Morsy Ayman, Kuijk Maarten
Department of Electronics and Informatics, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium.
Sensors (Basel). 2024 Aug 20;24(16):5380. doi: 10.3390/s24165380.
Time of flight is promising technology in machine vision and sensing, with an emerging need for low power consumption, a high image resolution, and reliable operation in high ambient light conditions. Therefore, we propose a novel direct time-of-flight pixel using the single-photon avalanche diode (SPAD) sensor, with an in-pixel averaging method to suppress ambient light and detect the laser pulse arrival time. The system utilizes two orthogonal sinusoidal signals applied to the pixel as inputs, which are synchronized with a pulsed laser source. The detected signal phase indicates the arrival time. To evaluate the proposed system's potential, we developed analytical and statistical models for assessing the phase error and precision of the arrival time under varying ambient light levels. The pixel simulation showed that the phase precision is less than 1% of the detection range when the ambient-to-signal ratio is 120. A proof-of-concept pixel array prototype was fabricated and characterized to validate the system's performance. The pixel consumed, on average, 40 μW of power in operation with ambient light. The results demonstrate that the system can operate effectively under varying ambient light conditions and its potential for customization based on specific application requirements. This paper concludes by discussing the system's performance relative to the existing direct time-of-flight technologies, identifying their strengths and limitations.
飞行时间是机器视觉和传感领域一项很有前景的技术，当前对低功耗、高图像分辨率以及在高环境光条件下可靠运行的需求不断增加。因此，我们提出了一种使用单光子雪崩二极管（SPAD）传感器的新型直接飞行时间像素，采用像素内平均方法来抑制环境光并检测激光脉冲到达时间。该系统利用施加到像素的两个正交正弦信号作为输入，这两个信号与脉冲激光源同步。检测到的信号相位表示到达时间。为了评估所提出系统的潜力，我们开发了分析模型和统计模型，用于评估在不同环境光水平下到达时间的相位误差和精度。像素模拟表明，当环境光与信号之比为120时，相位精度小于检测范围的1%。制作并表征了一个概念验证像素阵列原型，以验证系统的性能。该像素在有环境光的情况下运行时平均功耗为40微瓦。结果表明，该系统能够在不同环境光条件下有效运行，并且具有根据特定应用需求进行定制的潜力。本文最后讨论了该系统相对于现有直接飞行时间技术的性能，确定了它们的优势和局限性。
