State-of-the-art assistance systems monitor the driver at all times, making the roads safer. Light from OSRAM is the invisible passenger.
Traffic accidents throughout the world account for more than one million deaths and 50 million injuries every year. More than 90 percent of accidents are the result of human error. Speeding, drunk driving and other such traffic violations are major causes, but other important factors are fatigue and distractions.
This is where driver monitoring systems (DMS) provide a solution. They detect whenever a driver is not paying attention to the road or is in some way incapacitated and then warn the driver. If necessary, they take action themselves. Some top-of-the-range vehicles now have them. And the DMS trend is gaining pace. Assessment programs for new vehicles such as Euro NCAP are already promoting active driver monitoring systems. And such systems will be mandatory on semi or fully autonomous vehicles at the very least.
Alertness alert
There are a few ways in which driver monitoring can be implemented, but the principle is always the same. A camera with a CMOS image sensor monitors the driver using invisible infrared light. One option is to monitor the driver’s eyes. “Infrared light produces a reflection on the cornea which is captured by the camera,” explains Martin Wittmann, Marketing Head Sensing at OSRAM Opto Semiconductors. “By tracking eye movement we can tell whether or not the driver is looking at the road. The size of the pupils also indicates how awake the driver is. And from the movement of the eyelids we know when the driver is getting tired.
DMS systems can also check whether the seatbelt is in use and can monitor the posture of the driver’s head and upper body. Is the driver taking too long to sit up again? Is he looking for something on the passenger seat? Is his head nodding from fatigue or a sudden medical emergency? Recognizing the latter is becoming increasingly important in an aging society. But it is also an additional safety measure for professional drivers, such as truck drivers, who spend many hours behind the wheel.
No glow
Eye tracking in particular is an application that shows the need for high-quality light. The light must be powerful enough to function in daylight but must not damage the driver’s eyes. “Infrared emitters with a wavelength of 940 nanometers are now firmly established for this purpose,” says Wittmann. “We offer an unbeatable portfolio of solutions: compact in design, powerful and with different beam angles for every need.” They include infrared LEDs and infrared surface-emitting lasers, known as VCSELs. The latter are increasingly being tested because they have two key advantages. Their integrated optics produce the desired light distribution directly, which means the light source is much more compact. And they also emit light in a narrower band, which minimizes the unwanted effect of red glow even though infrared light is essentially invisible.
VCSELs are also ideal for another aspect of driver monitoring, namely identifying drivers by their facial features. This aspect is relevant for safety in that it can be used, for example, to adjust the seat position or the airbag for each driver.
Look who’s talking
Driver recognition in the broadest sense, however, will play a completely different role in the future. “Gesture recognition and speech recognition are becoming increasingly important for interactions between man and machine,” says Wittmann. “Infrared light can be used to capture commands by hand movements and gestures. For a voice recognition system, however, it is difficult to identify commands when the radio is on or a passenger is speaking at the same time. This is where infrared systems can help as they also detect the driver’s lip movements. After all, you don’t want a radio program all about coffee breaks to keep bringing the car to an abrupt halt,” says the OSRAM expert with a smile. He is convinced that invisible light will make a visible contribution to road safety and driver convenience.
