Getting behind the wheel of a car is the riskiest thing that most people do every day, safety statistics say. And highway hazards only get worse at nighttime when about a half of fatal road crashes occur. So better illuminating the way forward on dark streets is key to improving overall driving safety.
Perhaps more so than some other car companies, General Motors’ German brand, Opel, has long focused on making night-driving safer, having previously developed headlights whose light beams are steered by the direction of the front wheels and an anti-dazzle high-beam system that automatically switches the headlamps to low-beam when a forward-facing camera recognizes others on the road ahead. In addition, the carmaker just introduced LED-matrix headlamps that provide glare-free, high-beam road illumination patterns that are automatically and constantly adapted for varying traffic conditions.
Opel’s next advance in automotive lighting will be smart eye-tracking technology that will automatically adjust the direction and intensity of headlights to follow the direction of the driver’s gaze, said Ingolf Schneider, Director of Lighting Technology at Opel. This next-generation system, which “we assume would be introduced as a product in 2019 or 2020,” uses a dashboard camera and infrared sensors that together scan the driver’s face and eyes more than 50 times a second at dusk and nighttime to determine the motorist’s line of sight.
Light where you’re looking
“When we first started brainstorming about the problem of night visibility several years ago, we asked what can we do to have light fall exactly in the direction in which the driver is looking,” he recalled. “We needed to know exactly what the driver is looking at.” Since then, his engineering team at Opel’s International Technical Development Center in Rüsselsheim has been working through increasingly sophisticated solutions.
“Swiveling headlights that are steered by the wheel direction certainly provide a clear safety benefit,” Schneider explained, “but there are certain situations when you look elsewhere than down the road, say, at an unlighted overhead sign. In that case, having the light directed toward what you’re watching is a big help. And it’s not possible with car-wheel-based steering.”
The new gaze-directed technology provides illumination benefits that are akin to wearing a camping-type headlamp when you’re setting up a tent at night, navigating a dark cave, or bicycling at night. It helps to have the light directly shining on what you’re looking at.
“We started working on the latest generation of eye-tracking technology last autumn,” Schneider reported. “Whereas in years past we had worked with sensors on helmets and near the steering wheel for developmental and testing purposes, new cameras had since come on the scene that were much more effective. A single, low-cost sensor could now check eye movements very precisely.”
Three steps toward progress
Schneider said that his team of engineers had first worked with helmet sensors when developing its current AFL+ (Adaptive Forward Lighting) technology. In the second R&D step, they collaborated with students at the Technical University of Darmstadt’s Laboratory of Lighting Technology, who are led by Professor Tran Quoc Khanh. “The students wrote eye-tracking programs for Web-based cameras, but we recognized it would take a lot of data capacity on board the car to do it that way.”
The prototype system translated the camera data into commands for electronically controlled headlight actuators, which quickly aligned the headlamp projectors. Although this technique came close to a solution, the calculations took too long and the recording rate of the webcam was too slow to match fast-changing traffic conditions.
“During the latest step,” he said, “we saw how the Apple iPad and other digital readers now feature eye-controlled page-turning features, so we took this capability, found an off-the-shelf camera that we could modify and adapt, and built a system that the Darmstadt students will evaluate on the road during the next few years.”
Optimization of the camera’s operating parameters and the adaptation of the eye-tracking algorithm led to the current prototype system. The camera features peripheral infrared sensors and central photo-diodes that together enable rapid eye scanning. And much faster data processing and transmission allow the headlamp actuators to react almost instantaneously to adjust horizontally and vertically.
Schneider said that the dashboard sensors determine the driver’s gaze-direction “by looking at the plane of the face in relation to the position of the pupils.” That plane, he noted, is established by finding the location of the motorist’s eye-sockets and the back of the nostrils. Then the resulting face plane is compared to the pupil position to resolve the eyes’ line of sight.
He added that “the eye-tracking system is not disturbed if the driver is wearing glasses,” and that it compensates for rapid, transient eye movements as they naturally and unconsciously jump from one focal point to another. If the headlamps were allowed to follow this movement precisely, the vehicle’s forward illumination would jerk around erratically as the headlamps retargeted, he said.
“A motorist’s gaze can easily briefly move 30 to 40 degrees to the right or left,” for example, when talking to the front-seat occupant, Schneider said. “If the gaze moves too far or too fast, the system must be smart enough to filter out that extraneous movement and insert a delay to maintain safe, consistent illumination.”
“To overcome this problem, we have developed a sophisticated delay algorithm, which ensures a suitably flowing movement for the light cone,” he explained. Even if the driver is momentarily distracted and takes their eyes of the road, the lights will continue illuminating in the direction of travel.
“Another major benefit is that the eye-tracker doesn’t have to be individually calibrated for a particular driver,” Schneider said. “The system works perfectly with anyone behind the wheel, no matter what their size.” The upcoming road testing by the Darmstadt students “will help figure out the right amount of filtering” that provides the greatest safety and utility.
A Laboratory demonstration of Opel's eye-tracking headline system can be viewed at: https://www.youtube.com/watch?v=wGV1YHQDXaY.