A comprehensive study of time-of-flight non-line-of-sight imaging

2026-03-10

AI Summary

This work addresses the challenge of fair comparison among existing time-of-flight (ToF) non-line-of-sight (NLOS) imaging methods, which stems from inconsistencies between their forward models and hardware implementations. To resolve this, we propose a unified modeling framework that enables systematic evaluation of mainstream ToF NLOS techniques under identical forward models, hardware platforms, and photon budgets. Our analysis reveals intrinsic connections between these methods and both the Radon transform and frequency-domain phasor models. Experimental results using data captured with picosecond-resolution ToF sensors demonstrate that, under matched conditions, the approaches exhibit comparable performance in spatial resolution, visibility, and noise robustness, with observed differences primarily attributable to method-specific hyperparameters. This study establishes a standardized benchmark and a theoretically unified perspective for advancing NLOS imaging research.

Technology Category

• Computer Vision: Other Foundations of Computer Vision
• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Search and Optimization: Non-convex Optimization

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Web performance, measurement, and characterization
• Search and Retrieval-Augmented AI: Web evaluation methodologies and metrics
• Graph Algorithms and Modeling for the Web: Algorithms and analysis for incomplete, noisy, or partially observed Web-related graphs

Abstract

Time-of-Flight non-line-of-sight (ToF NLOS) imaging techniques provide state-of-the-art reconstructions of scenes hidden around corners by inverting the optical path of indirect photons scattered by visible surfaces and measured by picosecond resolution sensors. The emergence of a wide range of ToF NLOS imaging methods with heterogeneous formulae and hardware implementations obscures the assessment of both their theoretical and experimental aspects. We present a comprehensive study of a representative set of ToF NLOS imaging methods by discussing their similarities and differences under common formulation and hardware. We first outline the problem statement under a common general forward model for ToF NLOS measurements, and the typical assumptions that yield tractable inverse models. We discuss the relationship of the resulting simplified forward and inverse models to a family of Radon transforms, and how migrating these to the frequency domain relates to recent phasor-based virtual line-of-sight imaging models for NLOS imaging that obey the constraints of conventional lens-based imaging systems. We then evaluate performance of the selected methods on hidden scenes captured under the same hardware setup and similar photon counts. Our experiments show that existing methods share similar limitations on spatial resolution, visibility, and sensitivity to noise when operating under equal hardware constraints, with particular differences that stem from method-specific parameters. We expect our methodology to become a reference in future research on ToF NLOS imaging to obtain objective comparisons of existing and new methods.

Problem

• Time-of-Flight
• non-line-of-sight imaging
• performance evaluation
• method comparison
• hidden scene reconstruction

Innovation

• time-of-flight
• non-line-of-sight imaging
• Radon transform
• phasor-based imaging
• inverse problems