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

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. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

Analog SiPM in Planar CMOS Technology

Silicon Photomultipliers (SiPMs) are emerging single photon detectors used in many applications requiring large active area, photon number resolving capability and immunity to magnetic fields. We developed planar analog SiPMs in a reliable and cost-effective CMOS technology with a total photosensitive area of about 1×1 mm2. Three devices with different active areas, and fill-factor (21%, 58.3%, 73.7%), have been characterized. The maximum photon detection efficiency is in the near-UV and tops at 38% (fill-factor included), with a dark count rate of 125 kcps. Gain and crosstalk depend on the active area size and are comparable to those of commercial best-in-class custom-technology SiPMs. However our full CMOS processing enables advanced SiPM single-chip systems where transistors and further on chip electronics can be integrated together with the detectors

Photon-efficient imaging with a single-photon camera

Reconstructing a scene's 3D structure and reflectivity accurately with an active imaging system operating in low-light-level conditions has wide-ranging applications, spanning biological imaging to remote sensing. Here we propose and experimentally demonstrate a depth and reflectivity imaging system with a single-photon camera that generates high-quality images from ∼1 detected signal photon per pixel. Previous achievements of similar photon efficiency have been with conventional raster-scanning data collection using single-pixel photon counters capable of ∼10-ps time tagging. In contrast, our camera's detector array requires highly parallelized time-to-digital conversions with photon time-tagging accuracy limited to ∼ns. Thus, we develop an array-specific algorithm that converts coarsely time-binned photon detections to highly accurate scene depth and reflectivity by exploiting both the transverse smoothness and longitudinal sparsity of natural scenes. By overcoming the coarse time resolution of the array, our framework uniquely achieves high photon efficiency in a relatively short acquisition time

High-speed integrated QKD system

Quantum key distribution (QKD) is nowadays a well-established method for generating secret keys at a distance in an information-theoretically secure way, as the secrecy of QKD relies on the laws of quantum physics and not on computational complexity. In order to industrialize QKD, low-cost, mass-manufactured, and practical QKD setups are required. Hence, photonic and electronic integration of the sender's and receiver's respective compo-nents is currently in the spotlight. Here we present a high-speed (2.5 GHz) integrated QKD setup featuring a transmitter chip in silicon photonics allowing for high-speed modulation and accurate state preparation, as well as a polarization-independent low-loss receiver chip in aluminum borosilicate glass fabricated by the femtosecond laser micromachining technique. Our system achieves raw bit error rates, quantum bit error rates, and secret key rates equivalent to a much more complex state-of-the-art setup based on discrete components [A. Boaron et al., Phys. Rev. Lett. 121, 190502 (2018)].& COPY; 2023 Chinese Laser Pres

Indirect time-of-flight 3D ranging based on SPADs

Systems for 3D image acquisition are the enabling technology for a number of applications such as architectural studies, safety and security, automotive. Single-sensor active-illumination cameras are the most promising system, ensuring a good depth measurement accuracy combined with a simple structure (no double sensor required), simplest measurement algorithm and night and daytime operation. These systems are based on the measurement of the time delay between the emission of light signal and the detection of the back-reflected signal (Time of Flight - TOF). The direct measurement of the time delay between two adjacent pulses is called direct TOF (dTOF), while if the time delay is obtained starting from the phase delay of a periodic waveform we speak of indirect TOF (iTOF). We present two different 0.35μm CMOS Silicon mini-arrays for iTOF 3D ranging based on square and sinusoidal waveforms, in which the sensitive element is a Single-Photon Avalanche Diode (SPAD)

3D SPAD camera for Advanced Driver Assistance

We present a 3D-ranging camera based on the optical indirect Time-of-Flight technique, suitable for automotive applications. The camera is based on a 64Ã\u9732-pixel chip, integrating a Single-Photon Avalanche Diode (SPAD) in each pixel, fabricated in an automotive-certified CMOS technology, and on an 808 nm active illuminator, emitting 1.5 W average optical power. Thanks to the SPAD single-photon sensitivity and the in-pixel processing, the camera provides a precision better than 1 m over a 40° Ã\u97 20° field-of-view, at 45 m distance