, to a system named BladeScan Type AHS (Adaptive High beam System) that Lexus unveiled last year.

Like the more sophisticated Maybach ADB system, BladeScan shines light from LEDs onto a blade mirror spinning at high speed, thus projecting the light onto a lens, and illuminating the road ahead. LEDs are switched on and off in sync with the rotation of the blade, illuminating portions of the road that may otherwise be difficult to see (such as the shoulder of the road), while not bothering other drivers.

Innovative HD headlamps from Mercedes-Benz help keep pedestrians safe.

But to keep system costs down, BladeScan uses an array of just 10 LEDs contained in a module sitting at the inner corner of each headlamp, alongside the triple-eye units, and the light is cast diagonally across the rotating blade mirror.

Regulators have not yet approved the technology for use in vehicles sold in the U.S., despite automakers’ pressing the issue. “As we wait to roll them out in the U.S., ADB systems are constantly evolving — resolution is improving, from less than 10 light segments to hundreds, thousands or even millions of light pixels, along with smoother transitions,” Grant says. “New features are being added, such as local dimming of reflective signs to prevent glare, and marking lights to highlight pedestrians, animals and other obstacles. The evolution of ADB systems is closely aligned with the evolution of vehicle camera systems, which provide most of the key information needed for ADB.”

Of course, it is easy to assume that when a car is self-driving it will not need illumination from a headlamp that is intended to help a human driver. Grant explains, the mix of LiDARs and camera sensors used in self-driving cars do require a mix of visible and invisible light to operate correctly.

More, some automakers have already incorporated ADAS sensors in lamp assemblies. For years both Ford and FCA have built radars for blind spot detection systems into pickup truck and SUV tail lamps, Audi has integrated radar sensors with headlamps, and General Motors has integrated two cameras into the center stop lamp of its Chevy Silverado pickup truck, Grant says.

Creating an Emotional Bond with Lighting

Light can build an emotional connection with a vehicle including dynamic “welcome lighting” and “farewell lighting”, which use software to fade individual LEDs on and off at different increments and create animation sequences. “Depending on what the automaker wants customers to feel about their vehicle, or brand as a whole,” he explains, some may convey a soft, organic sensibility while others may seem more technical. “Both are very effective at enhancing the emotional connection between the customer and their vehicle,” Grant adds.

For instance, Ford Motor Co.’s Lincoln brand features Embrace, which activates when a key holder approaches the vehicle (welcome) or leaves (farewell). In welcome mode Embrace lights up the signature LED headlamp and tail lamp elements and the running boards beneath the doors, projects a Lincoln star logo on the ground beside the vehicle, and turns on ambient lighting in the passenger cabin.

Embrace “plays into what we’re seeing at CES but other shows, too — more animation in the lights,” says Todd Clark, chief engineer for lighting, mechatronics and switches at Ford in Dearborn, MI. “The challenge is delivering that technology that can wow the customer at a cost that is affordable,” Clark says. Ford is accomplishing this by standardizing the necessary electronics across the company’s entire product portfolio. He says, “The building blocks of what we’ve set with Lincoln Embrace, we can scale up to other animation in the future.”

Further in the future Clark foresees an Embrace-like function targeting rideshare vehicles such as using a custom light color on the outside to identify the rider’s vehicle (selected by the user in the service’s app) or lighting up the rider’s seat in a selected color.

Another trend Ford has identified is the use of smart surfaces that light up when appropriate but otherwise remain dark, and these could include both interior and exterior trim pieces, and hard or soft materials such as leather and wood. “We’re pushing this as far as the art of the possible,” Clark says.

At least one automaker is studying lighting design outside the industry for ideas on how to style car interiors. “We look to architectural concepts — how they’re using materials like different plastics and glass, and laser etching,” says Mike Nicholas, chief designer of lighting, badging and under hood design at FCA in Auburn Hills, MI. “We used to do traditional graining of our lenses and bezels. Now with laser etching you can actually design textures, and when the light hits it, it has this dynamic effect.”

Also, with the advent of driver and passenger monitoring systems, there’s a health and wellness application for car interior lighting, says Dominique Massonie, head of innovation at Elektrobit, based in Erlangen, Germany. He imagines, for example, automatically adjusting the cabin lighting to help wake a sleepy driver at night.

Indeed, lighting — or more specifically photonics — is itself part and parcel of car sensing, says Mike Godwin, director of automotive marketing at Osram Opto Semiconductors Inc. in Novi, MI. It can be used for eye gaze and emotion detection inside the passenger cabin. And then, reacting to the findings, it can be adjusted to, for example, mitigate motion sickness.

“Everyone’s looking for those right solutions,” Godwin affirms. “The car makers are looking for how are they going to differentiate their brand, and differentiate the outer shell of the vehicle, plus the experience that is related on the interior of the vehicle.”

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