Page 49 - EE Times Europe Magazine - June 2025

EE|Times EUROPE 49

AUTONOMOUS DRIVING | IN-CABIN MONITORING SYSTEMS
Time-of-Flight and Radar Take the Wheel

By Rebecca Pool

Can a new generation of in-cabin sensors deliver the safety essential for tomorrow’s
autonomous cars?

s cars steer ever closer to autonomous driving, driver monitoring than 25 million systems are being used in
and in-cabin monitoring systems are set to play a truly critical role augmented-reality systems, smartphones,
driver monitoring and in-cabin sensing sys-
in passenger safety. 3D time-of-flight (ToF) imagers and 60-GHz tems, and more.
A radar are two sensors that could make a big difference, given their To gather data, these devices illuminate the
abilities to detect occupants and monitor behavior—and the two technologies area of interest with modulated infrared light,
which reflects and is then detected by an
are already being integrated into such monitoring platforms. imager and compared with the emitted light.
Distance information in each pixel, obtained
Driver monitoring systems (DMS) have been around for more than from the detected phase shifts, is combined with a 2D grayscale image
a decade, typically relying on infrared cameras to assess attentiveness to generate 3D information of the scene. And in a car, such 3D data is
by directly observing a driver’s facial orientation, glance behavior, critical.
and eye movements in real time. Today, global safety regulations are Smart airbags, for example, use sensors to detect driver or occupant
driving the integration of more advanced driver distraction warn- size as well as motion so that the best timing and deployment force
ing (ADDW) systems and wider in-cabin monitoring systems into can be determined. “In this scenario, we really need body tracking,
vehicles. estimates of the size and weight of passengers, even how they are
The EU has mandated that all newly registered vehicles be capable seated in front of the airbag,” Lass said. “We can get some of this
of detecting driver drowsiness and distraction by 2026. In parallel, information from 2D cameras, but we really need depth information,
the European New Car Assessment Programme (Euro NCAP) requires and this is a key example of where 3D and time-of-flight cameras can
new cars to have a DMS—with a raft of features beyond driver come into play.”
impairment—to achieve a five-star safety rating. Think child presence Unlike conventional cameras, Lass added, 3D ToF sensors can
detection, information on numbers of occupants in a vehicle, posture provide robust data under all ambient light, as they are not affected by
monitoring to enhance seat belt use, airbag parameters for smart shadows and sunlight overexposure. But the technology has its limits.
airbags, and more. For example, ToF imagers cannot directly measure vital signs, a
“The industry, driven by Euro NCAP, has really been heading toward critical aspect of driver impairment monitoring. The sensors will
direct driver monitoring, which is now leading us to these advanced also struggle to provide the higher resolution demanded by the
driver distraction warning systems,” said Martin Lass, head of ToF wide-view cameras that will be used to monitor all occupants in a
business at Infineon Technologies. “These systems will really detect car. But an alternative sensor, the 60-GHz radar, could help.
if, say, a driver has his or her eyes on
the road, their hands on the steering
wheel, or if something is being handed
over from the back of the car to the
driver.”

HIDDEN DEPTHS
The complex use cases associated with
ADDW systems will demand more than
the 2D cameras and infrared sensors
used in earlier driver monitoring sys-
tems. 3D ToF sensors are one option
currently under consideration. The
sensors can accurately detect objects
and track movement, making them
suitable for mapping occupants and
monitoring gestures in a car.
The technology is hardly new,
having been manufactured by the
likes of Texas Instruments,
STMicroelectronics, Melexis, and
Infineon for several years. Infineon
partnered with 3D ToF hardware and
software pioneer pmdtechnologies
(Siegen, Germany) some time ago to More complex in-cabin monitoring is driving the development of advanced sensors as well as
develop ToF imagers, and today, more sensor fusion. (Source: Infineon Technologies)

www.eetimes.eu | JUNE 2025