EF-Calib: Spatiotemporal Calibration of Event- and Frame-Based Cameras Using Continuous-Time Trajectories

TL;DR

EF-Calib introduces a novel spatiotemporal calibration framework for event- and frame-based cameras using continuous-time trajectories, achieving high accuracy in intrinsic, extrinsic, and timing calibration for fused camera systems.

Contribution

The paper presents a new calibration pattern, an event recognition algorithm, and a derivable B-spline representation for continuous-time camera pose, enabling comprehensive calibration of event- and frame-based stereo systems.

Findings

Achieves state-of-the-art intrinsic parameter calibration accuracy.

Provides extrinsic calibration comparable to frame-based methods.

Accurately estimates time offset between cameras.

Abstract

Event camera, a bio-inspired asynchronous triggered camera, offers promising prospects for fusion with frame-based cameras owing to its low latency and high dynamic range. However, calibrating stereo vision systems that incorporate both event and frame-based cameras remains a significant challenge. In this letter, we present EF-Calib, a spatiotemporal calibration framework for event- and frame-based cameras using continuous-time trajectories. A novel calibration pattern applicable to both camera types and the corresponding event recognition algorithm is proposed. Leveraging the asynchronous nature of events, a derivable piece-wise B-spline to represent camera pose continuously is introduced, enabling calibration for intrinsic parameters, extrinsic parameters, and time offset, with analytical Jacobians provided. Various experiments are carried out to evaluate the calibration performance of EF-Calib, including calibration experiments for intrinsic parameters, extrinsic parameters, and time offset. Experimental results show that EF-Calib achieves the most accurate intrinsic parameters compared to current SOTA, the close accuracy of the extrinsic parameters compared to the frame-based results, and accurate time offset estimation. EF-Calib provides a convenient and accurate toolbox for calibrating the system that fuses events and frames. The code of this paper will also be open-sourced at: https://github.com/wsakobe/EF-Calib.