Abstract
Light detection and ranging (LiDAR) systems based on silicon single-photon avalanche diodes (SPAD) offer several advantages, like the fabrication of system-on-chips with a co-integrated detector and dedicated electronics, as well as low cost and high durability due to well-established CMOS technology. On the other hand, silicon-based detectors suffer from high background light in outdoor applications, like advanced driver assistance systems or autonomous driving, due to the limited wavelength range in the infrared spectrum. In this paper we present a novel method based on the adaptive adjustment of photon coincidence detection to suppress the background light and simultaneously improve the dynamic range. A major disadvantage of fixed parameter coincidence detection is the increased dynamic range of the resulting event rate, allowing good measurement performance only at a specific target reflectance. To overcome this limitation we have implemented adaptive photon coincidence detection. In this technique the parameters of the photon coincidence detection are adjusted to the actual measured background light intensity, giving a reduction of the event rate dynamic range and allowing the perception of high dynamic scenes. We present a 192 × 2 pixel CMOS SPAD-based LiDAR sensor utilizing this technique and accompanying outdoor measurements showing the capability of it. In this sensor adaptive photon coincidence detection improves the dynamic range of the measureable target reflectance by over 40 dB.
Highlights
To bring autonomous vehicles to the road, a fast and reliable high-resolution perception of the environment is essential
In this paper we present a technique to improve the measurement performance at high ambient light. This technique can be implemented in addition to the aforementioned techniques for ambient light rejection and is especially suitable for single-photon avalanche diode (SPAD)-based light detection and ranging (LiDAR)
MHz for for the the laser laser pulse width ofof1010ns, pulse and background light; and (b) the probability density for photon detection detection rates rates of 30 MHz achieved by increasing the photon detection efficiency (PDE) or target reflectance reflectance by by aa factor factor of of three
Summary
To bring autonomous vehicles to the road, a fast and reliable high-resolution perception of the environment is essential. Since commercial laser sources exhibit a certain emission bandwidth, fabrication induced variation, and temperature dependence, the filter bandwidth has to be chosen carefully to not sacrifice available laser power [12] Another common approach to reduce the influence of high ambient light is the accumulation of multiple time measurements. A trade-off between frame rate and reliability has to be made Another approach to cope with strong background light is the use of scanning lasers which illuminate only a single spot or line of the target scene at once [14]. In this paper we present a technique to improve the measurement performance at high ambient light This technique can be implemented in addition to the aforementioned techniques for ambient light rejection and is especially suitable for single-photon avalanche diode (SPAD)-based LiDAR sensors. The measurements prove the feasibility of improving the measureable dynamic range of target reflectance by adjusting the coincidence parameters to the ambient light conditions
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