Contents I. Introduction
In automotive applications like advanced driver assistance systems (ADAS) and autonomous driving (AD) a fast and reliable monitoring of the environment is absolutely essential. Most of the today used light detection and ranging (LIDAR) sensors employ laser scanners to sample the target scene. Since these scanners are very expensive due to the required high precision mechanical parts, the request for affordable solid state flash LIDAR sensors is increasing [1]. In flash systems the whole target scene is illuminated with a single laser shot obviating moving parts and reducing the cost of the system. Since single-photon avalanche diodes (SPAD) achieve a very high sensitivity and can be fabricated in standard CMOS processes, thanks to the improvements in CMOS technology, SPADs are a favorable choice for implementing cost-efficient time-of-flight (TOF) sensors [2]. Two general techniques for distance measurement based on TOF can be distinguished when SPADs are used as detector technology [3]. We use the direct measurement technique. Here an electronic stopwatch – e.g. a time-to-digital-converter (TDC) – measures the time between the emission and reception of a short laser pulse. Therefore, if other statistical effects are neglected, the distance precision is determined by the resolution of the TDC [4]. In this paper we present a pixel SPAD-based line sensor fabricated in an automotive certificated CMOS process. Since particular requirements regarding the ambient light exist in automotive applications, photon coincidence detection as presented in [5] has been employed to reduce its influence and allow measurements at high ambient light.
