Proceedings Article | 27 February 2015
KEYWORDS: Electronics, Roads, 3D acquisition, Modulation, Imaging systems, Cameras, Sensors, Stereoscopic cameras, 3D metrology, Ranging
Advanced Driver Assistance Systems (ADAS) are the most advanced technologies to fight road accidents. Within
ADAS, an important role is played by radar- and lidar-based sensors, which are mostly employed for collision avoidance
and adaptive cruise control. Nonetheless, they have a narrow field-of-view and a limited ability to detect and
differentiate objects. Standard camera-based technologies (e.g. stereovision) could balance these weaknesses, but they
are currently not able to fulfill all automotive requirements (distance range, accuracy, acquisition speed, and frame-rate).
To this purpose, we developed an automotive-oriented CMOS single-photon camera for optical 3D ranging based on
indirect time-of-flight (iTOF) measurements.
Imagers based on Single-photon avalanche diode (SPAD) arrays offer higher sensitivity with respect to CCD/CMOS
rangefinders, have inherent better time resolution, higher accuracy and better linearity. Moreover, iTOF requires neither
high bandwidth electronics nor short-pulsed lasers, hence allowing the development of cost-effective systems. The
CMOS SPAD sensor is based on 64 × 32 pixels, each able to process both 2D intensity-data and 3D depth-ranging
information, with background suppression. Pixel-level memories allow fully parallel imaging and prevents motion
artefacts (skew, wobble, motion blur) and partial exposure effects, which otherwise would hinder the detection of fast
moving objects. The camera is housed in an aluminum case supporting a 12 mm F/1.4 C-mount imaging lens, with a
40°×20° field-of-view. The whole system is very rugged and compact and a perfect solution for vehicle’s cockpit, with
dimensions of 80 mm × 45 mm × 70 mm, and less that 1 W consumption. To provide the required optical power (1.5 W,
eye safe) and to allow fast (up to 25 MHz) modulation of the active illumination, we developed a modular laser source,
based on five laser driver cards, with three 808 nm lasers each.
We present the full characterization of the 3D automotive system, operated both at night and during daytime, in both
indoor and outdoor, in real traffic, scenario. The achieved long-range (up to 45m), high dynamic-range (118 dB), highspeed
(over 200 fps) 3D depth measurement, and high precision (better than 90 cm at 45 m), highlight the excellent
performance of this CMOS SPAD camera for automotive applications.
