Indirect time-of-flight (iToF) imaging allows us to capture dense depth information at a low cost. However, iToF imaging often suffers from multipath interference (MPI) artifacts in the presence of scattering media, resulting in severe depth-accuracy degradation. For instance, iToF cameras cannot measure depth accurately through fog because ToF active illumination scatters back to the sensor before reaching the farther target surface. In this work, we propose a polarimetric iToF imaging method that can capture depth information robustly through scattering media. Our observations on the principle of indirect ToF imaging and polarization of light allow us to formulate a novel computational model of scattering-aware polarimetric phase measurements that enables us to correct MPI errors. We first devise a scattering-aware polarimetric iToF model that can estimate the phase of unpolarized backscattered light. We then combine the optical filtering of polarization and our computational modeling of unpolarized backscattered light via scattering analysis of phase and amplitude. This allows us to tackle the MPI problem by estimating the scattering energy through the participating media. We validate our method on an experimental setup using a customized off-the-shelf iToF camera. Our method outperforms baseline methods by a significant margin by means of our scattering model and polarimetric phase measurements.

翻译：间接飞行时间（iToF）成像技术能够以低成本获取稠密深度信息。然而，在散射介质存在时，iToF成像常受到多路径干扰（MPI）伪影的影响，导致深度精度严重下降。例如，当透射式主动照明光在到达远距离目标表面前被雾散射回传感器时，iToF相机便无法准确测量深度。本文提出一种偏振iToF成像方法，能够稳健地透过散射介质捕获深度信息。基于对间接ToF成像原理与光偏振特性的深入观察，我们构建了一种新颖的散射感知型偏振相位测量计算模型，从而实现对多路径干扰（MPI）误差的校正。首先设计了一个散射感知的偏振iToF模型，用于估算非偏振后向散射光的相位；继而结合偏振光学滤波与通过相位-振幅散射分析建立的未偏振后向散射光计算模型，利用参与介质中的散射能量估算解决MPI问题。我们使用定制的商用iToF相机搭建实验装置验证了该方法，结果表明，基于散射模型与偏振相位测量技术，本方法在性能上显著优于基准方法。