SPADAS: a high-speed 3D single-photon camera for advanced driver assistance systems

Abstract

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.

3D SPAD camera for Advanced Driver Assistance

“…From our measurements, we can infer that the illumination system is able to uniformly illuminate the scene without shadow zones and, although the camera resolution is limited to 2048 pixels, the integration of all information provided by the SPAD sensor enables to generate images rich of details, thus allowing to locate and recognize objects in the scene through real-time image processing. A video, showing all the potentialities of the automotive 3D SPAD camera is available at [13].…”

Automotive Three-Dimensional Vision Through a Single-Photon Counting SPAD Camera

“…Since frames are taken one out of 100, the estimation of the second car's speed is 6 km/h.From the previous pictures, it is clear that the illumination system is able to uniformly illuminate the scene without shadow zones and, although the camera resolution is limited to 2048 pixels, the integration of all information provided by the SPAD sensor permit to generate images rich of details, thus allowing to easily locate and recognize objects in the scene through realtime image processing. A video, showing all the potentialities of the automotive 3-D SPAD camera is available here[35].…”