Graduate School of Science and Technology, Shizuoka University, Hamamatsu, Shizuoka 432-8011, Japan.
Research Institute of Electronics, Shizuoka University, Hamamatsu, Shizuoka 432-8011, Japan.
Sensors (Basel). 2021 Jan 11;21(2):454. doi: 10.3390/s21020454.
This paper presents a high-linearity high-resolution time-of-flight (ToF) linear-array digital image sensor using a time-domain negative feedback technique. A coarse ToF measurement loop uses a 5-bit digital-to-time converter (DTC) and a delayed gating-pulse generator for time-domain feedback to find the zero of the difference between ToF and the digital estimate of the gating-pulse delay while maintaining a constant operating point of the analog readout circuits. A fine ToF measurement uses a delta-sigma modulation (DSM) loop using the time-domain feedback with a bit-stream signal form. Because of the self-contained property of the DSM for low distortion and noise exploited by the oversampling signal processing, the proposed technique provides high-linearity and high-range resolution in the fine ToF measurement. A prototype ToF sensor of 16.8 × 16.8 μm two-tap pixels and fabricated in a 0.11 μm (1P4M) CMOS image sensors (CIS) process achieves +0.9%/-0.47% maximum nonlinearity error and a resolution of 0.24 mm (median) for the measurement range of 0-1.05 m. The ToF sensor produces an 11-bit fully digital output with a ToF measurement time of 22.4 ms.
本文提出了一种采用时域负反馈技术的高线性度、高分辨率飞行时间（ToF）线性阵列数字图像传感器。粗 ToF 测量环路使用 5 位数字到时间转换器（DTC）和延迟选通脉冲发生器进行时域反馈，以找到 ToF 与数字估计的选通脉冲延迟之间的差值的零点，同时保持模拟读出电路的恒定工作点。细 ToF 测量使用使用位流信号形式的时域反馈的 delta-sigma 调制（DSM）环路。由于 DSM 具有自包含特性，可用于低失真和噪声，因此采用过采样信号处理，所提出的技术在细 ToF 测量中提供了高线性度和高范围分辨率。一个 16.8×16.8μm 两抽头像素的 ToF 传感器原型和在 0.11μm（1P4M）CMOS 图像传感器（CIS）工艺中制造，实现了+0.9%/-0.47%的最大非线性误差和 0.24mm（中位数）的分辨率对于 0-1.05m 的测量范围。ToF 传感器产生具有 22.4ms ToF 测量时间的 11 位全数字输出。
