Online Temporal Calibration of Camera and IMU using Nonlinear Optimization

In this paper, we aim to calibrate the time delay of timestamps of cameras and IMU measurements provided by Android smart phones or other low-cost devices whose camera and IMU are not temporally aligned. The time delay is estimated online in an iterative way through nonlinear optimization in sliding windows. We add new terms that are relative to time delay to the pre-integration results of IMU measurements instead of feature observations in order to improve the precision of temporal calibration. The experimental results indicate that our calibration result is closer to the real value compared with the state-of-the-art system and that our method appears to converge faster. By using our temporal calibration, the visual inertial odometry algorithm is less likely to suffer from fast turning or sudden stop.